期刊
BIOLOGY LETTERS
卷 6, 期 6, 页码 807-810出版社
ROYAL SOC
DOI: 10.1098/rsbl.2010.0423
关键词
anagenesis; biogeography; extinction; Hesperotestudo; island area; sea-level cycles
资金
- Bermuda Aquarium, Museum and Zoo (BAMZ) [141]
- Division Of Earth Sciences
- Directorate For Geosciences [929415] Funding Source: National Science Foundation
During the last half million years, pulses of gigantism in the anagenetic lineage of land snails of the subgenus Poecilozonites on Bermuda were correlated with glacial periods when lower sea level resulted in an island nearly an order of magnitude larger than at present. During those periods, the island was colonized by large vertebrate predators that created selection pressure for large size and rapid growth in the snails. Extreme reduction in land area from rising seas, along with changes in ecological conditions at the onset of interglacial episodes, marked extinction events for large predators, after which snails reverted to much smaller size. The giant snails were identical in morphology during the last two glacials when the predators included a large flightless rail Rallus recessus (marine isotope stages (MIS) 4-2) and a crane Grus latipes and a duck Anas pachysceles (MIS 6). In a preceding glacial period (MIS 10), when the fauna also included the tortoise Hesperotestudo bermudae, the snails were not only large, but the shells were much thicker, presumably to prevent crushing by tortoises. Evolution of Poecilozonites provides an outstanding example of dramatic morphological change in response to environmental pressures in the absence of cladogenesis.
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