Genetically informed ecological niche models improve climate change predictions

TLDR

Local adaptation is common across environmental gradients, and common garden studies show a covariance between neutral markers and functional traits linked to a species’ ability to adapt to environmental change. The study hypothesizes that incorporating population genetic structure into ecological niche models improves species distribution predictions, predicts that genetically distinct populations will respond differently to climate change with little overlap, and tests this by creating genetically informed ENMs for Populus fremontii. They developed genetically informed ecological niche models (gENMs) for Populus fremontii by integrating population genetic structure and evidence of local adaptation from common garden experiments. gENMs predicted population occurrences up to 12‑fold more accurately than models without genetic information, revealed distinct ecotypes with climate‑associated differences, forecasted further geographic separation of ecotypes under climate change, and suggested that ecotypes with larger distributions and niche breadth are most buffered, supporting the claim that gENMs improve distribution predictions under climate change.

Abstract

We examined the hypothesis that ecological niche models (ENMs) more accurately predict species distributions when they incorporate information on population genetic structure, and concomitantly, local adaptation. Local adaptation is common in species that span a range of environmental gradients (e.g., soils and climate). Moreover, common garden studies have demonstrated a covariance between neutral markers and functional traits associated with a species' ability to adapt to environmental change. We therefore predicted that genetically distinct populations would respond differently to climate change, resulting in predicted distributions with little overlap. To test whether genetic information improves our ability to predict a species' niche space, we created genetically informed ecological niche models (gENMs) using Populus fremontii (Salicaceae), a widespread tree species in which prior common garden experiments demonstrate strong evidence for local adaptation. Four major findings emerged: (i) gENMs predicted population occurrences with up to 12-fold greater accuracy than models without genetic information; (ii) tests of niche similarity revealed that three ecotypes, identified on the basis of neutral genetic markers and locally adapted populations, are associated with differences in climate; (iii) our forecasts indicate that ongoing climate change will likely shift these ecotypes further apart in geographic space, resulting in greater niche divergence; (iv) ecotypes that currently exhibit the largest geographic distribution and niche breadth appear to be buffered the most from climate change. As diverse agents of selection shape genetic variability and structure within species, we argue that gENMs will lead to more accurate predictions of species distributions under climate change.