Fungal-feeding habits of six nematode isolates in the genus Filenchus

The family Tylenchidae is a large group of soil nematodes but their feeding habits are not fully known. We studied the fungal-feeding abilities of nematodes in the genus Filenchus. We measured population growth rates (PGRs) of six nematode isolates, representing three Filenchus species, when feeding on seven fungal species on two types of culture media. On Potato Dextrose Agar (PDA) Filenchus misellus, Filenchus discrepans and an unidentified Filenchus sp. generally showed moderate to large PGRs on saprophytic fungi (Rhizoctonia solani, Chaetomium globosum, Coprinus cinereus, Flammulina velutipes) and low PGRs on plant-pathogenic fungi (Fusarium oxysporum, Pythium ultimum). In soil medium amended with chopped soybean plant material or wheat bran, the status of most of the fungi as food for the nematodes was similar to that on PDA, although PGRs tended to be lower in the soil medium. However, C. globosum, a good food on PDA, only supported low PGR in soil for each of the three nematodes. The PGRs of F. misellus on C. globosum in soil were still low even when types and amounts of organic matter amendments were varied. A nematophagous fungus, Pleurotus ostreatus (oyster mushroom), was determined to be a food for Filenchus on PDA or in soil, based on PGR measurements corrected for extraction efficiency. To determine whether fungal species and culture media affected nematode extraction efficiencies and, consequently, the apparent PGRs, we compared efficiencies between R. solani, C. globosum and C. cinereus, and between PDA and soil. The relatively low extraction efficiencies across fungal species in soil seemed responsible for the lower nematode PGRs in soil than on PDA. On PDA generally, fungal species did not affect the assessment. In soil, effects of fungal species on extraction were significant, but not consistent, across nematode species. Nevertheless, the extraction efficiency differences in soil were considered not to affect assessment of the three fungi as food for the nematodes. The confirmation that three Filenchus species reproduce by feeding on fungi in soil suggests that fungal-feeding is not an unusual habit in the field, in this genus. We believe that in community studies, nematodes in the genus Filenchus should be considered fungal feeders or root and fungal feeders, rather than only plant feeders. Our confirmation of fungal-feeding habits in the genus Filenchus supports the hypotheses that plant-feeding nematodes evolved from those feeding on fungi.     

Pre-symbiotic and symbiotic interactions between Glomus intraradices and two Paenibacillus species isolated from AM propagules. In vitro and in vivo assays with soybean (AG043RG) as plant host

Two indole-producing Paenibacillus species, known to be associated with propagules of arbuscular mycorrhizal (AM) fungi, were examined for their mycorrhization helper bacteria activity at pre-symbiotic and symbiotic stages of the AM association. The effects were tested under in vitro and in vivo conditions using an axenically propagated strain of the AM fungus Glomus intraradices and Glycine max (soybean) as the plant host. The rates of spore germination and re-growth of intraradical mycelium were not affected by inoculation with Paenibacillus strains in spite of the variation of indole production measured in the bacterial supernatants. However, a significant promotion in pre-symbiotic mycelium development occurred after inoculation of both bacteria under in vitro conditions. The Paenibacillus rhizosphaerae strain TGX5E significantly increased the extraradical mycelium network, the rates of sporulation, and root colonization in the in vitro symbiotic association. These results were also observed in the rhizosphere of soybean plants grown under greenhouse conditions, when P. rhizosphaerae was co-inoculated with G. intraradices. However, soybean dry biomass production was not associated with the increased development and infectivity values of G. intraradices. Paenibacillus favisporus strain TG1R2 caused suppression of the parameters evaluated for G. intraradices during in vitro symbiotic stages, but not under in vivo conditions. The extraradical mycelium network produced and the colonization of soybean roots by G. intraradices were promoted compared to the control treatments. In addition, dual inoculation had a promoting effect on soybean biomass production. In summary, species of Paenibacillus associated with AM fungus structures in the soil, may have a promoting effect on short term pre-symbiotic mycelium development, and little impact on AM propagule germination. These findings could explain the associations found between some bacterial strains and AM fungus propagules.     

