A tale of time and depth: intralacustrine radiation in endemicGammarusspecies flock from the ancient Lake Ohrid

Abstract

Tentatively dated, the Plio‐/Pleistocene origin of the ancient Lake Ohrid on the Balkan Peninsula makes it the oldest ancient lake in Europe. Given the surface area of the lake and the adjusted endemicity rate, it may be also defined as the most diverse of all the ancient lakes in the world. From all the animal groups endemic to this lake, gammarids are amongst the most scarcely known in terms of their diversity and phylogenetic relationships. Partial DNA sequences of two mitochondrial genes, cytochrome oxidase subunit I (cox1) and 16S ribosomal RNA (16S rRNA) of eight known endemic Gammarus species from the Lake Ohrid valley were analysed. Phylogenetic analyses showed that endemic Gammarus species comprise an ancient species flock, with Gammarus sketi from the feeder springs being their sister taxon outside the lake. Amongst the species inhabiting the lake, Gammarus solidus and Gammarus salemaai are morphologically and molecularly well defined. By contrast, Gammarus ochridensis, Gammarus parechiniformis, Gammarus lychnidensis, and Gammarus stankokaramani revealed high discrepancy between morphological and genetic data. None of these morphospecies form a monophyletic clade and a significant degree of apparent gene flow occurs between them. This could be caused by incomplete lineage sorting and/or hybridization events. Two novel mtDNA lineages were found within the lake, possibly constituting two new species (Gammarus sp. 1 and Gammarus sp. 2). Molecular clock analysis showed that the split between G. sketi and the Gammarus species flock from the lake occurred approximately 5–7 Mya, whereas within the flock there were at least two intralacustrine radiations: one estimated at 2–3 Mya and the second at less than 1 Mya. The first one could be associated with the origin of the lake and the second with the lake water‐level fluctuations during Pleistocene. © 2013 The Linnean Society of London

Morphological vs. molecular delineation of taxa across montane regions in Europe: the case study ofGammarus balcanicusSchäferna, (Crustacea: Amphipoda)

“…Similar pattern was already observed in the cichlid fishes from the ancient lake Victoria (Seehausen ) as well as in gammarid crustaceans from the European ancient Lake Ohrid (Wysocka et al. ). Apparently, in case of the ancient lakes, the morphological diversification with incomplete sorting of genetic lineages may be related to rapid events of sympatric speciation caused by availability of free ecological niches (Elmer et al.…”

A review of Gammaridae (Crustacea: Amphipoda): the family extent, its evolutionary history, and taxonomic redefinition of genera

“…The Ohrid lacustrine species together with those from the surrounding springs constitute a very well‐supported monophylum within the aggregate G. balcanicus . Seven species have been described (Karaman, ; Karaman & Pinkster, ), and there are a few as yet undescribed but reliable species (Hou et al ., , ; Wysocka et al ., ). None of them has the ‘Baikalian’ habitus, but as many as five of them are armed by spines (stout spiniform setae) at the posterior borders of the pleonites (Karaman & Pinkster, ).…”

Origin of the Lake Ohrid gammarid species flock: ancient local phylogenetic lineage diversification

“…Samples of Gammarus species endemic to Lake Ohrid basin were collected from 2007 to 2011 (see Wysocka et al ., ). Species from other water bodies on the Balkan Peninsula, including ponds, springs, streams and rivers were sampled between 2006 and 2012.…”

“…(). All the recognized species seem to show at least partial spatial separation with respect to depth zones and habitat types (Karaman, , ; Salemaa, ; Salemaa & Kamaltynov, ; Wysocka et al ., ).…”