Reproductive behaviour indicates specificity in resource use: phylogenetic examples from temperate and tropical insects

Abstract

Specificity (= the degree of ecological specialisation) is one of the fundamental concepts of the science of ecology. Ambiguities on how to define and measure specificity have however complicated respective research efforts. Here we propose that, in insects, a behavioural trait – adult oviposition latency in captivity without a favourable host plant – correlates with a species’ specificity in larval host use. In the absence of a suitable host, monophagous insects are expected to wait for a long time before commencing oviposition, with the long waiting time corresponding to careful host location behaviour in nature. Polyphagous insects, in contrast, should be selected for an increased oviposition rate at the expense of the quality of oviposition substrate encountered and will on average have a short latency time. Using experimentally derived data on oviposition latency, we performed a phylogenetically informed analysis based on Bayesian inference to show that this variable correlates with host specificity (larval diet breadth) in a sample of north European species of geometrid moths. A closely related index – the probability to lay any eggs on an unfavourable substrate – shows an analogous pattern. To provide an example of how these indices can be applied, we compare our sample of geometrid moths from northern Europe with a sample from equatorial Africa. A comparative analysis based on an original phylogenetic reconstruction found no differences between the two study sites in parameters of oviposition behaviour. We conclude that behavioural tests can provide information about ecological interactions when the latter can not be directly recorded. Our example study also hints at the possibility that host specificity of herbivores is not necessarily higher in a tropical region compared to a temperate one.

Size‐related life‐history traits in geometrid moths: a comparison of a temperate and a tropical community

“…The phylogenetic tree of Geometridae was constructed on the basis of nucleotide sequences of eight gene fragments (see Appendices S1, S2, and Holm et al, 2018Holm et al, , 2019 for details and references). Four subfamily-specific ultrametric trees were created using beast v.1.8.1 (Drummond et al, 2012) on the CIPRES Science Gateway (Miller et al, 2010).…”

“…The study area represents species-rich, medium-altitude, moist, evergreen tropical forest (Struhsaker, 1997). Adult specimens of geometrid moths were obtained though ex ovo rearing of the offspring of the females collected in light traps (Holm et al, 2018), complemented by moths originating from wild-collected larvae. The larvae were reared individually in 50-ml plastic vials under ambient conditions at Kibale.…”

“…1; Table 1). The world may not be so different for a tropical and a temperate moth after all (for a similar conclusion relying on the study of oviposition behaviour, see Holm et al, 2018Holm et al, , 2019, although a much broader sample of sites is needed to confirm any systematic differences between the moths representing tropical and temperate habitats.…”

“…E-mail: sille.holm@ut.ee (e.g. Holm et al, 2016Holm et al, , 2018, with obvious limitations on affordable sample sizes.…”

A comparative morphometric study of sensory capacity in geometrid moths

“…Locating larval host plants appears to be predominantly the responsibility of ovipositing females, though experimental studies on oviposition behaviour in these moths are rather scarce and mainly restricted to pest species (but see, e.g. Tammaru & Javoiš, ; Holm et al., ). However, there are also examples of species with indiscriminate oviposition, which is compensated for by the ballooning behaviour of the early‐instar larvae (Britton & New, ; Edland, ; Tammaru et al., ).…”