The gum exudates from some acacia subspecies of the series botryocephalae

Gum specimens from A. deanei subsp. paucijuga (two samples), A. irrorata subsp. irrorata, and A. dealbata subsp. subalpina have been analysed. There are minor differences between the two specimens from A. deanei subsp. paucijuga, but they, and the gum from A. irrorata subsp. irrorata, have analytical parameters that correspond well with those for species in the proposed Group A within the Botryocephalae. In contrast, the gum from A. dealbata subsp. subalpina conforms well with the analytical parameters established for A. dealbata gum, and the slight analytical differences lead to it being assigned with greater confidence to the proposed Group B. Now that the gum exudates from approximately 40% of the species within the Botryocephalae have been studied and shown to fall into two different types, it is hoped that the chemical data may be meaningful taxonomically.     

Some Acacia gum exudates of the section Phyllodineae

Australian gum specimens from Acacia saliciformis, A. xanthina, A. rostellifera, A. murrayana (two specimens differing in the mode of initiation of gum exudation), A. georginae, A. cyclops, A. implexa, and an un-named species (Maslin ‘P31’) have been analysed. The first four of these are placed within Bentham's Series 1, subseries 6F, A. georginae within subseries 7E, and the remainder within subseries 7F. These data extend considerably the ranges of the analytical parameters reported previously for phyllodine species. The molecular weights of the gums from A. cyclops and A. implexa are much higher than those reported earlier for South African specimens; this may affect some taxonomic deductions based on their examination. The gum composition of A. saligna can no longer be regarded as atypical of a phyllodinous species; a suggestion that A. saligna should be transferred to the section Juliflorae may require reconsideration. The major difference between the specimens of gum from A. murrayana lies in their nitrogenous content. Data are reported for the amino acid compositions of the gums from A. saliciformis and A. xanthina.     

The gum exudates from some closely related Acacia species of the subseries Uninerves racemosae (section phyllodineae)

Australian gum specimens from Acacia aestivalis, A. chrysella, A. jennerae and A. microbotrya (five specimens differing slightly in some morphological characters) have been studied. These species, placed within Bentham's Series 1, subseries 6F (Uninerves racemosae) are closely related, forming part of the recognized A. microbotrya group. The five specimens from A. microbotrya show minor variations, similar in extent to those established previously for gums from other species. The gums from A. chrysella and A. jennerae are similar to those from A. microbotrya in chemical composition. The gum from A. aestivalis differs from those from A. microbotrya, A. chrysella and A. jennerae in two main respects: it is more acidic and has a much higher methoxyl content. Thus significant differences in gum composition can be shown by some species that differ only slightly in morphological characters. Data for the amino acid compositions of the proteinaceous components of the gums from A. aestivalis, A. jennerae and A. microbotrya, differ considerably from those for the gums from other species belonging to the Uninerves racemosae, e.g. A. saliciformis and A. xanthina, which are much more viscous and have higher proteinaceous contents containing much higher proportions of the amino acids commonly involved in linkages with sugars. Of the closely related species studied, A. aestivalis is closer to A. microbotrya than A.jennerae in terms of the amino acid compositions of their gums, a reversal in the relative affinities shown by their polysaccharide parameters. Thus amino acid compositions are of interest chemotaxonomically and also in terms of the tertiary structures of Acacia gum exudates.     

The composition and properties of gum exudates from subspecies of Acacia tortilis

Gum specimens from Acacia tortilis ssp. spirocarpa, ssp. raddiana var. pubescens (two specimens) and ssp. heteracantha (three specimens) have been analysed. The results are of chemotaxonomic interest. Although the gum from ssp. raddiana var. pubescens appears to be intermediate between those from ssp. spirocarpa and ssp. heteracantha in terms of some of the analytical parameters, the overall impression is that ssp. raddiana is more similar chemically to ssp. spirocarpa than to ssp. heterocantha. The latter yields a viscous, proteinaceous polysaccharide that differs from those from both ssp. spirocarpa and ssp. raddiana by having a much higher ratio of arabinose to galactose, higher nitrogen and methoxyl contents, and much higher intrinsic viscosity and molecular weight; preliminary experiments have shown this gum to consist of two components.     

Some highly proteinaceous Acacia gum exudates of the subseries Juliflorae

Analytical data for the gum exudates from Acacia difficilis, A. dimidiata, A. eriopoda, A. maidenii, A. stipuligera, A. torulosa and A. tumida are presented. Of these, five are highly proteinaceous; they also have high methoxyl contents and very low rhamnose contents. In contrast, A. dimidiata shows no unusual analytical parameters, and A. maidenii gum has alowarabinose content and a high rhamnose content, thus having a sugar composition of the type first observed in the gum from A. saligna. The gum from A. maidenii is also of interest as its analytical data are closely similar to those for A. longifolia, the only other tetramerous member of the subseries Juliflorae to have been studied. The data reported extend even further the unusual ranges of analytical parameters found within the Juliflorae, and confirm its great heterogeneity and chemotaxonomic interest.     

