Patterns of genetic differentiation and population history of endemic isopods (Asellidae) from ancient Lake Ohrid: combining allozyme and mtDNA data

Abstract

Ancient lakes as places of extensive speciation processes have been characterized by a high degree of endemicity and biodiversity. The most outstanding European ancient lake is the oligotrophic and karstic Balkan Lake Ohrid. The lake is inhabited by a number of endemic species, but their evolutionary history is largely unresolved. in the present study, the genetic structure, gene genealogy and demographic history of the representatives of the Ohridian endemic Proasellus species were studied using both biparentally (allozyme loci) and maternally (partial mitochondrial cytochrome oxidase subunit I gene) inherited markers. Both data sets gave similar results and supported discrepancies among genetic differentiation, the current morphology-based taxonomy and bathymetric segregation. Horizontal distribution of endemic Proasellus species (Lake Ohrid vs adjacent feeder springs) within the lake presumably promote parapatric speciation whereas the main role of vertical barriers into diversification processes was not fully supported. The analyses of demographic history suggested the decline of endemic isopod populations. The radiation of endemic Proasellus populations within the lake could have started from the sublittoral/profundal zone towards the littoral or in the opposite direction — from the littoral to the profundal. Our analyses did not exclude both possibilities.

Surprisingly high genetic divergence of the mitochondrial DNA barcode fragment (COI) within Central European woodlice species (Crustacea, Isopoda, Oniscidea)

“…(Poulakakis and Sfenthourakis 2008), Helleria brevicornis Ebner, 1868 (Gentile et al 2010), or two species of the genus Trachelipus Budde-Lund, 1908 (Parmakelis et al 2008). Similar results have been also demonstrated for freshwater isopods of the genus Asellus Geoffroy, 1762 (Verovnik et al 2004;Verovnik et al 2005;Sworobowicz et al 2015;Pérez-Moreno et al 2017) and Proasellus Dudich, 1925(Ketmaier 2002Eme et al 2013;Kilikowska et al 2013). Our data set revealed extremely high intraspecific distance values for the myrmecophilous isopod Platyarthrus hoffmannseggii Brandt, 1833 (n = 33), with a maximum value of 29.4% (Tab.…”

Constant diversification rates of endemic gastropods in ancient Lake Ohrid: ecosystem resilience likely buffers environmental fluctuations

“…Preliminary data of the SCOPSCO deep-drilling program based on core catcher data for the last 1.2 My and high-resolution data for the last 640 thousand years (ky) so far do not indicate the occurrence of catastrophic environmental events Wagner et al, 2014), i.e., events that lead to sudden drastic regime shifts (sensu Scheffer and Carpenter, 2003;Scheffer et al, 2001) and thus potentially to mass extinction. By comparison, such events have been observed in other ancient lakes, including Lake Titicaca (Kroll et al, 2012;Lavenu, 1992) and Lake Malawi (Cohen et al, 2007;Schultheiß et al, 2009Schultheiß et al, , 2011. We do, however, see signatures of severe environmental/climatic perturbations in Lake Ohrid, including significant lake-level drops (Lindhorst et al, 2010), volcanic ash deposits Wagner et al, 2014), and glacial-interglacial cycles (Lézine et al, 2010;Reed et al, 2010;Wagner et al, 2014).…”

“…Another theory suggests that diversification rates can be higher in the initial phase of diversification (particularly in groups that diversify through an adaptive radiation) and may decline once niche spaces becomes successively occupied (e.g., Purvis et al, 2009;Schluter, 2000). This may happen after a lake first came into existence or after the occurrence of major environmental events such as volcanic ash deposits, severe lake-level drops, and desiccation or salinization events (Cristescu et al, 2010;Kroll et al, 2012;Salzburger et al, 2014). A forth theory proposes the opposite, i.e., the existence of a pronounced lag phase between colonization and onset of diversification (e.g., Cristescu et al, 2010).…”

“…Of the few ancient lakes in the world, even fewer fulfil the above criteria. Some lakes, despite being old, have gone through a series of major environmental events, and the respective endemic species are often comparable young, as observed in Lake Malawi (e.g., Schultheiß et al, 2009Schultheiß et al, , 2011 and Lake Titicaca (Kroll et al, 2012). Other lakes such as Lake Baikal (e.g., Ivanov et al, 2013) and Lake Tanganyika (e.g., Salzburger et al, 2014; might be sufficiently old but lack a continuous paleo-limnological record.…”

Diversity of invertebrates in the Republic of Macedonia

“…The papers of Kilikowska et al (2006Kilikowska et al ( , 2013 and Wysocka et al (2008Wysocka et al ( , 2013 shed light on the phylogenetic relationships in the genera Proasellus and Gammarus from Ohrid Lake, but some of the taxonomic problems still remain.…”