Cryptic habitats and cryptic diversity: unexpected patterns of connectivity and phylogeographical breaks in a Mediterranean endemic marine cave mysid.
The marine cave-dwelling mysid Hemimysis margalefi is distributed over the whole Mediterranean Sea, which contrasts with the poor dispersal capabilities of this brooding species. In addition, underwater marine caves are a highly fragmented habitat which further promotes strong genetic structuring, therefore providing highly informative data on the levels of marine population connectivity across biogeographical regions. This study investigates how habitat and geography have shaped the connectivity network of this poor disperser over the entire Mediterranean Sea through the use of several mitochondrial and nuclear markers. Five deeply divergent lineages were observed among H. margalefi populations resulting from deep phylogeographical breaks, some dating back to the Oligo-Miocene. Whether looking at the intralineage or interlineage levels, H. margalefi populations present a high genetic diversity and population structuring. This study suggests that the five distinct lineages observed in H. margalefi actually correspond to as many separate cryptic taxa. The nominal species, H. margalefi sensu stricto, corresponds to the westernmost lineage here surveyed from the Alboran Sea to southeastern Italy. Typical genetic breaks such as the Almeria-Oran Front or the Siculo-Tunisian Strait do not appear to be influential on the studied loci in H. margalefi sensu stricto. Instead, population structuring appears more complex and subtle than usually found for model species with a pelagic dispersal phase. The remaining four cryptic taxa are all found in the eastern basin, but incomplete lineage sorting is suspected and speciation might still be in process. Present-day population structure of the different H. margalefi cryptic species appears to result from past vicariance events started in the Oligo-Miocene and maintained by present-day coastal topography, water circulation and habitat fragmentation.
Institut Méditerranéen de Biodiversité et d'Écologie Marine et Continentale (IMBE), UMR 7263 CNRS, IRD, Aix Marseille Université, Avignon Université, Station Marine d'Endoume, Rue de la Batterie des Lions, 13007, Marseille, France.
Pierre-Alexandre
PA
Rastorgueff
Pierre
P
Chevaldonné
Defne
D
Arslan
Caroline
C
Verna
Christophe
C
Lejeusne
D000818:Animals; D001499:Bayes Theorem; D059552:Caves; D002467:Cell Nucleus / Q000235:genetics; D003445:Crustacea / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000235:genetics; D017753:Ecosystem; D014644:Genetic Variation; D005828:Genetics, Population; D016013:Likelihood Functions; D008522:Mediterranean Sea; D008957:Models, Genetic; D058974:Phylogeography; D017422:Sequence Analysis, DNA
D004272:DNA, Mitochondrial
Hemimysis margalefi; Mediterranean cryptic species; Mysid phylogeography; marine caves; metapopulation; population connectivity