Wing patterning in moths and butterflies

Introduction

• Butterfly wings are comprised of a series of “scales” each composed from a single cell (Ghiradella 1989).
• How these scales are patterned is dependent upon a variety of genes contained in a highly-conserved set of genes that have evolved somewhat independently (Martin and Reed 2010).
• Each pattern element has some developmental modularity. Wings are highly compartmentalized (Martin and Reed 2010).
• Autonomy of patterning lessens constraint in each part’s evolutionary trajectories
• Nymphalid ground plan consists of several major plan elements (Martin and Reed 2010):
  • Basalis (B)
  • Discalis II (DII)
  • Discalis I (DI)
  • MII
  • MI
  • Border ocelli (Oc)
  • Externae patterns (E)
    • Parafocal (EIII)
    • Submarginal (EII)
    • Marginal (EI)
    • Venosa (V)
    • Intervenosa (I)

Figure 1: Schematic showing location and conservation of major wing plan elements Phylogenetic spread of each ground plan pattern element across Lepidoptera. : encountered in the clade; : not encountered in the clade (Martin and Reed 2010).

• Martin and Reed (2010) presents a broad comparative analysis of the development and evolution of discal spot (DI) and basal symmetry system (DII) patterns across Lepidoptera.

 

Methods (Martin and Reed 2010)

• Review of existing literature
• Online collections of photographs analyzed to find distribution of DI and DII
• Phylogenetic Reconstruction
• Molecular cloning and probe synthesis
• Immunohistofluorescence and in situ hybridization

Results (Martin and Reed 2010)

• DI elements are widespread, while DII is scattered (Figure 2)

Figure 2: Shows phylogenetic distribution of DI and DII (Martin and Reed 2010)

• Wingless marks the development of major ground plan elements in larval wing disks (Figure 3)

Figure 3 (Martin and Reed 2010)

• Aristaless1 is duplicated in Lepidoptera (Figure 4)
• Accelerated rate of evlotion in aristaless1 after duplication (Figure 4)
• Aristaless1 and aristaless2: cis-regulatory divergence after duplication (Figure 4)

Figure 4: shows duplication of aristaless1 (Martin and Reed 2010)

Conclusions (Martin and Reed 2010)

• Highly conserved ground plan of pattern homologies
• Modification of only a handful of serially repeated elements
• Wingless (wg)
  • Early determination of major basal, discal, and marginal stripe patterns in Lepidoptera
  • Homology across moths and butterflies
• Aristaless2
  • Lepidoptera-specific homeobox gene
  • Preceded wingless expression in early determination of discal II stripe patterns
  • Derived from tandem duplication of aristaless gene
  • More conserved paralog = aristaless1

Figure 5: Model for the evolution of DI and DII pattern elements. (A) Summary of forewing wgand DP311-antigen/alexpression in the species sampled in this study (Martin and Reed 2010).

References:

Ghiradella, H. (1989). “Structure and development of iridescent butterfly scales: Lattices and laminae.” Journal of Morphology 202(1): 69-88.

Martin, A. and R. D. Reed (2010). “wingless and aristaless2 Define a Developmental Ground Plan for Moth and Butterfly Wing Pattern Evolution.” Molecular Biology and Evolution 27(12): 2864-2878.