Ungulate browsing in winter reduces the growth of <Emphasis Type="Italic">Fraxinus</Emphasis> and <Emphasis Type="Italic">Acer</Emphasis> saplings in subsequent unbrowsed years

Browsing by ungulates has become a hotly debated issue in many European mountain forests in the past century. Acer pseudoplatanus L. and Fraxinus excelsior L. are broadleaved tree species that are preferentially browsed by roe deer (Capreolus capreolus) in central Europe. We analyzed growth data from shaded saplings of both tree species to quantify the extent to which height growth after game browsing is reduced in subsequent, unbrowsed years in forest stands. Sixty saplings of F. excelsior and A. pseudoplatanus from forest stands at Albisriederberg (Switzerland) were available to us that had been dissected into pieces that then were split in the middle for counting tree rings and assessing ungulate damage. We fitted the von Bertalanffy growth equation to these height growth data and included a reduction factor for winter browsing. Both tree species showed significantly reduced height growth in unbrowsed years after one to several browsing events in winter, and this effect increased with the number of browsing events. Saplings with a high growth rate showed a higher growth reduction. After winter browsing, height growth of A. pseudoplatanus saplings was less affected in unbrowsed years than that of F. excelsior saplings. We conclude that browsed saplings of these species in forest stands are not able to compensate browsing-induced height loss, but that height differences between browsed and unbrowsed saplings probably increase over time. A comparison between our analysis and the parameters estimated using equations published by Eiberle for predicting age at 130 cm height suggests that our parameter values are rather conservative estimates of the growth reduction effect after winter browsing. Neither F. excelsior nor A. pseudoplatanus show a distinct pattern in browsing-induced growth reduction with respect to soil moisture, nutrient level, and altitude. We thus conclude that our results are likely to be valid for a wide range of forested sites.     

Anatomical changes induced by increasing NaCl salinity in three fodder shrubs, <Emphasis Type="Italic">Nitraria retusa</Emphasis>, <Emphasis Type="Italic">Atriplex halimus</Emphasis> and <Emphasis Type="Italic">Medicago arborea</Emphasis>

Nitraria retusa and Atriplex halimus (xero-halophytes) plants were grown in the range 0–800 mM NaCl while Medicago arborea (glycophyte) in 0–300 mM NaCl. Plants were harvested after 120 days of salt-treatment. The present study was designed to study the effect of salinity on root, stem and leaf anatomy, water relationship, and plant growth in greenhouse conditions. Salinity induced anatomical changes in the roots, stems and leaves. The cuticle and epidermis of N. retusa and A. halimus stems were unaffected by salinity. However, root anatomical parameters (root cross section area, cortex thickness and stele to root area ratio), and stem anatomical parameters (stem cross section area and cortex area) were promoted at 100–200 mM NaCl. Indicating that low to moderate salinity had a stimulating effect on root and stem growth of these xero-halophytic species. At higher salinities, root and stem structures were altered significantly, and their percentages of reduction were higher in A. halimus than in N. retusa whereas, in M. arborea, they were strongly altered as salinity rose. NaCl (100–300 mM) reduced leaf water content by 21.2–56.2% and specific leaf area by 51–88.1%, while increased leaf anatomical parameters in M. arborea (e.g. increased thickness of upper and lower epidermis, palisade and spongy mesophyll, entire lamina, and increased palisade to spongy mesophyll ratio). Similar results were evidenced in A. halimus leaves with salinity exceeding 100 mM NaCl. Leaves of N. retusa were thinner in salt-stressed plants while epidermis thickness and water content was unaffected by salinity. The size of xylem vessel was unchanged under salinity in the leaf’s main vein of the three species while we have increased number in M. arborea leaf main vein in the range of 200–300 mM NaCl. A longer distance between leaf vascular bundle, a reduced size and increased number of xylem vessel especially in stem than in root vascular system was evidenced in M. arborea treated plants and only at (400–800 mM) in the xero-halophytic species. The effects of NaCl toxicity on leaf, stem and root ultrastructure are discussed in relation to the degree of salt resistance of these three species. Our results suggest that both N. retusa and A. halimus show high tolerance to salinity while M. arborea was considered as a salt tolerant species.     

