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Oceanic islands are known as test tubes of evolution. Isolated and colonized by relatively few species, islands are home to many of nature’s most renowned radiations from the finches of the Galápagos to the silverswords of the Hawaiian Islands. Despite the evolutionary exuberance of insular life, island occupation has long been thought to be irreversible. In particular, the presumed much tougher competitive and predatory milieu in continental settings prevents colonization, much less evolutionary diversification, from islands back to mainlands. To test these predictions, we examined the ecological and morphological diversity of neotropicalAnolislizards, which originated in South America, colonized and radiated on various islands in the Caribbean, and then returned and diversified on the mainland. We focus in particular on what happens when mainland and island evolutionary radiations collide. We show that extensive continental radiations can result from island ancestors and that the incumbent and invading mainland clades achieve their ecological and morphological disparity in very different ways. Moreover, we show that when a mainland radiation derived from island ancestors comes into contact with an incumbent mainland radiation the ensuing interactions favor the island-derived clade.
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Insect Radiations on Islands: Biogeographic Pattern and Evolutionary Process in Hawaiian Insects.
The spectacular adaptive radiations on the Hawaiian Islands offer the tantalizing possibility of ascertaining the predictability of evolution, especially with regard to how the archipelago’s dynamic geology suggests a priori hypotheses for evolutionary pattern and process. In the past two decades advances in sequencing and phylogenetics have shed new light on the evolution of this model fauna. Here, we provide an overview of recent research on major endemic Hawaiian insect radiations. We find that, in contrast to earlier views, a substantial fraction of Hawaiian insect clades colonized the archipelago prior to the formation of the current high islands (5.1 Ma) and have persisted through one or more rounds of island formation and subsidence prior to the emergence of the current archipelago. Many Hawaiian insect radiations show elements of the progression rule, a null expectation where biogeographic patterns on the phylogeny mirror the chronological sequence of island formation, but few match its predictions exactly. Diversity in most radiations is shaped by a complicated interplay of among-island dispersal and within-island diversification. Finally, we find a positive relationship between clade age and species richness in Hawaiian insects, but with a great deal of variance that is likely explained by aspects of ecology and clade-specific factors.
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- Award ID(s):
- 2030129
- PAR ID:
- 10303146
- Date Published:
- Journal Name:
- The quarterly review of biology
- Volume:
- 96
- Issue:
- 4
- ISSN:
- 0033-5770
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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