Establishment of exotic parasites: the origins and characteristics of an avian malaria community in an isolated island avifauna

Knowledge of the processes favouring the establishment of exotic parasites is poor. Herein, we test the characteristics of successful exotic parasites that have co-established in the remote island archipelago of New Zealand, due to the introduction of numerous avian host species. Our results show that avian malaria parasites (AM; parasites of the genus Plasmodium) that successfully invaded are more globally generalist (both geographically widespread and with a broad taxonomic range of hosts) than AM parasites not co-introduced to New Zealand. Furthermore, the successful AM parasites are presently more prevalent in their native range than AM parasites found in the same native range but not co-introduced to New Zealand. This has resulted in an increased number and greater taxonomic diversity of AM parasites now in New Zealand.     

Cavity type influences abundance of nest-dwelling avian blow flies: an experiment with tree swallows

1. Diverse assemblages of blood-feeding parasitic arthropods occupy the nests of birds, and nest temperature and humidity can strongly influence the population dynamics of these ectoparasites, with important implications for parasite–host relationships. 2. This study used two types of nest box that differed in internal microclimates, one constructed of plywood and the other constructed of boles of aspen (Populus tremuloides Michx.), more closely replicating natural cavities, to examine how nest microclimate affects the prevalence and abundance of nest-dwelling larval blow flies (Protocalliphora and Trypocalliphora spp.) in nests of tree swallows (Tachycineta bicolor Vieillot, 1808). 3. Based on known microclimatic differences between the box types and responses of larval blow flies to different temperatures, it was predicted that the microclimate of plywood boxes would be more favourable for growth and development of larval blow flies, and therefore have higher abundance, and possibly higher prevalence, of larval blow flies. 4. Plywood nest boxes had higher abundance, but not prevalence, of larval blow flies compared with aspen boxes at two different geographical locations in Canada. Nest composition also differed between box types, particularly at one site, where aspen boxes contained more nesting material (grass and feathers) than did plywood boxes. 5. Although it seems probable that microclimate was driving the differences between box types in abundance of larval blow flies, several additional explanations are discussed. These findings may have implications for conservation efforts, particularly those where nest boxes are used to aid in the recovery of declining bird populations.     

Reducing complexity when studying seed dispersal at community scales: a functional classification of vertebrate seed dispersers in tropical forests

The process of seed dispersal has a profound effect on vegetation structure and diversity in tropical forests. However, our understanding of the process and our ability to predict its outcomes at a community scale are limited by the frequently large number of interactions associated with it. Here, we outline an approach to dealing with this complexity that reduces the number of unique interactions considered by classifying the participants according to their functional similarity. We derived a classification of dispersers based on the nature of the dispersal service they provide to plants. We described the quantities of fruit handled, the quality of handling and the diversity of plants to which the service is provided. We used ten broad disperser traits to group 26 detailed measures for each disperser. We then applied this approach to vertebrate dispersers in Australia’s tropical forests. Using this we also develop a classification that may be more generally applicable. For each disperser, data relating to each trait was obtained either from the field or published literature. First, we identified dispersers whose service outcomes were so distinct that statistical analysis was not required and assigned them to functional groups. The remaining dispersers were assigned to functional groups using cluster analysis. The combined processes created 15 functional groups from 65 vertebrate dispersers in Australian tropical forests. Our approach—grouping dispersers on the basis of the type of dispersal service provided and the fruit types it is provided to—represents a means of reducing the complexity encountered in tropical seed dispersal systems and could be effectively applied in community level studies. It also represents a useful tool for exploring changes in dispersal services when the distribution and abundance of animal populations change due to human impacts. Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at .     

Elevated air temperature alters an old-field insect community in a multifactor climate change experiment

To address how multiple, interacting climate drivers may affect plant–insect community associations, we sampled insects that naturally colonized a constructed old‐field plant community grown for over 2 years under simultaneous CO₂, temperature, and water manipulation. Insects were sampled using a combination of sticky traps and vacuum sampling, identified to morphospecies and the insect community with respect to abundance, richness, and evenness quantified. Individuals were assigned to four broad feeding guilds in order to examine potential trophic level effects. Although there were occasional effects of CO₂ and water treatment, the effects of warming on the insect community were large and consistent. Warming significantly increased Order Thysanoptera abundance and reduced overall morphospecies richness and evenness. Nonmetric multidimensional scaling found that only temperature affected insect community composition, while a Sørensen similarity index showed less correspondence in the insect community between temperature treatments compared with CO₂ or soil water treatments. Within the herbivore guild, elevated temperature significantly reduced richness and evenness. Corresponding reductions of diversity measures at higher trophic levels (i.e. parasitoids), along with the finding that herbivore richness was a significant predictor of parasitoid richness, suggest trophic‐level effects within the insect community. When the most abundant species were considered in temperature treatments, a small number of species increased in abundance at elevated temperature, while others declined compared with ambient temperature. Effects of temperature in the dominant insects demonstrated that treatment effects were limited to a relatively small number of morphospecies. Observed effects of elevated CO₂ concentration on whole‐community foliar N concentration did not result in any effect on herbivores, which are probably the most susceptible guild to changes in plant nutritional quality. These results demonstrate that climatic warming may alter certain insect communities via effects on insect species most responsive to a higher temperature, contributing to a change in community structure.     

