Afforestation causes changes in post‐fire regeneration in native shrubland communities of northwestern Patagonia,Argentina

Question: What are the effects of fire in native shrubland communities and in pine plantations established in these shrublands? Location: Northern Patagonia, Argentina. Methods: We surveyed four sites in Chall‐Huaco valley, located in northwest Patagonia. Each site was a vegetation mosaic composed of an unburned Pinus ponderosa plantation, a plantation burned in 1996, and an unburned matorral and a matorral burned by the same fire. We recorded the cover of all vascular plant species. We also analysed species richness, total cover, proportion of exotic species, abundance of woody species and herb species, cover of exotic species, abundance of woody and herb species and differences in composition of species. For both shrubs and tree species we recorded the main strategy of regeneration (by resprouting or by seed). Results: We found that fire had different effects on native matorral and pine plantations. Five years after fire, plantations came to be dominated by herbs and exotic species, showing differences in floristic composition. In contrast, matorral communities remained very similar to unburned matorral in terms of species richness, proportion of woody species, and herb species and proportion of exotics. Also, pine plantations were primarily colonized by seedlings, while matorrals were primarily colonized by resprouting. Conclusions: Matorrals are highly fire resilient communities, and the practice of establishing plantations on matorrals produces a strong reduction in the capacity of matorral to return to its original state. The elimination of shrubs owing to the effect of plantations can hinder regeneration of native ecosystems. Burned plantations may slowly develop into ecosystems similar to the native ones, or they may produce a new ecosystem dominated by exotic herbs. This study shows that plantations of exotic conifers affect native vegetation even after they have been removed, as in this case by fire.     

Fire‐related cues break seed dormancy of six legumes of tropical eucalypt savannas in north‐eastern Australia

Abstract This paper describes an assessment of the effect of exposure to fire‐related cues (heat shock, smoke and nitrate) and the interactions between the cues on seed dormancy release of tropical savanna legumes in north‐eastern Australia. Ten legume species were tested, comprising both native and exotic species. The ten species responded variously to the treatments. Brief exposure to temperatures between 80 and 100°C was found to break the seed dormancy of the native ephemeral herbs Chamaecrista mimosoides, Crotalaria calycina, Crotalaria montana, Indigofera hirsuta and Tephrosia juncea, as well as the exotic ephemeral herb Crotalaria lanceolata. Exposure to 80°C combined with treatment with a nitrate solution produced an additive effect on the germination of Chamaecrista mimosoides and Crotalaria lanceolata. However, the four species with the heaviest seeds, two exotic ephemeral herbs (Chamaecrista absus and Crotalaria pallida) and two native perennials (Galactia tenuiflora and Glycine tomentella) displayed no significant increase in germination with exposure to fire‐related cues. Exposure to 120°C for 5 min produced seed mortality in all species tested. Two of the largest seeded species, Crotalaria pallida and Galactia tenuiflora, displayed the lowest tolerance to heat shock, with seed mortality after exposure to 100°C for 5 min. These data indicate that fire can promote the germination of some tropical savanna legumes. As a proportion of seeds of each species displayed no innate dormancy, some germination may occur in the absence of fire, especially of exotic species.     

Unique Carotenoids in the Terrestrial Cyanobacterium <Emphasis Type="Italic">Nostoc commune</Emphasis> NIES-24: 2-Hydroxymyxol 2′-Fucoside,Nostoxanthin and Canthaxanthin

Cyanobacteria produce some carotenoids. We identified the molecular structures, including the stereochemistry, of all the carotenoids in the terrestrial cyanobacterium, Nostoc commune NIES-24 (IAM M-13). The major carotenoid was β-carotene. Its hydroxyl derivatives were (3R)-β-cryptoxanthin, (3R,3′R)-zeaxanthin, (2R,3R,3′R)-caloxanthin, and (2R,3R,2′R,3′R)-nostoxanthin, and its keto derivatives were echinenone and canthaxanthin. The unique myxol glycosides were (3R,2′S)-myxol 2′-fucoside and (2R,3R,2′S)-2-hydroxymyxol 2′-fucoside. This is only the second species found to contain 2-hydroxymyxol. We propose possible carotenogenesis pathways based on our identification of the carotenoids: the hydroxyl pathway produced nostoxanthin via zeaxanthin from β-carotene, the keto pathway produced canthaxanthin from β-carotene, and the myxol pathway produced 2-hydroxymyxol 2′-fucoside via myxol 2′-fucoside. This cyanobacterium was found to contain many kinds of carotenoids and also displayed many carotenogenesis pathways, while other cyanobacteria lack some carotenoids and a part of carotenogenesis pathways compared with this cyanobacterium.     

