High genetic variation and phylogeographic relations among Palearctic fairy shrimp populations reflect persistence in multiple southern refugia during Pleistocene ice ages and postglacial colonisation

Abstract

Intense anthropogenic disturbance threatens temporary pond ecosystems and their associated fauna across the Palearctic. Since fairy shrimps (Crustacea, Branchiopoda) are endemic to temporary ponds, populations are declining due to habitat loss and it is important to define adequate units for conservation. Phylogeographic reconstructions, based on genetic variation, provide valuable information for defining evolutionary and conservation units, especially for organisms with high levels of cryptic diversity like many fairy shrimps. We studied a total of 152 individuals of the fairy shrimp Branchipus schaefferi from 79 populations across the Palearctic and used mitochondrial (CO1) and nuclear (ITS1) DNA data to reconstruct the phylogeography of the species. Our results show that B. schaefferi comprises four highly diverged (10.3–16.5%) evolutionary clades. The present‐day haplotypes within each of the clades probably diverged from lineages that were maintained in separate refugia during the Pleistocene ice ages. While two clades represent distinct geographic regions, the two remaining clades have more wide and overlapping ranges. In addition, the limited number of shared haplotypes among populations from geographically distant regions within three of the clades suggest recent long‐distance dispersal events. Overall, the studied B. schaefferi dataset comprises high levels of genetic differentiation, without a clear morphological signal. Phylogenetic searches and pairwise genetic distances suggest that the studied lineages belong to a complex of four morphologically cryptic species. Since these four evolutionary old clades persist (±2 million years), despite overlapping geographic ranges and since they span a variety of ecological conditions, they should be considered as separate evolutionary significant units for conservation.

Distinctive genetic signatures of two fairy shrimp species with overlapping ranges in Iberian temporary ponds

“…Furthermore, our estimates for the age of the MRCA of Branchipus schaefferi (7.1 [13.5–0.4] myr) agrees with estimates by Lukić et al. (2019). Also, our estimate of the age of the MRCA of the genus Triops is consistent with estimates by Korn et al.…”

“…Despite the high passive dispersal potential of fairy shrimps, the existence of a large number of unique haplotypes has been reported in several species (Aguilar, 2011; Arukwe & Langeland, 2013; Ketmaier et al., 2005; Lukić et al., 2019; Rodríguez‐Flores et al., 2020; Vanschoenwinkel et al., 2011). In our case, the absence of a central most common haplotype and the presence of unique haplotypes in the networks of T .…”

“…cf. wolfi, B. schaefferi, Chirocephalus diaphanus ) (Andrews, 2013; Deiner et al., 2017; Lukić et al., 2019; Reniers et al., 2013; Vanschoenwinkel et al., 2011). Nonetheless, shallower divergences have also been detected, particularly in species with widespread distributions (e.g.…”

“…In the light of the everything is everywhere hypothesis originally sustained by Darwin (1859), no genetic structure would be expected wolfi, B. schaefferi, Chirocephalus diaphanus) (Andrews, 2013;Deiner et al, 2017;Lukić et al, 2019;Reniers et al, 2013;Vanschoenwinkel et al, 2011). Nonetheless, shallower divergences have also been detected, particularly in species with widespread distributions (e.g.…”

“…Davies et al., 1997; Deiner et al., 2017; Ketmaier et al., 2012; Pinceel et al., 2013; Vanschoenwinkel et al., 2011) or large (e.g. Aguilar et al., 2017; Bohonak, 1998; Eimanifar et al., 2015; Lukić et al., 2019; Muñoz et al., 2008; Reniers et al., 2013) geographic ranges have generated contrasting results.…”