Human interference and gull predation in cormorant colonies

The vulnerability of cormorant eggs and nestlings to gull predation is greatly increased by human intrusion into breeding colonies. Observations of the behaviour of double-crested cormorants (Phalacrocorax auritus) and king shag (P. albiventer) vis-à-vis the behaviour of great black-backed and herring gulls (Larus marinus and L. argentatus) on the one hand and dolphin gulls (Leucophaeus scoresbii) on the other indicate that certain predictable offensive and defensive interactions occur when breeding birds are disturbed. Knowledge of these behavioural patterns suggests that interference with normal breeding activities and the resulting reduction in productivity of cormorants can be minimised in colonies where human access is carefully regulated.     

Livestock predation by endangered African wild dogs (Lycaon pictus) in northern Kenya

Most large mammalian carnivores are in global decline, principally due to conflict with livestock farmers. Because endangered African wild dogs (Lycaon pictus) range widely, often beyond the boundaries of protected areas, they may be particularly exposed to lethal control by farmers, even where nominally protected by reserves. Hence, effectively conserving wild dogs demands resolution of their conflicts with farmers. We investigated livestock depredation by African wild dogs living outside protected areas in northern Kenya. Scat analysis confirmed the distribution of depredation events reported by local farmers, indicating that farmer reports - collated by local Community Liaison Officers - gave a reasonably good index of the true pattern of depredation. Although livestock were abundant throughout the study area, depredation was exceedingly uncommon (approximately one attack per 1000 km² per year) and the costs of tolerating wild dogs were very low (US $3.40/wilddog/year) where wild prey remained, even at low densities. However, where wild prey were seriously depleted, wild dogs killed livestock repeatedly, and the cost of sustaining them rose to US $389/wilddog/year. Hence, although wild dogs had a negligible economic impact in the region, their impact was locally severe. Conservation activities for wild dogs are most likely to be successful if targeted at areas where wild prey remain, and where traditional herding practices have been retained.     

Foraging behaviour and habitat use by Antechinus flavipes and Sminthopsis murina (Marsupialia: Dasyuridae) in response to predation risk in eucalypt woodland

We examined the foraging behaviour and habitat use of two species of small Australian mammal (Antechinus flavipes and Sminthopsis murina) in response to predation risk in remnant eucalypt woodland. Predation risk was manipulated by providing refuge in the form of ground level wire netting to reduce risks from avian and mammalian predators. Giving-up-densities (GUD) using artificial food trays (20 mealworms in 1.5 l vermiculite) quantified the foraging behaviour in response to predation risk, by measuring the quitting harvest rate. Both A. flavipes and S. murina had lower GUDs (number of mealworms remaining) under the netting than in the open, most likely because these areas have lower predation risk. Animals also made greater visits to tracking tunnels under the netting compared to in the open. Tracking animal movements using fluorescent pigments also revealed preference for natural microhabitats that were structurally complex with animals moving most where logs and rock crevices were present. These results suggest that small mammals may use habitat structure to reduce their risks of predation. If future studies are able to demonstrate commensurate population-level responses, manipulation of habitat may be a useful management option to complement the direct control of exotic predators such as foxes and feral cats.     

Long-term trends in the demography of the Allen Cays Rock Iguana (Cyclura cychlura inornata): Human disturbance and density-dependent effects

Allen Cays Rock Iguanas (Cyclura cychlura inornata) are native to two small islets (Leaf and U Cay) in the north-central Bahamas. These populations were nearly extirpated in the early 1900s because of heavy hunting pressure (for food), but increased to a total of ca. 150 lizards in 1970, and now number over 500 (not including juveniles). Over the past several decades poaching has declined, but tourist visitation (including nearly daily supplemental feeding of iguanas) has increased. To examine human impacts on the demography of these iguanas, survival, population growth rates, and population sizes for subadult and adult (>25 cm snout-vent length) males and females on the two cays were estimated based on mark-recapture data collected over a 25-year period (1980-2004). As predicted, annual survival probability was higher on U Cay (with less human visitation) than on Leaf Cay, was higher in females than in males (which are bolder), and exhibited a declining trend. Both populations more than doubled during this study, but population growth rates declined to near zero in recent years. These data reflect the importance of human impacts, but also suggest that the populations may be nearing carrying capacity. The rapid population growth observed on these cays, and that seen for several other translocated iguana populations, suggest that if unnatural causes of mortality are reduced or eliminated, island populations of iguanas are capable of rapid recovery. The inexpensive establishment of assurance colonies on undisturbed “islands” should be considered for any comprehensive management plan for endangered species of iguanas.     

