A test of the preference–performance hypothesis with stream insects: selective oviposition affects the hatching success of caddisfly eggs

Abstract

Summary Under the preference–performance hypothesis (PPH), oviparous females select oviposition sites that optimise the fitness of their offspring (eggs or larvae). The resulting distribution and fitness of offspring may have knock‐on effects for population distribution patterns and dynamics during larval and adult stages. We tested the PPH for Australian caddisflies from two genera (family: Hydrobiosidae) that oviposit in different flow conditions. Apsilochorema spp. oviposit in slow flowing water, whereas Ulmerochorema sp. favour fast flows. We expected hatching success to be higher in velocities favoured by ovipositing females. In a field experiment, newly laid egg masses of each species were exposed to experimental ‘fast’ and ‘slow’ flow treatments throughout development and monitored until they hatched or died. In a second field experiment, we placed egg masses in a range of velocities (0.0–1.5 ms−1) to determine the threshold beyond which eggs were damaged by shear forces. The results supported the PPH for one species. Apsilochorema egg masses were sheared from the substratum in fast flows, but hatched with 100% success in favoured slow flows. The threshold velocity for Apsilochorema was 0.6–0.7 ms−1, well beyond the natural oviposition range of up to 0.3 ms−1. Ulmerochorema eggs hatched in all flows, suggesting that flow‐related mortality of the egg stage is unimportant for this species. Oviposition in fast flows might enhance the fitness of Ulmerochorema larvae or ovipositing females instead. Vulnerability to shear forces appears to explain why Apsilochorema lay eggs exclusively in slow flows. Shear may be a common cause of mortality for lotic insect eggs, and unseasonal spates or regulated flows may significantly affect recruitment of larvae. Selective oviposition affects the spatial distribution and survival of eggs and thus affects larval supply, and these supply dynamics are under‐studied in stream ecology.

Macroinvertebrate responses to flow and stream temperature variability across regulated and non‐regulated rivers

“…The ecological implications of the timing of hydrological extremes were observed within this study, which highlighted significant associations between several univariate ecological responses and abiotic indices, including fauna reproducing by laying isolated eggs on the riverbed being positively associated with minimum flows in July. This could be attributed to different reasons, including the resistance of such eggs to higher flows, or increased amounts of phytoplankton being flushed downstream, which may otherwise encrust eggs and prevent embryonic development (Bovill, Downes, & Lancaster, ); the latter is plausible given high productivity within the reservoirs studied that results in large quantities of organic matter being deposited within the tailwaters (House, Beatson, Martin, & Bowles, ; White, Wilding, House, Beatson, & Martin, ).…”

Ultrastructure of antennal and posterior abdominal sensilla in Chlorophorus caragana females

“…The choice of oviposition site directly affects the development of the next generation of insects (Bovill et al, 2013;Fatouros et al, 2012;Liu et al, 2012;Masaki, 1986;Van Loon, 1996;Woodcock et al, 2013;Zhang et al, 2012). Female insects locate hosts by means of complicated behaviors in which sensilla play important sensing roles.…”

Egg masses of some stream‐dwelling caddisflies (Trichoptera: Hydrobiosidae) from Victoria, Australia

“…Most importantly, the egg masses are morphologically distinct, can be identified readily and enumerated. These flow preferences are related, in part, to egg mass morphology and the ability of the spumaline to resist the forces of hydraulic shear stress (Bovill et al 2013). facilitate empirical estimates of recruitment for studies on population dynamics.…”

“…Traditionally, freshwater ecological research has focussed on the aquatic juvenile stages and predominantly late instar larvae, but estimating the factors that drive population dynamics requires examination of multiple life stages, including the often-neglected stages of eggs, pupae and adults. The success of such studies, however, depends on understanding the environmental factors that influence oviposition behaviours, and hence the spatial and temporal distribution of eggs within water bodies (Hoffmann & Resh 2003;Lancaster et al 2003;Reich & Downes 2003a, 2003bEncalada & Peckarsky 2007;Lancaster et al 2010b;Reich et al 2011;Storey et al 2016), and on understanding the factors that can influence successful hatching of eggs and recruitment of juveniles into the population (Siva-Jothy et al 1995;Purcell et al 2008;Bovill et al 2013;Bovill et al 2015;. Pupae are rarely considered by freshwater ecologists but high, density-dependent mortality of pupae can regulate some populations (Marchant & Hehir 1999).…”

“…There are over 15 genera and over 60 species of Australian Hydrobiosidae, occurring primarily in eastern Australia, with the highest species richness in south-eastern Australia and Tasmania (Dean 1997). Subsequent ecological research on these same genera has provided further insight into the consequences of oviposition behaviour for the spatial arrangement of egg masses (Lancaster et al 2003;Reich et al 2011), and into the effects of flow and egg predation on hatching success (Bovill et al 2013;Bovill et al 2015). an 'emergent rock'), climb down the side of the rock and lay their eggs in a single, plaque-shaped mass covered in spumaline and attached to the underside of the rock.…”