The wing pattern of Moerarchis Durrant, 1914 (Lepidoptera: Tineidae) clarifies transitions between predictive models.

Sandra R Schachat

doi:10.1098/rsos.161002

Abstract

The evolution of wing pattern in Lepidoptera is a popular area of inquiry but few studies have examined microlepidoptera, with fewer still focusing on intraspecific variation. The tineid genus Moerarchis Durrant, 1914 includes two species with high intraspecific variation of wing pattern. A subset of the specimens examined here provide, to my knowledge, the first examples of wing patterns that follow both the ‘alternating wing-margin’ and ‘uniform wing-margin’ models in different regions along the costa. These models can also be evaluated along the dorsum of Moerarchis, where a similar transition between the two models can be seen. Fusion of veins is shown not to effect wing pattern, in agreement with previous inferences that the plesiomorphic location of wing veins constrains the development of colour pattern. The significant correlation between wing length and number of wing pattern elements in Moerarchis australasiella shows that wing size can act as a major determinant of wing pattern complexity. Lastly, some M. australasiella specimens have wing patterns that conform entirely to the ‘uniform wing-margin’ model and contain more than six bands, providing new empirical insight into the century-old question of how wing venation constrains wing patterns with seven or more bands.

Highlights

During recent decades, the longstanding scientific interest in the evolution of lepidopteran wing pattern has experienced a revival [1]
The results presented here provide insight into transitions between the ‘alternating’ and ‘uniform wingmargin’ models, the effect of vein fusion on wing pattern, the relationship between pattern and venation along the dorsum, the importance of wing size, and the number of bands along the wing
In all female M. australasiella examined here, and in two of the five male specimens, wing pattern always appears to follow the ‘uniform wing-margin’ model from Sc to Rs2: each vein is surrounded by dark scales, and light pattern elements reach the costa between each pair of adjacent veins

Summary

Introduction

The longstanding scientific interest in the evolution of lepidopteran wing pattern has experienced a revival [1]. A decade later, in 1935, the first predictive model for wing pattern in microlepidoptera was proposed [9] This model, called the ‘vein-fork’ model, predicts that the basal edge of each dark band lies along the points where veins bifurcate; recent studies have found no support for this model [10,11]. A second predictive model for microlepidopteran wing patterns—previously known as ‘wing-margin’ model, and called the ‘alternating wing-margin’ model here—was proposed much more recently [12,13]. According to this model, dark and light bands straddle/abut alternating veins along the costal margin of the forewing (figure 1a); two recent studies strongly support this model [10,11]

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Conclusion