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Title: Host Plant Effects on Sexual Selection Dynamics in Phytophagous Insects
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. more »« less
Sellers, Emma J; Tanino-Springsteen, Mykaela M; Hicks, Kailey G; Rogan, Caroline R; Reigrut, J D; Golbetz, Sierra; Dam, Kanshita; Guerra, Maxwell; Vidal, Mayra C; Wimp, Gina M; et al
(, Environmental Entomology)
Ginzel, Matthew
(Ed.)
Abstract Why and how herbivorous insects choose to feed on some plant species and not others can be influenced by many factors; however, it is not always clear why herbivorous insects will choose to lay their eggs on some plants over others. The Hopkins’ host selection principle (hereafter HHSP) hypothesizes that female insects prefer to lay eggs on host plants upon which they fed as larvae, but there are studies that both support and refute the hypothesis. Here, we test HHSP in a dietary generalist moth, fall webworm (Hyphantria cunea, hereafter FW). Previously, local host plant abundance has been the only factor found to determine FW host plant use; whether FW exhibit individual host plant preferences is unknown. We conducted preference tests with females of the two FW morphotypes (red-head and black-head), presenting females with four host plants: their one natal host plant, two other potential host plants, and one non-host plant for that morphotype that is a host plant for the other morphotype. Overwhelmingly, females of both morphotypes oviposited on a non-plant surface in the choice arena and those that did oviposit on a plant did not distinguish between host plants and non-host plants. Of the few FW females that oviposited on a host plant, only red-head females showed preference for their natal hosts. Our results support previous findings that HHSP is not a strong driver of host plant selection, suggesting that female FW are not selective in their choice of host plants, which may facilitate generalism in this species.
Raymond, St Leger; Jonathan, Wang
(, Open biology)
null
(Ed.)
The genus Metarhizium and Pochonia chlamydosporia comprise a monophyletic clade of highly abundant globally distributed fungi that can transition between long-term beneficial associations with plants to transitory pathogenic associations with frequently encountered protozoans, nematodes or insects. Some very common ‘specialist generalist’ species are adapted to particular soil and plant ecologies, but can overpower a wide spectrum of insects with numerous enzymes and toxins that result from extensive gene duplications made possible by loss of meiosis and associated genome defence mechanisms. These species use parasexuality instead of sex to combine beneficial mutations from separate clonal individuals into one genome (Vicar of Bray dynamics). More weakly endophytic species which kill a narrow range of insects retain sexuality to facilitate host–pathogen coevolution (Red Queen dynamics). Metarhizium species can fit into numerous environments because they are very flexible at the genetic, physiological and ecological levels, providing tractable models to address how new mechanisms for econutritional heterogeneity, host switching and virulence are acquired and relate to diverse sexual life histories and speciation. Many new molecules and functions have been discovered that underpin Metarhizium associations, and have furthered our understanding of the crucial ecology of these fungi in multiple habitats.
Abstract Pollen protein content has been demonstrated to be an essential nutritional component for bees and thus important in mediating plant–pollinator interactions. However, little is known on the drivers and consequences of among‐species variation in pollen protein content and how this can impact male and female reproductive success across plant species. Among‐species variation in resources allocated to pollen nutrition could further be constrained by life‐history strategies (e.g. survival‐reproduction trade‐offs) or evolutionary history.Here, we surveyed pollen protein content for 29 species within a diverse co‐flowering community and evaluated the effect of pollen protein on male and female reproductive success. We also tested the role of life history (annuals vs. perennials) and phylogeny in mediating differences in resource allocation to pollen nutrition.We found that pollen protein content influences components of male (bee visitor abundance and pollen dispersal) but not female (conspecific pollen deposition and pollen tube growth) reproductive success, suggesting this trait affects plants only via male function. This sex‐specific effect further suggests the potential for sexual conflicts driven by differential investment on this trait. We found no phylogenetic signal on pollen protein content. However, pollen protein content was higher in annual compared to perennial species suggesting survival versus reproduction trade‐offs also contribute to variation in pollen protein at the community level.Our study underscores the importance of understanding the ecological and evolutionary drivers of pollen protein content across plant species. Our results further suggest the existence of sexual conflicts and ecological trade‐offs mediated by differential investment in pollen nutritional quality, with important implications for community assembly and the structure of plant–pollinator interactions. Read the freePlain Language Summaryfor this article on the Journal blog.
Westeen, Erin P; Wogan, Guinevere_O U; Wang, Ian J; Yuan, Michael L
(, Evolution)
Parins-Fukuchi, Tomomi; Connallon, Tim
(Ed.)
Abstract Sexual dichromatism is thought to evolve primarily as a function of sexual selection, especially female choice. However, other forces, from sex-specific environmental conditions to social signaling in females, can also generate color differences between sexes. We studied dewlap dichromatism across 292 species of Anolis lizards. Dewlaps are colorful throat ornaments found on males of most anole species but are also present in females in many species. Although male and female dewlaps often have similar coloration, in some species, they are strikingly dichromatic. We found that ornament color is labile and that dichromatism results from the loss of costly pigments in females. This pattern could indicate a shift towards signal loss in females; however, the secondary gains of female dewlaps across the phylogeny suggest a potential advantageous function. Possible mechanisms for female dewlap coloration include social selection, nonsexual signaling, or detectability in different microhabitats (e.g., sensory drive). Female dewlap color overlap between co-occurring species is both less than expected by chance overall and reduced in species-rich communities, suggesting that dichromatism could be driven by competition. Our results highlight that selection on females drives the observed pattern of dichromatism, suggesting a potentially adaptive role for female ornaments and emphasizing the need for additional work to understand female ornament evolution.
