Vascular plant assemblages of ephemeral wetland vegetation along the Mediterranean-temperate gradient in Chile

Resumo

Plant species composition and geographical distribution of vernal pools in Mediterranean Chile are poorly studied. In
order to overcome this gap we collected 73 floristic samples in the Mediterranean-temperate gradient from Chile (31-
44°S). Additionally, we carried out an exhaustive collection of published phytosociological relevés made in this area
including some relevés from the East side of the Andes in Argentina. The resulting dataset contains 228 observations of
269 species. Hierarchical clustering was applied in order to get co-occurrence assemblages. These sets were compared with
diagnostic groups defined a priori, life forms and their status in South America (introduced vs native species). In order to
detect geographic and climatic distribution patterns of the assemblages, we extracted climatic summary variables from
the WorldClim database and performed a principal component analysis (PCA). We detected seven species assemblages
with a significant correspondence to diagnostic groups defined a priori (P < 0.01), though their association is relatively
low (Cramér’s V = 0.49). Native species dominate over adventive ones in each assemblage suggesting low risk of outcompetition
by introduced species adapted to these habitats. The annual life form is over represented in most of the cooccurrence
groups. Despite the huge temperature and precipitation gradient in the studied transect, plant assemblages
are occurring almost along the whole range, supporting the hypothesis of azonality (low dependence on macro-climate).
Assemblages defined in this work can be potentially used for further supervised classification strategies in order to define
plant community types within vernal pool vegetation.