Functional biogeography of angiosperms: life at the extremes

Abstract

Nonlinear relationships between species and their environments are believed common in ecology and evolution, including during angiosperms' rise to dominance. Early angiosperms are thought of as woody evergreens restricted to warm, wet habitats. They have since expanded into numerous cold and dry places. This expansion may have included transitions across important environmental thresholds. To understand linear and nonlinear relationships between angiosperm structure and biogeographic distributions, we integrated large datasets of growth habits, conduit sizes, leaf phenologies, evolutionary histories, and environmental limits. We consider current-day patterns and develop a new evolutionary model to investigate processes that created them. The macroecological pattern was clear: herbs had lower minimum temperature and precipitation limits. In woody species, conduit sizes were smaller in evergreens and related to species' minimum temperatures. Across evolutionary timescales, our new modeling approach found conduit sizes in deciduous species decreased linearly with minimum temperature limits. By contrast, evergreen species had a sigmoidal relationship with minimum temperature limits and an inflection overlapping freezing. These results suggest freezing represented an important threshold for evergreen but not deciduous woody angiosperms. Global success of angiosperms appears tied to a small set of alternative solutions when faced with a novel environmental threshold.

Tunicate bulb size variation in monocots explained by temperature and phenology

“…Herbaceous plants in general tend to inhabit colder and/or drier habitats compared to their woody relatives (Zanne et al, 2014(Zanne et al, , 2018.…”

Diversification, adaptation, and community assembly of the American oaks (Quercus), a model clade for integrating ecology and evolution

“…Plant ecologists interested in comparative approaches rarely focus on clades, tending instead to work at broad phylogenetic scales. Important advances have been made at these large scales in examining the evolutionary mechanisms for trait coordination along major axes of life history variation, such as the leaf economic spectrum (Ackerly & Reich, ; Wright et al ., ; Moles et al ., ; Kerkhoff et al ., ; Donovan et al ., ), freezing adaptation (Zanne et al ., , ), or mechanisms of seed dormancy (Willis et al ., ). Yet working within highly resolved lineages is often critical to deciphering the ecological causes and direction of evolutionary shifts, given that evolutionary processes occur at smaller scales where species do not exhibit the extreme phenotypes observed across the entire evolutionary tree (Scoffoni et al ., ).…”

Climatic seasonality is linked to the occurrence of the mixed evergreen and deciduous broad‐leaved forests in China

“…Latitudinal shifts in the relative roles of these two temperature variables drive the formation of mixed forest. Tree species of different leaf habits can adapt and/or acclimatize to these temperature conditions differentially, which thus alter the respective competitive performance of tree species within forests and formations of our targeted mixed forest (Woodward et al 2004, Liang et al 2013, Zanne et al 2018. In other words, evergreen broad-leaved tree species and deciduous broad-leaved tree species respond to climate in unique ways, especially to temperature variables.…”

“…, Zanne et al. ). Considerable research effort has revealed that the evergreenness (or deciduousness) of tree species is tightly linked with climate‐related variables.…”