Temperature shapes oviposition site selection and post-oviposition egg transport in an insect with parental care

Depositing eggs in an area with adequate temperature is often crucial for mothers and their offspring, as the eggs are immobile and therefore cannot avoid exposure to sub-optimal temperatures. However, the importance of temperature on oviposition site selection is less clear when mothers have the capability to avoid these potential adverse effects by both moving their eggs after oviposition and providing other forms of egg care. In this study, we addressed this question in the European earwig, an insect in which mothers care for the eggs during several months in winter and often move them during this period. Using 60 females from two Canadian populations (St John's and Harvey station) set up under controlled thermal gradients, we demonstrated that earwig females both select oviposition sites according to temperature and move their eggs after oviposition to reach warmer environmental temperatures. While this set of behavioural thermoregulation is present in the two studied populations, its modality of expression was population-specific: St John's females explored greater ranges of temperatures before oviposition, laid their eggs in warmer areas, and moved their eggs quicker toward warm locations. Overall, our study reveals that earwig females have evolved both pre-and post-oviposition behavioural strategies to mitigate the risks inherent to tending eggs during winter. More generally, it also reveals that egg care and egg transport do not prevent behavioural thermoregulation via oviposition site selection and highlights the diversity of behaviours that insects can adopt to enhance their tolerance to global climate change.

The Evolutionary Relevance of Social Learning and Transmission in Non-Social Arthropods with a Focus on Oviposition-Related Behaviors

Research on social learning has centered around vertebrates, but evidence is accumulating that small-brained, non-social arthropods also learn from others. Social learning can lead to social inheritance when socially acquired behaviors are transmitted to subsequent generations. Using oviposition site selection, a critical behavior for most arthropods, as an example, we first highlight the complementarities between social and classical genetic inheritance. We then discuss the relevance of studying social learning and transmission in non-social arthropods and document known cases in the literature, including examples of social learning from con- and hetero-specifics. We further highlight under which conditions social learning can be adaptive or not. We conclude that non-social arthropods and the study of oviposition behavior offer unparalleled opportunities to unravel the importance of social learning and inheritance for animal evolution.

The evolutionary relevance of social learning and transmission of behaviors in non-social arthropods

Research on social learning has centered around vertebrates, but evidence is accumulating that small-brained, non-social arthropods also learn from others. Social learning can lead to social inheritance when socially acquired behaviors are transmitted to subsequent generations. Here, we first highlight the complementarities between social and classical genetic inheritance, using oviposition site selection, a behavior critical for many non-social arthropods, as a hypothetical example. We then discuss the relevance of studying social learning and transmission in non-social arthropods and document known cases in the literature, including examples of social learning from con and hetero-specifics. We subsequently highlight under which conditions social learning can be adaptive or not. We conclude that non-social arthropods and the study of oviposition behavior offer unparalleled opportunities to increase our understanding of social learning and inheritance.

Sex-Specific Oviposition Site Selection and Hatching Success in an Arboreal Treefrog: Implications of a Paternal Nest-Site Selection

Oviposition sites selected by parents is an important factor that affects offspring survival and parental fitness. A good nest site offers offspring protection from competition, predation, and harsh environmental conditions. In amphibians, though oviposition sites are generally determined by females, the distinction between male and female choice can be blurred in species with resource defense mating systems, where males occupy the territory that eggs are deposited before advertising for females. Using a phytotelm-breeding frog (Kurixalus eiffingeri) with male territoriality and biparental care, we examined 310 oviposition sites to determine (1) male choice based on physical characteristics of the site (stump height, inner diameter, stump depth, water depth), and (2) female choice based on site characteristics and male characteristics (snout-vent length and body condition). We hypothesized that either one or both sexes would select oviposition site based on characteristics correlate with higher offspring survivorship. We found that males preferred sites with deeper pools of water, while females showed no preference for sites or males based on the characteristics observed. While we cannot prove any nest traits directly benefit offspring, we contend that increased water depth within the phytotelm may 1) protect male frog from snake predation, which would allow for continued paternal care that increases the hatching success and 2) improve the offspring survival during the larval period. Our findings provide empirical evidence of male-driven oviposition site selection in an amphibian and highlight often overlooked role that males play in increasing their reproductive output by selecting for sites that benefit their offspring.

Influence of the presence of invasive mosquitofish and submerged vegetation on oviposition site selection by gray treefrogs (Hyla versicolor)

Amphibians often select oviposition sites based on a variety of cues that indicate the level of risk in the oviposition habitat. Surprisingly, the role of aquatic vegetation or habitat structure/complexity in anuran oviposition site selection has not been extensively studied even though it might affect perceived risk. We examined the effects of free-ranging invasive western mosquitofish (Gambusia affinis) and artificial vegetation/habitat structure on colonisation of experimental pools by gray treefrogs (Hyla versicolor). Hyla versicolor avoided ovipositing in mesocosms with G. affinis. The presence of artificial vegetation/habitat structure had no effect on oviposition site selection by H. versicolor, whether alone or in interaction with G. affinis. Our experiment provides evidence for the avoidance of fish, and more specifically G. affinis, by ovipositing H. versicolor; but provides no evidence for a role of vegetation/habitat structure.

Social signals mediate oviposition site selection in Drosophila suzukii

The information that female insects perceive and use during oviposition site selection is complex and varies by species and ecological niche. Even in relatively unexploited niches, females interact directly and indirectly with conspecifics at oviposition sites. These interactions can take the form of host marking and re-assessment of prior oviposition sites during the decision-making process. Considerable research has focused on the niche breadth and host preference of the polyphagous invasive pest Drosophila suzukii Matsumura (Diptera: Drosophilidae), but little information exists on how conspecific signals modulate oviposition behavior. We investigated three layers of social information that female D. suzukii may use in oviposition site selection—(1) pre-existing egg density, (2) pre-existing larval occupation, and (3) host marking by adults. We found that the presence of larvae and host marking, but not egg density, influenced oviposition behavior and that the two factors interacted over time. Adult marking appeared to deter oviposition only in the presence of an unmarked substrate. These results are the first behavioral evidence for a host marking pheromone in a species of Drosophila. These findings may also help elucidate D. suzukii infestation and preference patterns within crop fields and natural areas.