An experimental examination of dispersal decisions made by flight-capable heteropteran insects in urban stormwater pond conditions

1.     Urbanization transforms
landscapes, creating altered environments with novel aquatic habitats.
Constructed stormwater ponds are designed to manage increased stormwater
runoff from impervious surfaces and retain contaminants before flowing to
urban downstream waterways. These ponds are increasingly common in
urbanizing areas and despite elevated road runoff contaminants like road
salt, they can support aquatic insect communities. However, how increased
salinity in urban stormwater ponds impacts aquatic insect behaviour,
particularly dispersal which shapes connectivity in these patchy
landscapes, is unknown. 2.     Using a
simple, tractable outdoor dispersal assay, we explored whether urban
stormwater pond water impacts the dispersal propensity of two
flight-capable aquatic insects. We tested whether a predatory notonectid
(backswimmer) species, Notonecta undulata, and an herbivorous corixid
(water boatman) species, Hesperocorixa obliqua, differed in their
emigration responses when exposed to urban stormwater pond water or
unpolluted water. 3.     Overall
emigration probabilities did not change in response to stormwater pond
water. However, we found species-specific responses to treatment for
individual dispersal latency, with H. obliqua dispersing earlier in the
stormwater pond treatment than in the control while N. undulata showed no
difference. H. obliqua were also more dispersive than N. undulata overall,
with higher dispersal probabilities and shorter dispersal latencies.
Sex-biased dispersal was observed in the corixid species but not in the
notonectids. We also did not find any treatment differences in
pre-dispersal motivation behaviours. These findings suggest that urban
stormwater pond conditions can influence dispersal timing in
species-specific ways in aquatic insects, even if overall pre-dispersal
behaviour and probabilities remain unchanged.  
4.     Dispersal plays an important
role in shaping communities in spatially heterogenous environments,
including human-modified landscapes. As Heteroptera taxa are some of the
earliest dispersers in newly created aquatic environments, understanding
how urban pond conditions affect dispersal behaviour and impact species
with different dispersal abilities can help inform the management of urban
blue spaces to support freshwater biodiversity.