Micraphorura, Bagnall, 1949

Weiner, Grzegorz Paśnik Wanda M., 2017, First phylogenetic analysis of the tribe Oligaphorurini (Collembola: Onychiuridae) inferred from morphological data, with implications for generic classification, Organisms Diversity & Evolution 17 (3), pp. 619-631 : 623

Monophyly of Micraphorura and Oligaphorura

The monophyly of these two genera is not supported by the present work. All species of Micraphorura and majority species of Oligaphorura are clustered together within clade B (Fig. 1). The remaining species of Oligaphorura are placed in clade A and O. groenlandica , the type species of the genus, is placed in clade C (Fig. 1).

Traditionally, both genera were recognized almost exclusively on the basis of the build of furcal remnant. Oligaphorura was characterized by the presence of cuticular fold and four so-called dental setae arranged in two rows as 2 + 2 ( Fig. 4a, b ), whereas Micraphorura has cuticular furrow and two B dental^ setae in one row ( Fig. 4c ).

The term B dental setae^ was introduced ( Weiner 1996) to describe the setae located on dental area (= cuticular fold) or just behind in first row of manubrial setae (row B ma^) and differing in the size and/or the size of its socket (= setulae according to Pomorski 1996, 1998). The character was recently debated by Babenko and Fjellberg (2015), who stated that this feature is subjective and so-called dental setae differ from other sternal setae on abdominal segment 4 only occasionally. Our studies confirm that these setae show intra- and interspecific variability.

The further complications bring recently described species of Oligaphorura and Micraphorura ( Shvejonkova and Potapov 2011; Babenko and Fjellberg 2015) which do not have furca reduced to cuticular fold or furrow but small area of fine granulation, feature which is characteristic for Dimorphaphorura . Thus, several different patterns of furcal rudiment can be found among species of these two genera.

Moreover, O. groenlandica , the type species of the Oligaphorura , falls outside of the other sampled species of the genus and is placed together with the members of Dimorphaphorura into clade C (Fig. 1). Previously, there were some misunderstandings regarding the diagnosis of Oligaphorura presented by Pomorski (1996, 1998), Fjellberg (1998), and Weiner (1996). This species has furcal area without cuticular fold or deep pocket considered as a characteristic of the genus but an area with fine granulation in anterior third of the abdominal sternum IV (typical for the species of Dimorphaphorura ). In the material recently collect- ed on Spitzbergen, we found the specimens with a fine granulated area which the posterior edge seems to be folded with coarser granulation.

Figures

Fig. 4 Abdominal sternite IV showing organization of furcal remnant. a, b Oligaphorura ursi Fjellberg, 1984; c Micraphorura gamae Buşmachiu and Weiner, 2013; d Oligaphorura groenlandica (Tullberg, 1876); e Dimorphaphorura inya Weiner and Kaprus, 2014; f Protaphorura eichhorni (Gisin, 1954)