Photosystem II photochemistry and physiological parameters of three fodder shrubs, <Emphasis Type="Italic">Nitraria retusa</Emphasis>, <Emphasis Type="Italic">Atriplex halimus</Emphasis> and <Emphasis Type="Italic">Medicago arborea</Emphasis> under salt stress

Nitraria retusa and Atriplex halimus (xero-halophytes) plants were grown in the range 0–800 mM NaCl while Medicago arborea (glycophyte) in 0–300 mM NaCl. Salt stress caused a marked decrease in osmotic potential and a significant accumulation of Na⁺ and Cl⁻ in leaves of both species. Moderate salinity had a stimulating effect on growth rate, net CO₂ assimilation, transpiration and stomatal conductance for the xero-halophytic species. At higher salinities, these physiological parameters decreased significantly, and their percentages of reduction were higher in A. halimus than in N. retusa whereas, in M. arborea they decreased linearly with salinity. Nitraria retusa PSII photochemistry and carotenoid content were unaffected by salinity, but a reduction in chlorophyll content was observed at 800 mM NaCl. Similar results were found in A. halimus, but with a decrease in the efficiency of PSII (F′v/F′m) occurred at 800 mM. Conversely, in M. arborea plants we observed a significant reduction in pigment concentrations and chlorophyll fluorescence parameters. The marked toxic effect of Na⁺ and/or Cl⁻ observed in M. arborea indicates that salt damage effect could be attributed to ions’ toxicity, and that the reduction in photosynthesis is most probably due to damages in the photosynthetic apparatus rather than factors affecting stomatal closure. For the two halophyte species, it appears that there is occurrence of co-limitation of photosynthesis by stomatal and non-stomatal factors. Our results suggest that both N. retusa and A. halimus show high tolerance to both high salinity and photoinhibition while M. arborea was considered as a slightly salt tolerant species.     

Defoliation depletes the carbohydrate reserves of resprouting <Emphasis Type="Italic">Acacia</Emphasis> saplings in an African savanna

Over the past century there has been a global trend towards tree expansion and densification in rangelands and savannas. This phenomenon is commonly referred to as bush encroachment. In South Africa Acacia karroo is one of the key species responsible for bush encroachment. It has been suggested that the combination of fire and browsing might limit bush encroachment by A. karroo more effectively than either browsing or fire alone. We hypothesized that these repeated disturbances progressively deplete root carbohydrates and compromise resprouting ability. This was tested by burning and then manually defoliating A. karroo once a month for 1 year. Manual defoliation did not inhibit the rapid shoot elongation after topkill of A. karroo saplings. During this initial phase, the growth of the new shoots of A. karroo was dependent more on mobilised root reserves than on photoassimilates from the new shoots. Frequent manual defoliation of resprouting A. karroo saplings prevented the replenishment of starch reserves. We suggest a mechanism for how the interaction of browsing and fire can suppress and perhaps reverse bush encroachment in African savannas. Saplings that have reduced starch reserves at the end of dry season due to browsing will struggle to resprout if they are burnt. Even if they do not die, they will be less able to escape fire damage in the next fire than if they had been able to resprout unimpeded.     

<Emphasis Type="Italic">Linaria khalkhalensis</Emphasis> (<Emphasis Type="Italic">Linaria</Emphasis> sect. <Emphasis Type="Italic">Linaria</Emphasis>, Scrophulariaceae), a new species from Iran

Summary   Linaria khalkhalensis Hamdi & Assadi is described as a new species from Azerbaijan and Guilan provinces (northern Iran), belonging to Linaria sect. Linaria. It is close to Linaria lineolata Boiss. and L. elymaitica (Boiss.) Kuprian., which it resembles in habit and vegetative features. However, floral and seed characters together with a distinctive geographical distribution, warrant recognition at the species rank. An illustration of the new species, a distribution map, scanning electron micrographs of seed and capsule surfaces, and an identification key are also included.     