Developmental and environmental regulation of soybean <Emphasis Type="Italic">SE60</Emphasis> gene expression during embryogenesis and germination

Soybean SE60 belongs to the γ-thionin family of proteins. We recently demonstrated that SE60 plays a role in defense during soybean development. Here, we show that SE60 is expressed in a tissue-specific and developmentally regulated manner. The expression of SE60 is distinct from that of the glycinin (Gy2) and extensin (SbHRGP3) genes of soybean during embryogenesis and germination. A SE60::GUS(−809) transgene, comprising −809 bp of the 5′-flanking region of SE60 fused to the GUS reporter gene, was expressed specifically in developing embryos, but not in the endosperms, from the globular stage of transgenic tobacco and Arabidopsis seeds. Furthermore, light affected the SE60::GUS(−809) expression pattern in germinating seedlings. Electrophoretic mobility shift assay (EMSA) revealed that soybean nuclear proteins as well as E. coli-expressed SB16, a high mobility group protein (HMG), were bound sequence-specifically to the fragment containing AT-rich motifs identified in the SE60 promoter. Interestingly, the soybean nuclear proteins binding to the two G-boxes and RY repeat were prevalent in seeds of 2–4 mm in size. In contrast, the nuclear proteins binding to the AT-rich motif and SE60 RNA expression were more prominent in seeds of 4–6 mm in size. Therefore, we propose that factors binding to the G-boxes or RY repeat initiate SE60 expression during embryogenesis.     

A new genus of <Emphasis Type="Italic">Monimiaceae</Emphasis> from the Atlantic Coastal Forest in South-Eastern Brazil

Summary  A new monotypic genus and a new species of Monimiaceae, Grazielanthus arkeocarpus from the Brazilian Atlantic coastal forest are described, illustrated and compared with morphologically related taxa. The new taxon occurs in the State of Rio de Janeiro in the central coastal plain and was collected in the Po?o das Antas Biological Reserve, municipality of Silva Jardim (22°30′– 22°33′S; 42°14′– 42°19′W). The new taxon is represented by dioecious climbing shrubs of the sub-canopy that have urceolate, four-lobed flowers and a fleshy hypanthium that is closed until the fruit ripens. When ripe, the hypanthium ruptures irregularly and the fruitlets are exposed. The relationships between the new genus and other neotropical (Hennecartia J. Poiss. and Macrotorus Perkins) and paleotropical (Palmeria F. Muell.) genera are discussed.     

Population- and sociogenetic structure of the leaf-cutter ant <Emphasis Type="Italic">Atta colombica</Emphasis> (Formicidae,Myrmicinae)

Relatedness and genetic variability in colonies of social insects are strongly influenced by the number of queens present and the number of matings per queen, but also by the genetic variability in the population. Thus, multiple paternity will enhance within-colony genetic variability more strongly when the males a queen mates with are unrelated. To study the kin-structure within colonies of the leaf-cutter ant Atta colombica and the population structure of this species around Barro Colorado Island, Panama, we developed five polymorphic microsatellite loci with a range of three to 17 alleles in At. colombica, all of which cross-amplify in other higher attines as well. The average effective mating frequency calculated from four-locus microsatellite genotypes was 1.89 ± 0.12 (harmonic mean ± SE) and thus slightly lower than the average observed mating frequency of 2.50 ± 0.11 (arithmetic mean ± SE) over the 55 colonies studied, confirming former studies that utilized fewer loci. The discrepancy between observed mating frequency and effective mating frequency is most probably due to paternity skew within colonies. The study population proved to be genetically diverse and in Hardy-Weinberg equilibrium, suggesting random mating within the study area. No population substructure was observed, neither considering nuclear (global F _ST = 0.011 ± 0.003 SE) nor mitochondrial markers (mean Φ_ST = 0.008). Consequently, gene flow is obviously promoted by both sexes across the range investigated here. Thus, multiple mating and long-distance dispersal appear to be two interconnected behavioural mechanisms to create and maintain genetic diversity in At. colombica. The advantages of this system are partly offset by paternity skew and the non-zero relatedness among colony fathers found in the study population. Received 18 March 2008; revised 14 July 2008; accepted 18 July 2008.     

