Incorporating latitudinal and central–marginal trends in assessing genetic variation across species ranges
The genetic variation across a species’ range is an important factor in speciation and conservation, yet searching for general patterns and underlying causes remains challenging. While the majority of comparisons between central and marginal populations have revealed a general central–marginal (C-M) decline in genetic diversity, others show no clear pattern. Similarly, most latitudinal studies (although much fewer, especially those conducted rangewide) also showed latitudinal trends in genetic variation. To date, the C-M and latitudinal patterns have often been examined independently and have rarely been considered together when accounting for the observed genetic variation across species ranges. Here, in the light of the most recent findings, I show how latitude might be responsible for some of the deviations from the general C-M trends in genetic diversity, and vice versa. In the future, integrating latitude and range geometry with climate-induced species migration would offer important insights into conservation prioritization across species ranges.