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The taxonomy of subcosmopolitan Urtica dioica L. s.l. is problematic. Recent floras recognize Urtica dioica as a subcosmopolitan species ranging throughout the entire holarctic region and also South Africa and New Zealand. Numerous infraspecific taxa have been proposed, especially in western Eurasia. There is only weak character differentiation, with floral and fruit morphology largely uniform, details of leaf morphology and indumentum are therefore primarily used for species delimitation, together with some characters of gender distribution and growth habit. The present study addresses the enigmatic relationships of the infraspecific taxa in Urtica dioica with a special emphasis on the monoecious, American representatives of Urtica dioica s.l. The study is based on extensive field and herbarium studies, molecular data and the experimental cultivation of all relevant forms. Infraspecific taxa currently assigned to U. dioica are retrieved mainly on two separate clades, one comprising the predominantly polygamous western Eurasian and African taxa (all subspecies and varieties sampled), the other comprising the monoecious American taxa. Monoecious American representatives of “Urtica dioica” and closely allied taxa (U. aquatica, U. mollis) are retrieved as a monophyletic group sister to a clade with East Asian and Australasian species, this clade is then retrieved as sister to the western and central Eurasian and African taxa of U. dioica. We therefore advocate the removal of the American representatives of this group from Urtica dioica and their placement as infraspecific taxa under Urtica gracilis. The following new names are consequently proposed: Urtica gracilis subsp. gracilis (for Urtica dioica subsp. gracilis), Urtica gracilis subsp. holosericea, comb. nov. (for Urtica dioica subsp. holosericea), Urtica gracilis subsp. aquatica, comb. & stat. nov. (for Urtica aquatica), Urtica gracilis subsp. mollis, comb. & stat. nov. (for Urtica mollis). Additionally, we describe a new subspecies from Peru under the name Urtica gracilis subsp. incaica. The literature report of Urtica gracilis (dioica subsp. gracilis) as an introduced weed in New Zealand is shown to be erroneous – the corresponding specimens belong to Australian Urtica incisa. Based on gross morphology close affinities have been proposed between a range of Australasian, Asian, North American and European infraspecific taxa, all of these can be shown to be erroneous.

Urtica dioica L. in its wider sense is reported from nearly all temperate zones of the world, from throughout Eurasia, from North America and South America, from S Africa and New Zealand. In Europe, over 70 infrasubspecific names referable to the widespread and often weedy U. dioica subsp. dioica have been used in one form or another; over 40 of them are formally described. Many of these names are invalid and/or superfluous. However, several identifiable morphotypes can be found, which are stable in cultivation and usually occur in several different regions of Europe and/or are characterized by some type of habitat preference. These morphotypes in their most characteristic expression are quite well differentiated, but are connected by a continuous series of intermediates in nature. As a working hypothesis we here propose the tentative recognition of the following five morphotypes: U. dioica subsp. dioica var. dioica, -var. hispida, -var. sarmatica, -var. holosericea, and -var. glabrata. A characterization of each morphotype and corresponding synonyms are presented here based on extensive field studies, literature and herbarium studies and cultivation of material. Lecto-and neotypes are designated where necessary for some of the more important names.

Autogamous species are usually distinguishable from xenogamous relatives by smaller flowers, fewer or even no floral rewards and lower pollen-ovule (P/O) ratios. Many Rhipsalis spp. are small flowered, selfing and include the most widespread species in Cactaceae. However, Rhipsalis also includes a large number of narrowly endemic species and is most diverse in the Atlantic rainforests of Brazil. To investigate the evolution of floral function and the correlation between floral function and range size, we analysed display size, floral reward and P/O ratios of Rhipsalis and its closest relatives, reconstructed ancestral traits and related these patterns to the distributions and range sizes of the species. Display size and sugar amount are reduced in subgenera Goniorhipsalis and Rhipsalis and secondarily increased in Phyllarthrorhipsalis, whereas the P/O ratio is decreased in subgenera Rhipsalis and Phyllarthrorhipsalis. We interpret this pattern as a switch from a predominantly xenogamous to an autogamous reproductive system, followed by a return to a predominantly xenogamous system. None of the floral parameters shows significant correlations with range size, except for display size. Nevertheless, those species with the smallest flowers, lowest sugar amounts per flower and lowest P/O ratios occur either outside southeastern Brazil and/or have comparatively large distribution ranges. Almost all Rhipsalis spp. occurring outside the Atlantic rainforests are restricted to the clade formed by subgenera Rhipsalis and Phyllarthrorhipsalis. Thus, we believe that the evolution of an autogamous reproduction system enabled this lineage of Rhipsalis to diversify and spread in the Atlantic rainforests, in the rest of the Neotropics and even spread to the Old World, where it is the only member of the family.

