Records of urban occurrences expand estimates of the climate niches in tree species

Abstract

AbstractAimQuantifying a species' climate niche is often the first step to determining potential sensitivity to climate change. This process typically relies on native occurrence records, assuming that these reflect the breadth of a species' climatic requirements. Yet, many species survive in non‐native regions with climates beyond their native range. Identifying their characteristics could help to better elucidate responses to climate change. Here, we use an extensive data set of urban street tree and native range records for 566 tree species to assess differences between species native and urban climate niches and whether niche differences are predictable given characteristics of species native ranges.LocationGlobal.Time Period1970–2020.Major Taxa StudiedTree species.MethodsMultivariate niche estimations were undertaken using eight climate variables. Calculations included the size of species' urban and native niches, overlap and direction of shift. Relationships between niches and native range attributes (temperature and precipitation breadth, range size, Köppen Geiger subclasses occupied) were calculated using multiple linear regression.Results83% of tree species studied had significantly larger urban niches compared to native niches. Species with narrow geographic ranges demonstrated greater mismatch between their two niches, and the direction of niche shift was associated with their native range Köppen Geiger zone. For example, species native to the wet tropics tend to be planted in cooler, drier urban spaces; those native to cold regions are planted in warmer urban spaces.Main ConclusionNative range occurrences may poorly reflect the breadth of climatic conditions a species can tolerate—particularly for species with narrow geographic ranges. For some species, Köppen Geiger zones may be a useful proxy to help understand sensitivity to climate change. Accounting for possible plasticity in tree species to climate can improve our understanding of their sensitivity and adaptive capacity to climate change.