Publications by authors named "Alexandra M Tyers"
The African turquoise killifish is an emerging vertebrate model organism with great potential for aging research due to its naturally short lifespan. Thus far, turquoise killifish aging 'omic' studies have examined a single organ, single sex and/or evaluated samples from non-reference strains. Here, we describe a resource dataset of ribosomal RNA-depleted RNA-seq libraries generated from the brain, heart, muscle, and spleen from both sexes, as well as young and old animals, in the reference GRZ turquoise killifish strain.
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- - Epigenetic variation can influence gene expression and lead to differences in traits among populations adapting to different environments, specifically in the early stages of speciation.
- - The research examines the DNA methylome changes in two morphologically and ecologically distinct ecomorphs of Astatotilapia calliptera in Africa's Lake Masoko, which evolved about 1,000 years ago, despite no fixed genetic differences.
- - Findings show extensive differences in methylation patterns related to critical biological functions, supporting the idea that epigenetics plays a role in early vertebrate speciation, with some traits being inherited across generations.
Article Synopsis
- Epigenetic variation influences gene expression and can be passed down through generations, but its role in natural adaptive changes is not well understood.
- The research focuses on Lake Malawi cichlid fishes, showcasing significant phenotypic diversity despite minor genetic differences, making them an ideal subject for studying how epigenomics contributes to adaptation.
- The study finds notable differences in DNA methylation patterns between species, particularly in genes related to energy use and metabolism, highlighting a connection between diet and epigenetic changes, along with shared developmental gene patterns across tissues.
Balancing selection is important for the maintenance of polymorphism as it can prevent either fixation of one morph through directional selection or genetic drift, or speciation by disruptive selection. Polychromatism, the presence of multiple genetically determined colour phenotypes, can be maintained if the fitness of alternative morphs depends on the relative frequency in a population. In aggressive species, negative frequency-dependent antagonism can prevent an increase in the frequency of rare morphs as they would only benefit from increased fitness while they are rare.
View Article and Find Full Text PDFWhether freshwater fish colonize remote islands following tectonic or transoceanic dispersal remains an evolutionary puzzle. Integrating dating of known tectonic events with phylogenomics and current species distribution, we find that killifish species distribution is not explained by species dispersal by tectonic drift only. Investigating the colonization of a nonannual killifish (golden panchax, Pachypanchax playfairii) on the Seychelle islands, we found genetic support for transoceanic dispersal and experimentally discovered an adaptation to complete tolerance to seawater.
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- From the 1950s, East Africa has implemented aquaculture and fisheries programs focused on introduced species, though documentation in Tanzania has been lacking.
- A study conducted between 2011 and 2017 identified tilapia species across 123 locations, revealing 14 native taxa and three species, including one exotic (blue-spotted tilapia) that have expanded their range.
- Habitat modeling suggests that suitable conditions for these introduced species will persist and possibly expand due to changing climate projections, aiding in biodiversity management and informing future policies on aquaculture.
The hundreds of cichlid fish species in Lake Malawi constitute the most extensive recent vertebrate adaptive radiation. Here we characterize its genomic diversity by sequencing 134 individuals covering 73 species across all major lineages. The average sequence divergence between species pairs is only 0.
View Article and Find Full Text PDFThe genomic causes and effects of divergent ecological selection during speciation are still poorly understood. Here we report the discovery and detailed characterization of early-stage adaptive divergence of two cichlid fish ecomorphs in a small (700 meters in diameter) isolated crater lake in Tanzania. The ecomorphs differ in depth preference, male breeding color, body shape, diet, and trophic morphology.
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