MEPS 556:143-159 (2016)  -  DOI: https://doi.org/10.3354/meps11850

ABSTRACT: Southern California (USA) populations of the intertidal snail Chlorostoma funebralis occupy warmer climates than northern California populations, and southern populations are more thermally tolerant and have unique transcriptomic responses to heat stress compared to northern populations. To investigate how climate affects body temperature patterns for C. funebralis, iButton temperature loggers encased in empty C. funebralis shells (robosnails) were deployed at 3 northern and 3 southern California sites for 1.5 mo in the late summer and early fall of 2014, typically when maximum annual temperatures are reached. Measurements revealed that southern, thermally tolerant populations experienced higher average daily maximum and absolute maximum temperatures than northern, less tolerant populations, and that robosnails in southern, but not northern, California exceeded temperatures that cause 100% mortality. Similarly, the probability of a site reaching 27°C, the temperature that induces the heat shock response in C. funebralis, was 3 times higher at the southern compared to the northern sites. To determine whether these exposures to stressful temperatures are related to gene expression differences, we then tested for a correlation between the probability of reaching 27°C and the constitutive (non-induced) expression of genes previously implicated as pre-adapted in southern California populations. We identified 222 genes (including 14 involved in ubiquitin protein degradation, a response to heat stress) with a significant correlation. The results demonstrate how combining in situ temperature and transcriptome data can increase our understanding of thermal adaptation and better inform predictions regarding the impact of future climate change.

KEY WORDS: Body temperature · Pre-adaptation · Heat stress · Rocky intertidal · Mollusk · Gene expression