Response of Acacia species to disturbance by roadworks in roadside environments in southern New South Wales, Australia

Disturbances from road management activities are often considered to be a major threat to plants in roadside environments, however effects may not be deleterious to all plants. The post-disturbance response of three Acacia species with different life-history attributes was compared in four road reserves impacted by soil disturbance from grading activities. Recovery of acacias to grading was variable, however basal resprouting, root suckering and seedling emergence led to a 6.2% population increase for all road reserves combined. In two road reserves, there was significant resprouting of the facultative seeder A. decora, and 2 years after disturbance, resprouts reached mean heights of 71 and 74 cm. One year after disturbance, 71% of A. decora resprouts flowered and 49% also set viable seed, and there was a significant positive relationship between flowers produced and viable seed set. Similarly, 65% of resprouts of the facultative seeder A. montana flowered but only 10% set viable seed. In contrast, there was patchy seedling emergence of the obligate seeder A. pycnantha and to a lesser extent A. montana, and seedlings did not reach reproductive maturity 1 year after disturbance. Drought most likely reduced seedling numbers, as seedlings were only recorded in shaded road reserves, where additional water was applied from roadworks activities. Grading of roadside environments appears to favour plants with strong resprouting ability, and persistence of Acacia populations will depend on the timing of soil disturbances from grading activities in relation to species life-history attributes.     

Mycoparasitism by Pythium oligandrum and P. acanthicum

Isolates of the reported mycoparasites Pythium oligandrum, P. acanthicum and P. periplocum markedly reduced growth and cellulolysis by Botryotrichum piluliferum, grew rapidly across agar plates precolonized by Phialophora radicicola var radicicola (sensu Deacon) and, where tested (not P. periplocum), were non-pathogenic towards higher plants. Isolates of P. echinulatum, P. mamillatum. P. megalacanthum, P. spinosum, P. ultimum and one isolate of P. acanthicum behaved differently from the mycoparasites and could, themselves, be placed in two groupings in these tests. It is suggested that the ability or otherwise to grow on Phialophora-precolonized agar plates may help to distinguish broad biological groupings within the genus Pythium, but these groupings may cut across conventional taxonomic ones.One isolate of P. acanthicum was tested for its effects on a range of cellulolytic fungi: it reduced their growth to different extents, as did P. oligandrum.Plates of potato-dextrose agar precolonized by Phialophora radicicola were used to isolate selectively P. oligandrum and similar fungi from soils, but the use of hemp seed baits in conjunction with precolonized plates was less selective for these fungi.Straw pieces precolonized by P. oligandrum and buried in soil decomposed at the same rate as virgin straws or those precolonized by P. ultimum or Mucor hiemalis. Subsequently, Stachyholrys atra appeared to colonize straws more frequently from soil, and Fusarium spp. less so, in the presence of P. oligandrum than in its absence. In the laboratory, P. oligandrum was antagonized by Slachyholrys, whereas Fusarium spp. were frequently overgrown by the Pythium.     

The measurement of chronic disturbance and its effects on the threatened cactus Mammillaria pectinifera

