Sexual Dimorphism and Allometric Effects Associated With the Wing Shape of Seven Moth Species of Sphingidae (Lepidoptera: Bombycoidea)

Abstract

Sexual dimorphism is a pronounced pattern of intraspecific variation in Lepidoptera. However, moths of the family Sphingidae (Lepidoptera: Bombycoidea) are considered exceptions to this rule. We used geometric morphometric techniques to detect shape and size sexual dimorphism in the fore and hindwings of seven hawkmoth species. The shape variables produced were then subjected to a discriminant analysis. The allometric effects were measured with a simple regression between the canonical variables and the centroid size. We also used the normalized residuals to assess the nonallometric component of shape variation with a t-test. The deformations in wing shape between sexes per species were assessed with a regression between the nonreduced shape variables and the residuals. We found sexual dimorphism in both wings in all analyzed species, and that the allometric effects were responsible for much of the wing shape variation between the sexes. However, when we removed the size effects, we observed shape sexual dimorphism. It is very common for females to be larger than males in Lepidoptera, so it is expected that the shape of structures such as wings suffers deformations in order to preserve their function. However, sources of variation other than allometry could be a reflection of different reproductive flight behavior (long flights in search for sexual mates in males, and flight in search for host plants in females).

Identification, sexual dimorphism, and allometric effects of three psyllid species of the genus Psyllopsis by geometric morphometric analysis (Hemiptera, Liviidae)

“…: Pyralidae) (Zahiri, 2003), Chironomus imicola Kieffer, 1913 (Dip. : Chironomidae) (McLechlan, 1986), seven moth species of Sphingidae (de Camargo et al 2015), and Ectomyelois ceratoniae (Zeller, 1839) (Lepidoptera: Pyralidae) (Mozaffarian et al 2007b). …”

“…McLechlan (1986) believes that the sexual dimorphism observed in insects is due to different roles of adult males and females, and Dale et al (2007) categorizes the reasons into three main groups, including: evolutionary constraints, natural selection, and sexual selection. Forewings of females have larger surfaces with rounder apical edge, which are suitable for flight with greater maneuverability (de Camargo et al 2015). Triangular wingtip (or longer wingtip) in insects can increase energy efficiency during the migratory flight (Lockwood et al 1998).…”

“…Sexual dimorphism in size also has not been ever recorded in the ash psyllids. The presence of larger wing size of females may be due to larger body size of the females and affected by the different reproductive role in the males and females (Fairbairn 1997) commonly observed in different insect groups (de Camargo et al 2015, Fox et al 2003, Harrison and Cooper 2003; Kraushaar and Blanckenhorn 2002, Mozaffarian et al 2007, Outomuro and Johansson 2011). …”

“…These variations have been specially shown in body size and color and also wing size and color (Hodkinson 2009, Brown and Hodkinson 1988, Conci and Tamanini 1983). Sexual dimorphism may arise as size and shape dimorphism or by allometry (i.e., correlation of shape and size) (de Camargo et al 2015). …”

Sexual dimorphism in the alpine butterflies Boloria pales and Boloria napaea: differences in movement and foraging behavior (Lepidoptera: Nymphalidae)

“…Examples of differences in life histories of sexes are protandry and protogeny, when the emergence of male and female individuals of a single species is time‐shifted (examples of protandry: Munguira et al ., ; Mousson et al ., ; Hula et al ., ; Wang et al ., ; Junker & Schmitt, ; protogeny: Larsen et al ., ; Degen et al ., ). Variations in morphology between sexes are found, for example, in the shape and size of the wings (De Camargo et al ., ; Francini et al ., ), or other body parts like the eyes or the antennae (Wall, ; Ziemba & Rutowski, ; Lau et al ., ), but also in body‐size with females normally being bigger than males (Stillwell et al ., ). More difficult to investigate is sexual dimorphism in the behavior of butterflies.…”