Biology subjects

Betancur-R, R.

Publications and source records attributed to Betancur-R, R..

3 recordsLinked to original sources

bioRxiv2024

Ancient climate changes and relaxed selection shape cave colonisation in North American cavefishes

Extreme environments serve as natural laboratories for studying evolutionary processes, with caves offering replicated instances of independent colonisations. The timing, mode, and genetic underpinnings underlying cave-obligate organismal evolution remains enigmatic. We integrate phylogenomics, fossils, paleoclimatic modeling, and newly sequenced genomes to elucidate the evolutionary history and adaptive processes of cave colonisation in the study group, the North American Amblyopsidae fishes. Amblyopsid fishes present a unique system for investigating cave evolution, encompassing surface, facultative cave-dwelling, and cave-obligate (troglomorphic) species. Using 1,105 exon markers and total-evidence dating, we reconstructed a robust phylogeny that supports the nested position of eyed, facultative cave-dwelling species within blind cavefishes. We identified three independent cave colonisations, dated to the Early Miocene (18.5 Mya), Late Miocene (10.0 Mya), and Pliocene (3.0 Mya). Evolutionary model testing supported a climate-relict hypothesis, suggesting that global cooling trends since the Early-Middle Eocene may have influenced cave colonisation. Comparative genomic analyses of 487 candidate genes revealed both relaxed and intensified selection on troglomorphy-related loci. We found more loci under relaxed selection, supporting neutral mutation as a significant mechanism in cave-obligate evolution. Our findings provide empirical support for climate-driven cave colonisation and offer insights into the complex interplay of selective pressures in extreme environments.

evolutionary biology↗

bioRxiv2023

Phylogenomics reveals the deep ocean as an accelerator for evolutionary diversification in anglerfishes

Colonization of a novel habitat is often followed by radiation in the wake of ecological opportunity. Alternatively, some habitats should be inherently more constraining than others if the challenges of that environment have few evolutionary solutions. We examined the push-and-pull of these factors on evolution following habitat transitions, using anglerfishes (Lophiiformes) as a model. Deep-sea fishes are notoriously difficult to study, and poor sampling has limited progress thus far. Here we present a new phylogeny of anglerfishes with unprecedented taxonomic sampling (1,092 loci and 40% of species), combined with three-dimensional phenotypic data from museum specimens obtained with micro-CT scanning. We use these datasets to examine the tempo and mode of phenotypic and lineage diversification using phylogenetic comparative methods, comparing lineages in shallow and deep benthic versus bathypelagic habitats. Our results show that anglerfishes represent a surprising case where the bathypelagic lineage has greater taxonomic and phenotypic diversity than coastal benthic relatives. This defies expectations based on ecological principles since the bathypelagic zone is the most homogeneous habitat on Earth. Deep-sea anglerfishes experienced rapid lineage diversification concomitant with colonization of the bathypelagic zone from a continental slope ancestor. They display the highest body, skull and jaw shape disparity across lophiiforms. In contrast, reef-associated taxa show strong constraints on shape and low evolutionary rates, contradicting patterns suggested by other shallow marine fishes. We found that Lophiiformes as a whole evolved under an early burst model with subclades occupying distinct body shapes. We further discuss to what extent the bathypelagic clade is a secondary adaptive radiation, or if its diversity can be explained by non-adaptive processes.

evolutionary biology↗

bioRxiv2023

Conservation of affinity rather than sequence underlies a dynamic evolution of the motif-mediated p53/MDM2 interaction in teleosts

The transcription factor and cell cycle regulator p53 is marked for degradation by the ubiquitin ligase MDM2. The interaction between these two proteins is mediated by a conserved binding motif in the disordered p53 transactivation domain (p53TAD) and the folded SWIB domain in MDM2. The conserved motif in p53TAD from zebrafish displays a 20-fold weaker interaction with MDM2, compared to the interaction in human and chicken. To investigate this apparent difference, we tracked the molecular evolution of the p53TAD/MDM2 interaction among ray- finned fishes (Actinopterygii), the largest vertebrate clade. Intriguingly, phylogenetic analyses, ancestral sequence reconstructions, and binding experiments showed that different loss-of- affinity changes in the canonical binding motif within p53TAD have occurred repeatedly and convergently in different fish lineages, resulting in relatively low extant affinities (KD = 0.5-5 M). However, for eleven different fish p53TAD/MDM2 interactions, non-conserved regions flanking the canonical motif increased the affinity 4 to 73-fold to be on par with the human interaction. Our findings suggest that compensating changes at conserved and non-conserved positions within the motif, as well as in flanking regions of low conservation, underlie a stabilizing selection of "functional affinity" in the p53TAD/MDM2 interaction. Such interplay complicates bioinformatic prediction of binding and call for experimental validation. Motif- mediated protein-protein interactions involving short binding motifs and folded interaction domains are very common across multicellular life. It is likely that evolution of affinity in motif- mediated interactions often involves an interplay between specific interactions made by conserved motif residues and non-specific interactions by non-conserved disordered regions.

molecular biology↗