Environment not dispersal limitation drives clonal composition of Arctic Daphnia in a recently deglaciated area

Abstract

One of the most prominent manifestations of the ongoing climate warming is the retreat of glaciers and ice sheets around the world. Retreating glaciers result in the formation of new ponds and lakes, which are available for colonization. The gradual appearance of these new habitat patches allows us to determine to what extent the composition of asexual Daphnia (water flea) populations is affected by environmental drivers vs. dispersal limitation. Here, we used a landscape genetics approach to assess the processes structuring the clonal composition of species in the D. pulex species complex that have colonized periglacial habitats created by ice-sheet retreat in western Greenland. We analysed 61 populations from a young (<50 years) and an old cluster (>150 years) of lakes and ponds. We identified 42 asexual clones that varied widely in spatial distribution. Beta-diversity was higher among older than among younger systems. Lineage sorting by the environment explained 14% of the variation in clonal composition whereas the pure effect of geographical distance was very small and statistically insignificant (Radj2 = 0.010, P = 0.085). Dispersal limitation did not seem important, even among young habitat patches. The observation of several tens of clones colonizing the area combined with environmentally driven clonal composition of populations illustrates that population assembly of asexual species in the Arctic is structured by environmental gradients reflecting differences in the ecology of clones.

Founder effects determine the genetic structure of the water flea Daphnia in Ethiopian reservoirs

“…Still, a correlation with environmental variables may result when particular haplotypes would hitchhike with particular genotypes or fixed allele combinations that are favored under certain conditions. Three studies on strictly asexual zooplankton with comparable sample sizes and statistical power found clear environmental and/or spatial structuring in their studies (Aguilera et al 2007;Pantel et al 2011, Haileselasie et al 2016 suggesting that the lack of patterns in our dataset is not merely a consequence of insufficient statistical power. Evolution-mediated priority effects, the key feature of the monopolization hypothesis (De Meester et al 2002;De Meester et al 2016), are expected to be less important in asexual taxa than in similar sexual taxa, due to a reduced ability for rapid local adaptation in the asexuals.…”

Meiofauna as a model to test paradigms of ecological metacommunity theory

“…Further, to better quantify dispersal, studies covering several spatial scales and different parts of aquatic network are needed (Heino et al, 2015a). Investigations of colonization may be further supported by examining the genetic diversity of metapopulations (Haileselasie et al, 2016;Copilaş-Ciocianu & Petrusek, 2017) and by DNA metabarcoding of whole assemblages.…”

Centennial clonal stability of asexualDaphniain Greenland lakes despite climate variability

“…Conductivity is the dominant control on algal composition in this area and is highly correlated with both DOC concentration and CDOM quality [37]. Conductivity was also identified as one of the major factors driving clonal composition of Daphnia populations in an area about 250 km north of Kangerlussuaq [30]. Lakes SS1381 and SS1590 have never been connected hydrologically, since SS1381 lies outside the boundary of the large palaeolake that included SS4 in the period immediately after deglaciation [41].…”

“…Arctic Daphnia populations are generally obligate asexuals [26,27], and many of these lineages are triploids [28]. In the Illulissat area of West Greenland, clonal richness of Daphnia pulex populations was between 4 and 5 genotypes [29,30]. The lakes along Kangerlussuaq in SW Greenland are particularly well-studied in relationship to recent climate change, with evidence for a dramatic increase in environmental forcing of these sensitive habitats [31].…”