Z. Fehér, C. Albrecht, Á. Major†, S. Sereda & V. Krízsik (2012): Extremely low genetic diversity in the endangered striped nerite, Theodoxus transversalis (Mollusca, Gastropoda, Neritidae) – a result of ancestral or recent effects? North-Western Journal of Zoology 8(2): 300-307.
Abstract
The striped nerite (Theodoxus transversalis), once a widespread freshwater snail, is of high conservation priority as the majority of its populations have become extinct during the past few decades. We have performed a preliminary study to calculate intraspecific variability of the T. transversalis using two different DNA markers, the mitochondrial cytochrome c oxidase subunit I (COI) and the intron of the nuclear-coded ATP synthase subunit α (ATPSα). Surprisingly, the intraspecific variability is very low; we have found only three closely related haplotypes of each marker. Considering that the sampling sites represent well the whole present range of the species, this phenomenon seems to be the consequence of a historical bottleneck. In our view, the whole Holocene range has been colonized by descendants of a bottlenecked population. Low genetic diversity, however, was not an obstacle for this species to obtain a relatively wide range and abundance until the recent past. Comparison with other Theodoxus species of similar sized historical ranges raises the idea that possibly reduced genetic diversity accounts for the species' high sensitivity to water quality and habitat alteration. Based on these data, the species represents a single management unit for conservation, i.e. each viable population shall play an equal role in the preservation of the species in the future. To prevent the extinction of Theodoxus transversalis, high priority should be directed to the maintenance of suitable habitat conditions as well as monitoring the conservation status of persistent populations.
Keywords
bottleneck, demographic history, intraspecific molecular diversity, mismatch distribution, mitochondrial COI, nuclear-coded ATPSα, Theodoxus transversalis
Abstract
The striped nerite (Theodoxus transversalis), once a widespread freshwater snail, is of high conservation priority as the majority of its populations have become extinct during the past few decades. We have performed a preliminary study to calculate intraspecific variability of the T. transversalis using two different DNA markers, the mitochondrial cytochrome c oxidase subunit I (COI) and the intron of the nuclear-coded ATP synthase subunit α (ATPSα). Surprisingly, the intraspecific variability is very low; we have found only three closely related haplotypes of each marker. Considering that the sampling sites represent well the whole present range of the species, this phenomenon seems to be the consequence of a historical bottleneck. In our view, the whole Holocene range has been colonized by descendants of a bottlenecked population. Low genetic diversity, however, was not an obstacle for this species to obtain a relatively wide range and abundance until the recent past. Comparison with other Theodoxus species of similar sized historical ranges raises the idea that possibly reduced genetic diversity accounts for the species' high sensitivity to water quality and habitat alteration. Based on these data, the species represents a single management unit for conservation, i.e. each viable population shall play an equal role in the preservation of the species in the future. To prevent the extinction of Theodoxus transversalis, high priority should be directed to the maintenance of suitable habitat conditions as well as monitoring the conservation status of persistent populations.
Keywords
bottleneck, demographic history, intraspecific molecular diversity, mismatch distribution, mitochondrial COI, nuclear-coded ATPSα, Theodoxus transversalis
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