Oligaphorurini, 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 : 623-626

Monophyly of Oligaphorurini

As the main objective of this study was to investigate the relationships of Oligaphorurini genera, the taxon sampling of the remaining Onychiurinae tribes is sparse. Nevertheless, the results of our studies allow for some conclusions to be drawn regarding the status of the tribe.

In the equal- and implied-weighting parsimony analyses, the Oligaphorurini was recovered as monophyletic although only with moderate support (Figs. 1 and 2). The tribe was supported by two unambiguous character changes: postantennal organ composed of one vesicle (character 3) and postantennal organ vesicle divided into three to five lobes (character 4).

Traditionally, Oligaphorurini (as all other tribes of Onychiurinae ) have previously been defined by character combination, which mainly include: the shape of postantennal organ, build of sense organ of the third antennal segment, presence/absence of pseudocelli and anal spines, the reduction of furca, chaetotaxy of tibiotarsi, and distribution of sensory setae on the body.

A growing number of the described species with intermediate combinations of features compared to previously known ones makes tribes also becoming less characterized. Most of the morphological characters are variable and segregated

Fig. 2 Unambiguous morphological character optimization onto the strict consensus tree. Numbers above and below circles on the branches indicate character numbers and states, respectively. White and black circles represent homoplasious and nonhomoplasious states, respectively across genera. Some of this features so far considered useful is not working any more. The validity of currently recognized tribes also required detailed studies.

Cladistic analysis of the tribe Oligaphorurini presents some serious problems regarding character discovery and coding. This is compounded by Onychiurinae systematics being generally difficult due to close morphological similarity of species and a paucity of informative characters at this level of classification. The preferred phylogeny is preliminary but can serve as a working hypothesis of the evolutionary relationships within the study groups. Future studies on the phylogeny of Oligaphorurini (and Onychiurinae ) should focus on molecular systematics with comprehensive sampling.

Furcal remnant

The reduction of the furca and organization of its elements was considered as one of the most important characters to discriminate between genera of Oligaphorurini . The character was introduced by Weiner (1996) and Pomorski (1996) in their works on systematics of Onychiurinae . According to these authors, the genera maybe recognized as follows: Archaphorura and Oligaphorura possess cuticular fold and four dental setae arranged in two rows as 2 + 2 ( Fig. 4a, b ), Micraphorura has cuticular furrow and two dental setae in one row ( Fig. 4c ), whereas Dimorphaphorura has furcal remnant as a finely granulated area and is devoid of dental setae ( Fig. 4e ). For years, this scheme was widely used in the systematics of Oligaphorurini .

Recently published papers ( Shvejonkova and Potapov 2011; Babenko and Fjellberg 2015), presenting descriptions of new species with furcal features arranged in a different way, caused the collapse of the entire system (see above). Additionally, the latter authors criticize the use of reductional stages of the furca as an almost exclusive diagnostic feature, arguing that similarity in reductional stage may represent a convergence and many collembolan genera cover species with a wide range of furcal reduction.

The results of our study confirm that the furcal remnant seems to have smaller generic value than have been assumed so far. Nevertheless, the construction of furcal area provides

On. granulosus On. granulosus On. granulosus Th. encarpata Th. encarpata Th. encarpata P. eichhorni P. eichhorni P. eichhorni Ch. allanae Ch. allanae Ch. allanae D. olenae D. olenae D. olenae O. duocellata O. duocellata O. duocellata O. ambigua O. ambigua O. ambigua Ar. marcuzzii Ar. marcuzzii Ar. marcuzzii O. humicola O. humicola O. humicola O. kremenitsai O. kremenitsai O. kremenitsai M. absoloni M. absoloni M. absoloni M. nataliae M. nataliae M. nataliae M. pieninensis M. pieninensis M. pieninensis M. gamae M. gamae M. gamae

O. schoetti O. schoetti O. schoetti Ar. serratotuberculata Ar. serratotuberculata Ar. serratotuberculata O. koreana O. koreana O. koreana

O. ursi O. ursi O. ursi

O. sabulosa O. sabulosa O. sabulosa O. judithae O. judithae O. judithae O. linderae O. linderae O. linderae M. changbaiensis M. changbaiensis M. changbaiensis O. montana O. montana O. montana O. chankaensis O. chankaensis O. chankaensis O. pseudomontana O. pseudomontana O. pseudomontana D. raxensis D. raxensis D. raxensis D. hackeri D. hackeri D. hackeri

D. daii D. daii D. daii

D. steposa D. steposa D. steposa

D. eremia D. eremia D. eremia

D. melittae D. melittae D. melittae D. differens D. differens D. differens D. stojkoae D. stojkoae D. stojkoae D. caucasica D. caucasica D. caucasica D. irinae D. irinae D. irinae

D. sophyae D. sophyae D. sophyae O. groenlandica O. groenlandica O. groenlandica D. sanjiangensis D. sanjiangensis D. sanjiangensis D. sibirica D. sibirica D. sibirica

D. jingyueensis D. inyae D D.. inyae jingyueensis D D.. inyae jingyueensis D. pseudoinyae D. pseudoinyae D. pseudoinyae many useful features that can be used successfully at the level of species or groups of species.

Although this feature has been used for years in the systematics of Oligaphorurini , there is no uniform pattern of description of this structure. This is particularly evident in recent years when the system was clarified. Different authors use different terminology and classify the individual manubrial setae to different rows. This ensures that the system is less and less comparable.

In this work, we have tried to organize the system, taking into account the recent criticism. The furcal remnant can be divided into dental vestige and manubrial area ( Fig. 4a ). The first one is typically located in mid-section of abdominal segment 4 and can be developed as a cuticular fold ( Fig. 4a, b, f ), cuticular furrow ( Fig. 4c ), or a finely granulated area ( Fig. 4d, e ).

The manubrial area is comprised of setae typically arranged in three rows ( Fig. 4a ). The mp -row is located just above pseudopore and is defined by the two outer macrosetae. Above it is the mm -row of setae which is defined by two outer B q^ setae (sensu Pomorski 1996). These two rows may count from four to five (most common) to seven setae (rarely). At the top is a ma -row which can count from two to four setae. The so-called dental setae, because of their variability, are no longer recognized by their size or size of their socket. We decided that the dental setae are only these that are located on the cuticular fold ( Fig. 4a ). The dental setae of the second row (regardless of the size), which are typically placed on manubrial area, are here included in the ma -row without naming them as B dental.^ This is a typical arrangement, easily recognizable, and occurs in most species. In some cases, there are additional rows of setae between ma- and mm- rows, which are then referred to as mm ’-row(s) ( Fig. 4f ). Because these additional rows are often not arranged regularly and often have chaotically multiplied setae, we decided not to assign them to individual rows (ma ’, mm ’, mm^, etc.) but treat them all as mm ’-row(s).

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)