Genetics and ecology do not agree in reconstructing how birds reacted to past climate changes

A new paper in which I took part is now available in Molecular Ecology

Eleanor F. Miller, Rhys E. Green, Andrew Balmford, Pierpaolo Maisano Delser, Robert Beyer, Marius Somveille, Michela Leonardi, William Amos, Andrea Manica
Bayesian Skyline Plots disagree with range size changes based on Species Distribution Models for Holarctic birds
Molecular Ecology, Volume 30, Issue 16 August 2021 Pages 3993-4004

We analysed more than 100 species of Holarctic birds finding that genetics and ecology do not agree in reconstructing how more they reacted to past climatic fluctuations.

Why should we care? The reconstructions compared in our paper (one based on genetic data, the other on ecological modelling) are widely used to assess how well species can react to the ongoing climate emergency.

In our study, we show that when we systematically compare them for a lot of species they tend to tell us quite different stories. This does not mean that they are wrong: different methods are based on different assumptions, and each of them is likely to be missing a small but significant part of the whole story.

So, when we use these methods, the key is interdisciplinarity: integrating into the analyses different lines of evidence help tackle these limitations and get more reliable results.

Article

Abstract

During the Quaternary, large climate oscillations impacted the distribution and demography of species globally. Two approaches have played a major role in reconstructing changes through time: Bayesian Skyline Plots (BSPs), which reconstruct population fluctuations based on genetic data, and Species Distribution Models (SDMs), which allow us to back-cast the range occupied by a species based on its climatic preferences. In this paper, we contrast these two approaches by applying them to a large data set of 102 Holarctic bird species, for which both mitochondrial DNA sequences and distribution maps are available, to reconstruct their dynamics since the Last Glacial Maximum (LGM). Most species experienced an increase in effective population size (N_e, as estimated by BSPs) as well as an increase in geographical range (as reconstructed by SDMs) since the LGM; however, we found no correlation between the magnitude of changes in N_e and range size. The only clear signal we could detect was a later and greater increase in N_e for wetland birds compared to species that live in other habitats, a probable consequence of a delayed and more extensive increase in the extent of this habitat type after the LGM. The lack of correlation between SDM and BSP reconstructions could not be reconciled even when range shifts were considered. We suggest that this pattern might be linked to changes in population densities, which can be independent of range changes, and caution that interpreting either SDMs or BSPs independently is problematic and potentially misleading.