Reticulate evolution in the Asplenium anogrammoides complex from Korea

For Asplenium sarelii Hook. (Dol-dam-go-sa-ri in Korean), recognized in Korea, it has been proposed that some populations of the species should be verified as A. anogrammoides Christ (2n = 4x = 144 based on its chromosome number counted from Japanese populations). Asplenium anogrammoides has been hypothesized as a polyploid species derived from a hybrid between A. sarelii (2n = 2x = 72) and A. tenuicaule Hayata (2n = 2x = 72) based on its chromosome number counted from Japanese populations. To clarify the identity of A. anogrammoides in Korea, the morphological, cytological, and molecular characters were examined. Morphologically variable individuals of A. anogrammoides were found in sympatric regions with A. tenuicaule and A. pekinense. We investigated ploidy levels using flow cytometry data as well as the chloroplast DNA sequence data of two regions (rbcL; rps4-trnS and rps4-trnS intergenic spacer) to clarify the taxonomic status of this species. The chloroplast DNA (rbcL and rps4–trnS) indicated monophyly of the A. anogrammoides complex, although there were a few polyphyletic phenomena within the populations. With regard to the genome size data (flow cytometry) and chromosomes numbers, the A. anogrammoides complex from Korea contains mostly hexapodids, rarely tetraploids, and we cannot find diploid individuals. Based on these results, we hypothesize that the A. anogrammoides complex in Korea is mostly fertile hexaploids that arose due to autotetraploidy from A. × huawuense (3x), which formed between A. sarelii and A. anogrammoides. In addition, it is postulated that there are sp1 (6x), sp2 (6x), and sp3 (6x) due to the sharing of morphological characters among A. sarelii, A. tenuicaule, A. anogrammoides, and A. pekinense.