James E. Platz

|[tdot]|and turn back again

The conventional view of evolutionary relationships within the living reptiles is that turtles are basal to the other groups. Their placement is based largely on the absence in turtles of temporal fenestrae, openings on either side of the skull involved in jaw muscle attachment, which all other groups of living reptiles and their descendants have. Rieppel and deBragas recent analyses of fossil and living groups of reptiles challenged this long-held conclusion, although their results have since been questioned. We present a molecular analysis in support of Rieppel and deBragas original conclusions.

COMPARATIVE ASSESSMENT OF MODES OF REPRODUCTIVE ISOLATION AMONG FOUR SPECIES OF LEOPARD FROGS (RANA PIPIENS COMPLEX)

It is well known that sympatric congeneric species maintain their respective identities by limiting interspecific gene exchange. Mayr (1963) has outlined the principal categories of mechanisms that result in reproductive isolation. Following Mecham (1961), he classifies such mechanisms as either premating (methods that limit wastage of reproductive effort and are subject to selective improvement) or postmating (methods that limit the success of interspecies matings and are not subject to direct selective improvement). Mayr stressed that typically it is the interplay of many reproductive isolating mechanisms that is responsible for limiting interspecific breeding, but that one factor often is dominant. For example, in anurans it is generally believed that the mating call is typically the primary factor responsible for accomplishing mating discrimination between congeners (Blair, 1974). In recent years, considerable attention has been focused on elucidating reproductive isolating mechanisms and associated gene-flow characteristics in species complexes. The leopard frogs, Rana pipiens complex, have proven useful subjects for such studies (Mecham, 1968; Platz, 1972, 1976, 1981; Platz and Platz, 1973; Kruse and Dunlap, 1976; Frost and Bagnara, 1977a, 1977b; Sage and Selander, 1979; Hillis, 1981) because member species generally share narrow zones of geographical contact. Although progress has been made much remains to be learned about reproductive isolating mechanisms within the complex. Four species of leopard frogs are known to occur in the extreme southwestern United States. One of them, R. chiricahuensis (Platz and Mecham, 1979) has been found in sympatric association with each of the other three species-namely, R. pipiens, R. blairi and the lowland form (Platz and Frost; species description unpubl.) of leopard frog. The distributions of the latter three frogs appear to be allopatric with respect to one another in this region (Fig. 1). Electrophoretic marker loci (Platz and Platz, 1973; Platz, 1976) demonstrate that about 9% of the individuals collected from sympatric populations of R. chiricahuensis and R. pipiens represented derived progenies (hybrids). This compares with a derived progeny frequency of 3% for individuals collected from sympatric populations of R. chiricahuensis and the lowland form of leopard frog. Furthermore, no derived progeny were detected either by the electrophoretic comparison of hemoglobins or the comparison of mating calls from sympatric populations of R. chiricahuensis and R. blairi (Frost and Bagnara, 1977b). For the most part, the mechanisms responsible for limiting hybridization are unknown. Therefore, the purpose of this study was to make a comparative assessment of the modes of reproductive isolation that best explain the limited hybridization observed between each species pair.

Rana yavapaiensis, a new species of leopard frog (Rana pipiens complex)

Rana yavapaiensis, a distinctive new species of the R. pipiens complex, occupies lower elevation aquatic habitats in the western third and southern half of Arizona and adjacent Sonora, Mexico. It is similar to but distinguishable from R. chiricahuensis and R. magnaocularis. The new species is sympatric over part of its range with R. chiricahuensis. Where they occur together the production of F, hybrids was low and presumed backcross individuals were not detected. Comparisons of preserved specimens of the new species with type specimens of both R. onca and R. fisheri indicate that R. yavapaiensis is distinct from each of these

Age Distribution and Longevity in the Ramsey Canyon Leopard Frog, Rana subaquavocalis

