Cryptic Diversity Within The African Aquatic Plant Ottelia Ulvifolia(Hydrocharitaceae)Revealed By Population Genetic And Phylogenetic Analyses

Species are the functional units of biodiversity,and detailed species delimitation is vital for impartial biodiversity estimation.While there is no perfect species concept,it is generally agreed that species should be delimited as evolutionarily distinct lineages,usually manifested by important morphological,genetic,or niche differentiation.Currently,the majority of species are still identified based on morphological variances alone,and many genetically different but morphologically similar species remain unnoticed.These cryptic species make up a great proportion of hidden diversity.Identification of cryptic species hidden in traditionally established species may lead to the emergence of new geographical patterns and change the understanding of how biodiversity is geologically distributed.The existence of cryptic species is related to both internal properties of organisms and with external environmental conditions thus making the detection of cryptic species thought-provoking.Fixing boundaries among species is puzzling yet required in biodiversity conservation.Similar species are occasionally difficult to distinguish even after cross-examination by eminent taxonomists.However,with the invention of molecular techniques in species delimitation,this concealed diversity has received much attention over the recent years.Therefore,for better conservation and deciphering macroevolution and ecology of plants,revealing of cryptic diversity is necessary.Ottelia,a typical example of aquatic plants,shows great morphological variation and the existence of cryptic diversity makes its taxonomic classification problematic.Past studies have revealed the presence of cryptic Ottelia species in Asia,but very little is known about the molecular systematics of this genus in Africa,a center of species diversity of Ottelia.In this study,Ottelia ulvifolia,an endemic species of tropical Africa,from Zambia and Cameroon was sampled.Six chloroplast DNA regions,nrITS and six polymorphic microsatellite markers were used to estimate the molecular diversity and population genetic structure in O.ulvifolia.The phylogenetic inference,STACEY and STRUCTURE analyses supported at least three clusters within O.ulvifolia,each representing unique flower types(i.e.,bisexual yellow flower,unisexual yellow flower and bisexual white flower types).Although abundant genetic variation(> 50%)was observed within the populations,excessive anthropogenic activities may result in genetic drift and bottlenecks.Here,three cryptic species of O.ulvifolia complex are defined,and insights are provided into the taxonomy of Ottelia using the phylogenetic species concept.