Species differentiation and gene flow in the Blackbutts (genus <Emphasis Type="Italic">Eucalyptus</Emphasis> subgenus <Emphasis Type="Italic">Eucalyptus</Emphasis> section <Emphasis Type="Italic">Pseudophloius</Emphasis>)

The significance of the taxonomic distinction of two species of Blackbutt was studied by analysing patterns of genetic (microsatellite markers; n = 13) and phenetic (capsule morphology) differentiation. Analysis of genetic structure using a Bayesian modelling approach on range-wide samples of both taxa (n = 457) showed the major division was within the more widely distributed species, Eucalyptus pilularis, and not aligned with taxonomy. Comparisons of intra- and inter-taxon genetic differentiation in paired-samples of taxa from each of four locations spanning the distribution of the more restricted E. pyrocarpa, showed that around twice as much variation was found among locations within taxa, than between taxa. Despite the lack of differentiation at effectively neutral microsatellite markers, significant phenetic differences (including capsule size) were evident between taxa at most sites. A landscape mosaic of taxa, coincident with changes in elevation, vegetation and soil types, suggested some phenetic differences were probably adaptive and spatial differentiation was stabilised by environmental factors. An absence of morphological intermediates and a lack of correlation in the rankings of locus inter-taxon differentiation (Phi_BT) across locations, was consistent with parapatric origins for E. pyrocarpa. We conclude the taxa are at the lower end of the speciation spectrum and might best be viewed as ecotypes, divergent in evolutionary potential, but with genomes broadly permeable to inter-taxa gene flow. Gene exchange between plantings of E. pilularis and nearby E. pyrocarpa forest is likely as the two taxa appear to have few barriers to reproduction.     

Post-pollination hybridization barriers in <Emphasis Type="Italic">Nicotiana</Emphasis> section <Emphasis Type="Italic">Alatae</Emphasis>

Nicotiana section Alatae contains eight species with variable flower sizes and morphologies. Section members readily hybridize in the glasshouse, but no hybrids have been observed in natural sympatric and parapatric populations. To investigate interspecific crossing relationships with respect to mechanisms preventing hybridization, all members of section Alatae were intercrossed in a complete diallel. We found positive correlation between the pistil length of the pollen donor and interspecific seed set relative to the conspecific cross. Pollen tube growth rate and pollen donor pistil length were positively correlated as well. Furthermore, pollen from short-pistil members of section Alatae could only grow a maximum distance proportional to, but greater than, their own pistil lengths. Our results show that pollen tube growth capacity (i.e., rate and distance), provides a hybridization barrier in long-pistil species × short-pistil species crosses. We also found another hybridization barrier not specifically related to pollen tube growth capacity in short-pistil species × long-pistil species. Taken together, these barriers can generally be described by a ‘pistil-length mismatch’ rule; in section Alatae, pollen has the most success fertilizing ovules from species with pistil lengths similar to their own. This rule could contribute to hybridization barriers in Section Alatae because the species display dramatically different pistil lengths. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Demographic variation of dwarf birch (<Emphasis Type="Italic">Betula nana</Emphasis>) in communities dominated by <Emphasis Type="Italic">Ledum palustre</Emphasis> and <Emphasis Type="Italic">Vaccinium uliginosum</Emphasis>

The structure and demographic processes were compared in shrub communities to test the effects of vegetation succession on population growth, fecundity and abundance of the dwarf birch (Betula nana L.), which is a rare and endangered plant species in Poland and a glacial relict in Central Europe. The effects of Ledum palustre L. and Vaccinium uliginosum L. were studied in the Linje nature reserve in Chełmińskie Lake District (northern Poland), in three permanent plots on a peat bog. Vegetative growth and reproduction of B. nana were lower in plant communities dominated by L. palustre and V. uliginosum, than in a reference site. Fecundity was also lower, despite the fact that the percentage share of potentially fertile age groups was similar in all study sites. Mortality of ramets was independent of vegetation, both for juvenile and mature stages. The results confirm that B. nana is intolerant of shade, and it is more abundant in vegetation without competitors. Light limitation can lead to its decline, primarily by a decrease in vegetative growth. Sexual reproduction may be negatively affected by shade, but it plays only small role in population growth. Butterfly larvae can destroy inflorescences, and thus contribute to low effectiveness of sexual reproduction. Increasing density of shrubs and trees in peat bogs can reduce the abundance of dwarf birch, and can lead to the extinction of its local populations.     

