Genomic signatures of positive selection and relaxed selective constraints associated with convergent dietary specialisation
- 1Universitat of Barcelona
Abstract
Island radiations provide ideal frameworks for studying the molecular basis of convergent evolution. The rapid diversification of Dysdera spiders in Canary Islands provides a striking example, with repeated dietary shifts towards specialisation on woodlice, accompanied by morphological, metabolic, and behavioural modifications that facilitate the exploitation of this heavy-metal-rich prey. Here, we investigate two independent events of dietary specialisation on different islands. By analysing six high-quality genome-assemblies, including three newly generated in this study, we investigate the genomic signals of positive selection and relaxed selection in protein-coding genes, upstream regulatory regions, and gene family turnover rates. We detected signatures of positive selection associated with the two specialists, accompanied by a twofold increase in gene loss rates relative to generalist ancestors. Notably, positive selection targeted a smaller, functionally coherent set of genes, potentially involved in detoxification likely through heavy metal excretion. In contrast, relaxation of selection affected a broader set of genes associated with functions that may have become dispensable under the new dietary regime. Furthermore, we found contractions in gene families associated with vesicular transport, potentially reflecting a reduced reliance on vesicle-mediated metal accumulation. Overall, our findings suggest that similar ecological pressures can drive parallel, yet non-identical, adaptive and non-adaptive responses, pointing to partially predictable evolutionary trajectories in an island radiation.
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BibTeX
@misc{olivemuniz2026genomic,
title = {{Genomic signatures of positive selection and relaxed selective constraints associated with convergent dietary specialisation}},
author = {M. Olive-Muniz and V. A. Pisarenco and N. Macias-Hernandez and C. Frias-Lopez and M. A. Arnedo and A. Sanchez-Gracia and S. Guirao-Rico and J. Rozas},
howpublished = {bioRxiv},
year = {2026},
month = nov,
doi = {10.64898/2026.11.05.764531},
url = {https://www.biorxiv.org/content/10.64898/2026.11.05.764531v1},
note = {CC BY-NC},
}
RIS
TY - UNPB
TI - Genomic signatures of positive selection and relaxed selective constraints associated with convergent dietary specialisation
AU - M. Olive-Muniz
AU - V. A. Pisarenco
AU - N. Macias-Hernandez
AU - C. Frias-Lopez
AU - M. A. Arnedo
AU - A. Sanchez-Gracia
AU - S. Guirao-Rico
AU - J. Rozas
PY - 2026
DA - 2026/11/05
PB - bioRxiv
DO - 10.64898/2026.11.05.764531
UR - https://www.biorxiv.org/content/10.64898/2026.11.05.764531v1
AB - Island radiations provide ideal frameworks for studying the molecular basis of convergent evolution. The rapid diversification of Dysdera spiders in Canary Islands provides a striking example, with repeated dietary shifts towards specialisation on woodlice, accompanied by morphological, metabolic, and behavioural modifications that facilitate the exploitation of this heavy-metal-rich prey. Here, we investigate two independent events of dietary specialisation on different islands. By analysing six high-quality genome-assemblies, including three newly generated in this study, we investigate the genomic signals of positive selection and relaxed selection in protein-coding genes, upstream regulatory regions, and gene family turnover rates. We detected signatures of positive selection associated with the two specialists, accompanied by a twofold increase in gene loss rates relative to generalist ancestors. Notably, positive selection targeted a smaller, functionally coherent set of genes, potentially involved in detoxification likely through heavy metal excretion. In contrast, relaxation of selection affected a broader set of genes associated with functions that may have become dispensable under the new dietary regime. Furthermore, we found contractions in gene families associated with vesicular transport, potentially reflecting a reduced reliance on vesicle-mediated metal accumulation. Overall, our findings suggest that similar ecological pressures can drive parallel, yet non-identical, adaptive and non-adaptive responses, pointing to partially predictable evolutionary trajectories in an island radiation.
ER -