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1. Geographic variation in sexual communication in the cotton bollworm, Helicoverpa armigera

   https://doi.org/10.1002/ps.5893  

   Gao, Ke ; Torres‐Vila, Luis M. ; Zalucki, Myron P. ; Li, Yiping ; Griepink, Frans ; Heckel, David G. ; Groot, Astrid T. ( June 2020 , Pest Management Science)

   Geographic variation in male response to sex pheromone lures has been studied in the field in a number of moth species. However, only a few studies have investigated geographic variation in female calling and sex pheromone under field conditions. For an effective field implementation of sex pheromone lures, it is essential to know the local sex pheromone blend and local timing of sexual communication. We investigated the level and extent of geographic variation in the sexual communication of the important agricultural pestHelicoverpa armigera(Lepidoptera, Noctuidae) in three continents.

   We found there is no genetic variation in the calling behavior ofH. armigera. In the female sex pheromone, we found more between‐population variation than within‐population variation. In male response experiments, we found geographic variation as well. Strikingly, when adding the antagonistic compound Z11‐16:OAc to the pheromone blend ofH. armigera, significantly fewer males were caught in Australia and China, but not in Spain. This variation is likely not only due to local environmental conditions, such as photoperiod and temperature, but also to the presence of other closely related species with which communication interference may occur.

   Finding geographic variation in both the female sexual signal and the male response in this pest calls for region‐specific pheromone lures. Our study shows that the analysis of geographic variation in moth female sex pheromones as well as male responses is important for effectively monitoring pest species that occur around the globe. © 2020 The Authors.Pest Management Sciencepublished by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

    

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2. bric à brac controls sex pheromone choice by male European corn borer moths

   https://doi.org/10.1038/s41467-021-23026-x  

   Unbehend, Melanie ; Kozak, Genevieve M. ; Koutroumpa, Fotini ; Coates, Brad S. ; Dekker, Teun ; Groot, Astrid T. ; Heckel, David G. ; Dopman, Erik B. ( May 2021 , Nature Communications)

   The sex pheromone system of ~160,000 moth species acts as a powerful form of assortative mating whereby females attract conspecific males with a species-specific blend of volatile compounds. Understanding how female pheromone production and male preference coevolve to produce this diversity requires knowledge of the genes underlying change in both traits. In the European corn borer moth, pheromone blend variation is controlled by two alleles of an autosomal fatty-acyl reductase gene expressed in the female pheromone gland (pgFAR). Here we show that asymmetric male preference is controlled bycis-acting variation in a sex-linked transcription factor expressed in the developing male antenna,bric à brac(bab). A genome-wide association study of preference using pheromone-trapped males implicates variation in the 293 kbbabintron 1, rather than the coding sequence. Linkage disequilibrium betweenbabintron 1 andpgFARfurther validatesbabas the preference locus, and demonstrates that the two genes interact to contribute to assortative mating. Thus, lack of physical linkage is not a constraint for coevolutionary divergence of female pheromone production and male behavioral response genes, in contrast to what is often predicted by evolutionary theory.

    

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3. Clonality, local population structure and gametophyte sex ratios in cryptic species of the Sphagnum magellanicum complex

   https://doi.org/10.1093/aob/mcad077  

   Shaw, A. Jonathan ; Duffy, Aaron M. ; Nieto-Lugilde, Marta ; Aguero, Blanka ; Schuette, Scott ; Robinson, Sean ; Loveland, James ; Hicks, Karen A. ; Weston, David ; Piatkowski, Bryan ; et al ( July 2023 , Annals of Botany)

   Sphagnum (peatmoss) comprises a moss (Bryophyta) clade with ~300–500 species. The genus has unparalleled ecological importance because Sphagnum-dominated peatlands store almost a third of the terrestrial carbon pool and peatmosses engineer the formation and microtopography of peatlands. Genomic resources for Sphagnum are being actively expanded, but many aspects of their biology are still poorly known. Among these are the degree to which Sphagnum species reproduce asexually, and the relative frequencies of male and female gametophytes in these haploid-dominant plants. We assess clonality and gametophyte sex ratios and test hypotheses about the local-scale distribution of clones and sexes in four North American species of the S. magellanicum complex. These four species are difficult to distinguish morphologically and are very closely related. We also assess microbial communities associated with Sphagnum host plant clones and sexes at two sites.

   Four hundred and five samples of the four species, representing 57 populations, were subjected to restriction site-associated DNA sequencing (RADseq). Analyses of population structure and clonality based on the molecular data utilized both phylogenetic and phenetic approaches. Multi-locus genotypes (genets) were identified using the RADseq data. Sexes of sampled ramets were determined using a molecular approach that utilized coverage of loci on the sex chromosomes after the method was validated using a sample of plants that expressed sex phenotypically. Sex ratios were estimated for each species, and populations within species. Difference in fitness between genets was estimated as the numbers of ramets each genet comprised. Degrees of clonality [numbers of genets/numbers of ramets (samples)] within species, among sites, and between gametophyte sexes were estimated. Sex ratios were estimated for each species, and populations within species. Sphagnum-associated microbial communities were assessed at two sites in relation to Sphagnum clonality and sex.