Dispersal patterns and behaviour of the nematode Phasmarhabditis hermaphrodita in mineral soils and organic media

The commercially available parasitic nematode Phasmarhabditis hermaphrodita is an effective biocontrol agent for slugs and particularly Deroceras reticulatum, a widespread pest species. Use of the nematode is currently limited by cost and it may be that by developing a fuller understanding of the ecology and behaviour of this nematode, more cost effective application strategies can be developed. We investigated the ability of two strains of P. hermaphrodita (one newly isolated and one that had been maintained in vitro for >15 years) to move through mineral soils and organic media. Active dispersal of both strains was found to be greatest in organic media (bark chips and leaf litter, and to a lesser extent peat) and the nematode was capable of growth and reproduction in leaf litter. Conversely, active dispersal was poor in mineral soils. Nematodes moved further in a clay loam compared with a sandy loam, and moved more at a bulk density of 1.0 vs. 1.2 Mg m⁻³. However, P. hermaphrodita was capable of moving greater distances in mineral soils by using the earthworm Lumbricus terrestris as a phoretic host. Our data suggest that P. hermaphrodita is a facultative parasite that is adapted to living in leaf litter and organic material where slugs frequently rest. The implications of these findings for using the nematode as a biological control agent for slugs are discussed.     

Screening of bacterial isolates from various European soils for in vitro antagonistic activity towards Rhizoctonia solani and Fusarium oxysporum: Site-dependent composition and diversity revealed

A cultivation-based approach was used to determine the in vitro antagonistic potential of soil bacteria towards Rhizoctonia solani AG3 and Fusarium oxysporum f. sp. lini (Foln3). Four composite soil samples were collected from four agricultural sites with previous documentation of disease suppression, located in France (FR), the Netherlands (NL), Sweden (SE) and the United Kingdom (UK). Similarly, two sites from Germany (Berlin, G-BR; and Braunschweig, G-BS) without documentation of disease suppression were sampled. Total bacterial counts were determined by plating serial dilutions from the composite soil samples onto R2A, AGS and King's B media. A total of 1,788 isolates (approximately 100 isolates per medium and site) was screened for antifungal activity, and in vitro antagonists (327 isolates) were found amongst the dominant culturable bacteria isolated from all six soils. The overall proportion of antagonists and the number of isolates with inhibitory activity against F. oxysporum were highest in three of the suppressive soils (FR, NL and SE). Characterization of antagonistic bacteria revealed a high phenotypic and genotypic diversity. Siderophore and protease activity were the most prominent phenotypic traits amongst the antagonists. The composition and diversity of antagonists in each soil was site-specific. Nevertheless, none of the antimicrobial traits of bacteria potentially contributing to soil suppressiveness analyzed in this study could be regarded as specific to a given site.     

Growth promoting effects of corn (Zea mays) bacterial isolates under greenhouse and field conditions

Fertilizer costs are a major component of corn production. The use of biofertilizers may be one way of reducing production costs. In this study we present isolation and identification of three plant growth promoting bacteria that were identified as Enterobacter cloacae (CR1), Pseudomonas putida (CR7) and Stenotrophomonas maltophilia (CR3). All bacterial strains produced IAA in the presence of 100 mg l⁻¹ of tryptophan and antifungal metabolites to several soilborne pathogens. S. maltophilia and E. cloacae had broad spectrum activity against most Fusarium species. The only strain that was positive for nitrogen fixation was E. cloacae and it, and P. putida, were also positive for phosphate solubilization. These bacteria and the corn isolate Sphingobacterium canadense CR11, and known plant growth promoting bacterium Burkholderia phytofirmans E24 were used to inoculate corn seed to examine growth promotion of two lines of corn, varieties 39D82 and 39M27 under greenhouse conditions. When grown in sterilized sand varieties 39M27 and 39D82 showed significant increases in total dry weights of root and shoot of 10-20% and 13-28% and 17-32% and 21-31% respectively. Plants of the two varieties grown in soil collected from a corn field had respective increases in dry weights of root and shoot of 10-30% and 12-35% and 11-19% and 10-18%. In sand, a bacterial mixture was highly effective whereas in soil individual bacteria namely P. putida CR7 and E. cloacae CR1 gave the best results with 39M27 and 39D82 respectively. These isolates and another corn isolate, Azospirillum zeae N7, were tested in a sandy soil with a 55 and 110 kg ha⁻¹ of nitrogen fertility at the Delhi research Station of Agriculture and Agri-Food Canada over two years. Although out of seven bacterial treatments, no treatment provided a statistically significant yield increase over control plots but S. canadense CR11 and A. zeae N7 provided statistically significant yield increase as compared to other bacteria. The 110 kg rate of nitrogen provided significant yield increase compared to the 55 kg rate in both years.     

