Neanurini (Smolis, 2008)

Paśnik, Adrian Smolis Grzegorz, 2020, Phylogenetic analysis of the tribe Neanurini questions tribal classification of the subfamily Neanurinae (Collembola: Neanuridae), Organisms Diversity & Evolution 20 (3), pp. 497-509 : 503-505

Monophyly of Neanurini

In the presented phylogenetic analyses, five taxa representing the remaining tribes in the subfamily Neanurinae were used as external groups. Of these, members of three genera: Bilobella carpatica Smolis and Kaprus’ 2008 (tribe Paleonurini ), Oregonanura cascadensis Smolis, 2008 ( Paranurini ) and Sensillanura austriaca ( da Gama 1963) (Sensillanurini) were clustered together with the members of the tribe Neanurini . The results of the analyses do not confirm the monophyly of the tribe Neanurini . Moreover, the mixing of external groups with the representatives of the studied tribe influences the obtained relationships and support for the particular clades. The results obtained entitle us to question the current tribal classification of the subfamily Neanurinae and to propose changes to the current system.

The current Cassagnau classification (1989) was not carried out according to cladistic methods and is based on morphological similarities and a small set of features. In addition, the author assumed a priori the origin of all Neanurinae from Nearctic representatives of the genus Anurida belonging to the group A. hammerae . This group differs from other members of the genus because it has several features found in Neanurinae : sensilla p3 on the second and third thoracic segments shifted forward, reduction of axial chaetotaxy on the thorax and abdomen and the presence of reticulation ( Fjellberg 1985). In such a reconstructed evolution of Neanurinae , several processes have taken place in separate lines (= tribes), including the reduction of the number of eyes, the disappearance of the blue pigment and the reduction of the complexity of the mouthparts while increasing the degree of tuberculation. As the most primitive representatives of Neanurinae, Cassagnau considered the genus Paranura to have been the origin of Sensillanurini and Paleonurini , while the other three tribes, Morulodini , Neanurini and Lobellini , emerged from their own archaic ancestors: Archimorulodes , Archineanura and Archilobella , respectively. It is worth noting that the current evolutionary pattern of Neanurinae is not dichotomous and recognises the existence of paraphyletic taxa such as Sensillanurini , Paleonurini and Paranurini ( Cassagnau 1989).

Moreover, the diagnostic features used by Cassagnau to distinguish each of the tribes, thanks to new discoveries, can no longer be used to distinguish them. For example, the typical hypertrophy of the seventh sensillum on the antennae in Sensillanurini was reported in Galanura agnieskae Smolis 2000 , a member of the tribe Paleonurini . In contrast, the typical non-bilobed abdomen of Paranurini is present in Ghirkanura chernovae Kuznetsova and Potapov 1988 , so these features can no longer be used as synapomorphies of the two tribes mentioned above. Similarly, the total absence of blue pigment on body and eye characteristic for Bilobella carpatica Smolis and Kaprus’ 2008 was recorded in several Endonura species belonging to Neanurini ( Smolis 2008a) and the red and orange body colour typical for other members of the genus Bilobella also occurs in the genera Monobella or Lathriopyga , which are classified in the tribe Neanurini . The description of Xylanura oregonensis Smolis 2011 , characterised by the absence of tubercles in the first thoracic segment, shows that incomplete tuberculation can be observed in Neanurini as well as the Paranurini and Paleonurini , considered by Cassagnau to be the most primitive Neanurinae ( Cassagnau 1986, 1989).

Since the current analysis indicates the paraphyletic status of Neanurini in the Cassagnau classification, we propose to include in the Neanurini the tribes Paranurini and Sensillanurini and the bilobellan line of the Paleonurini . The first two tribes are therefore absorbed and the number of tribes in the Neanurinae is reduced to four. It should be mentioned that molecular studies based on nuclear rRNA 28S and the mitochondrial gene COII showed the monophyletic character of Paleonurini and Neanurini ( Frati and DelľAmpio 2000) . However, only one genus of Paleonurini , Bilobella , and closely related species were used in Frati and Dell’ Ampio study. Phylogenetic studies based on the chemical compounds contained in springtail cuticles, covering 380 different lipids, placed Bilobella aurantiaca Caroli 1912 among representatives of the tribe Neanurini , which supports the results obtain- ed during these analyses. Interestingly, the cladistic analysis of the genus Palmanura Cassagnau and Palacios-Vargas 1983 belonging to Sensillanurini , where two species from the Paranurini and Neanurini were used as external groups, did not fully support the monophyly of this tribe ( Palacios-Vargas et al. 2010). Cassagnau’ s classification and relationship of taxa within Neanurinae conflict also with the results of phylogenetic analyses based on cladistic methods ( D’ Haese 2002, 2003), which show the subfamily Morulininae as a sister group to Neanurinae . These analyses were based on morphological characters ( D’ Haese 2003) and the D1 and D2 regions of 28D rDNA ( D’ Haese 2002).