Resumen:
We investigated how the phylogenetic structure of Amazonian plant communities
varies along an edaphic gradient within the non-inundated forests. Forty localities
were sampled on three terrain types representing two kinds of soil: clayey soils of
a high base cation concentration derived from the Solimões formation, and loamy
soils with lower base cation concentration derived from the Içá formation and al luvial terraces. Phylogenetic community metrics were calculated for each locality
for ferns and palms both with ferns as one group and for each of three fern clades
with a crown group age comparable to that of palms. Palm and fern communities
showed significant and contrasting phylogenetic signals along the soil gradient. Fern
species richness increased but standard effect size of mean pairwise distance (SES.
MPD) and variation of pairwise distances (VPD) decreased with increasing soil base
cation concentration. In contrast, palm communities were more species rich on less
cation-rich soils and their SES.MPD increased with soil base cation concentration.
Species turnover between the communities reflected the soil gradient slightly better
when based on species occurrences than when phylogenetic distances between the
species were considered. Each of the three fern subclades behaved differently from
each other and from the entire fern clade. The fern clade whose phylogenetic patterns
were most similar to those of palms also resembled palms in being most species-rich
on cation-poor soils. The phylogenetic structuring of local plant communities varies
along a soil base cation concentration gradient within non-inundated Amazonian rain
forests. Lineages can show either similar or different phylogenetic community struc ture patterns and evolutionary trajectories, and we suggest this to be linked to their
environmental adaptations. Consequently, geological heterogeneity can be expected
to translate into a potentially highly diverse set of evolutionarily distinct community
assembly pathways in Amazonia and elsewhere
