Neutral dynamics operate among the species of each guild in patchy
habitats
The variation partitioning based on canonical analysis (i.e. redundancy
analysis; Borcard, Legendre, & Gillet 2011; Peres-Neto & Legendre,
2010) and the autocorrelation method (Diniz-Filho et al., 2012) were
also used to infer the relative roles of alternative processes. In
general, the applications followed Yunoki & Torres (2016); Yunoki,
Torres, Pouilly, & Hablützel (2017); Yunoki, Torres, & Cholima (2018);
Yunoki, Torres, & Cholima (2019).
The variation partitioning was applied for the model communities at
convergence time. In model communities, the species response curves
might be often unimodal, so that the species abundances data was
Hellinger transformed prior to analysis and the first and second-order
orthogonal environmental variables were used (Borcard et al., 2011;
Gilbert & Bennett, 2010). The standard forward selection procedure was
used because the habitat associations among the species of each guild
were equivalent and these species might have similarities regarding
their environmental and spatial associations (Borcard et al., 2011;
Peres-Neto & Legendre, 2010). If more than two guilds were coexisted in
model communities and if the pure environmental component was
significant, the hierarchical guild structure was identified by thek -means partitioning of linear combination scores (scaling 1) and
simple structure index criterion. If the hierarchical guild structure
was significant, the principal coordinates of neighbour matrices (PCNM)
were constructed to model the spatial structures within and among patchy
habitats in the residual variation of species composition between sites.
The portion explained by each component was obtained by the adjusted
coefficient of determination in overall and hierarchical models, and its
significance was estimated by a randomization test applying an alpha of
0.05.
The functional uniqueness and redundancy of model communities were
compared to the relative portions explained by environmental and pure
spatial components in the total explaind variation of overall model;
then, the total explained variation and these relative portions were
compared between overall and hierarchical models. Furthermore, the
number of guilds coexisted in model communities was compared to the
number of habitat types identified by hierarchical guild structure.
In the model communities resulted with only one guild, the
autocorrelation method was applied for the species abundances predicted
by true spatial and false environmental components. In the model
communities resulted with more than two guilds, this method was applied
for the true environmental component of overall model, and the spatial
structures found by hierarchical model in each environmental context.
The correlograms were calculated using the number of distance classes
computed by Sturges method in overall model; while, three or two
distance classes in each environmental context. In all cases, the Mantel
correlation between matrices of correlation coefficients and correlogram
distances among species was tested against the null hypothesis of less
than zero applying an alpha of 0.05. Appendix A presents the summary
statics of scenarios.