How does habitat connectivity influence the colonization success of a hemimetabolous aquatic insect? - A modeling approach

Climate and land-use change constitute major threats to biodiversity. Beside pure habitat loss, changing environmental conditions are likely to result in decreasing landscape permeability and increasing landscape fragmentation. This compromises habitat connectivity and, thereby increases threats to meta-population persistence. Comprehensive theoretical knowledge and general understanding of key parameters affecting habitat connectivity are therefore mandatory to assess risks of environmental change. However, related studies are scarce for hemimetabolous freshwater insects, which depend on both aquatic and terrestrial sites to complete their life cycle. We developed a process-based, spatially explicit meta-population model for a hemimetabolous freshwater insect, parameterized based on the traits of a damselfly, and analyzed the influence of varying landscape permeability on patch colonization for differently structured coextensive habitat networks. The in total 675,000 networks were set up by varying (1) landscape scenarios, representing different levels of permeability, (2) stream networks and (3) derived habitat patch assemblages, using least-cost path analysis. We found that habitat connectivity in general strongly determined the proportion of colonized habitat patches (Spearman’s ρ = 0.64). Moreover, a multi-factorial ANOVA of the parameters used for habitat network set up showed that the number of habitat patches had the largest effects on the colonization success (18.6 % explained variance) followed by varying proportions of three landscape types incurring increasing dispersal costs (13.1 %) and the spatial arrangement of habitat patches (7.1 %). The introduced model generated theoretical knowledge how changing environmental conditions (e.g. landscape permeability) can influence the habitat connectivity of hemimetabolous freshwater species and, thus, has the potential to support conservation through habitat management within changing landscapes. Its design facilitates future adaptation to real hemimetabolous species and real-world habitats.