Biologic interactions determining geographic range size: a one species response to phylogenetic community structure

Range size variation in closely related species suggests different responses to biotic and abiotic heterogeneity across large geographic regions. Species turnover generates a wide spectrum of species assemblages, resulting in different competition intensities among taxa, creating restrictions as important as environmental constraints. We chose to adopt the widely used phylogenetic relatedness (NRI) measurement to define a metric that depicts competition strength (via phylogenetic similarity), which one focal species confronts in its environment. This new approach (NRI_focal) measures the potential of the community structure effect over performance of a single species. We chose two ecologically similar Peucaea sparrows, which co‐occur and have highly dissimilar range size to test whether the population response to competition intensity is different between species. We analyzed the correlation between both Peucaea species population sizes and NRI_focal using data from point counts. Results indicated that the widespread species population size was not associated with NRI_focal, whereas the population of restricted‐sized species exhibited a negative relationship with competition intensity. Consequently, a species' sensitivity to competition might be a limiting factor to range expansion, which provides new insights into geographic range analysis and community ecology.     

Predators and priority effects suggested as potential drivers of microfauna communities in a community transplantation experiment along an elevational gradient

Transplantation experiments are a useful method to identify responses of organisms to environmental change. However, they are typically restricted to single or few species. Our experiment was carried out using entire bromeliad‐inhabiting microfauna communities which were transplanted along an elevational gradient, simulating environmental change acting on the communities. Additionally, we manipulated trophic interactions, i.e. resource availability and predator presence, thus combining abiotic and biotic effects in a full‐factorial experimental design. Using this experiment, we found a strong signal of original elevation in microfauna community structure (abundance, evenness, functional composition) with a shift from amoeba‐dominated to flagellate‐dominated communities with increasing original elevation. Surprisingly, the transplantation of communities along the elevational gradient did not affect community structure, indicating strong priority effects. Predation decreased microfauna abundance and increased microfauna evenness, specifically in higher original elevation and high resource levels. In summary, our results suggest that microfauna communities in bromeliads might be primarily shaped by priority effects and predator presence. However, interacting effects (between predator presence and resource availability, as well as between predator presence and original elevation) highlight the usefulness of studies with full‐factorial experimental designs to understand community‐structuring processes. Bromeliads and other micro‐ecosystems provide convenient study systems for community level approaches that could be used in future studies concerning the effects of environmental change, for example climate change on community structure.     

Experimental slab salvage and reinstatement after pipeline construction in a threatened grassland community

The protection and management of grasslands is a priority to conserve biodiversity, particularly in fragmented landscapes subject to human‐induced disturbance. We examined the success of salvage and reinstatement of multiple 90 m² slabs of modified temperate grassland in a pipeline construction corridor in south‐eastern Australia and compared it with a reinstated topsoil treatment (i.e. standard pipeline reinstatement practice) and an undisturbed control. Thirty‐six plots (each 9 × 10 m) representing the three treatments were monitored across six locations, pre‐ and postconstruction every 3 months for 2 years. We sampled 18 vegetation/habitat variables to examine the effect of treatments over time. Introduced grass cover was consistently higher than native grasses for both treatments, and the cover of introduced grasses increased over time in both treatments. Conversely, control plots had considerably higher native grass cover than the slab and reinstated topsoil treatments. Native species richness was not negatively affected by the slab reinstatement process. Our results suggest that in this instance, slab replacement was an ineffective way to reinstate native grasslands, as it appeared to confer minimal benefit when compared to the standard practice of reinstating topsoil. This was most likely due to the high degree of disturbance to slabs during the reinstatement process.     

