Format: ORAL

Angelo Armijos-Carrion1*, Sander Boisen1, Susan Meades, Michael Burzynski3, Julissa Roncal1

1 Department of Biology, Memorial University of Newfoundland, St. John’s, Canada 2 Great Lakes Forestry Centre, Sault Ste. Marie, Ont, Canada  3 Gros Morne National Park of Canada, Parks Canada, Rocky Harbour, NL, Canada  *Corresponding author email: aarmijoscarr@mun.ca

Understanding how plant communities are assembled is critical to explaining the functioning of ecosystems and the maintenance of biodiversity. The phylogenetic distance among species in a community (i.e community phylogenetic structure) has been used to infer deterministic and stochastic assembly processes, albeit with criticisms. However, the effect of the phylogenetic scale (old versus young lineages) and spatial scale on measures of community phylogenetic structure are rarely tested, yet essential to unravel different assembly processes that might operate across species in a community. We examined clade-specific phylogenetic structure of different plant communities defined at the habitat scale, and the aggregated phylogenetic structure of communities defined at a smaller plot level scale. We obtained vascular plant species lists for six habitats in Newfoundland, Canada, and for 73 permanent 1m2 plots at Gros Morne National Park to estimate their mean pairwise phylogenetic distance standardized for sample size (SES-MPD). As expected, we found that the phylogenetic structure of plant habitats was clade-specific, with clustering at deep angiosperm nodes, overdispersion, and no pattern at both old and young lineages. Our results suggest that different lineages may exhibit different assembly processes within a habitat. As expected, at smaller spatial scales, communities showed strong phylogenetic overdispersion likely explained by processes like limiting similarity and competition.