The composition of eight Acacia gum exudates from the series Gummiferae and Vulgares

An analytical study has been made of gum specimens from Acacia hebeclada, A. kirkii, A. newbrownii and A. reficiens (all of the series Gummiferae) and of Acacia erubescens, A.fleckii, A. mellifera ssp. mellifera and A. mellifera ssp. detinens (all of the series Vulgares). The data obtained give further support for the main chemotaxonomic differences between the Gummiferae and Vulgares species recorded previously. In addition, two of the species studied have exceptional features; the gum exudate from A. hebeclada contains 9.4% of nitrogen; that from A. erubescens contains 12% of glucose.     

Fluorinated carbohydrates. IV. 4-deoxy-4-fluoro-D-galactose

An analytical study has been made of gum specimens from Acacia deanei, A. filicifolia (three specimens), A. leucoclada, A. parramattensis (two specimens), A. parvipinnula, A. silvestris, A. terminalis, and A. trachyphloia, which are species belonging to Series II ({Botryocephalae}) in Bentham's classification of the genus. The three specimens from A. filicifolia are all closely similar, but the specimens from A. parramattensis differ appreciably in parameters other than their sugar ratios. Several of the analytical values reported increase considerably the range of values established so far for Acacia gum exudates. The Botryocephalae species give gum exudates of at least 2 chemically distinct types. Group A species (A. deanei, A. parramattensis, A. parvipinnula, and {A. trachyphloia}) have low galactose-arabinose ratios (<2:1) but have strongly negative rotations, high intrinsic viscosities and molecular weights, and relatively high nitrogen, methoxyl, uronic anhydride, and rhamnose contents. Group B species (A. filicifolia, A. leucoclada, and A. terminalis) have high galactose-arabinose ratios (> ) but low negative or positive rotations, low intrinsic viscosities and molecular weights, and relatively low nitrogen, methoxyl, uronic anhydride, and rhamnose contents.     

The proteinaceous components of the gum exudates from some phyllodinous Acacia species

Acacia gum exudates are proteinaceous polysaccharides; their protein content ranges from ca 0.2 to 45%.The data presented show that the amino acid compositions of the gums from 12 phyllodinous species (10 from Bentham's sub-series Uninerves racemosae, two from sub-series Juliflorae) also vary considerably, particularly in respect of their hydroxyproline content (55 residues per 1000 residues in A. aestivalis gum, 287 residues per 1000 in A. saliciformis gum). The proportions of some other amino acids, e.g. alanine, aspartic acid, proline and serine also vary considerably, but the proportions of others, e.g. cystine, methionine, histidine, threonine, tyrosine and valine, are remarkably constant. The amino acid composition of gums with a very low protein content (e.g. A. victoriae and A. mycrobotrya) is similar to that for a highly proteinaceous gum (A. tumida). There are, however, considerable differences between the amino acid compositions of the gums from A. saligna and A. pycnantha (South African and Western Australian specimens). This strengthens previous chemotaxonomic evidence, based on the polysaccharide parameters of their gums, that these two species are not as close taxonomically as was originally believed from morphological considerations.     

The composition of the gum exudates from some combretum species; the botanical nomenclature and systematics of the combretaceae

An analytical study has been made of gum specimens from Combretum collinum, C. collinum subsp. hypopilinum, C. erythrophyllum, C. nigricans, C. fragrans, and C. glutinosum. In comparison with the genus Acacia, both the botanical classification and synonymy, and the chemistry, are more complex. Glucuronic acid, galacturonic acid, 4-O-methylglucuronic acid, galactose, arabinose, and rhamnose are present in all the specimens studied. In addition, mannose and xylose are present in the gum from C. collinum, which is therefore similar to C. hartmannianum. The data now available suggest that, as a group, the genus Combretum produces gum exudates that are more viscous, of higher molecular weight, and more acidic than those of the Acacia group.     

The composition of acacia gum exudates from species of the subseries Juliflorae

An analytical study has been made of gum specimens from Acacia auriculiformis (two specimens), A.holosericea, A.mangium, A.leptostachya and A.pubifolia, which belong to subseries Juliflorae of the Series Phyllodineae. These gums appear to be more proteinaccous, more acidic and more viscous, with higher methoxyl contents and higher molecular weights but with lower proportions of rhamnose and arabinose, than the majority of Acacia gums studied so far.     

