Repository for analysis of lethal and sublethal responses of P. armatus to cold water temperatures. This analysis uses the Survival package to generate survivorship curves and determine differences in hazard between main effects. Lethal effects are tested in the survival files, sublethal responses are tested based on righting responses.
Instructions for Use and Index: Conducting analysis for both sub-lethal (righting response) and lethal (survival) effects is very similar. Both analyses include two markdown files, one for conducting the overall analysis and another for generating publication figures. Each analysis.Rmd walks through four basic steps: (1)an exploratory analysis, (2) an analysis of main effects, (3) an analysis of spatial scales, and (4) in-depth analysis for individual figures.
- ./Righting-Response/
- ./Figures/ - contains all figures of sublethal responses
- ./Righting Response Analysis.Rmd - analysis of sublethal results
- ./Righting Response Figures.Rmd - generation of righting response figures
- ./Trial1_sublethal.scv - sublethal results dataset
- ./Survival/
- ./Figures/ - contains all figures of lethal responses
- ./Survival Analysis.Rmd - analysis of lethal results
- ./Survival Figures.Rmd - generation of survival figures
- ./Trial1_survival.csv - lethal results dataset
- ./Applied Quant_Incubation Analysis.docx - written manuscript
- ./README
Abstract: The green porcelain crab, Petrolisthes armatus, is an intertidal anomuran crab with a native range extending from the Indian River, FL south to Brazil. In the mid-1990s, the species invaded northward and established populations on intertidal oyster reefs along the South Atlantic Bight, first appearing in Charleston, SC and later expanding as far north as Wilmington, NC. Petrolisthes armatus appears limited in its poleward expansion by its intolerance of extreme cold winter temperatures, although the mechanism is not well understood. Crabs collected from five locations within the species' northernmost invaded range from Savannah, GA to Wilmington, NC were used in incubation trials to determine whether cold temperatures experienced by adults induce different sublethal (loss of righting response) or lethal effects among locations, between crab sizes, or between sexes. Following an acclimation period, crabs were exposed to a chronic cold temperature trial informed by the January 2014 cold snap in Charleston Harbor, SC. Crabs from more northerly locations survived significantly longer as temperatures decreased. Regardless of location, females survived and maintained the righting response longer than males. These results suggest differences in cold tolerance between sexes, and indicate that thermal tolerance may vary along a latitudinal gradient in P. armatus.