The phylogeny of dionychan spiders

RAMÍREZ, M. J.

Gent, Bélgica

Congreso; 16th International Congress of Arachnology; 2004

International Society of Arachnology

Sometimes regarded as the crown group of spiders, Dionycha, the two clawed spiders, are a large conglomerate of seventeen families, comprising about 2,000 genera and more than 13,000 species, 35% of the spider species known to date.  Is Dionycha monophyletic?  Where, in the phylogeny of entelegyne spiders, did they come from?  What are the sister groups of the idiosyncratic Salticidae and Thomisidae?  How do we define a liocranid, or a miturgid?  I tried to answer these questions and much more through a phylogenetic analysis based in morphological characters.  I reviewed most morphological systems and proposed characters, and built a unified homology system spanning much of the spectrum of variation within Araneomorphae.  Testing monophyly requires an ample sampling of outgroups, and for this study I included about 40.  Among them there are many members of the RTA clade of Entelegynae (especially Lycosoidea), the main lineages of Araneomorphae, from the basal clades (Hypochilidae, Austrochilidae, Filistatidae), to the main groups of entelegynes (Eresoidea, Orbiculariae, Palpimanoidea, Amaurobiidae, Amphinectidae, Titanoecidae, Zodariidae, Lycosoidea).  All dionychan families are represented, and the most problematic in terms of monophyly are more intensively sampled (14 genera of Liocranidae, 11 of Miturgidae, 15 of Corinnidae).  The dataset comprises about 400 characters scored for about 140 taxa, and is documented with 4800 original SEM images.  The resulting trees are sensitive to variations in analysis parameters (e.g., weighting in function of homoplasy), and several groups have very low support indices, including Salticidae and Sparassidae.  Dionycha is not monophyletic.  It seems that several areas of the tree will need a most intense taxon sampling and continued work, but the way in that phylogenetic analyses are classically conducted is resistant to accumulation of knowledge.  I discuss some issues of accumulation and documentation of phylogenetic data.