Dataset Information

Morphology and life history divergence in cave and surface populations of Gammarus lacustris (L.).

ABSTRACT: Cave animals provide a unique opportunity to study contrasts in phenotype and life history in strikingly different environments when compared to surface populations, potentially related to natural selection. As such, we compared a permanent cave-living Gammarus lacustris (L.) population with two lake-resident surface populations analyzing morphology (eye- and antennal characters) and life-history (size at maturity, fecundity and egg-size). A part of the cytochrome c oxidase subunit I gene in the mitochondrion (COI) was analyzed to contrast genetic relationship of populations and was compared to sequences in GenBank to assess phylogeography and colonization scenarios. In the cave, a longer life cycle was implied, while surface populations seemed to have a shorter life cycle. Egg size, and size at maturity for both sexes, were larger in the cave than in surface populations, while fecundity was lower in the cave than in surface populations. The cave population had longer first- and second antennae with more articles, longer first- and second peduncles, and fewer ommatidia than surface populations. The cold low-productive cave environment may facilitate different phenotypic and life-history traits than in the warmer and more productive surface lake environments. The trait divergences among cave and surface populations resembles other cave-surface organism comparisons and may support a hypothesis of selection on sensory traits. The cave and Lake Ulvenvann populations grouped together with a sequence from Slovenia (comprising one genetic cluster), while Lake Lille Lauarvann grouped with a sequence from Ukraine (comprising another cluster), which are already recognized phylogenetic clusters. One evolutionary scenario is that the cave and surface populations were colonized postglacially around 9 000-10 000 years ago. We evaluate that an alternative scenario is that the cave was colonized during an interstadial during the last glaciation or earlier during the warm period before onset of the last glaciation.

SUBMITTER: Ostbye K

PROVIDER: S-EPMC6201897 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Morphology and life history divergence in cave and surface populations of Gammarus lacustris (L.).

Østbye Kjartan K Østbye Eivind E Lien Anne May AM Lee Laura R LR Lauritzen Stein-Erik SE Carlini David B DB

PloS one 20181025 10

Cave animals provide a unique opportunity to study contrasts in phenotype and life history in strikingly different environments when compared to surface populations, potentially related to natural selection. As such, we compared a permanent cave-living Gammarus lacustris (L.) population with two lake-resident surface populations analyzing morphology (eye- and antennal characters) and life-history (size at maturity, fecundity and egg-size). A part of the cytochrome c oxidase subunit I gene in the ...[more]

PMID: 30359400

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Project description:Gammarus minus, a freshwater amphipod living in the cave and surface streams in the eastern USA, is an excellent model for investigating evolutionary adaptation to the subterranean environment. RNA-Seq was conducted on one pair of morphologically distinct sister populations inhabiting surface and cave habitats to identify genes that were differentially expressed in the two populations, as well as to compare levels and patterns of genetic variation within and between populations. Of the 104,630 transcripts identified in the transcriptome assembly, 57% had higher average levels of expression in the cave population. After Benjamini-Hochberg correction for multiple tests, 1517 and 551 transcripts were significantly upregulated or downregulated, respectively, in the cave population, indicating an almost three-fold enrichment of cave-upregulated genes. The average level of nucleotide diversity across all transcripts was significantly lower in the cave population. Within the cave population, where the average nucleotide diversity of cave-downregulated transcripts was 75% that of the cave-upregulated transcripts, a highly significant difference, whereas within the spring population the nucleotide diversities of cave-downregulated and cave-upregulated transcripts was virtually identical. Three lines of evidence suggest that the reduced variation in cave downregulated transcripts is due to positive selection in the cave population: 1) the average neutrality index of cave-downregulated genes was < 1, consistent with positive selection, and significantly less than that of cave-upregulated genes; 2) Tajima's D was positively correlated with the cave:surface expression ratio, and 3) cave-downregulated transcripts were significantly more likely to be highly diverged from their surface homologs than cave-upregulated transcripts. Five transcripts had fixed premature termination codons in the cave population. The expression patterns and sequence variation in one such transcript, encoding the DNA repair protein photolyase, were examined in more detail and provide the first evidence for the relaxation of functional constraint in this light-dependent protein in a subterranean population.

Dataset Information

Morphology and life history divergence in cave and surface populations of Gammarus lacustris (L.).

Publications

Morphology and life history divergence in cave and surface populations of Gammarus lacustris (L.).

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