Beyond network-based approaches: uncovering the true cost of connectivity.

CONTEXT: Fragmented landscapes challenge biodiversity conservation. While connectivity elements are promoted to mitigate the effects of fragmentation, their effectiveness remains debated. OBJECTIVES: This study evaluates the effectiveness of corridors and stepping stones in enhancing dispersal success and population dynamics in a high-resistance matrix. We compare two experimental approaches: a landscape-based design that explicitly accounts for matrix resistance, and a traditional network-based design in which habitat patches are connected by tubes. METHODS: We conducted a laboratory experiment using the microarthropod model Folsomia candida, manipulating fragmentation by varying the distance between four habitat patches embedded in a high-resistance matrix. Connectivity elements (corridors and stepping stones) were tested and compared with unconnected landscapes (control) and network-based designs. Over 12 weeks, we monitored colonization success, population size, reproduction rate, and adult survival using AI-based image analysis. RESULTS: The presence of corridors as a connectivity element enhanced the colonization of initially empty patches, but their effectiveness was distance-dependent. Stepping stones did not differ from the non-connected control landscapes. Interestingly, the largest total populations were found in the non-connected control landscapes, where restricted dispersal resulted in higher reproduction, indicating a trade-off between movement and reproduction. The highest mortality of released adults was observed in landscapes with corridors, whereas higher recruitment was observed in stepping stones landscapes. Network-based designs yielded a higher population size in initially empty patches compared to landscape-scale designs. However, as they bypassed matrix-related dispersal costs, they led to a miss-estimation of the movement, reproduction, survival and recruitment processes. CONCLUSIONS: Connectivity elements can support dispersal and reproduction, but may also increase mortality in resistant matrices. Conservation strategies should incorporate matrix resistance and landscape-scale context to better promote population dynamics in fragmented landscapes. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10980-026-02382-3.