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

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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.

No MeSH data available.


The two versions of the ‘wing-margin’ model, plotted onto the most recent reconstruction of ancestral wing venation for Lepidoptera [14]. The boundary between the costa and dorsum is ambiguous here; the Rs4 vein is treated as belonging to the costa because of the developmental constraints that it exerts in the Micropterigidae [10,11]. Either series of pattern elements—those illustrated in blue, or those illustrated in red—could develop a dark colour. The bands are not shown to reach the dorsum here, despite the fact that wing pattern does extend to the dorsum, because the ancestral relationship between the costa and dorsum is not yet known for banded wing patterns. (a) The original version of the model, called the ‘alternating wing-margin’ model here. (b) A hypothesized intermediate stage, based on observations of Sabatinca demissa [11]. (c) The ‘uniform wing-margin’ model.
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RSOS161002F1: The two versions of the ‘wing-margin’ model, plotted onto the most recent reconstruction of ancestral wing venation for Lepidoptera [14]. The boundary between the costa and dorsum is ambiguous here; the Rs4 vein is treated as belonging to the costa because of the developmental constraints that it exerts in the Micropterigidae [10,11]. Either series of pattern elements—those illustrated in blue, or those illustrated in red—could develop a dark colour. The bands are not shown to reach the dorsum here, despite the fact that wing pattern does extend to the dorsum, because the ancestral relationship between the costa and dorsum is not yet known for banded wing patterns. (a) The original version of the model, called the ‘alternating wing-margin’ model here. (b) A hypothesized intermediate stage, based on observations of Sabatinca demissa [11]. (c) The ‘uniform wing-margin’ model.

Mentions: One century ago, two studies examined the relationship between wing pattern and wing venation in individual genera and families of microlepidoptera, but did not propose any predictive models that could be tested explicitly in the context of ordinal-level homologies [5,6]. The nymphalid ground plan, a model for wing pattern in butterflies, was proposed soon thereafter, in the 1920s [7,8]. A decade later, in 1935, the first predictive model for wing pattern in microlepidoptera was proposed [9]. This model, now 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 simply 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].Figure 1.


The wing pattern of Moerarchis Durrant, 1914 (Lepidoptera: Tineidae) clarifies transitions between predictive models
The two versions of the ‘wing-margin’ model, plotted onto the most recent reconstruction of ancestral wing venation for Lepidoptera [14]. The boundary between the costa and dorsum is ambiguous here; the Rs4 vein is treated as belonging to the costa because of the developmental constraints that it exerts in the Micropterigidae [10,11]. Either series of pattern elements—those illustrated in blue, or those illustrated in red—could develop a dark colour. The bands are not shown to reach the dorsum here, despite the fact that wing pattern does extend to the dorsum, because the ancestral relationship between the costa and dorsum is not yet known for banded wing patterns. (a) The original version of the model, called the ‘alternating wing-margin’ model here. (b) A hypothesized intermediate stage, based on observations of Sabatinca demissa [11]. (c) The ‘uniform wing-margin’ model.
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Related In: Results  -  Collection

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RSOS161002F1: The two versions of the ‘wing-margin’ model, plotted onto the most recent reconstruction of ancestral wing venation for Lepidoptera [14]. The boundary between the costa and dorsum is ambiguous here; the Rs4 vein is treated as belonging to the costa because of the developmental constraints that it exerts in the Micropterigidae [10,11]. Either series of pattern elements—those illustrated in blue, or those illustrated in red—could develop a dark colour. The bands are not shown to reach the dorsum here, despite the fact that wing pattern does extend to the dorsum, because the ancestral relationship between the costa and dorsum is not yet known for banded wing patterns. (a) The original version of the model, called the ‘alternating wing-margin’ model here. (b) A hypothesized intermediate stage, based on observations of Sabatinca demissa [11]. (c) The ‘uniform wing-margin’ model.
Mentions: One century ago, two studies examined the relationship between wing pattern and wing venation in individual genera and families of microlepidoptera, but did not propose any predictive models that could be tested explicitly in the context of ordinal-level homologies [5,6]. The nymphalid ground plan, a model for wing pattern in butterflies, was proposed soon thereafter, in the 1920s [7,8]. A decade later, in 1935, the first predictive model for wing pattern in microlepidoptera was proposed [9]. This model, now 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 simply 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].Figure 1.

View Article: PubMed Central - PubMed

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.

No MeSH data available.