Biology subjects

Mavengere, H.

Publications and source records attributed to Mavengere, H..

3 recordsLinked to original sources

bioRxiv2021

15 years of introgression studies: quantifying gene flow across Eukaryotes

With the rise of affordable next generation sequencing technology, introgression -- or the exchange of genetic materials between taxa -- is widely perceived to be a ubiquitous phenomenon in nature. Although this claim is supported by several keystone studies, no thorough assessment on the frequency of introgression in nature has been performed to date. In this manuscript, we aim to address this knowledge gap by providing a meta-analysis of the most comprehensive survey of introgression studies in Eukaryotes to date (724 papers with claims of introgression). We first examined the evidence given to support introgression, and if/how the lines of evidence have changed across time. We then collated a single statistic, Pattersons D, that quantifies the strength of introgression across 123 studies to further assess how taxonomic group, divergence time, and aspects of life history influence introgression. We find three main results. Studies on introgression are much more frequent in plants and mammals than any other taxonomic group. The study of introgression has shifted from a largely qualitative assessment of whether introgression happens, to a focus on when and how much introgression has occurred across taxa. The most often used introgression statistic, Pattersons D, shows several intriguing patterns suggesting introgression reports may be biased by both differences in reporting criteria and sequencing technology, but may also differ across taxonomic systems and throughout the process of speciation. Together, these results suggest the need for a unified approach to quantifying introgression in natural communities, and highlight important areas of future research that can be better assessed once this unified approach is met.

evolutionary biology↗

bioRxiv2020

Paracoccidioides genomes reflect high levels of species divergence and little interspecific gene flow

The fungus Paracoccidioides spp. is a prevalent human pathogen endemic to South America. The genus is composed of five species. In this report, we use 37 whole genome sequences to study the allocation of genetic variation in Paracoccidioides. We tested three genome-wide predictions of advanced speciation, namely, that all species should be reciprocally monophyletic, that species pairs should be highly differentiated along the whole genome, and that there should be low rates of interspecific gene exchange. We find support for these three hypotheses. Species pairs with older divergences show no evidence of gene exchange, while more recently diverged species pairs show evidence of modest rates of introgression. Our results indicate that as divergence progresses, species boundaries become less porous among Paracoccidioides species. Our results suggest that species in Paracoccidioides are at different stages along the divergence continuum. IMPORTANCEParacoccidioides is the causal agent of the most frequent systemic mycosis in Latin America. Most of the inference of the evolutionary history of Paracoccidioides has used only a handful of molecular markers. In this report, we evaluate the extent of genome divergence among Paracoccidioides species and study the possibility of interspecific gene exchange. We find that all species are highly differentiated. We also find that the amount of gene flow between species is low and in some cases even completely absent in spite of geographic overlap. Our study constitutes a systematic effort to identify species boundaries in fungal pathogens, and determine the extent of gene exchange among fungal species.

microbiology↗

bioRxiv2020

Environmental and genetic contributions to imperfect wMel-like Wolbachia transmission and frequency variation

Maternally transmitted Wolbachia bacteria infect about half of all insect species. They usually show imperfect maternal transmission and often produce cytoplasmic incompatibility (CI). Irrespective of CI, Wolbachia frequencies tend to increase when rare only if they benefit host fitness. Several Wolbachia, including wMel that infects Drosophila melanogaster cause weak or no CI and persist at intermediate frequencies. On the island of Sao Tome off West Africa, the frequencies of wMel-like Wolbachia infecting D. yakuba (wYak) and D. santomea (wSan) fluctuate, and the contributions of imperfect maternal transmission, fitness effects, and CI to these fluctuations are unknown. We demonstrate spatial variation in wYak frequency and transmission on Sao Tome. Concurrent field estimates of imperfect maternal transmission do not predict spatial variation in wYak frequencies, which are highest at high altitudes where maternal transmission is the most imperfect. Genomic and genetic analyses provide little support for D. yakuba effects on wYak transmission. Instead, rearing at cool temperatures reduces wYak titer and increases imperfect transmission to levels observed on Sao Tome. Using mathematical models of Wolbachia frequency dynamics and equilibria, we infer temporally variable imperfect transmission or spatially variable effects on host fitness and reproduction are required to explain wYak frequencies. In contrast, spatially stable wSan frequencies are plausibly explained by imperfect transmission, modest fitness effects, and weak CI. Our results provide insight into causes of wMel-like frequency variation in divergent hosts. Understanding this variation is crucial to explain Wolbachia spread and to improve wMel biocontrol of human disease in transinfected mosquito systems.

evolutionary biology↗