Biodiversity and phylogeny of Ammotheidae (Arthropoda: Pycnogonida)

Abstract

D N A L i b r a r y o f L i f e , r e s e a r c h a r t i c l eurn:lsid:zoobank

Phylogenomic resolution of sea spider diversification through integration of multiple data classes

“…Future work should prioritize the gap segmentation genes of sea spiders, especially those functionally linked to gap segmentation phenotypes in chelicerate model species [41][42][43]. rRNA in such studies [12,44]. N. tapetis may therefore constitute a rogue taxon, an inference corroborated by its variable placement across data partitions generated in this study (electronic supplementary material, figure S3).…”

“…Previous efforts to decipher the higher-level relationships of sea spiders have been hindered by the omission of key lineages [11,12], inaccessibility of many families for phylotranscriptomic approaches [18,21,22], limited informativeness of legacy Sangersequenced markers [5,[11][12], compositional bias of mitochondrial genes [11], ineffectiveness of mitogenomes for resolving deep relationships of Chelicerata [13,14], and the potential for gut or epibiont contamination [5]. Here, we surmounted these challenges by integrating multiple data classes and using a target capture approach optimized for sea spider (or chelicerate) genomic sequence.…”

“…Phylogenetic investigations of sea spider relationships based on anatomical data [6] or combined analyses of morphology and molecular sequence data [5] suggested instead that reduction of appendages occurred independently across the phylogeny, but the tree topologies were highly discordant between data partitions. Subsequent approaches to infer sea spider relationships under model-based approaches [10][11][12] were repeatedly frustrated by the instability of basal relationships, which are attributable to two possible causes. First, efforts to infer the phylogeny of Pycnogonida have been based on a small number of loci (one to six genes; figure 2).…”

“…First, efforts to infer the phylogeny of Pycnogonida have been based on a small number of loci (one to six genes; figure 2). These datasets consisted largely of genes that evolve at high rates (e.g., mitochondrial genes cytochrome c oxidase subunit I and 16S rRNA) or those that evolve at low rates (e.g., nuclear ribosomal genes) [5,[10][11][12]. Separately, mitochondrial genes of sea spiders exhibit well-known lineage-specific compositional biases [11].…”

“…Concordantly, datasets based on fast-evolving mitochondrial genes have exhibited limited utility in resolving Paleozoic relationships of various invertebrate groups, and the placement of sea spiders within Chelicerata in particular [13,14]. Second, previous phylogenetic studies have omitted or poorly sampled two small-bodied families of sea spiders, Austrodecidae and Rhynchothoracidae [11,12]. Austrodecidae (figure 1g; approximately 60 species in two genera) are distinguished from other sea spiders by the annulation of the proboscis.…”