Phylogeography of the Chydorus sphaericus Group (Cladocera: Chydoridae) in the Northern Palearctic

Abstract

The biodiversity and the biogeography are still poorly understood for freshwater invertebrates. The crustacean Chydorus sphaericus-brevilabris complex (Cladocera: Chydoridae) is composed of species that are important components of Holarctic freshwater food webs. Recent morphological and genetic study of the complex has indicated a substantial species diversity in the northern hemisphere. However, we know little of the geographic boundaries of these novel lineages. Moreover, a large section of the Palearctic remains unexamined at the genetic level. Here we attempt to address the biodiversity knowledge gap for the Chydorus sphaericus group in the central Palearctic and assess its diversity and biogeographic boundaries. We sequenced nuclear (ITS-2) and mitochondrial (COI) gene regions of Chydorus specimens across the Palearctic and compared them with already available Holarctic sequences. We detected six main clades in the C. sphaericus group in the Palearctic, of which two of the groups are novel. Three of the more divergent clades are geographically widespread. The central portion of Eurasia (the Yenisey River basin) appears to be a narrow zone of secondary contact for phylogroups that expanded from European and Beringian refugia. As such, the previously unsampled central Palearctic represents an important region for understanding the evolutionary consequences of Pleistocene climatic oscillations on the Chydorus sphaericus group.

Phylogeography of Daphnia magna Straus (Crustacea: Cladocera) in Northern Eurasia: Evidence for a deep longitudinal split between mitochondrial lineages

“…The width of this zone and its North-South extension cannot currently be assessed due to a lack of available samples. However, the lake in which the two super-clades are found to co-occur is located in the Ob' River basin, in the Easternmost part of Western Siberia, somewhat west to the transition zone between two super-groups of haplotypes previously identified in other cladocerans [ 31 , 32 ]. Regardless, our findings provide strong additional evidence for a marked longitudinal (East-West) differentiation of the cladoceran fauna in Northern Eurasia.…”

“…For two taxa ( Moina and Chydorus ), we demonstrated the existence of two faunistic super-complexes: (1) a European-Western Siberian super-complex and (2) a Eastern Siberian-Far Eastern super-complex, with a transition zone in the Yenisey basin, approximately near the boundary between Western and Eastern Siberia [ 31 ]. We also identified a special role of a Beringian region (including the Chukot Area of Russia, Kamchatka Peninsula, Alaska and surrounding territories) as a center of dispersion of cladocerans in Eurasia [ 32 ]. The generality of these patterns needs further verification, based on analyses of other taxa, as the identification of general patterns has the potential to strongly improve our understanding of the history of the whole freshwater fauna of Northern Eurasia.…”

Crustacean remains from the Yuka mammoth raise questions about non-analogue freshwater communities in the Beringian region during the Pleistocene

“…Chydorus cf. sphaericus is a species group represented in Eurasia by at least three taxa with indistinguishable parthenogenetic females 35,36 , while gamogenetic specimens are rare. Different taxa from the Daphnia longispina group inhabit water bodies of different types 37 ; since several taxa occur in the region this group could not be used as an indicator of abiotic factors or waterbody type.…”

An annotated checklist of the freshwater cladocerans (Crustacea: Branchiopoda: Cladocera) of Ecuador and the Galápagos Islands

“…The species was initially described from Denmark (Smirnov, 1971). This is a very difficult cosmopolitan species complex with many taxa, as revealed by genetic methods (Belyaeva, Taylor, 2009;Kotov et al, 2016). The name "C. sphaericus" is used for nearly every Chydorus around the world, and it is not certain that all these records belong to the C. sphaericus group.…”