# A Landscape Genetics Approach Reveals Species‐Specific Connectivity Patterns for Stream Insects in Fragmented Habitats

## TL;DR

This study explores how landscape features affect the genetic connectivity of stream insects in fragmented habitats, revealing species-specific dispersal patterns.

## Contribution

The study introduces a landscape genetics approach to identify species-specific connectivity patterns in stream insects within fragmented landscapes.

## Key findings

- Significant spatial genetic structure was observed at larger geographical distances among stream insect populations.
- Landscape factors influenced genetic connectivity differently across species, with Z. confusus showing high dispersal potential.
- Forested riparian zones enhanced connectivity for C. humeralis and H. fimbriata despite limited overland dispersal.

## Abstract

Dispersal is a critical process in ecology and evolution, shaping global biodiversity patterns. In stream habitats, which often exist within diverse and fragmented landscapes, dispersal ensures population connectivity and survival. For aquatic insects in particular, landscape features may significantly influence the degree of genetic connectivity among populations. Thus, understanding connectivity drivers in such populations is essential for the conservation and management of streams. We conducted a landscape genetic study using mitochondrial DNA (mtDNA) and genome‐wide single nucleotide polymorphism (SNP) markers to assess the functional connectivity of stream insects in a fragmented pasture‐dominated landscape. We focused on three species with terrestrial winged adults: the mayfly Coloburiscus humeralis, the stonefly Zelandobius confusus, and the caddisfly Hydropsyche fimbriata. We observed significant spatial genetic structure at larger geographical distances (populations separated by ~30 and 170 km). However, the effects of landscape factors, which were assessed at fine spatial scales, varied among species: for
C. humeralis
SNP data, genetic differentiation was weakly correlated with land cover, suggesting greater population connectivity within stream channels protected by forested riparian zones compared to fragmented streams; for
Z. confusus
, widespread gene flow indicated high dispersal potential across forested and pasture land; while overland dispersal was reduced for
H. fimbriata
(potentially due to local habitat features), this did not seem to hinder broader population connectivity. Our results emphasise the importance of assessing landscape features when evaluating population connectivity in stream riparian zones, which can greatly benefit stream management efforts through an enhanced understanding of connectivity dynamics.

We conducted a landscape genetics study using mtDNA and SNP markers to examine the connectivity and dispersal of three stream insect species, Coloburiscus humeralis, Zelandobius confusus and Hydropsyche fimbriata, in a fragmented, pasture‐dominated landscape on the North Island of New Zealand. Spatial genetic structure with isolation by distance was observed at large scales, while landscape factors such as land cover and topography had a weaker influence on genetic differentiation at finer scales.
Z. confusus
showed high dispersal capacity and low constraints in altered and proximate streams, whereas the short‐distance dispersal of
C. humeralis
and
H. fimbriata
was enhanced in forested stream channels.