-Phalangeal elements from 80 individuals from two populations of the Ramsey Canyon leopard frog, Rana subaquavocalis, were sectioned, stained and then examined to estimate individual ages and to determine population age structure and growth curves. Large adults from the Ramsey Canyon population exceeded 100 mm in body length and had as many as 10 resting lines indicating that they were 11 years postmetamorphosis. In contrast the majority of the 38 specimens from the Barchas Ranch population were small, under 70 mm in body length, and were five or less years old. Growth curves for both populations were constructed based on body size and the number of resting lines in bone sections. Growth rates for males in the Ramsey Canyon population are lower than females. The population age structure revealed in this study has implications to conservation efforts. Our findings suggest that the Ramsey Canyon population was composed largely of reproductive and very old reproductive individuals whereas at the time of analysis the Barchas Ranch population was larger and contained mostly prereproductive individuals. During the summer of 1988 large ranid frogs were discovered in Ramsey Canyon in the Huachuca Mountains, Cochise Co., southeastern Arizona. They were subsequently recognized as a new species, Rana subaquavocalis, by Platz (1993). Currently they are known to occur only from this small mountain range, making it the geographically most restricted species among the seven described leopard frogs in the United States. Until recently they existed in natural plunge pools created by water flow along Ramsey Creek at an elevation of approximately 1600 m. However, most of the Ramsey Canyon population now inhabit a 15 x 15 m man-made concrete tank adjacent to the creek (Fig. 1, Site 1). Subsequent survey work uncovered a second breeding population on the Barchas Ranch (Fig. 1, Site 3), less than 6 km away. At the time of this study, a total of four localities (Fig. 1) were known to have adults, but only the two indicated above have a sustained history of successful breeding. Adults at the Ramsey Canyon study pond (Site 1) are large compared to most species of leopard frogs. Some females reach 120 mm snout-urostyle length (SUL) and males, although smaller, often reach 90 mm and sometimes 100 mm SUL. Amphibians appear generally to have indeterminate growth (Duellman and Trueb, 1986) although the rate decreases greatly after sexual maturity. The Barchas Ranch population (Site 3) appeared to consist of much smaller individuals, and observations in June-July of 1992 indicated that tadpoles all metamorphosed at this time, in contrast to the repeated observation of tadpoles overwintering at the Ramsey Canyon site (Platz, unpubl. data). The large body size of adults at Ramsey Canyon suggested that they might be quite old because of indeterminate growth at a low rate. This question, the smaller body sizes at the Barchas Ranch, along with the limited distribution and very small population size (an estimated number of fewer than 100 adult individuals) prompted the present study to determine the age structure of these two populations. Small population size and limited sites and additional evidence of recent declines in other leopard frog species in Arizona (Clarkson and Rorabaugh, 1989; Sredl and Howland, 1994) make obtaining population age structure and longevity data critical issues. METHODS AND MATERIALS Ramsey Canyon frogs (N = 42) were hand captured on 27 April and 25 May 1990 and 8 July 1991 to obtain toe samples. Toes were obtained from the Barchas Ranch population (N = 38) on 8, 16, and 21 June 1995. Individuals were sexed on the basis of the presence of well developed external vocal sacs (only in the case of animals larger than 80 mm SUL) and measured for body length (SUL) from the tip of the snout to the base of the urostyle and recorded to the nearest mm. The distal two phalangeal elements of the fourth toe from the right hind foot were This content downloaded from 157.55.39.27 on Wed, 07 Sep 2016 05:55:38 UTC All use subject to http://about.jstor.org/terms POPULATION AGE STRUCTURE-RANA surgically removed, placed in 10% formalin, and stored until sectioned. Skeletochronological studies followed the protocol of Hemelaar and Van Gelder (1980). Toes were decalcified in 5% nitric acid for 5 to 6 and left in water overnight. The mid-diaphyseal region of the distal phalangeal element of each toe was then sectioned at 20 um using a Spencer model 880 freeze microtome. The resulting sections were mounted on slides in an albumen-glycerin preparation and stained in Cabiscos Delafield Hematoxylin for 10 min. Stained slides were examined under a compound microscope to determine the number of resting lines (RLs). Age estimates were then determined by counting RLs which appear as darker stained rings separating lighter bands of bone material. The resulting age estimates were used in conjunction with body size to examine variation in size in relation to age and to compare population age structure between the Ramsey Canyon and Barchas Ranch sites. To compare populations, growth parameters (von Bertalanffy, 1938) were fitted to growth curves using the nonlinear procedure utilizing the Powell variant of the Levenberg-Marquardt methodology (Micromath Scientist, 1995). The equation form used was: St = Smax (Smax S0)e-k(t-t), where: t = age estimate in years, to = age at metamorphosis, set at 0.5 yr, St = size at age t (in mm), Smax = asymptotic maximum size, So = size at age to, k = growth coefficient. Population census data from 1990 through 1995 were examined to determine trends at the Ramsey Canyon site.

Sympatric Interaction between Two Forms of Leopard Frog (Rana pipiens Complex) in Texas

