Abstract
This study examines the evolution hindwing shape in Chinese dung beetle species using morphometric and phylogenetic analyses. Previous studies have analyzed the evolution of wing shape within a single or very few species, or by comparing only a few wing traits. No study has analyzed wing shape evolution of a large number of species, or quantitatively compared morphological variation of wings with proposed phylogenetic relationships. This study examines the morphological variation of hindwings based on 19 landmarks, 119 morphological characters, and 81 beetle species. Only one most parsimonious tree (MPT) was found based on 119 wing and body characters. To better understand the possible role of the hindwing in the evolution of Scarabaeinae, additional phylogenetic analyses were proposed based on the only body features (106 characters, wing characters excluded). Two MPT were found based on 106 body characters, and five nodes were collapsed in a strict consensus. There was a strong correlation between the morphometric tree and all phylogenetic trees (r>0.5). Reconstructions of the ancestral wing forms suggest that Scarabaeinae hindwing morphology has not changed substantially over time, but the morphological changes that do occur are focused at the base of the wing. These results suggest that flight has been important since the origin of Scarabaeinae, and that variation in hindwing morphology has been limited by functional constraints. Comparison of metric disparity values and relative evolutionary sequences among Scarabaeinae tribes suggest that the primitive dung beetles had relatively diverse hindwing morphologies, while advanced dung beetles have relatively similar wing morphologies. The strong correlation between the morphometric tree and phylogenetic trees suggest that hindwing features reflect the evolution of whole body morphology and that wing characters are suitable for the phylogenetic analyses. By integrating morphometric and cladistic approaches, this paper sheds new light on the evolution of dung beetle hind wings.
Highlights
The evolution of flight has led to a wide variety of morphological adaptations in such flying animals as birds, bats, and insects
Previous studies have considered the evolution of wing shape by analyzing a single or very few species [18,19,20,21,22], or by comparing only a few wing traits [23,24] using a traditional comparative morphology approach
This study examines the morphological variation of beetle hind wings based on 81 beetle species (Table s1), 19 wing landmarks (Figure 1A–B), and 119 wing and body morphological characters (Table S2, S3, Figures S1, S2, S3, S4, S5, S6, S7, S8), which were selected from Philips et al [25] and coded for the Chinese dung beetles for the first time
Summary
The evolution of flight has led to a wide variety of morphological adaptations in such flying animals as birds, bats, and insects. Studying the evolution of flight characters is important to understanding the different selective external forces that have shaped the size and shape of wings and other flight traits, and how these adaptations may be limited by developmental or phylogenetic constraints [1,2]. Several studies have demonstrated that wing shape in birds is affected by migration distance [3,4,5], sexual selection [6,7], and foraging strategies [3,8], and that flight characters, such as tail shape, can be limited by mechanical and physiological constraints [9]. As well, wing shape is likely to be affected by different selective external forces [10,11], but the dominant drivers of wing shape evolution are generally unknown. If wing characters are suitable for the phylogenetic analyses and how wing characters have evolved over time are largely unexplored
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