Maintenance of Species Differences in Closely Related Tetraploid Parasitic Euphrasia (Orobanchaceae) on an Isolated Island.

Polyploidy is pervasive in angiosperm evolution and plays important roles in adaptation and speciation. However, polyploid groups are understudied due to complex sequence homology, challenging genome assembly, and taxonomic complexity. Here, we study adaptive divergence in taxonomically complex eyebrights (Euphrasia), where recent divergence, phenotypic plasticity, and hybridization blur species boundaries. We focus on three closely related tetraploid species with contrasting ecological preferences that are sympatric on Fair Isle, a small isolated island in the British Isles. Using a common garden experiment, we show a genetic component to the morphological differences present between these species. Using whole-genome sequencing and a novel k-mer approach we call "Tetmer", we demonstrate that the species are of allopolyploid origin, with a sub-genome divergence of approximately 5%. Using ∼2 million SNPs, we show sub-genome homology across species, with a very low sequence divergence characteristic of recent speciation. This genetic variation is broadly structured by species, with clear divergence of Fair Isle heathland Euphrasia micrantha, while grassland Euphrasia arctica and coastal Euphrasia foulaensis are more closely related. Overall, we show that tetraploid Euphrasia is a system of allopolyploids of postglacial species divergence, where adaptation to novel environments may be conferred by old variants rearranged into new genetic lineages.

Dermatitis herpetiformis presenting as chronic urticaria.

Childhood dermatitis herpetiformis (DH) is an immunobullous disease associated with gluten-sensitive enteropathy. This disease is rare in children and is typically characterized by intensely pruritic vesicles on the extensor surfaces. Definitive diagnosis of DH depends on the direct immunofluorescence finding of granular or fibrillar IgA deposits along the basement membrane zone of biopsied perilesional skin. We report an 11-year-old boy with an unusual presentation of DH characterized by a 7-month history of chronic urticaria-like skin lesions. He had evanescent, largely asymptomatic, urticarial wheals on his trunk, face, and extremities that were unresponsive to conventional therapy for urticaria. Skin biopsy specimen findings were consistent with DH and direct immunofluorescence of perilesional skin was diagnostic. The patient had no symptoms of gluten-sensitive enteropathy at the time of diagnosis, and his skin lesions rapidly cleared with dapsone therapy. This patient serves to highlight an unusual presentation of childhood DH and the need to consider this diagnosis when evaluating chronic urticarial lesions in children.