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Simple Summary: Predators drive prey trait diversification and promote ecological speciation. The impacts of predation are not only on the final state of antipredation traits, but also on the development of antipredation traits. Species of the dragonfly genus Leucorrhinia are distributed in both habitats dominated by predatory fish (fish lakes) and habitats dominated by predatory invertebrates (invertebrate lakes). In larval dragonflies, the spine is one of the most efficient traits deterring gape-limited fish predators. However, the spine is not useful in invertebrate lakes. In this study, we compared the developmental patterns of spines in both habitats. We constructed the scaling relationship between spine length and body size and compared the inflexion point on those curves in five species of Leucorrhinia dragonfly larvae. Here, we found that fish-lake Leucorrhinia species kept a higher spine growth rate than species from invertebrate lakes, and Leucorrhinia species from fish lakes displayed accelerated spine growth rate at larger body size compared to invertebrate-lake species. Our results highlight that development patterns, as well as the final states of antipredator traits, are essential to understanding predator–prey interactions. Predation is a major factor driving prey trait diversification and promoting ecological speciation. Consequently, antipredator traits are widely studied among prey species. However, comparative studies that examine how different predators shape the ontogenetic growth of antipredator traits are scarce. In larval dragonflies, abdominal spines are effective traits against predatory fish in fish lakes, which prefer larger prey. However, defensive spines increase mortality in habitats dominated by invertebrate predators (invertebrate lakes), which prefer smaller prey. Thus, species from fish lakes may accelerate spine growth at a later body size compared to species from invertebrate lakes when growing into the preferred prey size range of predatory fish. In this study, we constructed the allometric relationship between spine length and body size and compared the inflexion point of those growth curves in five species of Leucorrhinia dragonfly larvae. We found that fish-lake Leucorrhinia species accelerated spine growth at a larger body size than congenerics from invertebrate lakes. Further, rather than extending spine length constantly through development, fish-lake species rapidly accelerated spine growth at a larger body size. This is likely to be adaptive for avoiding invertebrate predation at an early life stage, which are also present in fish lakes, though in smaller numbers. Our results highlight that comparative studies of ontogenetic patterns in antipredator traits might be essential to develop an integrated understanding of predator–prey interactions. [ABSTRACT FROM AUTHOR]

Agriocnemis femina (Brauer, 1868) and Ischnura senegalensis (Rambur, 1842) are two damselflies inhabiting paddy lands. As an intermediate predator, they play an important role in controlling certain crop pest and mosquitoes. In this study, we sequenced complete mitogenomes of these two species. The total length of mitogenomes is 15,936 bp in A. femina and 15,762 bp in I. senegalensis. Both of mitogenomes consist of 13 protein-coding genes, 22 tRNA genes, two rRNA genes, and one control region. The close relationship between I. senegalensis and I. elegans was further proved by phylogenetic analysis. Our phylogenetic analysis indicated a clear two lineages in Coenagrionidae (Core and ridge-faced Coenagrionidae). Ridge-faced Coenagrionidae consisted of Megaloprepus caerulatus and Ceriagrion fallax. In core Coenagrionidae, Ischnura and Enallagma are most closely related; they formed one clade with Agriocnemis and then grouped together with Paracerion. Our study provides new genetic information for further study in phylogenetic analysis of Coenagrionidae. [ABSTRACT FROM AUTHOR]

1. Behavioural adaptations to avoid and evade predators are common. Many studies have investigated population divergence in response to changes in predation regime within species, but studies exploring interspecific patterns are scant. Studies on interspecific divergence can infer common outcomes from evolutionary processes and highlight the role of environmental constraints in shaping species traits. 2. Species of the dragonfly genus Leucorrhinia underwent well‐studied shifts from habitats being dominated by predatory fish (fish lakes) to habitat being dominated by predatory invertebrates (dragonfly lakes). This change in top predators resulted in a set of adaptive trait modifications in response to the different hunting styles of both predator types: whereas predatory fish actively search and pursue prey, invertebrate predator follow a sit‐and‐wait strategy, not pursuing prey. 3. Here it is shown that the habitat shift‐related change in selection regime on larval Leucorrhinia caused species in dragonfly lakes to evolve increased larval foraging and activity, and results suggest that they lost the ability to recognise predatory fish. 4. The results of the present study highlight the impact of predators on behavioural trait diversification with habitat‐specific predation regimes selecting for distinct behavioural expression. [ABSTRACT FROM AUTHOR]

Sexual size dimorphism ( SSD) reflects adaptive differences in male and female reproductive roles. Understanding the mechanisms generating SSD is of broad ecological and evolutionary interest, because body size is closely linked to fitness., Sex-specific phenotypic plasticity in growth as a response to environmental conditions represents one of the major sources mediating variation in SSD., We investigated phenotypic plasticity associated with predation and seasonal time constraints in development as a source of SSD in the Azure damselfly, Coenagrion puella. We complemented this with an analysis of trait correlations (integration) of body size with behavioural, physiological and life-history traits to investigate how dimorphism manifests., Our results reveal that: (i) plasticity in SSD is mediated by environmental variation; and (ii) environment-dependent, sex-specific changes in the association of body size with growth rate and fat storage mediated changes in the offset of SSD., Our results highlight sex-specific trait responses to the environment channel manifestation of SSD. These findings may be crucial to understanding large parts of the widely documented intraspecific variation of SSD. [ABSTRACT FROM AUTHOR]