. 1955. Seasonal changes in the gross organ composition of the lizard Anolis carolinensis. J. Exper. Zool. 128:1-12. GOLDBERG, S. R. 1970a. Ovarian cycle of the mountain spiny lizard Sceloporus jarrovi Cope. Ph.D. dissertation, Univ. of Arizona, Tucson. .1970b. Seasonal ovarian histology of the ovoviviparous iguanid lizard Sceloporus jarrovi Cope. J. Morph. 132:265-276. 1971. Reproductive cycle of the ovoviviparous iguanid lizard Sceloporus jarrovi Cope. Herpetologica 27:123-131. HAHN, W. E. 1967. Estradiol-induced vitellogenesis and concomitant fat mobilization in the lizard Uta stansburiana. Comp. Biochem. Physiol. 23:83-93. , AND D. W. TINKLE. 1965. Fat body cycling and experimental evidence for its adaptive significance to ovarian follicle development in the lizard Uta stansburiana. J. Exp. Zool. 158:79-86. HODDENBACH, G. A. 1966. Reproduction in western Texas Cnemidophorus sexlineatus (Sauria:teiidae). Copeia 1966:110-113. LOWE, C. H. 1964. The vertebrates of Arizona. Univ. of Arizona Press, Tucson. LUFT, J. 1961. Improvements in epoxy resin embedding methods. J. Biophysic. Biochem. Cytol. 9:409-414. MAYHEW, W. W. 1971. Reproduction in the desert lizard Dipsosaurus dorsalis. Herpetologica 27:57-77. MILLER, M. R. 1954. Further observations on reproduction in the lizard Xantusia vigilis. Copeia 1954:38-40. MINNICH, J. E. 1971. Seasonal variation in weight-length relationships and fat body size in the desert iguana Dipsosaurus dorsalis. Copeia 1971:359-362. REYNOLDS, E. S. 1963. The use of lead citrate at high ph as an electron-opaque stain in electron microscopy. J. Cell. Biol. 17:208-212. SMITH, R. E. 1968. Experimental evidence for a gonadal fat body relationship in two teiid lizards Ameiva festiva and Ameiva quadrilineata. Biol. Bull. 134:325-331. TELFORD, S. R. 1970. Seasonal fluctuations in liver and fat body weights of the Japanese lacertid Takydromus tachydromoides Schlegel. Copeia 1970:681-688.

Speciation within the Chorus Frog Pseudacris triseriata: Morphometric and Mating Call Analyses of the Boreal and Western Subspecies

Data from mating call and morphological analyses of the boreal and western subspecies of the chorus frog Pseudacris triseriata were obtained along a transect from South Dakota to Oklahoma. Two call types are evident. At the northern end of the transect calls are long and low in pulse rate. Both traits had low variability relative to populations further south. The southern end of the transect contained populations with a much shorter call and pulse rates approximately twice those in the north. Identical long and short call types are evident in Colorado as well. Limited data from Oklahoma indicates that the call of P. triseriata feriarum is more like that of P. t. maculata. Multivariate stepwise discriminant analyses performed on data sets containing only morphological measurements produced two clusters of populations which correspond on geographic grounds to two currently recognized subspecies, P. t. maculata and P. t. triseriata. When call data are included, the same two clusters are identified suggesting concordance between call type and morphology. The data indicate that the two entities represent separate species and that the zone of overlap is much more extensive than previously depicted.

Biochemical and Morphological Variation of Leopard Frogs in Arizona

Evaluation of electrophoretic and morphological traits reveals three distinct members of the Rana ipipens complex present in Arizona. Examination of 653 frogs from 34 sites indicates that these three forms, designated Northern, Southern and Lowland, are largely allopatric and can be distinguished from each other morphologically. Where geographic replacement occurs, the transition is discontinuous with respect to protein phenotypes and associated morphology. The Southern type is sympatric at a number of locations with either the Lowland or the Northern form. Where sympatry occurs the morphotypes and their associated protein patterns remain essentially distinct except for occasional hybrids. Ten Northern-Southern F1 hybrids and three backcrosses have been identified among 143 individuals from sympatric sites. Only F1 hybrids (3/43) were detected among the 96 individuals from Lowland-Southern collecting sites. F1 hybrids are rare and backcrosses even rarer. Both the morphological and electrophoretic findings support the recent work of my own and numerous others suggesting that the Rana ipipens complex consists of several species.

Rana berlandieri: Recently Introduced Populations in Arizona and Southeastern California

are consistent with the morphology and mating call of Rana berlandieri, a member of the R. pipiens complex native to southwestern Texas and parts of southeastern New Mexico and Mexico. Electrophoretic comparisons of the unknown with tissues from Texas, New Mexico, and Mexico specimens confirm the above identification. The allelic configurations found in New Mexico populations of R. berlandieri also occur in the Yuma area specimens, suggesting eastern New Mexico as the original source. Present assessment indicates that these frogs are apt to spread further in Arizona and possibly into Mexico and California as well. Little is currently known concerning the impact on native fauna.

Limited Genetic Heterozygosity and Status of Two Populations of the Ramsey Canyon Leopard Frog: Rana subaquavocalis

Abstract Using starch gel electrophoresis, we examined proteins specified by 41 presumptive loci representing two breeding populations of Rana subaquavocalis, a recently described species of leopard frog from Arizona. Individual and population levels of heterozygosity were low. Mean number of alleles detected (1.2) and mean levels of individual heterozygosity were higher at the Barchas Ranch location (0.042) compared with those from Ramsey Canyon (0.029). Nine loci among the 41 surveyed were polymorphic. Four of these were common to both populations. Each population was polymorphic for the remaining three loci, and each possessed one unique allele. Both populations went extinct by 1996.