Environmental DNA data of aquatic insects for habitat suitability models

The rapid loss of biodiversity in freshwater systems asks for a robust and
spatially explicit understanding of species’ occurrences. As two
complementing approaches, habitat suitability models provide information
about species’ potential occurrence, while environmental DNA (eDNA) based
assessments provide indication of species’ actual occurrence.
Individually, both approaches are used in ecological studies to
characterize biodiversity, yet they are rarely combined. Here, we
integrated high-resolution habitat suitability models with eDNA-based
assessments of aquatic invertebrates in riverine networks to understand
their individual and combined capacity to inform on species’ occurrence.
We used eDNA sampling data from 172 river sites and combined the detection
of taxa from three insect orders (Ephemeroptera, Plecoptera, Trichoptera;
hereafter EPT) with suitable habitat predictions at a subcatchment level
(2 km2). Overall, we find congruence of habitat suitability and eDNA-based
detections. Yet, the models predicted suitable habitats beyond the
observed number of detections by eDNA sampling, congruent with the
suitable niche being larger than the realized niche. For local mismatches,
where eDNA detected a species but the habitat was not predicted suitable,
we calculated the minimal distance to upstream suitable habitat patches,
indicating possible sources of eDNA signals from upstream sites
subsequently being transported along the water flow. We estimated a median
distance of 1.06 km (range 0.2–42) of DNA transport based on upstream
habitat suitability, and this distance was significantly smaller than
expected by null model predictions. This estimated transport distance is
in the range of previously reported values and allows extrapolations of
transport distances across many taxa and riverine systems. Together, the
combination of eDNA and habitat suitability models allows larger scale and
spatially integrative inferences about biodiversity, ultimately needed for
the management and protection of biodiversity.