1. An organism’s growth parameters are expected to depend on environmental constraints, such as predation risk and food supply. However, antipredator responses, food intake, and thus growth of an animal may be mediated by behavioural traits, which are likely to differ among developmental stages. In this study, it was investigated how the relationship between growth and behavioural antipredator responses changes during ontogeny in the time-constrained dragonfly species Libellula depressa, and which factors influenced specific behavioural decisions at different points in ontogeny. 2. The results revealed that behavioural strategies differed between larval developmental sages, depending on associations between larval growth, food supply, and predation risk. Early in ontogeny, faster development was correlated with high larval activity and high food supply. This resulted in high activity levels under high food conditions irrespectively of predator presence, and under low food supply in predator absence only. In the intermediate stage of development, all larvae displayed a high activity level, which was correlated in general with fast development. However, growth later in ontogeny was not only influenced by the activity level, but also by predator presence and food supply, with larvae reared under high food supply and/or in presence of predators attaining a higher final mass. Thus, not only the way in which larval growth parameters and behaviour are related changed during development, but also whether the factors influenced larval growth and behaviour. Once the larvae reached the ultimate stage of development, in which they overwinter, behavioural patterns observed were consistent with model predictions. 3. It is advocated that behavioural plasticity of prey organisms in different developmental stages should be analysed in the context of associated growth variables. [ABSTRACT FROM AUTHOR]

Prey species are often non-randomly distributed along predator gradients but according to how they trade off growth against predation risk. The foraging-mediated growth/predation risk trade-off is well established, with increased foraging accelerating growth but also increasing predator induced mortality. While adaptations in digestive physiology may partly modify the relationship between foraging and growth in response to predation risk, studies exploring the impact of digestive physiology on growth in prey subjected to predation risk are still scarce. Larvae of the dragonfly genus Leucorrhinia segregate at the species level between lakes either being dominated by predatory fish (fish-lakes) or predatory invertebrates (dragonfly-lakes). Predators of these two lake types differ dramatically in their hunting style like searching and pursuing mode causing different selection pressure on prey traits including foraging. In a laboratory experiment we estimated growth rate, digestive physiology (ingested food, growth efficiency, assimilation efficiency, conversion efficiency) and metabolic rate (oxygen consumption) in the presence and absence of predator cues. Whereas fish-lake and dragonfly-lake Leucorrhinia species did not differ in growth rate, they evolved different pathways of digestive physiology to achieve similar growth rate. Because fish-lake species expressed a higher metabolic rate than dragonfly-lake species, we assume energy to be differently allocated and used for metabolic demands between species of both predator environments. Further, growth rate, but not digestive physiology was plastic in response to the presence of predator cues. Our results highlight the impact of digestive physiology in shaping the foraging-mediated growth/predation risk trade-off, with digestive physiology contributing to species distribution patterns along predator gradients. [ABSTRACT FROM AUTHOR]

Agriocnemis femina (Brauer, 1868) and Ischnura senegalensis (Rambur, 1842) are two damselflies inhabiting paddy lands. As an intermediate predator, they play an important role in controlling certain crop pest and mosquitoes. In this study, we sequenced complete mitogenomes of these two species. The total length of mitogenomes is 15,936 bp in A. femina and 15,762 bp in I. senegalensis . Both of mitogenomes consist of 13 protein-coding genes, 22 tRNA genes, two rRNA genes, and one control region. The close relationship between I. senegalensis and I. elegans was further proved by phylogenetic analysis. Our phylogenetic analysis indicated a clear two lineages in Coenagrionidae (Core and ridge-faced Coenagrionidae). Ridge-faced Coenagrionidae consisted of Megaloprepus caerulatus and Ceriagrion fallax . In core Coenagrionidae, Ischnura and Enallagma are most closely related; they formed one clade with Agriocnemis and then grouped together with Paracerion . Our study provides new genetic information for further study in phylogenetic analysis of Coenagrionidae., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.)

Presence or absence of predators selects for different kind of morphologies. Hence, we expect variation in traits that protect against predators to vary over geographical areas where predators vary in past and present abundance. Abdominal larval spines in dragonfly larvae provide protection against fish predators. We studied geographical variation in larval spine length of the dragonfly Leucorrhinia dubia across Western Europe using a phylogenetic approach. Larvae were raised in a common garden laboratory experiment in the absence of fish predators. Results show that larvae from northern Europe (Sweden and Finland) had significantly longer larval spines compared to larvae from western and central Europe. A phylogeny based on SNP data suggests that short larval spines is the ancestral stage in the localities sampled in this study, and that long spines have evolved in the Fenno-Scandian clade. The role of predators in shaping the morphological differences among the sampled localities is discussed.