title: Resolving the phylogeny of a speciose spider group, the family Linyphiidae (Araneae).
abstract: For high-level molecular phylogenies, a comprehensive sampling design is a key factor for not only improving inferential accuracy, but also for maximizing the explanatory power of the resulting phylogeny. Two standing problems in molecular phylogenies are the unstable placements of some deep and long branches, and the phylogenetic relationships shown by robust supported clades conflict with recognized knowledge. Empirical and theoretical studies suggest that increasing taxon sampling is expected to ameliorate, if not resolve, both problems; however, sometimes neither the current taxonomic system nor the established phylogeny can provide sufficient information to guide additional sampling design. We examined the phylogeny of the spider family Linyphiidae, and selected ingroup species based on epigynal morphology, which can be reconstructed in a phylogenetic context. Our analyses resulted in seven robustly supported clades within linyphiids. The placements of four deep and long branches are sensitive to variations in both outgroup and ingroup sampling, suggesting the possibility of long branch attraction artifacts. Results of ancestral state reconstruction indicate that successive state transformations of the epigynal plate are associated with early cladogenetic events in linyphiid diversification. Representatives of different subfamilies were mixed together within well supported clades and examination revealed that their defining characters, as per traditional taxonomy, are homoplastic. Furthermore, our results demonstrated that increasing taxon sampling produced a more informative framework, which in turn helps to study character evolution and interpret the relationships among linyphiid lineages. Additional defining characters are needed to revise the linyphiid taxonomic system based on our phylogenetic hypothesis.
authors.affiliation: College of Life Sciences, Capital Normal University, Beijing 100048, PR China.
authors.forename: Fang
authors.initials: F
authors.lastname: Wang
authors.affiliation: Department of Biological Sciences, The George Washington University, Washington, DC 20052, USA.
authors.forename: Jesus A
authors.initials: JA
authors.lastname: Ballesteros
authors.affiliation: Department of Biological Sciences, The George Washington University, Washington, DC 20052, USA.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Hormiga
authors.affiliation: Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, PR China.
authors.forename: Douglas
authors.initials: D
authors.lastname: Chesters
authors.affiliation: College of Life Sciences, Capital Normal University, Beijing 100048, PR China.
authors.forename: Yongjia
authors.initials: Y
authors.lastname: Zhan
authors.affiliation: College of Life Sciences, Capital Normal University, Beijing 100048, PR China.
authors.forename: Ning
authors.initials: N
authors.lastname: Sun
authors.affiliation: Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, PR China.
authors.forename: Chaodong
authors.initials: C
authors.lastname: Zhu
authors.affiliation: College of Life Sciences, Capital Normal University, Beijing 100048, PR China.
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
authors.affiliation: College of Life Sciences, Capital Normal University, Beijing 100048, PR China. Electronic address: tulh@cnu.edu.cn.
authors.forename: Lihong
authors.initials: L
authors.lastname: Tu
mesh_terms: D000818:Animals; D005075:Biological Evolution; D049810:Genetic Speciation; D010802:Phylogeny; D013112:Spiders / Q000033:anatomy & histology / Q000145:classification* / Q000235:genetics
keywords: Character transformations; Cladogenetic events; Epigynal morphology; Linyphiids; Phylogenetics