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Oceanography Seminar

February 14, 3:00pm - 4:15pm
Mānoa Campus, MSB 100

Tom Oliver
Hawai'i Institute of Marine Biology
University of Hawai'i

"Comparative Evolutionary Ecology and Next-Generation Genomics Reveal Patterns of Selection in Deep Sea Urchins and Over-heated Reef Corals"

Abstract: Recent advances in nucleic acid sequencing have brought the full power of genomic analysis into "non-model" systems, and thereby have empowered evolutionary biologists to deeply query systems that pose fundamentally interesting questions about the process of adaptation. In this seminar I will focus on two such systems: first, closely related shallow and deep-sea urchins, and second, reef corals living near their critical thermal thresholds.

First, we compare three Strongylocentrotid urchins, one of which has recently diverged from the ancestral habit of a shallow-water lifestyle, and adapted to survive in the deep sea (~1000 m). Here we ask if adaptation to a novel habitat can leave patterns discernable at the whole-genome scale. We compare thousands of genes across these species (9,258 - 14,543 genes) that differ in stage and tissue-specific expression, and we examine patterns of purifying & positive selection as indicated by patterns of substitution in protein-coding regions. By using traditional non-synonymous/synonymous substitution indices (dN/dS) as well as a maximum likelihood branch-specific model (HYPHY), we show that all species show predictable differences in tissue/stage specific selective constraint, but the recent deep-sea invader shows elevated rates of adaptive evolution. These elevated rates are particularly high in genes associated with biomineralization, a function challenged by the low carbonate saturation environment of the deep sea.

Second, we will explore an on-going research program investigating thermally tolerant reef corals in American Samoa. Here we will first cover spatial patterns of thermally resistant coral symbionts both locally in a back-reef pool system and across the Indo-Pacific. Then we will turn to experimental evidence of elevated thermal tolerance associated with both hosting such symbionts, and acclimatization to high-temperature habitats. Finally we will turn to whole-transcriptome expression data highlighting the apparent mechanism behind this acclimatization - front-loading of stress mitigating genes.

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Oceanography, Mānoa Campus

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