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

Abstract

Founder effects introduce stochasticity in the genetic structure of species at the regional scale. To the extent that founder effects are important, they will result in a reduced signature of space, time, and environmental variation in landscape genetic data. We studied the metapopulation genetic structure of recently founded populations of the microcrustacean Daphnia sinensis in 10 Ethiopian water reservoirs. We used three different approaches to estimate the number of effective founders and applied them to two independent genetic marker sets in an effort to investigate the role of founder effects and to estimate effective size of the founding population. Estimates of founding sizes rarely exceeded eight individuals but were most often limited to less than four individuals. No associations of genetic identities, gene frequencies, measures of genetic diversity, or differentiation with environmental and spatial variables were found. Age and size of the reservoirs were not correlated with genetic diversity measures or number of founders in these reservoirs. These findings indicate that neither strong selection, nor dispersal limitation are responsible for the observed pattern of genetic variation. Our results suggest a regional population structure that is strongly impacted by founder events, reflecting colonization by just a few founders per waterbody, and not noticeably influenced by subsequent dispersal and gene flow. Our results show that rapid colonization of empty habitats and fast population growth by a handful of founders can result in strong founder effects, even in relatively large habitats that are likely regularly reached by new immigrants.

Freshwater zooplankton metapopulations and metacommunities respond differently to environmental and spatial variation

“…Previous work has identified IBE as a dominant pattern for invertebrates (Sexton et al 2013). Patterns of IBD and IBE within zooplankton appear variable with effects varying by spatial scale for a variety of taxa (Michels et al 2001, Zeller et al 2006, Mills et al 2007, Xiang et al 2011, Orsini et al 2012, Ventura et al 2014, Haileselasie et al 2018). IBD patterns have been most frequently observed at large (>100 km) spatial scales and are frequently believed to be the result of past colonization history rather than solely the result of dispersal limitation (e.g., Zeller et al 2006, Mills et al 2007, Ventura et al 2014).…”

Optimal light conditions for Daphnia filtration

“…showing its great capacity for thermal and light adaptation. Other Daphnia species have been found at different latitudes and longitudes (Burns, 1969;Critescu et al, 2006;DeMott, 1982;Dodson et al, 1997;Filella et al, 2008;Geller and Müller, 1981; 18 Haileselasie et al, 2018;Haney, 1985;Kasprzak et al, 1999;Korinek et al, 2003;Laspoumaderes et al, 2017;Lindlholm, 2002;Okogwu, 2010;Paes et al, 2016;Rellstab and Spaak, 2007;Straile, 2000;Tessier and Goulden, 1987;Yampolsky et al, 2018;Yurista and O'Brien, 2001). Therefore, it can be expected that by extending the time of exposure to light in future experiments, further adaptations will occur in individuals of later generations.…”

Experimental evidence of rapid heritable adaptation in the absence of initial standing genetic variation

“…Low genetic diversity within populations frequently occurs and can be the result of both natural (Haileselasie et al, 2018;Louette et al, 2007;So et al, 2015) and anthropogenic processes (Roman & Darling, 2007;Schlaepfer et al, 2018). However, the long-term success of these populations is not well understood, given the potential for mismatch between phenotypes and the environment (Pérez et al, 2006).…”