Large‐scale manipulation of oviposition substrata affects egg supply to populations of some stream‐dwelling caddisflies

Macqueen, Ashley; Downes, Barbara J.

doi:10.1111/fwb.12535

Cited by 15 publications

(14 citation statements)

References 32 publications

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“…Much of this research focuses particularly on plant attributes (such as chemicals that can be detected by female insects) that influence successful oviposition or larval survival [83]. In contrast, although some aquatic insects lay their eggs on or within plants (particularly macrophytes), many do not attach eggs directly to any particular object or attach their eggs to inanimate objects such as rocks, wood or bark [84,85,86,87,88,89]. Notably, these species are often very selective about the characteristics or microenvironment of these objects, which distinguishes them from many terrestrial insects that oviposit on hard surfaces but are rather unselective (e.g., some praying mantis).…”

Section: Real and Presumed Differences In Aquatic And Terrestrial mentioning

confidence: 99%

Aquatic versus Terrestrial Insects: Real or Presumed Differences in Population Dynamics?

Lancaster

Downes

2018

Insects

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The study of insect populations is dominated by research on terrestrial insects. Are aquatic insect populations different or are they just presumed to be different? We explore the evidence across several topics. (1) Populations of terrestrial herbivorous insects are constrained most often by enemies, whereas aquatic herbivorous insects are constrained more by food supplies, a real difference related to the different plants that dominate in each ecosystem. (2) Population outbreaks are presumed not to occur in aquatic insects. We report three examples of cyclical patterns; there may be more. (3) Aquatic insects, like terrestrial insects, show strong oviposition site selection even though they oviposit on surfaces that are not necessarily food for their larvae. A novel outcome is that density of oviposition habitat can determine larval densities. (4) Aquatic habitats are often largely 1-dimensional shapes and this is presumed to influence dispersal. In rivers, drift by insects is presumed to create downstream dispersal that has to be countered by upstream flight by adults. This idea has persisted for decades but supporting evidence is scarce. Few researchers are currently working on the dynamics of aquatic insect populations; there is scope for many more studies and potentially enlightening contrasts with terrestrial insects.

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Section: Real and Presumed Differences In Aquatic And Terrestrial mentioning

confidence: 99%

Aquatic versus Terrestrial Insects: Real or Presumed Differences in Population Dynamics?

Lancaster

Downes

2018

Insects

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“…For species with specialised oviposition habits, temporal fluctuations in the availability of oviposition habitat can influence recruitment and longer‐term variability in populations (Peckarsky et al., 2000). Spatially, variations in oviposition site abundance can constrain egg supply and densities of subsequent life stages for many aquatic insects, including multiple species of Ephemeroptera and Trichoptera (Encalada & Peckarsky, 2012; Lancaster & Downes, 2014,2018; Lancaster et al., 2010; Macqueen & Downes, 2015), and some Hemiptera and Odonata (Goldstein et al., 2012; Mellal et al., 2018). If temporal variations in oviposition site abundance also influence populations, then we might expect concurrence between seasonal egg‐laying patterns and oviposition site availability.…”

Section: Introductionmentioning

confidence: 99%

Hydrological controls on oviposition habitat are associated with egg‐laying phenology of some caddisflies

