Biology subjects

Losos, J. B.

Publications and source records attributed to Losos, J. B..

4 recordsLinked to original sources

bioRxiv2024

Structural rearrangements and selection promote phenotypic evolution in Anolis lizards

The genomic characteristics of adaptively radiated groups could contribute to their high species number and ecological disparity, by increasing their evolutionary potential. Here, we explored the genomic features of Anolis lizards, focusing on three species with unique phenotypes: A. auratus, one of the species with the longest tail; A. frenatus, one of the largest species; and A. carolinensis, one of the species that inhabits the coldest environments. We assembled and annotated two new chromosome-level reference genomes for A. auratus and A. frenatus, and compared them with the available genomes of A. carolinensis and A. sagrei. We evaluated the presence of structural rearrangements, quantified the density of repeat elements, and identified signatures of positive selection in coding and regulatory regions. We detected substantial rearrangements in scaffolds 1, 2 and 3 of A. frenatus different from the other species, in which the rearrangement breakpoints corresponded to hotspots of developmental genes. Further, we detected an accumulation of repeats around key developmental genes in anoles and phrynosomatid outgroups. Finally, we detected signatures of positive selection on coding sequences and regulatory regions of genes relevant to development and physiology that could affect the unique phenotypes of the analyzed species. Our results suggest that anoles have genomic features associated with genes that affect organismal morphology and physiology. This could provide a genomic substrate that promoted phenotypic disparity in anoles, and contributed to their ability to adaptively radiate. Author SummaryAdaptive radiations are often characterized by high species richness and phenotypic differentiation. Besides the ecological context, the genetic features of organisms could also contribute to their ability to diversify. Anolis lizards are an adaptively radiated group that shows high phenotypic disparity in morphology and physiology. In this study, we explored the genome of four species within the Anolis radiation with distinctive phenotypes. We generated a high-quality chromosome-level reference genome for A. auratus and A. frenatus, and compared them with A. carolinensis and A. sagrei. We detected major structural rearrangements in A. frenatus, a high density of repeat elements around key developmental genes, and signatures of natural selection associated with genes functionally relevant for the analyzed species. Hence, the genomic characteristics of anoles were associated with their unique phenotypic diversity. We highlight the potential relevance of genomic features to influence the ability of groups of organisms to radiate adaptively.

evolutionary biology↗

bioRxiv2021

Chromosome-scale genome assembly of the brown anole (Anolis sagrei), a model species for evolution and ecology

Rapid technological improvements are democratizing access to high quality, chromosome-scale genome assemblies. No longer the domain of only the most highly studied model organisms, now non-traditional and emerging model species can be genome-enabled using a combination of sequencing technologies and assembly software. Consequently, old ideas built on sparse sampling across the tree of life have recently been amended in the face of genomic data drawn from a growing number of high-quality reference genomes. Arguably the most valuable are those long-studied species for which much is already known about their biology; what many term emerging model species. Here, we report a new, highly complete chromosome-scale genome assembly for the brown anole, Anolis sagrei - a lizard species widely studied across a variety of disciplines and for which a high-quality reference genome was long overdue.

genomics↗

bioRxiv2021

Conservation and convergence of genetic architecture in the adaptive radiation of Anolis lizards

The G matrix, which quantifies the genetic architecture of traits, is often viewed as an evolutionary constraint. However, G can evolve in response to selection and may also be viewed as a product of adaptive evolution. Convergent evolution of G in similar environments would suggest that G evolves adaptively, but it is difficult to disentangle such effects from phylogeny. Here, we use the adaptive radiation of Anolis lizards to ask whether convergence of G accompanies the repeated evolution of habitat specialists, or ecomorphs, across the Greater Antilles. We measured G in seven species representing three ecomorphs (trunk-crown, trunk- ground, and grass-bush). We found that the overall structure of G does not converge. Instead, the structure of G is well conserved and displays a phylogenetic signal consistent with Brownian motion. However, several elements of G showed signatures of convergence, indicating that some aspects of genetic architecture have been shaped by selection. Most notably, genetic correlations between limb traits and body traits were weaker in long-legged trunk-ground species, suggesting effects of recurrent selection on limb length. Our results demonstrate that common selection pressures may have subtle but consistent effects on the evolution of G, even as its overall structure remains conserved.

evolutionary biology↗

bioRxiv2017

Semicircular Canals In Anolis Lizards: Ecomorphological Convergence And Ecomorph Affinities Of Fossil Species

Anolis lizards are a model system for the study of adaptive radiation and convergent evolution. Greater Antillean anoles have repeatedly evolved six similar forms or ecomorphs: crown-giant, grass-bush, twig, trunk, trunk-crown, and trunk-ground. Members of each ecomorph category possess a specific set of morphological, ecological and behavioural characteristics which have been acquired convergently. Here we test whether the semicircular canal system - the organ of balance - is also convergent among ecomorphs, reflecting the shared sensory requirements of their ecological niches. As semicircular canal shape has been shown to reflect different locomotor strategies, we hypothesised that each Anolis ecomorph would have a unique canal morphology. Using 3D semilandmarks and geometric morphometrics, semicircular canal shape was characterised in 41 Anolis species from the Greater Antilles and the relationship between canal shape and ecomorph grouping, phylogenetic history, size, and perch characteristics was assessed. Further, canal morphology of modern species was used to predict the ecomorph affinity of five fossil anoles from the Miocene of the Dominican Republic. Our study recovered ecomorph as the single-most important covariate of canal morphology in modern taxa; although phylogenetic history and size also showed a small, yet significant correlation with shape. Surprisingly, perch characteristics were not found to be significant covariates of canal shape, even though they are important habitat variables. Using posterior probabilities, we found that the fossil anoles have different semicircular canals shapes to modern ecomorph groupings implying extinct anoles may have been interacting with their Miocene environment in different ways to modern Anolis species.

evolutionary biology↗