Dynamics of hardwood patches in a conifer matrix: 54 years of change in a forested landscape in Coastal Oregon, USA

Changes to minor patch types in forested landscapes may have large consequences for forest biodiversity. The effects of forest management and environment on these secondary patch types are often poorly understood. For example, do early-to-mid successional minor patch types become more expansive as late successional forest types are fragmented or do they also become more fragmented in managed landscapes? We evaluated the dynamics of early-to-mid successional hardwood patches in a conifer-dominated landscape in relation to environment and land ownership in the central Coast Range of Oregon, USA, from the time of early logging to the present-day using scanned and georeferenced aerial photographs and a GIS. Hardwood patches declined in size, number, total area, and within-patch cover-type heterogeneity, and became more irregular in shape. Patch turnover and fragmentation was high, with most patches present at the historical date disappearing by the present-day. Land ownership was important to hardwood patch dynamics: hardwoods declined on lands owned by the USDA Forest Service, increased on non-industrial private lands, and were at similar levels at both dates on private forest industry lands. Patch locations became more restricted to near-stream, lower elevation areas where hardwoods are competitive. The relatively extensive distribution of hardwood patches at the historical date probably resulted from earlier fire, selective logging, and grazing. In recent decades, forest management that includes fire suppression and intensive management, and ecological constraints have resulted in a landscape in which early-to-mid successional hardwood patches have been reduced in size, fragmented, and restricted to particular locales.     

Variability of communities and physiological characteristics between free-living bacteria and attached bacteria during the PAH biodegradation in a soil/water system

The biodegradation of polycyclic aromatic hydrocarbons (PAHs) via free-living and attached micro-organisms in soil/water systems was observed in order to examine the variability in the community dynamics and physiological profiles of the micro-organisms. As determined by fluorescence in situ hybridization (FISH), the Domain Bacteria, consisting of three phyla α-, β- and γ-Proteobacteria, reached 41.27–56.05% of all organisms in the soil/water system for PAH biodegradation. Among the free-living species, Proteobacteria, including Brevundimonas (Pseudomonas) diminuta, Caulobacter spp., Mycoplana bullata, Acidovorax spp. and Pseudomonas aeruginosa were found to be dominant—making up 93.51–99.80% of the population—and therefore seem to be associated with PAH biodegradation. Total plate count numbers and the count of Pseudomonas sp. present in the free-living population increased to between 10³ and 10⁶ CFU ml⁻¹ when clay with very low organic matter content was used as the matrix for PAH degradation. However, total plate count microbial numbers increased to only 10¹–10² CFU ml⁻¹ using natural soil from Taichung containing 1.883% organic matter. The soil organic content (SOM) seemed to affect the mass transfer of PAH in soil, leading to the difference in PAH biodegradation. Two different approaches, which included community-level physiological profiling (CLPP) and ectoenzymatic activities, were used to explain the functional diversity between free-living and attached bacteria. The free-living and attached bacterial communities from the clay system showed proportionately greater differences using CLPP. Relatively high levels of esterases, aminopeptidases and some specific glycolysis-gluconeogenesis enzymes gave an identifiable correlation with PAH biodegradation. The differences in bacterial composition, numbers and physiological characteristics show that free-living and attached micro-organisms may play different biochemical roles in PAH degradation in soil.     

Habitat characteristics of adult frosted elfins (Callophrys irus) in sandplain communities of southeastern Massachusetts, USA

Changes to land use and disturbance frequency threaten disturbance-dependent Lepidoptera within sandplain habitats of the northeastern United States. The frosted elfin (Callophrys irus) is a rare and declining monophagous butterfly that is found in xeric open habitats maintained by disturbance. We surveyed potential habitat for adult frosted elfins at four sites containing frosted elfin populations in southeastern Massachusetts, United States. Based on the survey data, we used kernel density estimation to establish separate adult frosted elfin density classes, and then used regression tree analysis to describe the relationship between density and habitat features. Adult frosted elfin density was greatest when the host plant, wild indigo (Baptisia tinctoria), density was >2.6 plants/m² and tree canopy cover was <29%. Frosted elfin density was inversely related to tree cover and declined when the density of wild indigo was <2.6 plants/m² and shrub cover was ?16%. Even small quantities of non-native shrub cover negatively affected elfin densities. This effect was more pronounced when native herbaceous cover was <36%. Our results indicate that management for frosted elfins should aim to increase both wild indigo density and native herbaceous cover and limit native tree and shrub cover in open sandplain habitats. Elimination of non-native shrub cover is also recommended because of the negative effects of even low non-native shrub cover on frosted elfin densities. The maintenance of patches of early successional sandplain habitat with the combination of low tree and shrub cover, high host plant densities, and the absence of non-native shrubs appears essential for frosted elfin persistence, but may also be beneficial for a number of other rare sandplain insects and plant species.     

