Large-scale mitochondrial phylogeography in the halophilic fairy shrimp Phallocryptus spinosa (Milne-Edwards, 1840) (Branchiopoda: Anostraca)

In this study we analyzed patterns of sequence divergence in about 1kb of mitochondrial DNA coding for two genes (16S rRNA and Cytochrome Oxidase I, COI) in 15 populations and 61 individuals of the halophilic fairy shrimp Phallocryptus spinosa (Milne-Edwards, 1840). Populations were sampled in saline and hypersaline water bodies from Spain, France, Italy, Greece, Turkey, Ukraine, Iran, Uzbekistan, Cyprus, Algeria, Morocco and Botswana. Our genetic findings suggest complex phylogeographic relationships and pronounced genetic differentiation among populations. Multiple phylogenetic methods and nested clade analysis revealed the existence of four highly divergent maternal lineages with strong phylogeographic patterns and signatures of either allopatric fragmentation or restricted gene flow with isolation by distance. These results are further supported by the hierarchical analysis of molecular variance (AMOVA) and pairwise FST values, which indicate that most of detected genetic heterogeneity is apportioned among populations. Genetic relationships among haplotypes fit geographical hypotheses in most cases but one. Indeed, one haplotype is shared among French, Iranian and Uzbekistan populations. We hypothesize that this peculiar occurrence might be due to an avian-mediated long distance passive dispersal event.