An experimental examination of dispersal decisions made by flight-capable heteropteran insects in urban stormwater pond conditions
Data files
Mar 04, 2026 version files 7.25 KB
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NotoCorixDisp_EmigrationAssay.csv
1.82 KB
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NotoCorixDisp_Pre-emigrationBehaviouralAssay.csv
1.58 KB
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README.md
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Abstract
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.
This Dryad repository contains the datasets for the two parts of the dispersal experiment:
- Emigration assay: N. undulata and H. obliqua were allowed to fly out of their experimental units to examine the dispersal probabilities over time (survival analysis), the overall dispersal probability by the end of the experiment, and dispersal latency as the time it took for individuals to take flight out of their experimental units. See the associated article methods for full details.
- Pre-dispersal motivation behavioural assay: where N. undulata and H. obliqua were prevented from completing the emigration event, allowing quantification of behaviours associated with pre-dispersal motivation. Behaviours are counts of dispersal attempts and pre-dispersal preparation behaviours within the 15-minute observation period.
Description of the data and file structure
NotoCorixDisp_EmigrationAssay.csv
These data are for the emigration assay - individuals were able to take flight out of experimental units and the following aspects of dispersal propensity were measured here: dispersal probability and dispersal latency (timing).
Each row is an individual in the experiment, in its own experimental cup with treatment water.
Columns: IDcode: individual ID - codes for randomized treatment x species assignment; Treatment: either control water or SWMP (stormwater pond) water; Species: Noto (Notonecta undulata) or Corix (Hesperocorixa obliqua); Sex: M or F (male or female)
The following columns are used for the survival analysis (and for examining final dispersal probability by the end of the experiment with the Dispersal Status response variable):
Time: This column is used in the survival analysis in conjunction with the DispStatus column. It represents the time an individual dispersed, or if not, the time of the experimental end for that species.
DispStatus: Dispersal status, 0 or 1; 1 = dispersed at Time t, 0 = did not disperse by experimental end for that species. Experiment run time depended on species. See details in methods.
The following column is the response variable Dispersal Latency (timing):
DispLatency: the dispersal latency or timing, which is the time it took for an individual to emigrate out of the experimental unit, recorded at time points (e.g. checked after 15 minutes, 30 min, 45 min time points, etc). When an individual has no dispersal time i.e. non-disperser, this is coded as zero to analyze these data with a two-part model for the disperser (positive dispersal latency), vs the non-disperser data with respect to the predictors simultaneously in the ZINB model.
NotoCorixDisp_Pre-emigrationBehaviouralAssay.csv
These data are for the pre-dispersal motivation behavioural assay. This assay allows for their pre-dispersal motivation behaviours to be quantified: number of dispersal attempts, and pre-dispersal preparation behaviour (see details below)
Each row is an individual in the experiment, in its own experimental cup with treatment water.
Columns: IDcode: individual ID - codes for randomized treatment x species assignment; Treatment: either control water or SWMP (stormwater pond) water; Species: Noto or Corix (Noto: Notonecta undulata; Corix: Hesperocorixa obliqua); Sex: M or F (male or female)
The following columns represent response variables for the pre-dispersal motivation behaviours examined:
DispAttempts: number of dispersal attempts observed
AtSurfaceorFlips: number of pre-dispersal preparation behaviours. For the corixid, this means breaching the surface of the water and readying itself at the surface. For the notonectid, this means flipping over at the surface of the water and readying itself at the surface.