Static allometry in two species of neotropical stalk‐eyed fly

Abstract

The eye stalk is a sexually selected trait that has evolved several times within true flies (Diptera). It has been suggested that selection on secondary sexual traits such as the eye stalk favors positive allometry (disproportionate increase in a trait in relation to body size), but it remains unclear how common positive allometry is in such traits compared with nonsexual traits. Although the morphological evolution of eye stalks has been extensively investigated in diopsids, little is known about the evolution of eye stalks in other dipteran families. Our study aimed to assess the allometric relationships of sexual and nonsexual traits in two species of the Neotropical ulidiid genus Plagiocephalus. We estimated the covariance between body size and eye stalks, and between body size and four other nonsexual morphological traits, in males and females of P. latifrons and P. lobularis. We found a significant positive scaling relationship between eye stalk length and body size in both species, representing the steepest allometric exponents ever observed in stalk‐eyed flies. However, our results also show evidence that positive allometry is not exclusive for exaggerated traits. Our findings also lend support to the hypothesis that the allometric intercept is subject to more variation during evolution than the allometric slope.

New integrated evidences reveal male polymorphism and species delimitation in stalk‐eyed fruit flies

“…Moreover, non-social insects like dragonflies, damselflies, spade beetles, water striders, and aphids have also been reported to exhibit male polymorphism (Futahashi, 2016;Matsumoto & Knell, 2017;Nomakuchi, 1992;Sun et al, 2018;Ziabari et al, 2023). Male polymorphism has also been found in Diptera, for example, Sciaridae (Steffan, 1973), Ulidiidae (Oliveira Vasconcelos et al, 2019), and Diopsidae (Baker et al, 2012). However, the discovery of male polymorphism in natural populations of stalk-eyed fruit flies still holds special scientific significance.…”

Size and shape in the evolution of the worker head in Pheidole ants (Hymenoptera: Formicidae)

“…The evolutionary origin of exaggerated morphological structures provides a window into the versatility and limits of developmental programs (Emlen, 2001; Emlen & Nijhout, 2000; Shingleton & Frankino, 2013). Examples of exaggerated structures are found in many animal lineages (e.g., Gould, 1974) but seem to be particularly common in insects, such as stalk‐eyed flies (Vasconcelos et al., 2019), lucanid beetles (Romiti et al., 2015), and several ant lineages (e.g., Blanchard et al., 2020; Boudinot et al., 2021; Sarnat et al., 2017). Although exaggerated traits are most likely to be associated with males and be under sexual selection (e.g., weapons used for fights and/or display; see Emlen, 2008 for further discussion), several cases of such morphologies are present in females (e.g., Matsuura, 2006), as well as not being sexually selected (e.g., Bro‐Jørgensen, 2007).…”

Phylogenetic relationships of picture‐winged flies of the tribe Pterocallini (Diptera: Ulidiidae) inferred from a morphological analysis

“…One of the most conspicuous forms of sexual dimorphism in animals is displayed by species of Pterocallini: the stalked eyes of males of Plagiocephalus Wiedemann, 1830 (Vasconcelos et al 2019a). Among Diptera, only eight groups are known to have evolved independently this type of ornamental trait (Buschbeck et al 2001).…”

“…Wilkinson & Reillo 1994;David et al 2000). Compared to Diopsidae species, Plagiocephalus males have relative larger eye stalks (Vasconcelos et al 2019a). Pterocallini species also featured other interesting forms of sexual dimorphism.…”