Environmental Association Analysis
Temperature and precipitation are considered the driving factors that affect the population growth rate and limit the distribution of species (Cahill et al., 2014; Dalgleish, Koons, Hooten, Moffet, & Adler, 2011; Kim & Donohue, 2013). Therefore, nineteen current bioclimatic variables with a spatial resolution of 30 s were collected from WorldClim (http://www.worldclim.org/). At the same time, we recorded the GPS information of the sampling locations and downloaded the GPS information of A. viridiflorafrom CVH (http://www.cvh.ac.cn) and GBIF (http://www.gbif.org). ArcMap v.10.4 was used to limit the spatial extent according to the buffer radius (5 km) around each occurrence record. We used |r| < 0.8 (Pearson correlation coefficient) as a cutoff to remove highly correlated variables. The seven retained current bioclimatic factors (Bio1: annual mean temperature; Bio2: mean diurnal range; Bio3: isothermality; Bio4: temperature seasonality; Bio8: mean temperature of the wettest quarter; Bio15: precipitation seasonality; Bio17: precipitation of the driest quarter) were used for subsequent analysis. To identify the loci related to the seven retained current bioclimatic factors, BAYENV2 (Coop, Witonsky, Di Rienzo, & Pritchard, 2010) was used with 1,000,000 iterations and run three times separately. For each bioclimatic factor, the SNPs among the top 1% according to BF and among the top 5% according to the absolute Spearman’s ρ were considered candidates.