The Asplenium normale complex contains the widespread A. normale and several geographically restricted species: A. boreale, A. hobdyi, A. kiangsuense, A. oligophlebium and A. shimurae. The taxonomy of this group is unclear with some entities treated infraspecifically or as synonyms. Furthermore, the existence of diploids and tetraploids in this species complex is suggestive of reticulate evolution.
A phylogenetic study of this fern group is urgently needed to achieve a natural classification of the complex. Dr. CHANG Yanfen of Xishuangbanna Tropical Botanical Garden (XTBG) and her teachers conducted a study that was aimed to identify the number of lineages that form the A. normale complex and clarify the relationships among those lineages.
Sampling covered the distribution range of the whole complex, including China, East Africa (Tanzania), Madagascar, the Pacific Islands (Hawai‘i), Japan, Indochina (Vietnam), and Malesia (Malay Peninsula). The genetic diversity and phylogeny of the complex were studied using four regions of the maternally inherited chloroplast genome (trnL-trnF, rps4-trnS, trnG-trnR, rbcL). In order to detect reticulation in the A. normale complex, the researchers employed a biparentally inherited marker, the single-copy nuclear gene pgiC.
Their results suggested that the A. normale complex consisted of six distinct species. Traditional morphology-based taxonomy poorly represented the diversity in this complex. In light of their phylogenetic results, further analyses of morphology may recover currently unrecognized species characters.
Their study revealed that the presence and location of frond buds was a potentially informative character in the A. normale complex.
The study entitled “Species diversity and reticulate evolution in the Asplenium normale complex (Aspleniaceae) in China and adjacent areas” has been published online in Taxon.