2-β-d-Glucopyranosyloxy-2-methylpropanol in Acacia sieberana var. woodii

A new diol glucoside, 2-β-d-glucopyranosyloxy-2-methylpropanol, the first reported naturally occurring monoglucoside of an aliphatic dihydric alcohol, was isolated from pods of Acacia sieberana var. woodii. Structure elucidation was based on ¹ H and ¹³C NMR spectroscopy, and enzymatic analyses. The compound was hydrolysed very slowly by almond β-glucosidase, but cleaved by a β-glucuronidase enzyme complex from Helix pomatia.     

Population genetics of the endangered Canarian endemic Atractylis arbuscula (Asteraceae): implications for taxonomy and conservation

We use the information provided by 36 RAPD loci and 15 morphological traits to describe and construe the population differentiation in A. arbuscula, a Canarian endemic Asteraceae threatened with extinction that exhibits a disjunct distribution in the islands of Gran Canaria (var. schizogynophylla) and Lanzarote (var. arbuscula). Our evaluation of morphological characters and the extent of RAPD differentiation found sets the stage for a taxonomic restructuring to hoist both var. arbuscula and var. schizogynophylla to subspecies category. Our genetic results suggest that fragmentation and generally low population sizes are jeopardising the survival of this species through a predominance of stochastic processes in microevolutionary dynamics, especially in Gran Canaria, where subpopulations exhibit the lowest levels of genetic variation and gene flow. If, as most Asteraceae, these plants have a sporophytic self-incompatibility system, the scarce reproductive turnover observed in the much smaller subpopulations from Gran Canaria (ssp. schizogynophylla) is possibly more influenced by a deficiency of S-alleles (that would be provoking the unavailability of compatible mating types, and a cascade of deleterious effects associated with the Allee effect) than by a reduced pollinator visitation frequency. Based on the depauperated values of genetic parameters for this subspecies, urgent mixed subpopulation reinforcements and reintroductions (with specimens belonging to the same subspecies) seem advisable on the grounds that they might allow the isolated habitat remnants to retrieve from inbreeding through the introduction of a new stock of S-alleles and the subsequent production of genotypes that may have a higher selective value.     

TWO NEW SOREDIATE TAXA OFPELTIGERA

Examination of specimens ofPeltigera didactyla, from Africa, Asia, Europe and North America revealed that this sorediate species includes three entities that can be separated on morphological characters. A new species,P. lambinonii, is described from East Africa, and a new combinationP. didactylavar.extenuata, is proposed to accommodate morphs from mesic forest habitats in Asia, Europe and North America. Despite this taxonomic reduction,P. didactylavar.didactylaremains a ubiquitous taxon. The former two taxa often produce methyl gyrophorate, which can co-occur with traces of gyrophoric acid. These tridepsides were only rarely detected in var.didactyla; their occasional presence seems to be best explained by hybridization. The taxonomic and ecological significance of these substances is discussed.     

New species ofEdmundmasonia (Hyphomycetes)

A new species ofEdmundmasonia Subram,E. villosa is illustrated and described from decaying culms of bamboo collected in Cuba. Two others, which are Indian species, are briefly discussed.     

Seed viability of five wild Saudi Arabian species by germination and X-ray tests

Our objective was to evaluate the usefulness of the germination vs. the X-ray test in determining the initial viability of seeds of five wild species (Moringa peregrina, Abrus precatorius, Arthrocnemum macrostachyum, Acacia ehrenbergiana and Acacia tortilis) from Saudi Arabia. Usually several days were required to determine the viability of all five species via germination tests. However, X-ray test will give immediate results on filled/viable seeds. Seeds of all species, except Acacia ehrenbergiana and Acacia tortilis showed high viability in both germination (96–72% at 25/15 °C, 94–70% at 35/25 °C) and X-ray (100–80%) test. Furthermore, there was a general agreement between the germination (19%, 14% at 25/15 °C and 17% and 12% at 35/25 °C) and X-ray (8%, 4%) tests in which seed viability of Acacia ehrenbergiana and Acacia tortilis was very low due to insect damaged embryo as shown in X-ray analysis. Seeds of Abruspreca torius have physical dormancy, which was broken by scarification in concentrated sulfuric acid (10 min), and they exhibited high viability in both the germination (83% at 25/15 °C and 81% at 35/25 °C) and X-ray (96%) tests. Most of the nongerminated seeds of the five species except those of Acacia ehrenbergiana and Acacia tortilis, were alive as judged by the tetrazolium test (TZ). Thus, for the five species examined, the X-ray test was proved to be a good and rapid predictor of seed viability.     