Measuring how anthropogenic disturbance affects biological systems is crucial for conservation and management. However, it is often difficult to quantify disturbance when it occurs in a slow, long-lasting - or chronic - fashion. Because various human activities influence gradually an area, chronic disturbance must be measured on a continuous scale that accounts for different sources of disturbance. Here we propose a method to develop multimetric indices for chronic disturbance. The approach is exemplified by considering the effects of disturbance on the threatened cactus Mammillaria pectinifera. Fourteen indicators of three agents of disturbance (human activities, livestock raising and land degradation) were measured in 10 populations of M. pectinifera, and summarised through principal components analysis (PCA). An index for each agent was also developed. M. pectinifera achieved maximum density at intermediate values of the first PCA axis, which was related to disturbance intensity. Assessing only both extremes of the disturbance gradient, where density is low, would erroneously suggest that disturbance has no effect on this plant. The different disturbance agents act synergistically on M. pectinifera, and their combined effects are detrimental. Land degradation reduces plant density, while livestock enhances it. However, overgrazing promotes degradation, so maintaining appropriate livestock levels is critical for management. Our method allowed us to identify which agents have more impact on threatened species, and sets the basis to manage disturbance agents in a way compatible with conservation. The method proposed here can be easily modified for its use in other environments and to account for different forms of anthropogenic disturbance.     

Restoration of Calluna vulgaris on grass-dominated moorlands: The importance of disturbance, grazing and seeding

Calluna vulgaris-dominated heaths and moorlands are habitats of international conservation importance. Degradation has occurred throughout their range with Calluna typically being replaced by grass species. The cessation of grazing is often impractical and rarely results in the recovery of Calluna abundance when it is initially present at low cover. Thus the development of restoration methods is required; these should be practical at a large-scale, in remote areas and create suitable conditions for Calluna germination and establishment, whilst still allowing grazing to occur. A replicated field experiment was established on Nardus stricta and Molinia caerulea-dominated moorlands to test the efficacy of different grazing regimes and intervention techniques aimed at establishing Calluna. Disturbance (rotavation and trampling by animals) to create bare ground increased Calluna establishment. On the Nardus site, Calluna establishment was equally successful on rotavated and trampled plots, but rotavation was more successful on the Molinia site. Seeding with Calluna increased Calluna establishment irrespective of whether a seed-bank was present. At the Nardus site, 0.5 cow/ha for two months in summer led to Calluna establishment and growth similar to that of ungrazed plots and was more successful than a mixed grazing regime (1 ewe/ha plus 0.5 cow/ha for 2 months) or a sheep only regime (1.5 ewes/ha). The creation of small patches of bare ground, seed addition and low intensity grazing enabled the rapid establishment of Calluna on grass-dominated moorlands; such techniques may also be applicable in other habitats where restoration requires the addition of a single/few species and minimal intervention.     

Nature-based tourism as a form of predation risk affects body condition and health state of Podarcis muralis lizards

Nature-based tourism has experienced a greater increase, and, even although it might have deleterious effects for many wildlife species, its consequences remains little explored. Many lizard species are endangered and tourism has been proposed as a potential factor responsible of the decline of several lizards’ populations, but no study has examined the effect of tourism on lizards’ behaviour, body condition and health state. Many lizards respond to people as if they were predators, by readily escaping to refuges. However, an increase in the frequency of these antipredatory strategies can lead to a loss of body condition, which may have important consequences for short and long term fitness. We analysed the effects of tourism on escape behaviour of common wall lizards, Podarcis muralis, as well as on their body condition and health state (ectoparasites, blood parasites, and cell mediated immune response). Results showed that lizards did not modify their escape behaviour in response to tourism. Lizards had similar approach and flight distances, and escape strategies regardless of the level of tourism pressure. However, lizards inhabiting areas with high tourism levels, where they presumably needed to perform antipredatory behaviours more often, showed higher intensity of infection by ticks and lower body condition at the end of the breeding period. Moreover, lizards with poorer body condition had lower cell mediated immune responses. Therefore, tourism seems to have deleterious effects on body condition and on host-parasite relationships in this lizard species. These effects should be taking into account when designing walking paths in protected areas. Our study reports evidence that regardless lizards showed similar escape behaviour in tourist than in natural areas, their body condition and health state should be also examined to accurately assess the actual effects of tourism on lizards’ populations.     