Dynamics of <Emphasis Type="Italic">Typha domingensis</Emphasis> spread in <Emphasis Type="Italic">Eleocharis</Emphasis> dominated oligotrophic tropical wetlands following nutrient enrichment

Recent agricultural intensification in tropical countries has led to increased nutrient input and eutrophication of wetland ecosystems. Higher nutrient levels often lead to changes of vegetation structure and, eventually, shift in species dominance and loss of ecosystem services. We studied the dynamics of species shift in a manipulative nutrient enrichment experiment (+N, +P, +N&P) in oligotrophic wetlands of northern Belize distributed along a salinity gradient. We monitored spread and biomass accumulation of an introduced single individual of Typha domingensis within a 4 years period. The focus was on speed of the spreading and the relative importance of neighbouring ramets in this process. Large differences were found between control and N addition plots versus P and N&P addition plots. The ramets planted in control and N plots died or barely survived, while ramets in P and N&P plots grew vigorously and almost completely outcompeted original vegetation represented by Eleocharis spp. Final numbers of ramets were 2 and 576 per 100 m² for control and N versus P and N&P plots. The filling dynamics of P-enriched plots of differing salinity changed in time. The spreading was delayed in low salinity plots compared to high and medium salinity plots, although it finally reached comparable rates and values. We attribute this delay to originally denser vegetation and less suitable soil conditions in low salinity plots than to a direct salinity effect. Eventually, the number of ramets stabilized and often even decreased, probably due to self-thinning. Spatiotemporal model extrapolating observed vegetative spread suggested that in P-enriched conditions, a clone originating from a single individual is able to cover 1 ha plot completely within 9 years. We conclude that P-enrichment strongly increases the possibility of fast takeover of Belizean wetlands by Typha domingensis. Eventually, such species change can highly increase potential larval habitat for malaria transmitting mosquitoes.     

<Emphasis Type="Italic">Cambessedesia tiradentensis</Emphasis> (<Emphasis Type="Italic">Melastomataceae</Emphasis>), a new species from Brazil

Summary  A new and probably endemic species of Cambessedesia DC. is described from campo rupestre vegetation, as part of a floristic survey of Melastomataceae from the S?o José mountain range, Tiradentes District, Minas Gerais State, Brazil. Miscellaneous  Accepted for publication April 2008.     

Overexpression of <Emphasis Type="Italic">AP1-</Emphasis>like genes from <Emphasis Type="Italic">Asteraceae</Emphasis> induces early-flowering in transgenic <Emphasis Type="Italic">Chrysanthemum</Emphasis> plants

Chrysanthemum is one of the most important commercial cut flowers in the world. Early-flowering cultivars are required to produce quality chrysanthemum flowers with a lower cost of production. To shorten the vegetative growth phase of chrysanthemum, three AP1-like genes from Asteraceae were constitutively overexpressed in 80 independent transgenic chrysanthemum lines. All lines were characterized by PCR and RT-PCR and demonstrated that overexpression of compositae AP1-homologs in transgenic chrysanthemum under long-day conditions had no effect on plant development compared to non-transgenic controls. Conversely, under short-day conditions, transgenic plants commenced bud initiation 2 wk earlier than non-transgenic chrysanthemum plants. Subsequently, transgenic chrysanthemum flowers showed color earlier and resulted in full opening of inflorescences 3 wk prior to non-transgenic control plants. These results open new possibilities for genetic improvement and breeding of chrysanthemum cultivars.     

<Emphasis Type="Italic">Agrobacterium</Emphasis><Emphasis Type="Italic">tumefaciens</Emphasis>-mediated transformation of callus cells of <Emphasis Type="Italic">Crataegus</Emphasis><Emphasis Type="Italic">aronia</Emphasis>

A genetic transformation system has been developed for callus cells of Crataegus aronia using Agrobacterium tumefaciens. Callus culture was established from internodal stem segments incubated on Murashige and Skoog (MS) medium supplemented with 5 mg l⁻¹ Indole-3-butyric acid (IBA) and 0.5 mg l⁻¹ 6-benzyladenine (BA). In order to optimize the callus culture system with respect to callus growth and coloration, different types and concentrations of plant growth regulators were tested. Results indicated that the best average fresh weight of red colored callus was obtained on MS medium supplemented with 2 mg l⁻¹ 2,4-dichlorophenoxyacetic acid (2,4-D) and 1.5 mg l⁻¹ kinetin (Kin) (callus maintenance medium). Callus cells were co-cultivated with Agrobacterium harboring the binary plasmid pCAMBIA1302 carrying the mgfp5 and hygromycin phosphotransferase (hptII) genes conferring green fluorescent protein (GFP) activity and hygromycin resistance, respectively. Putative transgenic calli were obtained 4 weeks after incubation of the co-cultivated explants onto maintenance medium supplemented with 50 mg l⁻¹ hygromycin. Molecular analysis confirmed the integration of the transgenes in transformed callus. To our knowledge, this is the first time to report an Agrobacterium-mediated transformation system in Crataegus aronia.     

