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Vol. 51 No. 2, 2012
Systematic Study of the Simocephalus Sensu Stricto Species Group (Cladocera: Daphniidae) from Taiwan by Morphometric and Molecular Analyses
Shuh-Sen Young1,*, Mei-Hui Ni2, and Min-Yun Liu3
1Department of Applied Science, National Hsinchu University of Education, Hsinchu 300, Taiwan
2Hsinchu Municipal Hsinchu Elementary School, Hsinchu 300, Taiwan
3National Applied Research Laboratories, Taiwan Ocean Research Institute, Taipei 106, Taiwan
Shuh-Sen Young, Mei-Hui Ni, and Min-Yun Liu (2012) There is some controversy regarding the traditional taxonomy of the Simocephalus
sensu stricto species group. We conducted molecular and morphometric
analyses to differentiate the 3 species from this group found in
Taiwan: S. vetulus (O.F. Müller, 1776), S. vetuloides Sars, 1898, and S. mixtus
Sars, 1903. The landmark method was employed, followed by a transfer
into 24 characteristic values for a principal component analysis (PCA),
the results of which indicated morphometric overlap among these
species. The dorsal angle, brood size, and body length were smallest in
S. vetulus, medium in S. vetuloides, and largest in S. mixtus. In the Simocephalus
sensu stricto group from Taiwan, the dorsal angle and body length were
significantly correlated with brood size in a quadratic manner. In the
molecular analysis, 98 specimens of Simocephalus were used, and the
641-bp mitochondrial DNA cytochrome oxidase subunit 1 sequence was
employed as a marker to analyze the genetics of S. vetulus, S. vetuloides, S. mixtus, S. serrulatus (Koch, 1841), and S. heilongjiangensis Shi and Shi, 1994. Simocephalus vetulus, S. vetuloides, and S. mixtus
shared several haplotypes, and the interspecific genetic distance was
merely 0.00671-0.00785, which is within the range of intraspecific
differences. We concluded that S. vetulus, S. vetuloides, and S. mixtus in Taiwan belong to the same species and should be treated as S. cf. vetulus. The number of species of Simocephalus in Taiwan is thus reduced to 3: S. cf. vetulus, S. serrulatus, and S. heilongjiangensis.
Key words: Systematics, Biodiversity, Simocephalus, Freshwater zooplankton.
*Correspondence: E-mail:shuh@mail.nhcue.edu.tw
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