HARVARD UNIVERSITY J €1 r B, LIBRARY OF THE Museum of Comparative Zoology University of Kansas Publications museum of natural history VOLUME 13 • 1960-1962 EDITORS E. Raymond Hall, Chairman Henry S. Fitch Robert W. Wilson Museum of Natural History UNIVERSITY OF KANSAS LAWEENCE 1962 Museum of Natural History university of kansas lawrence LIBRARY FEB - 6 1963 PRINTED BY JEAN H. NEIBARGER. STATE PRINTER TOPEKA. KANSAS 19 62 29-3916 CONTENTS OF VOLUME 13 1. Five natural hybrid combinations in minnows ( Cyprinidae ) . By Frank B. Cross and W. L. Minckley. Pp. 1-18. June 1, 1960. 2. A distributional study of the amphibians of the Isthmus of Tehuantepec, Mexico. By William E. Duellman. Pp. 19-72, pis. 1-8, 3 figs. August 16, 1960. 3. A new subspecies of slider turtle (Pseudemys scripta) from Coahuila, Mexico. By John M. Legler. Pp. 73-84, pis. 9-12, 3 figs. August 16, 1960. 4. Autecology of the copperhead. By Henry S. Fitch. Pp. 85-288, pis. 13-20, 26 figs. November 30, 1960. 5. Occurrence of the garter snake, Thamnophis sirtalis, in the Great Plains and Rocky Mountains. By Henry S. Fitch and T. Paul MasUn. Pp. 289- 308, 4 figs. February 10, 1961. 6. Fishes of the Wakarusa River in Kansas. By James E. Deacon and Artie L. Metcalf. Pp. 309-322, 1 fig. February 10, 1961. 7. Geograpliic variation in the North American cyprinid fish, Hybopsis gracilis. By Leonard J. Olund and Frank B. Cross. Pp. 323-348, pis. 21-24, 2 figs. February 10, 1961. 8. Descriptions of two species of frogs, genus Ptychohyla — studies of Ameri- can hylid frogs, V. By WiUiam E. Duellman. Pp. 349-357, pi. 25, 2 figs. April 27, 1961. 9. Fish populations, following a drought, in the Neosho and Marais des Cygnes rivers of Kansas. By James Everett Deacon. Pp. 359-427, pis. 26-30, 3 figs. August 11, 1961. 10. North American Recent soft-shelled turtles (family Trionychidae ) . By Robert G. Webb. Pp. 429-611, pis. 31-54, 24 figs. February 16, 1962. Index. Pp. 613-624. 3otF?1960 University of Kansas PuBLiCAxiois HARVARD iiiuui wi«i->> Liii/Hi'. I Museum of Natural Histoby UNIVERSITY Volume 13, No. 1, pp. 1-18 June 1, 1960 Five Natural Hybrid Combinations in Minnows (Cyprinidae) BY FRANK B. CROSS AND W. L. MINCKLEY University of Kansas Lawrence -^ 1960 University of Kansas Publications, Museum of NATimAL History Editors: E. Raymond Hall, Chairman, Henry S. Fitch, Robert W. Wilson Volume 13, No. 1, pp. 1-18 PubUshed June 1, 1960 University of Kansas Lawrence, Kansas PRINTED IN THE STATE PRINTING PLANT TOPEKA, KANSAS 1960 28-3424 |MK. COMP. 7001 mm JUN2 91960, Five Natural Hybrid Combinations f;/lf!V;^;^0 in Minnows (Cyprinidae) [ ^^m^ BY FRANK B, CROSS AND W. L. MINCKLEY The hybrid fishes described herein are Chrosomus erythrogaster (Rafinesque) X Notropis cornutus frontalis (Agassiz), C. ery- throgaster X Semotilus atromaculatus ( Mitchill ) , Campostoma anomdlum plumheum ( Girard ) X S. atromaculatus, Gila nigrescens (Girard) X Rhinichthys cataractae (Valenciennes), and Notropis venustus venustus (Girard) X Notropis whipplei (Girard). Two of the combinations have been reported, without descriptions, in literature (citations below), and Hubbs (1955: Fig. 3) graphically indicated hybridization between the same genera with which this paper is concerned, but did not designate the species involved. All specimens of C. erythogaster X N. c. frontalis, C. erythro- gaster X S, atromaculatus, C. a. plumheum X S. atromaculatus, and N. v. venustus X N. whipplei were taken in a period of severe drought in Kansas and Arkansas. All were from small, spring-fed streams that support large populations of fishes. That the drought of 1953-1956 had pronounced efiFects on stream habitats in Kansas has been documented by Minckley and Cross (1959). Satisfactory sites for spawning may have been few, but an abun- dance of adult fishes persisted from earlier, wet years. Unusual crowding of spawning fishes would increase the opportunity for fertilization of the eggs of one species by sperm from another species. We think that the hybrids reported here (excepting G. nigrescens X R. cataractae ) are explainable on the basis of crowd- ing; we have no information about stream-conditions where tlie last-named hybrid was found. Generally, hybridization of fishes seems most common in areas that have been subject to radical climatic change in tlie past 20,000 or fewer years (Hubbs, 1955: 18-19), and in streams that have been altered recently by the activities of man (Hubbs and Strawn, 1956:342, and others). Streams from which we report hybrids probably were affected by overgrazing of their watersheds; overgrazing was unusually severe in the drought. Most of the hybrids were recognized as unusual at the time of capture, and were saved as part of numerically selective samples (3) 4 University of Kansas Publs., Mus. Nat. Hist. from the streams (rather than being discovered in the laboratory, in random samples). Our measurements were made by methods defined by Hubbs and Lagler (1958); values are expressed as thousandths of the larger dimension. Chrosomus erythrogaster X Notropis cornutus frontalis: KU 3872 (26.7 mm. in standard length) and KU 4170 (46.6 mm.) from Deep Creek, Riley Co., Kansas, Sec. 23, T. US, R. 7E, Dec. 14, 1957, and Apr. 26, 1958, respectively; and KU 4185 (39.3 mm.) from BluflF Creek, Pottawatomie Co., Kansas, Sec. 15, T. 6S, R. 8E, June 29, 1958. Compared in Table 1 with five specimens of C. erythrogaster, KU 3914 (39.3 to 47.3 mm., mean 43.0 mm.) from the same locality and of the same date as KU 3872 (above); and with five specimens of N. c. frontalis, KU 4184 (41.0 to 46.5 mm., mean 42.5 mm. ) from the same locality and of the same date as KU 4185 (above). This cross has previously been recorded by Trautman (1957:326, 355) and by Minckley (1959:431). The head-lengths of the hybrids are greater than in specimens of like size of C. erythrogaster or N. c. frontalis (Table 1). Hubbs and Miller (1943:373-374) reported that hybrids of Gila orcutti X Siphateles mohavensis have larger, more robust heads than either of the parental species, perhaps because of heterosis. The enlarged heads in hybrids of C. erythrogaster and N. c. frontalis result pri- marily from elongation of the postorbital region, with lesser elon- gation of the snout and orbit. The enlarged head affects measure- ments obtained for other structures that are parts of the head (and expressed as proportions of standard length or head-length), causing a tendency toward N. c. frontalis when the head-part is divided by standard length, and greater intermediacy or a tendency toward C. erythrogaster when the head-part is divided by head- length. In characters in which the parental species dijBFer most (size of eye, length of upper jaw, and width of gape), the hybrids are intermediate between the parental species, regardless of whether the measurements are expressed as proportions of head- length or standard length; however, tendencies toward one or the other of the parental species (dependent on the divisor) can also been seen in these characters. Some experimentally prop- agated hybrids show highly variable, and sometimes extreme characters, rather than intermediacy of meristic and proportional characters (Hubbs, 