bioRxiv Science⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/2021.10.09.463756

Polygenic sex determination produces modular sex polymorphism in an African cichlid fish

Moore, E. C.·Ciccotto, P. J.·Peterson, E. N.·Lamm, M. S.·Albertson, R. C.·Roberts, R. B.
View original source ↗Export metadata ↓

Abstract

For many vertebrates, a single genetic locus initiates a cascade of developmental sex differences in the gonad and throughout the organism, resulting in adults with two, phenotypically distinct sexes. Species with polygenic sex determination (PSD) have multiple interacting sex determination alleles segregating within a single species, allowing for more than two genotypic sexes, and scenarios where sex genotype at a given locus can be decoupled from gonadal sex. Here we investigate the effects of PSD on secondary sexual characteristics in the cichlid fish Metriaclima mbenjii, where one female (W) and one male (Y) sex determination allele interact to produce siblings with four possible sex classes: ZZXX females, ZWXX females, ZWXY females, and ZZXY males. We find that PSD in M. mbenjii produces an interplay of sex-linkage and sex-limitation resulting in modular variation in morphological and behavioral traits. Further, the evolution or introgression of a novel sex determiner creates additional axes of phenotypic variation for varied traits, including genital morphology, craniofacial morphology, gastrointestinal morphology, and home tank behaviors. In contrast to single-locus sex determination, which broadly results in sexual dimorphism, polygenic sex determination can induce higher-order sexual polymorphism. The modularity of secondary sexual characteristics produced by PSD provides novel context for understanding the evolutionary causes and consequences of maintenance, gain, or loss of sex determination alleles in populations. Significance StatementSex differences in traits can occur when those traits are modified by genetic factors inherited on sex chromosomes. We investigated how sex differences emerge in a species with more than one set of sex chromosomes, measuring a variety of morphological, physiological, and behavioral traits. Rather than exhibiting sexual dimorphism associated with primary sex, the species has higher-order sexual polymorphism in secondary sexual characteristics, or more than two phenotypic sexes. Variation in secondary sexual characteristics is modular, involving the interplay of sex-linked and sex-limited traits. Our findings provide novel implications for how sex determination systems and whole-organism fitness traits co-evolve, including that significant creation or loss of variation in diverse traits can occur during transitions among sex chromosome systems.

Source connections

Explore related subjects

evolutionary biologyPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Moore, E. C., Ciccotto, P. J., Peterson, E. N., Lamm, M. S., Albertson, R. C., Roberts, R. B.. 2021-10-09. Polygenic sex determination produces modular sex polymorphism in an African cichlid fish. https://doi.org/10.1101/2021.10.09.463756

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

Geometry of antigenic evolution improves influenza vaccine selection

Anticipating antigenic evolution is essential for selecting effective seasonal influenza A/H3N2 vaccine strains. To this end, we integrated hemagglutination-inhibition and neutralization titers spanning 2002 to 2025 into a unified Bayesian antigenic map. The map resolves twelve antigenic clusters advancing in discrete steps, with several clusters co-circulating in most seasons. In 15 of 21 seasons, the WHO-recommended vaccine belonged to an earlier cluster than the dominant circulating cluster. The direction of each vaccine update relative to recent viral drift predicted vaccine effectiveness one season ahead in out-of-sample forecasts. Antigenic distance, the conventional measure of vaccine-virus match, was weakly associated with effectiveness until update direction was accounted for. Retrospectively ranking candidate strains by predicted effectiveness would have selected a strain predicted to outperform the WHO recommendation in every season, raising mean predicted effectiveness by 10 percentage points.

evolutionary biology↗
bioRxiv2026

Evolutionary replay of duplicate-gene retention across independent whole-genome duplications

Whole-genome duplications repeatedly expose ancestral gene lineages to the same broad evolutionary outcome-retention or loss of duplicated copies-but it remains unclear whether this history replays similarly across evolutionary scales. We placed duplicate retention in shared hierarchical orthologous-group coordinates and compared percentile ranks defined within each event-wide mapped universe. Three independent angiosperm whole-genome duplications showed reproducible replay (global rank effect T-replay = 0.210, bootstrap 95% confidence interval 0.172-0.248; permutation P = 1/100,001). A plant reference-panel score specified before target outcomes were examined predicted retention after the Apple/Pear duplication ({rho} = 0.169, n = 373). Deep transfer was heterogeneous: the teleost-genome-duplication estimate was positive but unresolved ({rho} = 0.107, n = 151, 95% confidence interval -0.050 to 0.260), whereas transfer to the ancient budding-yeast whole-genome duplication (yeast WGD) was supported ({rho} = 0.280, n = 186). Independently reconstructed animal outcomes also replayed between teleost and Stylommatophora duplications (r = 0.226, n = 146, P = 0.00326), although the effect remained below a prespecified strong-effect threshold. A strict plant-animal comparison was limited to 25 deeply one-to-one lineages and was unresolved (r = 0.033, 95% confidence interval -0.303 to 0.340). Thus, ancestral gene-lineage identity contributes reproducibly to duplicate retention after independent whole-genome duplications, but replay is structured by evolutionary lineage and modified by event-specific history rather than governed by one universal gene-fate ranking.

evolutionary biology↗
bioRxiv2026

A Hymenoptera-restricted gene mediating ant castes co-opts deeply conserved machinery to control organ size

Lineage-specific genes are widespread and have been implicated as phenotypic innovation inducers, but how they acquire complex developmental functions remains poorly understood. Ant queens and workers develop dramatically different organ sizes from identical genomes under juvenile hormone (JH) control, yet the molecular effectors translating JH signalling into caste-specific organ growth remain unknown. Here we identify torch, a Hymenoptera-restricted gene, as the most consistently gyne-biased and JH-responsive gene across 68 ant species. Knockdown of torch in virgin queens of Monomorium pharaonis produces a worker-like, multi-organ growth-restricted phenotype. Mechanistically, torch harbours an E-box-like motif activated by the JH receptor Gce-Tai and acts as a GA-repeat-binding transcription factor that regulates Hippo signalling, the deeply conserved organ-size control pathway in animals. Expressing torch heterologously in mice and a growth-restricted Drosophila background shows that the gene retained its general growth-promoting activity across more than 700 million years of animal evolution in lineages that lack the gene, establishing that its function is mediated through conserved rather than ant-specific machinery. A lineage-specific gene can therefore acquire complex morphogenetic function by co-opting ancient organ-size circuitry, providing a general route by which novel genes can drive phenotypic innovation.

evolutionary biology↗