Patterns of richness and diversity of snake communities in Texas: The influence of sampling methodology

Background/Question/Methods

The characteristics of richness and diversity are commonly addressed themes in ecological research.  Investigating these aspects of biotic communities is extremely valuable, as these data can lead to insight about a community’s productivity, efficiency, temporal stability, and robustness against perturbations.  Assessments of communities are also useful to test model predictions about the evolutionary factors that drive patterns of species richness and diversity.  Snakes play an important role in communities, both as predators and prey.  Their intermediate trophic position makes snakes ideal candidates for such research because information on a snake community may shed light on those organisms occupying trophic positions both above and below that of snakes.  Despite this potential utility, snake communities remain severely understudied, and as a result we have a paucity of data about the characteristics of many snake communities.  This lack of information is at least partially driven by the relatively secretive nature of snakes and the difficulty in sampling them.  We compared characteristics of snake communities (richness, diversity, and evenness) derived from multiple sampling methods (road-cruising, funnel-trapping, intensive searches, and pitfall trapping) on multiple sites along a gradient within Texas.  This gradient encompassed approximately 700 km, starting in Anderson County and proceeding northwest to Potter County, Texas.  We also used overlap and similarity indices to compare among methods and sites.

Results/Conclusions

Species richness varied from 14 to 20 across the three primary sites we surveyed.  However, there were noticeable differences in detection amongst sampling methods.  For example, milksnakes (Lampropeltis triangulum) and diamondback water snakes (Nerodia rhombifer) were documented only by funnel-trapping while prairie rattlesnakes (Crotalus viridis) and checkered garter snakes (Thamnophis marcianus) were documented only by road-cruising at one site.  In general, methods such as road-cruising were more successful for detecting larger-bodied, less active snakes, while funnel-trapping was more useful for detecting more active species.  Because different methods resulted in different community patterns, using them together provided better insight into the snake community, and thus a better understanding of the broader patterns of richness and diversity.