Tanaka Kohtaro, Barmina Olga, Kopp Artyom
Department of Evolution and Ecology, University of California-Davis, One Shields Ave., Davis, CA 95616, USA.
Proc Natl Acad Sci U S A. 2009 Mar 24;106(12):4764-9. doi: 10.1073/pnas.0807875106. Epub 2009 Mar 2.
Similar selective pressures can lead to independent origin of similar morphological structures in multiple evolutionary lineages. Developmental mechanisms underlying convergent evolution remain poorly understood. In this report, we show that similar sex comb morphology in closely related Drosophila species is produced by different cellular mechanisms. The sex comb is a recently evolved, male-specific array of modified bristles derived from transverse bristle rows found on the first thoracic legs in both sexes. "Longitudinal" sex combs oriented along the proximo-distal leg axis evolved independently in several Drosophila lineages. We show that in some of these lineages, sex combs originate as one or several transverse bristle rows that subsequently rotate 90 degrees and align to form a single longitudinal row. In other species, bristle cells that make up the sex combs arise in their final longitudinal orientation. Thus, sex combs can develop through either sex-specific patterning of bristle precursor cells or male-specific morphogenesis of sexually monomorphic precursors. Surprisingly, the two mechanisms produce nearly identical morphology in some species. Phylogenetic analysis shows that each of these mechanisms has probably evolved repeatedly in different Drosophila lineages, suggesting that selection can recruit different cellular processes to produce similar functional solutions.
相似的选择压力可导致多个进化谱系中相似形态结构的独立起源。趋同进化背后的发育机制仍知之甚少。在本报告中，我们表明，亲缘关系相近的果蝇物种中相似的性梳形态是由不同的细胞机制产生的。性梳是一种最近进化而来的、雄性特有的经过修饰的刚毛阵列，源自两性第一胸腿上的横向刚毛排。沿腿的近端到远端轴排列的“纵向”性梳在几个果蝇谱系中独立进化。我们表明，在其中一些谱系中，性梳起源于一排或几排横向刚毛，这些刚毛随后旋转90度并排列形成单一的纵向排。在其他物种中，构成性梳的刚毛细胞以其最终的纵向方向产生。因此，性梳可以通过刚毛前体细胞的性别特异性模式形成或两性同形前体的雄性特异性形态发生来发育。令人惊讶的是，这两种机制在某些物种中产生了几乎相同的形态。系统发育分析表明，这些机制中的每一种可能在不同的果蝇谱系中反复进化，这表明选择可以利用不同的细胞过程来产生相似的功能解决方案。