Population biology and regeneration of forbs and shrubs after fire in Brazilian <Emphasis Type="Italic">Campos</Emphasis> grasslands

Fire is an important factor in several ecosystems, affecting plant population biology. Campos grasslands are under constant influence of disturbance, mostly grazing and fire. However, few studies evaluated the effect of fire on plant population biology of grassland species. Therefore, we aim to analyze the effect of fire on the population biology of four species, from different functional groups and regeneration strategies: Chaptalia runcinata (forb, resprouter, absence of belowground organ), Vernonia flexuosa (forb, resprouter, presence of rhizophore), Eupatorium ligulaefolium (shrub, resprouter, presence of xylopodium) and Heterothalamus psiadioides (shrub, obligate seeder). Seven plots were established in different sites in southern Brazil: frequently burned (FB) and excluded from fire since 6 years (E). All plots were subjected to controlled burns during summer. Before experiments, populations were sampled. Further observations were carried out after 90 and after 360 days of fire experiments. In addition, we counted the number of seedlings and resprouters recruited after fire. Heat shock experiments were conducted with two species (H. psiadioides and V. flexuosa), as well as the study of the bud bank of the following species: E. ligulaefolium and V. flexuosa. The obligate seeder species had all individuals killed by fire and established only after 1 year. Resprouters, however, showed new stems immediately after fire. E. ligulaefolium and V. flexuosa showed only vegetative regeneration from belowground organs and more individuals in excluded sites 1 year after the fire. The bud bank of E. ligulaefolium tended to be larger in excluded sites, whilst V. flexuosa showed an opposite result. High temperatures did not enhance nor kill seeds from both studied species. Vegetative regeneration was the most important strategy for all studied species, except for H. psiadioides, the obligate seeder species. Fire thus, plays an important role on population structure and demography, being also important for plant recruitment.     

Early post-fire vegetation regeneration in <Emphasis Type="Italic">Larix kaempferi</Emphasis> artificial forests with an undergrowth of <Emphasis Type="Italic">Sasa senanensis</Emphasis>

Post-fire vegetation regeneration was studied for a 6-year period in a 13-year-old-artificial forest consisting of Larix kaempferi with a dense undergrowth of Sasa senanensis. The study site was classified into three fire severity categories according to the degree of Sasa senanensis scorching, that is, a high-severity category, a mid-severity category, and a low-severity category. Study plots were established in areas which fitted the criteria for each category, and in nearby unburned sites. A total of 41 woody species were newly emerged during the 6-year study period in the burned and unburned plots. Only a few seedlings and resprouts emerged in the unburned plots, while many seedlings emerged in the high-severity plots from the first year after fire onward. A high-severity fire that burns the rhizomes of Sasa is necessary for the vegetation recovery by germination of seed. Whereas the establishment of seedlings was restricted to a few years after fire, the regeneration through resprouting continued into the last year of observation. The survival time of resprouts was longer than that of seedlings, and the survival time of shade-tolerant species was longer than that of shade-intolerant species. In contrast, shade-intolerant species grew more rapidly than shade-tolerant species. The plants ability to exceed the maximum height of the Sasa before the bamboo recovers can be critical to the survival of shade-intolerant species. Because resprouts have a stronger resistance to the shade of Sasa than seedlings, the resprouts of shade-tolerant species play a major role in the re-establishment of woody species after fire in sites with considerable Sasa ground-cover.     

