Habitat divergence shapes the morphological diversity of larval insects: insights from scorpionflies

Abstract

Insects are the most diverse group of organisms in the world, but how this diversity was achieved is still a disputable and unsatisfactorily resolved issue. In this paper, we investigated the correlations of habitat preferences and morphological traits in larval Panorpidae in the phylogenetic context to unravel the driving forces underlying the evolution of morphological traits. The results show that most anatomical features are shared by monophyletic groups and are synapomorphies. However, the phenotypes of body colorations are shared by paraphyletic assemblages, implying that they are adaptive characters. The larvae of Dicerapanorpa and Cerapanorpa are epedaphic and are darkish dorsally as camouflage, and possess well-developed locomotory appendages as adaptations likely to avoid potential predators. On the contrary, the larvae of Neopanorpa are euedaphic and are pale on their trunks, with shallow furrows, reduced antennae, shortened setae, flattened compound eyes on the head capsules, and short dorsal processes on the trunk. All these characters appear to be adaptations for the larvae to inhabit the soil. We suggest that habitat divergence has driven the morphological diversity between the epedaphic and euedaphic larvae, and may be partly responsible for the divergence of major clades within the Panorpidae.

Morphological phylogeny of Panorpidae (Mecoptera: Panorpoidea)

“…11A–S); in females: 9) medigynium usually with poorly developed main plate, and a pair of long twisted posterior arms (Fig. 13E–J); and in larvae (only known for Neopanorpa ): 10) head capsule with shallow furrows, reduced antennae, shortened setae and flattened compound eyes, and trunk with short dorsal processes (Jiang et al ., 2019b).…”

“…10C–E); in females, 9) medigynium usually with a well‐developed main plate, and a pair of short tapering posterior arms (Fig. 13K–Z); and in larvae (known for all genera except † Baltipanorpa ): 10) head capsule lacking shallow furrows, with well‐developed antennae, setae, and compound eyes, and trunk with long dorsal processes (Chen & Hua, 2011; Wang & Hua, 2019a; Jiang et al ., 2019b).…”

“…According to recent molecular studies (Hu et al ., 2015; Miao et al ., 2019), the Panorpidae can be categorized into two major clades: one consisting of Leptopanorpa and Neopanorpa , and the other comprising the other extant genera. A great divergence between these two clades is also supported by the morphology of the egg chorion (Ma et al ., 2009), the chromosome number (Miao et al ., 2019) and the morphology and biology of the larvae (Jiang et al ., 2019b). Therefore, taxonomic revisions at the generic levels are desperately needed to provide a clear diagnosis for each clade of Panorpidae, and resolve the paraphyly of Panorpa and Neopanorpa .…”

Review of the scorpionfly genus Dicerapanorpa Zhong & Hua (Mecoptera: Panorpidae), with descriptions of two new species

“…The male adult initiates copulation by grasping the female with a notal organ on the posterior margin of the third abdominal tergum and two anal horns on the posterior margin of the sixth tergum, and prolongs copulation by offering salivary masses as nuptial gifts (Zhong et al 2015). The larvae of Dicerapanorpa are eruciform with annulated processes, reflecting the adaptive significance for fossorial and soil-living habits (Ma et al 2014;Jiang et al 2019).…”

Two new species of Cerapanorpa (Mecoptera, Panorpidae) from the Qinling and Minshan mountains

“…The eggs are oval and bear polygonal net-like ridges on the chorion surface ( Li et al 2007 ; Ma et al 2009 ). The saprophagous larvae are eruciform and epedaphic, bearing eight pairs of abdominal prolegs, and usually overwinter as grown larvae in soil cavities ( Jiang and Hua 2015 ; Jiang et al 2019 ). The larvae possess a pair of compound eyes consisting of ⁓30 ommatidia ( Chen et al 2012 ), which almost have the same cellular components as those of their adults although the tiering scheme is different ( Chen and Hua 2016 ).…”