Genetic variation in bank vole populations in natural and metal-contaminated areas

The effects of isolation and heavy-metal pollution on genetic diversity in Myodes (=Clethrionomys) glareolus populations were studied. Isolation and pollution are considered to have important effects on biodiversity. Animals were collected from ten populations in isolated (island), mainland, and metal-polluted areas. Three populations were in areas near zinc and lead smelters; four were on islands in the relatively unpolluted Mazurian Lake District and in the Bieszczady Mountains; and three were in clean-mainland areas in the Mazurian Lake District, the Niepołomice Forest, and the Bieszczady Mountains. Cadmium and lead concentrations in liver and kidney were measured to assess the animals’ exposure to metals. The metal concentrations were greater in animals from areas classed as polluted than in animals from the clean-mainland areas and islands. The genetic diversity of each population was analyzed using eight microsatellite markers. The results confirmed that isolation adversely affects genetic diversity in M. glareolus populations (giving low heterozygosity and poor allelic richness), but the effect of metal exposure on genetic diversity was not strong. Of the samples from polluted areas, only the Katowice population, which is exposed to high levels of metal pollution and is also isolated because of human activity, showed genetic variation parameters that were similar to those for the island populations. Nei’s genetic distances indicated that the island populations were genetically distant from each other and from the other populations, and there were noticeable inbreeding effects that would have been caused by the isolation of these populations

The impact of isolation and pollution on the genetic variation in bank vole Myodes glareolus populations.

Przeprowadzono badanie mające na celu ocenę wpływu zanieczyszczenia metalami ciężkimi oraz izolacji na wyspach na zmienność genetyczną w populacjach nornicy rudej (Myodes glareolus). W tym celu odłowiono osobniki z 10 polskich populacji. Osobniki zasiedlające lasy w pobliżu Katowic, Miasteczka Śląskiego i Olkusza uznano za narażone na zanieczyszczenie, z wysp na jeziorach Dejguny, Dobskie, Święcajty oraz z Wyspy Skalistej posłużyły do oceny izolacji, a jako referencyjne odłowiono osobniki z Puszczy Niepołomickiej, Teleśnicy Oszwarowej i Mikołajek. Analiza stężeń kadmu i ołowiu w nerkach i wątrobach badanych osobników wykazała istotnie wyższe stężenia metali u osobników z Katowic, Miasteczka Śląskiego i Olkusza. Analizy genetyczne z użyciem 8 mikrosatelitarnych loci wykazały, że populacje są średnio zróżnicowane genetycznie (Fst = 0.103). Ocena zmienności genetycznej w oparciu o liczbę alleli w locus, liczbę alleli prywatnych oraz heterozygotyczność oczekiwaną i obserwowaną nie wykazała negatywnego wpływu zanieczyszczenia na zmienność genetyczną, ujawniła natomiast zubożenie genetyczne populacji wyspowych. Zachowanie różnorodności genetycznej przez populacje z terenów zanieczyszczonych może wynikać z maskującego wpływ selekcji przepływu genów z sąsiednich populacji, natomiast w przypadku populacji wyspowych, woda stanowi skuteczną barierę dla gatunku Myodes glareolus ograniczając migrację osobników, co powoduje zmniejszenie zmienności genetycznej w tych populacjach.An analysis was made to investigate the effects of heavy metal pollution and isolation on islands on genetic variation in 10 Polish populations of bank vole (Myodes glareolus). Populations from forests near Katowice, Miasteczko Śląskie and Olkusz were used to assess effect of contaminants, from islands on lakes Dejguny, Dobskie, Święcajty and Skalista Island were used to evaluate the influence of isolation and populations from area of Niepołomice Forest, Teleśnica Oszwarowa and Mikołajki were used as a reference to the rest of populations. The analyses of cadmium and lead concentration in the kidneys and livers showed significantly higher concentrations of these metals in individuals from area of Katowice, Miasteczko Śląskie and Olkusz. Genetic analysis by using 8 microsatellite loci showed that populations have low genetic diversity (Fst = 0.103). Evaluated genetic diversity by such parameters as: a number of alleles in locus, a number of private alleles, expected and observed heterozygosity did not showed negative effect of contamination, but revealed that populations from island are less genetically diverse. The high genetic variation in populations from contaminated areas is probably masked by migration - gene flow from neighboring populations. In case of isolated populations from islands, water is an effective barrier for individuals migration and therefore decreased genetic diversity in these populations is noted