A new species of the water mite genus Hygrobates Koch, 1837 (Acari: Hydrachnidia: Hygrobatidae) from the ancient Lake Ohrid

Abstract. Ancient lakes represent key ecosystems for endemic freshwater species. This high endemic biodiversity has been shown to be mainly the result of intra-lacustrine diversification. Whereas the principle role of this mode of diversification is generally acknowledged, actual diversification rates in ancient lakes remain little understood. At least four types are conceivable. Diversification rates may be constant over time, they may fluctuate, rates may be higher in the initial phase of diversification, or there may be a pronounced lag phase between colonization and subsequent diversification. As understanding the tempo of diversification in ancient lake environments may help reveal the underlying processes that drive speciation and extinction, we here use the Balkan Lake Ohrid as a model system and the largest species flock in the lake, the non-pyrgulinid Hydrobiidae, as a model taxon to study changes in diversification rates over time together with the respective drivers.Based on phylogenetic, molecular-clock, lineage-throughtime plot, and diversification-rate analyses we found that this potentially monophyletic group is comparatively old and that it most likely evolved with a constant diversification rate. Preliminary data of the SCOPSCO (Scientific Collaboration On Past Speciation Conditions in Lake Ohrid) deepdrilling program do indicate signatures of severe environmental/climatic perturbations in Lake Ohrid. However, so far there is no evidence for the occurrence of catastrophic environmental events. We therefore propose that the constant diversification rate observed in endemic gastropods has been caused by two factors: (i) a potential lack of catastrophic environmental events in Lake Ohrid and/or (ii) a probably high ecosystem resilience, buffering environmental changes. Parameters potentially contributing to the lake's high ecosystem resilience are its distinct bathymetry, ongoing tectonic activities, and karst hydrology.The current study not only contributes to one of the overall goals of the SCOPSCO deep-drilling program -inferring the driving forces for biotic evolution in Lake Ohrid. It might also enhance our understanding of how ecosystem resilience, in general, may promote relatively constant diversification rates in isolated ecosystems. However, we encourage future studies testing hypotheses about the lack of catastrophic events in Lake Ohrid. These studies should be based on high-resolution data for the entire geological history of the lake, and they should potentially involve information from the sediment fossil record, not only for gastropods but also for other groups with a high share of endemic taxa.

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“…So far, at least 185 taxa have been described Pešić, 2015;Stocchino et al, 2013;Wysocka et al, 2013). In addition, there is a rich protist flora.…”

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confidence: 99%

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

et al. 2015

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“…Previous studies showed that the lake is characterised by a high rate of endemism (36%, Albrecht & Wilke, 2008) compared to other ancient lakes, such as the much bigger Lake Victoria (31.3%). So far, nearly 350 endemic species have been described from Lake Ohrid, of which at least 188 are animals (Albrecht & Wilke, 2008; Hauffe et al., 2015; Pešič, 2015; Stelbrink et al., 2016).…”

Section: Introductionmentioning

confidence: 99%

Distribution, diversity and diversification from DNA barcoding perspective: The case of Gammarus radiation in the ancient Lake Ohrid

Mamos,

Grabowski,

Sworobowicz

et al. 2024

Journal of Biogeography

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AimA detailed, comparative DNA‐barcoding and morphospecies‐based overview of the vertical and horizontal distribution of Lake Ohrid's endemic Gammarus species flock is provided. Re‐evaluation of the time frame for the onset of the species flock and identification of events that putatively influenced diversification processes.LocationLake Ohrid, Balkan Peninsula, Europe.TaxonGammarus species flock (Amphipoda, Crustacea).MethodsExtensive sampling and DNA barcoding of 600 individuals was carried out. DNA sequences were analysed using species delimitation methods, haplotype network reconstructions, Bayesian molecular dating and demographic analyses. The COI‐based species delimitation results were validated with nuclear 28S RNA data.ResultsThe species flock distribution has a weak horizontal but clear vertical structure. The diversity along bathymetric gradients correlates with temperature and salinity; and the highest diversity is observed in sublittoral and springs on the lake's shore. Two new molecular units representing putatively new species are revealed and supported also by the nuclear marker. The onset of flock radiation overlaps with the time of lake formation. The COI gene shows signs of positive selection and an acceleration in substitution rate. The demographic changes within the flock happened during the last thousands years.Main ConclusionsDistribution of the Gammarus species flock is vertically structured, reflecting habitat zonation. Parapatric speciation is one of the possible mechanisms behind the flock's diversification. Detection of new MOTUs suggests that the flock's diversity is still not fully revealed. Simultaneously, failure to collect three previously known MOTUs suggests a loss of gammarid diversity in the lake. This represents, together with the current threats to the lake ecosystem (i.e. climate changes, development of tourism), a clear call for conservation efforts. The speciation events and demographic changes within the flock relate presumably to glacial and postglacial water level changes and to the colonisation of new depth ranges and the associated springs.

