Effects of landscape fragmentation on floodplain fishes as revealed by species–habitat networks

How species interact with habitat patches is influenced primarily by habitat configuration (e.g., connectivity) and species' functional traits. As levels of fragmentation increase, identifying the intricate connections between these components is crucial for biodiversity conservation. We used the species-habitat network (SHN) approach to identify the links between fish species and lakes in a highly fragmented floodplain; to determine lakes and fish species that are key to maintaining landscape SHN organization; and to examine the impact of habitat configuration and species functional traits on fish responses to loss of lateral hydrological connectivity (LHC). Low metacommunity functional connectivity, lack of robustness, and high modularity (i.e., strong within group interactions) and nestedness indicated low resistance of fish communities to long-lasting landscape fragmentation, highlighting the importance of large lakes connected by rivers and fishes that migrate between rivers and lakes to maintaining the SHN organization in floodplain ecosystems. The strong association between maximum body length and fish contribution to this network organization indicated that large fish species are potentially more likely to establish interactions at the landscape scale. Trophic level was the main factor controlling the roles of migrating fishes in SHN organization. Based on species' interactions with habitat patches, we identified and mapped the sites and species responsible for the main features of the SHN structure. Our approach offers new directions for conserving and restoring fragmented floodplains by integrating LHC and fish functional traits to inform targeted conservation priorities.