Melina Giakoumis' evidence of hybridization and adaptation in Asterias sea stars is published in Molecular Ecology.
Hybridization occurs when two species cross breed to successfully make offspring. Two species of North Atlantic sea stars, the North American Asterias forbesi and European Asterias rubens, known to cross breed in laboratory settings, were long suspected of hybridizing in their natural habitat.
Using genomic data and environmental niche modeling, City College of New York biology PhD Melina Giakoumis, associate director of the Institute for Comparative Genomics at the American Museum of Natural History, documented hybridization occurring along the coast from New England to the southern Canadian Maritimes. She then studied how environmental differences could have driven natural selection within and between species.
Sea stars such as A. rubens and A. forbesi are crucial to the health of intertidal ecosystems. As keystone species, their survival has a disproportionate impact on the fate of other species in their communities. “If their population crashes, other species follow,” said Giakoumis. However, the ecosystems where these sea stars once flourished are rapidly changing. “The Gulf of Maine is warming faster than 99 percent of the global ocean.” Sea stars the western North Atlantic ecosystem have been in serious decline since the 1970s.
Giakoumis found certain genomic variations in both species were driven by temperature. In the North American A. forbesi this genomic variation was statistically associated with long-term minimum temperatures. Conversely, long-term maximum temperatures were a factor for A. rubens, whose distribution extends along the North Atlantic intertidal zone well into the Arctic along the Norwegian coast.
For both species, nitrate concentration in their environment was highly associated with allelic variation, which may be important for a population’s potential for adaptability and survival.
“Will the hybrids’ movements follow the changes in sea surface temperatures so that eventually one species replaces the other?” said Giakoumis’ advisor, CCNY Biology Professor Michael Hickerson. Equally possible, hybridization could save the two species by generating a beneficial source of adaptive genetic variation.
Understanding these species’ adaptations to the environment will have implications for wildlife management and conservation in the North Atlantic intertidal region.
The study appears in the journal Molecular Ecology.
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