Taxonomy and breeding systems of the 'Drosera peltata' complex (Droseraceae)

Abstract

Literature, and personal observations, suggested that the 'Drosera peltata' complex consisted of up to 12 species in Australia, Asia and Africa. The taxonomy of the complex was controversial, making it ideal for testing species limits, and the morphological, genetic, phylogenetic and biological species concepts. Species limits of 10 species and 7 putative taxonomic entities were tested by phenetic analysis, using clustering and ordination of 243 herbarium samples and 294 characters. Type specimens were included to consider the application of names. According to morphology, two species were recognised: 'D. bicolor' and 'D. peltata'. Phylogenetic analysis using nuclear (ITS 1, ITS2 and 5.8 S), and the chloroplast 'trnL' sequences revealed that the 'D. peltata' complex is non-monophyletic. 'Drosera peltata' "Western Australian Form" grouped apart from the remainder of the complex, indicating that it merits species status under the phylogenetic species concept, and that it is a cryptic species because it lacks obvious morphological autapomorphy. Experimental pollinations were conducted within and between entities from south-eastern Australia. Fertility was measured as percent seed set. Cross-pollinations between plants of 'D. peltata' "Black Mountain, A.C.T." from different populations showed a decline in fertility with increasing geographic separation, which indicates outbreeding depression. Self- and cross-pollinations within entities and between entities were similarly highly fertile. Flowers exhibited a delayed autonomous self-pollination mechanism, which would provide reproductive assurance. Stanlens inflexed bringing the anthers into contact with the stigmatic surfaces at the end of floral life. This highly selfing breeding system in the 'D. peltata' complex would genetically isolate populations and entities within this complex, which would facilitate speciation. Synthesis of my morphological, molecular and breeding system data indicate that the 'D. peltata' complex consists of three species: the narrow endemic 'D. hieolor', the widespread and highly morphologically variable 'D. peltata', and an undescribed cryptic species: 'D. peltata' "Western Australian Form".