The effects of copper on the photosynthetic response of <Emphasis Type="Italic">Phaeocystis cordata</Emphasis>

We investigated the effects of limiting (1.96 × 10⁻⁹ mol l⁻¹ total Cu, corresponding to pCu 14.8; where pCu = −log [Cu²⁺]) and toxic Cu concentrations up to 8.0 × 10⁻⁵ mol l⁻¹ total Cu (equivalent to pCu 9.5) on growth rates and photosynthetic activity of exponentially grown Phaeocystis cordata, using batch and semi-continuous cultures. With pulse amplitude modulated (PAM) fluorometry, we determined the photochemical response of P. cordata to the various Cu levels, and showed contrasting results for the batch and semi-continuous cultures. Although maximum photosystem II (PSII) quantum yield (Φ_M) was optimal and constant in the semi-continuous P. cordata, the batch cultures showed a significant decrease in Φ_M with culture age (0–72 h). The EC50 for the batch cultures was higher (2.0 × 10⁻¹⁰ mol l⁻¹, pCu9.7), than that for the semi-continuous cultures (6.3 × 10⁻¹¹ mol l⁻¹, pCu10.2). The semi-continuous cultures exhibited a systematic and linear decrease in Φ_M as Cu levels increased (for [Cu²⁺] < 1.0 × 10⁻¹² mol l⁻¹, pCu12.0), however, no effect of high Cu was observed on their operational PSII quantum yield (Φ′_M). Similarly, semi-continuous cultures exhibited a significant decrease in Φ_M, but not in Φ′_M, because of low-Cu levels. Thus, Cu toxicity and Cu limitation damage the PSII reaction centers, but not the processes downstream of PSII. Quenching mechanisms (NPQ and Q _n) were lower under high Cu relative to the controls, suggesting that toxic Cu impairs photo-protective mechanisms. PAM fluorometry is a sensitive tool for detecting minor physiological variations. However, culturing techniques (batch vs. semi-continuous) and sampling time might account for literature discrepancies on the effects of Cu on PSII. Semi-continuous culturing might be the most adequate technique to investigate Cu effects on PSII photochemistry.     

Restoring restoration: removal of the invasive plant <Emphasis Type="Italic">Microstegium vimineum</Emphasis> from a North Carolina wetland

Restoration sites are vulnerable to plant invasions due to habitat and resource alteration. We conducted an invasive plant-removal study at a wetland restoration in the North Carolina Piedmont, a site dominated by the non-native invasive, Microstegium vimineum. Paired plots (M. vimineum hand-weeded and unweeded) were established and maintained to monitor response of plant species richness and diversity. Plots increased from 4 to 15 species m⁻² after three growing seasons of M. vimineum removal and 90% of the newly establishing species were native. Weeding ceased in the fourth growing season and M. vimineum rapidly re-invaded. Formerly weeded plots increased to 59% (±11% SE) M. vimineum cover, 25 of 51 plant species disappeared from the plots, and species richness decreased to an average of <8 species m⁻². Our results show that we can quickly establish an abundant, diverse community with invasive removal, but that persistent effort is required to monitor and maintain the long-term viability of this community.     

Transition zones in small lakes: the importance of dilution and biological uptake on lake-wide heterogeneity