   All four species appear to engage in a mixture of sexual and asexual (clonal) reproduction. A single ramet represents most genets but two to eight ramets were dsumbers ansd text etected for some genets. Only one genet is represented by ramets in multiple populations; all other genets are restricted to a single population. Within populations ramets of individual genets are spatially clustered, suggesting limited dispersal even within peatlands. Sex ratios are male-biased in S. diabolicum but female-biased in the other three species, although significantly so only in S. divinum. Neither species nor males/females differ in levels of clonal propagation. At St Regis Lake (NY) and Franklin Bog (VT), microbial community composition is strongly differentiated between the sites, but differences between species, genets and sexes were not detected. Within S. divinum, however, female gametophytes harboured two to three times the number of microbial taxa as males.

   These four Sphagnum species all exhibit similar reproductive patterns that result from a mixture of sexual and asexual reproduction. The spatial patterns of clonally replicated ramets of genets suggest that these species fall between the so-called phalanx patterns, where genets abut one another but do not extensively mix because of limited ramet fragmentation, and the guerrilla patterns, where extensive genet fragmentation and dispersal result in greater mixing of different genets. Although sex ratios in bryophytes are most often female-biased, both male and female biases occur in this complex of closely related species. The association of far greater microbial diversity for female gametophytes in S. divinum, which has a female-biased sex ratio, suggests additional research to determine if levels of microbial diversity are consistently correlated with differing patterns of sex ratio biases.

    

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4. Differentiation in putative male sex pheromone components across and within populations of the African butterfly Bicyclus anynana as a potential driver of reproductive isolation

   https://doi.org/10.1002/ece3.2298  

   Bacquet, Paul M. B. ; de Jong, Maaike A. ; Brattström, Oskar ; Wang, Hong‐Lei ; Molleman, Freerk ; Heuskin, Stéphanie ; Lognay, George ; Löfstedt, Christer ; Brakefield, Paul M. ; Vanderpoorten, Alain ; et al ( July 2016 , Ecology and Evolution)

   Sexual traits are often the most divergent characters among closely related species, suggesting an important role of sexual traits in speciation. However, to prove this, we need to show that sexual trait differences accumulate before or during the speciation process, rather than being a consequence of it. Here, we contrast patterns of divergence among putative male sex pheromone (pMSP) composition and the genetic structure inferred from variation in the mitochondrial cytochrome oxidase 1 and nuclearCADloci in the African butterflyBicyclus anynana(Butler, 1879) to determine whether the evolution of “pheromonal dialects” occurs before or after the differentiation process. We observed differences in abundance of some sharedpMSPcomponents as well as differences in the composition of thepMSPamongB. anynanapopulations. In addition,B. anynanaindividuals from Kenya displayed differences in thepMSPcomposition within a single population that appeared not associated with genetic differences. These differences inpMSPcomposition both between and withinB. anynanapopulations were as large as those found between differentBicyclusspecies. Our results suggest that “pheromonal dialects” evolved within and among populations ofB. anynanaand may therefore act as precursors of an ongoing speciation process.

    

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5. A genetic switch for male UV iridescence in an incipient species pair of sulphur butterflies

   https://doi.org/10.1073/pnas.2109255118  

   Ficarrotta, Vincent ; Hanly, Joseph J. ; Loh, Ling S. ; Francescutti, Caroline M. ; Ren, Anna ; Tunström, Kalle ; Wheat, Christopher W. ; Porter, Adam H. ; Counterman, Brian A. ; Martin, Arnaud ( January 2022 , Proceedings of the National Academy of Sciences)

   Mating cues evolve rapidly and can contribute to species formation and maintenance. However, little is known about how sexual signals diverge and how this variation integrates with other barrier loci to shape the genomic landscape of reproductive isolation. Here, we elucidate the genetic basis of ultraviolet (UV) iridescence, a courtship signal that differentiates the males of Colias eurytheme butterflies from a sister species, allowing females to avoid costly heterospecific matings. Anthropogenic range expansion of the two incipient species established a large zone of secondary contact across the eastern United States with strong signatures of genomic admixtures spanning all autosomes. In contrast, Z chromosomes are highly differentiated between the two species, supporting a disproportionate role of sex chromosomes in speciation known as the large-X (or large-Z) effect. Within this chromosome-wide reproductive barrier, linkage mapping indicates that cis- regulatory variation of bric a brac ( bab ) underlies the male UV-iridescence polymorphism between the two species. Bab is expressed in all non-UV scales, and butterflies of either species or sex acquire widespread ectopic iridescence following its CRISPR knockout, demonstrating that Bab functions as a suppressor of UV-scale differentiation that potentiates mating cue divergence. These results highlight how a genetic switch can regulate a premating signal and integrate with other reproductive barriers during intermediate phases of speciation. 

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