Cornelia Klak

Unmatched tempo of evolution in Southern African semi-desert ice plants

The Succulent Karoo is an arid region, situated along the west coast of southern Africa. Floristically this region is part of the Greater Cape Flora and is considered one of the Earths 25 biodiversity hotspots. Of about 5,000 species occurring in this region, more than 40% are endemic. Aizoaceae (ice plants) dominate the Succulent Karoo both in terms of species numbers (1,750 species in 127 genera) and density of coverage. Here we show that a well-supported clade within the Aizoaceae, representing 1,563 species almost exclusively endemic to southern Africa, has diversified very recently and very rapidly. The estimated age for this radiation lies between 3.8 and 8.7 million years (Myr) ago, yielding a per-lineage diversification rate of 0.77–1.75 per million years. Both the number of species involved and the tempo of evolution far surpass those of any previously postulated continental or island plant radiation. Diversification of the group is closely associated with the origin of several morphological features and one anatomical feature. Because species-poor clades lacking these features occur over a very similar distribution area, we propose that these characteristics are key innovations that facilitated this radiation.

A phylogeny and new classification for Mesembryanthemoideae (Aizoaceae)

Guatteria (Annonaceae) is with ca. 265 species one of the largest genera of Neotropical trees together with Inga and Ocotea. Use of Guatteria in evolutionary studies has been hampered by taxonomic problems caused by lack of morphological variability in the genus. This study focuses on molecular phylogenetic relationships within Guatteria and its satellites Guatteriopsis, Guatteriella and Heteropetalum, and implications of these relationships for classification and character evolution. Results show that Guatteriopsis, Guatteriella and Heteropetalum should be merged with Guatteria. Heteropetalum may be recognized at subgeneric level because of its aberrant morphology and Guatteriopsis and Guatteriella might be given sectional status. Most of the currently recognised sections in Guatteria are probably non-monophyletic. A completely new infrageneric classification of Guatteria would be premature, however, due to the lack of molecular and morphological synapomorphies to define the sections. Synapomorphies defining Guatteria s.str. probably evolved after divergence of several early branching lineages

A Molecular Systematic Study of the Lampranthus Group (Aizoaceae) Based on the Chloroplast TrnL -trnF and Nuclear ITS and 5S NTS Sequence Data

Abstract The phylogenetic position of the Lampranthus group (Ruschioideae, Aizoaceae), with particular emphasis on the large genus Lampranthus, was studied using DNA sequences from the trnL-trnF region of the chloroplast genome, the nuclear ribosomal internal transcribed spacer (ITS) region and the 5S non-transcribed spacer (NTS). Phylogenies of 59 species in 29 genera of succulent Aizoaceae, including two species from subfamily Mesembryanthemoideae, are presented. Due to an inadequate number of informative sites within the Ruschioideae (31 for trnL-trnF; 49 for ITS), the trnL-trnF and ITS regions are found to be unsuitable for phylogenetic investigations at the specific and generic level. The 5S spacer proves useful at the generic level, but fails to reveal well-supported phylogenies above the generic level. Combined analyses of all three gene regions show that Lampranthus N.E.Br. in its present circumscription is not monophyletic. A “core” of species of Lampranthus is well supported with numerous species of Lampranthus more closely related to other genera. At a higher taxonomic level, the data also do not support a monophyletic Lampranthus group. Circumscription of informal groups within the Ruschioideae, including the Lampranthus group, has mainly been based on the shared presence of a particular type of fruit. Fruits of the Lampranthus group are characterized by long, diverging expanding keels, broad valve wings and the absence of a closing body. The present data implies that this fruit type is homoplasious. Communicating Editor: Alan T. Whittemore

How succulent leaves of Aizoaceae avoid mesophyll conductance limitations of photosynthesis and survive drought