1956). Hybrid Combinations in Minnows Table 1. Comparisons of Three Specimens of Chrosomus erythrogaster X NoTROPis cornutus frontalis with Specimens of the Parental Species (means are above, ranges in parentheses below) Standard lengths. Head-length Standard length Orbital length Standard length Orbital length Head-length Snout-length Standard length Snout-length Head-length Interorbital width Standard length Interorbital width Head-length Gape-width Standard length Gape- width Head-length Upper jaw-length Standard length Upper jaw-length Head-length Postorbital length Standard length Postorbital length Head-length Chrosomus erythrogaster 43.0 (39.3-47.3) 253 (246-262) 067 (063-071) 263 (252-272) 069 (068-071) 272 (262-280) 069 (065-071) 272 (262-286) 056 (051-059) 222 (204-241) 057 (051-061) 223 (206-237) 113 (108-120) 444 (432-456) KU 4170 and 4185 43.0 (39.3-46.6) 282 (280-283) 075 (071-079) 266 (250-282) 073 (071-075) 260 (255-265) 074 (069-079) 263 (245-280) 065 (059-071) 230 (209-250) 082 (076-088) 292 (273-311) 130 (129-130) 460 (455-464) KU 3872 26.7 307 101 329 071 232 079 256 064 207 112 268 124 402 Notropis c. frontalis 42.5 (41.0-46]5) 276 (273-283) 083 (080-086) 300 (291-310) 068 (066-071) 245 (233-260) 068 (067-069) 245 (241-250) 065 (062-066) 233 (224-239) 083 (080-086) 301 (284-315) 123 (121-125) 446 (431-457) 6 University of Kansas Fuels., Mus. Nat. Hist. Table 1. Comparisons of Three Specimens of Chrosomus ery-^irogasteh X NoTROPis coRNirrus frontalis with Specimens of the Parental Species (means are above, ranges in parentheses below) — Concluded Chrosomus erythrogaster KU 4170 and 4185 KU 3872 Notropis c. frontalis Length of depressed dorsal fin 224 (217-232) 885 (869-892) 71.7 (68-76) 0,5-5,0 8 37-40 250 (247-252) 886 (871-900) 53.0 (53.0) 1,5-4,1 ((?)-4,l) 8 39 255 237 Standard length Length of depressed dorsal fin (233-243) 829 858 Head-length Number scales in lateral line (836-890) 52(?) 38.8 (38-39) Pharyngeal teeth Anal rays 1,5-4,2 8 2,4-4,2 usually 9 Vertebrae 38-39 In pigmentation, all three of the hybrids are intermediate be- tween the parental species. The mid-lateral band (which is dark and discrete in C. erythrogaster, but faint, broad, and diflFuse in N. c. frontalis) is broader and fainter in the hybrids than in Chroso- mus, but is better developed than in N. c. frontalis. The dorsolat- eral dark band of C. erythrogaster is present in the hybrids, but is less distinct than in that species, and less distinct than the mid- lateral band of the hybrids themselves. The dorsolateral band is not present in N. c. frontalis. The color of the peritoneum in the hybrids is the glossy, jet-black of C. erythrogaster in two speci- mens, and the dusky-black of N. c. frontalis in one. Chrosomus and Notropis differ greatly in the length and con- volution of the intestine. Chrosomus has a long, coiled gut, wliich is crossed by the mid-ventral line eight or nine times; in N. c. frontalis, the intestine forms a flat, S-shaped loop that does not cross the mid-ventral line. In the two largest hybrids (KU 4170 and 4185), the gut is intermediate, crossing the mid-ventral line four times. In the smaller hybrid (KU 3872) the gut crosses the mid-ventral line twice but the configuration of the anterior loops Hybrid Combinations in Minnows 7 indicates that the same intestinal convolutions that were found in the larger specimens would have developed in KU 3872 as the gut elongated with increase in size of the fish. Both Deep and BluflF creeks are clear, gravel-bottomed streams draining parts of the Flint Hills Area of Kansas. A description of Flint Hills streams and lists of fishes occurring in them have been published by Minckley (1956 and 1959), and by Minckley and Cross (1959). Chrosomus erythrogaster X Semotilus atromaculatus: KU 2947 (28.0 mm. in standard length) from Mill Creek, Wabaunsee Co., Kansas, Sec. 30, T. 12S, R. 9E, Mar. 22, 1953. Compared in Table 2 with five specimens of C. erythrogaster, KU 2836 (27.2 to 31.0 mm., mean 28.5) from the same locality and of the same date as KU 2947 (above); and with five specimens of S. atromaculatus, KU 1954, 2499, 2703, and 2838 (25.5 to 31.1 mm., mean 28.9 mm.) from streams in the same area. This hybrid is intermediate between the two species in number of scales and pharyngeal teeth, and has a composite of the pig- mentation found in the parental fishes (Table 2). For diagnostic purposes, greater importance is attached to the characters men- tioned above than to proportional measurements, which are sub- ject to considerable error because of the small size of the speci- mens. The few measurements that were taken indicate that this hybrid, like C. erythrogaster X ^- c. frontalis, has a larger head than do specimens of like size of either parental species. The en- larged head aflFects measurements obtained for other structures that are parts of the head; only the length of the upper jaw, which is greatly different in the parental species, is actually intermediate in KU 2947. Mill Creek is a clear stream, similar to Deep and Bluff creeks but somewhat larger. Mill Creek had an exceptionally large population of fishes at the time the hybrid was found, but Chroso- mus and Semotilus were neither unusually common nor rare. Two other crosses, both of which have been described in the literature, also have been found in Mill Creek. These are N. c. frontalis X S. atromaculatus, and N. c. frontalis X Notropis rubel- lus (Agassiz). Campostoma anomalum plumbeum X Semotilus atromaculatus: KU 4013 (three males, 86.0 to 96.0 mm. in standard length, mean 89.5 mm.) from Timber Creek, Scott Co., Kansas, Sec. 2, T. 16S, 8 University of Kansas Publs., Mus. Nat. Hist. Table 2. Comparison of One Specimen of Chrosomus erythrogaster X Semotilus atromaculatus with Specimens of the Parental Species (means are above, ranges in parentheses below) Dark lateral band .... Light dorsolateral band Dark dorsolateral band Color of peritoneum . . Length of gut Pharyngeal teeth Number scales in lateral hne Barbels Vertebrae Head-length Standard length Upper jaw-length Standard length Upper jaw-length Head-length Interorbital width Standard length Interorbital width Head-length Orbital length Standard length Orbital length Head-length Chrosomus erythrogaster intense well-defined intense black long with trans- verse coils 0,5-5,0 usually 70 or more, em- bedded absent 37-40 272 (266-277) 071 (069-074) 263 (254-273) 103 (101-106) 381 (372-400) 081 (075-085) 296 (271-313) KU 2947 intense poorly developed poorly developed black short, with a single forward loop 1,5-5,2 about 67 slightly em- bedded absent 39 310 097 310 114 372 083 267 Semotilus atromaculatus intense absent absent silvery short, with a single forward loop usually 2,5—4,2 usually fewer than 65, not embedded usually present 42-43 300 (292-308) 110 (104-114) 366 (356-382) 116 (114-118) 388 (380-400) 078 (076-084) 261 (255-273) Hybrid Combinations in Minnows 9 R. 33W, June 19, 1958. Compared in Table 3 with five specimens of C. a. plumbeum, KU 4034 (85.7 to 93.1 mm., mean 90.2 mm.) from the Smoky Hill River, Wallace Co., Kansas, Sec. 26, T. 13S, R. 39W, June 20, 1958; and with five specimens of S. atromaculatus, Table 3. Comparisons