Rocks and clocks: linking geologic history and rates of genetic differentiation in anchialine organisms |
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Authors: | Scott R Santos David A Weese |
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Institution: | (1) Department of Biological Sciences, Cell & Molecular Biosciences Peak Program and Molette Biology Laboratory for Environmental and Climate Change Studies, Auburn University, 101 Life Sciences Building, Auburn, AL 36849-5407, USA |
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Abstract: | The geologic history of a region can significantly impact the development of its flora and fauna, with past events shaping
community patterns and evolutionary trajectories of species. In this context, islands are excellent “natural laboratories”
for studying the fundamental processes of evolution due to their discrete geographical nature and dynamic geologic histories.
An island system meeting these criteria is the Hawaiian Archipelago, which is ideal for testing how island geologic history
influences the processes leading to population genetic variation and differentiation. One Hawaiian endemic whose evolutionary
history is closely tied to the geology of the islands is the anchialine atyid shrimp Halocaridina, whose mitochondrial cytochrome oxidase I (COI) gene is hypothesized to be evolving at the rate of 20% per million years.
To validate this rapid evolutionary rate, time since divergence estimates between geographically close, yet genetically distinct,
populations were calculated for Halocaridina from anchialine habitats on the islands of Hawai’i, Maui, and O’ahu. On the younger (i.e., <1.5 million years) islands of
Hawai’i and Maui, where all anchialine habitats occur in basalt, application of the Halocaridina molecular clock identified a strong correlation between levels of genetic divergence and the geologic age of the region inhabited
by those populations. In contrast, this relationship weakened when similar analyses were conducted for Halocaridina from limestone anchialine habitats on the older (i.e., >2.75 million years) island of O’ahu. These results suggest geologic
age, basin origin and/or composition are important factors that should be taken into consideration when conducting molecular
clock analyses on anchialine flora and fauna as well as island populations in general. |
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