Uniting genetic and geographic databases to understand the relationship
between latitude and population demography
Abstract
Conducting large-scale phylogeographic studies to understand processes
affecting population structure and genetic diversity across multiple
species is difficult because the key genetic (NCBI) and spatial (GBIF)
repositories are disconnected. In this issue of Molecular Ecology
Resources, Pelletier et al. (2022) demonstrate the power of connecting
these in the program phylogatR. This program assembled 87,852 species
and 102,268 sequence alignments in a taxonomic hierarchy, yielding
multiple sequence alignments per species, mainly for animals (88%),
composed mostly of mtDNA data. The authors discuss several caveats with
these alignments and provide flags identifying particular problems
associating locality and genetic data with certain taxa (e.g., multiple
localities per individuals). They provide a test that nucleotide
diversity should increase with area, but find a significant relationship
in only 32% of taxa with no clear taxonomic or ecological factors
accounting for this. To examine the potential of this program, I tested
the idea that the degree of population expansion should increase with
latitude given potential environmental stability in the tropics and
instability in temperate regions. In under two hours, I downloaded all
squamates (lizards and snakes) and regressed Tajima’s D on latitude and
found a weak but significant negative relationship, indicating a
potential association between latitude and population expansion. The
phylogatR database is a powerful resource for researchers wanting to
test the relationship between genetic diversity and some aspect of space
or environment.