Phylogenetic relationships in Stephanopinae: systematics of Stephanopis and Sidymella based on morphological characters (Araneae: Thomisidae)

Abstract

The subfamily Stephanopinae stands out among other groups in Thomisidae by its significative number of species and genera that are still in need of taxonomic reviews and phylogenetic studies, which would help us to better comprehend their diversity and evolutive relationships. The polyphyletism of Stephanopinae has been frequently recovered in recent phylogenetic works, indicating the necessity to perform monophyly tests for its component genera and proper investigations on the composition of the group. Therefore, the present study aimed the redefinition of the morphological boundaries of Stephanopis and Sidymella through taxonomic reviews, as well as test the monophyly of both genera discussing their phylogenetic relationships. To do so, a data matrix with 117 morphological characters, coded for 77 terminal taxa, was assembled. This matrix was submitted to parsimony analysis (under equal weights and an implied weighting scheme) and bayesian inference. Branch supports were estimated through relative Bremer support index and symmetric resampling, while nodal stability was represented by “Navajo rugs” of a sensitivity test. The obtained results indicate that both Sidymella and Stephanopis are polyphyletic, with the component species of this latter emerging in five distinct groups: the “cambridgei clade”, which has all its species transferred to Isala; the “championi clade”, proposed here as Paratobias gen. rev.; the “ditissima clade”, whose comprised species are combinated to Coenypha; the “pentacantha clade”, comprising all South-American species of Stephanopis, and finally the “altifrons clade”, considered here as Stephanopis (stricto sensu) for comprehend the type-species S. altifrons and other 15 species with Australian distribution. Sidymella also presented species emerging in distinct lineages, being attributed to the “lucida clade” the status of Sidymella (stricto sensu), since it is composed by the type species of the genus S. lucida and other Neotropical representatives. Australian species hitherto attributed to Sidymella are for now treated as dissident clades (“trapezia clade”, “hirsuta clade” and “angulata clade”), even presenting strong evidences that suggest their possible validity as new independent genera. The taxonomic review of Neotropical Sidymella species allowed the redescription of S. furcillata, S. longispina, S. lucida and S. kolpogaster and two new species to be described (S. excavata and S. marmorata). Additional taxonomic acts were also proposed: S. nigripes is considered species inquirenda while S. obscura, S. parallela e S. spinifera are put in nomina dubia. New distribution records for Sidymella in the Neotropics are presented as well as diagnoses and descriptions are updated. Thereby, the genus previously composed by 21 species, now comprises 20. Similarly, we presente a taxonomic review of Stephanopis, but in this case, focusing on the Australian representatives of the genus. In this study an identification key for males and females is provided. The type-species S. altifrons is redescribed while S. aspera, S. depressa, S. monticola, S. elongata e S. scabra are considered its junior synonyms. Males of S. altifrons, S. angulata, S. nigra, S. armata, S. fissifrons e S. longimana are described for the first time. Neotypes are proposed for S. nigra and S. barbipes, being the female of this latter originally described in this same work. Seven new species are proposed (S. arenata, S. squalida, S. flagellata, S. nana, S. spiralis, S. similis and S. carcinoides) and nine are considered nomina dubia (S. bradleyi, S. clavata, S. cristipes, S. malacostracea, S. minuta, S. ornata, S. secata and S. vilosa). The species S. thomisoides is considered species inquirenda and S. cheesmanae is transferred to Phrynarachne. New distribution records are provided and a brief comment section regarding the validity of the genus and its relationship with Sidymella and other stephanopines is presented, supporting the proposition for the possible existence of distinct groups of species in Stephanopis, which would come to be posteriorly discussed in the phylogenetic analysis.