Data from: Geography and ecology shape the phylogenetic composition of Amazonian tree communities

Aim: Amazonia hosts more tree species, from numerous evolutionary lineages
both young and ancient, than any other biogeographic region. Previous
studies have shown that tree lineages colonised multiple edaphic
environments and dispersed widely across Amazonia, leading to a
hypothesis, which we test, that lineages should not be strongly associated
with either geographic regions or edaphic forest types. Location:
Amazonia. Taxon: Angiosperms (Magnoliids; Monocots; Eudicots). Methods:
Data for the abundance of 5,082 tree species in 1,989 plots were combined
with a mega-phylogeny. We applied evolutionary ordination to assess how
phylogenetic composition varies across Amazonia. We used variation
partitioning and Moran’s eigenvector maps (MEM) to test and quantify the
separate and joint contributions of spatial and environmental variables to
explain the phylogenetic composition of plots. We tested the indicator
value of lineages for geographic regions and edaphic forest types and
mapped associations onto the phylogeny. Results: In the terra firme and
várzea forest types, phylogenetic composition varies by geographic region,
but the igapó and white-sand forest types retain a unique evolutionary
signature regardless of region. Overall, we find that soil chemistry,
climate, and topography explain 24% of the variation in phylogenetic
composition, with 79% of that variation being spatially structured (R 2 =
19% overall for combined spatial/environmental effects). Phylogenetic
composition also shows substantial spatial patterns not related to the
environmental variables we quantified (R 2 = 28%). A greater number of
lineages were significant indicators of geographic regions than forest
types. Main conclusions: Numerous tree lineages, including some ancient
ones (>66 Ma), show strong associations with geographic regions and
edaphic forest types of Amazonia. This shows that specialization on
specific edaphic environments has played a long-standing role in the
evolutionary assembly of Amazonian forests. Furthermore, many lineages,
even those that have dispersed across Amazonia, dominate within a specific
region, likely because of phylogenetically conserved niches for
environmental conditions that are prevalent within regions.