Tuesday, April 14, 2015

Heat Resistance in Reef-Building Corals

Discussing:  Bay, R.A. and Palumbi, S.R. 2014. "Multi-locus adaptation associated with heat resistance in reef-building corals". Current Biology 24: 252-2956.

Introducing their informative study, Bay and Palumbi (2014) write that "physiology and gene expression patterns have shown that corals living in naturally high-temperature microclimates are more resistant to bleaching because of both acclimation and fixed effects, including adaptation," citing in this regard the slightly earlier work of Palumbi et al. (2014). And in further searching for potential genetic correlates of these fixed effects, they go on to describe how they "genotyped 15,399 single nucleotide polymorphisms (SNPs) in 23 individual table top corals, Acropora hyacinthus, within a natural temperature mosaic in backreef lagoons on Ofu Island, American Samoa."

This effort led to the two researchers identifying 114 highly divergent SNPs that appeared to be good candidates for environmental selection, as a result of multiple stringent outlier tests they conducted, as well as the corals' evident correlations with temperature. More specifically, they report that "corals from the warmest reef location had higher minor allele frequencies across these candidate SNPs, a pattern not seen for non-candidate loci." In addition, they discovered that "within backreef pools, colonies in the warmest microclimates had a higher number and frequency of alternative alleles at candidate loci."

In discussing the significance of their findings, Bay and Palumbi say they imply a "mild selection for alternate alleles at many loci in these corals during high heat episodes and possible maintenance of extensive polymorphism through multi-locus balancing selection in a heterogeneous environment," which leads them to their ultimate conclusion that a natural population of these corals "harbors a reservoir of alleles preadapted to high temperatures, suggesting potential for future evolutionary response to climate change."