DISSERTATION RESEARCH: The adaptive significance of shell color variation in the flat periwinkle Littorina obtusata

University Of Pennsylvania, Philadelphia PA

Investigators

Abstract

The marine snail Littorina obtusata is noted for remarkable diversity in shell color. Shell color is expected to affect absorption of visible light that may in turn impact body temperature and fitness. Previous results suggest that patterns of shell color diversity in the Gulf of Maine are driven by variation in thermal regime. Lighter shell colors increase in frequency in hotter, more exposed habitats in the Gulf of Maine whereas dark colors dominate populations in cooler areas. In addition, manipulative experiments demonstrated that light shell colored snails are at a fitness advantage under hot, dry conditions. The proposed study will further test the relationship between shell color and fitness, examining growth and mortality rates under cold stress and behavioral responses to thermal stress in the field. The proposed study will provide a compelling example of the importance of variation in thermal regime as a selective force in natural populations. Such examples are rare, particularly in natural systems with significant ecological relevance. Further, understanding how organisms respond and adapt to variable thermal regimes may generate concrete predictions as to which populations and species are most vulnerable to environmental change and better inform the methods used to protect important ecosystems. Monitoring the distribution of shell color frequencies in L. obtusata may prove to be a cost-effective, tractable method for tracking the effects of climate change in ecological communities.