Short-chain polyphosphate in arbuscular mycorrhizal roots colonized by Glomus spp.: A possible phosphate pool for host plants

We investigated the relationship between plant growth and polyphosphate (poly P) content in Allium fistulosum roots colonized by Glomus sp. R10 or Glomus etunicatum with different levels of phosphate addition. Poly P was quantified by two enzymatic assays: long-chain poly P (>∼20 inorganic phosphate [P_i] residues) with polyphosphate kinase, and total poly P with polyphosphate exopolyphosphatase. The difference between these values was designated as short-chain poly P (<∼20 P_i residues). The content of long-chain poly P in mycorrhizal roots and plant growth was poorly correlated or not, depending in fungal species. However, the content of short-chain poly P and plant growth was highly correlated in both species. This difference suggests that short-chain poly P in mycorrhizal roots colonized by Glomus spp. functions as a pool of P_i for the plant.     

Genetic diversity among Elaeagnus compatible Frankia strains and sympatric-related nitrogen-fixing actinobacteria revealed by nifH sequence analysis

Elaeagnus compatible Frankia isolates from Tunisian soil have been previously clustered with Frankia, colonizing Elaeagnaceae and Rhamnaceae in two different phylogenetic subgroups, while strain BMG5.6 was described as a new lineage closely related to Frankia and Micromonospora genera. In this study we further assess the diversity of captured Frankia and the relationship with BMG5.6-like actinobacteria, by using nifH gene sequences. Using PCR-RFLP screening on DNA extracted from lobe nodules, additional microsymbionts sharing BMG5.6 features have been detected proving a widespread occurrence of these actinobacteria in Elaeagnus root nodules. Neighbour-Joining trees of Frankia nifH sequences were consistent with previously published 16S rRNA and GlnII phylogenetic trees. Although four main clades could be discerned, actinobacterial strain BMG5.6 was clustered with Frankia strains isolated from Elaeagnus. The present study underscored the emanation of new diazotrophic taxon isolated from actinorhizal nodules occupying intermediate taxonomic position between Frankia and Micromonospora. Moreover, its aberrant position in nifH phylogeny should open network investigations on the natural history of nitrogen-fixing gene among actinobacteria.     

A possible role for saprotrophic microfungi in the N nutrition of ectomycorrhizal Pinus resinosa

We determined whether Pinus resinosa, selected ectomycorrhizal and saprotrophic microfungi have access to various organic nitrogen sources commonly found in the forest. Vector analysis demonstrated nitrogen limitation of the P. resinosa in the plantation from which most of the fungi were isolated, establishing this study's relevance. Nonmycorrhizal P. resinosa seedlings did not absorb significant N from amino acids. The ectomycorrhizal fungi, including Pisolithus tinctorius, Suillus intermedius and Tylopilus felleus, obtained substantial N from amino acids, a limited amount of N from glucosamine, and essentially no N from protein-tannin complex. In contrast, Penicillium and Trichoderma readily acquired N from protein-tannin and glucosamine. Thus, there was an increasing ability to obtain N from complex organic N sources from plant to ectomycorrhizal fungi to saprotrophic fungi. Furthermore, N mineralization from an organic N source by Penicillium depended on the C:N ratio. We conclude that acquisition of relatively simple organic N sources by P. resinosa is likely to be largely indirect via ectomycorrhizal fungi, and that more complex organic N sources may become accessible to ectomycorrhizal fungi (and thus possibly their host plants) following mineralization by saprotrophic fungi such as Penicillium or Trichoderma when C:N ratios are sufficiently low.     

Village size and forest disturbance in Bhadra Wildlife Sanctuary, Western Ghats, India

Habitat fragmentation, land cover change and biodiversity loss are often associated with village communities in protected areas, but the extent and intensity of such impacts are often inadequately assessed. We record resource use and depletion by human inhabitants by conducting ecological surveys in six villages and social surveys in all 13 villages of varying sizes in India’s Bhadra Wildlife Sanctuary (492 km²). We examined the occurrence of 10 regionally-specific ecological indicators that encompassed several aspects of human activities. Thirty transects with 180 total sampling locations recorded the occurrence of these specific habitat disturbance variables. High correlations between the variables led to the use of principal component analysis to derive an effective summary index that reflected disturbance intensity and determined village ecological impacts spatially. A generalized linear model was fit to determine the rate at which disturbance decreases as we move away from village centers. Our model indicates that village size class, distance from the village and proximity to other villages were significant predictors of the disturbance index. The index distinguished each village’s spatially explicit ecological impact. We estimated that an average area of 23.7 km² of the forest surrounding the six focal villages was altered by human activities. These six villages have directly impacted 8-10% of this protected area.     

