Persist or perish: critical life stages determine the sensitivity of invertebrates to disturbances

Abstract

A large proportion of studies assessing the impact of disturbances on the invertebrate community composition focus on a single life stage, assuming that those are an adequate indicator of environmental conditions. The effect of a specific disturbance may, however, depend on the life stage of the exposed organism. Therefore, we focused on the effect of spates on the caddisfly Agapetus fuscipes CURTIS (Trichoptera: Glossosomatidae) during different larval stages. A 2 year field study was performed in which we measured the discharge dynamics and population development of A. fuscipes in four lowland streams in The Netherlands. A stage-structured population model (i.e. StagePop) was used to test the impact of peak discharge on the different life stages, as larval instars 1-4 were not effectively sampled in the field. Four different mortality rates in response to spates were simulated, including a constant low, a constant high, a decreasing and an increasing impact per larval stage. This way, we were able to show a potential association between spates and population declines, where the stage-population model including decreasing impact by spates with increasing larval life stage most accurately described the population development of the larval instars 5-8. Focusing only on late instars could thus potentially result in underestimation of the effects of spates on this species. In conclusion, determination of responses of critical life stages to specific disturbances may help to identify the causes of the presence and absence of species, and thereby aid more effective management and restoration of degraded aquatic systems.

Vertical reworking of sediment by the cased caddisfly Glossosomatidae (Agapetus fuscipes) increases sand exposure and availability in armoured gravel-bed rivers

“…9b). Furthermore, the displacement of this sediment is likely to be lessened at earlier instars as they were observed in the River Dove to occupy lower vertical elevations on surface particles and are also less resistant to flow than larger taxa (van Der Lee et al, 2020). During pupation A. fuscipes fix their pupal cases on cobbles in flowing water, often on the upstream face (Anderson and Bourne, 1974).…”

Van de regen in de drup : Verkenning van de huidige kennis en praktijk rond integraal herstel van beekdallandschappen

“…De sturende milieufactoren werken elk in een andere mate in op het organisme, waarbij nog niet altijd duidelijk is hoe de interactie tussen deze factoren werkt. Wel is duidelijk dat van de milieufactoren naast de waarde ook moet worden gekeken naar de variatie of constantheid en de timing van pieken in relatie tot de levensfase van organismen, om een goed beeld te krijgen van de impact (Van der Lee et al, 2020).…”