A conceptual framework for constructing and evaluating directed ecological networks: Evidence from Wuhan Metropolitan Area, China

Many ecologists have demonstrated that building ecological networks (ENs) can resist habitat fragmentation. However, existing studies have not yet explored the directionality of ENs. In this study, we proposed a research framework for the construction and structural evaluation of directed ENs from the perspective of dynamic biological flows. The framework reveals the operational essence of ENs, which is that dynamic biological flows rely on static carriers for directed movement. Thus, this framework overcomes the shortcomings of previous studies that only focused on static carriers and ignored dynamic biological flows. In other words, this study will guide the research of ENs from undirected to directed. The specific research and innovations are as follows. (1) First, the MaxEnt model and InVEST model were combined to evaluate habitat suitability in Wuhan Metropolitan Area (WHM), and 180 species habitats were identified accordingly. A total of 366 potential species migration corridors were extracted based on the identified species habitats and ecological resistance surfaces. (2) Second, we constructed a new relationship function between dynamic biological flows and potential biological flows, species dispersal probability, and species dispersal attraction. The results indicate that dynamic biological flows can serve as the measurement of directionality for directed ENs, and their density and intensity exhibit significant spatial heterogeneity. (3) Finally, we introduced the Chu-Liu/Edmonds' algorithm for complex network analysis to reveal the tree-like structure of directed ENs. The results show that the backbone and branches of directed ENs in WHM are species migration pathways with maximum dynamic biological flows linking global and local habitats, respectively. Meanwhile, the implementation of hierarchical protection according to the tree-like structure of directed ENs can significantly enhance its robustness.