The regeneration status of the endangered Acer opalus subsp. granatense throughout its geographical distribution in the Iberian Peninsula

Acer opalus subsp. granatense is an endemic endangered tree with a wide but fragmented distribution in the Mediterranean mountains. The persistence of its small populations often depends on just a few adults, and consequently is highly vulnerable to factors limiting recruitment. In this paper, we examined the regeneration status of this maple in 16 populations throughout its whole geographical distribution in the Iberian Peninsula. Age and size structures were analysed as indicators of the viability of the species. Additionally, we studied the effects of herbivory by ungulates and the role of shrubs as nurse plants in maple regeneration dynamic. Our results show that A. opalus subsp. granatense has active recruitment throughout its range in the Iberian Peninsula. Shrubs served as the main microsites for recruitment, not only for early establishment but also for long-term survival. However, ungulates heavily damaged maple saplings in all locations and microhabitats. A direct consequence of herbivory is the uncoupling of age and size structures, saplings becoming older but not higher, possibly affecting population turnover in the long term. We suggest that the conservation of the small populations of Acer opalus subsp. granatense heavily depends on the control of herbivory pressure throughout the maple distribution area.     

Monitoring the performance of wild-born and introduced lizards in a fragmented landscape: Implications for ex situ conservation programmes

Ex situ conservation of animal populations may benefit from captive-breeding programmes, but these are criticised because they are assumed to be difficult, time-consuming and expensive, while they do not guarantee success. However, such assumptions remain untested in most organisms; for example, introductions could be very useful for recovering populations of small-sized species with short generation time, no learned behaviours, and ease to rear in captivity. Here, we document an easy, cheap and successful reintroduction programme of the lacertid lizard Psammodromus algirus. Two captive-bred cohorts (178 juveniles in 2001 and 187 in 2002) were released in four woodland fragments (0.9-5.2 ha) at two localities (B and V); B housed a stable lizard population whereas V apparently lacked a viable population of lizards. We monitored introduced and native lizards during 2002 and 2003, and carried out a corroborative searching in 2006 which confirmed the existence of a lizard population at site V. Introduced lizards had higher activity and dispersed more frequently among woodland fragments than native ones. Survivorship and growth rates were similar for both groups, but introduced juveniles were about 25% larger than native ones, due to both early hatching and better rearing conditions. The whole procedure was easily implemented in our Faculty facilities (mean hatching and hatchling survival rates of 0.90 and 0.87), and cost less than 20,000 € (excluding salaries). Therefore, similar programmes may be of wide application in small animals and of practical importance for species with a meta-population structure living in fragmented landscapes.     

Reproductive biology and conservation implications of three endangered snapdragon species (Antirrhinum, Plantaginaceae)

About 32% of Antirrhinum species are considered to be endangered; however, no field studies have focused on their reproductive biology. In this work, several aspects of the reproductive biology (flowering phenology, floral biology, breeding system) and potential limits on seed quantity and quality (pollen limitation, inbreeding depression) were studied in natural populations of three endangered species of the genus (Antirrhinum charidemi, Antirrhinum subbaeticum, Antirrhinum valentinum). Results disclose that all three species need insect visitors for seed production since fruit set after autonomous self-pollination was lower than under hand cross-pollination. A. charidemi and A. valentinum were mainly self-incompatible, whereas A. subbaeticum was self-compatible but herkogamous. Supplementary pollination in open-pollinated flowers only increased fruit set and seed set relative to controls in a given population of A. valentinum. Preliminary data on inbreeding depression at early life-cycle stages of the self-compatible A. subbaeticum revealed that the cumulative level was low. Despite the three species being closely related and sharing many ecological characteristics, they show different mating systems, and different factors limit seed quantity and quality. Thus, caution should be taken when making a common conservation plan for a group of closely related taxa.     

