Spatial phylogenetic and phenotypic patterns reveal ontogenetic shifts in ecological processes of plant community assembly

The analysis of spatial phylogenetic and phenotypic structure of plant
communities provides insight into the underlying processes and
interactions governing their assembly, and how these may change during
plant ontogeny. We used point pattern analysis to find out if saplings and
adult plants are surrounded by phylogenetically and phenotypically more
similar or dissimilar neighbours than expected by chance, and whether
these associations change from the sapling to the adult stage. To this
end, we combined information on the phylogenetic structure and eight
phenotypic traits of 15 woody plant species in two Mediterranean mixed
forests of southeastern Spain. At the community level, we found that the
sapling bank at both sites did not show phylogenetic or phenotypic spatial
patterns, but adults showed phylogenetic clustering (i.e., heterospecific
neighbours were more similar than expected). At the species level, we
found frequently repulsive patterns in the sapling bank of less abundant
species (i.e., heterospecific sapling or adult neighbours were more
dissimilar than expected) in both, phylogenetic and phenotypic analyses.
For the adult stage, we found phylogenetic attraction (i.e., more similar
neighbours) in just one species and phenotypic clustering in four species.
The processes driving the assembly of the communities of saplings and
adults leave detectable signals in the spatial phylogenetic and phenotypic
structure of our two forest communities. Our findings reinforce the
existence of ontogenetic shifts in the mechanisms involved in plant
community assembly. Facilitation between phylogenetically distant and
phenotypically divergent species favours the recruitment of less abundant
species. However, processes acting later in the ontogeny ameliorate the
competition between close relatives and determine the spatial structure of
adult plants. Nevertheless, the role of phenotype in shaping adult-adult
interactions was context- and trait-dependent. The use of spatial point
pattern analysis allowed a nuanced interpretation of the phylogenetic and
phenotypic structures of the plant community.