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.     

Herbicides, weeds and endangered species: management of bitou bush (Chrysanthemoides monilifera ssp. rotundata) with glyphosate and impacts on the endangered shrub, Pimelea spicata

Environmental weed invasion threatens the biodiversity of native species. Unfortunately, managing these weeds may also affect biodiversity adversely. A recent example occurred when glyphosate, a herbicide used to control the highly invasive weed, bitou bush (Chrysanthemoides monilifera ssp. rotundata), accidentally drifted over a small population of an endangered shrub, Pimelea spicata. Following concerns that the affected population would not recover and, thereby, cause the local extinction of P. spicata, we conducted a series of glasshouse and field experiments to explore the impacts of glyphosate on this endangered species. Seedlings and young plants of P. spicata, in which the tap root was undeveloped, were killed by a single application of glyphosate. Older plants with a well developed tap root also died back initially, but about 50% of individuals re-sprouted. This re-growth was associated with a significant decrease in tap root diameter, implying that further disturbance, including repeated treatment with glyphosate, would kill plants by impairing their potential for recovery. Unlike some sclerophyllous native shrubs, the tolerance of P. spicata to glyphosate was limited, even when its growth was slowed artificially by limiting water availability. Winter applications of glyphosate to manage infestations of bitou bush will impact adversely on populations of P. spicata and may also affect the other rare and endangered species whose survival is threatened by this species, even though some natives are unaffected by the herbicide. Protecting native biodiversity from bitou bush will involve sustainable weed management that minimises impacts on non-target native species.     

Effects of physicochemical interactions and microbial activity on the persistence of Cry1Aa Bt (Bacillus thuringiensis) toxin in soil

Genetically modified crops, that produce Cry insecticidal crystal proteins (Cry) from Bacillus thuringiensis (Bt), release these toxins into soils through root exudates and upon decomposition of residues. The fate of these toxins in soil has not yet been clearly elucidated. Persistence can be influenced by biotic (degradation by microorganisms) and abiotic factors (physicochemical interactions with soil components, especially adsorption). The aim of this study was to follow the fate of Cry1Aa Bt toxin in contrasting soils subjected to different treatments to enhance or inhibit microbial activity, in order to establish the importance of biotic and abiotic processes for the fate of Bt toxin. The toxin was efficiently extracted from each soil using an alkaline buffer containing a protein, bovine serum albumin, and a nonionic surfactant, Tween 20. The marked decline of extractable toxin after incubation of weeks to months was soil-dependent. The decrease of extractable toxin with incubation time was not related to microbial degradation but mainly to physicochemical interactions with the surfaces that may decrease immunochemical detectability or enhance protein fixation. Hydrophobic interactions may play an important role in determining the interaction of the toxin with surfaces.     

Survival of the western pond turtle (Emys marmorata) in an urban California environment

The western pond turtle Emys (formerly Clemmys) marmorata is declining throughout its range, primarily due to loss of habitat via urbanization and conversion to agriculture. Urban waterways present several important challenges to freshwater turtle populations, but they also present an opportunity to maintain declining species in a ubiquitous habitat that has high public visibility. The arboretum waterway on the University of California, Davis campus is an example of an extensively altered urban habitat that supports a relatively large E. marmorata population. Over the last 6 years, we monitored the turtle population inhabiting the arboretum waterway to determine the demographic health of the population, and the challenges and opportunities that urban environments pose for pond turtles. Since 1993, the naturally existing arboretum pond turtle population has declined by approximately 40% and has shown little natural recruitment. During this time, we also introduced 31 headstarted turtles into the arboretum. Headstarting is the process of raising juveniles in captivity until they have outgrown their period of greatest vulnerability to predators, and then releasing them into the wild. Our headstarting results demonstrate that this contentious strategy is a viable option for adding young turtles to the population, although it does not address the causes of decline. Over the course of our study, we encountered nine species of non-native turtles in the waterway, and these appear to be a serious threat to the native species. As more habitat becomes urbanized, it is increasingly important to understand how freshwater turtles, such as E. marmorata, adapt to urban waterways and the impact of non-native turtles on native turtle species. Our strong feeling is that urban waterways can provide habitat for viable populations of freshwater turtles and showcase them to the public, but both the aquatic and terrestrial habitat must be managed according to the biological requirements of individual species.     