Relationship between population size and genetic diversity in endangered populations of the European bullhead (Cottus gobio): implications for conservation

This study investigated the relationship between the current size of endangered bullhead (Cottus gobio) populations and microsatellite genetic variability. Additionally, the microsatellite data were used to evaluate whether a genetic test for population bottlenecks was able to provide evidence of recent severe population declines. Finally, our results were used to develop conservation priorities and measures. Population size appears to be a crucial parameter in determining the amount of genetic diversity that can be preserved in bullheads, since a significant positive correlation was observed between both variables. Furthermore, in some populations we were able to detect genetic signatures of the documented decline in population size. We suggest that the most immediate goal for bullhead conservation should be to increase the size and the range of the populations, and in doing so minimise or even reverse further genetic erosion. Potential management actions like habitat quality improvement, reduction of river fragmentation and supplementation programmes (translocation, supportive breeding) are discussed.     

Relationship of biotic and abiotic factors to recruitment patterns in Margaritifera margaritifera

We investigated relationships of biotic and abiotic factors to recruitment patterns of the endangered freshwater pearl mussel (Margaritifera margaritifera) in 10 Swedish streams. We found that the maximum proportion of gravid mussels did not differ between streams with and without recent recruitment. Moreover, the mean glochidial load on trout (Salmo trutta), which was positively related to adult mussel density, did not differ significantly between these stream types. Thus, the larval stages of the freshwater pearl mussel were not related to recruitment failure. Instead, recruitment is probably hindered at the next stage in the life history of the mussels, the benthic stage, and may be related to sedimentation as turbidity was four times greater in streams lacking recent recruitment than in streams with recent recruitment. Furthermore, we found that juvenile mussel density was positively related to the number of glochidial infections per stream area in streams with ongoing recruitment, indicating that successful recruitment in these streams may depend on both mussel and trout density. Future research should thus examine biotic interactions between mussels and trout as well as the effects of sedimentation on benthic-living mussels.     

Surface water and ground-water thresholds for maintaining Populus-Salix forests, San Pedro River, Arizona

Ground-water and surface flow depletions are altering riparian ecosystems throughout the southwestern United States, and have contributed to the decline of forests of the pioneer trees Populus fremontii (Fremont cottonwood) and Salix gooddingii (Goodding willow). On some rivers, these forests have been replaced by shrublands of Tamarix ramosissima (tamarisk), a drought-tolerant species from Eurasia. The physiological response of these three riparian plant species to decreases in water availability is well studied, but little attention has been given to shifts in community and population structure in response to declines in surface flow and ground-water levels. Based on study of 17 sites spanning a hydrologic gradient, this research identified hydrologic thresholds above which P. fremontii-S. gooddingii maintain tall dense stands with diverse age classes, and above which they are more abundant than T. ramosissima stands along the San Pedro River in Arizona. Surface flow permanence was the hydrologic variable that explained most of the variance in species abundance and relative importance, with inter-annual ground-water fluctuation and depth to ground water also contributing. P. fremontii and S. gooddingii were dominant over T. ramosissima at sites where surface flow was present more than 76% of the time, inter-annual ground-water fluctuation was less than 0.5 m, and average maximum depth to ground water was less than 2.6 m, during a two-year period of data collection. Because T. ramosissima is a shrub species with smaller leaves and lower canopy heights than P. fremontii and S. gooddingii, these shifts in species composition corresponded to decreases in maximum canopy height and upper stratum (above 8 m) vegetation volume as site water availability declined. As well, sites with deeper water tables and more intermittent flows had greater areal coverage of shrublands and less of woodlands. The altered vegetation structure along dewatered rivers may lower wildlife habitat quality. This study provides river managers with quantitative hydrologic guidelines for conserving tall dense P. fremontii-S. gooddingii stands and emphasizes the importance of maintaining long-term hydrologic conditions that are favorable to these species. The study also has implications for riparian restoration and invasive species management by suggesting that desired outcomes may be achieved through restoration of physical processes.     

