Genomic data reveal a loss of diversity in two species of tuco-tucos (genus Ctenomys) following a volcanic eruption

Abstract

Marked reductions in population size can trigger corresponding declines in genetic variation. Understanding the precise genetic consequences of such reductions, however, is often challenging due to the absence of robust pre- and post-reduction datasets. Here, we use heterochronous genomic data from samples obtained before and immediately after the 2011 eruption of the Puyehue-Cordón Caulle volcanic complex in Patagonia to explore the genetic impacts of this event on two parapatric species of rodents, the colonial tuco-tuco (Ctenomys sociabilis) and the Patagonian tuco-tuco (C. haigi). Previous analyses using microsatellites revealed no post-eruption changes in genetic variation in C. haigi, but an unexpected increase in variation in C. sociabilis. To explore this outcome further, we used targeted gene capture to sequence over 2,000 putatively neutral regions for both species. Our data revealed that, contrary to the microsatellite analyses, the eruption was associated with a small but significant decrease in genetic variation in both species. We suggest that genome-level analyses provide greater power than traditional molecular markers to detect the genetic consequences of population size changes, particularly changes that are recent, short-term, or modest in size. Consequently, genomic analyses promise to generate important new insights into the effects of specific environmental events on demography and genetic variation.

Ecological and demographic impacts of a recent volcanic eruption on two endemic patagonian rodents

“…Collectively, these findings lead us to expect that post-eruption genetic variability in each population should also have been reduced. Analyses of pre- and post-eruption samples from the study species using a genome-wide panel of single nucleotide polymorphisms (SNPs) support this prediction, revealing small but significant decreases in genetic variability in both study populations [28]. These findings indicate that abrupt reductions in population size of the magnitude reported here (25–50%) can produce significant changes in genetic variability over short time scales.…”

“…Previous studies [27, 28] have revealed that the 2011 eruption affected levels of genetic variability in both study species and a primary objective of our analyses was to identify the demographic parameters that may have contributed to these changes in genetic variation. Loss of genetic variability following anthropogenically-induced bottlenecks has been documented for a number of mammalian species, including elephant seals [41], fur seals [42], black-footed ferrets [43], arctic foxes [44], lions [45], and Florida panthers [46].…”

“…haigi that have been the focus of long-term study were also subject to extensive ash fall, providing a rare opportunity to assess directly the consequences of a severe environmental event on natural populations of native vertebrates. Analyses of different molecular markers have revealed contrasting information regarding post-eruption changes in genetic variability in these populations [27,28], highlighting the need for more detailed exploration of the effects of the eruption on the demography each study species. To identify the specific population parameters contributing to changes in genetic variation and, more generally, to characterize the immediate demographic consequences of the eruption on these animals, we compared pre- and post-eruption values for multiple elements of population structure including survival, offspring production, and juvenile recruitment.…”

After a catastrophe, a little bit of sex is better than nothing: Genetic consequences of a major earthquake on asexual and sexual populations

“…This is in line with former studies revealing an increased weight of the migration after disturbance that provide opportunities for recruitment (Becheler, Benkara, Moalic, Hily, & Arnaud‐Haond, 2014; Becheler, Diekmann, Hily, Moalic, & Arnaud‐Haond, 2010; Eriksson, 1993; Reusch, 2006). Increase in available open space lead, in some extreme cases, to mosaic patterns where impacted areas colonized by external sources are genetically distinct from the surviving local patches (Parvizi, Craw, & Waters, 2019) or to a reset of the genetic composition (Hsu et al, 2017; Wilmer et al, 2011) after the near‐total crash of populations. The surprising consequences of such profound genetic reset rely in a resulting diversity comparable to the original one, as the rapid recolonization is achieved through intense long‐distance migration (i.e., migration pool model), bringing new migrants and alleles in impacted populations.…”

“…Indeed, most studies have focused on the consequences of a catastrophic event on genetic structure by analyzing the impacted populations a posteriori (Jacquemyn, Roldán‐Ruiz, & Honnay, 2010; Russello, Gladyshev, Miquelle, & Caccone, 2004) or sometimes benefitting from banks of ancient data (e.g., data from museum specimens: Nyström, Angerbjörn, & Dalén, 2006; archeological data: Hadly et al, 2004; Weber, Stewart, & Lehman, 2004). Population‐based studies in which information was gathered before and after the extreme event in order to quantify the changes in genetic diversity caused by the catastrophe are rare (but see Gallardo, Köhler, & Araneda, 1995; Hsu et al, 2017; Pujolar et al, 2011; Wilmer et al, 2011). These studies have reported a loss of genetic diversity by directly comparing the standing variation before and after the event.…”