Community structure and diversity patterns of pelagic copepods were investigated for the coastal areas and in the marine lakes of the Palau islands in the West Pacific. We conducted field surveys during 2004–2007 and collected zooplankton samples from eight coastal areas and 16 marine lakes. The marine lakes in the islands of Palau are limnologically classified into two types, meromictic and holomictic lakes. Species diversity indices (Margalef’s species richness d′, Shannon–Wiener index H′, and Simpson’s dominance) were measured at each sampling site. The copepod community structure was analyzed using multivariate analyses, hierarchical cluster analysis, and non-metric multidimensional scaling (MDS) from the PRIMER package. A total of 36 copepod taxa were identified to the genus or species level from Calanoida, Cyclopoida, Harpacticoida, and Poecilostomatoida. Multivariate analysis based on the Bray–Curtis similarity index revealed that copepod assemblages could be classified into three different groups according to their habitat: (I) meromictic lakes, (II) holomictic lakes with an exceptionally shallow and flat basin (type A holomictic lakes), (III) holomictic lakes with a deep basin (type B holomictic lakes), and all coastal areas. The meromictic lakes were characterized by markedly decreased species diversity (d′ = 0.15, H′ = 0.41) in which only two brackish-water species, Bestiolina similis and Oithona dissimilis, were dominant. Type A holomictic lakes were characterized by relatively low levels of species diversity (d′ = 1.25, H′ = 1.35). In contrast, type B holomictic lakes were characterized by relatively high levels of species diversity, which was comparable to that of coastal areas. This result indicated that zooplankton assemblages in the type B holomictic lakes were closely related to a coastal community. The present study showed that the species diversity of pelagic copepods varies according to the level of isolation and the local environmental conditions for each marine lake.     

Stand stratification and woody species diversity of a subtropical forest in limestone habitat in the northern part of Okinawa Island

Stand stratification and woody species diversity were studied in a subtropical forest in limestone habitat in the northern part of Okinawa Island, Japan. The forest stand consisted of four architectural layers. Cinnamomum japonicum Sieb. was the most dominant species as it had the highest importance value in all layers, especially in the lower three layers. Although Rhus succedanea L. was a major top-layer species, it might disappear because of its absence in the lower two layers. The lower two layers had similar floristic composition, while the composition of the top layer differed greatly from that of the lower two layers. The value of H′ in each layer increased from the bottom to the second layer and then decreased, and the value of J′ in each layer consistently increased from the bottom layer upward. The values of Shannon’s index H′ and Pielou’s index J′ were 4.27 bit and 0.74, respectively, at the stand level. The trends of H′ and J′ based on the cumulative height range from the top layer downward were, respectively, the same as those in each layer for the present forest in limestone habitat. However, these trends were opposite from those of a nearby subtropical forest in silicate habitat, where the values of H′ and J′ based on the cumulative height range decreased steadily from the bottom layer upward.     

Qualitative Traits Variation in Sorghum (<Emphasis Type="Italic">Sorghum Bicolor</Emphasis> (L.) Moench) Germplasm from,Eastern Highlands of Ethiopia

Forty-five sorghum germplasm growing in the Eastern Highlands of Ethiopia were evaluated for 10 qualitative traits. Phenotypic frequencies between the accessions from each of the nine Aanaas and Alemaya University, grouped in 10 localities were tabulated. Phenotypic diversity index, H′, was analysed and the result indicated the between localities component of diversity to be relatively smaller than the variation in H′ among characters within localities. The value of H′ for all sample germplasm ranged from 0.36 to 0.95 with a mean of 0.71. The results showed that there is a wide morpho-agronomical diversity among the sample germplasm studied. This information can be used for the conservation of these germplasm resources and future improvement work of the sorghum crop.     

Biotransformation of soybean isoflavones by a marine <Emphasis Type="Italic">Streptomyces</Emphasis> sp. 060524 and cytotoxicity of the products

A marine Streptomyces sp. 060524 capable of hydrolyzing the glycosidic bond of isoflavone glycosides, was isolated by detecting its β-glucosidase activity. 5 isoflavone aglycones were isolated from culture filtrates in soybean meal glucose medium. They were identified as genistein (1), glycitein (2), daidzein (3), 3′,4′,5,7-tetrahydroxyisoflavone (4), and 3′,4′,7-trihydroxyisoflavone (5), based on UV, NMR and mass spectral analysis. The Streptomyces can selectively hydroxylate at the 3′-position in the daidzein and genistein to generate 3′-hydroxydaidzein and 3′-hydroxygenistein, respectively. The Strain biotransformed more than 90% of soybean isoflavone glycosides into their aglycones within 108 h. 3′-hydroxydaidzein and 3′-hydroxygenistein exhibited stronger cytotoxicity against K562 human chronic leukemia than daidzein and genistein.     

