Higher‐level phylogenetics of linyphiid spiders (Araneae, Linyphiidae) based on morphological and molecular evidence

Abstract

This study infers the higher-level cladistic relationships of linyphiid spiders from five genes (mitochondrial CO1, 16S; nuclear 28S, 18S, histone H3) and morphological data. In total, the character matrix includes 47 taxa: 35 linyphiids representing the currently used subfamilies of Linyphiidae (Stemonyphantinae, Mynogleninae, Erigoninae, and Linyphiinae (Micronetini plus Linyphiini)) and 12 outgroup species representing nine araneoid families (Pimoidae, Theridiidae, Nesticidae, Synotaxidae, Cyatholipidae, Mysmenidae, Theridiosomatidae, Tetragnathidae, and Araneidae). The morphological characters include those used in recent studies of linyphiid phylogenetics, covering both genitalic and somatic morphology. Different sequence alignments and analytical methods produce different cladistic hypotheses. Lack of congruence among different analyses is, in part, due to the shifting placement of Labulla, Pityohyphantes, Notholepthyphantes, and Pocobletus. Almost all combined analyses agree on the monophyly of linyphioids, Pimoidae, Linyphiidae, Erigoninae, Mynogleninae, as well as Stemonyphantes as a basal lineage within Linyphiidae. Our results suggest independent origins of the desmitracheate tracheal system in micronetines and erigonines, and that erigonines were primitively haplotracheate. Cephalothoracic glandular specializations of erigonines and mynoglenines apparently evolved independently. Subocular sulci of mynoglenines and lateral sulci (e.g. Bathyphantes) evolved independently but glandular pores in the prosoma proliferated once. The contribution of different character partitions and their sensitivity to changes in traditional analytical parameters is explored and quantified.

The female genitalic morphology of “micronetine” spiders (Araneae, Linyphiidae)

“…Comparatively, among all linyphiid groups, the epigynal morphology of erigonines is the most similar to that of ''micronetines'', the former may be interpreted as a ''compressed from'' of the latter. Thus results of present study fit the phylogenetic hypothesis of Arnedo et al (2009) which suggests that the ''micronetines'' are paraphyletic with respect to the erigonines, and that both form a lineage.…”

“…Furthermore, the illustrations of linyphiid vulvae provided by Millidge (1984Millidge ( , 1993 and those of Orsonwelles by Hormiga (2002) reveal that the basal part of the spermatheca is more or less spiraled with the copulatory and the fertilization ducts (grooves). Based on the strong support for the monophyly of Linyphiidae (Hormiga 1994(Hormiga , 2000Miller and Hormiga 2004;Arnedo et al 2009) Results of the present study suggest that in ''micronetines'' and erigonines the spermathecae, as the only connection between the copulatory and the fertilization grooves, may be partially derived from the groove itself (arrow indicates the proximal end of fertilization groove). CG copulatory groove, DP dorsal plate, FG fertilization groove, MP median plate, S spermatheca, S 1 upper chamber of spermatheca, S 2 lower chamber of spermatheca, SG special gland, VP ventral plate (Figs.…”

“…In ''micronetines'' the scape is a projection of the ventral wall (double layer) of the epigynal cavity and it is usually furnished with an apical pit which houses the suprategular apophysis of the male palp during copulation (Saaristo 1975(Saaristo , 1977van Helsdingen 1965). Ventral plate scapes seem to have evolved independently more than once in linyphiids (Arnedo et al 2009;Hormiga 2000;Miller and Hormiga 2004). In addition some linyphiids have a scape on the dorsal plate.…”

“…As we have mentioned, the current phylogenetic hypothesis on Linyphiidae implies that Micronetinae are paraphyletic with respect to Erigoninae (Arnedo et al 2009). We refer to the Micronetinae (sensu Saaristo and Tanasevitch 1996) as ''micronetine'' and we use the informal label ''micronetine-erigonine'' to the clade proposed by Arnedo et al (2009) that includes the ''micronetines'' and Erigoninae. We have used the methods described by Á lvarez-Padilla and to study external and internal epigynal morphology using a scanning electron microscopy (SEM).…”

“…''Micronetinae'' is one of the largest groups among linyphiids (see Saaristo and Tanasevitch 1996) and particularly diverse in the Holarctic region. Recent cladistic work, based on both morphological characters and DNA sequences, suggests that the ''micronetines'' are not a natural group because they seem to include another large lineage, namely the erigonines (Erigoninae or dwarf spiders) (Arnedo et al 2009). Whether a grade or a clade, ''micronetines'' share a remarkably complex male and female genitalia and a relatively uniform somatic morphology.…”