A novel framework of phylogenetic and trait-based
community structure
Well
known, community assembly processes act on species through a series of
phenotypes (or frequently called functional traits) (Chai et al.2019; Laughlin & Messier 2015; Pawar 2015). According to distinct
contributions of functional attributes in community assembly, we raised
the concepts of “predominant trait” and “assistant trait” to refer
major or supporting traits mediating assembly process. Combining prior
theoretical efforts (Kraft & Ackerly 2010; Kraft et al. 2007;
Cavender-Bares et al. 2004; Webb et al. 2002) and the
thought of distinct contributions displayed by traits, we proposed a
novel framework of phylogenetic and trait-based structure.
We built this modified framework on four key assumptions. Firstly,
following with prior conceptual work, we assumed that phylogenetic
relatedness was a comprehensive proxy of interspecific similarity at
multiple ecological niches (Swenson 2013). Secondly, we assumed that
functional traits were independent with each other in evolutionary and
ecological processes. Because the relationship among phenotypes was
extremely complicated and taxon-specified, which was beyond the research
scope in this work. Thirdly, we assumed that environmental filtering
effect, competitive exclusion and stochastic process are three major
processes driving community assembly. Other processes such as mutualism,
host-pathogen interactions, plant-insect interactions and negative
density-dependence mentioned in (Cavender-Bares et al. 2009) were
not involved in this study, but deserved to be considered in future
studies. Lastly, we assumed that phylogenetic signal metrics such as
Pagel’s lambda (Pagel 1999) and Blomberg’s K (Blomberg et al.2003) could accurately infer the phylogenetic conservatism in functional
traits. These assumptions above have also clarified the baselines to
apply this framework in interpreting the biodiversity pattern.
We
simulated ecological processes and community structure using virtual
species (A~H), phylogeny and traits (phylogenetic
conserved traits: T1 and T3; phylogenetic convergent traits: T2 and T4)
(Box 1). Two major parameters concerning trait conservatism
(phylogenetically conserved or convergent) and trait contribution
(predominant or assistant role) were involved in later prediction on
phylogenetic and functional dispersion. Given the effects of
environmental filtering and competitive exclusion produce opposite
imprints on community structure, as a representative, we only simulated
the assembly process driven by environmental filtering effect. Following
with Kraft and Ackerly (2010), environmental filtering processes were
discussed within simple (Fig. 1, scenario A and B) and complex (Fig. 2
scenario C, D and E) habitats, respectively. Besides, we simplified
complex habitat with only two microhabitats, which contained independent
predominant and assistant traits.
According to the phylogenetic and functional patterns demonstrated in
Fig 1 and 2, the modified framework of phylogenetic and trait-based
community structure was summarized in Table 1. Generally, in sample
habitat, phylogenetic community dispersion was accordant with the
functional dispersion of phylogenetically conserved predominant traits,
and opposed to phylogenetically convergent predominant traits. While,
dispersion comparison between phylogenetic relatedness and assistant
traits
in simple habitat became more complicated, which highly depended on the
degree of phylogenetic conservatism and inter-trait relationship. In
complex habitat, due to multi-directional effect across different
microhabitats, phylogenetic and functional dispersion appear complicated
and unpredictable.