Root-promoting rhizobacteria in <Emphasis Type="Italic">Eucalyptus globulus</Emphasis> cuttings

Cloned Eucalyptus spp. plantations are based in greenhouse production of plants generated by vegetative propagation. Diverse studies have demonstrated that rhizospheric bacteria can stimulate plant growth, and more recently that they can increase rooting in vegetative material. Considering this potential, the objective of this study was to verify the effect of bacterial strains on rooting Eucalyptus globulus. A total of 132 bacterial strains isolated from the rhizosphere of E. globulus and Eucalyptus nitens were studied. The bacterial inoculums in a concentration of 4 × 10⁸ cfu/ml were applied to the rooting substrate at the cutting installation and 45 days after by irrigation. Rooting was evaluated on days 60 and 75 after cutting installation, considering the number of roots as well as their fibrosity and roots biomass. Of the 132 strains evaluated, 26 significantly increased cutting rooting in a range of 191.4–69.4% with respect to the control. Additionally, some strains stimulated the development of fine roots and incremented the roots biomass. The strains identificated that produced a rooting effect were: Bacillus firmus, Bacillus mycoides, Bacillus stearothermophilus, Bacillus subtilis, B. subtilis/amyloliquefaciens, Bacillus circulans, Brevibacillus brevis, Paenibacillus lautus and Stenotrophomona maltophilia. These first trials suggest the potential of these bacteria to be used in clonal production programs for E. globulus.     

Potential allelopathic effect of <Emphasis Type="Italic">Eucalyptus</Emphasis><Emphasis Type="Italic">grandis</Emphasis> across a range of plantation ages

Allelopathy of the eucalypt has been considered as an important mechanism for the biodiversity reduction in the eucalypt plantation. To understand the allelopathic potential of the eucalypt (Eucalyptus grandis) roots and rhizosphere soil along a chronosequence (2, 4, 6, 8, 10 years), the germination and growth characteristics of three plant species (Raphanus sativus, Phaseolus aureus, and Lolium perenne) growing nearby or beneath the eucalypt plantations were measured. The results showed that aqueous extract of E. grandis root suppressed the germination and early seedling growth of the target plants. The younger E. grandis exhibited a comparatively stronger allelopathic potential. The highest dose root extracts from 4 years old E. grandis showed the strongest inhibitory effects on the germination rates of the target species, the inhibitory rates were about 48, 51.2, and 56.56% for R. sativus, P. aureus, and L. perenne, respectively. However, present biotests of rhizosphere soils from 6, 8, and 10-year-old plantations exhibited a remarkable stimulative effect on L. perenne, which indicated that the soil might neutralize or dilute allelopathic agents with the increase of plantation age. In addition, according to GC–MS analysis, more allelopathic potential compounds were found in the rhizosphere soil and roots of younger E. grandis plantation. Moreover, more allelochemicals were obtained from soil than from roots. The allelopathic compounds in roots and rhizosphere soil may play important roles in allelopathy of E. grandis plantation. More attention should be paid to the younger E. grandis plantations for the relative higher allelopathic effects.     

Seed predation limits post-fire recruitment in the waratah (<Emphasis Type="Italic">Telopea speciosissima</Emphasis>)

Seed predation may reduce recruitment in populations that are limited by the availability of seeds rather than microsites. Fires increase the availability of both seeds and microsites, but in plants that lack a soil- or canopy-stored seed bank, post-fire recruitment is often delayed compared to the majority of species. Pyrogenic flowering species, such as Telopea speciosissima, release their non-dormant seeds more than 1 year after fire, by which time seed predation and the availability of microsites may differ from that experienced by plants recruiting soon after fire. I assessed the role of post-dispersal seed predation in limiting seedling establishment after fire in T. speciosissima, in southeastern Australia. Using a seed-planting experiment, I manipulated vertebrate access to seeds and the combined cover of litter and vegetation within experimental microsites in the 2 years of natural seed fall after a fire. Losses to vertebrate and invertebrate seed predators were rapid and substantial, with 50% of seeds consumed after 2 months in exposed locations and after 5 months when vertebrates were excluded. After 7 months, only 6% of seeds or seedlings survived, even where vertebrates were excluded. Removing litter and vegetation increased the likelihood of seed predation by vertebrates, but had little influence on losses due to invertebrates. Microsites with high-density vegetation and litter cover were more likely to have seed survival or germination than microsites with low-density cover. Recruitment in pyrogenic flowering species may depend upon the release of seeds into locations where dense cover may allow them to escape from vertebrate predators. Even here, conditions suitable for germination must occur soon after seed release for seeds to escape from invertebrate predators. Seed production will also affect recruitment after any one fire, while the ability of some juvenile and most adult plants to resprout after fire buffers populations against rapid declines when there is little successful recruitment.     

