Abstract
BackgroundThe arthropod class Diplopoda is a mega-diverse group comprising >12,000 described millipede species. The history of taxonomic research within the group is tumultuous and, consequently, has yielded a questionable higher-level classification. Few higher-taxa are defined using synapomorphies, and the practice of single taxon descriptions lacking a revisionary framework has produced many monotypic taxa. Additionally, taxonomic and geographic biases render global species diversity estimations unreliable. We test whether the ordinal taxa of the Diplopoda are consistent with regards to underlying taxonomic diversity, attempt to provide estimates for global species diversity, and examine millipede taxonomic effort at a global geographic scale.Methodology/Principal FindingsA taxonomic distinctness metric was employed to assess uniformity of millipede ordinal taxa. We found that ordinal-level taxa are not uniform and are likely overinflated with higher-taxa when compared to related groups. Several methods of estimating global species richness were employed (Bayesian, variation in taxonomic productivity, extrapolation from nearly fully described taxa). Two of the three methods provided estimates ranging from 13,413–16,760 species. Variations in geographic diversity show biases to North America and Europe and a paucity of works on tropical taxa.Conclusions/SignificanceBefore taxa can be used in an extensible way, they must be definable with respect to the diversity they contain and the diagnostic characters used to delineate them. The higher classification for millipedes is shown to be problematic from a number of perspectives. Namely, the ordinal taxa are not uniform in their underlying diversity, and millipedes appear to have a disproportionate number of higher-taxa. Species diversity estimates are unreliable due to inconsistent taxonomic effort at temporal, geographic, and phylogenetic scales. Lack of knowledge concerning many millipede groups compounds these issues. Diplopods are likely not unique in this regard as these issues may persist in many other diverse yet poorly studied groups.
Highlights
The Linnean system of biological classification is an information-rich organizational scheme that has been in existence for over 250 years
Global Species Diversity Estimates The Bayesian methods of Wilson & Costello [38] were unable to provide an estimate of the total global diversity of millipedes due to a lack of an asymptote in the rarefaction curve (Figure 2B)
In the study presented we have shown that the ordinal-level taxa contained within the class Diplopoda are not equivalent based on a metric of taxonomic distinctness that is calculated from the classification-based tree
Summary
The Linnean system of biological classification is an information-rich organizational scheme that has been in existence for over 250 years Despite its antiquity, it remains, even today, the framework on which almost every biological question relies; it is the principal mode for communicating species level data within a relational and hierarchical context. Contained within the Linnean hierarchical schema is a wealth of information from which we can draw inferences regarding the tempo, mode, and pattern of evolutionary diversification. These classifications are fundamentally a hypothesis of phylogeny and can be used in conjunction with fossil and biogeographic data to make hypotheses concerning evolutionary processes that can be tested using modern phylogenetic techniques. We test whether the ordinal taxa of the Diplopoda are consistent with regards to underlying taxonomic diversity, attempt to provide estimates for global species diversity, and examine millipede taxonomic effort at a global geographic scale
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
