Abstract
Discord between molecular and morphological datasets was observed in two pairs of species of Australian millipedes in the family Paradoxosomatidae using morphological and molecular phylogenetic analysis (mitochondrial COI rDNA and 16 rRNA, and nuclear 28S rRNA). Close to the presumed distributional boundary between Pogonosternumnigrovirgatum (Carl, 1912) and Pogonosternumjeekeli Decker, 2017, near Dargo in Central Gippsland, Victoria, Pogonosternum specimens were collected which are phylogenetically closer to P.jeekeli in COI and 16S sequences, but are morphologically closer to P.nigrovirgatum. At Mount Osmond, Adelaide, South Australia, eight morphologically typical Somethuscastaneus (Attems, 1944) specimens were collected are phylogenetically closer to S.castaneus in 28S genealogy, but three of the eight are closer to S.lancearius Jeekel, 2002 in COI genealogy. These two cases are discussed in terms of hybridisation, past introgressive hybridisation events and aberrant morphology.
Highlights
While many cases of hybridisation in plants, fungi and animals are well known (Alix et al 2017, Crossman et al 2016, Ottenburghs et al 2016, Stukenbrock 2016, Yazicioglu et al 2016), examples in millipedes are scarce. Pedroli-Christen and Scholl (1990) studied a hybrid zone between the two chordeumatidans Rhymogona cervina (Verhoeff, 1910) and Rhymogona silvatica (Rothenbühler, 1899) in the Swiss Alps
The final alignments consisted of 618 bp of c oxidase subunit I (COI) mtDNA and 1206 bp of 28S rRNA in Somethus, and 1158 bp for COI+16S in Pogonosternum
The trees constructed from individual genes did not show significant conflicts in topology and no significant incongruence among the three genes was revealed by the incongruence length difference (ILD) test (P > 0.81 in all of the pairwise comparisons), and the sequences were concatenated into a dataset comprised 1158 characters for phylogenetic analysis in Pogonosternum
Summary
While many cases of hybridisation in plants, fungi and animals are well known (Alix et al 2017, Crossman et al 2016, Ottenburghs et al 2016, Stukenbrock 2016, Yazicioglu et al 2016), examples in millipedes are scarce. Pedroli-Christen and Scholl (1990) studied a hybrid zone between the two chordeumatidans Rhymogona cervina (Verhoeff, 1910) and Rhymogona silvatica (Rothenbühler, 1899) in the Swiss Alps. Later revisions (Pedroli-Christen and Scholl 1996; Scholl and Pedroli-Christen 1996) placed both nominal species within R. montivaga (Verhoeff, 1894), either as a synonym (R. silvatica) or as a subspecies (R. cervina). Later searches of the area for I. beattyi were unsuccessful, and Jorgensen (2009) was unable to determine whether the one known male of I. beattyi was a hybrid of E. leachii and A. evides, or an aberrant individual of one of these two euryurid species. Introgressive hybridisation has not yet been reported in the class Diplopoda
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