Ambystoma Mavortium Research Articles

Influence of agricultural landscape structure on a Southern High Plains, USA, amphibian assemblage

Landscape structure can influence demographics of spatially structured populations, particularly less vagile organisms such as amphibians. We examined the influence of agricultural landscape structure on community composition and relative abundance of the 4 most common amphibians in the Southern High Plains of central USA. Amphibian populations were monitored using pitfall traps and drift fence at 16 playa wetlands (8 playas/year) in 1999 and 2000. We quantified landscape structure surrounding each playa via estimating 13 spatial metrics that indexed playa isolation and inter-playa landscape complexity. Multivariate ordination and univariate correlations and regressions indicated that landscape structure was associated with community composition and relative abundance for 2 of the 4 amphibians. Spadefoots (Spea multiplicata, S. bombifrons) generally were positively associated with decreasing inter-playa distance and increasing inter-playa landscape complexity. Great Plains toads (Bufo cognatus) and barred tiger salamanders (Ambystoma tigrinum mavortium) usually were negatively associated with spadefoots but not influenced by landscape structure. Composition and relative abundance patterns were related to amphibian body size, which can influence species vagility and perception to landscape permeability. Spatial separation of these species in the multivariate ordination also may have been a consequence of differential competitive ability among species. These results suggest agricultural landscape structure may influence abundance and composition of spatially structured amphibian populations. This also is the first applied documentation that inter-patch landscape complexity can affect intra-patch community composition of amphibians as predicted by metapopulation theory. In the Southern High Plains, landscape complexity is positively associated with agricultural cultivation. Agricultural cultivation increases sedimentation, decreases hydroperiod, alters amphibian community dynamics, and negatively impacts postmetamorphic body size of amphibians in playa wetlands. Thus, conservation efforts should focus on preserving or restoring native landscape structure, hydroperiod, and connectivity among playas to maintain native amphibian populations and historic inter-playa movement.

Effects of Agricultural Cultivation on Demographics of Southern High Plains Amphibians

Abstract: Anthropogenic disturbance of landscapes surrounding wetlands is considered a factor in local and global amphibian declines. Few data exist on the effects of agricultural cultivation of wetland watersheds on amphibians, and results from previous studies are contradictory. Our objective was to test the effects of general anthropogenic land use (cultivation vs. grassland) on the demographics of seven species and three age classes of amphibians in the Southern High Plains of Texas. We partially enclosed 16 playa wetlands (4 per land use per year) with drift fences and pitfall traps and monitored relative daily abundance and diversity from 16 May to 17 October 1999 and 19 April to 18 August 2000. In general, relative abundance (i.e., average daily capture) of New Mexico and plains spadefoots ( Spea multiplicata, S. bombifrons) was greater at cropland than grassland playas; the abundance of other species and diversity of the amphibian assemblage was not affected by land use. Also, abundance generally was greater in 1999 than 2000 for metamorph spadefoots and barred tiger salamanders (Ambystoma tigrinum mavortium). Differences in spadefoot abundance between land‐use types may have been related to low species‐specific vagility, resulting in increased nestedness within disturbed landscapes and reduced abundance of a potential keystone intraguild predator in cropland playas. The yearly difference in amphibian abundance was likely related to annual precipitation, which influenced wetland hydroperiod. Agricultural cultivation surrounding wetlands is associated with the increased abundance of some amphibian species, but other demographic and fitness parameters—such as temporal demographics, body size, and diet diversity—may be negatively affected.

