Taxonomic and evolutionary implications of spore ornamentation in Davalliaceae

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Abstract

Davalliaceae is a small family of derived ferns that grow epiphytic or occasionally epilithic in the tropics and subtropics of the Old World. Despite recent taxonomic and phylogenetic achievements, some aspects of its classification remain controversial. In this study, we provided new spore observations on Davalliaceae by using scanning electron microscopy. The newly generated data were integrated together with previously reported spore evidence of this group. The evolution of spore ornamentation and taxonomic implications of spore characters was optimized onto a phylogenetic tree based on plastid sequences. Verrucate colliculate spore ornamentation was identified as plesiomorphic character state within Davalliaceae. The Humata clade was characterized by the transition from verrucate colliculate to fused verrucate ornamentation. Several species complexes subject to taxonomic controversy were found to show informative variation in the spore ornamentation. In conclusion, our observations support the utility of spores as a morphological taxonomic trait in ferns, as long as the evolution of spore morphology is considered.

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