Evolution of temperature tolerance in the introduced seaweed <i>Gracilaria vermiculophylla</i>.

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Shainker, Sarah
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The red macroalga <i>Gracilaria vermiculophylla</i> is native to the Northwest Pacific and invaded North American and European coastlines in recent decades. We tested whether the success of this invasion was aided by genetic adaptation of temperature tolerance. We sampled 15 native Japanese populations and 25 introduced populations from North America and Europe. Within a week of field collection, we subjected samples to extreme hot and cold temperatures then followed their rates of bleaching and survivorship for 8 days following exposure. Significantly more native populations bleached and died after hot and cold exposure compared to introduced populations. Similar results were found when common garden samples were exposed to heat, suggesting that the greater thermal tolerance among introduced populations has a genetic basis. Given the invasion history of this species, we propose that adaptation to greater heat tolerance occurred post-introduction. Evolution in this and other algal traits facilitated invasion success.
biological invasion, evolution, introduced species, thermal tolerance