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Abstract The ecological and phenotypic diversity observed in oceanic island radiations presents an evolutionary paradox: a high level of genetic variation is typically required for diversification, but species colonizing a new island commonly suffer from founder effects. This reduction in population size leads to lower genetic diversity, which ultimately results in a reduction in the efficiency of natural selection. What then is the source of genetic variation which acts as the raw material for ecological and phenotypic diversification in oceanic archipelagos? Transposable elements (TEs) are mobile genetic elements that have been linked to the generation of genetic diversity, and evidence suggests that TE activity and accumulation along the genome can result from reductions in population size. Here, we use the Hawaiian spiny-leg spider radiation (Tetragnatha) to test whether TE accumulation increases due to demographic processes associated with island colonization. We sequenced and quantified TEs in 23 individuals representing 16 species from the spiny-leg radiation and four individuals from its sister radiation, the Hawaiian web-building Tetragnatha. Our results show that founder effects resulting from colonization of new islands have not resulted in TE accumulation over evolutionary time. Specifically, we found no evidence for an increase in abundance of specific TE superfamilies, nor an accumulation of ‘young TEs’ in lineages which have recently colonized a new island or are present in islands with active volcanoes. We also found that the DNA/hAT transposon superfamily is by far the most abundant TE superfamily in the Tetragnatha radiation. This work shows that there is no clear trend of increasing TE abundance for the spiny-leg radiation across the archipelago chronosequence, and TE accumulation is not affected by population oscillations associated with island colonization events. Therefore, despite their known role in the generation of genetic diversity, TE activity does not appear to be the mechanism explaining the evolutionary paradox of insular diversification in the Tetragnatha spiny-leg radiation. 

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). 

We address the phylogenetic relationships of pimoid spiders (Pimoidae) using a standard target-gene approach with an extensive taxonomic sample, which includes representatives of the four currently recognized pimoid genera, 26 linyphiid genera, a sample of Physoglenidae, Cyatholipidae and one Tetragnathidae species. We test the monophyly of Pimoidae and Linyphiidae and explore the biogeographic history of the group. Nanoa Hormiga, Buckle and Scharff, 2005 and Pimoa Chamberlin & Ivie, 1943 form a clade which is the sister group of a lineage that includes all Linyphiidae, Weintrauboa Hormiga, 2003 and Putaoa Hormiga and Tu, 2008. Weintrauboa, Putaoa, Pecado and Stemonyphantes form a clade (Stemonyphantinae) sister to all remaining linyphiids. We use the resulting optimal molecular phylogenetic tree to assess hypotheses on the male palp sclerite homologies of pimoids and linyphiids. Pimoidae is redelimited to only include Pimoa and Nanoa. We formalize the transfer from Pimoidae of the genera Weintrauboa and Putaoa to Linyphiidae, re-circumscribe the linyphiid subfamily Stemonyphantinae, and offer revised morphological diagnoses for Pimoidae and Linyphiidae. 

Abstract Spiders (Araneae) have a diverse spectrum of morphologies, behaviors, and physiologies. Attempts to understand the genomic-basis of this diversity are often hindered by their large, heterozygous, and AT-rich genomes with high repeat content resulting in highly fragmented, poor-quality assemblies. As a result, the key attributes of spider genomes, including gene family evolution, repeat content, and gene function, remain poorly understood. Here, we used Illumina and Dovetail Chicago technologies to sequence the genome of the long-jawed spider Tetragnatha kauaiensis, producing an assembly distributed along 3,925 scaffolds with an N50 of ∼2 Mb. Using comparative genomics tools, we explore genome evolution across available spider assemblies. Our findings suggest that the previously reported and vast genome size variation in spiders is linked to the different representation and number of transposable elements. Using statistical tools to uncover gene-family level evolution, we find expansions associated with the sensory perception of taste, immunity, and metabolism. In addition, we report strikingly different histories of chemosensory, venom, and silk gene families, with the first two evolving much earlier, affected by the ancestral whole genome duplication in Arachnopulmonata (∼450 Ma) and exhibiting higher numbers. Together, our findings reveal that spider genomes are highly variable and that genomic novelty may have been driven by the burst of an ancient whole genome duplication, followed by gene family and transposable element expansion. 

Abstract The repeated evolution of phenotypes provides clear evidence for the role of natural selection in driving evolutionary change. However, the evolutionary origin of repeated phenotypes can be difficult to disentangle as it can arise from a combination of factors such as gene flow, shared ancestral polymorphisms or mutation. Here, we investigate the presence of these evolutionary processes in the Hawaiian spiny‐legTetragnathaadaptive radiation, which includes four microhabitat‐specialists or ecomorphs, with different body pigmentation and size (Green, Large Brown, Maroon, and Small Brown). We investigated the evolutionary history of this radiation using 76 newly generated low‐coverage, whole‐genome resequenced samples, along with phylogenetic and population genomic tools. Considering the Green ecomorph as the ancestral state, our results suggest that the Green ecomorph likely re‐evolved once, the Large Brown and Maroon ecomorphs evolved twice and the Small Brown evolved three times. We found that the evolution of the Maroon and Small Brown ecomorphs likely involved ancestral hybridization events, while the Green and Large Brown ecomorphs likely evolved through novel mutations, despite a high rate of incomplete lineage sorting in the dataset. Our findings demonstrate that the repeated evolution of ecomorphs in the Hawaiian spiny‐legTetragnathais influenced by multiple evolutionary processes.