Tropical Forest Community Ecology

84 Campbell O. Webbetal.

Stochastic and/or

Historical

community

Regional pool

Continental

Biogeographic

filter

Branch length units

Community

phylogeny

Neighborhood

Not in habitat H

In habitat H

community pool

Local/

1a

1b

substrate filter

Continental pool

2

Time

3

Global

lineage

evolution

Autecology h

and climatic filter

Regional biogeo.

Figure 6.1 Illustrative example of the samplin gof linea ges throu gh different scales, dependin gon ecolo gical
characters and biogeography. Negative (or positive) interactions may occur among individual neighbors (1a). Habitat
filterin gfor traits that permit survival in abiotic habitat H may occur amon gtaxa in a community pool, modified by
competitive interactions (1b). The community pool is in turn an environment- and dispersal-dependent samplin gof a
regional pool (2), which is structured by the geographic history of lineage diversification (3). The particular physical
size of each sample/pool pair, and the number of levels of nestedness, depend on biological and physical
circumstances (see text). Note the intentional similarity to the “life-cycle filtering” model in Harper (1977).

Phylogenies.The great expansion in numbers
of plant species sequenced and included in phy-
logenetic analyses offers an increasingly resolved
picture of the relationships amon gan giosperms
(Stevens 2001, Angiosperm Phylogeny Group
2003); for example, as of mid-2005, some 6500
taxa in GenBank had been sequenced forrbcL (A.
Driskell personal communication). Although rel-
atively few tropical forest tree species are included
in these analyses, enough exist to draw a rea-
sonable picture of relationships at the “generic”
level, and it has become increasingly possible for

ecologists themselves to undertake the molecular

work required to produce a phylogeny. There are

even online tools that permit the rapid retrieval

of a coarse phylogenetic hypothesis for any list of

angiosperm species (Webb and Donoghue 2005).

A number of serious caveats are necessary

concernin gphylo genies for tropical trees. First,

these phylogenies are hypotheses, and some areas

of the angiosperm tree may still undergo seri-

ous re-organization, especially with the increasing

evidence that “deep” hybridization events may

have been frequent (Davis and Wurdack 2004,