of Three Specimens of Campostoma anomalum PLUMBEUM X SeMOTILUS ATROMACtTLATUS WITH SPECIMENS OF THE PARENTAL Species (means are above, ranges in parentheses below) Standard lengths . Predorsal length Standard length Head-length Standard length Snout-length Standard length Orbital length Standard length Interorbital width Standard length Distance from tip of mandible to tip of maxillary Standard length Gill rakers (1st arch) Number scales in lateral line . Predorsal scale-rows. Anal rays . Vertebrae . Campostoma a. plumbeum 90.2 (85.7-93.1) 511 (505-517) 251 (244-258) 090 (086-096) 044 (043-045) 075 (073-078) 057 (053-063) 30 (29-31) 54 (53-55) 25 (23-27) 7 (6-7) 40 KU 4013 (three spec.) 89.5 (85.7-96.2) 533 (523-542) 276 (273-278) 088 (087-091) 048 (047-049) 094 (091-099) 076 (072-078) 17 (16-18) 54 (54-55) 27 (27-28) 7.3 (7-8) 42-44* Semotilus atromaculatus 91.7 (85.0-97!5) 557 (547-564) 289 (280-299) 085 (082-087) 049 (048-050) 110 (104-113) 098 (095-104) 9 (8-10) 56 (52-64) 35 (34-36) 8 8 42-43 * Three deformed vertebrae in one specimen with 44; other two specimens have 42 vertebrae. 10 University of Kansas Publs., Mus. Nat. Hist. KU 4012 and 4047 (85.0 to 97.5 mm., mean 91.7 mm.) from the same locality and of the same date as KU 4013 (above), and Sappa Creek, Decatur Co., Kansas, Sec. 29, T. 2S, R. 28W, June 23, 1958, respectively. This hybrid combination has previously been recorded by Johnson (1945). The hybrids seem uniformly intermediate between the parental species. Application of the hybrid index to the characters listed in Table 3 results in a value of 55.7 when C. a. plumbeum is as- signed the value 0. The pharyngeal arches of the hybrids are peculiarly deformed. Expressed in terms of the one- or two-rowed arrangement common to all North American cyprinids, tooth-counts of 0,5-4,1; l,3(?)-4,0; and 2,5-4,1 best fit the three fish. However, one arch bears only three teeth, all deformed and badly aligned, plus a pit that pre- sumably represents a lost fourth tooth. At the other extreme, one arch bears eight teeth, some of which are attached to the arch between and behind others that are countable as part of the basic main row. Supernumerary teeth and other deformities may have resulted from abnormalities in the replacement process. In some cases, replacement teeth probably failed to develop; in others, replacement teeth seemingly developed, but attached to the arch in abnormal positions, with or without loss of previous teeth, causing irregularity in alignment. Hubbs (1951) described an irregular (seemingly three-rowed) alignment in a fish that Hay (1888:249) reported from western Kansas as Squalius elon- gatus. However, Hubbs considered the specimen to be an aberrant example of S, atromaculatus, and the characteristics that he lists for it do not correspond closely with those of the hybrid speci- mens that we have. Evans and Deubler (1955:32) found three rows of teeth in two of 150 specimens of Semotilus, and attributed the abnormality to failure of old teeth to fall out after formation of new teeth. The teeth of Campostoma usually number 0,4-4,0, and those of Semofilus 2,5-4,2. The pharyngeal arches are much smaller in Campostoma than in Semotilus. The peritoneum is mottled dark and silvery in the hybrids; it has a composite of the coloration in the parental species rather than a blended shade. The intestine has two diagonal loops cross- ing the ventral part of the body cavity, and the hindgut lies high in the cavity, along the left side of the air bladder. In Campostoma, the long gut is transversely coiled around the air bladder, whereas in Semotilus the gut forms a longitudinal, flattened, S-shaped loop, ventral to the air bladder. Hybrid Combinations in Minnows 11 In the hybrids, the mouth is slightly oblique and nearly terminal. The lower lip is thick and fleshy, but has only a suggestion of the projecting mandibular shelf that is unique in Campostoma. The upper lip is uniform in width, not medially expanded as in S. atromaciilatiis. One of the hybrids lacks barbels, one has a Semotilus-\ike barbel on the right side only, and one has a vestigial barbel on the right side and an anomalous barbel that is nearly terminal on the left upper lip. In coloration, the hybrids lack the spot in the anterior base of the dorsal fin that is characteristic of Semotilus, but each has a poorly- developed dark lateral band, and a weak basicaudal spot. This band and spot are usually prominently developed in S. atromaculatus and usually are absent in adults of C. a. plumbeum. In the position and obHquity of the mouth, basic color pattern ( diflPuse lateral band and basicaudal spot ) , and the presence in one specimen of a nearly terminal, barbel-like structure, the hybrids somewhat resemble Hybopsis biguttata (Kirtland), which occurs rarely in the Kansas River Basin. These partial similarities are co- incidental, because otlier characters of the hybrids make relation- ship witli H. biguttata implausible. The high number of gill rakers (Table 3) and the length and position of the gut indicate strongly that the tliree specimens are hybrids with C. anomalum as one parent; the pharyngeal arches, though deformed, indicate that the other parental species has two rows of teeth, witli five teeth in the main row. Only S. atromaculatus, among species in the Kansas River Basin, usually has such a dental formula, and other characters of our three specimens fit expectations in a hybrid between that species and C. a. plumbeum. Timber Creek, where the three hybrids were collected, is a small, spring-fed, sandy-bottomed tributary to Scott County State Lake in the extreme southwestern part of the Kansas River Basin. The stream was less than 10 feet wide and six inches deep, except in three pools near road crossings. The hybrids were found in two of these pools, along with numerous S, atromaculatus and one adult C. a. plumbeum. Another specimen of C. a. plumbeum X S. atromaculatus (KU 4841, 39.3 mm. in standard length) was taken in the North Platte River at Lisco, Garden County, Nebraska, on September 11, 1959. That specimen has 7 anal rays and 52 scales in the lateral line; other- wise, it is similar to the three hybrids described above. Gila nigrescens X Bhinichthys cataractae: KU 4253 (a male. 12 University of Kansas Publs., Mus, Nat. Hist, 60.6 mm. in standard length), from New Mexico, Bernalillo County, Rio Grande 12 mi. S Bernalillo on U. S. Highway 85 (Corraleo Bridge). Compared in Table 4 with six specimens of G. nigrescens: KU 4251, 4254, and 4262 (63.1-72.4 mm. in standard length, mean 66.4 mm.); and with five specimens of R. cataractae: KU 4248, 4258, and 4264 (55.6-65.0 mm. standard length, mean 59.5 mm.). Comparative material was taken at the same locahty as KU 4253 and at nearby localities in the Rio Grande. The hybrid is intermediate in almost all of the features in which the parental species diflFer from each other. For six of the char- acters included in Table 4, the hybrid index is 49.7 per cent, when Gila is assigned the value 0 ( height of dorsal fin and numbers of fin rays and teeth excluded). There is no enlargement of the head in KU 4253, such as was found in Gila orcutti X Siphateles mohavensis (Hubbs