Simulated climate change increases larval mortality, alters phenology, and affects flight morphology of a dragonfly

Abstract

. 2018. Simulated climate change increases larval mortality, alters phenology, and affects flight morphology of a dragonfly. Ecosphere 9(3):e02151. 10. 1002/ecs2.2151 Abstract. For organisms with complex life cycles, climate change can have both direct effects and indirect effects that are mediated through plastic responses to temperature and that carry over beyond the developmental environment. We examined multiple responses to environmental warming in a dragonfly, a species whose life history bridges aquatic and terrestrial environments. We tested larval survival under warming and whether warmer conditions can create carry-over effects between life history stages. Rearing dragonfly larvae in an experimental warming array to simulate increases in temperature, we contrasted the effects of the current thermal environment with temperatures +2.5°and +5°C above ambient, temperatures predicted for 50 and 100 yr in the future for the study region. Aquatic mesocosms were stocked with dragonfly larvae (Erythemis collocata), and we followed survival of larvae to adult emergence. We also measured the effects of warming on the timing of the life history transition to the adult stage, body size of adults, and the relative size of their wings, an aspect of morphology key to flight performance. There was a trend toward reduced larval survival with increasing temperature. Warming strongly affected the phenology of adult emergence, advancing emergence by up to a month compared with ambient conditions. Additionally, our warmest conditions increased variation in the timing of adult emergence compared with cooler conditions. The increased variation with warming arose from an extended emergence season with fewer individuals emerging at any one time. Altered emergence patterns such as we observed are likely to place individuals emerging outside the typical season at greater risk from early and late season storms and will reduce effective population sizes during the breeding season. Contrary to expectations for ectotherms, body size was unaffected by warming. However, morphology was affected: at +5°C, dragonflies emerging from mesocosms had relatively smaller wings. This provides some of the first evidence that the effects of climate change on animals during their growth can have carry-over effects in morphology that will affect performance of later life history stages. In dragonflies, relatively smaller wings are associated with reduced flight performance, creating a link between larval thermal conditions and adult dispersal capacity.

Ecology of female mating failure/lifelong virginity: a review of causal mechanisms in insects and arachnids

“…Low mating success of tethered females relative to feral females in field experiments is also consistent with a mating cost associated with restricted mobility (Rhainds, ). Under some climate‐change scenarios, increasing wing load of adults (small wings relative to body size) implies reduced motility of females and increased risk of FMF (McCauley et al., ).…”

“…As ectotherms, insects undergo seasonal shifts in phenology because larval development and timing of adult emergence depend on temperature (Forrest, ; Chuine & Régnière, ). Protogyny (early emergence of females relative to males) is rare in insects relative to protandry (Morbey & Ydenberg, ), thus climate‐induced protogyny is often presumed to increase FMF (Uyi et al., ; Bonal et al., ; McCauley et al., ; Ehl et al., ). However, protogyny is correlated with extended longevity of females (which counterbalances the risk of FMF; Degen et al., , ) and may in fact enhance mating success of early emergent females by reducing late‐season signal competition among conspecifics (Rhainds, ).…”

Rapid functional traits turnover in boreal dragonfly communities (Odonata)

“…Some studies show that the variation in emergence time can probably be attributed to environmental conditions such as temperature 44 , 45 , but also to habitat structure or food availability. The changes caused by acid deposition affect aquatic organisms in different ways 19 .…”

“…Warming can further reduce the period of winter stagnation in lakes (if the lakes don’t freeze) and thereby induce a possible winter circulation of the whole water volume. This would favour species that are more temperature tolerant 45 . Whether any of the species seemingly favoured in 2017 (Fig.…”

On the evolution of carry‐over effects

“… References for plausible examples of each kind of carry‐over effect: (1) Allen and Marshall (), (2) Craig and Foote (), (3) Moczek and Emlen (), (4) McCauley, Hammond, and Mabry (), (5) Hunt et al (), (6) Boes and Benard (). …”