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Ecological niche divergence between extant and glacial land snail populations explained.

ABSTRACT: The presence of Last Glacial Maximum (LGM) biotic communities without modern counterparts is well known. It is particularly evident in central European fossil LGM land snails whose assemblages represent an odd mix of species that are currently limited to either xeric or wetland habitats. Here we document a genetically verified discovery of the modern calcareous wetland species Pupilla alpicola on Iceland, where it is limited to dry grasslands. This species also represents a common European LGM fossil, and its new records from Iceland help explain puzzling shifts of some glacial land snails of xeric grassland habitats to open wetlands today. Similarities between the climates of modern Iceland and LGM Eurasia suggest that this species did not become limited to wetlands in continental Europe until after the Late Pleistocene-Holocene climate transition. These results are a strong reminder that assumptions of ecological uniformity must be questioned and that the quality and robustness of palaeoecological reconstructions is dependent upon adequate knowledge of the full autecological range of species over time.

SUBMITTER: Horsak M

PROVIDER: S-EPMC8763904 | biostudies-literature | 2022 Jan

REPOSITORIES: biostudies-literature

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Ecological niche divergence between extant and glacial land snail populations explained.

Horsák Michal M Horsáková Veronika V Divíšek Jan J Nekola Jeffrey C JC

Scientific reports 20220117 1

The presence of Last Glacial Maximum (LGM) biotic communities without modern counterparts is well known. It is particularly evident in central European fossil LGM land snails whose assemblages represent an odd mix of species that are currently limited to either xeric or wetland habitats. Here we document a genetically verified discovery of the modern calcareous wetland species Pupilla alpicola on Iceland, where it is limited to dry grasslands. This species also represents a common European LGM f ...[more]

PMID: 35039536

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Project description:Background and aimsIn eastern Neotropical South America, the Cerrado, a large savanna vegetation, and the Atlantic Forest harbour high biodiversity levels, and their habitats are rather different from each other. The biomes have intrinsic evolutionary relationships, with high lineage exchange that can be attributed, in part, to a large contact zone between them. The genomic study of ecotypes, i.e. populations adapted to divergent habitats, can be a model to study the genomic signatures of ecological divergence. Here, we investigated two ecotypes of the tree Plathymenia reticulata, one from the Cerrado and the other from the Atlantic Forest, which have a hybrid zone in the ecotonal zone of Atlantic Forest-Cerrado.MethodsThe ecotypes were sampled in the two biomes and their ecotone. The evolutionary history of the divergence of the species was analysed with double-digest restriction site-associated DNA sequencing. The genetic structure and the genotypic composition of the hybrid zone were determined. Genotype-association analyses were performed, and the loci under putative selection and their functions were investigated.Key resultsHigh divergence between the two ecotypes was found, and only early-generation hybrids were found in the hybrid zone, suggesting a partial reproductive barrier. Ancient introgression between the Cerrado and Atlantic Forest was not detected. The soil and climate were associated with genetic divergence in Plathymenia ecotypes and outlier loci were found to be associated with the stress response, with stomatal and root development and with reproduction.ConclusionsThe high genomic, ecological and morphophysiological divergence between ecotypes, coupled with partial reproductive isolation, indicate that the ecotypes represent two species and should be managed as different evolutionary lineages. We advise that the forest species should be re-evaluated and restated as vulnerable. Our results provide insights into the genomic mechanisms underlying the diversification of species across savanna and forest habitats and the evolutionary forces acting in the species diversification in the Neotropics.

Project description:Background and aimsNiche divergence between polyploids and their lower ploidy progenitors is one of the primary mechanisms fostering polyploid establishment and adaptive divergence. However, within-species chromosomal and reproductive variability have usually been neglected in community ecology and biodiversity analyses even though they have been recognized to play a role in the adaptive diversification of lineages.MethodsWe used Paspalum intermedium, a grass species with diverging genetic systems (diploidy vs. autopolyploidy, allogamy vs. autogamy and sexuality vs. apomixis), to recognize the causality of biogeographic patterns, adaptation and ecological flexibility of cytotypes. Chromosome counts and flow cytometry were used to characterize within-species genetic systems diversity. Environmental niche modelling was used to evaluate intraspecific ecological attributes associated with environmental and climatic factors and to assess correlations among ploidy, reproductive modes and ecological conditions ruling species' population dynamics, range expansion, adaptation and evolutionary history.Key resultsTwo dominant cytotypes non-randomly distributed along local and regional geographical scales displayed niche differentiation, a directional shift in niche optima and signs of disruptive selection on ploidy-related ecological aptitudes for the exploitation of environmental resources. Ecologically specialized allogamous sexual diploids were found in northern areas associated with higher temperature, humidity and productivity, while generalist autogamous apomictic tetraploids occurred in southern areas, occupying colder and less productive environments. Four localities with a documented shift in ploidy and four mixed populations in a zone of ecological transition revealed an uneven replacement between cytotypes.ConclusionsPolyploidy and contrasting reproductive traits between cytotypes have promoted shifts in niche optima, and increased ecological tolerance and niche divergence. Ecologically specialized diploids maintain cytotype stability in core areas by displacing tetraploids, while broader ecological preferences and a shift from sexuality to apomixis favoured polyploid colonization in peripheral areas where diploids are displaced, and fostered the ecological opportunity for autotetraploids supporting range expansion to open southern habitats.

Dataset Information

Ecological niche divergence between extant and glacial land snail populations explained.

Publications

Ecological niche divergence between extant and glacial land snail populations explained.

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