Predictors of Phylogeographic Structure among co-distributed taxa across
the complex Australian Monsoonal Tropics
Abstract
Differences in the geographic scale and depth of phylogeographic
structure across co-distributed taxa can reveal how microevolutionary
processes such as population isolation and persistence drive
diversification. In turn, environmental heterogeneity, species’ traits
and historical biogeographic barriers may influence the potential for
isolation and persistence. Using extensive SNP data and a combination of
population genetic summary statistics and landscape genomic analyses, we
explore predictors of the scale and depth of phylogeographic structure
in co-distributed lizard taxa from the topographically and climatically
complex monsoonal tropics (AMT) of Australia. We first resolve
intraspecific lineages and then test whether genetic divergence across
space within lineages is related to isolation by distance, resistance
and/or environment, and whether these factors differ across genera or
between rock-related versus habitat generalist taxa. We then test
whether microevolutionary processes within lineages explain differences
in the geographic scale and depth of intraspecific phylogeographic
lineages. Results indicate that landscape predictors of phylogeographic
structure differ between taxa. Within lineages, there was prevalent
isolation by distance, but the strength of isolation by distance is
independent of the taxonomic family, habitat specialization and climate.
Isolation by environment is the strongest predictor of landscape-scale
genetic divergence for all taxa, with both temperature and precipitation
acting as limiting factors. The strength of isolation by distance does
not predict the geographic scale of phylogeographic structure. However
localized lineages had higher mean individual heterozygosity and less
negative Tajima’s D. This implies that finer-scale phylogeographic
structuring within species is associated with larger and more stable
populations and, hence, persistence.