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

Citation

becheler, ronan et al. (2020), After a catastrophe, a little bit of sex is better than nothing: genetic consequences of a major earthquake on asexual and sexual populations, Dryad, Dataset, https://doi.org/10.5061/dryad.9kd51c5d8

Abstract

Catastrophic events can have profound effects on the demography of a population and consequently, on genetic diversity. The dynamics of post-catastrophic recovery as well as the role of sexual versus asexual reproduction in buffering the effects of massive perturbations remain poorly understood, in part because the opportunity to document genetic diversity before and after such events is rare. Six natural (purely sexual) and seven cultivated (mainly clonal due to farming practices) populations of the red alga Agarophyton chilense were surveyed along the Chilean coast before, in the days after and two years after the 8.8 magnitude earthquake in 2010. The genetic diversity of sexual populations appeared sensitive to this massive perturbation, notably through the loss of rare alleles immediately after the earthquake. By 2012, the levels of diversity returned to those observed before the catastrophe, probably due to migration. In contrast, enhanced rates of clonality in cultivated populations conferred a surprising ability to buffer the instantaneous loss of diversity. After the earthquake, farmers increased the already high rate of clonality to maintain the few surviving beds, but most of them collapsed rapidly. Contrasting fates between sexual and clonal populations suggest that betting on strict clonality to sustain production is risky, probably because this extreme strategy hampered adaptation to the brutal environmental perturbation induced by the catastrophe.

Methods

Temporal sampling of natural fixed populations (N = 7) and farms (N = 6) began in 2002, and was undertaken during the Austral summer months (i.e., January to March). Before the earthquake, sites were sampled at one or two time steps between 2002 and 2009. Sampling in 2010 was completed in March, less than one month after the earthquake. All sites were sampled in 2012.

Sampling was carried out in two Chilean regions where both A. chilense natural and farmed opulations are encountered: Concepción, heavily impacted by the earthquake of 2010 through both tsunami waves and coastal uplift (Castilla et al. 2010; Vargas et al. 2011), and Puerto Montt where this event went almost unnoticed.

DNA extractions followed the protocol recommended by Cohen et al. (2004). Due to the eventful evolutionary history of A. chilense (an initial founder event followed by recurrent demographic bottlenecks explained by overharvesting and domestication; Guillemin et al. 2014), only a few microsatellite markers have been shown to be variable in Chile (Guillemin et al. 2005). Indeed, previous studies showed that genetic diversity of A. chilense is highly reduced along the Chilean coast compared to the species region of origin (New Zealand) probably because of the combined effects of the founding event (that likely took place at the end of the Quaternary) and the recent human impacts of harvesting and cultivation practices (Guillemin et al. 2014). PCR amplification of five microsatellite loci and allele size scoring were performed according to Guillemin et al. (2005). For loci 2B2, 6C7, 7F12 and 8B2 (locus names follow Guillemin et al. 2005), PCR products were visualized on an ABI 3100 Sequencer fragment analyzer (Applied Biosystem, Foster City, CA, USA). For the locus 7D3 (Guillemin et al. 2005), PCR products were run on 6.5% polyacrylamide denaturing gels in a LI-COR DNA sequencer model 4200TM (LI-COR, Lincoln, NE, USA). For all five loci, PCR products of five to ten individuals already genotyped for the study of Guillemin et al. (2008) were scored jointly with the new samples to ensure correspondence in allele size between temporal sampling. A second and third round of PCR and electrophoresis were performed for individuals with missing data.

Usage Notes

No missing data. All information is avalaible with this dataset and the related article. In case, you can contact the corresponding author of the related article. 

Funding

Fondo Nacional de Desarrollo Científico y Tecnológico, Award: 1130868

Fondo Nacional de Desarrollo Científico y Tecnológico, Award: 1170541

Agence Nationale de la Recherche, Award: ANR-10-BTBR-04

Agence Nationale de la Recherche, Award: ANR-11-BSV7-007