The novel framework of phylogenetic and trait-based
community structure: distinct trait roles
Since Webb et al. (2002) raised the framework of phylogenetic
community structure, mechanistic understanding on community assembly has
experienced remarkable progress in the last decade. However,
phylogenetic approaches highly rely on phylogenetic relatedness being a
comprehensive proxy of ecological similarity (Swenson 2013; Losos 2008),
which implies the necessity of phylogenetic-trait intergration in
revealing mechanism underlying community assembly.
Distinct functional role and contribution of traits in assembling
species has been mentioned in earlier empirical and theoretical studies
(Kraft & Ackerly 2010; Swenson & Enquist 2009; Grime 2006; Thompsonet al. 1996). Swenson & Enquist (2009) and Grime (2006) have
detected that plant traits related to productivity often appeared
clustered in local communities, while disturbance and regeneration
related traits displayed locally over-dispersed. Kraft & Ackerly (2010)
have ever predicted that functional traits related to resource use and
environmental tolerance were more likely to answer habitat filtering,
resource use strategy traits were more sensitive to interspecific
competitive exclusion and niche differentiation, physical and chemical
defense traits displayed a major role in responding to enemy-mediated
negative density dependence. These information together have presented
an apparent signal that part of traits are more important (predominant
traits) in responding to a certain ecological process, and the others
performed relatively less sensitive (assistant traits) response to
assemblying process. Absolutely, either predominant or assistant traits
are indispensable niche components at both species and community levels.
Actually, it appears extraordinarily challenge to decide which
functional attributes display a more important role than the others, as
they work as an alliance in most of cases (Zukswert & Prescott 2017;
Grassein et al. 2014).
Based on prior understanding on community structure, we rethink over
community assembly process by taking account of distinct functional role
(predominant and assistant role) of phenotype. Through simulating
assembly process in simple habitat, we found that phylogenetic
dispersion was accordant with the functional dispersion of conserved
predominant trait, and opposed to the structure of convergent
predominant trait. This result of predominant traits could also occur in
assistant trait, especially when assistant trait presented similar
ecological and evolutionary chacteristics (Table 1). But in most
instances, the dispersion of assistant traits appeared unpredictable in
simple habitat. By comparison, phylogenetic and trait dispersion in
complex habitat appear extremely complicated, as community structure is
resulting from similar or/and distinct assembly processes acting on
conserved or/and convergent functional attributes. Therefore, it seems
impossible to predict the functional role of a certain trait in
structuring community within a complex habitat. These patterns have also
provided two reasonable explanations for the incongruent dispersion
between conserved trait and phylgoenetic relatedness (Du et al.2017; Yang et al. 2014; Swenson & Enquist 2009): the trait might
act an assistant role organizing community in simple habitat; or the
community is defined upon a heterogeneous habitat.