Melanic individuals in color polymorphicEnallagmadamselflies result from phenotypic, not genetic, variation

Abstract

This paper is dedicated to Georg Ruppëll, in honor of his 75th birthday and with great appreciation for his dedication to capturing the stunning beauty of odonates on film.Genetically determined color polymorphisms have a long history in the study of evolutionary change acting on populations. The Odonata exhibit relatively high levels of sex-specific color polymorphisms in mature adults. In Ischnura and Coenagrion, female-specific polymorphisms are known to be controlled by Mendelian genes. Nearly half of Enallagma species have polymorphic females, but the inheritance of any has yet to be determined. Our aims here were to determine: (1) the inheritance of the color polymorphism in E. hageni; and (2) inherent reproductive characteristics of blue female andromorphs and green heteromorphs reared under controlled conditions as tenerals. Maternal morphs, which developed normal coloration in field enclosures within a week, did not differ in copulation time or clutch size, and their offspring did not differ in sex ratio or survivorship to emergence. Surprisingly, no laboratory-reared offspring developed normal mature coloration. Rather, the initially pale parts of the thorax and abdomen, that normally would turn either blue or green, became melanized. Black novel phenotypes also developed in adults of E. civile, E. anna, E. carunculatum, and E. annexum that as larvae or teneral adults were reared to sexual maturity under greenhouse conditions that differed from the laboratory conditions used to rear E. hageni. We hypothesize that the phenotypic plasticity in body coloration documented in Enallagma results from the quality of UV radiation experienced as a sexually immature adult, which is known to affect melanization in other insects. These examples in Enallagma offer insights into the origin of color novelty in Odonata.

Peer Review #1 of "The inheritance of female colour polymorphism in Ischnura genei (Zygoptera: Coenagrionidae), with observations on melanism under laboratory conditions (v0.1)"

“…S1), which complicated morph assignment. Melanism was previously found in other captive-reared damselflies in our laboratory, notably in Coenagrion scitulum (Cordero, Santolamazza-carbone & Utzeri, 1995) (Barnard et al, 2015). In our case, the only difference between I. genei and the other species was the food supply.…”

Peer Review #2 of "The inheritance of female colour polymorphism in Ischnura genei (Zygoptera: Coenagrionidae), with observations on melanism under laboratory conditions (v0.1)"

“…We did not find differences in fecundity between female morphs as in previous studies on other species (Bots et al, 2010;as Barnard et al, 2015;Galicia-Mendoza, 2015 between others).…”

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

“…obs., 2009). Similar melanic colouration in several Enallagma species was assumed as an effect of the incomplete UV radiation that larvae and tenerals received under captive conditions ( Barnard et al, 2015 ). In our case, the only difference between I. genei and the other species was the food supply.…”

“…We fed I. genei only with Artemia nauplii during the whole larval period, while in the other cases last instar larvae received a supplement of Tubifex worms or adult Artemia (which has different nutrient composition). However, Barnard et al (2015) suggest that the nutritional supply cannot produce melanism. In our case, melanism only appeared in old individuals while in the other cited cases the first adult colouration was affected by melanism.…”