et al. 2021

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Seasonal variation in resource availability can have strong effects on life histories and population densities. Emergent rocks (ERs) are an essential oviposition resource for multiple species of stream insects. The availability of ERs depends upon water depth and clast size, which vary with discharge and river geomorphology, respectively. Recruitment success for populations may depend on whether peak egg‐laying periods occur at times when ERs are also abundant. For multiple species that oviposit on ERs, we tested whether seasonal fluctuations in ER abundance were concurrent with oviposition phenology. We also tested whether high discharge drowned ERs for sufficiently long periods to preclude egg laying, and whether this problem varied between rivers differing in channel morphology and particle size distribution. We obtained a continuous timeseries of water level (WL) measured every 30 min for 2 years at sites on three rivers in south‐eastern Australia with similar hydrology but different geomorphology. A relationship between WL and ER numbers was determined empirically at each site and these relationships were used to predict ER availability over the 2 years. Egg masses of 10 species of caddisflies were enumerated each month for a year in one river to establish oviposition phenology. Abundance of ERs was inversely related to discharge in all three rivers. ERs were most abundant during autumn and scarce during spring. Site‐specific geomorphology resulted in skewed or multimodal distributions of ER abundance each year. Between years, catchment‐scale hydrometeorology mediated patterns of ER availability, despite the close proximity of sites. Temporal variance in ER availability was not consistently correlated with mean WL or WL variance. ER variance increased with WL variance, when WL was below a threshold equivalent to mean annual WL. Above this threshold, most ERs were likely to be submerged. Oviposition phenology varied strongly among the 10 species of caddisflies, with egg‐laying ranging from 1–2 months to year‐round. Temporal variations in ER and egg mass abundance were not correlated for most species. Below a threshold minimum number of ERs, egg masses were highly crowded onto the few available ERs, which is evidence that ERs were in short supply. For five species, high egg mass abundance was positively associated with periods of the year when the time above the threshold number of ERs was high. Unusually, two species laid most egg masses during winter and when the time above this threshold was short. Three species showed no association between egg mass abundance and time above this threshold; two of these species laid eggs year‐round. Regional hydrometeorology controlled the availability of ERs, but between‐river differences were sufficient to deliver different outcomes in the availability of oviposition sites between years and seasons. Caddisflies were rarely prevented from laying eggs but periods when ERs were in short supply created crowding, which may be associated with negative fitness effects...

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“…The net-spinning larvae of Ecnomus are omnivorous but prey primarily upon invertebrates that become entangled in the silken threads of the net (Chessman 1986;Lancaster et al 2009). In the study stream, larvae occur throughout the year, the adult flight period is approximately 6 months (Nov-April) and oviposition occurs throughout (see also Macqueen and Downes 2015). These observations suggest that these species may be bi-or multivoltine, have weakly synchronized cohorts with long emergence periods, overlapping generations, and perhaps relatively long-lived adults (e.g.…”

Section: Study Species Site and Sampling Protocolsmentioning

confidence: 77%

Dispersal traits may reflect dispersal distances, but dispersers may not connect populations demographically

Lancaster

Downes

2017

Oecologia

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Ecological traits that reflect movement potential are often used as proxies for measured dispersal distances. Whether such traits reflect actual dispersal is often untested. Such tests are important because maximum dispersal distances may not be achieved and many dispersal events may be unsuccessful (without reproduction). For insects, many habitat patches harbour 'resident' species that are present as larvae (sedentary) and adults (winged and dispersing), and 'itinerant' species present only as adults that have dispersed from elsewhere and fail to reproduce. We tested whether itinerancy patterns were temporally consistent, and whether itinerant and resident species differed in wing morphology, a strong correlate of flight capability. Over 3 years and at multiple locations in a 22 km stream length, we sampled larvae and adults of caddisflies in the genus Ecnomus to categorize species as residents or itinerants. Flight capacity was measured using wing size (length and area) and shape parameters (aspect ratio and the second moment of wing area). Three species of Ecnomus were residents and three species were itinerants, and patterns were consistent over 3 years. On average, itinerant species had larger wings, suggesting a greater capacity to fly long distances. Wing shape differed between species, but did not differ systematically between residents and itinerants. Wing morphology was associated with actual but not effective dispersal of some species of Ecnomus. Morphological traits may have weak explanatory power for hypotheses regarding the demographic connectedness of populations, unless accompanied by data demonstrating which dispersers contribute new individuals to populations.

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Large‐scale manipulation of oviposition substrata affects egg supply to populations of some stream‐dwelling caddisflies

Cited by 15 publications

References 32 publications

Aquatic versus Terrestrial Insects: Real or Presumed Differences in Population Dynamics?

Aquatic versus Terrestrial Insects: Real or Presumed Differences in Population Dynamics?

Hydrological controls on oviposition habitat are associated with egg‐laying phenology of some caddisflies

Dispersal traits may reflect dispersal distances, but dispersers may not connect populations demographically

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