Morphological evolution through multiple cis-regulatory mutations at a single gene

Micro-scale macroevolution What are the genetics of species origin? The classic Darwinian 'micromutationist' view is that a new species differs from progenitors through an accumulation of small changes at many genes. But there are many examples that support the 'macromutationist' theory, where the key difference lies in large, abrupt changes, especially in genes involved in development. The answer, it seems, is a mixture of the two extremes. McGregor et al. took a close look at the shavenbaby gene, known to be responsible for differences in bristle pattern between fruit-fly species. They found that the interplay between three distinct gene enhancers is required to generate species-specific patterns of bristles. They conclude that genes of large effect that distinguish species may sometimes reflect the accumulation of multiple mutations of small effect at several genes. So the historical divide between the micromutationist and macromutationist camps may simply represent views of the same data observed at different scales.