Citation:

JAEGER, J., D. F. BRADFORD, AND R. BRETT. POPULATION STRUCTURE OF THE RED-SPOTTED TOAD, BUFO PUNCTATUS, IN A NATURALLY FRAGMENTED DESERT LANDSCAPE. Presented at Annual Meeting of California-Nevada Amphibian Poplulations Task Force, Las Vegas, NV, January 18 - 20, 2007.

Impact/Purpose:

The primary objectives of this research are to:

Develop methodologies so that landscape indicator values generated from different sensors on different dates (but in the same areas) are comparable; differences in metric values result from landscape changes and not differences in the sensors;

Quantify relationships between landscape metrics generated from wall-to-wall spatial data and (1) specific parameters related to water resource conditions in different environmental settings across the US, including but not limited to nutrients, sediment, and benthic communities, and (2) multi-species habitat suitability;

Develop and validate multivariate models based on quantification studies;

Develop GIS/model assessment protocols and tools to characterize risk of nutrient and sediment TMDL exceedence;

Complete an initial draft (potentially web based) of a national landscape condition assessment.

This research directly supports long-term goals established in ORDs multiyear plans related to GPRA Goal 2 (Water) and GPRA Goal 4 (Healthy Communities and Ecosystems), although funding for this task comes from Goal 4. Relative to the GRPA Goal 2 multiyear plan, this research is intended to "provide tools to assess and diagnose impairment in aquatic systems and the sources of associated stressors." Relative to the Goal 4 Multiyear Plan this research is intended to (1) provide states and tribes with an ability to assess the condition of waterbodies in a scientifically defensible and representative way, while allowing for aggregation and assessment of trends at multiple scales, (2) assist Federal, State and Local managers in diagnosing the probable cause and forecasting future conditions in a scientifically defensible manner to protect and restore ecosystems, and (3) provide Federal, State and Local managers with a scientifically defensible way to assess current and future ecological conditions, and probable causes of impairments, and a way to evaluate alternative future management scenarios.

Description:

We investigated the spatial scale at which genetic structure of Bufo punctatus within the Mojave

Desert is organized by sequencing a portion of mitochondrial DNA control region for 831 toads

collected from 43 sites around Las Vegas, Nevada. We grouped these collections a priori into seven geographic ranges based predominately on clusters of sites within mountain ranges. We used hierarchical analysis of molecular variance (AMOVA) in a series of nested procedures to assess genetic structure among mountain ranges, among sites within mountain ranges, and among

individuals within sites. We also calculated pairwise FST among sites within mountain ranges, and inferred population processes within mountain ranges by applying neutrality test statistics. We identified 36 haplotypes that formed five groups using network analysis, and an additional haplotype at three sites that represented recently colonized B. punctatus from the Colorado

Plateau. The designated mountain ranges accounted for a significant amount (25.8%) of genetic variation, and we confirmed substantial genetic structure between most neighboring ranges. Within four mountain ranges, we found little genetic variation among collection sites, and

inferred that a population bottleneck or range expansion likely explained a lack of diversity within two of these ranges. Within three mountain ranges we found significant genetic structure among sites; however, within two of these ranges only a few sites generally accounted for most of the pattern. Within the third range the observed structure appears to have resulted from a recent

convergence of two divergent lineages. Our assessment supports the perspective that within the Mojave Desert, B. punctatus occurs primarily in patchy populations within mountain ranges that are currently isolated from similar populations in neighboring ranges.

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