The inheritance of female colour polymorphism inIschnura genei(Zygoptera: Coenagrionidae),with observations on melanism under laboratory conditions

Abstract

Current research on female colour polymorphism in Ischnura damselflies suggests that a balanced fitness trade-off between morphotypes contributes to the maintenance of polymorphism inside populations. The genetic inheritance system constitutes a key factor to understand morph fluctuation and fitness. Ischnura genei, an endemic species of some Mediterranean islands, has three female colour morphs, including one androchrome (male-coloured) and two gynochromes. In this study, we reared two generations of I. genei under laboratory conditions and tested male behavioural responses to female colour morphs in the field. We recorded ontogenetic colour changes and studied morph frequency in three populations from Sardinia (Italy). Morph frequencies of laboratory crosses can be explained by a model based on an autosomal locus with three alleles and sex-restricted expression, except for one crossing of 42 families with unexpected offspring. The allelic dominance relationship was androchrome > infuscans > aurantiaca. Old individuals reared in the laboratory exhibited different levels of melanism in variable extent depending on sex and morph. Results of model presentations indicate a male preference for gynochrome females and the lack of recognition of androchromes as potential mates. Aurantiaca females were the most frequent morph in the field (63–87%). Further studies in other populations and islands are needed to understand the maintenance of this polymorphism.

Ontogenetic colour change signals sexual maturity in a non‐territorial damselfly

“…Signalling sexual maturity through change in colour has been reported in many taxa including insects, amphibians, reptiles and birds (Bell & Zamudio, ; Chan, Stuart‐Fox, & Jessop, ; Corbet, ; Griggio, Devigili, Hoi, & Pilastro, ). Ischnura heterosticta , I. genei, I. elegans and I. senegalensis females change colour during ontogenesis; juvenile females carry fewer eggs and mate less frequently than adult females (Hinnekint, ; Huang & Reinhard, ; Sanmartín‐Villar & Cordero‐Rivera, ; Takahashi & Watanabe, ). In I. elegans , the males also change colour from green to blue, which correlates with spermatogenesis (Henze et al, ; Hinnekint, ).…”

“…In odonates, genetic and ontogenetic colour variation can occur in both sexes, or it can be limited to either males or females (Huang & Reinhard, ; Sanmartín‐Villar, Zhang, & Cordero‐Rivera, ; Willink, Duryea, Wheat, & Svensson, ). Genetically, determined female polychromatism occurs in sexually mature and immature in Ischnura senegalensis, I. elegans , and I. genei damselflies (Sanmartín‐Villar & Cordero‐Rivera, ; Takahashi & Watanabe, ; Willink et al, ). Likewise, sexually mature male dichromatism (conspicuous orange‐winged males and inconspicuous clear‐winged males) occurs in Mnais costalis damselflies (Tsubaki, ).…”

Temperature drives pre‐reproductive selection and shapes the biogeography of a female polymorphism

“…). The genetic basis of female colour polymorphism in I. elegans and its close relatives ( I. graellsii and I. genei ) has been revealed in controlled breeding experiments over several generations and arises from genetic variation at a single autosomal locus with three alleles in a dominance hierarchy and with sex‐limited expression to females (Cordero ; Sanchez‐Guillen et al ; Sanmartín‐Villar & Cordero‐Rivera ). In addition to fixed genetic colour differences among adult female colour morphs (Fig.…”

Ontogenic colour change, survival, and mating in the damselfly Agriocnemis pygmaea Rambur (Insecta: Odonata)

“…Colour variation may either represent allelic (heritable) polymorphism or phenotypic plasticity (‘functional polymorphism’, Fincke et al ., ). Allelic polymorphism arises from the expression of distinct autosomal alleles (Johnson, , ; Cordero‐Rivera, ; Andrés & Cordero, ; Sanmartín‐Villar & Cordero‐Rivera, ). On the other hand, many odonates exhibit ontogenic colour changes, whereby individual colour patterns change with age and developmental stage (Corbet, ; Fincke et al ., ; Huang, ).…”

“…On the other hand, many odonates exhibit ontogenic colour changes, whereby individual colour patterns change with age and developmental stage (Corbet, ; Fincke et al ., ; Huang, ). For instance, several species from the genus Ischnura exhibit a characteristic age‐related colour change from orange‐reddish to blue (Sirot et al ., ; Takahashi et al ., ; Sanmartín‐Villar & Cordero‐Rivera, ). Ontogenic colour change acts as a signal of female maturity in some damselflies (Takahashi & Watanabe, ; Huang & Reinhard, ; Takahashi et al ., ; Khan & Herberstein, ), suggesting that non‐receptive females benefit from ontogenic colour change by avoiding unnecessary mating attempts by males.…”