The phytophagous insect superfamily Coreoidea (Heteroptera) is a diverse group of ~3100 species in five extant families, with many of agricultural importance and model organisms in behavioural studies. Most species (~2800 species) are classified in the family Coreidae (four subfamilies, 37 tribes). While previous phylogenetic studies have primarily focused on the larger and more diverse subfamilies and tribes of Coreidae, several smaller tribes remain poorly studied in a phylogenetic context. Here, we investigated the phylogenetic positions of three less diverse tribes using ultraconserved elements: Agriopocorini, Amorbini, and Manocoreini. Our study is the first to test phylogenetic hypotheses for the Agriopocorini and Amorbini in a cladistic analysis. All three tribes were recovered within the subfamily Coreinae with robust support. The monophyletic Agriopocorini were supported as the sister-group of Colpurini, the monophyletic Amorbini as sister to Mictini, and the monogeneric Manocoreini as sister to Dasynini + Homoeocerini. We briefly discuss the evolution of wing development in Coreidae, putative synapomorphies for clades of interest, and taxonomic considerations. Our study emphasizes the importance of including smaller, less diverse groups in phylogenetic analyses. By doing so, we gain valuable insights into evolutionary relationships, identify future investigations of trait evolution, and resolve systematic controversies.
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Abstract Sexually selected weapons, such as the antlers of deer, claws of crabs, and tusks of beaked whales, are strikingly diverse across taxa and even within groups of closely related species. Phylogenetic comparative studies have typically taken a simplified approach to investigate the evolution of weapon diversity, examining the gains and losses of entire weapons, major shifts in size or type, or changes in location. Less understood is how individual weapon components evolve and assemble into a complete weapon. We addressed this question by examining weapon evolution in the diverse, multi-component hind-leg and body weapons of leaf-footed bugs, superfamily Coreoidea (Hemiptera: Heteroptera). Male leaf-footed bugs use their morphological weapons to fight for access to mating territories. We used a large multilocus dataset comprised of ultraconserved element loci for 248 species and inferred evolutionary transitions among component states using ancestral state estimation. Our results suggest that weapons added components over time with some evidence of a cyclical evolutionary pattern—gains of components followed by losses and then gains again. Furthermore, our best estimate indicated that certain trait combinations evolved repeatedly across the phylogeny, suggesting that they function together in battle or that they are genetically correlated. This work reveals the remarkable and dynamic evolution of weapon form in the leaf-footed bugs and provides insights into weapon assembly and disassembly over evolutionary time.
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Abstract Theory predicts that traits with heightened condition dependence, such as sexually selected traits, should be affected by inbreeding to a greater degree than other traits. The presence of environmental stress may compound the negative consequences of inbreeding depression. In this study, we examined inbreeding depression across multiple traits and whether it increased with a known form of environmental stress. We conducted our experiment using both sexes of the sexually dimorphic leaf-footed cactus bug, Narnia femorata (Hemiptera: Coreidae). Adult male cactus bugs have enlarged hind legs used as weapons in male–male contests; these traits, and their homologue in females, have been previously found to exhibit high condition dependence. In this study, we employed a small developmental group size as an environmental stress challenge. Nymph N. femorata aggregate throughout their juvenile stages, and previous work has shown the negative effects of small group size on survivorship and body size. We found evidence of inbreeding depression for survival and seven of the eight morphological traits measured in both sexes. Inbreeding depression was higher for the size of the male weapon and the female homolog. Additionally, small developmental group size negatively affected survival to adulthood. However, small group size did not magnify the effects of inbreeding on morphological traits. These findings support the hypothesis that traits with heightened condition dependence exhibit higher levels of inbreeding depression.