The western Pacific red lionfish, Pterois volitans (Scorpaenidae), in Florida: Evidence for reproduction and parasitism in the first exotic marine fish established in state waters

Many exotic fresh-water and brackish-water fish species have become established in Florida waters, but the red lionfish is the first entirely marine species that appears to have become established here. We give a detailed account of the initial collections of adult specimens from off St. Augustine and Jacksonville, including data on morphometrics, meristics, and gonad histology. Our review of historical sightings on Florida reefs and of the specimens reported herein suggests that the most plausible vector for the introduction of this fish was aquarium releases. We discuss our reasons for concluding that this species has probably become established in Florida, summarize the potential danger that these venomous fishes pose to the public, and examine the effect of a parasite hosted by the male lionfish. We also consider the potential effect of the red lionfish on marine communities in Florida, but limited information on its biology precludes a detailed assessment.     

Keystone effects of the endangered Stephens' kangaroo rat (Dipodomys stephensi)

Kangaroo rats (Dipodomys) have been argued to exert keystone effects because they interact strongly with other species, and their removal results in major changes in community structure. We evaluated the nature and magnitude of such impacts by the endangered Stephens' kangaroo rat (Dipodomys stephensi), employing an exclosure experiment to determine how the removal of this species impacted relative cover by vegetation, plant species diversity, abundance of a dominant annual plant genus (Erodium), and predation of seeds from artificial trays. Fifteen months of D. stephensi removal resulted in significant increases in herb cover and Erodium abundance, and significant declines in bare ground and in seed predation. These results support the hypothesis that D. stephensi has major impacts on plant community structure and seems to function as a keystone species. It remains to be seen how the loss of this species from much of its range will influence local community composition and dynamics.     

Impact of the colonisation of Zaprionus (Diptera, Drosophilidae) in different ecosystems of the Neotropical Region: 2 years after the invasion

The drosophilid Zaprionus indianus was not collected in Brazil, despite on-going drosophilid collecting, until 1999. Since 1999 this species has become common in Brazil. We present data on collections of Z. indianus in central Brazil, since its first occurrence in this region, with the goal of discussing its route of introduction in South America and aspects of its adaptation to the environment. Collections made during a 2-year period show different seasonal distribution patterns of this insect. In contrast with the low population sizes registered in 1999, during the summer of 2000 a large proliferation of this insect was detected. We show that Z. indianus is more common in the savanna sites and that its population peaks during the wet season. These preferences are discussed, and the hypothesis that the introduction in South America should have occurred in the southeast region of this continent is defended.     

Feeding activity of the earthworm Eisenia andrei in artificial soil

Quantitative information on the feeding activity of earthworms is scarce but this information is valuable in many eco(toxico)logical studies. In this study, the feeding activity of the compost worm Eisenia andrei is examined in artificial soil (OECD medium), with and without a high-quality food source (cow manure), and at two temperatures (10 and 20 °C). Methods are provided to estimate the most important parameters: gut load, selection of organic matter (OM), digestion efficiency, compaction, gut retention time, and fraction of manure in the diet. Lanthanides (Lu and Tm) were successfully used as inert markers in soil and manure, and we applied Bayesian statistics to analyse the data and fully capture the compounded uncertainty in the parameter estimates. Results show that the compost worm does not feed on soil indiscriminately but is able to select an OM-enriched diet from apparently homogeneous OECD medium. When manure is present on the soil surface, approximately three-quarters of the diet still consists of soil particles. The gut load of the worms was approximately 10% (dwt gut/wwt empty worm), varying little with the treatments. Unfortunately, the digestion efficiency could only be reliably estimated at 20 °C, and was approximately 40%. Temperature clearly affected feeding as a 10° temperature decrease nearly doubled the gut retention time (from 2.9 to 5.5 h), which corresponds to a two-fold decrease in feeding rate. The present data may be used to interpret toxicity and accumulation studies with E. andrei in OECD medium. However, care must be taken, as it seems possible that feeding is influenced by the size of the worm and subtle differences in experimental set-up.     

