Climate‐driven range shifts are stochastic processes at a local level: two flying squirrel species in Maine

Abstract

Numerous directional range shifts have been linked to climate change, but mechanistic explanations are frequently absent. In North America, southern flying squirrel (Glaucomys volans) range has expanded northward as a result of climate change, and northern flying squirrel (G. sabrinus) range has shifted north, likely in response to competition. We tracked both species abundances as well as climate, food availability, and forest structure over 31 yr, and found complete species turnover from G. sabrinus to G. volans in 18 yr. We tested multiple generalized least squares models of each species' abundance over time. The top model for G. sabrinus indicated that abundance was likely shaped by the arrival of G. volans, a competitor and known vector of a pathological nematode, food, and modest anthropogenic changes to forest structure; the top model for G. volans suggested that warm winters coinciding with high mast years likely facilitated the initial establishment of G. volans, whereas positive density dependence likely shaped subsequent population dynamics. The only significant change to local climate was an increase in minimum summer temperature, which would enhance the survival of Strongyloides robustus, the nematode carried by G. volans and detrimental to G. sabrinus. This complex suite of interactions suggests that at a local level, range shifts may be a largely stochastic process permitted by the temporal coincidence of multiple species‐ and site‐specific factors.

Adjusting the lens of invasion biology to focus on the impacts of climate-driven range shifts

“…Range shifters encountering new species can have significant impacts on recipient communities through changes to biotic processes, such as predation, competition and the transmission of new parasites or pathogens. In North American forests, the southern flying squirrel (Glaucomys sabrinus) is displacing the smaller northern flying squirrel (Glaucomys volans) as the southern species expands its range in response to increasing temperatures 62 . In addition to being superior competitors, southern flying squirrels are carriers of an intestinal parasite that is deadly to northern flying squirrels 63,64 .…”

A de novo genome assembly and annotation of the southern flying squirrel (Glaucomys volans)

“…The copyright holder for this preprint (which this version posted June 9, 2021. ; https://doi.org/10.1101/2021.06.09.447775 doi: bioRxiv preprint zones across a latitudinal gradient between southern (Glaucomys volans) and northern (Glaucomys sabrinus) flying squirrels (Garroway et al 2010;Rogic et al 2016). Interspecific hybridization is a key conservation concern for these flying squirrel species, as population declines among northern flying squirrels have been noted in some areas of the USA, where some populations are endangered (Wood et al 2016). The potential for introgressive hybridization and the subsequent ecological and fitness consequences necessitates a holistic assessment of species biology in the Glaucomys hybrid zone.…”

Ultrasonic Acoustic Surveys of State Endangered Northern Flying Squirrels in the Pocono Mountains, Pennsylvania

“…Species are predicted to shift their distributions upwards in elevation or poleward in latitude due to climate change (Walther et al 2002), making species in mountainous regions at more southern latitudes or at the southern extent of their range more vulnerable to range contractions (Guralnick 2006). These trends have already been observed in flying squirrels, where NFS are experiencing range contractions and SFS are experiencing range expansion (Myers et al 2009;Garroway et al 2011;Wood et al 2016). The rates of expansion with climate change may accelerate with an increasingly warming climate (Chen et al 2011) and a method that can rapidly assess shifts in species distribution is needed.…”