Swain Timothy D, Taylor Derek J
Department of Biological Sciences, Florida State University, Tallahassee, FL 32306, USA.
Proc Biol Sci. 2003 May 7;270(1518):887-96. doi: 10.1098/rspb.2002.2297.
The evolutionary success of arthropods has been attributed partly to the diversity of their limb morphologies. Large morphological diversity and increased specialization are observed in water flea (Cladocera) limbs, but it is unclear whether the increased limb specialization in different cladoceran orders is the result of shared ancestry or parallel evolution. We inferred a robust among-order cladoceran phylogeny using small-subunit and large-subunit rRNA nuclear gene sequences, signature sequence regions, novel stem-loops and secondary structure morphometrics to assess the phylogenetic distribution of limb specialization. The sequence-based and structural rRNA morphometric phylogenies were congruent and suggested monophyly of orders with raptorial limbs, but paraphyly of orders with reduced numbers of specialized limbs. These results highlight the utility of complex molecular structural characters in resolving ancient rapid radiations.
节肢动物在进化上的成功部分归因于其肢体形态的多样性。在水蚤（枝角类）的肢体中观察到了巨大的形态多样性和日益增加的特化现象，但尚不清楚不同枝角类目中肢体特化的增加是共同祖先的结果还是平行进化的结果。我们利用小亚基和大亚基rRNA核基因序列、特征序列区域、新型茎环和二级结构形态测量学推断了一个稳健的枝角类目间系统发育树，以评估肢体特化的系统发育分布。基于序列和结构rRNA形态测量的系统发育树是一致的，表明具有捕食性肢体的目是单系的，但具有较少特化肢体的目是并系的。这些结果凸显了复杂分子结构特征在解析古代快速辐射中的作用。