and Miller, 1943:373), Chrosomus erythrogaster X ^o- tropis cornutits frontalis, and C. eryfhrogaster X Semotilus atro- maculatus. The height of the dorsal fin, which Hubbs and Miller (loc. cit.) found to be extreme in G. orcutti X S. mohavensis, ex- ceeds the average for the parental species in G. nigrescens X R- cataractae also; but, dorsal fins as high as that of the hybrid were found in some individuals of both parental species. In R. cataractae, all fins are more rounded and more expansive than in G. nigrescens, and fins other than the dorsal have an intermediate size in the hy- brid. This intermediacy has doubtful significance, because fin-size in Rhinichthys varies greatly with body-size, sex, and probably with the state of sexual development. Rhinichthys matures at smaller size than Gila, and never becomes so large as that species. Gila nigrescens and R. cataractae diflFer strikingly in features involving the snout and mouth, and these differences provide the most conclusive evidence that KU 4253 is a hybrid of these species. The projecting, fleshy snout of R. cataractae is bridged to the ven- tral mouth by a frenum that is approximately 3 mm. wide in speci- mens 60 mm. in standard length. In Gila, the snout does not project beyond the mouth, which is oblique, lacks a frenum, and is larger than in Rhinichthys. The snout of the hybrid projects less than in R. cataractae and is bridged to the upper lip by a frenum 1.7 mm. wide. The mouth of the hybrid is intermediate in size, obliquity, and thickness of the lips. Rhinichthys has barbels, Gila lacks them, and the hybrid has one vestigial barbel, on the right side. The lower surface of the head of Rhinichthys is broad and flattened, with pronounced rugosity on the gular area Hybrid Combinations in Minnows 13 and isthmus. In Gila the underside of the head is convex, with comparatively smooth membranes; the hybrid is intermediate, but tends toward Gila. Table 4. Comparisons of One Specimen of Gila nigrescens X Rhinich- THYS CATARACTAE WITH SPECIMENS OF THE PARENTAL SPECIES ( MEANS ARE ABOVE, RANGES IN PARENTHESES BELOW ) Standard lengths Head-length Standard length Orbital length Standard length Snout-length Standard length Dorsal fin-height Standard length Postorbital length Standard length Distance from tip of mandible to tip of maxillary Standard length Length of infralabial groove Standard length Upper jaw Number scales in lateral line . Anal fin-rays Pelvic fin-rays Pectoral fin-rays Pharyngeal teeth Gila nigrescens 66.4 (63.1-72.4) 282 (277-290) 063 (063-065) 083 (081-085) 225 (212-238) 140 (134-142) 081 (079-085) 060 (058-064) protractile 60 (58-63) 8 (7-8) 9 (9) 16 (16-18) 2,5-4,2 KU 4253 60.6 281 054 092 234 135 076 045 non-protractile 63 7 8 16-15 2,5-4,2 Rhinichthys cataradae 59 5 (55.6-65.0) 281 (273-293) 044 (041-047) 106 (099-113) 221 (206-234) 131 (127-136) 066 (064-069) 036 (034-038) non-protractile 65 (63-67) 7 (7) 8 (8-9) 13 (13-14) 2,4-4,2 14 University of Kansas Publs., Mus. Nat, Hist. Table 5. Comparisons of One Specimen of Notropis v. venustus X No- TROPIS WHIPPLEI with SPECIMENS OF THE PARENTAL SpECIES, AND WITH N. LU- TRENSIS X N. V. VENUSTUS. MEASUREMENTS ( LENGTHS AND DEPTHS ) ArE Expressed as Thousandths of Standard Length (means above, ranges m parentheses below) Notropis whipplei KU 3516 Notropis venustus, KU 3510 Notropis venustus from Gibbs (1957a) Notropis lutrensis XN. venustus Standard length. . Predorsal length. . Dorsal origin to caudal base , . . Prepelvic length . . Head-length Caudal peduncle- length Caudal peduncle- depth Head-depth Snout-length Eye-diameter. . . . Postorbital length, head Upper jaw, length , Body depth Lateral-line scales. Scales above lateral-line. 50.6 (45.0-54.0) 525 (513-535) 497 (493-502) 505 (498-518) 257 (250-262) 217 (211-220) 110 (106-116) 170 (167-173) 079 (076-083) 069 (063-078) 112 (108-115) 078 (076-081) 239 (233-248) 36-37 13 47.8 523 508 492 255 221 119 182 079 069 115 077 253 36 14 47.3 (44.5-49.6) 534 (519-547) 497 (478-504) 505 (500-510) 261 (256-267) 224 (213-230) 127 (124-133) 186 (182-190) 080 (072-083) 070 (066-072) 116 (112-120) 081 (076-082) 278 (261-288) 36-38 15 523 496 260 125 073^ 079 274 44.7 (43.3-47.3) 532 (628-538) 508 (502-514) 499 (486-517) 263 (261-267) 224 (214-231) 126 (122-131) 190 (189-192) 081 (078-082) 070 (068-074) 117 (115-120) 077 (076-081) 282 (275-294) 36.5 (34-39) 15 (13-16) Hybrid Combinations in Minnows 15 Table 5. Compamsons of One Specimen of Notropis v. venustus X No- tropis WHIPPLEI with Specimens of the Parental Species, and with N. lu- trensis X N. V. venustus. Measurements (lengths and depths) Are Expressed as Thousandths of Standard Length (means above, ranges in parentheses below) — Concluded Notropis whipplei KU 3516 Notropis venu^tv^, KU 3510 Notropis venustus from Gibbs (1957a) Notropis lutrensis X N. venustus Anal fin-rays 9 14 (14-15) Absent 37-38 9 14-14 8 15 (14-16) Present 37 8 (7-8) 14.2 (12-17) Present Pectoral fin-rays .... Caudal spot Vertebrae Present 38 Present * Orbital diameter. The air bladder of KU 4253 is nearly as large as in Gila, and much larger than the degenerate air bladder of R. cataractae. Although the hybrid appears to be male, the gonads (especially the right one) are poorly developed. The hybrid is intermediate in curva- ture of the lateral line, which is nearly straight in Rhinichthys and strongly decurved in Gila. Specimen No. 4253 is mostly pallid, resembling Gila much more than Rhinichthys in pigmentation. A mid-dorsal dark streak is conspicuous in the hybrid, especially anteriorly, but is less intense than in Gila. Rhinichthys lacks a well-developed dorsal stripe. The preorbital and suborbital areas are more heavily pigmented in the hybrid than in Gila, but not nearly so dark as in Rhinichthys. The hybrid has a faint dark basicaudal spot that is variably de- veloped in Rhinichthys but absent in Gila. Notropis venustus venustus X Notropis whipplei: KU 3516 (a male, 47.8 mm. in standard length), from Arkansas, Sevier Co., Winters Creek where it is crossed by U. S. Highway 71, 5 mi. N of Little River Bridge, March 8, 1956. Compared in Table 5 with four specimens of IV. whipplei, KU 3517 (45.0-52.6 mm. in standard length, mean 50.6 mm.), same locality and date as KU 3516; four specimens of N. v. venustus, KU 3510 (44.5-49.6 mm. in standard length, mean 47.3 mm.), Louisiana, Winn Parish, Little Naches Bayou on U. S. Highway 71, 8.8 mi. NW Montgom- ery, March 4, 1956; three specimens of Notropis lutrensis (Baird and Girard) X N. v. venustus, KU 3510 (43.3-47.3 mm. in stand- 16 University of Kansas Publs., Mus. Nat. Hist. ard length, mean 44.7 mm. ) , same locality and date as N. v. venus- tus above; and with tabulated data on N. v. venustus from Gibbs (1957a: 185-186). All specimens are from the lower Red River Drainage; other series of N. whipplei, N. venustus, and N. lutrensis X N. venustus, from the Red River Drainage and elsewhere, were examined but are not tabulated because of differences in size, and because of geographic variability that has been discussed by Gibbs (1957a). The Subgenus Cyprinella of Notropis, to which N. venustus and N. whipplei belong, has been studied intensively by Gibbs (1957a