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“…Previous studies showed that, taking into account its surface, the lake is characterised by a high rate of endemism (36%) compared to other ancient lakes (Albrecht & Wilke, 2008), such as for example the much bigger Lake Victoria (31.3 %). So far, nearly 350 endemic species have been described from Lake Ohrid, of which at least 188 are animals (Albrecht & Wilke, 2008;Hauffe et al, 2015;Pešič, 2015;Stelbrink et al, 2016;Stocchino et al, 2013). Lake Ohrid region was designated a UNESCO World Heritage Site for its natural values in 1979 and for its cultural heritage values a year later (Centre, 2022).…”

Section: Introductionmentioning

confidence: 99%

Distribution, diversity and diversification from a DNA barcoding perspective: the case ofGammarusradiation in Europe’s oldest inland waterbody - the ancient Lake Ohrid

Mamos

Grabowski

Sworobowicz

et al. 2023

Preprint

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Aim A detailed, comparative DNA-barcoding and morphospecies based overview of the vertical and horizontal distribution of Lake Ohrid endemic Gammarus species-flock. Re-evaluation of the origin of the species-flock dating, identification of events that putatively influenced diversification patterns in the species-flock. Location Lake Ohrid: a deep and ancient lake of tectonic origin, biosphere reserve, UNESCO World Heritage Site, located on the Macedonia/Albania border. Taxon Gammarus species-flock (Amphipoda, Crustacea) Methods Extensive sampling and DNA barcoding of 600 individuals were carried out. DNA sequences were analysed using species delimitation methods, haplotype network reconstructions, Bayesian molecular dating and demographic analysis. The COI-based delimitation results were validated with nuclear 28S RNA data. Results The species flock distribution has weak horizontal but clear vertical structure. The diversity across bathymetric gradients correlates with temperature and salinity; and the highest diversity with sublittoral and springs of lake`s shore. Two new MOTUs representing putatively new species are revealed and supported also by the nuclear marker. The time of flock radiation overlaps with the time of lake formation. The COI gene shows signs of positive selection and an acceleration in substitution rate. The demographic changes of the flock happened during the last ky. Main conclusions Distribution of the Gammarus species-flock is vertically structured, reflecting habitat zonation. Parapatric speciation as one of the mechanisms in flock`s diversification is suggested. Detection of new MOTU suggests that the flock`s diversity is still not fully revealed. Nevertheless, failure to recover three other MOTUs suggests the loss of gammarid diversity in the lake. This represents,together with the current threats to the lake ecosystem (i.e. climate changes, development of tourism), a clear call for conservation efforts. The speciation events and demographic changes within the flock relate presumably to glacial and postglacial water level changes and to colonisation of new depth ranges and the associated springs.

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A new species of the water mite genus Hygrobates Koch, 1837 (Acari: Hydrachnidia: Hygrobatidae) from the ancient Lake Ohrid

Cited by 5 publications

References 4 publications

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

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

Distribution, diversity and diversification from DNA barcoding perspective: The case of Gammarus radiation in the ancient Lake Ohrid

Distribution, diversity and diversification from a DNA barcoding perspective: the case ofGammarusradiation in Europe’s oldest inland waterbody - the ancient Lake Ohrid

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