Ecology of the native and introduced crayfishes Austropotamobius pallipes and Procambarus clarkii in southern Spain and implications for conservation of the native species

The former and present distribution of white clawed crayfish (Austropotamobius pallipes) in the province of Granada (southern Spain) is studied. Before 1980 it was widely distributed but at present only 16 populations exist. The decline is related to the presence of the freshwater red-swamp crayfish (Procambarus clarkii), an American species, vector of the aphanomycosis disease, introduced to the Iberian Peninsula in 1974 and now widely distributed in the watercourses and marshes of southern Spain. To establish an appropriate conservation policy for A. pallipes at its southernmost distribution limit, we studied watercourses from two river basins, Genil and Guadiana Menor, (tributaries of the Guadalquivir River). P. clarkii inhabits the medium to lower reaches of these two river basins (with its upper limit at 820 m a.s.l.). The distribution of this species was best explained by the effect of three of the 12 analyzed variables: altitude, water-current and minimum winter temperatures. From our results, the repopulation of the native crayfish is almost impossible in those reaches inhabited by P. clarkii. However, based on the habitat selection study, it is clear that upper reaches are unsuitable for the red-swamp crayfish, where the native white-clawed crayfish may have greater survival possibilities, and these sites can be used for future restocking projects.     

Competitive abilities of common field isolates and a commercial strain of Rhizobium leguminosarum bv. trifolii for clover nodule occupancy

We previously reported that commercial Rhizobium leguminosarum bv. trifolii inoculants failed to outcompete naturalized strains for nodule occupation of clover sown into an alkaline soil [Aust. J. Agric. Res. 53 (2002) 1019]. Two field isolates that dominated nodule occupancy at the field site were labeled with a PnifH-gusA marker. Marked strains were chosen on the basis that they were equally competitive and fixed similar amounts of nitrogen in comparison to their parental strain. The minitransposon insertions were cloned and sequence analysis revealed that neither lesion disrupted the integrity of any known gene. The marked strains were then used to follow nodule occupancy of Trifolium alexandrinum in competition against the commercial inoculant TA1 under a range of experimental conditions. In co-inoculation experiments in sand-vermiculite, TA1 outcompeted each marked field isolate for nodule occupancy. However, using TA1-inoculated seed sown into alkaline soil containing a marked field strain, it was demonstrated that by increasing the cell number of marked rhizobia in the soil and reducing the cell number of the commercial inoculant, the proportion of nodules occupied by TA1 was reduced. These studies indicate that the ability of the field isolates to dominate nodule occupancy in the alkaline field soils was most likely caused by poor commercial inoculant survival providing the advantage for naturalized soil rhizobia to initiate nodulation.     

Coppice management effects on experimentally established populations of three herbaceous layer woodland species

Traditional coppice management creates a temporal release of resources. We determined how this affected three herbaceous species (Cardamine pratensis, Primula elatior and Geum urbanum) and if it was suitable for their conservation within woodland given their differing phenologies and habitat affinities for woodland.Reproductive adults were transplanted and their fate, i.e. survival and counts of leafs and flowers, plus the fate of their progeny, were monitored for three years following cutting of coppice shoots (three light levels) or yearly autumn mowing.Cardamine pratensis and P. elatior produced more flowers with increasing light availability. Mowing increased flower and leaf production with time for P. elatior. Seedling numbers followed a similar trend. Geum urbanum initially produced more flowers with increasing light and when mown, but the effect disappeared and did not increase seedling numbers. Its basal leaves showed the opposite pattern. Population growth rates (λ), calculated for P. elatior and G. urbanum, confirmed the strong treatment effects on the former and the absence of effects on the latter. Yet, decomposition of treatment effects, showed considerable flexibility in life history of G. urbanum, except for contributions of fecundity. The latter, however, contributed most to positive effects on λ for P. elatior.Early flowering species with an affinity for open habitats (C. pratensis > P. elatior) benefited more from temporal resource release than the later flowering, typical woodland species. Coppice management thereby maintains both typical forest herbs and herbs with affinity for more open habitats. This is an important conservation tool especially in intensively managed landscapes.     

