- 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)
- 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
- 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).
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.