Age of wheat and barley roots and infection by gaeumannomyces graminis var tritici

Seminal roots of wheat and barley seedlings were inoculated with G. graminis var tritici on regions 0, 5- and 15-days old, and assessed for intensity and extent of infection after standard times. Wheat roots were most heavily infected on young regions, whereas barley roots were most heavily infected on old ones. The effect of root age in wheat was similar in both unsterile and aseptic conditions, so it could not be ascribed to saprophytic rhizosphere micro-organisms interacting with G. graminis.The contrasting results for wheat and barley are explained by a single hypothesis, based on decreasing host-resistance in the root cortex but increasing resistance at or near the endodermis as the roots age. It is suggested that, under some conditions, even small amounts of non-pathogenic root cortex death can enhance infection by G. graiminis. This interpretation may explain several aspects of take-all and its biological control by other dark mycelial parasites.     

Metabolism of fluoroacetate by a soil Pseudomonas SP. and Fusarium solani

Enzymes (haloacetate halidohydrolases) capable of cleaving the C-F bond of fluoroacetate and some other organofluorine compounds have been isolated and partially purified from a soil pseudomonad and from the common soil fungus Fusarium solani. Both enzymes readily released F^? from monofluoroacetate and fluoroacetamide but were without effect on a wide range of other organic F-compounds. The enzymes also cleaved the C-Cl and C-Br bonds in mono-chloroacetate and monobromoacetate. Inorganic F^? acted as a competitive inhibitor of the enzymes. The molecular weights of both enzymes were about 62,000. Thus the properties of the halidohydrolases from both organisms were similar in many respects but the bacterial enzyme was more stable at 55°C and exhibited an unusual difference in temperature coefficient (Q₁₀ value) over its higher (30–55°C) and lower (15–30°C) temperature ranges.     

Zinc uptake by mycorrhizal and uninfected roots of Pinus radiata and Araucaria cunninghamii

Uptake of zinc from solution by uninfected roots, ectomycorrhizas of Pinus radiata, and endomycorrhizas of Araucaria cunninyhamii occurred by a non-metabolic phase and by metabolically mediated absorption. The metabolically mediated absorption of Zn was 1.4–4.5 times greater for ectomycorrhizas than for uninfected roots and 2.6 times greater for endomycorrhizas than for uninfected roots. Part of the increase with ectomycorrhizas was due to their larger size than uninfected roots and when corrected for this, the uptake/cm² was 1.4–3.0 times greater. The roles of mycorrhizas in uptake of Zn and other trace elements from soil are discussed.     

Improved zinc tolerance in Eucalyptus globulus inoculated with Glomus deserticola and Trametes versicolor or Coriolopsis rigida

The potential of interactions between saprophytic and arbuscular mycorrhizal (AM) fungi to improve Eucalyptus globulus grown in soil contaminated with Zn were investigated. The presence of 100 mg kg ⁻¹ Zn decreased the shoot and root dry weight of E. globulus colonized with Glomus deserticola less than in plants not colonized with AM. Zn also decreased the extent of root length colonization by AM and the AM fungus metabolic activity, measured as succinate dehydrogenase (SDH) activity of the fungal mycelium inside the E. globulus root. The saprophytic fungi Trametes versicolor and Coriolopsis rigida increased the shoot dry weight and the tolerance of E. globulus to Zn when these plants were AM-colonized. Both saprophytic fungi increased the percentage of AM root length colonization and elevated G. deserticola SDH activity in the presence of all Zn concentrations applied to the soil. In the presence of 500 and 1000 mg kg⁻¹ Zn, there were higher metal concentrations in roots and shoots of AM than in non-AM plants; furthermore, both saprophytic fungi increased Zn uptake by E. globulus colonized by G. deserticola. The higher root to shoot metal ratio observed in mycorrhizal E. globulus plants indicates that G. deserticola enhanced Zn uptake and accumulation in the root system, playing a filtering/sequestering role in the presence of Zn. However, saprophytic fungi did not increase the root to shoot Zn ratio in mycorrhizal E. globulus plants. The effect of the saprophytic fungi on the tolerance and the accumulation of Zn in E. globulus was mediated by its effect on the colonization and metabolic activity of the AM fungi.     

