Guild-Based Metacommunity Internal Structure: Insights From Waterbird Assemblages in a Dynamic Estuarine System

Abstract

Aim

Understanding how ecological processes shape species assemblages in dynamic environments is central to community ecology. Estuarine waterbirds are a compelling system for metacommunity analysis because their high mobility, functional diversity and sensitivity to environmental variation make them well suited to examine how assembly is partitioned in a highly mobile group. We characterize the internal structure of a waterbird metacommunity, expecting a comparatively weak spatial component relative to environmental filtering and species co-distribution given the group's mobility, and use a trait-based, guild-level reading to interpret these patterns across landscape contexts.

Location

Paranaguá Estuarine Complex, southern Brazil, as a model system for a dynamic subtropical estuarine system.

Taxon

Estuarine waterbirds.

Methods

Using joint species distribution models (JSDMs), we partitioned variation in observed species occurrence among environmental predictors, spatial structure and co-distribution. Our analysis included 32 waterbird species grouped into functional foraging guilds. Models included environmental field data, land-cover variables and Moran's eigenvector spatial predictors derived from 36 transects surveyed monthly between March 2020 and February 2021.

Results

Environmental filtering and species co-distribution explained most of the variation in community composition, whereas spatial effects were comparatively weak. Environmental variables, particularly salinity and air temperature, showed contrasting effects across foraging guilds. Migratory and resident ground predators exhibited different seasonal tendencies, compatible with temporal niche partitioning. In contrast to our expectations, aerial predators showed positive intraguild residual co-distributions, consistent with heterospecific attraction or shared responses to unmeasured factors. Assemblages in bays with higher inferred anthropogenic pressure showed a greater contribution from species co-distribution, consistent with (though not direct evidence of) weaker species–environment relationships.

Main Conclusions

Our results emphasize the importance of environmental gradients and residual species co-distribution in shaping waterbird metacommunity structure in a dynamic estuarine system. By integrating species-level and guild-level responses across landscape contexts, this study illustrates how the internal structure framework can help disentangle multiple assembly processes in highly mobile taxa.