Geographic patterns of body size are of particular interest to biologists because they suggest a correlation between local environmental conditions and phenotypic expression. Bergmann's rule is a widely observed latitudinal pattern of body size in which organisms from colder latitudes possess larger body sizes than their warmer latitude counterparts. Although widely studied, the evolutionary mechanisms and environmental driving forces dictating these latitudinal patterns remain relatively underexplored. Consistent with Bergmann's rule, I found that field-collected individuals of the marine isopod Idotea baltica from Massachusetts sites are larger than individuals from Virginia sites. I raised juvenile I. balthica from populations from both regions at a range of temperatures (6°, 12°, 18°, 24°, and 30°C), and measured growth and survivorship regularly for 15 weeks or until sexual maturity. I found that body size varied positively with temperature, with individuals from Massachusetts populations possessing an overall larger body size than those from Virginia populations (MA, 18°C = 9.21 mm, MA, 24°C = 10.12 mm, VA, 18°C = 7.77 mm, VA, 24°C = 8.65 mm, p < 0.0001). Time to maturity was greater in Massachusetts populations (MA, 18°C = 71.02 days, MA, 24°C = 51.14 days, VA 18°C = 52.52 days, VA 24°C = 45.64 days, p < 0.0001), while growth rate at a given temperature was consistent across all populations, indicating that higher predation rates in Virginia habitats may be an important driving force. Field tethering experiments support this argument, with higher isopod survival rates in Massachusetts sites than Virginia sites (MA = 57%, VA = 13%, p-value = < 0.0001). My data indicates that the latitudinal body size pattern in I. balthica is adaptive, and that predation may have been an important driving force in the development of this pattern.
|Commitee:||Bell, Tina, McCandless, Amy, Murren, Courtney, Podolsky, Robert|
|School:||College of Charleston|
|School Location:||United States -- South Carolina|
|Source:||MAI 51/01M(E), Masters Abstracts International|
|Subjects:||Biology, Ecology, Evolution and Development|
|Keywords:||Bergmann's rule, Body size, Idotea balthica, Predation, Temperature, Temperature-size rule|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be