Genetic evidence for widespread population size expansion in North American boreal birds prior to the Last Glacial Maximum

Abstract

Pleistocene climate cycles are well documented to have shaped contemporary species distributions and genetic diversity. Northward range expansions in response to deglaciation following the Last Glacial Maximum (LGM; approximately 21 000 years ago) are surmised to have led to population size expansions in terrestrial taxa and changes in seasonal migratory behaviour. Recent findings, however, suggest that some northern temperate populations may have been more stable than expected through the LGM. We modelled the demographic history of 19 co-distributed boreal-breeding North American bird species from full mitochondrial gene sets and species-specific molecular rates. We used these demographic reconstructions to test how species with different migratory strategies were affected by glacial cycles. Our results suggest that effective population sizes increased in response to Pleistocene deglaciation earlier than the LGM, whereas genetic diversity was maintained throughout the LGM despite shifts in geographical range. We conclude that glacial cycles prior to the LGM have most strongly shaped contemporary genetic diversity in these species. We did not find a relationship between historic population dynamics and migratory strategy, contributing to growing evidence that major switches in migratory strategy during the LGM are unnecessary to explain contemporary migratory patterns.

Revealing the Demographic History of the European nightjar (Caprimulgus europaeus).

“…Our results contribute to the growing consensus that long distance migratory behaviour in contemporary Western-Palearctic avifauna predates the LGM (i.e. Ponti et al, 2020;Ralston et al, 2021;Thorup et al, 2021;Kimmitt et al, 2023).…”

“…The dramatically fluctuating N e prior to the LGM throughout the Pleistocene may reflect periods of significant population expansion and contraction associated with climate driven changes in temperate breeding habitat availability (Ponti et al, 2020). If nightjar had exhibited a sedentary Afrotropic distribution prior to the LGM we might expect to see less severe fluctuation inN e relative to global climate change (Kimmitt et al, 2023; but see Speckled mousebird; Colius striatus in Nadachowska-Brzyska et al, 2015). Similarly, if migratory behaviour had not developed until ˜20,000 ya, we would expect divergence between populations to occur exclusively post-LGM.…”

Population genetics and ecological niche modelling provide insights into management strategies of the herbivorous pest Phytomyza horticola (Diptera: Agromyzidae)

“…In Europe and North America, faunal population demographic histories and changes in suitable habitats are often closely related to Pleistocene glacial cycles (Hewitt, 2000;Kimmitt et al, 2023;Kotsakiozi et al, 2018;Ye et al, 2022) Gasse, 2000). In this study, four lines of evidence (haplotype network characteristics and demographic history inference) indicate a recent rapid expansion in the P. horticola population size.…”

“…In Europe and North America, faunal population demographic histories and changes in suitable habitats are often closely related to Pleistocene glacial cycles (Hewitt, 2000; Kimmitt et al, 2023; Kotsakiozi et al, 2018; Ye et al, 2022). Species from different habitat types in China have also exhibited diverse responses to late Pleistocene climate change.…”

Population genetic consequences of the seasonal migrations of birds

“…Our analyses reveal that boreal bird species vary considerably in spatial population genetic patterns and genetic diversity despite their common landscape and broadly similar histories in the region (38) (Fig. 2, Fig.…”