First molecular data on the Western Australian Diacyclops (Copepoda, Cyclopoida) confirm morpho-species but question size differentiation and monophyly of the Alticola-group

Abstract

Size differentiation has been considered an important phenomenon in evolution, and in situ speciation was hypothesized in the past for the parapatríc subterranean Western Australian Diacyclops Kiefer, 1927 species from the a///co/<2-group, based on morphological evidence. Aims of this study are to: derive their prehminary molecular phytogenies based on mitochondríal (12S) and nuclear (18S) genes; test if morpho-species are supported by molecular data; examine monophyly of the a/ii'co/a-group; and test whether the size differences evolved in situ after colonization by a single ancestral species or resulted from different phytogeny. Analyses of the 12S sequences reveal at least six well defined clades, each corresponding to one morpho-species. The divergences are very high between all species, suggesting only a remote relationship, with those between sympatríc species with significant size difference being in excess of 27%. Surprísingly, all analyses show very high bootstrap values for the clade formed by two cosmopolitan surface-water species, Diacyclops bisetosus (Rehberg, 1880) and D. bicuspidatus (Claus, 1857), despite numerous morphological differences. The 18S dataset also supports only a remote relationship between Diacyclops scanloni Karanovic, 2006 and two other Westem Australian members of the alticola-group: D. humphreysi s. str. Pesce &De Laurentiis, 1996 and D. sobeprolatus Karanovic, 2006. Preliminary analyses suggest absence of in situ speciation and parallel evolution in the Westem Austrahan Diacyclops, interspecific size differentiation being a result of different phytogeny. The alticola-groüp may be polyphyletic, and we recognize morphological characters that define two main lineages. A possibility of cryptic speciation in the cosmopolitan D. bisetosus is also suggested, and several sequences of Diacyclops available from GenBank are recognized either as contamination or misidentification. "RÉSUMÉ La différenciation par la taille a été considérée comme un phénomène important dans l'évolution, et l'hypothèse de la spéciation in situ a été proposée dans le passé pour les espèces souterraines parapatriques du genre Diacyclops Kiefer, 1927 appartenant au groupe alticola, à partir des données morphologiques. Les objectifs de cette étude sont : élaborer leur phylogénie moléculaire préhminaire à partir de gènes mitochondriaux (12S) et nucléaires (18S) ; tester si les espèces morphologiques sont soutenues par les données moléculaires ; examiner la monophyhe du groupe alticola ; et enfin tester si les différences de taille ont évolué in situ après colonisation par une seule espèce ancestrale ou si elles résultent d'une phylogénie différente. Les analyses des séquences de 12S révèlent au moins six clades bien définis, correspondant chacun à une espèce morphologique. Les divergences sont très élevées entre toutes les espèces, suggérant seulement une relation très éloignée, avec celles parmi les espèces sympatriques ayant une différence de taille significative de plus de 27%. De façon surprenante, toutes les a...

The genus Schizopera (Copepoda, Harpacticoida) in the Pilbara region of Western Australia, with description of a new species and its molecular and morphological affinities

“…The very disjunct localities of S. roberiverensis belong to more or less interconnected waterways, but are 35, 45, and 295 km from the nearest sea shore respectively, with no Schizopera records in between. Experience from other studies on subterranean copepods with similarly wide distribution show them usually to be complexes of cryptic species (Karanovic and Krajicek 2012;Karanovic and Cooper 2012), and morphological hypotheses about the specific status of different populations of S. roberiverensis should be tested with molecular tools.…”

“…leptafurca Karanovic and Cooper, 2012;and S. uranusi Karanovic and Cooper, 2012. Using a combined morphological and molecular approach they were able to demonstrate that both explosive radiation and multiple colonisations are responsible for this unprecedented diversity, that sister species have parapatric distributions and show niche partitioning in the area of overlap, and that there is no evidence for parallel evolution, interspecifi c size differentiation being a result of different phylogeny (the latter also demonstrated for some subterranean cyclopoid copepods in the Pilbara region by Karanovic and Krajicek (2012)). Another 10 or so new species of Schizopera have been discovered in calcretes around Lake Way and Lake Maitland (T. Karanovic, unpublished data) that are awaiting formal description.…”

A new cyclopoid copepod from Korean subterranean waters reveals an interesting connection with the Central Asian fauna (Crustacea: Copepoda: Cyclopoida)

“…A proper revision of the Diacyclops/ Acanthocyclops group would require redescriptions of almost 200 species, not counting the evidence of cryptic speciation in some of the widely distributed taxa (Monchenko, 2000), which seems to be a common phenomenon in freshwater cyclopoids (Karanovic and Krajicek, 2012a). Some recent molecular work suggested that even a well-defined morphological group of the genus Diacyclops, within subterranean waters of a well-defined Australian region could be polyphyletic (Karanovic and Krajicek, 2012b). Unfortunately, most of the species of Acanthocyclops and Diacyclops were described from subterranean habitats, from very few specimens, and for some the types are no longer existent, which all makes a comprehensive revision less plausible.…”

Two new species of stygobitic Anzcyclops (Copepoda: Cyclopoida: Cyclopidae) from Australia

“…This region has been relatively well surveyed for stygofauna during the past 15 years, at least in the context of the Southern Hemisphere, and possibly about half the stygobitic species present have been formally described (Eberhard et al 2009;. With 86 named ostracod and 50 named copepod species, the ostracod and copepod faunas of the Pilbara are both rich and better known than other elements of the region's stygofauna (see Karanovic 2007;Karanovic and McKay 2010 for ostracods; Karanovic 2006Karanovic , 2010Karanovic and Hancock 2009;Karanovic and Krajicek 2012;Tang et al 2008;Karanovic and McRae 2013 for copepods).…”

“…This de-watering may potentially threaten species with small ranges, which many species of stygofauna have. While some stygobitic copepod species are widely distributed (Karanovic and Krajicek 2012;, others appear to have linear ranges of only a few kilometres (e.g. Karanovic and Cooper 2011).…”