In several taxa, increasing leaf succulence has been associated with decreasing mesophyll conductance (g M) and an increasing dependence on Crassulacean acid metabolism (CAM). However, in succulent Aizoaceae, the photosynthetic tissues are adjacent to the leaf surfaces with an internal achlorophyllous hydrenchyma. It was hypothesized that this arrangement increases g M, obviating a strong dependence on CAM, while the hydrenchyma stores water and nutrients, both of which would only be sporadically available in highly episodic environments. These predictions were tested with species from the Aizoaceae with a 5-fold variation in leaf succulence. It was shown that g M values, derived from the response of photosynthesis to intercellular CO2 concentration (A:C i), were independent of succulence, and that foliar photosynthate δ13C values were typical of C3, but not CAM photosynthesis. Under water stress, the degree of leaf succulence was positively correlated with an increasing ability to buffer photosynthetic capacity over several hours and to maintain light reaction integrity over several days. This was associated with decreased rates of water loss, rather than tolerance of lower leaf water contents. Additionally, the hydrenchyma contained ~26% of the leaf nitrogen content, possibly providing a nutrient reservoir. Thus the intermittent use of C3 photosynthesis interspersed with periods of no positive carbon assimilation is an alternative strategy to CAM for succulent taxa (Crassulaceae and Aizoaceae) which occur sympatrically in the Cape Floristic Region of South Africa.

Recent radiation of Brachystelma and Ceropegia (Apocynaceae) across the Old World against a background of climatic change.

The genera Brachystelma Sims and Ceropegia L. of the Ceropegieae (Apocynaceae-Asclepiadoideae) consist of ±320 species of geophytes and slender climbers with a tendency to stem-succulence in Ceropegia. They occur in and around the semi-arid, mainly tropical parts of the Old World. For 146 species (around half of the total) from most of the geographic range of the genera, we analysed data from two nuclear and five plastid regions. The evolution of Ceropegia is very complex, with at least 13 mostly well-supported lineages, one of which is sister to the ±350 species of stapeliads. Species of Brachystelma have evolved at least four times, with most of them nested within two separate major lineages. So, neither Brachystelma nor Ceropegia is monophyletic. We recover a broad trend, in two separate major lineages, from slender climbers to small, geophytic herbs. Several clades are recovered in which all species possess an underground tuber. Small, erect, non-climbing, geophytic species of Ceropegia with a tuber are nested among species of Brachystelma. Consequently, the distinctive tubular flowers used to define Ceropegia do not reflect relationships. This re-iterates the great floral plasticity in the Ceropegieae, already established for the stapeliads. Both major lineages exhibit a trend from tubular flowers with faint, often fruity odours, pollinated by very small Dipteran flies, to flatter flowers often with a bad odour, pollinated by larger flies. Most of the diversity in Brachystelma and Ceropegia is recent and arose within the last 3my against a background of increased aridification or extreme climatic variability during the Pliocene. In the ingroup, diversity is highest in Southern Africa, followed by Tropical East Africa and other arid parts of Africa, the Arabian Peninsula and India. Many disjunctions are revealed and these are best explained by recent, long distance dispersal. In Africa, the diversity arises from the presence of many different lineages over wide areas but there is also evidence of closely related species growing together with different pollinators.

Evolution of the stapeliads (Apocynaceae–Asclepiadoideae) – repeated major radiation across Africa in an Old World group

The stapeliads of the Ceropegieae (Apocynaceae-Asclepiadoideae), are approximately 340 species of stem-succulents placed in around 30 genera, found in semi-arid parts of the Old World. Here we sampled 192 species (i.e. nearly two thirds of the total) from across the full geographic range of the group and analysed data from the two nuclear regions (nuclear ribosomal ITS and ncpGS) and five plastid regions (psbA-trnH intergenic spacer, rps16 intron, trnL-trnF intergenic spacer, trnS-trnG intergenic region and the non-coding rpl32-trnL region). We find that the stapeliads radiated first in the northern hemisphere from Africa to southern Europe and Myanmar. This radiation subtends a grade of minor clades in the south-western corner of the African continent. These were followed by a single clade containing major radiation back across Africa from South Africa to tropical Arabia (but no further east than Dhofar, Oman), which includes also a single early spread into Madagascar. We establish the monophyly of many of the genera, such as Echidnopsis Hook.f., Hoodia Hook., Huernia R. Br., Piaranthus R. Br., Rhytidocaulon P.R.O. Bally and Tridentea Haw., but find that Duvalia Haw., Orbea Haw., Stapelia L. and Tromotriche Haw. are polyphyletic. We show that in certain vegetative features, there is broad cohesion across clades. Florally, on the other hand, the stapeliads exhibit considerable plasticity and we are able to show that very differently shaped flowers as well as large and small flowers evolved repeatedly among closely related species.