Cloning and sequence diversity analysis of <Emphasis Type="Italic">GmHs1</Emphasis><Superscript><Emphasis Type="Italic">pro-1</Emphasis></Superscript> in Chinese domesticated and wild soybeans

Soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) is the most important pathogen in soybean production worldwide and causes substantial yield losses. An apparent narrow genetic base of SCN resistance was observed in current elite soybean cultivars, and searching for novel SCN resistance genes as well as novel resistance sources rather than focusing on the two important genes rhg1 and Rhg4 has become another major objective in soybean research. In the present paper we report a 1,477 bp Hs1 ^pro-1 homolog, named GmHs1 ^pro-1 . This gene was cloned from soybean variety Wenfeng 7 based on information for Hs1 ^pro-1 , a beet cyst nematode resistance gene in sugar beet. It has two domains, Hs1pro-1_N and Hs1pro-1_C, both of which are believed to confer resistance to nematodes. Of the 1,477 bp sequence in GmHs1 ^pro-1 , an open reading frame of 1,314 bp, encoding a protein with 437 amino acids, was flanked by a 5′-untranslated region of 27 bp and a 3′-untranslated region of 135 bp. Fourteen single-nucleotide polymorphisms (SNPs) were observed in 44 soybean accessions including 23 wild soybeans, 8 landraces, and 13 soybean varieties (or lines), among which 5 in wild soybeans and 3 in landrace accessions were unique. Sequence diversity analysis on the 44 soybean accessions showed π = 0.00168 and θ = 0.00218 for GmHs1 ^pro-1 ; landraces had the highest diversity, followed by wild soybeans, with varieties (or lines) having the lowest. Although we did not detect a significant effect of selection on GmHs1 ^pro-1 in the three populations, sequence diversity, unique SNPs, and phylogenetic analysis indicated a slight domestication bottleneck and an intensive selection bottleneck. High sequence diversity, more unique SNPs, and broader representation across the phylogenetic tree in wild soybeans and landraces indicated that wild collections and landrace accessions are invaluable germplasm for broadening the genetic base of elite soybean varieties resistant to SCN. C. Yuan and G. Zhou contributed to this paper equally.     

Genetic variability in relocated Père David’s deer (<Emphasis Type="Italic">Elaphurus davidianus</Emphasis>) populations—Implications to reintroduction program

Since 1985, China has established three breeding herds of Père David’s deer: the Beijing Père David’s Deer Park (39°07′N, 116°03′E), the Dafeng Père David’s Deer Nature Reserve (33°05′N, 120°49′E) and Shishou (Tianezhou) Père David’s Deer Nature Reserve (29°49′N, 112°33′E), through reintroductions of about 30–40 founders. Since establishment, all three populations have grown steadily. However, genetic backgrounds in those populations are still unknown. We studied the genetic diversity in Père David’s deer and genetic consequences of population relocations in China. We revealed that genetic diversity was extremely low in Père David’s deer populations in China. Only a single mtDNA D-loop haplotype was found in the deer, furthermore, only five polymorphic microsatellite loci were screened out from 84 pairs of species-transferred primers. Genetic makeup in the three Père David’s deer populations were significantly different (P < 0.01). H _E and allelic richness in the Tianezhou population were the highest (0.54, 2.60, n = 31), Beijing population (0.52, 2.4, n = 125) showed the second highest measures, while the Dafeng population (0.46, 2.39, n = 39) measured lowest. Our results suggest that effective management of a species of low genetic diversity like the Père David’s deer should consider the genetic background of each founder to make sure genetic variations are preserved in both source population and relocated population. Now, the Tianezhou population is the most appropriate source population in China when establishing new Père David deer populations in the wild.

Does biofouling influence <Emphasis Type="Italic">Kappaphycus alvarezii</Emphasis> (Doty) Doty ex Silva farming production in Brazil?

