Biology subjects

Fitzgerald, L. M.

Publications and source records attributed to Fitzgerald, L. M..

3 recordsLinked to original sources

bioRxiv2025

Genetic basis of the evolution of vertical bars in clownfishes

Clownfish exhibit striking color patterns, characterized primarily by the presence of zero to three vertical white bars, along with three main colors: orange, white, and black. The common ancestor of clownfish likely possessed three vertical bars, with several instances of gains and losses occurring throughout clownfish evolutionary history over the past 10 million years. However, the evolutionary genomic mechanisms underlying the gain or loss of vertical bars remain unknown. In this study, we tested whether vertical bar transitions across the clownfish phylogeny were associated with changes in non-synonymous to synonymous substitution rates (dN/dS values). Our analyses identified pigmentation-related genes that underwent changes in selective pressure, including gch2, oca2, and vps11, which are linked to melanophores, iridophores, and visual function. Additionally, pmel, a key melanogenesis gene, was found under positive selection, suggesting its role in shaping bar patterning. These results provide new insights into the genomic basis of coloration in clownfish, highlighting how selection and genetic variation influence phenotypic evolution.

evolutionary biology↗

bioRxiv2024

Specialization into Host Sea Anemones Impacted Clownfish Demographic Responses to Pleistocene Sea Level Changes

Fluctuating sea levels during the Pleistocene led to habitat loss and fragmentation, impacting the evolutionary trajectories of reef fishes. Species with specialized ecological requirements or habitat preferences, like clownfishes (Amphiprioninae), may have been particularly vulnerable due to their intricate dependence on sea anemones. The diverse host specializations within this group likely contributed distinct responses to sea-level fluctuations, differentially shaping their recent evolutionary histories. Leveraging a comprehensive genomic dataset, we reveal demographic patterns and connectivity dynamics across multiple populations of ten clownfish species under different host specializations. Host-generalist species demonstrated strong resilience to habitat perturbations, while those specialized on single hosts suffered dramatic bottlenecks linked to sea-level fluctuations. Spatial analyses revealed the significant role of oceanic currents in shaping clownfish genetic diversity landscapes. Dispersal barriers were driven by environmental variables, with the Coral Triangle emerging as a hub of genetic diversity. Our results reveal how clownfish associative behavior influences their population dynamics, holding major implications for their conservation such as the need to consider their mutualism with sea anemones, particularly on host-specialists, to ensure their survival in the face of climate threats. These findings extend broader principles of conservation, improving our understanding of species responses to ecological constraints and environmental changes over evolutionary timescales.

genomics↗

bioRxiv2024

Host-use Drives Convergent Evolution in Clownfish and Disentangles the Mystery of an Iconic Adaptive Radiation

Clownfishes (Amphiprioninae) are a fascinating example of marine radiation. From a central Pacific ancestor, they quickly colonized the coral reefs of the Indo-Pacific and diversified independently on each side of the Indo-Australian Archipelago. Their association with venomous sea anemones is often thought to be the key innovation that enabled the clownfish radiation. However, this intuition has little empirical or theoretical support given our current knowledge of the clade. To date, no ecological variable has been identified that can explain clownfish niche partitioning, phenotypic evolution, species co-occurrence, and thus, the adaptive radiation of the group. Our synthetic work solves this long-standing mystery by testing the influence of sea anemone host use on phenotypic divergence. We provide the first major revision to the known clownfish-sea anemone host associations in over 30 years, accounting for host associations in a biologically relevant way. We gathered whole-genome data for all 28 clownfish species and reconstructed a fully supported species tree for the Amphiprioninae. Integrating this new data into comparative phylogenomic approaches, we demonstrate for the first time, that the host sea anemones are the drivers of convergent evolution in clownfish color pattern and morphology. During the adaptive radiation of this group, clownfishes in different regions that associate with the same hosts have evolved the same phenotypes. Comparative genomics also reveals several genes under convergent positive selection linked to host specialisation events. Our results identify the sea anemone host as the key ecological variable that disentangles the entire adaptive radiation. As one of the most recognizable animals on the planet and an emerging model organism in the biological sciences, our findings bear on the interpretation of dozens of prior studies on clownfishes and will radically reshape research agendas for these iconic organisms.

evolutionary biology↗