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In this study we analysed ETS sequence data of 164 accessions belonging to 31 taxa of Salicornia, a wide‐spread, hygrohalophytic genus of succulent, annual herbs of Chenopodiaceae subfam. Salicornioideae, to investigate phylogenetic and biogeographical patterns and hypothesise about the processes that shaped them Furthermore, our aim was to understand the reasons for the notorious taxonomic difficulties in Salicornia. Salicornia probably originated during the Miocene somewhere between the Mediterranean and Central Asia from within the perennial Sarcocornia and started to diversify during Late Pliocene/Early Pleistocene. The climatic deterioration and landscape‐evolution caused by orogenetic processes probably favoured the evolution and initial diversification of this annual, strongly inbreeding lineage from the perennial Sarcocornia that shows only very limited frost tolerance. The further diversification of Salicornia was promoted by at least five intercontinental dispersal events (2× to South Africa, at least 3× to North America) and at least two independent polyploidization events resulting in rapidly expanding tetraploid lineages, both of which are able to grow in lower belts of the saltmarshes than their diploid relatives. The diploid lineages of Salicornia also show rapid and effective range expansion resulting in both widespread genotypes and multiple genotypes in a given area. Reproductive isolation through geographical isolation after dispersal, inbreeding, and comparatively young age might be responsible for the large number of only weakly differentiated lineages. The sequence data show that the taxonomic confusion in Salicornia has two major reasons: (1) in the absence of a global revision and the presence of high phenotypic plasticity, the same widespread genotypes having been given different names in different regions, and (2) striking morphological parallelism and weak morphological differentiation led to the misapplication of the same name to different genotypes in one region.

An important adaptation to CO2-limited photosynthesis in cyanobacteria, algae and some plants was development of CO2-concentrating mechanisms (CCM). Evolution of a CCM occurred many times in flowering plants, beginning at least 15-20 million years ago, in response to atmospheric CO2 reduction, climate change, geological trends, and evolutionary diversification of species. In plants, this is achieved through a biochemical inorganic carbon pump called C4 photosynthesis, discovered 35 years ago. C4 photosynthesis is advantageous when limitations on carbon acquisition are imposed by high temperature, drought and saline conditions. It has been thought that a specialized leaf anatomy, composed of two, distinctive photosynthetic cell types (Kranz anatomy), is required for C4 photosynthesis. We provide evidence that C4 photosynthesis can function within a single photosynthetic cell in terrestrial plants. Borszczowia aralocaspica (Chenopodiaceae) has the photosynthetic features of C4 plants, yet lacks Kranz anatomy. This species accomplishes C4 photosynthesis through spatial compartmentation of photosynthetic enzymes, and by separation of two types of chloroplasts and other organelles in distinct positions within the chlorenchyma cell cytoplasm.

SummaryKranz anatomy, with its separation of elements of the C 4 pathway between two cells, has been an accepted criterion for function of C 4 photosynthesis in terrestrial plants. However, Bienertia cycloptera (Chenopodiaceae), which grows in salty depressions of Central Asian semi-deserts, has unusual chlorenchyma, lacks Kranz anatomy, but has photosynthetic features of C 4 plants. Its photosynthetic response to varying CO 2 and O 2 is typical of C 4 plants having Kranz anatomy. Lack of night-time CO 2 ®xation indicates it is not acquiring carbon by Crassulacean acid metabolism. This species exhibits an independent, novel solution to function of the C 4 mechanism through spatial compartmentation of dimorphic chloroplasts, other organelles and photosynthetic enzymes in distinct positions within a single chlorenchyma cell. The chlorenchyma cells have a large, spherical central cytoplasmic compartment interconnected by cytoplasmic channels through the vacuole to the peripheral cytoplasm. This compartment is ®lled with mitochondria and granal chloroplasts, while the peripheral cytoplasm apparently lacks mitochondria and has grana-de®cient chloroplasts. Immunolocalization studies show enzymes compartmentalized selectively in the CC compartment, including Rubisco in chloroplasts, and NAD-malic enzyme and glycine decarboxylase in mitochondria, whereas pyruvate, Pi dikinase of the C 4 cycle is localized selectively in peripheral chloroplasts. Phosphoenolpyruvate carboxylase, a cytosolic C 4 cycle enzyme, is enriched in the peripheral cytoplasm. Our results show Bienertia utilizes strict compartmentation of organelles and enzymes within a single cell to effectively mimic the spatial separation of Kranz anatomy, allowing it to function as a C 4 plant having suppressed photorespiration; this raises interesting questions about evolution of C 4 mechanisms.

