Morphology to the rescue: molecular data and the signal of morphological characters in combined phylogenetic analyses-a case study from mysmenid spiders (Araneae, Mysmenidae), with comments on the evolution of web architecture

Abstract

The limits and the interfamilial relationships of the minute orb-weaving symphytognathoid spiders have remained contentious and poorly understood. The circumscription and diagnosis of the symphytognathoid family Mysmenidae have always been elusive, and its monophyly has never been thoroughly tested. We combine sequence data from six genes with a morphological dataset in a total-evidence phylogenetic analysis (ca. 6100 characters, 109 taxa: 74 mysmenids), and explore the phylogenetic signal of the combined dataset, individual genes, and gene combinations with different parsimony methods and model-based approaches. Several support values and parameter-sensitivity schemes are explored to assess stability of clades. Mysmenidae monophyly is supported by ca. 20 morphological and ca. 420 molecular synapomorphies. Mysmenidae is monophyletic under all combined analyses that include morphology. Almost no gene or gene combination supports Mysmenidae monophyly. Symphytognathoids are delimited to include: (Theridiosomatidae (Mysmenidae (Synaphridae (Anapidae + Symphytognathidae)))). Micropholcommatids are a lineage nested within the anapid clade and thus are synonymized with Anapidae (Micropholcommatinae New Rank). We provide morphological diagnoses for all symphytognathoid families and discuss the behavioural evolutionary implications of our hypotheses of relationships. The planar orb web evolved independently twice from three-dimensional webs. The orb web was modified into sheet or cobwebs three times independently. The spherical mysmenine web has a single origin. Kleptoparasitism evolved once in mysmenids. We comment on the discrepancies and lack of resolving power of the molecular datasets relative to the morphological signal, and discuss the relevance of morphology in inferring the total-evidence phylogenetic pattern of relationships.