and b). Notropis venustus differs conspicuously from N. whipplei in having a large dark basicaudal spot; also, N. venustus usually has 8 (rather than 9) anal rays, and 15 (rather than 13) scales above the lateral line immediately anterior to the dorsal fin. Speci- mens of N. V. venustus from the Red River Drainage, where the most robust representatives of the species are found, differ from N. whipplei in depth of head, body, and caudal peduncle (Table 5). KU 3516 has a composite of the 9-rayed anal fin of N. whipplei and the caudal spot ( albeit diffuse ) of N. venustus; and, the hybrid is intermediate in body-proportions that distinguish the two species, especially depth of head, body, and caudal peduncle. In other features KU 3516 has values within the overlapping ranges of variation of whipplei and venustus except that the ratio of postdorsal length to standard length is extremely long in the hybrid, and the ratio of prepelvic length to standard length is extremely short (Table 5). Both extreme values for the hybrid seem to result from the cumulative influence of characters in which the parental species differ slightly in mean value ( especially head-length, in which the hybrid is like whipplei, and caudal peduncle-length, in which the hybrid approaches venustus, despite the 9-rayed anal fin of the hybrid). The basicaudal spot of the hybrid is like that of N. v. venustus except for being less intense. Notropis venustus hybridizes extensively with N. lutrensis ( Hubbs, Kuehne, and Ball, 1953:226-230; Hubbs and Strawn, 1956), and that combination occurs in streams near the locality where KU 3516 was taken. KU 3516 resembles N, lutrensis X N. v. venustus in many ways, but is more slender than the latter hybrid. The depth of head, body, and caudal peduncle are greater in N. lutrensis than in N. venustus (much greater than in N. whipplei); therefore, speci- Hybrid Combinations in Minnows 17 mens of N. lutrensis X ^- venustus are usually deeper than N. venustus, whereas KU 3516 is less deep. KU 3516 has a rather sharp snout and thin, straight lips that are strongly suggestive of N. whipplei, rather than N. lutrensis, in which the snout is rounded and the Hps are more obliquely decurved. There is less pigment underlying the anterior lateral-Hne scales in KU 3516 than in N. lutrensis X ^- venustus, and melanophores on the scale-pockets of KU 3516 are arranged in narrower, more distinct submarginal bars than in N. lutrensis X ^- venustus. Because of the di£Ference in pigmentation, the lateral scales of N. whipplei (and of KU 3516) appear more narrowly diamond-shaped than the lateral scales of N. lutrensis or N. lutrensis X N- venustus. The lengths and heights of the scales are approximately the same in all three species. Winters Creek, where KU 3516 was taken, flowed approximately five cubic feet per second at the time our collection was made; a landowner on the stream stated that it had been dry, except for pools, in the previous two summers. The water was somewhat gray, but nearly clear. The habitat consisted mainly of short riffles, with average depth of four inches, and pools to depths of two feet. Twelve species of fish, including N. whipplei but not N. lutrensis or N. venustus, were found; other minnows were Semotilus atro- maculatus, N. chalybaeus, N. cornutus, N. umbratilis, and Campo- stoma anomalum. LITERATURE CITED Evans, H. E., and Deubler, Jr., E. E. 1955. Pharyngeal tooth replacement in Semotilus atromaculatus and Clinostomus elongatus, two species of cyprinid fishes. Copeia, 1955 (1):31-41, February 18. GiBBs, Jr., R. H. 1957a. Cyprinid fishes of the Subgenus Cyprinella of Notropis. III. Vari- ation and subspecies of Notropis venustus (Girard). Tulane Studies in Zoology, 5(8):175-203, August 7. 1957b. Cyprinid fishes of the Subgenus Cyprinella of Notropis. I. Sys- tematic status of the Subgenus Cyprinella, with a key to the species exclusive of the lutrensis-omatus complex. Copeia, 1957(3) :185- 195, August 26. Hay, O. p. 1888. A contribution to the knowledge of the fishes of Kansas. Proc. U. S. Nat. Mus., 10:242-253, March 1. HUBBS, C. L. 1951. Identification of cyprinid fish reported from Kansas as Squalius elongatus. Trans. Kansas Acad. Sci., 54(2): 190-192, June 15. 18 University of Kansas Publs., Mus. Nat. Hist. 1955. Hybridization between fish species in nature. Systematic Zoology, 4(l):l-20, March. HuBBS, C. L., and Lagler, K. F. 1958. Fishes of the Great Lakes Region. Cranbrook Inst. Sci., Bull. 26, revised ed., xiii + 213 pp. HuBBS, C. L., and Miller, R. R. 1943. Mass hybridization between two genera of cyprinid fishes in the Mohave Desert, CaUfomia. Papers Michigan Acad. Sci., Arts, and Lett., 28 ( 1942) : 343-378, pis. 1-4, February. HUBBS, C. 1956. Relative variability of hybrids between the minnows, Notropis lepidus and N. proserpinus. Texas Jour. Sci., 8 (4):463-469, De- cember. HuBBS, C, KuEHNE, R. A., and Ball, J. C. 1953. The fishes of the upper Guadalupe River, Texas. Texas Jour. Sci., 5(2):216-244, June. HuBBS, C., and Strawn, K. 1956. Interfertihty between two sympatric fishes, Notropis lutrensis and Notropis vcnustus. Evolution, 10(4):341-344, December. Johnson, R. 1945. Ever hook a hybrid? Minnesota Conservation Volunteer, 8(49): 18-22. MiNCKLEY, W. L. 1956. A fish survey of the Pillsbury Crossing Area, Deep Creek, Riley County, Kansas. Trans. Kansas Acad. Sci., 59(3) :351-357, Octo- ber 31. 1959. Fishes of the Big Blue River Basin, Kansas. Univ. Kans. Publ., Mus. Nat. Hist., ll(7):401-442. May 8. MiNCKLEY, W. L., and Cross, F. B. 1959. Distribution, habitat, and abimdance of the Topeka shiner, Notropis topeka (Gilbert) in Kansas. Amer. Midl.-Nat., 61( 1) :210-217. Trautman, M. B. 1957. The fishes of Ohio. Ohio State Univ. Press, xviii -1- 683 pp. Transmitted March 2, 1960. D 28-3424 University of Kansas Publications Museum of Natural History I Volume 13, No. 2, pp. 19-72, pis. 1-8, 3 figs. August 16, 1960 COMKZOBi 7iqB0 ^rtKyakS iiiiilES' A Distributional Study of the Amphibians of the Isthmus of Tehuantepec, Mexico BY WILLIAM E. DUELLMAN University of Kansas Lawrence 1960 UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATURAL HISTORY Institutional libraries interested in publications exchange may obtain this series by addressing the Exchange Librarian, University of Kansas Library, Lawrence, Kansas. Copies for individuals, persons working in a particular field of study, may be obtained by addressing instead the Museum of Natural History, University of Kansas, Lawrence, Kansas. There is no provision for sale of this series by the University Library, which meets institutional requests, or by the Museum of Natural History, which meets the requests of individuals. However, when individuals request copies from the Museum, 25 cents should be included, for each separate number that is 100 pages or more in length, for the purpose of defraying the costs of wrapping and mailing. * An asterisk designates those numbers of which the Museum's supply (not the Library's supply) is exhausted. Numbers published to date, in this series, are as follows: Vol. 1. Nos. 1-26 and index. Pp. 1-638, 1946-1950. *Vol. 2. (Complete) Mammals of Washington. By Walter W. Dalquest. Pp. 1-444, 140 figures in text. April 9, 1948. Vol. 3. *1. The avifatma of Micronesia, its origin, evolution, and distribution. By Rol- lin H. Baker. Pp. 1-359, 16 figures in text. June 12, 1951. *2. A quantitative studv of the nocturnal migration of birds. By George H. Lowery, Jr. Pp. 361-472, 47 figures in text. June 29, 1951. 