Medina M, Walsh P J
Division of Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, Florida 33149, USA.
Mol Phylogenet Evol. 2000 Apr;15(1):41-58. doi: 10.1006/mpev.1999.0736.
Fragments from three mitochondrial genes (12S, 16S, and COI) were sequenced to reconstruct a molecular phylogeny of the opisthobranch order Anaspidea. The molecular phylogeny supports the placement of the genus Akera, a taxon previously regarded by some authors as a cephalaspidean, within the Anaspidea. Incongruence between the molecular data and the classifications based on morphology suggests that some of the taxonomic characters (i.e., shell, parapodia fusion) traditionally used for the classification of sea hares must be reevaluated, since they may be homoplastic. The ancestral nature of Notarchus based on the molecular evidence suggests that homoplasy may be an explanation for the morphological resemblance of this species to the more derived sea hares with highly fused parapodia and concentrated nerve ganglia. Finally, examples are given of how comparative studies of the evolution of learning mechanisms in the anaspidean clade will benefit from the phylogenetic hypothesis presented in this paper.
对三个线粒体基因（12S、16S和COI）的片段进行了测序，以重建后鳃目无楯目的分子系统发育。分子系统发育支持将Akera属置于无楯目内，该属以前被一些作者视为头楯目。分子数据与基于形态学的分类之间的不一致表明，传统上用于海兔分类的一些分类特征（即壳、鳃足融合）必须重新评估，因为它们可能是同塑性的。基于分子证据，Notarchus的祖先性质表明，同塑性可能是该物种与具有高度融合鳃足和集中神经节的更进化海兔形态相似的一种解释。最后，给出了一些例子，说明无楯目进化枝中学习机制进化的比较研究将如何受益于本文提出的系统发育假说。
