Contribution of small isolated habitats in creating refuges from biological invasions along a geomorphological gradient of floodplain waterbodies

1. Habitat fragmentation, which involves habitat size reduction and isolation, is a major cause of biodiversity decline. However, interest in small isolated habitats has increased among ecosystem managers because these fragments can serve as remnant refuges for unique and/or endangered species in human-altered landscapes.

2. In a fragmented floodplain of northern Japan, we demonstrate how habitat fragmentation and habitat quality shape the refuges for a unique endangered minnow (Rhynchocypris percnurus sachalinensis) from biological invasions. We focused on two invasive minnows, topmouth gudgeon (Pseudorasbora parva) and rosy bitterling (Rhodeus ocellatus ocellatus), which are the dominant invasive species. By using a graph theoretical approach and structural equation modeling, we elucidated the relationships among habitat fragmentation, habitat quality and the abundance of invasive minnows with the endangered swamp minnow.

3. We found that the invasion of topmouth gudgeon, which ...