Evolution of wing polymorphism and genital asymmetry in the thread‐legged bugs of the tribe Metapterini Stål (Hemiptera, Reduviidae, Emesinae) based on morphological characters

Abstract

Wing polymorphism and asymmetric male genitalia are intriguing morphological phenomena occurring in insects. Among Emesinae, or thread‐legged bugs, the tribe Metapterini Stål exhibits these two interesting morphological attributes. Nonetheless, evolutionary interpretations of these phenomena cannot be put forward because phylogenetic hypotheses for Emesinae are lacking. Thread‐legged bugs are easily recognized among assassin bugs due to their elongated and seemingly delicate body. The tribe Metapterini has 28 genera and approximately 280 described species. The only available phylogenetic hypothesis among Emesinae tribes was proposed by Wygodzinsky (1966), and it hypothesized Deliastini Villiers as the sister group of Metapterini, although this hypothesis has never been tested with cladistic approaches. Recent analyses using character sets of genitalia and prolegs suggest that Metapterini might not be monophyletic. In order to test these ideas, we compiled a morphological dataset of 138 characters that includes external morphological characters, detailed features of prolegs and genitalia of both sexes for Metapterini, which were analysed cladistically including 55 terminals, comprising 24 genera (85.7% of the generic diversity), 43 species of Metapterini and 12 outgroups. Metapterini was recovered as paraphyletic by the inclusion of Bergemesa Wygodzinsky, Palacus Dohrn and Stalemesa Wygodzinsky, all currently assigned to Deliastini. Gardena Dohrn (Emesini) was recovered as the sister group of Metapterini + Deliastini as suggested by Wygodzinsky (1966). Based on these results, we synonymize Deliastini syn. n. with Metapterini sensu n. and propose two new genera: Bacata Castro‐Huertas & Forero gen. n., for three Andean species previously placed in Liaghinella Wygodzinsky, and Valkyriella Castro‐Huertas & Forero gen. n. for Ghilianella borgmeieri Wygodzinsky. Ancestral state reconstruction of wing polymorphism indicates that males and females were fully winged in the ancestor of Metapterini sensu n. with two independent evolutionary transitions to the apterous and brachypterous conditions. The analysis of the symmetry of the male genitalia shows an ancestor with symmetric male genitalia and two independent emergences of asymmetrical male genitalia in Metapterini.

Genetic assimilation and the evolution of direction of genital asymmetry in anablepid fishes

“…Genital asymmetry appears to be evolutionarily labile (like other morphological characteristics of animal genitalia) [18], with multiple transitions from symmetry to asymmetry across lineages [51][52][53][54]. In anablepid fishes, the transition from symmetry to asymmetry appears to have occurred twice: once in males after the evolution of the male gonopodium and again in females of the genus Anableps.…”

Outside the pattern: Evolution of the genital asymmetry in Saicinae (Hemiptera: Heteroptera: Reduviidae)

“…The genitalia is one of the most important and useful species‐diagnostic characters in insect systematics (Song & Bucheli, 2010), is one of the most important criteria to take taxonomic decisions, and it is particularly useful in Heteroptera species delimitations. In Reduviidae, there are still scattered studies documenting in detail the male and female genitalia, and even less employing such character system in phylogenetic analyses (Castro‐Huertas et al, 2018, 2021; Forero & Weirauch, 2012; Weirauch, 2008). Despite this, the genitalia offer ideal characters for phylogenetic analyses, providing information for resolving relationships at different taxonomic levels.…”

“…The weak point of these analyses is the poorly sample used for the Saicinae (Hwang & Weirauch, 2012; Weirauch, 2008; Weirauch & Munro, 2009). In addition, recent studies within the allied subfamily Emesinae showed that the genital characters could offer information to elucidate the relationships and limits to tribal, generic, and specific levels (Castro‐Huertas et al, 2018, 2021).…”

Asymmetry of the male internal reproductive organs in Mantophasmatodea

“…Various hypotheses about the evolution of genital asymmetries have been suggested, for example, ecological constraints, internal space constraints that favour asymmetric morphology of internal organs which secondarily affect genitalia, sexual selection via antagonistic coevolution, and sexual selection favouring asymmetry as a mechanical compensation for behavioural changes of the mating position [ 6 , 7 ]. While external copulatory organs in insects have often been subject to investigations concerning asymmetries and the evolution thereof [ 8 – 11 ], internal reproductive structures have received far less attention. Usually, insect male internal reproductive organs consist of paired (and bilaterally symmetric) mesodermal testes, a pair of lateral ducts, the vasa deferentia, which each contain an enlarged region to serve as a sperm reservoir (vesiculum seminalis), and a median ectodermal ductus ejaculatorius.…”