Increasing Information Content and Diagnosability in Family-Level Classifications.

Area of Science:

• Systematics and Phylogenetics
• Arachnology
• Evolutionary Biology

Background:

• Higher-level taxonomic classifications must accommodate monotypic taxa and depauperate evolutionary lineages.
• Spider classification at the family level requires well-defined and informative taxa, as 'incertae sedis' is not permitted.
• The suprafamilial clade Orbipurae, comprising Nephilidae, Phonognathidae, and Araneidae, presents a classification challenge.

Purpose of the Study:

• To propose a revised family-level classification for the Orbipurae clade that enhances diagnosability, information content, and conservation utility.
• To address the taxonomic status of the depauperate lineage Paraplectanoides.
• To stabilize the phylogenetic topology of Orbipurae using new genomic data.

Main Methods:

• Phylogenomic analysis using subgenomic data to resolve the Orbipurae clade's topology.
• Comparative analysis of classification schemes, evaluating a 'splitting' versus 'lumping' approach for spider families.
• Revising family definitions and proposing a new monogeneric family, Paraplectanoididae.

Main Results:

• The proposed 'splitting' classification, recognizing Paraplectanoididae fam. nov., is superior to lumping these families into Araneidae sensu lato.
• New subgenomic data support the proposed family-level classification and stabilize the Orbipurae phylogeny.
• The classification accommodates depauperate evolutionary lineages like Paraplectanoides, enhancing taxonomic utility.

Conclusions:

• Classifications must be flexible to incorporate depauperate lineages, exemplified by the spider Paraplectanoides.
• The redefined Araneidae and the new family Paraplectanoididae improve the systematic cataloguing of spider families.
• Comparable ages of similarly ranked taxa, where applicable, benefit comparative biology.