BACKGROUND Charles Darwin’s Descent of Man, and Selection in Relation to Sex tackled the two main controversies arising from the Origin of Species: the evolution of humans from animal ancestors and the evolution of sexual ornaments. Most of the book focuses on the latter, Darwin’s theory of sexual selection. Research since supports his conjecture that songs, perfumes, and intricate dances evolve because they help secure mating partners. Evidence is overwhelming for a primary role of both male and female mate choice in sexual selection—not only through premating courtship but also through intimate interactions during and long after mating. But what makes one prospective mate more enticing than another? Darwin, shaped by misogyny and sexual prudery, invoked a “taste for the beautiful” without speculating on the origin of the “taste.” How to explain when the “final marriage ceremony” is between two rams? What of oral sex in bats, cloacal rubbing in bonobos, or the sexual spectrum in humans, all observable in Darwin’s time? By explaining desire through the lens of those male traits that caught his eyes and those of his gender and culture, Darwin elided these data in his theory of sexual evolution. Work since Darwin has focused on how traits and preferences coevolve. Preferences can evolve even if attractive signals only predict offspring attractiveness, but most attention has gone to the intuitive but tenuous premise that mating with gorgeous partners yields vigorous offspring. By focusing on those aspects of mating preferences that coevolve with male traits, many of Darwin’s influential followers have followed the same narrow path. The sexual selection debate in the 1980s was framed as “good genes versus runaway”: Do preferences coevolve with traits because traits predict genetic benefits, or simply because they are beautiful? To the broader world this is still the conversation. ADVANCES Even as they evolve toward ever-more-beautiful signals and healthier offspring, mate-choice mechanisms and courter traits are locked in an arms race of coercion and resistance, persuasion and skepticism. Traits favored by sexual selection often do so at the expense of chooser fitness, creating sexual conflict. Choosers then evolve preferences in response to the costs imposed by courters. Often, though, the current traits of courters tell us little about how preferences arise. Sensory systems are often tuned to nonsexual cues like food, favoring mating signals resembling those cues. And preferences can emerge simply from selection on choosing conspecifics. Sexual selection can therefore arise from chooser biases that have nothing to do with ornaments. Choice may occur before mating, as Darwin emphasized, but individuals mate multiple times and bias fertilization and offspring care toward favored partners. Mate choice can thus occur in myriad ways after mating, through behavioral, morphological, and physiological mechanisms. Like other biological traits, mating preferences vary among individuals and species along multiple dimensions. Some of this is likely adaptive, as different individuals will have different optimal mates. Indeed, mate choice may be more about choosing compatible partners than picking the “best” mate in the absolute sense. Compatibility-based choice can drive or reinforce genetic divergence and lead to speciation. The mechanisms underlying the “taste for the beautiful” determine whether mate choice accelerates or inhibits reproductive isolation. If preferences are learned from parents, or covary with ecological differences like the sensory environment, then choice can promote genetic divergence. If everyone shares preferences for attractive ornaments, then choice promotes gene flow between lineages. OUTLOOK Two major trends continue to shift the emphasis away from male “beauty” and toward how and why individuals make sexual choices. The first integrates neuroscience, genomics, and physiology. We need not limit ourselves to the feathers and dances that dazzled Darwin, which gives us a vastly richer picture of mate choice. The second is that despite persistent structural inequities in academia, a broader range of people study a broader range of questions. This new focus confirms Darwin’s insight that mate choice makes a primary contribution to sexual selection, but suggests that sexual selection is often tangential to mate choice. This conclusion challenges a persistent belief with sinister roots, whereby mate choice is all about male ornaments. Under this view, females evolve to prefer handsome males who provide healthy offspring, or alternatively, to express flighty whims for arbitrary traits. But mate-choice mechanisms also evolve for a host of other reasons Understanding mate choice mechanisms is key to understanding how sexual decisions underlie speciation and adaptation to environmental change. New theory and technology allow us to explicitly connect decision-making mechanisms with their evolutionary consequences. A century and a half after Darwin, we can shift our focus to females and males as choosers, rather than the gaudy by-products of mate choice. Mate choice mechanisms across domains of life. Sensory periphery for stimulus detection (yellow), brain for perceptual integration and evaluation (orange), and reproductive structures for postmating choice among pollen or sperm (teal). ILLUSTRATION: KELLIE HOLOSKI/ SCIENCE
Jarrett, Benjamin JM, and Miller, Christine W. Host Plant Effects on Sexual Selection Dynamics in Phytophagous Insects. Retrieved from https://par.nsf.gov/biblio/10536350. Annual Review of Entomology 69.1 Web. doi:10.1146/annurev-ento-022823-020258.
Jarrett, Benjamin JM, & Miller, Christine W. Host Plant Effects on Sexual Selection Dynamics in Phytophagous Insects. Annual Review of Entomology, 69 (1). Retrieved from https://par.nsf.gov/biblio/10536350. https://doi.org/10.1146/annurev-ento-022823-020258
@article{osti_10536350,
place = {Country unknown/Code not available},
title = {Host Plant Effects on Sexual Selection Dynamics in Phytophagous Insects},
url = {https://par.nsf.gov/biblio/10536350},
DOI = {10.1146/annurev-ento-022823-020258},
abstractNote = {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.},
journal = {Annual Review of Entomology},
volume = {69},
number = {1},
publisher = {Annual Reviews},
author = {Jarrett, Benjamin JM and Miller, Christine W},
}
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