3. Phvlogenv of the waxwings and allied birds. By M. Dale Arvey. Pp. 473- 530, 49 figures in text, 13 tables. October 10, 1951. 4. Birds from the state of Veracruz, Mexico. By George H. Lowery, Jr., and Walter W. Dalquest. Pp. 531-649, 7 figures in text, 2 tables. October 10, 1951. Index. Pp. 651-681. *Vol. 4. (Complete) American weasels. By E. Raymond Hall. Pp. 1-466, 41 plates, 31 figures in text. December 27, 1951. Vol. 5. Nos. 1-37 and index. Pp. 1-676, 1951-1953. *Vol. 6. (Complete) Mammals of Utah, taxonomy and distribution. By Stephen D. Durrant. Pp. 1-549, 91 figures in text, 30 tables. August 10, 1952. Vol. 7. *1. Mammals of Kansas. By E. Lendell Cocknmi. Pp. 1-303, 73 figures in text, 37 tables. August 25, 1952. 2. Ecology of the opossum on a natural area in northeastern Kansas. By Henry S. Fitch and Lewis L. Sandidge. Pp. 305-338, 5 figures in text. August 24, 1953. 3. The silkv pocket mice (Perognathus flavus) of Mexico. By Rollin H. Baker. Pp. 339-347, 1 figure in text. February 15, 1954. 4. North American jumping mice (Genus Zapus). Bv Philip H. Krutzsch. Pp. 349-472, 47 figures in text, 4 tables. April 21, 1954. 5. Mammals from Southeastern Alaska. By Rollin H. Baker and James S. Findley. Pp. 473-477. April 21, 1954. 6. Distribution of Some Nebraskan Mammals. By J. Knox Jones, Jr. Pp. 479- 487. April 21, 1954. 7. Subspeciation in the montane meadow mouse. Microtus montanus, in Wyo- ming and Colorado. By Sydney Anderson. Pp. 489-506, 2 figures in text. July 23, 1954. 8. A new subspecies of bat (Myotis velifer) from southeastern California and Arizona. By Terry A. Vaughan. Pp. 507-512. July 23, 1954. 9. Mammals of the San Gabriel mountains of California. By Terry A. Vaughan. Pp. 513-582, 1 figure in text, 12 tables. November 15, 1954. 10. A new bat (Genns Pipistrellus) from northeastern Mexico. By Rollin H. Baker. Pp. 583-586. November 15, 1954. 11. A new subspecies of pocket mouse from Kansas. By E. Raymond Hall. Pp. 587-590. November 15, 1954. 12. Geographic variation in the pocket gopher, Cratogeomys castanops, in Coa- huila. Mexico. By Robert J. RusseU and RoUin H. Baker. Pp. 591-608. March 15, 1955. 13. A new cottontail ( Svlvilagus floridanus ) from northeastern Mexico. By Rollin H. Baker. Pp. 609-612. April 8, 1955. 14. Taxonomv and distribution of some American shrews. By James S. Findley. Pp. 613-618. June 10, 1955. 15. The pigmy woodrat, Neotoma goldmani, its distribution and systematic posi- tion. By Dennis G. Rainey and Rollin H. Baker. Pp. 619-624, 2 figures in text. June 10, 1955. Index. Pp. 625-651. (Continued on inside of back cover) University of Kansas Publications Museum of Natural History Volume 13, No. 2, pp. 19-72, pis. 1-8, 3 figs. August 16, 1960 A Distributional Study of the Amphibians of the Isthmus of Tehuantepec, Mexico BY WILLIAM E. DUELLMAN University of Kansas Lawrence 1960 Ui«VERSiTY OF Kansas PxraLiCATioNS, Museum of Natural History Editors: E. Raymond Hall, Chairman, Henry S. Fitch, Robert W. Wilson Volume 13, No. 2, pp. 19-72, pis. 1-8, 3 figs. Published August 16, 1960 MUS. COMP. ZOOl UBRArtV OCT -7 1960 HARVARD UNIVERSITY University of Kansas Lawrence, Kansas PRINTED IN THE STATE PRINTING PLANT TOPEKA. KANSAS I960 28-3859 A Distributional Study of the Amphibians of the Isthmus of Tehuantepec, Mexico BY WILLIAM E, DUELLMAN CONTENTS PAGE Intboduction 21 Acknowledgments 23 Field Studies in the Isthmus of Tehuantepec 23 Sources of Material 24 Description of the Isthmus of Tehuantepec 25 Physiography 25 Climate 28 Vegetation 29 The Sierra de los Tuxtlas - 32 Gazetteer 33 The Amphibian Fauna of the Lowlands 37 Composition of the Favma 37 Ecology of the Fauna 38 Distribution of the Fauna 42 The Amphibian Fauna of the Foothills and Adjacent Highlands .... 44 Establishment of Present Patterns of Distribution 45 Accounts of Species 49 Summary 68 Literatture Cited 69 INTRODUCTION Few regions in Middle America are so important zoogeographi- cally as is the Isthmus of Tehuantepec, that neck of land connecting North America with Central America, separating the Pacific Ocean from the Gulf of Mexico by a distance of only about 220 kilometers (airline), and forming a low break between the highlands of Mexico and those of Central America. Before World War II the isthmus could be reached readily only by railroad or by ocean vessel to Salina Cruz or Coatzacoalcos. With the advent of roads, principally the Trans-isthmian Highway, vast areas of the interior of the isthmus became accessible to biologists. Nevertheless, long before roads were built in the isthmian region collectors and biologists visited it, especially the town of Tehuantepec, from which collections date back to the 1870's. Therefore, it is rather sur- (21) 22 University of Kansas Publs., Mus. Nat. Hist. prising that no attempt has been made to present a faunal hst of the amphibians or reptiles of the isthmus. Ruthven (1912) summarized his collections from the vicinity of Cuatotolapam, Veracruz, and Hartw^eg and Oliver ( 1940 ) presented an annotated list of the species collected by them in the vicinity of Tehuantepec. In recent years there have been only a few papers reporting species from the isthmus ( Fugler and Webb, 1957; Langebartel and Smith, 1959). The zoogeographic significance of the Isthmus of Tehuan- tepec is exemplified by the works of Burt (1931), Duellman (1958), Gloyd (1940), Oliver (1948), and Stuart (1941), who in their discussions of evolution and dispersal of various genera of reptiles, pointed out that the Isthmus of Tehuantepec was a region of zoo- geographic importance. Originally I intended to study the entire herpetofauna of the isthmus. But I have not had opportunity to study all of the reptiles, and I have not had the inclination to solve certain taxonomic problems concerning them. The amphibians that I collected, to- gether with all other known specimens in museums, have been studied. Therefore, the present report is concerned only with the amphibians. Only the amphibians of the lowlands of the isthmus have been sampled adequately. Although I have commented on the highland species in the discussion of distribution, they are not included in the systematic section, which deals solely with the 36 species definitely known to occur in the lowlands of the isthmus. Among the species of amphibians that I would expect to occur in the isthm.us, the only one not yet found there is Hyla phaeota. Sufiicient specimens of most of the species are available to show their variation in the isthmus. Consequently, the systematics of these amphibians is on a fairly substantial basis. Probably cer- tain species in the istlimian region will be found to be conspecific with others to the south, for example Hijla ebraccata with Hyla leucophyllata and Hyla rohertmertensi with Hyla underwoodi. Nevertheless, such taxonomic changes will not affect the distribu- tional picture presented here. Our greatest