Understanding processes at the origin of species flocks with a focus on the marine Antarctic fauna

• Published in: Biological Reviews
• Main Authors: Chenuil, Anne, Saucède, Thomas, Hemery, Lenaïg G., Eléaume, Marc, Féral, Jean-Pierre, Améziane, Nadia, David, Bruno, Lecointre, Guillaume, Havermans, Charlotte
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Wiley 2017
• Subjects: Antarc*; Antarctic
• Online Access: https://epic.awi.de/id/eprint/47405/; https://epic.awi.de/id/eprint/47405/1/2017_Chenuiletal_BiolRev.pdf; https://doi.org/10.1111/brv.12354; https://hdl.handle.net/10013/epic.2ab38bbe-2b7e-4e2d-a2ae-aaad7acc8268

Species flocks (SFs) fascinate evolutionary biologists who wonder whether such striking diversification can be driven by normal evolutionary processes. Multiple definitions of SFs have hindered the study of their origins. Previous studies identified a monophyletic taxon as a SF if it displays high speciosity in an area in which it is endemic (criterion 1), high ecological diversity among species (criterion 2), and if it dominates the habitat in terms of biomass (criterion 3); we used these criteria in our analyses. Our starting hypothesis is that normal evolutionary processes may provide a sufficient explanation for most SFs. We thus clearly separate each criterion and identify which biological (intrinsic) and environmental (extrinsic) traits are most favourable to their realization. The first part focuses on evolutionary processes. We highlight that some popular putative causes of SFs, such as key innovations or ecological speciation, are neither necessary nor sufficient to fulfill some or all of the three criteria. Initial differentiation mechanisms are diverse and difficult to identify a posteriori because a primary differentiation of one type (genetic, ecological or geographical) often promotes other types of differentiation. Furthermore, the criteria are not independent: positive feedbacks between speciosity and ecological diversity among species are expected whatever the initial cause of differentiation, and ecological diversity should enhance habitat dominance at the clade level. We then identify intrinsic and extrinsic factors that favour each criterion. Low dispersal emerges as a convincing driver of speciosity. Except for a genomic architecture favouring ecological speciation, for which assessment is difficult, high effective population sizes are the single intrinsic factor that directly enhances speciosity, ecological diversity and habitat dominance. No extrinsic factor appeared to enhance all criteria simultaneously but a combination of factors (insularity, fragmentation and environmental stability) ...