2.6 Isolation by distance and isolation by phenotype
We investigated whether the genetic structure of A. buergerianavar. buergeriana reflects geographic distance or trait differences. In general, populations separated by greater distances are more genetically differentiated than populations close together (Wright, 1943). On the other hand, if populations with similar traits are also genetically similar, then we can expect to find a correlation between differences in traits between populations and the degree of genetic differentiation. We used GenoDive software version 3.0 (Meirmans, 2020) to calculate the genetic isolation (F ST) between populations. The geographic distance between populations was calculated from the latitude and longitude of the populations, and the difference in the average spur length of each population was used as the trait difference. We calculated the relationship between pairwiseF ST orF ST/(1 – F ST) and geographic distance between populations, as well as the relationship between pairwiseF ST or F ST/(1 –F ST) and trait difference between populations, following methods in Rousset (1997) and Noutsos et al. (2014). The relationship between genetic isolation and geographic or trait distance was tested by Mantel tests using the R package ”ade4” with 10,000 Monte-Carlo permutations.