Stemonyphantinae, Wunderlich, 1986

Silva-Moreira, Thiago Da, Kulkarni, Siddharth & Hormiga, Gustavo, 2025, A total evidence phylogenetic analysis of the spider family Linyphiidae (Araneae, Araneoidea), Zootaxa 5685 (1), pp. 1-78 : 41-42

Stemonyphantinae ( Figs 3 , 10 )

Stemonyphantines have been quite consistently hypothesized as the sister group of a clade with all other Linyphiidae (e.g., Wunderlich 1986; Hormiga 1994a, b; Arnedo et al. 2009; Gavish-Regev et al. 2013; Frick and Scharff 2013; Dimitrov et al. 2017). Hormiga et al. (2021) expanded the Stemonyphantinae circumscription by including Weintrauboa and Putaoa (previously placed in Pimoidae ) and the genus Pecado . The placement of Stemonyphantinae as the sister lineage to all other Linyphiidae did not change. Silva-Moreira and Hormiga (2022) did retrieve Pecado impudicus (Denis) as a sister group of Stemonyphantes using only phenotypic data. Pecado was erected by Hormiga & Scharff (2005) to place a single species transferred from Labulla Simon , based on a phenotypic cladistic analysis of the latter genus.

Our preferred hypothesis ( Fig. 3 ) concurs with Hormiga et al. (2021) in both the circumscription and placement of Stemonyphantinae : for the first time, Pecado position in Stemonyphantinae is supported by both molecular and phenotypic evidence. The monophyly of Stemonyphantinae (sensu Hormiga et al., 2021) is strongly supported in all analyses. The monophyly of Stemonyphantinae is supported by six phenotypic synapomorphies: male pedipalp with five or more macrosetae on the tibia (char 5), a dorsal or meso-dorsal oriented cymbium (char 28) with an ecto-marginal process (char 32), paracymbium with an anterobasal apophysis (char 49), the presence of ventral macrosetae on metatarsus I (char 224), and trichobothria on metatarsus IV (char 225).

The placement of Weintrauboa and Putaoa within Stemonyphantinae required the reinterpretation of some palpal homologies (see discussion in Hormiga et al. 2021). The male palp morphology of Pecado shares some features with that of Stemonyphantes , such as the presence of a secondary apical tegular membrane and a tegular ridge ( Gavish-Regev et al. 2013 fig. 3A–B—char 82). Both the conductor (char 81) and the median apophysis (char 82) are widespread throughout Araneoidea, and the loss of both of those sclerites is thought to be a synapomorphy of Linyphiidae ( Griswold et al. 1998, 2005; Hormiga 1994b). The analyses of Coddington (1990a) and Griswold et al. (1998) provided the cladistic foundation for studies to address the male palp homologies of araneoids. When a single tegular sclerite is found in araneoids, it is often difficult to determine whether it is a homolog of the conductor or of the median apophysis. This latter problem has led some workers to treat such sclerite as a conductor by default unless there is evidence to the contrary (e.g., Coddington 1990b; Griswold et al. 1998; Griswold et al. 2005). While such a pragmatic approach may provide a consistent system to code the sclerite in a character matrix, it does not necessarily resolve the homology problem per se. The conductor morphology of araneoids is very diverse, varying from a small and membranous (e.g., Pimoa ) to a large and heavily sclerotized apophysis (e.g., in many araneids). In Pimoa , Weintrauboa , Putaoa , Stemonyphantes , Pecado , and Labulla , it is possible to see a membranous structure on the tegulum (in Nanoa , the conductor is slightly more sclerotized, Hormiga et al. 2005). In both Weintrauboa and Putaoa , this structure is discrete and interpreted as a membranous conductor as it is located on the apical part of the tegulum. In Labulla and Pecado , this structure is named “ectal tegular flap” or “tegular membrane” ( Hormiga and Scharff 2005), and while in Pecado , it is positioned more apically, and in Labulla , it is on the ectal side of the tegulum. The position of the membrane on Stemonyphantes species varies but is usually found closer to the suprategulum ( Gavish-Regev et al. 2013). Gavish-Regev et al. (2013 figs 3A, B) and Hormiga et al. (2021) proposed that the tegular ridge is a homolog of the conductor in Stemonyphantes . In Pecado we can observe a tegular structure that the same study interpreted as a conductor homolog. Thus, we have coded all stemonyphantines as having a conductor following Hormiga et al. (2021). We also interpret the median apophysis of Weintrauboa (Hormiga 2003, figs 1G, 5C) and part of the Putaoa pimoid embolic process ( Hormiga & Tu, 2008, figs 3B, C) as part of the suprategulum (char 72), the distal suprategular apophysis (char 78). Our phylogenetic hypothesis suggests that the alveolar sclerite (char 24) and the pimoid cymbial sclerite (char 35), both synapomorphic features of pimoids in Tu & Hormiga (2008), are now understood as convergent features ( Fig. 10 ).

Labulla thoracica ( Figs 3 , 10 )

Labulla thoracica is the type species and the only representative of the genus Labulla Simon in our dataset. The position of Labulla as one of the earliest branches of Linyphiidae ( Figs 1 , 3 , Supplementary Figs 1–4 ) is one of the most stable topological results in all analyses that include molecular data, regardless of the optimality criteria used.

Hormiga & Scharff (2005) suggested that the Labulla clade (with three species) was sister to Tenuiphantes + Bolyphantes (here the Lepthyphantinae , see below) based on the following synapomorphies: ventral position of the ectal suprategular apophysis, the bifid shape of this apophysis, the presence of paracymbial apophyses and presence of a ventral plate epigynal scape ( Hormiga and Scharff 2005, fig. 25). While in some of our analyses (with MORPH dataset) we recovered L. thoracica (and Ipa keyserlingi ) as sister group to the Lepthyphantinae , our working hypothesis did not recover the same sister-group relationship. This latter result may be due to the lack of molecular data or the absence of other Labulla species in our analyses. Labulla has at least one autapomorphy, the epigynal lateral lobes (char 141), as well as more than 30 other transformations, which include a cymbium much smaller than the bulb (char 25), radix with both a tailpiece (char 100) and a terminal apophysis (char 104) and an epigynum with atrium and spiral grooves (char 143) ( Fig. 10 ). Given the uncertainty we described above, we feel that our study does not have sufficient evidence to place Labulla in any of the major lineages we describe. To this date, Hormiga & Scharff (2005) is still the only study to include more than one representative of the genus Labulla in a phylogenetic analysis. Future studies should include the other two species of this genus to test its placement further and thus, we prefer to leave it as incertae sedis.

Figures

FIGURE 1. Preferred hypothesis: Bayesian analysis tree from the total evidence dataset M4 (M4_MB) depicting the proposed new arrangement. Colors represent same previous subfamilial assignments. Black arrow indicates “linyphioids” node. Red arrow indicates Linyphiidae node. Red colored rectangles indicate the correspondent Superclades. Green colored rectangle indicate the novel circumscription for the MPME clade. Black squares represent nodes with full support (posterior probability =1).

FIGURE 3. Partial tree from the preferred hypothesis for linyphioids (M4_MB). Pimoidae, Stemonyphantinae, and Pocobletinae new subfamily. Black-colored squares represent nodes with posterior probability =1; gray-colored squares represent nodes with posterior probability between 0.95 and 0.99.

FIGURE 10. Optimization of the phenotypic matrix characters (DELTRAN optimization) on the pruned preferred hypothesis tree. Dashed line delimits the linyphioid clade. Solid line delimits Linyphiidae. Black circles indicate non-homoplasious synapomorphies, while white circles indicate homoplasious transformations.