Along the same lines, Di Marco et al.8 emphasized that, in conservation science, some historically under-studied taxa were receiving more attention today, but underlined that a taxonomic bias toward taxa that are threatened or less rich in biodiversity still exists.
Further research is warranted on under-represented taxa (e.g., herpetofauna and invertebrates) in literature and long-term effects of forest management on biodiversity.
Such a data availability matrix [ 4] clearly highlights under-represented taxa and provides an intuitive picture of the dataset sparseness.
Thus, we consider a integrative approach as most suitable for molecular species delineation in little known, putatively widespread and notoriously under-sampled taxa such as meiofauna in remote areas.
What is an efficient workflow for large-datasets with dense sampling coverage and thus high-quality COI barcoding output, may be inapplicable for datasets in little known and putatively under-sampled taxa.
For example, while the monophyly of many classically diagnosed Rodentia groups (Hystricognathi – a grouping of Myoxidae and Sciuridae – and the Muroidea/Dipodidae group) have been supported by molecular analyses (eg [ 4, 7]), relationships between these groups as well as the placement of a few under-studied taxa (such as the Anomaluridae) are controversial.
Previous partulid molecular phylogenies [ 35, 39, 43- 45] have either ignored or under-sampled Western Pacific taxa, the most comprehensive representation being 4 western species of Partula [ 44].
Out of the 85 taxa under analysis, 48 (56.5%) are either under-represented or not represented in any way in genebanks and therefore flagged as HPS for collecting (Table 3, Table S1).
It may be questioned how real these species are under the conditions of DNA barcoding: while there are 4 reciprocally monophyletic taxa under analysis of mtCOI (Appendix I), in no case do these groups fit the "10× rule" [34] that might indicate substantial temporal and demographic isolation that may be predictive of reproductive isolation.
The exceptions to this are MUSCLE and FSA, which both show a noticeable improvement under 32-taxa simulations.
