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Abstract In the last decade and a half, advances in genetic sequencing technologies have revolutionized systematics, transforming the field from studying morphological characters or a few genetic markers, to genomic datasets in the phylogenomic era. A plethora of molecular phylogenetic studies on many taxonomic groups have come about, converging on, or refuting prevailing morphology or legacy‐marker‐based hypotheses about evolutionary affinities. Spider systematics has been no exception to this transformation and the inter‐relationships of several groups have now been studied using genomic data. About 51 500 extant spider species have been described, all with a conservative body plan, but innumerable morphological and behavioural peculiarities. Inferring the spider tree of life using morphological data has been a challenging task. Molecular data have corroborated many hypotheses of higher‐level relationships, but also resulted in new groups that refute previous hypotheses. In this review, we discuss recent advances in the reconstruction of the spider tree of life and highlight areas where additional effort is needed with potential solutions. We base this review on the most comprehensive spider phylogeny to date, representing 131 of the 132 spider families. To achieve this sampling, we combined six Sanger‐based markers with newly generated and publicly available genome‐scale datasets. We find that some inferred relationships between major lineages of spiders (such as Austrochiloidea, Palpimanoidea and Synspermiata) are robust across different classes of data. However, several new hypotheses have emerged with different classes of molecular data. We identify and discuss the robust and controversial hypotheses and compile this blueprint to design future studies targeting systematic revisions of these problematic groups. We offer an evolutionary framework to explore comparative questions such as evolution of venoms, silk, webs, morphological traits and reproductive strategies. 

Abstract Spiders are unique in having a dual respiratory system with book lungs and tracheae, and most araneomorph spiders breathe simultaneously via book lungs and tracheae, or tracheae alone. The respiratory organs of spiders are diverse but relatively conserved within families. The small araneoid spiders of the symphytognathoid clade exhibit a remarkably high diversity of respiratory organs and arrangements, unparalleled by any other group of ecribellate orb weavers. In the present study, we explore and review the diversity of symphytognathoid respiratory organs. Using a phylogenetic comparative approach, we reconstruct the evolution of the respiratory system of symphytognathoids based on the most comprehensive phylogenetic frameworks to date. There are no less than 22 different respiratory system configurations in symphytognathoids. The phylogenetic reconstructions suggest that the anterior tracheal system evolved from fully developed book lungs and, conversely, reduced book lungs have originated independently at least twice from its homologous tracheal conformation. Our hypothesis suggests that structurally similar book lungs might have originated through different processes of tracheal transformation in different families. In symphytognathoids, the posterior tracheal system has either evolved into a highly branched and complex system or it is completely lost. No evident morphological or behavioral features satisfactorily explains the exceptional variation of the symphytognathoid respiratory organs. 

KiekiePolotow & Brescovit, 2018 is a Neotropical genus of Ctenidae, with most of its species occuring in Central America. In this study, we review the systematics ofKiekieand describe five new species and the unknown females ofK. barrocoloradoPolotow & Brescovit, 2018 andK. garifunaPolotow & Brescovit, 2018, and the unknown male ofK. verbenaPolotow & Brescovit, 2018. In addition, we described the female ofK. montanensewhich was wrongly assigned asK. griswoldiPolotow & Brescovit, 2018 (both species are sympatric). We provided a modified diagnosis for previously described species based on the morphology of the newly discovered species andin situphotographs of living specimens. We inferred a molecular phylogeny using four nuclear (histone H3, 28S rRNA, 18S rRNA and ITS-2) and three mitochondrial genes (cytochrome c oxidase subunit I or COI, 12S rRNA and 16S rRNA) to test the monophyly of the genus and the evolutionary relationships of its species. Lastly, we reconstruct the historical biogeography and map diversity and endemism distributional patterns of the different species. This study increased the number of known species ofKiekiefrom 13 to 18, and we describe a new genus,Eldivowhich is sister lineage ofKiekie. Most of the diversity and endemism of the genusKiekieis located in the montane ecosystems of Costa Rica followed by the lowland rainforest of the Pacific side (Limon Basin).Kiekieoriginated in the North America Tropical region, this genus started diversifying in the Late Miocene and spread to Lower Central America and South America. In that region,Kiekiecolonized independently several times the montane ecosystems corresponding to periods of uplifting of Talamanca and Central Cordilleras. 

