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. Graphic: encountered in the clade; Graphic: 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.

Butterfly Wing Scales (asknature.org)

 

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.

 

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