Publication Date:
2016-11-04
Description:
Molecular and morphological evidence indicates that the widespread North Pacific species Diaulula sandiegensis is a complex of two pseudocryptic species. One ranges from the Sea of Japan to northern California, whereas the other is found from northern California to Baja California. The name Diaulula sandiegensis applies to the southern species and Diaulula odonoghuei Steinberg, 1963 to the northern species; a neotype is designated for the latter. The two have consistent differences in colour pattern that were overlooked in previous studies. Field observations from San Diego, California, to Bamfield, British Columbia, revealed that the ranges of the two species partially overlap: D. odonoghuei is restricted to intertidal and bay habitats from Fort Bragg, California northwards, whereas D. sandiegensis is found throughout the entire region and is more common in subtidal habitats. Both species feed primarily on a sponge, Haliclona sp., in intertidal habitats, but faecal analysis indicated that D. sandiegensis in subtidal habitats feeds on Neopetrosia problematica . Haplotype-network analyses reveal substantial levels of genetic diversity in both species, which is highly structured in D. odonoghuei , suggesting a complex history for this species. Field surveys, a common garden experiment and a mating study were conducted to investigate the presence of assortative mating. During two mating trials, individuals that encountered one another for the first time always mated with the same species (11 matings). Reproductive isolation in the form of premating barriers may explain the absence of gene flow between these geographically overlapping sister species. A molecular-clock analysis indicates that glacial events may have played a role in speciation and the origin of population structure in the D. sandiegensis species complex, possibly through climate-driven vicariant events.
Print ISSN:
0260-1230
Electronic ISSN:
1464-3766
Topics:
Biology
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