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Abstract Newly arrived species on young or remote islands are likely to encounter less predation and competition than source populations on continental landmasses. The associated ecological release might facilitate divergence and speciation as colonizing lineages fill previously unoccupied niche space. Characterizing the sequence and timing of colonization on islands represents the first step in determining the relative contributions of geographical isolation and ecological factors in lineage diversification. Herein, we use genome-scale data to estimate timing of colonization in Naesiotus snails to the Galápagos islands from mainland South America. We test inter-island patterns of colonization and within-island radiations to understand their contribution to community assembly. Partly contradicting previously published topologies, phylogenetic reconstructions suggest that most Naesiotus species form island-specific clades, with within-island speciation dominating cladogenesis. Galápagos Naesiotus also adhere to the island progression rule, with colonization proceeding from old to young islands and within-island diversification occurring earlier on older islands. Our work provides a framework for evaluating the contribution of colonization and in situ speciation to the diversity of other Galápagos lineages.
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When adaptive radiations collide: Different evolutionary trajectories between and within island and mainland lizard clades
Significance Isolated and infrequently colonized, islands harbor many of nature’s most renowned evolutionary radiations. Despite this evolutionary exuberance, island occupation has long been considered irreversible: The much tougher competitive and predatory milieu on mainlands prevents colonization, much less evolutionary diversification, from islands to continents. To test these postulates, we examined neotropicalAnolislizards, asking what happens when mainland and island evolutionary radiations collide. Far from being a dead end, we show that island-to-mainland colonization seeded an extensive radiation that achieved its ecomorphological disparity in ways distinct from their island ancestors. Moreover, when the incumbent and island-derived radiations collided, the ensuing interactions favored the latter, together highlighting a persistent role of both historical contingency and determinism in adaptive radiation.
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- Award ID(s):
- 1835893
- PAR ID:
- 10505648
- Publisher / Repository:
- PNAS
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 118
- Issue:
- 42
- ISSN:
- 0027-8424
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1073/pnas.2024451118