The commercial cultivation of Kappaphycus alvarezii is the main source of raw material for the carrageenan industry. Brazilian commercial farming uses floating rafts that serve as substrata for fouling organisms that may affect production of the carrageenophyte seedlings. The aim of this work was to identify and quantify the biofouling on floating rafts at Sepetiba Bay, Rio de Janeiro State (23° 02′ 25″ S and 43° 53′ 39″ W), and to evaluate seedling damage caused by epibionts and endobionts. Samples were collected from August 2006 to August 2007. In each assessment, organisms contained in random sampling areas of 18 quadrats of 0.10 m² (n = 18) were removed from floating rafts. K. alvarezii seedling samples were collected to verify the presence of epibionts or endobionts (n = 30). Twenty-four taxa belonging to seven groups of animals and three groups of seaweed were found. The percentage occurrence estimated 13 dominant organisms and amphipod tubes: e.g., Chondracanthus tedii, Cladophora vagabunda, Gracilariopsis tenuifrons, Hypnea spinella, Hypnea musciformis, Hincksia mitchelliae, Spyridia spp., Ulva spp., Bowerbankia sp., Bugula neritina, Botryllus sp., Haplosclerida sp., and Perna perna. Richness, equitability, diversity, and total biomass varied significantly during the study period (p < 0.001). There was a tendency for higher biomass values in August 2007. After 6 months, epibionts (i.e., Chlorophyta, Rhodophyta, Chordata, Cnidaria and Ectoprocta) were found on K. alvarezii seedlings. Endobionts were not found in this study. The biofouling biomass was not found to have a significant effect on K. alvarezii daily growth rate, carrageenan yield, or quality (gel strength and viscosity; p > 0.05).     

<Superscript>1</Superscript>H NMR-based metabolic profiling and target analysis: a combined approach for the quality control of <Emphasis Type="Italic">Thymus vulgaris</Emphasis>

The characterization of T. vulgaris plant material for quality control purposes was performed by NMR-based methods. Direct extraction of 141 T. vulgaris samples with DMSO-d ₆ enabled the obtainment of crude extracts with a representative composition in terms of both volatile and non-volatile constituents. The acquisition of 600 MHz ¹H NMR spectra resulted in a dataset which was analyzed by a combination of metabolic profiling and target analysis approaches. Preliminary analysis of the ¹H NMR spectra was performed by principal component analysis, which revealed sample discrimination on a chemotype basis (thymol, carvacrol and linalool chemotypes). Further minor discriminative constituents were identified as p-cymene, γ-terpinene, rosmarinic acid, and 3,4,3′,4′-tetrahydroxy-5,5′-diisopropyl-2,2′-dimethylbiphenyl. Metabolite identification was accomplished by 1D and 2D NMR techniques and supported by spiking experiments. Fast dereplication of constituents not available as reference compounds was performed by HPLC–SPE–NMR experiments. A targeted approach based on qHNMR was validated for quantification of the identified secondary metabolites. Validation was performed in terms of precision (intra-day RSD ≤ 4.51%, inter-day RSD ≤ 4.18%), repeatability (RSD ≤ 2.30%), accuracy (recovery rates within 93.4 and 103.4%), linearity (correlation coefficients ≥ 0.9990), robustness, and stability. The amount of the dominant monoterpene in thymol, carvacrol, and linalool chemotypes was respectively found to be within 0.4–2.6, 0.7–2.3, and 1.1–3.6% (w/w). Variable amounts of the precursors p-cymene and γ-terpinene were found in thymol and carvacrol chemotypes. The highest amount of rosmarinic acid and 3,4,3′,4′-tetrahydroxy-5,5′-diisopropyl-2,2′-dimethylbiphenyl in the analyzed samples was respectively 4.6 and 0.4% (w/w). Since quantification is performed on a weight basis, the essential oil content can be estimated based on the sum of the quantified monoterpenes. The NMR-based analysis of T. vulgaris represents a more comprehensive approach in comparison to traditional chromatographic methods such as GC and LC, respectively employed for the analysis of volatile and non-volatile constituents. Further advantages lie in the simple sample preparation, rapidity and reproducibility of the NMR analysis.     

