Cryptic species are present throughout the tree of life. They are especially prevalent in ferns, because of processes such hybridization, polyploidy, and reticulate evolution. In addition, the morphologically simple body plan of ferns limits phenotypic variation and makes it difficult to detect cryptic species in ferns without molecular work. The model fern genus Ceratopteris has long been suspected to harbor cryptic diversity, specifically in the highly polymorphic C. thalictroides. Yet no studies have included samples from throughout its pan-tropical range or utilized genomic sequencing, making it difficult to assess the full extent of cryptic variation within this genus. Here, we present the first multilocus phylogeny of the genus using reduced representation genomic sequencing (RADseq).
Results/Conclusions
The flexibility of RADseq data allow us to utilize a three-pronged approach to decipher cryptic species within Ceratopteris: we examine population structure, phylogenetic relationships, and ploidy level variation. We recover similar species relationships found in previous studies, find support for a named cryptic species as genetically distinct, and identify a novel putative species from within C. thalictroides sensu latu in Central and South America. These insights also help us understand the processes of diversification within the genus.