Biology subjects

Barker, M. S.

Publications and source records attributed to Barker, M. S..

3 recordsLinked to original sources

bioRxiv2018

Polyploid plants have faster rates of multivariate climatic niche evolution than their diploid relatives

Whole genome duplication is an important evolutionary process in plants. In contrast to other speciation mechanisms, polyploid species begin with substantial postzygotic reproductive isolation from progenitors while being sympatric with one or both. These nascent polyploid species often go extinct due to ecological and evolutionary genetic obstacles. Interestingly, polyploid species appear to quickly occupy different geographic distributions and ecological niches than their diploid progenitors. Using biogeographic data from polyploid and diploid species representing 49 genera of vascular plants, we tested whether climatic niches of polyploid species evolve faster than their diploid relatives. We found polyploid species often have less climatic overlap than expected with diploid progenitors. Consistent with this pattern, we estimated that the climatic niches of polyploid plants consistently evolved faster than the niches of diploid relatives. Our results indicate ecological niche differentiation is important for polyploid establishment, and suggest ecological differentiation is important for speciation processes more widely.\n\nStatement of AuthorshipAB and MS conceived of project, AB and NA generated the dataset, AB and HM performed analyses, AB and MS cowrote manuscript.\n\nData Accessibility StatementUpon acceptance all necessary R scripts, data, and files supporting the results will be archived on FigShare with the data DOI included at the end of the article.

evolutionary biology↗

bioRxiv2018

Multiple large-scale gene and genome duplications during the evolution of hexapods

Polyploidy or whole genome duplication (WGD) is a major contributor to genome evolution and diversity. Although polyploidy is recognized as an important component of plant evolution, it is generally considered to play a relatively minor role in animal evolution. Ancient polyploidy is found in the ancestry of some animals, especially fishes, but there is little evidence for ancient WGDs in other metazoan lineages. Here we use recently published transcriptomes and genomes from more than 150 species across the insect phylogeny to investigate whether ancient WGDs occurred during the evolution of Hexapoda, the most diverse clade of animals. Using gene age distributions and phylogenomics, we found evidence for 18 ancient WGDs and six other large-scale bursts of gene duplication during insect evolution. These bursts of gene duplication occurred in the history of lineages such as the Lepidoptera, Trichoptera, and Odonata. To further corroborate the nature of these duplications, we evaluated the pattern of gene retention from putative WGDs observed in the gene age distributions. We found a relatively strong signal of convergent gene retention across many of the putative insect WGDs. Considering the phylogenetic breadth and depth of the insect phylogeny, this observation is consistent with polyploidy as we expect dosage-balance to drive the parallel retention of genes. Together with recent research on plant evolution, our hexapod results suggest that genome duplications contributed to the evolution of two of the most diverse lineages of eukaryotes on Earth.

evolutionary biology↗

bioRxiv2017

Genomic inferences of domestication events are corroborated by written records in Brassica rapa

Demographic modeling is often used with population genomic data to infer the relationships and ages among populations. However, relatively few analyses are able to validate these inferences with independent data. Here, we leverage written records that describe distinct Brassica rapa crops to corroborate demographic models of domestication. Brassica rapa crops are renowned for their outstanding morphological diversity, but the relationships and order of domestication remains unclear. We generated genome-wide SNPs from 126 accessions collected globally using high-throughput transcriptome data. Analyses of more than 31,000 SNPs across the B. rapa genome revealed evidence for five distinct genetic groups and supported a European-Central Asian origin of B. rapa crops. Our results supported the traditionally recognized South Asian and East Asian B. rapa groups with evidence that pak choi, Chinese cabbage, and yellow sarson are likely monophyletic groups. In contrast, the oil-type B. rapa subsp. oleifera and brown sarson were polyphyletic. We also found no evidence to support the contention that rapini is the wild type or the earliest domesticated subspecies of B. rapa. Demographic analyses suggested that B. rapa was introduced to Asia 2400-4100 years ago, and that Chinese cabbage originated 1200-2100 years ago via admixture of pak choi and European-Central Asian B. rapa. We also inferred significantly different levels of founder effect among the B. rapa subspecies. Written records from antiquity that document these crops are consistent with these inferences. The concordance between our age estimates of domestication events with historical records provides unique support for our demographic inferences.

genetics↗