Richmond J.Q.,U.S. Geological Survey |
Wood D.A.,U.S. Geological Survey |
Swaim K.E.,Swaim Biological Incorporated |
Fisher R.N.,U.S. Geological Survey |
Vandergast A.G.,U.S. Geological Survey
Herpetologica | Year: 2016
We used microsatellites and mtDNA sequences to examine the mixed effects of geophysical, habitat, and contemporary urban barriers on the genetics of threatened Alameda Striped Racers (Coluber lateralis euryxanthus), a species with close ties to declining coastal scrub and chaparral habitat in the eastern San Francisco Bay area of California. We used cluster assignments to characterize population genetic structuring with respect to land management units and approximate Bayesian analysis to rank the ability of five alternative evolutionary hypotheses to explain the inferred structure. Then, we estimated rates of contemporary and historical migration among the major clusters and measured the fit of different historical migration models to better understand the formation of the current population structure. Our results reveal a ring-like pattern of historical connectivity around the Tri-Valley area of the East Bay (i.e., San Ramon, Amador, and Livermore valleys), with clusters largely corresponding to different management units. We found no evidence of continuous gene flow throughout the ring, however, and that the main gap in continuity is centered across the Livermore Valley. Historical migration models support higher rates of gene flow away from the terminal ends of the ring on the north and south sides of the Valley, compared with rates into those areas from western sites that border the interior San Francisco Bay. We attribute the break in ring-like connectivity to the presence of unsuitable habitat within the Livermore Valley that has been reinforced by 20th century urbanization, and the asymmetry in gene flow rates to spatial constraints on movement and east-west environmental gradients influenced by the proximity of the San Francisco Bay. © 2016 by The Herpetologists' League, Inc.
McCoy E.D.,University of South Florida |
Britt E.J.,Swaim Biological Inc. |
Catenazzi A.,Southern Illinois University Carbondale |
Mushinsky H.R.,University of South Florida
Natural Areas Journal | Year: 2013
The Florida Scrub ecosystem depends on fire to sustain ecosystem function and to support resident plant and animal species. A recent study addressed the relationship between the time since last fire (TSF) and resident amphibians and reptiles in rosemary bald, one Florida Scrub habitat type. This is a parallel study in another Florida Scrub habitat type, scrubby flatwoods, at Archbold Biological Station (ABS), Lake Placid, Florida, USA. We installed 36 400-m 2 enclosures (four burn units within each of three TSF categories X 3 replicates per burn unit) at ABS. Bucket trap sampling, within and outside the enclosures, occurred during the spring and late summer in 2007 and 2008. Ten environmental variables that reflect differences in the biotic and abiotic conditions of the microhabitats associated with different TSF were surveyed. Eleven species of reptiles and six species of amphibians were captured. Three lizard species together accounted for > 95% of the reptile captures, and two toad species together accounted for > 96% of the amphibian captures. Abundance of the Florida Sand Skink (Plestiodon reynoldsi Stejneger) was highest in long-unburned areas, probably because of the accumulated litter; but abundances of the other two lizard species did not show a relationship with TSF. Differences in relative abundances of species between sampling years may be a function of the difference in rainfall. Despite substantial variation in sampling methods between this study and the previous one, the herpetofaunal composition of the two habitat types were found to be similar; differences in diversity between them was attributable mostly to differences in relative abundances. Species inhabiting the Florida Scrub ecosystem respond differently to TSF: the federally-listed Florida Scrub Jay (Aphelocoma coerulescens Bosc), for example, requires more frequent burning than appears to be the case for the Florida Sand Skink. A land management plan of stochastic return intervals and spatial variation of high-intensity fires to maintain a mosaic landscape would be ideal; but management options for maintaining the diversity of all species inhabiting the Florida scrub ecosystem are limited, because of the generally small size of remaining habitat patches.
Reeder N.M.M.,Swaim Biological Inc. |
Byrnes R.M.,Swaim Biological Inc. |
Stoelting R.E.,Swaim Biological Inc. |
Stoelting R.E.,University of Wisconsin - Madison |
Swaim K.E.,Swaim Biological Inc.
Endangered Species Research | Year: 2015
The endangered San Francisco garter snake Thamnophis sirtalis tetrataenia occurs in only 2 counties on the densely populated San Francisco Peninsula, California, USA. Due to its limited geographic range and destruction of populations by the rapid pace of urban development in the 1950s and 1960s, T. s. tetrataenia was the only snake included in the inaugural US Endangered Species Act. Several large areas preserved as public parks, utility lands, or private trusts support remnant populations that are the focus of recovery and conservation efforts. To assist in assessment of status and trend for this subspecies, we fit Huggins' closed capture models in RMark to mark-recapture data collected in 2007 and 2013 to estimate population size of an isolated population on a small (72.8ha) property surrounded by residential development and transportation infrastructure. Our best supported models indicate a population of 1763 individuals (95% CI: 1302-2446) in 2007 and 1761 (95% CI: 1211-2639) in 2013. In addition, total captures of an important prey species increased 2 orders of magnitude from 829 in 2007 to 17 180 in 2013. These findings highlight the potential for well-managed but small habitat units ('the good'), to compliment vast natural areas ('the ideal') in recovery and conservation strategies for threatened and endangered species that can be supported by a small home range. © The authors 2015.