New combinations, a new genus and five new species in the Aizoaceae

Summary: A detailed study of Lampranthus has shown that several of its species are more closely related to other taxa within the Aizoaceae than they are to Lampranthus. Here some of these anomalous species are transferred to the genera Esterhuysenia, Oscularia, Antimima, Erepsia and Ruschia. A new genus, Phiambolia Klak, is erected to accommodate a group of taxa which cannot be placed in any of the existing genera. The appropriate new combinations are made. In addition, the new species Phiambolia mentiens Klak, Brownanthus lignescens Klak, Acrodon deminutus Klak, Lampranthus procumbens Klak and Drosanthemum quadratum Klak are described.

Duplication of the Asymmetric Leaves1/Rough Sheath 2/Phantastica (ARP) gene precedes the explosive radiation of the Ruschioideae.

The Mesembryanthemoideae and Ruschioideae subfamilies are a major component of the Greater Cape Floristic Region in southern Africa. The Ruschioideae show an astonishing diversity of leaf shape and growth forms. Although 1,585 species are recognised within the morphologically diverse Ruschioideae, these species show minimal variation in plastid DNA sequence. We have investigated whether changes in selected leaf development transcription factors underpin the recent, rapid diversification of this large group of succulent plants. Degenerate primers designed to conserved regions of Asymmetric Leaves1/Rough Sheath 2/Phantastica (ARP) and the Class III HD-ZIP family of genes, were used to amplify sequences corresponding to these genes from several species within the Mesembryanthemoideae and Ruschioideae subfamilies. Two members of the Class III HD-ZIP family were identified in both the Mesembryanthemoideae and Ruschioideae, and were derived from an ancient gene duplication event that preceded the divergence of gymnosperms and angiosperms. While a single ARP orthologue was identified in the Mesembryanthemoideae, two paralogues, ARPa and ARPb, were identified in the Ruschioideae subfamily. ARPa was present in all species of Ruschioideae analysed in this study. ARPb has been lost from the Apatesieae and Dorotheantheae tribes, which form an early evolutionary branch from the Ruschieae tribe, as well as from selected species within the Ruschieae. The recent duplication and subsequent selected gene loss of the ARP transcription factor correlates with the rapid diversification of plant forms in the Ruschioideae.

Eight new species of Aizoaceae from the Cedarberg and Namaqualand, South Africa

Summary: The shrubby members of the Mesembryanthema are still poorly known and further field work and study of herbarium material has led to the recognition of eight new species. Seven of these species are placed in the Ruschioideae: Phiambolia longifolia Klak, Phiambolia similis Klak, Ruschiella cedrimontana Klak, Ruschia albida Klak, Ruschia magnifica Klak, Leipoldtia gigantea Klak and Hammeria cedarbergensis Klak. In addition, one species of Mesembryanthemoideae, Mesembryanthemum bulletrapense Klak, is described here. Five of these species are found in the Cedarberg area, whereas L. gigantea and M. bulletrapense occur in Namaqualand. Furthermore, two new names and one new combination in Mesembryanthemum are published, which replace recently published homonyms.

Producing a plant diversity portal for South Africa

The National Research Foundation (grant reference number: UID92629) and Royal Society (grant reference number: SA140038) are thanked for the funding that was awarded to host an e-Flora workshop in South Africa.