Differential intraspecific genetic variations of the closely related, wide-ranged freshwater copepods Cyclops vicinus Ul
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RESEARCH PAPER
Differential intraspecific genetic variations of the closely related, wide‑ranged freshwater copepods Cyclops vicinus Uljanin, 1875 and C. kikuchii Smirnov, 1932 Imane Sioud1 · Wataru Makino1 · Jotaro Urabe1 Received: 22 March 2020 / Accepted: 27 October 2020 © The Japanese Society of Limnology 2020
Abstract Although Cyclops vicinus Uljanin, 1875 and C. kikuchii Smirnov, 1932 are broadly distributed in Eurasia, the genetic divergences between European and Asian populations have been investigated in neither species. In Japan, the nomenclature and distinction between these two congeners are still questionable (thus, hereafter C. vicinus s.l.). We determined the taxonomic position of the Japanese C. vicinus s.l. by morphological analyses and by sequencing nuclear internal transcribed spacer 1(ITS-1) and the mitochondrial 12S (mt12S) genes. The ITS-1 phylogeny separated Japanese C. vicinus s.l. into two genetic groups; one was clustered with European C. kikuchii (thus, CkikJPN), while the other was clustered with European C. vicinus (thus, CvicJPN). Morphological analyses using the lengths of terminal furcal setae revealed that CkikJPN and CvicJPN correspond to C. kikuchii and C. vicinus, respectively. These results revealed that C. vicinus and C. kikuchii in Japan are confidently the same species as those in Europe. The degree of divergence in the mt12S between Japanese and European populations varied largely between the species, as it was nearly at the interspecific level in C. kikuchii, while it was at the intraspecific level in C. vicinus; it is the first case in which the genetic divergence between the European and Asian population is greatly different among closely related species of freshwater copepods. Keywords Cryptic species · Freshwater biodiversity · Genetic divergence · Quadratic discriminant analysis · Zooplankton
Introduction Copepods appear in nearly all freshwater habitats (Boxshall and Defaye 2007). They play an essential role in the aquatic food web as intermediate consumers (Reid and Williamson 2010), and can also be bioindicators of changes in water quality (Maier 1998; Perbiche-Neves et al. 2016; Silva 2011). Due to their relatively small size, it is sometimes challenging to distinguish morphologically similar, closely related species merely based on morphology. That Handling Editor: Teruhiko Takahara Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10201-020-00647-7) contains supplementary material, which is available to authorized users. * Imane Sioud [email protected] 1
Graduate School of Life Sciences, Tohoku University, Aramaki aza aoba, Sendai, Miyagi 980‑8578, Japan
is the case for Cyclops vicinus Uljanin, 1875 and its close relative Cyclops kikuchii Smirnov, 1932, both of which are distributed in Eurasia (Dussart and Defaye 2006; Hołyńska and Wyngaard 2019; Lee et al. 2005; Rylov 1948). Cyclops kikuchii was initially described based on specimens collected in Japan by Smirnov (1932). This species was once tre
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