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Abstract Genome-wide information has so far been unavailable for ribbon worms of the clade Hoplonemertea, the most species-rich class within the phylum Nemertea. While species within Pilidiophora, the sister clade of Hoplonemertea, possess a pilidium larval stage and lack stylets on their proboscis, Hoplonemertea species have a planuliform larva and are armed with stylets employed for the injection of toxins into their prey. To further compare these developmental, physiological, and behavioral differences from a genomic perspective, the availability of a reference genome for a Hoplonemertea species is crucial. Such data will be highly useful for future investigations toward a better understanding of molecular ecology, venom evolution, and regeneration not only in Nemertea but also in other marine invertebrate phyla. To this end, we herein present the annotated chromosome-level genome assembly for Emplectonema gracile (Nemertea; Hoplonemertea; Monostilifera; Emplectonematidae), an easily collected nemertean well suited for laboratory experimentation. The genome has an assembly size of 157.9 Mb. Hi-C scaffolding yielded chromosome-level scaffolds, with a scaffold N50 of 10.0 Mb and a score of 95.1% for complete BUSCO genes found as a single copy. Annotation predicted 20,684 protein-coding genes. The high-quality reference genome reaches an Earth BioGenome standard level of 7.C.Q50. 

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.