Potential gene exchange between Bacillus thuringiensis subsp. kurstaki and Bacillus spp. in soil in situ

The possible transfer of genes from Bacillus thuringiensis subsp. kurstaki (Btk) to indigenous Bacillus spp. was investigated in soil samples from stands of cork oak in Orotelli (Sardinia, Italy) collected 5 years after spraying of the stands with a commercial insecticidal preparation (FORAY 48B) of Btk. Two colonies with a morphology different from that of Btk were isolated and identified as Bacillus mycoides by morphological and physiological characteristics and by 16S rDNA analysis. Amplification by the polymerase chain reaction (PCR) of the DNA of the two isolated B. mycoides colonies with primers used for the identification of the Btk cry genes showed the presence of a fragment of 238 bp of the cry1Ab9 gene that had a similarity of 100% with the sequence of the cry1Ab9 gene present in GenBank, indicating that the isolates of B. mycoides acquired part of the sequence of this gene from Btk. No cells of Btk or B. mycoides carrying the 238-bp fragment of the cry1Ab9 gene were isolated from samples of unsprayed control soil. However, the isolates of B. mycoides were not able to express the partial Cry1Ab protein. Hybridization with probes for IS231 and the cry1Ab9 gene suggested that the inverted repeated sequence, IS231, was probably involved in the transfer of the 238-bp fragment from Btk to B. mycoides. These results indicate that transfer of genes between introduced Btk and indigenous Bacillus spp. can occur in soil under field conditions.     

Movement by rhizobium and nodulation of legumes

Several Rhizobium spp were tested for chemotaxis using a soft agar assay. Bacteria migrated in chemotactic bands in response to substances present in the agar medium. R. japonicum S-110 formed chemotactic bands in response to l-arabinose, l-canavanine, and yeast extract but not to several other common compounds, including several amino acids and sugars. These results suggested that simple compounds present in legume root exudates may attract these bacteria and aid in their rhizosphere accumulation and, thus, in the nodulation process. A slow-migrating mutant of R. japonicum S-110 was isolated. Microscopic examination showed that mutant populations had a much lower proportion of motile cells than did wild-type populations. Greenhouse nodulation tests, in which mutant and wild-type cells were mixed and used as inoculum, indicated that the mutant had less nodulation potential.     

Anthropogenic and natural disturbance lead to differing patterns of gene flow in the Rocky Mountain tailed frog, Ascaphus montanus

Understanding the influence of habitat alteration on population structure and persistence is critical for effective conservation strategies. Timber harvest and wildfire are two of the most prevalent disturbances across temperate forests, yet the long-term effects of these two forces on population connectivity have rarely been studied. We studied populations of the Rocky Mountain tailed frog (Ascaphus montanus) across landscapes that have experienced either timber harvest or broad scale fires. Rocky Mountain tailed frogs generally require forested habitat, and are a species of concern in managed forests. We used landscape genetic techniques to test the explanatory power of alternative paths of connectivity across both burned and harvested forests and identified topographical and climatic variables that significantly influenced gene flow. We found that timber harvest and fire led to different patterns of genetic connectivity. Widespread terrestrial gene flow was maintained across previously burned areas and connectivity was primarily limited by solar radiation. In contrast, gene flow among populations in managed forests followed riparian corridors, presumably to avoid the loss of cover due to timber harvest. Gene flow along riparian corridors in Rocky Mountain tailed frogs differs from a population of the closely related coastal tailed frog (Ascaphus truei), for which gene flow appears to occur primarily over land. These results suggest management of Rocky Mountain tailed frogs should focus on maintaining riparian buffer zones, which may be less effective for the coastal species. Thus, consideration of landscape differences is essential even for conservation of closely related, morphologically similar species.