Chenopodiaceae‐Salicornioideae (14–16 gen./c. 90 spp.) are distributed worldwide in coastal and inland saline habitats. Most of them are easy to recognize by their succulent‐articulated stem with strongly reduced leaves and by flowers aggregated in dense, thick spike‐shaped thyrses. ITS and the atpB‐rbcL spacer were sequenced for 67 species representing 14 genera of Salicornioideae and analysed with maximum parsimony and maximum likelihood, a fossil‐calibrated molecular clock using the penalized likelihood method, and lineage through time plots. The evolution of stem, leaf, and flower morphology was traced using MacClade. Both molecular markers indicate that the monophyletic Salicornioideae originated in Eurasia during the Late Eocene/Early Oligocene (38.2–28.7 Mya) and experienced a rapid radiation into its major lineages during the Early Oligocene with Allenrolfea/Heterostachys, Kalidium, Halopeplis and Halocnemum/Halostachys branching off early. Already in the Middle Miocene (19.6–14.6 Mya) all major lineages of Salicornioideae were present. These additionally include Arthrocnemum/Microcnemum, the Halosarcia lineage (which includes all Australian species except for the Australian Sarcocornia) and the Salicornia/Sarcocornia lineage. A high intercontinental dispersability can be observed in Salicornioideae in particular in the Salicornia/Sarcocornia lineage with multiple colonization events in America, Australia and South Africa linked to the global aridification during the Oligocene, Late Miocene and Pliocene. The comparatively low species number of many genera is explained by a low number of niches present in the extreme habitats of Salicornioideae, strong interspecific competition mainly by close relatives, and by Pleistocene extinctions. We detected an evolutionary trend towards increasing reduction of the leaf lamina in Salicornioideae, with an ovate or terete leaf with a decurrent base as the plesiomorphic condition. Opposite phyllotaxis has arisen at least two times in the subfamily and is strongly correlated with the pair‐wise fusion of leaves (not bracts), the reduction of leaf lamina, and the articulation of stem. However, the articulated stems and reduced leaves also have evolved twice in lineages with alternate phyllotaxis, such as Allenrolfea and Kalidium caspicum. Only one shift from free to connate bracts occurred in Salicornioideae with at least one reversal within the Halosarcia lineage. The fusion of bracts is mostly accompanied by a partly or fully connation of bracts and axis resulting in club‐shaped spikes in which the flwers are tightly embedded in cavities. Both molecular trees are conflicting with the traditional tribes indicating that their diagnostic characters have originated by convergent evolution. For reasons of stability and clarity we propose that only one tribe, Salicornieae, should be recognized. The traditional circumscription of most genera is supported by the molecular results except for the closely related genera of the Australian Halosarcia clade and the Sarcocorni...

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Camphorosmeae constitute a species‐rich tribe of Chenopodiaceae‐Camphorosmoideae that consists mostly of subshrubs and annuals, distributed in steppes and semi‐deserts of Australia, Eurasia, North Africa, southern Africa and North America. We study (1) the relationships of Camphorosmeae to major lineages of the closely related Salsoloideae and (2) the diversification of the tribe with focus on the non‐Australian members using sequence variation of five different markers (rbcL gene, ndhF gene, atpB‐rbcL spacer, psbB‐psbH spacer, ITS) and morphological characters. The cpDNA analyses revealed six early‐branching lineages in Camphorosmoideae/Salsoloideae (Camphorosmeae, Salsoleae s.str., Caroxyloneae, Salsola kali clade, Nanophyton clade, Salsola genistoides clade) and supported partly (ndhF and atpB‐rbcL spacer) the sister‐group relationship of Camphorosmeae and all Salsolean clades. The distinctness of Camphorosmeae and Salsoleae s.l. is further supported by seed, stigma and pollen morphology. Molecular clock estimates point to an earlier radiation in Salsoleae s.l. (Early to Middle Oligocene) than in Camphorosmeae (Early Miocene). In Salsoleae s.l. early radiation might have been enhanced by multiple evolution of C4‐photosynthesis which facilitated the spread into drier habitats of Eurasia. In Camphorosmeae, C4‐photosynthesis likely evolved two times, probably in the Middle Miocene. During the Miocene Camphorosmeae spread from Eurasia to Australia, North America and at least two times to South Africa. Only the Australian lineage diversified, the others remained species‐poor. The molecular trees congruently resolve three major clades of unclear relationship within Camphorosmeae, Chenolea clade (five widely disjunct and morphologically divergent C3‐species, possibly remnants of old lineages), Sclerolaena clade (ca. 150 C3‐species from Central Asia [3 spp.] and Australia [147 spp.], probably the results of a rapid radiation during the Pliocene) and Bassia/Camphorosma clade (ca. 23 C4‐species and one C3/C4‐intermediate which are widely distributed in Eurasia and southern Africa). The phylogenies show the artificial state of the current generic and subtribal classifications of Eurasian, North American and South African Camphorosmeae. All non‐monotypic genera except Camphorosma and Neokochia were found to be polyphyletic. A revised classification of the tribe is proposed including reinstatement of the newly defined subfamily Camphorosmoideae, description of the new genera Spirobassia (1 sp.), Eokochia (1 sp.), Grubovia (3 spp.) and Sedobassia (1 sp.), and several new combinations and synonymizations.

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