First indications for the involvement of strigolactones on nodule formation in alfalfa (Medicago sativa)

Strigolactones have recently been suggested to be phytohormones that are present in all plants. Strigolactones are released by roots into the rhizosphere, stimulating the seed germination of parasitic plants such as Striga spp. and Orobanche spp. and play a crucial role in the interaction between plants and symbiotic arbuscular mycorrhizal fungi.By applying different concentrations of the synthetic strigolactone analogue GR24 to alfalfa (Medicago sativa) inoculated with Sinorhizobium meliloti we could show that in alfalfa nodulation is positively affected by the presence of the strigolactone analogue GR24. Moreover, we could show that this increased nodulation cannot be linked with a stimulatory effect of GR24 on the growth or the expression of nod genes of S. meliloti.Putative mechanisms operating in the plant in response to the addition of GR24 and leading to increased nodule formation by rhizobia are discussed.     

Controlled ectomycorrhization of an exotic legume tree species Acacia holosericea affects the structure of root nodule bacteria community and their symbiotic effectiveness on Faidherbia albida, a native Sahelian Acacia

Many fast growing tree species have been introduced to promote biodiversity rehabilitation on degraded tropical lands. Although it has been shown that plant productivity and stability are dependent on the composition and functionalities of soil microbial communities, more particularly on the abundance and diversity of soil symbiotic micro-organisms (mycorrhizal fungi and rhizobia), the impact of tree introduction on soil microbiota has been scarcely studied. This research has been carried in a field plantation of Acacia holosericea (Australian Acacia species) inoculated or not with an ectomycorrhizal fungus isolate, Pisolithus albus IR100. After 7 year's plantation, the diversity and the symbiotic properties of Bradyrhizobia isolated from the plantation soil or from the surrounding area (Faidherbia albida (Del.) a. Chev. parkland) and able to nodulate F. albida, a native Sahelian Acacia species, have been studied. Results clearly showed that A. holosericea modified the structure of Bradyrhizobia populations and their effectiveness on F. albida growth. This negative effect was counterbalanced by the introduction of an ectomycorrhizal fungus, P. albus, on A. holosericea root systems.In conclusion, this study shows that exotic plant species can drastically affect genotypic and symbiotic effectiveness of native Bradyrhizobia populations that could limit the natural regeneration of endemic plant species such as F. albida. This effect could be counterbalanced by controlled ectomycorrhization with P. albus. These results have to be considered when exotic tree species are used in afforestation programs that target preservation of native plants and soil ecosystem rehabilitation.     

Mycorrhizal alleviation of acid soil stress in the sweet potato (Ipomoea batatas)

It is not known why sweet potato (Ipomoea batatas) cultivated in tropical regions tolerates acid soil. Here, we report the involvement of mycorrhizal symbiosis in this tolerance. Plants were grown in root-boxes filled with either acidic soil (pH 4.2) or the same soil amended with lime (pH 5.2) for 30 d in a growth chamber. In the inoculated treatments, the percentage of root length colonized by Gigaspora margarita was not affected by soil pH (23±9% at pH 4.2 vs. 30±12% at pH 5.2). The root and shoot dry weights of the non-mycorrhizal plants at pH 4.2 were 27 and 35%, respectively, of those at pH 5.2. The root and shoot dry weights of the mycorrhizal plants at pH 4.2 were 70 and 51% of those at pH 5.2. Growth promotion in mycorrhizal plants was significant only at pH 4.2 (2-fold increase in whole plant dry weight), but not at pH 5.2. As a result, no significant difference was detected in whole plant dry weight between the mycorrhizal plants at pH 4.2 and non-mycorrhizal plants at pH 5.2. The mycorrhizal plants at pH 4.2 showed reduced toxic symptoms of Mn (brown specks on mature leaves) and Al (poor root growth) compared to non-mycorrhizal ones, but tissue concentrations of P, K and Ca did not increase in mycorrhizal plants. We assume that the mycorrhizal colonization can reduce toxic effects of those elements while the exact mechanisms should be further investigated.     

