Filling the gaps: descriptions of unnamed species included in the latest molecular phylogeny of Pholcidae
(Published in Zootaxa, 2019; https://doi.org/10.1164/zootaxa.4546.1.1)
 
Large percentages of unnamed (or unidentified) species are the rule in molecular spider phylogenies that aim at comprehensiveness. Some recent examples:
  • Molecular phylogeny of the entire order: ~41% of the species unnamed (Wheeler et al. 2017).
  • Phylogeny of euophrine jumping spiders: ~38% unnamed (Zhang & Maddison 2013)
  • Phylogeny of goblin spiders: ~40% unnamed (Busschere et al. 2014)
The reasons for including unnamed species in phylogenies are obvious and easily justified. Scientifically there is nothing fundamentally wrong with including unnamed species in phylogenies. However, phylogenies with large numbers of unnamed species resemble ghost towns: they may be fine and functional, but they do not fulfil their proper meaning. After all, “we construct phylogenies to explain patterns of organismic diversity. Molecular data certainly contribute, but when nothing is known about organisms except their DNA, there are no evolutionarily interesting patterns to explain…” (Lipscomb et al. 2003).

In our own recent phylogeny of daddy longlegs spiders (Pholcidae) (Eberle et al. 2018) the percentage of unnamed species was at ~22%. The primary aim of this paper is simply to fill gaps, i.e. to name some of the undescribed taxa included in that paper. As a result of this paper and of the simultaneously published paper on Sri Lanka Pholcidae, the percentage of undescribed species is now down to 18% (106 of 600 species).

References

Busschere, C. de, Fannes, W., Henrard, A., Gaublomme, E., Jocqué, R. & Baert, L. (2014) Unravelling the goblin spiders puzzle: rDNA phylogeny of the family Oonopidae (Araneae). Arthropod Systematics & Phylogeny, 72(2), 177–192.

Lipscomb, D., Platnick, N. & Wheeler Q. (2003) The intellectual content of taxonomy: a comment on DNA taxonomy. Trends in Ecology and Evolution, 18(2), 65–66.

Wheeler, W.C, Coddington, J.A., Crowley, L.M. et al. (2017) The spider tree of life: phylogeny of Araneae based on target‐gene analyses from an extensive taxon sampling. Cladistics, 33(6), 574–616.

Zhang, J. & Maddison, W.P. (2013) Molecular phylogeny, divergence times and biogeography of spiders of the subfamily Euophryinae (Araneae: Salticidae). Molecular Phylogenetics and Evolution, 68, 81–92.