Divergence in Potential Contact Pheromones and Genital Morphology Among Sympatric Song Types of the Bush Cricket Mecopoda elongata

Abstract

A well-established route to speciation in animals is via the evolution of divergent male mating signals and female preferences within a species. However, an open question is how common it is for near complete isolation to be achieved through a single signal-receiver system as opposed to multiple aspects of the mate-recognition system diverging simultaneously. The five highly divergent mate-attraction song types of the bush cricket Mecopoda elongata exemplify reproductive isolation in sympatry through long-distance mating signals. Female preference for their own song type has been established as a strong pre-mating reproductive barrier, but the potential existence of additional isolating mechanisms has not been investigated. We quantify divergence in cuticular lipid profiles and external genital structures between song types. These traits show significant variation among species of Orthoptera and are known to be used in mate recognition following contact. We show that divergence among sympatric Mecopoda song types in both cuticular lipid profiles and two external genital structures is sufficiently extensive that either of them can be used to identify individual song type with 90% accuracy. Our findings suggest that multiple isolating mechanisms are likely to evolve simultaneously facilitating a more robust reproductive isolation. Our study indicates a role for sexual selection in the divergence and potential future speciation of these populations and suggests that reproductive isolation may frequently evolve through simultaneous divergence across different aspects of mate recognition systems.

Vocal divergence is concordant with genomic evidence for strong reproductive isolation in grasshopper mice (Onychomys)

“…Whereas speciation research has traditionally focused on single types of isolating mechanisms in a given system (e.g., genetic incompatibilities or ecological isolation; Coyne & Orr, ), recent work in invertebrates emphasizes the importance of multiple isolating mechanisms acting in concert (Dutta, Balakrishnan, & Tregenza, ; Gilman, Fowler‐Finn, & Hebets, ; Moran, Hunt, Mitchell, Ritchie, & Bailey, ). Here, we show that, contrary to prior suggestions (Sullivan et al, ), hybridization between O. arenicola and O. torridus either does not occur or is so rare that it is below the detection limits of our sample sizes.…”

Calling songs of Neotropical katydids (Orthoptera: Tettigoniidae) from Panama

“…The role of visual cues or chemical cues in mating is unknown for the species described here and is understudied in katydids in general. Chemical cues appear to play a role in mate recognition in the Mecopoda elongata species complex in India (Dutta et al 2018), suggesting that they might also play a role in mate recognition in Neotropical species with similar acoustic or visual cues. Studies on katydid acoustic signals have revealed the presence of cryptic species that are morphologically very similar but can be distinguished by acoustic signals (Walker 1964, Walker et al 2003, Montealegre-Z et al 2011 and also cases of morphologically distinct species that have extremely similar acoustic signals (Çiplak et al 2009(Çiplak et al , Şirin et al 2014(Çiplak et al , Grzywacz et al 2017, emphasizing the importance of documenting acoustic signals for taxonomic and phylogenetic studies.…”

Acoustic signalling in Orthoptera

“…Berger and Gottsberger, 2010;Ostrowski et al, 2009;Vedenina et al, 2020). Additional signalling modalities have been identified in courtship, for example vibration in the crickets Adelosgryllus rubricephalus (Zefa et al, 2008), Cranistus colliurides (Centeno and Zefa, 2019) and Ornebius aperta (Andrade and Mason, 2000), chemical cues in the grasshoppers Chorthippus biguttulus and C. mollis (Finck and Ronacher, 2017), and probably chemical and tactile cues in the bush-cricket Mecopoda elongata (Dutta et al, 2018). In bush-crickets visual cues can be important during phonotaxis.…”