PS 15-8 - CANCELLED - Thermal ecology and intra-specific variation in Rabidosa rabida (Araneae: Lycosidae) from the mountains of Arkansas

Tuesday, August 9, 2011
Exhibit Hall 3, Austin Convention Center
Ryan J. Stork, Biology, The University of Texas at Arlington, Arlington, TX

Temperature affects all levels of biological organization and ultimately affects multiple aspects of ecological performance and fitness.  Generalist arthropod predators, which exert top down effects on ecosystems, are strongly affected by temperature in ways that are not understood.  Descriptions of thermal ecology of important generalist arthropod predators are, therefore, essential pieces of information for studying ecology in changing thermal environments.  This study examined the thermal ecology of the spider Rabidosa rabida (Araneae: Lycosidae) using three common descriptive measures.  All spiders used were collected at elevations above 609m or below 365m from both Mount Magazine and Rich Mountain in Arkansas.  Elevation groups differed in temperature by 1-3◦C as did mountain locations.  Spiders were placed in a thermal gradient to determine thermal preference.  Other spiders had their body temperature increased or decreased until they reached their thermal limit and lost the ability to move.  Finally sprint speed was measured across five ecologically relevant temperatures in an incubator.  Thermal ecology results were compared between populations and sexes to examine intra-specific variation in thermal ecology measures between groups.  It was expected that differences would be found between mountain, elevation, and sex groups due to the strong effects of temperature on ectotherm performance and ecology.


Thermal preference of R. rabida, not corrected for body size, was determined to be 32+/-0.282◦C and differed only between sexes.  The mean critical thermal maximum was determined to be 43.5+/-0.413◦C with no differences shown between groups.  Apparent differences were seen between critical maxima of elevation groups and sexes.  The mean critical thermal minimum was estimated to be 0+/-1◦C.  There were no differences between groups.  Maximum sprint speed showed a slow increase across temperatures that could be experienced in the field (15-35◦C at 5◦ intervals).  Differences in sprint speed between some but not all temperature groups and between populations collected at different elevations were found.  This data provides a first description of the thermal ecology and intra-specific variation in this large generalist arthropod predator.  It also describes intra-specific variation between geographic locations and locations differing in temperature by only 1-3◦C.  Intra-specific variation provides a potential basis for adaptation to changing thermal environments.  Studying this variation can show us what the effects of relatively small temperature changes, such as those expected from global warming, might be on an arthropod predator that exerts interesting ecological effects on other organisms.  Spiders are also shown to be promising study organisms for future thermal ecology studies.

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