ENVIRONMENT-DEPENDENT ADMIXTURE DYNAMICS IN A TIGER SALAMANDER HYBRID ZONE

After an estimated five million years of independent evolution, the barred tiger salamander (Ambystoma tigrinum mavortium) was introduced by bait dealers into the native range of the California tiger salamander (A. californiense). Hybridization and backcrossing have been occurring in central California for 50–60 years, or an estimated 15–30 generations. We studied genetic and ecological factors influencing admixture of these two divergent gene pools by analyzing frequencies of hybrid genotypes in three kinds of breeding habitats: natural vernal pools, ephemeral man-made cattle ponds, and perennial man-made ponds. Perennial ponds tended to have higher frequencies of nonnative alleles than either type of seasonal pond, even in cases where perennial and seasonal ponds are within a few hundred meters. Thus, the hybrid zone has a mosaic structure that depends on pond hydrology or ecology. The presence of some broadly acting constraints on admixture is suggested by linkage disequilibria between physically unlinked molecular markers within ponds. In addition, we found several marker-specific deviations from Hardy-Weinberg equilibrium. One marker showed a consistent deficit of heterozygotes across pond types. Another showed heterozygote deficits only in vernal pools. A third was more likely to have heterozygote excess in ephemeral cattle ponds. These patterns indicate that admixture is influenced by complex genotype-by-environment interactions.

“Paedocannibal” Morph Barred Tiger Salamanders (Ambystoma tigrinum mavortium) from Eastern South Dakota

Abstract We report characteristics of a previously unknown population of Ambystoma tigrinum mavortium (barred tiger salamander) from eastern South Dakota, a location that extends the formerly known range of this subspecies about 150 km north. This population contains paedotypic animals and a small percentage of cannibal morphs. At least one cannibal morph was paedotypic. The vomerine tooth hypertrophy characteristic of cannibal morphs described here differs from the cannibal morph A. t. tigrinum from nearby (about 160 km) northwestern Iowa; in particular the pair of caudolateral tooth ridges has smaller teeth in individuals from the A. t. mavortium population. The study wetland is located near the convergence of four recognized (pending revision) tiger salamander subspecies (A. t. diaboli and A. t. melanosticum in addition to A. t. mavortium and A. t. tigrinum), making it an excellent region to examine subspecific morphological features in light of shared ecological factors. We suggest creating a formal n...

New Country Records and Habitat Preferences of Amphibians and Reptiles from the Sandsage Prairie in Finney County, Kansas

During the summer of 1980 a study of the herpetofauna of the sandsage prairie was conducted south of Holcomb, Finney County, Kansas. Seven new county records, the barred tiger salamander (Ambystoma tigrinum mavortium), yellow mud turtle (Kinosternon flavescens flavescens), eastern yellowbelly racer (Coluber constrictor flaviventris), western coachwhip (Masticophis flagellum testaceus), central plains milk snake (Lampropeltis triangulum gentilis), Texas longnose snake (Rhinocheilus lecontei tessellatus), and massasauga (Sistrurus catenatus) along with habitat data are reported. The sandsage prairie primarily occupies portions of 16 counties in the southwestern portion of Kansas with the largest areas, south of the Arkansas River in Hamilton, Kearny, Finney, Gray, and Ford counties (Kiichler, 1974). In 1980 a baseline study of the herpetofauna was conducted on an eight square mile section of the sandsage prairie south of Holcomb in Finney County (T.24S, R.33W, secs. 17, 18, 19, 20, 29, 30, 31, 32) and on an uncultivated area 2.9 mi. W, 11 mi. S Holcomb (T.26S, R.34W, center sec. 4). During this study 18 species of amphibians and reptiles were collected. A perusal of the literature (Collins, 1974, 1979, 1980; Collins and Caldwell, 1976, 1978; Caldwell and Collins, 1977) indicates that seven of these species represent new county records. These species are reported to (1) record the habitat preference of these species within the sandsage prairie and to (2) update the distributional record of Kansas herpetofauna. All specimens are housed in the Museum of the High Plains (MHP), Fort Hays State University, Hays, Kansas, with the exception of a previously unreported massasauga not from our study site. This specimen is housed in The Musuem of Natural History (KU), University of Kansas, Lawrence, Kansas. All common and scientific names of animals were taken from Collins et al. (1978). All common and scientific names of plants were taken from Barkley (1968). This content downloaded from 207.46.13.113 on Thu, 06 Oct 2016 04:15:17 UTC All use subject to http://about.jstor.org/terms 166 TRANSACTIONS OF THE KANSAS ACADEMY OF SCIENCE