Biology subjects

Everson, K. M.

Publications and source records attributed to Everson, K. M..

3 recordsLinked to original sources

bioRxiv2023

Not one, but multiple radiations underlie the biodiversity of Madagascar's endangered lemurs

Lemurs are often cited as an example of adaptive radiation. Since colonizing Madagascar, more than 100 extant lemur species have evolved to fill a variety of ecological niches on the island. However, recent work suggests that lemurs do not exhibit one of the hallmarks of other adaptive radiations: explosive speciation rates that decline over time. Thus, characterizing the tempo and mode of evolution in lemurs can help us understand alternative ways that hyperdiverse clades arise over time, which might differ from traditional models. We explore the evolution of lemurs using a phylogenomic dataset with broad taxonomic sampling that includes the lemurs sister group, the lorisiforms of Asia and continental Africa. Our analyses reveal multiple bursts of diversification (without subsequent declines) that explain much of todays lemur diversity. We also find higher rates of speciation in Madagascars lemurs compared to lorisiforms, and we demonstrate that the lemur clades with exceptionally high diversification rates have higher rates of genomic introgression. This suggests that hybridization in these primates is not an evolutionary dead-end, but a driving force for diversification. Considering the conservation crisis affecting strepsirrhine primates, with approximately 95% of species being threatened with extinction, this phylogenomic study offers a new perspective for explaining Madagascars exceptional primate diversity and reveals patterns of speciation, extinction, and gene flow that will help inform future conservation decisions.

evolutionary biology↗

bioRxiv2023

Lemur gut microeukaryotic community variation is not associated with host phylogeny, diet, or habitat

Gut prokaryotic (GP) community variation is often associated with host evolutionary and ecological variables; whether these factors drive variation in other gut taxa remains largely untested. We present a one-to-one comparison of GP (16S rRNA metabarcoding) and microeukaryotic (GME) (18S rRNA metabarcoding) community patterning among 12 species of lemurs. Lemurs were sampled from dry forests and rainforests of southeastern Madagascar and display a range of phylogenetic and ecological diversity. We found that while lemur GPs vary with host taxonomy, diet, and habitat, GMEs have no association with these factors. As a mechanism, we suggest purifying selection purges microbes with negative and commensal associations, while positive selection promotes the persistence of beneficial microbes. It is therefore likely that a greater proportion of GMEs comprise taxa with commensal, transient, and parasitic symbioses compared with GPs, many of which are mutualists. Our study reveals different microbial taxa are shaped by unique selective pressures.

evolutionary biology↗

bioRxiv2023

Whole Genomes Reveal Evolutionary Relationships and Mechanisms Underlying Gene-Tree Discordance in Neodiprion Sawflies

AO_SCPLOWBSTRACTC_SCPLOWRapidly evolving taxa are excellent models for understanding the mechanisms that give rise to biodiversity. However, developing an accurate historical framework for comparative analysis of such lineages remains a challenge due to ubiquitous incomplete lineage sorting and introgression. Here, we use a whole-genome alignment, multiple locus-sampling strategies, and locus-based and SNP-based species-tree methods to infer a species tree for eastern North American Neodiprion species, a clade of pine-feeding sawflies (Order: Hymenopteran; Family: Diprionidae). We recovered a well-supported species tree that--except for three uncertain relationships--is robust to different strategies for analyzing whole-genome data. Despite this consistency, underlying gene-tree discordance is high. To understand this discordance, we use multiple regression to model topological discordance as a function of several genomic features. We find that gene-tree discordance tends to be higher in regions of the genome that may be more prone to gene-tree estimation error, as indicated by a lower density of parsimony-informative sites, a higher density of genes, a higher average pairwise genetic distance, and gene trees with lower average bootstrap support. Also, contrary to the expectation that discordance via incomplete lineage sorting is reduced in low-recombination regions of the genome, we find a negative correlation between recombination rate and topological discordance. We offer potential explanations for this pattern and hypothesize that it may be unique to lineages that have diverged with gene flow. Our analysis also reveals an unexpected discordance hotspot on Chromosome 1, which contains several genes potentially involved in mitochondrial-nuclear interactions and produces a gene-tree that resembles a highly discordant mitochondrial tree. Based on these observations, we hypothesize that our genome-wide scan for topological discordance has identified a nuclear locus involved in a mito-nuclear incompatibility. Together, these results demonstrate how phylogenomic analysis coupled with high-quality, annotated genomes can generate novel hypotheses about the mechanisms that drive divergence and produce variable genealogical histories across genomes.

evolutionary biology↗