Genetic structure, population dynamics, and conservation of Black caiman (Melanosuchus niger)

Microsatellite DNA polymorphisms were screened in seven populations of the largest Neotropical predator, the Black caiman Melanosuchus niger (n = 169), originating from Brazil, French Guiana and Ecuador. Eight loci were used, for a total of 62 alleles. The Ecuadorian population had the lowest number of alleles, heterozygosity and gene diversity; populations of the Guianas region exhibited intermediate diversities; highest values were recorded in the two populations of the Amazon and Rio Negro. During the last century Melanosuchus populations have been reduced to 1-10% of their initial levels because of hunting pressure, but no strong loss of genetic diversity was observed. Both the inter-locus g-test and the Pk distribution suggested no recent important recovery and/or expansion of current populations. On a global scale, the inter-population variation of alleles indicated strong differentiation (F_ST = 0.137).Populations were significantly isolated from each other, with rather limited gene flow; however, these gene flow levels are sufficiently high for recolonization processes to effectively act at regional scales. In French Guiana, genetic structuring is observed between populations of two geographically close but ecologically distinct habitats, an estuary and a swamp. Similar divergence is observed in Brazil between geographically proximate “black water” and “white water” populations. As a consequence, the conservation strategy of the Black caiman should include adequate ecosystem management, with strong attention to preservation of habitat integrity. Distribution of genetic diversity suggests that current populations originated from the central Amazonian region. Dispersal of the species may thus have been deeply influenced by major climatic changes during the Holocene/Pleistocene period, when the Amazonian hydrographic networks were altered. Major ecological changes such as glaciations, marine transgressions and a hypothesized presence of an Amazonian Lake could have resulted in extension of Black caiman habitats followed by isolation.     

Novel microsatellite loci for the compost earthworm Eisenia fetida: A genetic comparison of three North American vermiculture stocks

Earthworms are important components of soil ecosystems worldwide, and have been used extensively as indicator species in ecotoxicology studies. Our understanding of mating systems, population structure, and genetic diversity in earthworms is limited by the current lack of available genetic tools. To address this gap, we developed 16 novel microsatellite markers for the compost earthworm Eisenia fetida, one of the most widely studied earthworm species. We tested the new markers in 3 putative populations of worms from commercial vermiculture operations in Canada and the U.S.A. All 16 loci were variable in at least one population, with the number of alleles per locus ranging from 3 to 10, observed heterozygosity from 0.000 to 0.783, and polymorphic information content from 0.032 to 0.587. One group had significantly reduced heterozygosity compared to the other 2, but overall there were only minor genetic differences among the tested suppliers, suggesting a possible bottleneck for this species in North America. The microsatellite loci we describe here will be extremely useful tools for future field and laboratory studies of E. fetida. Body size and condition in adult worms varied significantly by supplier, and breeding success and cocoon production were significantly higher in breeding pairs from one supplier compared to the other two. In the absence of evidence for genetic divergence among populations, our results suggest that the early rearing environment may be an important factor affecting adult breeding performance. We caution that the source of worms may affect the outcome of laboratory experiments involving growth and reproduction.     

