Ecological Review of the Species Complex.

AbstractThe set of four closely related solitary ascidians spp. were once considered a single cosmopolitan species, , but are now recognized as genetically and morphologically distinct species. The possibility of ecological differences between the species was not widely considered in studies preceding the schism of spp. Consequently, there may be an over-generalization of the ecology of spp., with potential implications for the broad range of studies targeting these species, encompassing the evolution, development, genomics, and invasion biology of spp. We completed a comprehensive review of the ecology of spp. to establish the similarities and differences between the widely distributed and (and what little is known of the two other species, sp. C and sp. D). When necessary, we used study locations and the species' geographic ranges to infer the species in each study in the review. As expected, ecological similarities are the norm between the two species, spanning both abiotic and biotic interactions. However, there are also important differences that have potential implications for other aspects of the biology of spp. For example, differences in temperature and salinity tolerances likely correspond with the disparities in the geographic distribution of the species. Asymmetries in topics studied in each species diminish our ability to fully compare several aspects of the ecology of spp. and are priority areas for future research. We anticipate that our clarification of common and unique aspects of each species' ecology will help to provide context for future research in many aspects of the biology of spp.