Network analysis of migration pattern
To quantify the proportion and direction of recent migration patterns
among populations in small and large patches, relative migration levels
(Nm ) were estimated between populations calculated based on
neutral SNPs using the GST and Nmparameters (Sundqvist et al., 2016) with the divMigrate function
of the R package diveRsity (Keenan et al., 2013). This approach
permits the determination of migration directional differences between
genetically structured populations, where deterministic extinction and
density-dependent processes govern source-sink population dynamics
(i.e., metapopulation structure). Relative migration network analysis
was estimated using only the complete dataset, as the probability of
assigning the correct migration direction is directly related to the
increase in the number of samples and loci in the dataset (Sundqvist et
al., 2016). The direction and magnitude of recent migration patterns
were summarized as a network from the significant estimated effective
number of migrants (Nm ) based on 1000 bootstrap interactions and
with a filter threshold of 0.35. Network graphics were generated using
the qgraph R package (Epskamp
et al., 2012).