Avian seed dispersal may be insufficient for plants to track future temperature change on tropical mountains

Abstract Aim: Climate change causes species’ range shifts globally.
Terrestrial plant species often lag behind temperature shifts, and it is
unclear to what extent animal-dispersed plants can track climate change.
Here, we estimate the ability of bird-dispersed plant species to track
future temperature change on a tropical mountain. Location: Tropical
elevational gradient (500–3500 m a.s.l.) in the Manú biosphere reserve,
Peru Time period: 1960–1990 to 2061–2080 Taxa: Fleshy-fruited plants,
avian frugivores Methods: Using simulations based on the functional traits
of avian frugivores and fruiting plants, we quantified the number of
long-distance dispersal (LDD) events that woody plant species would
require to track projected temperature shifts on a tropical mountain by
the year 2070 under different greenhouse gas emission scenarios (RCP 2.6,
4.5 and 8.5). We applied this approach to 343 bird-dispersed woody plant
species. Results: Our simulations reveal that bird-dispersed
plants differ in their climate-tracking ability, with large-fruited and
canopy plants exhibiting a higher climate-tracking ability. Our
simulations also suggest that even under scenarios of strong and
intermediate mitigation of greenhouse gas emissions (RCP 2.6 and 4.5),
sufficient upslope dispersal would require several LDD events by 2070,
which is unlikely for the majority of woody plant species. Furthermore,
the ability of plant species to track future temperature changes increased
in simulations with a low degree of trait matching between plants and
birds, suggesting that plants in generalised seed-dispersal systems may be
more resilient to climate change. Main conclusion: Our study illustrates
how plant and animal functional traits can inform predictive models of
species dispersal and range shifts under climate change and suggests that
the biodiversity of tropical mountain ecosystems is highly vulnerable to
future warming. The increasing availability of functional trait data for
plants and animals globally will allow parameterisation of similar models
for many other seed-dispersal systems.