An exotic Australian <Emphasis Type="Italic">Acacia</Emphasis> fixes more N than a coexisting indigenous <Emphasis Type="Italic">Acacia</Emphasis> in a South African riparian zone

Acacia mearnsii is an introduced Australian acacia in South Africa and has invaded more than 2.5 million ha, primarily establishing in rangeland and riparian areas. Because acacias have the capability to fix N, A. mearnsii invasions may fundamentally change N dynamics in invaded systems. This study compares biological N₂-fixation in the alien invasive A. mearnsii and the native A. caffra growing in a grassland riparian zone in the Komati Gorge Reserve, Mpumalanga, South Africa. A ¹⁵N natural abundance field survey suggested that both mature alien and native acacias fix N under current conditions in the riparian zone. Significantly depleted δ¹⁵N was observed in both acacias relative to reference species, although variation in δ¹⁵N was not correlated with N concentrations. Calculated contributions of N₂-fixation (%Ndfa) suggest that alien acacias fix significantly more of their N than native acacias (~75 ± 5% SE and 53 ± 9% SE, respectively). There was a larger variation in δ¹⁵N and %Ndfa in the native acacia, suggesting relatively high plasticity in its N₂-fixation contributions. This plasticity was interpreted as a facultative N₂-fixation strategy for the native acacia, while the N₂-fixation strategy of the alien acacia remained unclear. Our results emphasize the importance of potentially elevated N inputs through N₂-fixation by invasive legumes in invaded landscapes. Furthermore, they suggest that N₂-fixation by invasive acacias may not respond to fine-scale patchiness in soil N in the same manner as native acacias, making them potential contributors to N excess in Southern Africa.     

Niche separation between <Emphasis Type="Italic">Encarsia dispersa</Emphasis> and <Emphasis Type="Italic">Encarsia guadeloupae</Emphasis>, two biological control agents of the spiraling whitefly <Emphasis Type="Italic">Aleurodicus dispersus</Emphasis>, in Benin,West Africa

The spiraling whitefly Aleurodicus dispersus (Russell) is an insect pest that causes substantial damage to ornamental plants, shade trees and food crops. It was first observed in Benin in 1993. Two host specific parasitoids, Encarsia dispersa and E. guadeloupae, fortuitously introduced with its host, were recovered in the second half of 1993 in Southern Benin. Survey results from 1993 to 1995 (already published) showed the decline in the population of A. dispersus due to the parasitoids, and the spread from Cotonou (6°10′N) in a northern directions of both parasitoids and their host. Results from similar field surveys from 1996 to 2003 document that the spiraling whitefly and both its parasitoids spread to Natitingou (10°20′N, 540 km) in 1995 and Bembereke (10°14′N) in 1996, whereby E. dispersa arrived within less than a year of its host and quickly became dominant in the two localities on the northern front. In subsequent years, the parasitoids established their geographical niches, with E. dispersa being more abundant (up to 89%) in the coastal south bellow latitude 7°30′N and E. guadeloupae (up to 84%) in the north between latitudes 7°30′ and 10°30′N. We conclude that the gradual replacement observed over ten years and over 500 km has to do with longitudinal shifts in the length and severity of the dry season and the higher susceptibility to these conditions by E. dispersa.     

Animal species diversity at a land–water ecotone in Mongolia

The biodiversity of wetland ecosystems has received scant attention in Mongolia. We measured amphibian and macroinvertebrate species diversity at a complicated land–water ecotone of a pond within a wetland complex in Shaamar during July 2005. From our study area (0.5-ha grassland and an adjacent pond), we sampled 4,926 animals including 1 mammal, 4 amphibian, and 26 aquatic macroinvertebrate (>2 mm) species with a biomass of 4,444 g. Among these, a backswimmer (Notonectidae sp. 1) was a dominant species, representing 65% of the total number of animals collected (3,209) and 22% of the mass (999 g). Our study area was small but contained 4 amphibian species (Hyla japonica, Rana amurensis, Bufo raddei, and Salamandrella keyserlingii) in a mixed community with Shannon Diversity Index (H′) of 1.678 and Pielou’s Evenness Index (J′) of 1.211. No larvae or tadpoles of any amphibian species were found in the pond, indicating their early metamorphosis. H′ and J′ with 26 macroinvertebrate species were estimated to be 1.828 and 0.561, respectively. This suggests that low macroinvertebrate species diversity relative to high species richness is due to low evenness resulting from considerable numbers of a backswimmer. In 6 sites sampled in the pond, mean water pH revealed high alkalinity (range 9.01–10.45). The presence of our taxa in a highly alkaline environment indicates that they may be alkaliphilic.