Pseudomonas corrugata: A suitable bacterial inoculant for maize grown under rainfed conditions of Himalayan region

Colonization and survival of the inoculated bacteria in rhizosphere of maize were investigated in field and pot experiments conducted for 3 consecutive years under rainfed conditions of Himalayan region. The effect of bacterial inoculations on growth and yield related parameters of maize were also evaluated. While three bacterial species, viz. Bacillus megaterium, Bacillus subtilis and Pseudomonas corrugata were tested in 1st year experiments, P. corrugata (based on the 1st year results) was chosen for inoculation in the subsequent experiments. All the three bacterial inoculants showed good rhizosphere competence giving high inoculum numbers (log₁₀ 11.13-11.34 cfu g⁻¹). The bacterial inoculations by B. megaterium, B. subtilis and P. corrugata resulted in an increment in grain yield of maize up to 122.4%, 135.2% and 194.3%, respectively, as compared to respective control. In 1st year, the antibiotic marked (Nal^r Rif^r) inoculant P. corrugata resulted in the highest increase in grain yield, statistically significant (P<0.05) as compared to control, B. megaterium and B. subtilis. In 2nd and 3rd year experiments, P. corrugata increased the grain yield up to 147.28% and 149.93%, respectively, as compared to control. The best performance and consistent trend of P. corrugata to increase plant yields was credited to its initial isolation from rhizosphere of maize growing under temperate conditions. The overall beneficial effects of bacterial inoculations on maize were contributed to (1) the colonization and survival of the introduced bacteria, and (2) stimulation of the indigenous microflora in the rhizosphere. Based on the comprehensive results obtained in this study, P. corrugata may be recommended as suitable bioinoculant for maize fields of temperate climate grown under rainfed conditions.     

Reproductive constraints for the long-term persistence of fragmented Acacia dealbata (Mimosaceae) populations in southeast Australia

Fragmented and degraded vegetation characterises agricultural landscapes across southern Australian. Remnant vegetation within these regions performs a number of vital ecological and hydrological roles, but little is known about whether or how fragmentation is affecting the long-term persistence of these critical landscape elements. Acacias are a significant component of many remnant vegetation communities across Australia, forming numerous integral faunal and floral relationships. Here, reproductive output of 11 fragmented Acacia dealbata (Mimosaceae) populations from across the southern tablelands of New South Wales was assessed over 2 years to identify reproductive constraints associated with increasing vegetation fragmentation. Fertilization success is the major reproductive constraint, particularly in small populations, and probably reflects a self-incompatible reproductive strategy. During 2002 larger and more dense populations produced more legumes (p = 0.014 and <0.001, respectively) while in 2003 these two variables were associated with increased fertilization success (p = 0.004 and 0.017, respectively). There was also some suggestion that populations with fewer exotic species also experienced increased fertilization success (p = 0.055). Assessment of plant performance within populations suggests that consistent reproductive output of particular individuals within small populations may limit reproductive compatibility within these populations over time. The long-term persistence of many small A. dealbata populations may be jeopardised by low seed set, and limited recruitment and aging stands. Immediate steps are now required to ensure that these populations continue contributing to landscape function by augmenting populations, improving connectivity, and allowing disturbance events that will stimulate recruitment.     

Distribution, status, and conservation needs of the golden-crowned sifaka (Propithecus tattersalli)

The golden-crowned sifaka is considered one of the world's most endangered primates. To evaluate the species' current conservation status we established its actual distribution and abundance, and assessed current threats that affect its survival. Study methods involved direct sifaka observations and interviews to local villagers. Propithecus tattersalli's distribution is restricted to the region comprised between the Loky and Manambato rivers. Throughout its range, the species is abundant and it can even be found in small forest fragments, although it was never observed at elevations above 700 m.a.s.l. Major threats to the species include habitat destruction through slash-and-burn agriculture, grass fires, wood and gold extraction, and poaching. Total population estimates range from 6100 to 10,000 individuals, with an effective population size of approximately 2500-4000 sifakas. Though sensitive to forest destruction, the species seems to be resilient to current levels of landscape fragmentation. We recommend the establishment of a system of protected areas throughout the Loky-Manambato region and the implementation of a “Flagship Species Program” utilizing the golden-crowned sifaka as a catalyst for a regional Conservation Management Plan.