Asexual propagations of introduced exotic macrophytes <Emphasis Type="Italic">Elodea nuttallii</Emphasis>, <Emphasis Type="Italic">Myriophyllum aquaticum</Emphasis>, and <Emphasis Type="Italic">M. propinquum</Emphasis> are improved by nutrient-rich sediments in China

An increasing number of recent studies indicate that multiple interacting factors can affect the invasion of plants. However, few studies have focused on asexual propagation and the interaction of propagation with environmental factors that regulate the invasive potential of introduced exotic species in aquatic habitats. This study was designed to investigate the differences in asexual propagation between introduced exotic and non-invasive native aquatic macrophytes in nutrient-poor and nutrient-rich sediments and to test the hypothesis that differences in asexual propagation (stem fragment production) and propagule establishment between introduced exotic and non-invasive native macrophytes are driven by sediment nutrient levels. Three exotic aquatic macrophytes (Elodea nuttallii, Myriophyllum aquaticum, and M. propinquum) recently introduced to China and their non-invasive native counterparts (Hydrilla verticillata, M. oguraense, and M. ussuriense) were used for comparison in nutrient-poor (TN 0.59 and TP 0.03 mg g⁻¹) and nutrient-rich (TN 2.35 and TP 0.10 mg g⁻¹) sediments. After 8 weeks of growth, the exotic species tended to produce more total biomass, branch biomass and apical shoots and have higher relative growth rate (RGR) than their native counterparts in nutrient-rich sediment. Rooting efficiency and root growth of exotic fragments were higher than that of native counterparts in nutrient-rich sediment, although the survival rates of fragments did not differ between native and exotic species. In addition, superior traits (rooting efficiency and root growth) of exotic species were also observed in nutrient-poor sediment, but to a lesser degree than in nutrient-rich sediment. These results suggest that asexual propagation of these three introduced exotic macrophytes is more effective in nutrient-rich sediment than in nutrient-poor sediment in China.     

<Emphasis Type="Italic">Elaeocarpus</Emphasis> for <Emphasis Type="Italic">Flora Malesiana</Emphasis>: new taxa and understanding in the <Emphasis Type="Italic">Ganitrus</Emphasis> group

The Ganitrus group of Elaeocarpus L. (incl. Elaeocarpus Sect. Ptilanthus Schltr.) as found in Malesia is examined and some understanding reached. The group is more complex and speciose in eastern Malesia, especially in Papuasia (with the Philippines, Sulawesi and Maluku somewhat less rich) than in western and central Malesia. E. angustifolius Blume (syn. E. ganitrus & E. sphaericus auctt. mult.) — the source of the ornamental beads known as rudraksha of eastern commerce, from which malas or rosaries are made — is considered to be very variable in Malesia and probably varies further in the extremes of its range; outside Malesia the Ganitrus group is represented by ‘E. angustifolius s.l.’ only. The following species are recognised: E. altisectus Schltr. with a new subsp. carrii Coode from New Guinea; E. angustifolius Blume; E. avium Coode sp. nov. from New Guinea; E. buderi Coode; E. dolichostylus Schltr. with E. chloranthus treated as var. chloranthus (A. C. Sm.) Coode from New Guinea, with a new var. elliptifolius Coode from the Talaud/Sangihe Is. and a new var. hentyi Coode (replacing and re-interpreting subsp. collinus Coode) from New Guinea; E. fulvus Elmer; E. kaniensis Schltr.; E. ornatus Coode sp. nov. from New Guinea; E. osiae Coode sp. nov. from Bougainville I.; E. ptilanthus Schltr.; E. ramiflorus Merr. and E. trichopetalus Merr. & Quisumb. — a total of 12 species although the last two are perhaps not truly distinct from E. angustifolius. The stone sculpturing is discussed and some useful characters revealed. Attention is drawn to a collection from mid-altitude in Papua New Guinea, inadequately known but probably a new species in this group.