{
  "id": 18584417,
  "title": "Genomic signatures of positive selection and relaxed selective constraints associated with convergent dietary specialisation",
  "url": "https://urgent.news/2026/11/06/genomic-signatures-of-positive-selection-and-relaxed-selective",
  "topic": "science",
  "section": "Science",
  "published": "2026-11-06T00:00:00.000Z",
  "source": {
    "name": "bioRxiv",
    "slug": "biorxiv",
    "url": "https://www.biorxiv.org/content/10.64898/2026.11.05.764531v1?rss=1"
  },
  "original_language": "en",
  "account": "Island radiations provide an ideal setting for studying the molecular foundations of convergent evolution. The rapid diversification of Dysdera spiders in the Canary Islands is a prime example, with these arachnids repeatedly evolving a specialization on woodlice. This shift brings about morphological, metabolic, and behavioral adaptations that enable the exploitation of heavy-metal-rich prey.\n\nIn this study, researchers examined two independent instances of dietary specialization on different Canary Islands. By analyzing six high-quality genome assemblies, including three newly generated for this research, they sought to uncover genomic signals of positive selection and relaxed selection in protein-coding genes, upstream regulatory regions, and gene family turnover rates.\n\nSignatures of positive selection were detected in both specialist spiders, while there was a twofold increase in gene loss rates compared to their generalist ancestors. Crucially, positive selection focused on a smaller, functionally cohesive set of genes, potentially involved in detoxification through heavy metal excretion. Conversely, relaxation of selection impacted a wider array of genes linked to functions that may have become superfluous under the new dietary regime.\n\nMoreover, the researchers observed contractions in gene families related to vesicular transport, likely indicating a diminished reliance on vesicle-mediated metal accumulation. Overall, these findings indicate that similar ecological pressures can prompt parallel, yet distinct, adaptive and non-adaptive responses. This suggests partially predictable evolutionary trajectories in island radiations.",
  "summary": "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,…",
  "key_points": [],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}