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ABSTRACT Cave‐dwelling animals thrive in isolated caves despite the pressures of darkness, starvation, and reduced oxygen. Prior work revealed thatAstyanaxcave‐dwelling morphs derived from different cave localities express significantly higher levels of blood hemoglobin compared to surface‐dwelling fish. Interestingly, this elevation is maintained in different populations of cavefish, despite captive rearing in normal oxygen conditions. We capitalized on the consistent response of elevated hemoglobin in captive cavefish, which were derived from geographically distinct regions, to determine if this elevation is underpinned by expression of the sameHbgenes. Blood hemoglobin proteins are encoded by a large family ofhemoglobin(Hb) gene family members, which demonstrate coordinated expression patterns, subject to various organismal (e.g., period of life history) and environmental influences (e.g., oxygen availability). Surprisingly, we found that geographically distinct populations showed mostly divergent patterns ofHbgene expression. Cavefish from two cave localities, Pachón and Tinaja, have a more recent shared origin, and show more similarHbexpression patterns as adults. However, during embryonic phases, Pachón and Tinaja show significant variability in timing of peak expression ofHbfamily members. In sum, the transcriptomic underpinnings ofHbgene expression represents a complex composite of shared and divergent expression patterns across three captive cavefish populations. We conclude that these differential patterns are likely influenced by life history, and the unique cave conditions in which these animals evolved.
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Transcriptomic signatures of temperature adaptation in the eastern oyster Crassostrea virginica
Abstract The large geographic distribution of the eastern oyster,Crassostrea virginica,makes it an ideal species to test how populations have adapted to latitudinal gradients in temperature. Despite inhabiting distinct thermal regimes, populations ofC. virginicanear the species’ southern and northern geographic range show no population differences in their physiological response to temperature. In this study, we used comparative transcriptomics to understand how oysters from either end of the species’ range maintain enantiostasis across three acclimation temperatures (10, 20, and 30°C). With this approach, we identified genes that were differentially expressed in response to temperature between individuals ofC. virginicacollected from New Brunswick, Canada and Louisiana, USA. We observed a core set of genes whose expression responded to temperature in both populations, but also an even larger set of genes with expression patterns that were unique to each population. Intriguingly, the genes with population‐specific responses to temperature had elevatedFSTand Ka/Ks ratios compared to the genome‐wide average. In contrast, genes showing only a response to temperature were found to only have elevatedFSTvalues suggesting that divergentFSTmay be due to selection on linked regulatory regions rather than positive selection on protein coding regions. Taken together, our results suggest that, despite coarse‐scale physiological similarities, natural selection has shaped divergent gene expression responses to temperature in geographically separated populations of this broadly eurythermal marine invertebrate.
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- Award ID(s):
- 1737170
- PAR ID:
- 10446370
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Journal of Evolutionary Biology
- Volume:
- 34
- Issue:
- 8
- ISSN:
- 1010-061X
- Format(s):
- Medium: X Size: p. 1212-1224
- Size(s):
- p. 1212-1224
- Sponsoring Org:
- National Science Foundation
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