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Abstract A longstanding goal of evolutionary biology is to understand among-individual variation in resource allocation decisions and the timing of these decisions. Recent studies have shown that investment in elaborate and costly weapons can result in trade-offs with investment in testes. In this study, we ask the following questions: At what point plasticity in resource allocation to these different structures ceases during development, if at all? Furthermore, can individuals tailor their reproductive behavior to accompany structural changes? We experimentally addressed these questions in the insect Narnia femorata, quantifying resource reallocation across development for the first time, using a phenotypic engineering approach. To investigate whether allocation plasticity diminishes throughout ontogeny, we induced weapon loss at a range of different developmental stages and examined subsequent testes mass and reproductive behavior. We found that relative testes mass increased as weapon investment decreased, implying a direct trade-off between testes and weapon investment. However, autotomy postadulthood ceased to induce larger testes mass. Intriguingly, losing a weapon while young was associated with extended adult mating duration, potentially enabling compensation for reduced fighting ability. Our results highlight the importance of examining the ontogeny of trade-offs between reproductive traits and the flexibility of the relationship between reproductive morphology and behavior.
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Natural selection is notoriously dynamic in nature, and so, too, is sexual selection. The interactions between phytophagous insects and their host plants have provided valuable insights into the many ways in which ecological factors can influence sexual selection. In this review, we highlight recent discoveries and provide guidance for future work in this area. Importantly, host plants can affect both the agents of sexual selection (e.g., mate choice and male–male competition) and the traits under selection (e.g., ornaments and weapons). Furthermore, in our rapidly changing world, insects now routinely encounter new potential host plants. The process of adaptation to a new host may be hindered or accelerated by sexual selection, and the unexplored evolutionary trajectories that emerge from these dynamics are relevant to pest management and insect conservation strategies. Examining the effects of host plants on sexual selection has the potential to advance our fundamental understanding of sexual conflict, host range evolution, and speciation, with relevance across taxa.
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Herbivores often grapple with structural defences in their host plants, which may pose especially difficult challenges for juveniles due to their underdeveloped feeding morphology. The degree to which juvenile herbivore survival is limited by structural defences as well as the strategies used to overcome them are not well understood. We hypothesized that juveniles benefit from feeding near adults because adults pierce through physical barriers while feeding, enabling juveniles to access nutrients that they otherwise could not. We tested this feeding facilitation hypothesis in the leaf-footed bug
Leptoglossus zonatus (Hemiptera: Coreidae). Bugs were raised with an adult or a juvenile conspecific and fed a diet of pecans with or without shells. As predicted, we found that juveniles suffered greater mortality when fed nuts with shells than when fed nuts without shells. Contrary to our expectations, the presence of an adult feeding on the same nut did not lessen this effect. Therefore, the presence of an adult does not ameliorate the feeding difficulties faced by juvenileL. zonatus, despite evidence for feeding facilitation in related insect species. This study adds to our understanding of how host plant defences can limit the survival of even highly generalist herbivores. -
Intra- and interspecific communication is crucial to fitness via its role in facilitating mating, territoriality and defence. Yet, the evolution of animal communication systems is puzzling—how do they originate and change over time? Studying stridulatory morphology provides a tractable opportunity to deduce the origin and diversification of a communication mechanism. Stridulation occurs when two sclerotized structures rub together to produce vibratory and acoustic (vibroacoustic) signals, such as a cricket ‘chirp’. We investigated the evolution of stridulatory mechanisms in the superfamily Coreoidea (Hemiptera: Heteroptera), a group of insects known for elaborate male fighting behaviours and enlarged hindlegs. We surveyed a large sampling of taxa and used a phylogenomic dataset to investigate the evolution of stridulatory mechanisms. We identified four mechanisms, with at least five evolutionary gains. One mechanism, occurring only in male Harmostini (Rhopalidae), is described for the first time. Some stridulatory mechanisms appear to be non-homoplastic apomorphies within Rhopalidae, while others are homoplastic or potentially homoplastic within Coreidae and Alydidae, respectively. We detected no losses of these mechanisms once evolved, suggesting they are adaptive. Our work sets the stage for further behavioural, evolutionary and ecological studies to better understand the context in which these traits evolve and change.more » « less