A NEW VARIETY OFTHOTTEASIVARAJANII(ARISTOLOCHIACEAE) FROMWESTERN GHATS, INDIA

Thotteasivarajaniivar.anamalaianavar.nov., discovered from theAnamalaihills of Western Ghats, India is described and illustrated. The woody habit,comparatively less pubescent inflorescence and flowers, glabrous stem, petiole and fruits,highly reducedstaminodes, prominent bracts and bracteolesetc. are some of the characteristics that delimit thisvariety from the species proper.

Derived woodiness and annual habit evolved in African umbellifers as alternative solutions for coping with drought

Background One of the major trends in angiosperm evolution was the shift from woody to herbaceous habit. However, reversals known as derived woodiness have also been reported in numerous, distantly related clades. Among theories evoked to explain the factors promoting the evolution of derived woodiness are moderate climate theory and cavitation theory. The first assumes that woody habit evolves in response to mild climate allowing for prolonged life span, which in turn leads to bigger and woodier bodies. The second sees woodiness as a result of natural selection for higher cavitation resistance in seasonally dry environments. Here, we compare climatic niches of woody and herbaceous, mostly southern African, umbellifers from the Lefebvrea clade to assess whether woody taxa in fact occur in markedly drier habitats. We also calibrate their phylogeny to estimate when derived woodiness evolved. Finally, we describe the wood anatomy of selected woody and herbaceous taxa to see if life forms are linked to any particular wood traits. Results The evolution of derived woodiness in chamaephytes and phanerophytes as well as the shifts to short-lived annual therophytes in the Lefebvrea clade took place at roughly the same time: in the Late Miocene during a trend of global climate aridification. Climatic niches of woody and herbaceous genera from the Cape Floristic Region overlap. There are only two genera with distinctly different climatic preferences: they are herbaceous and occur outside of the Cape Floristic Region. Therefore, studied herbs have an overall climatic niche wider than their woody cousins. Woody and herbaceous species do not differ in qualitative wood anatomy, which is more affected by stem architecture and, probably, reproductive strategy than by habit. Conclusions Palaeodrought was likely a stimulus for the evolution of derived woodiness in the Lefebvrea clade, supporting the cavitation theory. The concurrent evolution of short-lived annuals withering before summer exemplifies an alternative solution to the same problem of drought-induced cavitation. Changes of the life form were most likely neither spurred nor precluded by any qualitative wood traits, which in turn are more affected by internode length and probably also reproductive strategy.

A new species of Osteospermum subgen. Tripteris (Asteraceae: Calenduleae) from the Namib Desert, Namibia

Osteospermum namibense, here described as a new species, is known only from the northern part of the Namib Desert in the Kaokoveld Centre of Endemism, northwestern Namibia. Within a broad generic concept for Osteospermum (tribe Calenduleae), the new species is a member of subgen. Tripteris. These dwarf shrubs grow on rocky outcrops under harsh desert conditions. Diagnostic characters for Osteospermum namibense include the perennial, woody habit, di- or trichotomous branching, succulent leaves arranged in rosettes, and capitula with 12–14 rays. A comparison of some of the more prominent morphological features to differentiate between O. namibense and its possible nearest relative, O. microcarpum (=Tripteris microcarpa), is provided. Based on IUCN Red List categories and criteria, a conservation assessment of Vulnerable (VU D1) is recommended for the new species.

How small and constrained is the genome size of angiosperm woody species

Angiosperm hardwood species are generally considered to show an average smaller genome size with a narrow range of variation than their herbaceous counterparts. Various explanations pertaining to limitations of cell size exerted by wood fibers, the requirement of smaller stomata, longer generation time, large population size, etc., have been put forward to account for their small and constrained genome size. Yet studies done in the past several years show that genomically as well as evolutionarily, hardwoods are as diverse and active as their herbaceous counterparts. This is entirely supported by the presence of well developed inter and intraspecific polyploid series and natural triploidy in many genera. Polyploidy, in some instances has been shown to confer adaptability to arid and salt stress conditions and in colonization of new areas. Moreover, hardwoods also show reasonable amenability to the induced polyploidy which abruptly changes the balance between nuclear and cell size. Polyploidy has been induced in many hardwoods to restore fertility in interspecific hybrids and for the production of triploids.Furthermore, some cases studied show that genome size variation in hardwoods can be as variable as that of herbaceous species. Genome size has been shown to vary remarkably both at homoploid level as well as by polyploidy in certain genera. In the same way, the genome size is not correlated with the habit in certain groups having both herbaceous and woody taxa. This point is further proved by the presence of secondary and insular woody habit in certain cases where either the transition to woodiness is not followed by any diminution in the genome size, or the genome size of insular woody species may be even more than that of the congeneric herbaceous species. This shows that woody habit does not by itself put any constraints on the genome size either at homoploid or at polyploidy levels. The genome size in fact, not only varies significantly in many congeneric woody species but also may not show any correlation with the habit when woody and herbaceous species are compared in some narrow taxonomic groups studied.

PHYLOGENY, BIOGEOGRAPHY AND CHARACTER EVOLUTION OF DORSTENIA (MORACEAE)

Dorstenia, the second largest genus (105 species) within the Moraceae, is the only genus in the family with woody, herbaceous and succulent species. All but one species of Dorstenia are restricted to the Neotropics or Africa, and it is the only genus in the family with an almost equal transatlantic distribution. This work presents the first molecular phylogeny and the first evolutionary study to examine origin and diversification within the genus. We inferred the phylogeny with ITS sequence data using Bayesian and maximum likelihood approaches. We tracked the evolution of distinct morphological characters and tested for correlated evolution in multiple characters. Time and place of Dorstenia’s origin were estimated to test a post-Gondwanan versus a Gondwanan origin hypothesis using fossil calibrations, Bayesian molecular dating, and maximum likelihood-based ancestral range reconstructions. Our phylogenetic analysis supports the monophyly of Dorstenia; previous subgeneric classifications are polyphyletic and must be re-evaluated. Woody habit, phanerophytic life form, macrospermy, and lack of storage organs are ancestral traits found in African Dorstenia. Evolution of woodiness and macrospermy are correlated. Dorstenia appears to have originated in Africa, radiated into the Neotropics and subsequently re-colonised Africa. Whether or not the extant distribution is the result of vicariance or dispersal is equivocal.

The physiology ofSalix

SynopsisSalixhas many physiological features in common with other deciduous woody plants, e.g. C3photosynthesis, occurrence of latitudinal photoperiodic ecotypes, and organic N (no) flux to the shoot in the xylem. Special points about the physiology ofSalixspp. which may have impact on their ecology and economic uses include: (i) relatively high (for woody plants) light-saturated rate of photosynthesis on a leaf area or leaf dry weight basis, (ii) sex differences in water (transpiration) costs of growth, (iii) very limited seed longevity and a wide range of temperature and light conditions permitting germination, and (iv) ready rooting and establishment of naturally or artificially detached twigs and branches. Areas in which work onSalixhas been especially influential for the development of plant physiology include: (i) the analysis of phloem functioning using aphids, (ii) the role of photoinhibition under natural conditions, and (iii) the realisation that the woody habit need not constrain the achieved activity of enzymes and hence N-based metabolic rates.