lack of knowledge concerning the amphibians is about their life histories, as may be illustrated by the following questions, all of which now are without definite answers. Where do many of the small frogs conceal themselves during the dry season? What amount of, if any, inter- specific competition exists among several species of tree frogs, all of which breed in the same ponds? What factors in the environ- ment permit certain amphibians, but not others, to live in the Amphibians of Isthmus of Tehuantepec 23 humid rainforests, as well as in the arid tropical scrub forest? The answers to these questions and many others must await addi- tional field studies. The purpose of this paper is to make known the species of amphibians living in the Isthmus of Tehuantepec, to describe the environments in which they live, and to discuss their distribution in the isthmus. With respect to the distribution of animals in the Isthmus of Tehuantepec I will attempt to explain the present patterns of distribution with special reference to climatic fluctua- tion in the Pleistocene. Acknowledgments My extensive field work in the Isthmus of Tehuantepec was made possible by grants from the Penrose Fund of the American Philosopliical Society ( 1956 ) and the Bache Fvmd of the National Academy of Sciences ( 1958 ) . Further- more, my field work received the hearty support of the Musemn of Zoology at the University of Michigan; for their cooperation I am indebted to Norman Hartweg, T. H. Hubbell, and Henry van der Schalie. In the course of my studies I received helpful suggestions from Norman Hartweg, L. C. Stuart, and Charles F. Walker, to whom I am grateful. For permission to examine specimens in their care I thank Doris M. Cocliran, Hobart M. Smith, and Richard G. Zweifel. I am deeply indebted to Thomas MacDougall for many suggestions and for aid in preparing the gazetteer. I am most grateful for the efForts of my field companions, Richard E. Etheridge, Jerome B. Tulecke, John Wellman, and especially my wife, Ann S. Duellman, who spent many long days and nights gathering much of the data on which this report is based. Our work in the isthmus was furthered by the generous help and hospitality of many residents, especially the late Wilbur Barker of Tehuantepec, Fortunado Delgado of Rancho Las Hojitas near Acayucan, Cesar Farjas of Donaji, and Juan Mayo! of San Andres Tuxtla. Profesor Jordi Julia Z. of the Laboratorio de Ento- mologia, Comision del Papaloapan, Ciudad Aleman, Veracruz, helped make possible my field work in 1959; for this he has my sincere thanks. In con- clusion I express my gratitude to Ing. Juan Lozano Franco, Secretaria de Agricultura y Ganaderia, for providing me witli the necessary permits. Field Studies in the Isthmus of Tehuantepec 1 first visited the Istlimus of Tehuantepec and collected on the Pacific low- lands of the isthmus in July, 1955. At that time heavy rains and impassable roads restricted travelling. In February and March of 1956 my wife and I concentrated our efforts in the central region between the Rio Jaltepec and Matias Romero, but also made several trips across the istlimus to gather eco- logical data in the dry season. In July of the same year, accompanied by Richard E. Etheridge, we again crossed the isthmus several times in order to gather ecological data in the wet season, and studied especially hylid frogs, most of which had not been seen in the dry season. Accompanied by Jerome B. Tulecke and John Wellman, I collected again in the isthmus in July, 1958, between Salina Cruz and Tehuantepec, and between Coatzacoalcos and Coso- 24 University of Kansas Publs., Mus. Nat. Hist. leacaque. In March and April, 1959, I collected at Ciudad Aleman. Nearly 1200 specimens of 30 species of amphibians were thus collected in the Isthmus of Tehuantepec; all specimens are now in the Museum of Z)oology at the Uni- versity of Michigan. Of other species known from the isthmus, I have had field experience with all but one (Bolitoglossa veracrucis) in other parts of Mexico. Sources of Material There are in museiun collections nearly 3000 specimens of amphibians with reliable data from the Isthmus of Tehuantepec. Among the first herpetological specimens collected in the isthmian region are those assembled by Francis Sumichrast in the 1870's from the vicinity of Santa Efigenia and Tapanatepec, Oaxaca. These specimens were sent to the United States National Museum and the Museum National d'Histoire Naturelle in Paris; many served as the types of new species: Bufo canaliferus Cope, Eleutherodactylus rugulosus Cope, Syr- rhophus lepras Cope, and Hylella sumichrasti Brocchi. In 1911 Alexander G. Ruthven collected in the savanna country near Cuatotolapam, Veracruz; the report on his collections (1912) is the first dealing with the herpetofauna of a part of the isthmus. His specimens are in the collection of the University of Michigan Museum of Zoology. Norman Hartweg and James A. Oliver collected for the University of Michigan Museum of Zoology in the vicinity of Tehuan- tepec, Oaxaca, during the summer of 1936. The results of their work were published as an annotated list of species occurring on the Pacific slopes of the isthmus (1940). Hobart M. Smith collected in the vicinity' of Tehuantepec in January, 1940; his specimens are in the United States National Museum. Speci- mens collected by Smith served as the types of Eleutherodactylus avocalis Taylor and Smith and Diaglena reticulata Taylor. Walter W. Dalquest col- lected vertebrates for the University of Kansas in southern Veracruz in the winters of 1947 and 1948; he spent about six months on the Gulf lowlands of the isthmus, principally in the vicinity of Jesus Carranza. For the past two decades Tliomas MacDougall, a resident of New York City, has spent his winters collecting biological specimens in southern Mexico. He makes his headquarters at Tehuantepec, but his compulsion to see the "back country" has taken him to many remote parts of southern Oaxaca. His earlier collections are in the American Museum of Natural History; the later ones are in the University of Ilfinois Museum of Natural History. Minor collections include those made by Matthew W. Stirling at San Lorenzo, Veracruz, February- April, 1946 (United States National Museum), by Fred G. Thompson on a trip across the isthmus in December, 1955 (University of Michigan Museum of Zoology), by the University of Kansas Museum of Natural History field party under the direction of Rolhn H. Baker at Tolosita, Oaxaca, and by David A. Langebartel and associates from southern Oaxaca in June, 1958 ( University of Illinois Museum of Natural History ) . In the collections of the United States National Museum are several species of amphibians sent to the museum from Tehuantepec by Francis Sumichrast. These include Bolitoglossa platydactyla (USNM 30305, 30344-6, 30528), Bolitoglossa rufescens (10042), Chiropterotriton chiropterus (30347), Linea- triton lineola (30353), Parvimolge townsendi (30352), Pseudoeurycea cepha- lica (30350), Thorius pennatulus (30348-9), Hyla miotympanum (30302-3), Amphibians of Isthmus of Tehuantepec 25 and Hyla picta (30304). Because of the poor condition of the specimens, determinations