Evolutionary potential under heat and drought stress at the southern range edge of North American Arabidopsis lyrata

The warm edges of species’ distributions are vulnerable to global warming.
Evidence is the recent range retraction from there found in many species.
It is unclear why populations cannot easily adapt to warmer, drier, or
combined hot and dry conditions and locally persist. Here, we assessed the
ability to adapt to these stressors in the temperate species Arabidopsis
lyrata. We grew plants from replicate seed families of a central
population with high genetic diversity under a temperature and
precipitation regime typical of the low-latitude margin or under hotter
and/or drier conditions within naturally occurring amplitudes. We then
calculated genetic variance-covariance (G-) matrices of traits depicting
growth and allocation as well as selection vectors to compare the
predicted adaptation potential under the different climate-stress regimes.
We found that the sum of genetic variances and genetic correlations were
not significantly different under stress as compared to benign conditions.
However, under drought and heat drought, the predicted ability to adapt
was severely constrained due to strong selection and selection pointing in
a direction with less multivariate genetic variation. The much-reduced
ability to adapt to dry and hot-dry conditions is likely to reduce the
persistence of populations at the low-latitude margin of the species’
distribution and contribute to the local extinction of the species under
further warming.