Vegetation survey data to understand drivers of plant rarity

Determining the drivers of plant rarity is a major challenge in ecology.
Analysing spatial associations between different plant species can provide
an exploratory avenue for understanding the ecological drivers of plant
rarity. Here, we examined the different types of spatial associations
between rare and common plants to determine if they influence the
occurrence patterns of rare species. We completed vegetation surveys at 86
sites in woodland, forest, and heath communities in south-east Australia.
We also examined two different rarity measures to quantify how
categorisation criteria affected our results. Rare species were more
likely to have positive associations with both rare and common species
across all three vegetation communities. However, common species had
positive or negative associations with rare and other common species,
depending on the vegetation community in which they occurred. Rare species
were positively associated with species diversity in forest communities.
In woodland communities, rare species were associated negatively with
species diversity but positively associated with species evenness. Rare
species with high habitat specificity were more clustered spatially than
expected by chance. Efforts to understand the drivers of plant rarity
should use rarity definitions that consider habitat specificity. Our
findings suggest that examining spatial associations between plants can
help understand the drivers of plant rarity.