Abstract
Standing genetic variation may allow for rapid evolutionary response to the geologically unprecedented changes in global conditions. However, there is little known about the consequences of such rapid evolutionary change. Here, we measure genetic responses to experimental low and high pCO 2 levels in purple sea urchin larvae, Strongylocentrotus purpuratus. We found greater loss of nucleotide diversity in high pCO 2 levels (18.61%; 900 μatm) compared to low pCO 2 levels (10.12%; 400 μatm). In the wild, this loss could limit the evolutionary capacity of future generations. In contrast, we found minimal evidence that purple sea urchin larvae physiologically respond to high pCO 2 through alternative splicing of transcripts (11 genes), despite a strong signal of alternative splicing between different developmental stages (1193 genes). However, in response to high pCO 2, four of the 11 alternatively spliced transcripts encoded ribosomal proteins, suggesting the regulation of translation as a potential response mechanism. The results of this study indicate that while the purple urchin presently may have enough standing genetic variation in response to rapid environmental change, this reservoir of resilience is a finite resource and could quickly diminish.
Highlights
Increasing atmospheric carbon due to anthropogenic activities lowers ocean pH causing changes to ocean carbonate chemistry (Doney et al 2009; Ho€nisch et al 2012)
There was significant loss in genetic diversity of cultured larvae between day 1 and day 7 in both high and low pCO2 conditions; the percent nucleotide diversity lost in high pCO2 was significantly more than in low pCO2 (P < 0.0001, Table 1). pCO2 treatment alone, pooled across days, was not a significant predicting factor of nucleotide diversity, indicating the negative effect of increased pCO2 acts through developmental time (Fig. 1)
The total number of polymorphic SNPs decreased between day 1 and day 7 in both high and low pCO2 conditions; the number of polymorphic SNPs lost in high pCO2 was significantly more than in low pCO2
Summary
Increasing atmospheric carbon due to anthropogenic activities lowers ocean pH causing changes to ocean carbonate chemistry (Doney et al 2009; Ho€nisch et al 2012). The consequences of ocean acidification for many ecologically and economically important marine organisms are slower growth, reduced fecundity, and higher mortality (Guinotte and Fabry 2008; Kroeker et al 2010; Gaylord et al 2011). To avoid such negative impacts of fast-changing environmental conditions, organisms will have to move to more favorable conditions, physiologically acclimatize, or genetically adapt (Somero 2010; Hoffmann and Sgro 2011). We tested the hypothesis that the changes in allele frequency observed in the purple sea urchin in response to increased pCO2 resulted in decreased genetic diversity
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