Synxenidae, Silvestri, 1923

Short, Megan & Vahtera, Varpu, 2017, Phylogenetic relationships of millipedes in the subclass Penicillata (Diplopoda) with a key to the genera, Journal of Natural History 51 (41 - 42), pp. 2443-2461 : 2454

Family Synxenidae

The family Synxenidae , represented by the single genus Phryssonotus , is shown to be monophyletic, with strong nodal support (JF 100%/87%; BS 93%) across all analyses. The ML analysis shows strong support for a basal position for the family. Species in this family have 15–17 pairs of legs, in contrast to species in the remaining two families with 13 pairs (11 pairs in one species). Reduction in segments and reduction in leg pairs are considered to be derived traits in the order ( Condé 1970).

Phryssonotus novaehollandiae has been identified from many parts of Australia ( Short and Huynh 2009). The ML analysis and the pairwise distances (Appendix 3) both suggest that South Australian and Western Australian populations (lab numbers 4 and 5) differ from the three Victorian populations (lab numbers 1, 2 and 3). Hence, it seems likely that P. novaehollandiae actually includes more than one species. The ML analysis further indicates that the thelytokous populations (lab numbers 1 and 2, indicated with an asterisk in Figures 2 and 3 ) do not form a separate clade from the geographically closest sexually reproducing population, indicating that parthenogenesis may be a recent localised response in the two populations, both of which inhabit a coastal habitat.

Figures

Figure 2. Optimal maximum likelihood tree (lnL = −10,376.678214) based on molecular data (COI, 16S, 18S). Bootstrap support values (> 50%) shown on the nodes. Thelytokous populations of P. novaehollandiae (Silvestri, 1923) and the one confirmed thelytokous population of Polyxenus lagurus (Linnaeus, 1758) are marked with an asterisk.

Figure 3. Strict consensus of 626 MP trees based on combined morphological and molecular data. Jackknife (JF) support values (> 50%) shown above the nodes (in parentheses, JF values based on molecular data only). Thelytokous populations of Phryssonotus novaehollandiae (Silvestri, 1923) and the one confirmed thelytokous population of Polyxenus lagurus (Linnaeus, 1758) are marked with an asterisk.