Urtica L. (Urticaceae) is generally reported as a genus of monoecious and dioecious taxa. However, the gender information found in the literature does not at all reflect the actual diversity of gender patterns in Urtica. Dioecy appears to be truly absent from Urtica, but otherwise there has been a major diversification in the geometry of gender and no comparable patterns exist in other plant groups. Thus, we here define technical terms for all unique architectural types of monoecy found in Urtica and closely related genera and reconstruct the ancestral gender states in a Bayesian framework. Our studies are based on a near‐comprehensive sampling, including 61 of the 63 Urtica species recognized. We report polygamy, two types of gynodioecy and five different architectural types of monoecy. A total of 15 switches appear to have taken place within the genus. Although gender characteristics have diversified strongly, they are relatively conserved within clades. Monoecy is the predominant sexual system within Urtica and specifically basiandrous monoecy (i.e. basal inflorescence branches of each individual male only, apical branches female) is the most widespread type, reported for 11 different clades. In particular, it characterizes the basally branching pilulifera‐clade and the sister genus Zhengyia, and may thus represent the plesiomorphic condition for Urtica. Gender distribution and gross morphology appear to evolve largely independently from each other and gender distribution is largely independent of growth habit. However, polygamous taxa are most common amongst rhizomatous perennials (one‐third of the taxa).

Taxon differentiation in Urtica from Australia and New Zealand initially appears to be uncomplicated, with taxa being easy to distinguish. However, a revision of the type material, more recent collections and a comparison of Australian and New Zealand material shows that three of the names are misapplied. Urtica gracilis (as U. dioica subsp. gracilis, North America) has been reported as introduced to New Zealand, but molecular data retrieve the corresponding specimens with the other NZ-species and we argue that they belong to the polygamous Australian species Urtica incisa. A critical revision of the protologues and type collections reveals that the names Urtica incisa, originally described from mainland Australia, and U. incisa var. linearifolia from Tasmania, have been misapplied to New Zealand taxa. Both New Zealand “Urtica linearifolia” and “U. incisa” represent unnamed taxa and are here formally described as Urtica perconfusa and Urtica sykesii, respectively. Urtica perconfusa corresponds to what is erroneously known as U. linearifolia. Urtica sykesii is an overlooked species, erroneously interpreted as U. incisa in New Zealand. It may be differentiated from U. incisa Poir. by its smaller, deltoid leaf lamina with a truncate to subcordate base (versus truncate to cuneate), fewer leaf teeth (9–12 on each side rather than 14–20 in U. incisa) and smaller plant size (20–60 cm rather than 60–200 cm in U. incisa). We found evidence for the presence of true introduced U. dioica subsp. dioica in New Zealand, but not for U. gracilis. Rather, New Zealand specimens assigned to the putatively introduced northern hemisphere U. gracilis belong to U. incisa as described from Australia. Typifications for the species treated here are provided, including an updated key to the Australian and New Zealand taxa. There are thus six native species of Urtica in New Zealand, four of them endemic, and two also indigenous in Australia.

Amborella trichopoda Baill., the most ancestral angiosperm, has been successfully cultivated in the Botanic Gardens of the University of Bonn in Germany (BG Bonn) for more than a decade. The distribution of this plant – limited to the South Pacific island of New Caledonia – and its cultivation has so far only been achieved in a few botanic gardens. This paper provides details about the cultivation and propagation of Amborella, and information on its cultivation in botanic gardens around the world. The authors propose that the collections of this plant in botanic gardens could be used to establish ex situ conservation collections.

Urtica L. (Urticaceae) is a subcosmopolitan genus common throughout temperate Asia. Species delimitation is very difficult and the present study investigates a group of taxa associated with Urtica fissa from East-Southeast Asia and based mainly on herbarium collections, including most of the type specimens and cultivated plants. Species limits especially of U. mairei, U. fissa and U. himalayensis have been consistently confused in both herbaria and floristic treatments. As part of a taxonomic revision we produced a molecular phylogeny of the group based on ITS1-5.8S-ITS2, psbA–trnH, trnL–trnF and trnS–trnG markers. Our revision recovers a total of five species and two subspecies: U. fissa E.Pritz. ex Diels, U. grandidentata Miq. subsp. grandidentata, U. grandidentata Miq. subsp. lombok K.Becker & Weigend, U. himalayensis Kunth & C.D.Boché, U. mairei Lév. and U. parviflora Roxb. We provide type information, diagnostic characters, a key to species identification, species conservation assessments and a list of exsiccatae for each taxon.