Ecological Indicators (Mar 2024)
Area- and latitude- shaped shorebird diversity patterns reveal constraints of migratory bottlenecks along the Yellow sea coast of China
Abstract
Migratory stopping regions are regarded as geographic bottlenecks. However, knowledge about constraints on migratory communities remains limited. This study proposed hypothetical spatial constraints (SCs) and tested the predictions by examining the response of multifaceted shorebird diversity to the tidal flat area and latitude of the stopping sites along the Yellow Sea coast. We estimated species richness (SR), phylogenetic and functional diversity (PD and FD) by building a species-level phylogenetic tree and measuring five functional traits of all species, using data on the shorebird community at 11 internationally important stopping sites of 2020–2021. We used multiple linear regression models and null models to examine the relationships between diversity metrics and stopping site variables (area and latitude). Functional and phylogenetic rarity of non-least concern species was calculated to estimate their risk of disappearance. The three dimensions of biodiversity decreased with decreasing area despite different slopes (i.e., FD was less sensitive to area than SR, whereas PD was lost more rapidly in smaller areas). In addition, only FD increased at sites approaching the terminal stopping area, implying that SR and PD were restricted from growing by latitude. Inferred from the PD and FD patterns, competitive exclusion tends be the dominant mechanism structuring the community, and the FD-inferred process was intensified in smaller sites toward the northerly terminal site. The area- and latitude-shaped diversity patterns indicate SCs on the migratory community, while a more intensive process of competitive exclusion tends to take place in smaller and near-terminal stopping sites. Consequently, the threatened shorebirds with less competitive capacity may be more prone than others in the SCs. This study highlighting the significance of the multifaceted biodiversity in monitoring the impacts of SCs and facilitating the development of conservation strategies in internationally critical migration bottlenecks.
