Plant dispersal strategies of high tropical alpine communities across the Andes

Abstract

Dispersal is a key ecological process that influences plant community assembly. Therefore, understanding whether dispersal strategies are associated with climate is of utmost importance, particularly in areas greatly exposed to climate change. We examined alpine plant communities located in the mountain summits of the tropical Andes across a 4,000‐km latitudinal gradient. We investigated species dispersal strategies and tested their association with climatic conditions and their evolutionary history. We used dispersal‐related traits (dispersal mode and growth form) to characterize dispersal strategies for 486 species recorded on 49 mountain summits. Then we analysed the phylogenetic signal of traits and investigated the association between dispersal traits, phylogeny, climate and space using structural equation modelling and fourth‐corner analysis together with RLQ ordination. A median of 36% species in the communities was anemochorous (wind‐dispersed) and herbaceous. This dispersal strategy was followed by the barochory‐herb combination (herbaceous with unspecialized seeds, dispersed by gravity) with a median of 26.3% species in the communities. The latter strategy was common among species with distributions restricted to alpine environments. While trait states were phylogenetically conserved, they were significantly associated with a temperature gradient. Low minimum air temperatures, found at higher latitudes/elevations, were correlated with the prevalence of barochory and the herb growth form, traits that are common among Caryophyllales, Brassicaceae and Poaceae. Milder temperatures, found at lower latitudes/elevations, were associated with endozoochorous, shrub species mostly from the Ericaceae family. Anemochorous species were found all along the temperature gradient, possibly due to the success of anemochorous Compositae species in alpine regions. We also found that trait state dominance was more associated with the climatic conditions of the summit than with community phylogenetic structure. Although the evolutionary history of the tropical Andean flora has also shaped dispersal strategies, our results suggest that the environment had a more predominant role. Synthesis. We showed that dispersal‐related traits are strongly associated with a gradient of minimum air temperatures in the Andes. Global warming may weaken this key filter at tropical alpine summits, potentially altering community dispersal strategies in this region and thus, plant community structure and composition.

Living at the Edge: Increasing Stress for Plants 2–13 Years After the Retreat of a Tropical Glacier

“…In a context of unprecedented velocity of temperature warming, the absence of keystone, cushion-forming species dispersed by animals during the first steps of primary succession, such as A. aretioides in our sampling or D. muscoides and O. andina in the southern tropical high Andes (Zimmer et al, 2018), could influence the composition and functioning of novel alpine ecosystems on the longer terms, just as local species pool does (Schumann et al, 2016). The disproportionate abundance of wind-dispersed species in our sampled area was observable through the overwhelming majority of species being wind-dispersed (see also Erschbamer et al, 2008;Zimmer et al, 2018;Franzén et al, 2019 in other recently deglaciated terrains) whereas "only" 39% of the species in the tropical alpine regions of the Andes are expected to be dispersed by wind (Tovar et al, 2020).…”

Climate Vulnerability Assessment of the Espeletia Complex on Páramo Sky Islands in the Northern Andes

“…Range shifts presuppose niche conservatism, but also depend on the intrinsic dispersal ability of the taxa (Pelayo et al, 2019;Tovar et al, 2020). In organisms with limited seed dispersal such as Espeletia, other ways for migration are key (Cochrane et al, 2019).…”

Variation in Alpine Plant Diversity and Soil Temperatures in Two Mountain Landscapes of South Patagonia

“…Many other species, mentioned as characteristic of and exclusive to high elevation mountains in SC and TF (e.g., Moschopis rosulata, Baccharis nivalis) [39], were not found in our study. This could be due to the restricted dispersal abilities of plants in alpine environments, where there is a high prevalence of barochory [64]. However, other authors have suggested that species present in the upper limit of vegetation are controlled by the availability of safe sites for colonization, survival, and growth among rocky substrate [47].…”