Influence of climate factors on the global dynamic distribution of Tsuga (Pinaceae)

Abstract

Throughout the Quaternary period, climate change has significantly influenced plant distribution, particularly affecting species within the genus Tsuga (Endl.) Carrière. This climatic impact ultimately led to the extinction of all Tsuga species in Europe. Today, there are ten recognized species of Tsuga worldwide, one of listed as a vulnerable species and four as near-threatened species. The genus Tsuga exhibits a disjunctive distribution in East Asia (EA), eastern North America (ENA), and western North America (WNA). It is crucial to comprehend the mechanisms underlying these distributional changes and to identify key climate variables to develop effective conservation strategies for Tsuga under future climate scenarios. In this study, we applied the maximum entropy (MaxEnt) model by combining distribution data for Tsuga with abundant pollen fossil data. Our objective was to investigate the climate factors that shape the distribution of Tsuga, identify climate thresholds, and elucidate distribution dynamics in the context of significant climate changes over the past 1070 thousand years (ka). Our findings highlight the pivotal role of precipitation as the key climate factor affecting the distribution of Tsuga. Specifically, in EA, summer precipitation was the key driver, while in North America (NA), winter precipitation exerted greater importance. Moreover, we observed similarities in climatic requirements between Tsuga species in Europe and EA, and declines in summer precipitation and winter temperature were major factors contributing to the extinction of Tsuga species in Europe. Quaternary glacial and interglacial fluctuations exerted substantial impacts on Tsuga distribution dynamics. The disappearance of Tsuga species in the Korean Peninsula may have occurred during the LGM (Last Glacial Maximum). The potential suitable area for Tsuga species in EA expanded during the cold periods, while in NA, it contracted. In the future, climate change may result Tsuga distribution area contraction in both the EA and NA. Our study has identified distinct response patterns of Tsuga in various geographic regions to Quaternary climate change and offers corresponding suggestions for Tsuga conservation. In the future, it will be imperative to prioritize the conservation of natural Tsuga distributions in EA and NA, with a focus on the impacts of precipitation fluctuation on the dynamic distribution of this genus.