Correlates of abundance and breeding success in the globally threatened Hinde's babbler (Turdoides hindei) and its congener, northern pied babbler (T. hypoleucus)

We investigated the relationship between habitat quality, abundance, group size and breeding success in the threatened Kenyan endemic Hinde's babbler (Turdoides hindei; Family Timaliidae), a co-operative breeder mainly associated with riverine thickets in cultivated areas. At two intensively cultivated sites, significantly more Hinde's babbler groups occurred in areas retaining at least 3% thicket cover, while breeding outcome improved where cover exceeded 9%. Despite previous concerns over low breeding success, the percentage of young birds present (17%, n=424 birds aged) was similar to that of a sympatric congener, the northern pied babbler (T. hypoleucus) (12%, n=162), and comparable with that of two other African congeners. Although breeding outcome was positively correlated with adult group size, there was no evidence that larger groups monopolised more favourable habitat or defended larger territories. Group density showed a positive, non-linear relationship with adjacent cover, levelling out where this exceeded 15-20%. Our findings suggest that even a modest increase in thicket cover may significantly raise the density and productivity of Hinde's babblers at these sites.     

Suicide vectors for the introduction of genetic markers into Bradyrhizobium strains by site-directed chromosomal integration between repeated sequences (RS-α)

To achieve stable expression of the heterologous and reporter genes in the Bradyrhizobium genome, we constructed suicide plasmids capable of site-directed genomic integration of the gusA, gfp and nifA genes by homologous recombination into non-essential repeated sequences (RS-α), isolated from B. japonicum strain CPAC7 (SEMIA5080). In this report, we describe the strategies to construct the vectors and their use to obtain mutants with site-specific insertions.     

Physiological evidence for reproductive suppression in the introduced population of brown tree snakes (Boiga irregularis) on Guam

Introduced species are an increasingly pervasive problem. While studies on the ecology and behavior of these pests are numerous, there is relatively little known of their physiology, specifically their reproductive and stress physiology. One of the best documented introduced pest species is the brown tree snake, Boiga irregularis, which was introduced onto the Pacific island of Guam sometime around World War II. The snake is responsible for severely reducing Guam's native vertebrates. We captured free-living individuals throughout the year and measured plasma levels of stress and sex hormones in an effort to determine when they were breeding. These data were compared to reproductive cycles from a captive population originally collected from Guam. Free-living individuals had chronically elevated plasma levels of the stress hormone corticosterone and basal levels of sex steroids and a remarkably low proportion were reproductively active. These data coincide with evidence that the wild population may be in decline. Captive snakes, had low plasma levels of corticosterone with males displaying a peak in plasma testosterone levels during breeding. Furthermore, we compared body condition between the free-living and captive snakes from Guam and free-living individuals captured from their native range in Australia. Male and female free-living snakes from Guam exhibited significantly reduced body condition compared to free-living individuals from Australia. We suggest that during the study period, free-living brown tree snakes on Guam were living under stressful conditions, possibly due to overcrowding and overexploitation of food resources, resulting in decreased body condition and suppressed reproduction.     

New insights into the origins and evolution of rhizobia that nodulate common bean (Phaseolus vulgaris) in Brazil

It is generally accepted that there are two major centers of genetic diversification of common beans (Phaseolus vulgaris L.): the Mesoamerican (Mexico, Colombia, Ecuador and north of Peru, probably the primary center), and the Andean (southern Peru to north of Argentina) centers. Wild common bean is not found in Brazil, but it has been grown in the country throughout recorded history. Common bean establishes symbiotic associations with a wide range of rhizobial strains and Rhizobium etli is the dominant microsymbiont at both centers of genetic diversification. In contrast, R. tropici, originally recovered from common bean in Colombia, has been found to be the dominant species nodulating field-grown common-bean plants in Brazil. However, a recent study using soil dilutions as inocula has shown surprisingly high counts of R. etli in two Brazilian ecosystems. In the present study, RFLP-PCR analyses of nodABC and nifH genes of 43 of those Brazilian R. etli strains revealed unexpected homogeneity in their banding patterns. The Brazilian R. etli strains were closely similar in 16S rRNA sequences and in nodABC and nifH RFLP-PCR profiles to the Mexican strain CFN 42^T, and were quite distinct from R. etli and R. leguminosarum strains of European origin, supporting the hypothesis that Brazilian common bean and their rhizobia are of Mesoamerican origin, and could have arrived in Brazil in pre-colonial times. R. tropici may have been introduced to Brazilian soils later, or it may be a symbiont of other indigenous legume species and, due to its tolerance to acidic soils and high temperature conditions became the predominant microsymbiont of common bean.