Chapter 6

ECOLOGICALORGANIZATION,

BIOGEOGRAPHY,ANDTHE

PHYLOGENETICSTRUCTUREOF

TROPICALFORESTTREE

COMMUNITIES

Campbell O. Webb, Charles H. Cannon, and Stuart J. Davies

OVERVIEW

The assembly of local tropical forest tree communities is influenced by abiotic filters from a larger regional species pool
(e.g., habitat differentiation, mass effects, dispersal limitation) and local biotic interactions (e.g., density dependence,
resource competition; summarized in Figure 6.1).These assembly processes are mediated by the phenotypic similarities
or differences of individuals, which are the outcome of evolutionary change in historical communities, and ultimately
the composition of taxa in a regional species pool is the outcome of biogeographic processes. Given the great diversity
of tropical tree species, we are unlikely ever to know enough about the ecologically important phenotypes or precise
spatial ranges of species to be able to predict local community species composition based on detailed attributes of every
species. However, we suggest in this chapter that because species similarity and difference are strongly influenced by
common ancestry, as is the presence or absence of a taxonomic clade in a geographic area, a phylogenetic approach
may be most effective for understandin gand predictin glocal community composition.
In this chapter, we briefly review current understandin gof abiotic and biotic controls of local species composition,
and of evolutionary patterns in ecological characters. We then describe phylogenetic analyses that explore the out-
comes of neighborhood interactions, habitat filtering, climatic gradients, and biogeographic history by analyzing the
phylogenetic patterns of species composition at nested spatial scales (Figure 6.1). We test these methods with data
from forests in Southeast Asia. Finally, we discuss the association of ecological and biogeographic characteristics with
internal nodes of plant phylogenies and the creation of predictive models for the general taxonomic and ecological
composition of communities.

ECOLOGICAL ORGANIZATION OF

TROPICAL TREE COMMUNITIES

What is the relative importance of abiotic limi-

tation, biotic interactions, and chance events on

contemporary species abundance and distribution

of tropical trees? The non-random distribution of

taxa on abiotic gradients (i.e., differing realized

niches; Hutchinson 1957) has been demonstrated

repeatedly, for topography (Ashton 1964, Clark

et al. 1999, Webb and Peart 2000, Valencia

et al. 2004), soil nutrients (Pottset al. 2002,

Hallet al. 2004, Palmiottoet al. 2004, Russo

et al. 2005, Paoliet al. 2006), geology (Cannon