Optimisation or satiation,testing diet selection rules in goats

Several hypotheses have been formulated to explain diet selection by herbivores, focusing on the maximization of nutrient intake, the minimization of plant secondary compounds, or the satiety hypothesis. This research aimed at studying diet selection revealing which chemical characteristics of plants form the bases for dietary preferences of goats. This was done by setting up a feeding experiment with three different combinations of tree species Acacia karroo, A. nilotica and A. sieberana. The chemical characteristics of these three Acacia species were used to predict diet selection. To test the validity of the satiety hypothesis, goats were placed on a conditioning diet of one of the three species. We found a clear preference for A. karroo and an avoidance of A. nilotica when these two were offered to the goats. In trials where A. nilotica was present, tannin minimization was the best explaining diet selection rule. In trials where A. nilotica was not present, however, tannin minimization was not the best explanation. Our findings suggest that tannins are not avoided but kept below a certain threshold. Below this threshold, goats based their dietary choices on other chemical characteristics of the Acacia species. Acid detergent fibre (ADF) minimization could then best explain preferences in trials with Acacia karroo and A. sieberana that have generally low tannin content. Goats did not maximize nutrient intake or digestibility, and we found no support for the satiety hypothesis.     

Implications of climate warming on seedling emergence and mortality of African savanna woody plants

Seedling emergence from scarified seeds and mortality of different seedling cohorts of five African savanna woody species (Acacia polyacantha, A. sieberana, Bauhinia thonningii, Dichrostachys cinerea and Ziziphus abyssinica) were studied under field conditions at a site in central Zambia. The study was conducted over a 4-year period, from 2003 to 2007. The objectives of the study were to determine climate factors that significantly influence seedling emergence rate and mortality in order to assess likely responses of the studied species to a warmer climate. Mean seedling emergence rate was 12% in D. cinerea and Z. abyssinica, 17% in B. thonningii, 47% in A. poyacantha and 62% in A. sieberana. Climate factors did not significantly affect seedling emergence in A. sieberana while temperature significantly influenced seedling emergence rate in the other species. Under a 1° warmer climate, seedling emergence rate was predicted to decline in A. polyacantha, B. thonningii and Z. abysssinica but is likely to increase slightly in D. cinerea. Time of seedling emergence during the wet season did not appear to affect seedling survival. Temperature also significantly influenced seedling mortality in all the studied species such that under a warmer climate, mortality was predicted to increase in A. sieberana and D. cinerea but decrease in A. polyacantha, B. thonningii and Z. abyssinica. As the studied species exhibited differential optimum temperature conditions for seedling emergence and seedling survival, they are likely to respond to climate warming in different but predictable ways. The results of the study are useful to forest management and development of climate change adaptation strategies in southern Africa.     

Spatio-environmental determinants of the genetic structure of three steppe species in a highly fragmented landscape

Habitat fragmentation can lead to substantial genetic depletion. As a consequence, restoration schemes often involve the introduction of propagules into isolated plant populations to improve genetic diversity. To avoid introducing maladapted seed material, such measures need to account for landscape genetic processes. However, surprisingly little is known as to whether different species within a distinct fragmented ecosystem respond similarly or idiosyncratically to eco-geographical variation.Using AFLP markers, we studied the population genetic structure in three species of the highly fragmented Kulunda steppe (South Siberia): Adonis villosa, Jurinea multiflora and Paeonia hybrida. In each population, we conducted a vegetation survey. We performed Mantel tests and an RDA approach to investigate how genetic structure was affected by three spatio-environmental variables: spatial distance, floristic composition and climate.Despite strong fragmentation, genetic diversity was moderate (A. villosa, J. multiflora) to high (P. hybrida), while differentiation was weak (A. villosa) to moderate (P. hybrida, J. multiflora). Mantel tests showed that spatial distance correlated with genetic distance in A. villosa and P. hybrida. Floristic composition was significantly associated with genetic differentiation in A. villosa. Climate did not have an effect on genetic structure in any species.All three species are long-lived, which may contribute to explaining why genetic effects of recent fragmentation are still limited. We highlight that floristic composition can be a powerful predictor of population differentiation in species that show rather stable conditions in their recent population histories (e.g. A. villosa). This can have important implications for identifying source populations where restoration actions involve the (re)introduction of propagules. In contrast, for P. hybrida and J. multiflora, we could not identify deterministic drivers of differentiation. We advocate that future studies should aim at disentangling the interactive effects of varying life cycles, eco-evolutionary population histories and spatio-environmental heterogeneity in fragmented landscapes.     

Gum exudates from the genus Grevillea (Proteaceae)

Analytical data are presented for gum specimens from Grevillea agrifolia, G. candelabroides, G. robusta, G. striata, and G. wickhamii (two specimens), and brief botanical details of this large, complex genus are given. The gum exudates, which are of high molecular weight, show good solubility and give solutions that are much more viscous than any of the Acacia exudates studied so far; they may therefore be of industrial interest.