Two new species of the genus Putaoa Hormiga and Tu, 2008 from southern China are described, Putaoa annulata n. sp. (♂♀) and Putaoa titanoverpa n. sp. (♂♀), for a total number of five described species in this genus. Detailed descriptions and illustrations of the two new species are provided. A map of collecting localities is also provided for all five Putaoa species. 

We complement and expand the existing descriptions of the Australian araneid spider Paraplectanoides crassipes Keyserling, 1886, and provide the first detailed analysis of the male palpal homologies to include examination of the expanded organ and scanning electron micrographs of the palpal sclerites. We study the placement of Paraplectanoides and the classification of the family Araneidae by combining ultraconserved elements with Sanger markers. We also added Sanger sequences of the Australian araneid genus Venomius to the molecular dataset of Scharff et al. (2020) to explore the phylogenetic placement and implications for classification of the family. We evaluate a recent proposal on the classification of the family Araneidae by Kuntner et al. (2023) in which a new family is erected for P. crassipes. Paraplectanoides is monotypic. Examination of the type material shows that Paraplectanoides kochi O. Pickard-Cambridge, 1877 is misplaced in the genus and the name is a senior synonym of the araneid Isoxya penizoides Simon, 1887 (new synonymy) that results in the new combination Isoxya kochi (O. Pickard-Cambridge, 1877). The classification of Araneidae is revised and the following nomenclatural acts are introduced: Paraplectanoididae Kuntner, Coddington, Agnarsson and Bond, 2023 is a junior synonym of Araneidae Clerck, 1757 new synonymy; phonognathines and nephilines are subfamilies of Araneidae (Subfamily Phonognathinae Simon, 1894 rank resurrected; and Subfamily Nephilinae Simon, 1894 rank resurrected). The results of our analyses corroborate the sister group relationship between Paraplectanoides and the araneid subfamily Nephilinae. Venomius is sister to the Nephilinae + Paraplectanoides clade. The placement of the oarcine araneids and Venomius renders the family Araneidae non-monophyletic if this were to be circumscribed as in Kuntner et al. (2023). In light of the paucity of data that the latter study presents, and in absence of a robust, stable and more densely sampled phylogenetic analysis of Araneidae, the changes and definitions introduced by that classification are premature and could lead to a large number of new families for what once were araneid species if the maximum-crown-clade family definitions were to be used. Consequently, we argue for restoring the familial and subfamilial classification of Araneidae of Dimitrov et al. (2017), Scharff et al. (2020) and Kallal et al. (2020). 

Abstract A prominent question in animal research is how the evolution of morphology and ecology interacts in the generation of phenotypic diversity. Spiders are some of the most abundant arthropod predators in terrestrial ecosystems and exhibit a diversity of foraging styles. It remains unclear how spider body size and proportions relate to foraging style, and if the use of webs as prey capture devices correlates with changes in body characteristics. Here, we present the most extensive data set to date of morphometric and ecological traits in spiders. We used this data set to estimate the change in spider body sizes and shapes over deep time and to test if and how spider phenotypes are correlated with their behavioral ecology. We found that phylogenetic variation of most traits best fitted an Ornstein–Uhlenbeck model, which is a model of stabilizing selection. A prominent exception was body length, whose evolutionary dynamics were best explained with a Brownian Motion (free trait diffusion) model. This was most expressed in the araneoid clade (ecribellate orb-weaving spiders and allies) that showed bimodal trends toward either miniaturization or gigantism. Only few traits differed significantly between ecological guilds, most prominently leg length and thickness, and although a multivariate framework found general differences in traits among ecological guilds, it was not possible to unequivocally associate a set of morphometric traits with the relative ecological mode. Long, thin legs have often evolved with aerial webs and a hanging (suspended) locomotion style, but this trend is not general. Eye size and fang length did not differ between ecological guilds, rejecting the hypothesis that webs reduce the need for visual cue recognition and prey immobilization. For the inference of the ecology of species with unknown behaviors, we propose not to use morphometric traits, but rather consult (micro-)morphological characters, such as the presence of certain podal structures. These results suggest that, in contrast to insects, the evolution of body proportions in spiders is unusually stabilized and ecological adaptations are dominantly realized by behavioral traits and extended phenotypes in this group of predators. This work demonstrates the power of combining recent advances in phylogenomics with trait-based approaches to better understand global functional diversity patterns through space and time. [Animal architecture; Arachnida; Araneae; extended phenotype; functional traits; macroevolution; stabilizing selection.]