New paper dealing with a ‘cryptic species complex’ of polyplacophoran molluscs (chitons) published in Marine Biodiversity! Open access, please read here: http://bit.ly/2okQQ56
In this work, we present a case study of a total-evidence approach to resolving difficult and perplexing ‘cryptic species complexes’. A Pacific shallow water chiton Leptochiton rugatus (Carpenter in Pilsbry, 1892) is supposed to have a very wide range from Japan to Baja California, but has been previously suggested to comprise several cryptic species. Our genetic haplotype network using specimens across the range revealed four discrete clusters. Most strikingly, the haplotype of L. rugatus sensu stricto (California to Baja California) was very different in structure from that of the cluster ranging from the panhandle of Alaska to Oregon. The latter was found to have extremely high side fidelity and patchy distribution, and we present evidence that it is likely a brooder. The difference in life-history strategies between these two clusters account for the differences in their genetic structure. Although morphological differences were observed, these were minor and insufficient to guarantee each as species-level lineages alone. Only with the difference in life-history strategy could they be confidently recognised as separate species, the latter we described as L. cascadiensis sp. nov. after the Cascadia costal bioregion which it inhabits.
L. cascadiensis harbouring putative eggs in the pallial cavity
Things without names are difficult to rationalise, and are difficult to conserve; assigning names to species is therefore critical to understanding and conserving biodiversity. This study shows that combining evidence from molecules, morphology, and importantly life-history, is key to untangling ‘cryptic species complexes’ which have become increasingly discovered in the recent years. The take-home message: if you want to solve cryptic species problems, don’t forget to look at their way of life!
Representative specimens of the 13 mollusc species collected from shallow hydrothermal vents off Kueishan Island, Taiwan