Climate‐driven extinctions shape the phylogenetic structure of temperate tree floras

Abstract

When taxa go extinct, unique evolutionary history is lost. If extinction is selective, and the intrinsic vulnerabilities of taxa show phylogenetic signal, more evolutionary history may be lost than expected under random extinction. Under what conditions this occurs is insufficiently known. We show that late Cenozoic climate change induced phylogenetically selective regional extinction of northern temperate trees because of phylogenetic signal in cold tolerance, leading to significantly and substantially larger than random losses of phylogenetic diversity (PD). The surviving floras in regions that experienced stronger extinction are phylogenetically more clustered, indicating that non-random losses of PD are of increasing concern with increasing extinction severity. Using simulations, we show that a simple threshold model of survival given a physiological trait with phylogenetic signal reproduces our findings. Our results send a strong warning that we may expect future assemblages to be phylogenetically and possibly functionally depauperate if anthropogenic climate change affects taxa similarly.

Extinction risk of North American seed plants elevated by climate and land‐use change

“…Phylogenetic niche conservatism may therefore result in greater risk for certain parts of the tree of life (Eiserhardt et al . ). However, existing assessments between phylogenetic diversity and climate change do not generally lead to consistent results, with some showing no phylogenetically biased extinction risk (Thuiller et al .…”

“…) and others strong phylogenetic signals (Eiserhardt et al . ). This may be due to the difference in spatial scale and phylogenetic breadth in different analyses.…”

Region effects influence local tree species diversity

“…However, if unique historical and biogeographic features of each region influenced within-region diversification and extinction (8)(9)(10), these regionspecific effects might contribute to the global pattern in local species richness. Efforts to disentangle these effects have met with limited success and have led to a long-standing discussion of the relationship between local and regional diversity (6,(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21).…”

Greater tree species richness in eastern North America compared to Europe is coupled to denser, more clustered functional trait space filling, not to trait space expansion

“…Here is important to highlight that Svenning (2003) and Eiserhardt et al (2015) suggested that the loss of these species in Europe could be related to selectivity regarding cold and drought tolerance. The clustering within the European trait space of species from genera lost in Neogene and Quaternary Extinctions but still present in North America signpost the functional resilience of temperate tree floras to large environmental changes.…”

“…Multiple studies on the subject have focused on evaluating how the division of resources amongst co-occurring species or the balance between species accumulation processes (diversification, extinction, and dispersal limitation) determines species richness differences between regions (Eiserhardt, Borchsenius, Plum, Ordonez, & Svenning, 2015;Latham & Ricklefs, 1993;Qian & Ricklefs, 2000;Ricklefs, Schwarzbach, & Renner, 2006). Multiple studies on the subject have focused on evaluating how the division of resources amongst co-occurring species or the balance between species accumulation processes (diversification, extinction, and dispersal limitation) determines species richness differences between regions (Eiserhardt, Borchsenius, Plum, Ordonez, & Svenning, 2015;Latham & Ricklefs, 1993;Qian & Ricklefs, 2000;Ricklefs, Schwarzbach, & Renner, 2006).…”