of those listed as Bolitoglossa rufescens and Pseudoeurycea cephalica are uncertain. With the exception of the Bolitoglossa rufescens, which is stated to have come from Santa Efigenia, all of these specimens are catalogued as having come from Tehuantepec. None of these species has since been recorded from the Pacific slopes of the isthmus; however, they all occur in the vicinity of Orizaba, Veracruz. Probably Sumichrast carried the specimens with him from Orizaba, his home before moving to Santa Efigenia, and shipped them from Tehuantepec to the United States National Museum. These species definitely should not be considered as inhabitants of the Pacific slopes of the Isthmus of Tehuantepec. DESCRIPTION OF THE ISTHMUS OF TEHUANTEPEC The Isthmus of Tehuantepec is a strip of land forming a low pass, which separates the mountain masses of Mexico proper from those of Central America, and at the same time provides a continuum of lowlands from the Gulf of Mexico to the Pacific Ocean. This topography combines with the climatic conditions to create ex- tremely diverse environments, the distribution of which can be adequately understood only after an acquaintance with the to- pography and climate of the region. Physiography In east-central Oaxaca the mountain masses comprising the Sierra Madre Oriental and the Sierra del Sur terminate in a series of ranges — Sierra de Juarez, Sierra de los Mijes, and Sierra de Choa- pam. From lofty peaks, such as Cerro de Zempoaltepetl (3400 meters), the highlands diminish eastward to succeedingly lower ridges, until in the middle of the Isthmus of Tehuantepec the con- tinental divide is about 250 meters above sea level. Eastward from this low divide the land rises to form the Sierra Madre de Chiapas, which is continuous with the highland masses of Guate- mala. For the purposes of this description, the lowlands of the isthmus may be divided into three parts — the Gulf Coastal Plain, the cen- tral ridges, and the Pacific Coastal Plain, which in the isthmus is called the Plains of Tehuantepec (Figs. 1 and 2). The Gulf Coastal Plain is broad and fairly level near the coast, but rolling in the interior. The plain, throughout most of its length in the isthmus, is at least 75 kilometers wide. The majority of the region in the isthmus is drained by the Rio Coatzacoalcos, which flows in a northerly course to the Gulf of Mexico. The western part is drained by the Rio San Juan, the principal tributary of the Rio Papaloapan. Behind the coastal dunes are frequent, and some- 96° 95° I9»- 94° — r- 10 0 10 20 30 40 Scole of Kilometers 0 Fig. 1. Map of the Isthmus of Tehuantepec based on the American Geo- graphical Society's "Map of Hispanic America on the Scale of 1:1,000,000." The localities shown are numbered in the gazetteer; the numerical sequence of localities is an arrangement whereby north takes precedence over south and west over east. 1. Alvarado. 2. Lerdo de Tejada. 3. Tlacotalpan. 4. Tula. 5. Tecolapan. 6. Amatitlan. 7. Cosa- maloapan. 8. Chacaltianguis. 9. Novillero. 10. Ciudad Aleman. 11. Papaloapan. 12. Tu.\- tepec. 13. Cuatotolapam. 14. Hueyapan. 15. Berta. 16. Coatzacoaicos. 17. Ayentes. 18. Rio de las Playas. 19. Cosaleacaque. 20. Minatitlan. 21. Acayucan. 22. Aquilera. 23. San Lorenzo. 24. Naranja. 25. Suchil. 26. Jesus Carranza. 27. La Oaxaqueiia. 28. Ubero. 29. Donaji. 30. Tolosita. 31. El Modelo. 32. Sarabia. 33. Guichicovi. 34. La Princesa. 35. Santa Maria Chimalapa. 36. Matias Romero. 37. Santo Domingo Petapa. 38. El Barrio. 39. Pahnar. 40. Chivela. 41. Santiago Chivela. 42. Nizanda. 43. Agua Caliente. 44. Portillo Los Nanches. 45. Ixtepec. 46. La Ventosa. 47. Zanatepec. 48. Union Hidalgo. 49. Tres Cruces. 50. Juchitan. 51. Escurano. 52. Salazar. 53. Santa Efigenia. 54. Tequisistlan. 55. Cerro de Quiengola. 56. San Pablo. 57. Mixtequilla. 58. Tapanatepec. 59. Zarzamora. 60. Lim6n. 61. Tehuantepec. 62. BisUana. 63. Santa Lucia. 64. Cerro de Arenal. 65. Cerro de San Pedro. 66. La Concepcion. 67. Tenango. 68. San Antonio. 69. Huilotepec. 70. Salina Cruz. Amphibians of Isthmus of Tehuantepec 27 DS01U9A 0-]- eiinbse/.j ^ D|9Aiq3 oSdijuds ojsoioy sDiiO^Aj DiqoiDS DiqoJDS cjy dzudj;do snsup DfUDJDN D-ieiinbv UDj'i/.DOV H LJ :<; O ^ < < Ll- o S 0") o C3 S < E in 5 § < z t) cc en 0. a. O 8dH 0| Sr- sr.bDODr;Dsoo- upi;iiouiA|- S0D|DO0DZjrj03- c- O— i c at a sja;3|/j o o o o o t« c oj tn l-c a; H a 0) -^ lO ID tCrH C n >% ci (U 03 O h •i-* X 03 2 O 03 t-. •9, a o -M r) \^ to m c bO b/) :s 05 n X -C 01 M •— H C3 c •4^ 1-4 a a o t-M 03 o Q) C/5 60 T dj > (—• •4-1 O 1/1 >-^ VI a; IV a ■*-' -4—* o o (U rrt a; ^ o a o ^ a rt Vh M O ft o H oi d M |JH 28 University of Kansas Publs., Mus. Nat. Hist. times large, lagoons. Immediately inland from Coatzacoalcos and along the lower stretches of the Rio Papaloapan are extensive marshes. Essentially the entire coastal plain, with the exception of the coastal dunes, consists of rich alluvial deposits. The central ridges extend from the Rio Jaltepec southward to within 40 kilometers of the Pacific coast. It is in this area that the continuity of the high ridges and volcanic peaks, which extend nearly the entire length of the Americas, is interrupted at a point almost directly in line with the shortest distance between the two oceans. The northern part of this central region consists of hills dissected by tributaries of the Rio Coatzacoalcos; the principal ones from north to south are — Rio Jaltepec, Rio Tortuguero, Rio Sarabia, and Rio Malatengo. The plains of Chivela are south of these rivers and lie at an elevation of about 200 meters; at the southern edge of these plains a range of hills rises to 250 to 400 meters above sea level. These hills drop abruptly to the Plains of Tehuan- tepec. In the northern and central parts of this central region the rocks are granitic; the hills to the south of the Plains of Chivela are limestone. The Pacific Coastal Plain or Plains of Tehuantepec have a maxi- mum width of about 30 kilometers. From the base of the hills at an elevation of about 75 meters the plains slope gradually to the sea. To the west of the Rio Tehuantepec and to the east of the Plains of Tehuantepec at the base of the Sierra Madre de Chiapas, the coastal plain becomes much narrower; in these places the continuity of the plain is frequently interrupted by low north- south ridges extending outward from the mountains or by iso- lated hills. The soil is poor, varying from volcanic rock to gravel and sand. Climate The prevailing winds are from the north across the Gulf of Mexico. These moisture-laden winds precipitate most of their moisture north of the central ridges. This results in high rainfall on the northern slopes and Gulf Coastal Plain and relatively little rainfall on the southern slopes and the Pacific Coastal Plain. Precipitation is cyclic; there is a marked wet and a dry season throughout the region, but this is most noticeable on the Pacific lowlands (Fig, 3). At Salina Cruz on the Pacific Ocean the average annual rainfall is 1040 mm. (Contreras, 1942); of this amount, only 15 mm. falls from November through April. On the Gulf Coastal Plain (Minatitlan station) the average annual Amphibians of Isthmus of Tehuantepec 29 30 UJ a < 20