Foraging ecology drives social information reliance in an avian eavesdropping community

Vertebrates obtain social information about predation risk by eavesdropping on the alarm calls of sympatric species. In the Holarctic, birds in the family Paridae function as sentinel species; however, factors shaping eavesdroppers' reliance on their alarm calls are unknown. We compared three hypothesized drivers of eavesdropper reliance: (a) foraging ecology, (b) degree of sociality, and (c) call relevance (caller‐to‐eavesdropper body‐size difference). In a rigorous causal‐comparative design, we presented Tufted Titmouse (Baeolophus bicolor) alarm calls to 242 individuals of 31 ecologically diverse bird species in Florida forests and recorded presence/absence and type (diving for cover or freezing in place) of response. Playback response was near universal, as individuals responded to 87% of presentations (N = 211). As an exception to this trend, the sit‐and‐wait flycatcher Eastern Phoebe (Sayornis phoebe) represented 48% of the nonresponses. We tested 12 predictor variables representing measures relevant to the three hypothesized drivers, distance to playback speaker, and vulnerability at time of playback (eavesdropper's microhabitat when alarm call is detected). Using model‐averaged generalized linear models, we determined that foraging ecology best predicted playback response, with aerial foragers responding less often. Foraging ecology (distance from trunk) and microhabitat occupied during playback (distance to escape cover) best predicted escape behavior type. We encountered a sparsity of sit‐and‐wait flycatchers (3 spp.), yet their contrasting responses relative to other foraging behaviors clearly identified foraging ecology as a driver of species‐specific antipredator escape behavior. Our findings align well with known links between the exceptional visual acuity and other phenotypic traits of flycatchers that allow them to rely more heavily on personal rather than social information while foraging. Our results suggest that foraging ecology drives species‐specific antipredator behavior based on the availability and type of escape cover.     

Heart targeting of retroviral expression in avian embryos: a species-independent phenomenon

A replication-incompetent retroviral vector derived from spleen necrosis virus (SNV), in which the viral structural genes gag, pol, and env were replaced with the bacterial -galactosidase gene lacZ, was used to infect embryos from outbred and inbred chicken lines, japanese quail and duck between embryonic day 0 and 13. LacZ expression was restricted to a few organs or cell types, and this distribution was not influenced by the different routes of inoculation tested but was specified by the age of the embryo at the time of inoculation. Inoculations at E0-E1 beneath or onto the blastodisc resulted in lacZ expression in ectodermal derivatives, i.e. skin and neural structures. From E2 onwards, heart muscle and skin were the preferential targets in all the species or inbred lines tested. Heart muscle was positive in 100% of the embryos displaying lacZ+ clones. Skin exhibited on and off periods depending on the age at inoculation. No lacZ-positive clones were detected in chick embryos infected after Ell. Outbred chick embryos displayed the largest array of organs labelled (heart, skin, liver, gizzard) while quail and duck embryos exhibited a more restrictive pattern. These results are of import if the vector is to be used as a tool to map lineages or to transfer genes into the developing embryo.     

Dietary niche breadth in a local community of passerine birds: an analysis using phylogenetic contrasts

The analysis of a local community of forest passerines (13 species) using phylogenetic contrasts shows a correlation between body size of bird species and mean prey size, minimum prey size, maximum prey size and the size range of dietary items. This suggests that larger birds drop small prey taxa from their prey list, because of the difficulty of capturing very small prey, for energetic reasons or because of microhabitat usage. We find some support for the third hypothesis. Dietary niche breadth calculated across prey taxa is not related to body size. Dietary niche breadth, however, is correlated with size-corrected measurements of the bill and locomotor apparatus. Long and slender bills increase the dietary niche breadth. Thus subtle differences constrain foraging and the techniques of extracting certain prey taxa form crevices. Dietary niche breadth and foraging diversity are positively correlated with population density: at least locally dietary generalists occur at higher breeding densities than specialists.     

瑞典南部落叶林动物对种子捕食的实验研究

在瑞典南部落叶林,于1985年和1986年秋季分别研究了不同动物对欧洲七叶树、夏栎、山楂和黑刺李等4种种子的捕食作用,即种子释放1周后被动物捕食的情况。实验分以下3种处理:排除小兽和鸟、排除鸟和对照(小兽和鸟均不排除),但昆虫可进入所有处理。在不同落叶林和小型林地共建有16个重复实验,即每个林分类型于每年秋季各设4个重复。在所有林分(包括落叶林和小型林地),不同处理的种子捕食表明:小兽是欧洲七叶树、夏栎和黑刺李等植物种子的主要捕食者,而无脊椎动物则是山楂种子的重要捕食者,但鸟类很少取食上述种子,因而捕食作用极小。在其中1年,动物对种子的总捕食率在落叶林和小型林地存在较大差异,以小型林地较高。     

Parasites in space and time: a case study of haemosporidian spatiotemporal prevalence in urban birds

Prevalence responses to anthropic factors differ across hosts and parasite species. We here analyzed the spatiotemporal variation of avian haemosporidian prevalence in bird assemblages of the Mooswald forest (i.e., urban greenspace; Freiburg, Germany), in response to local environmental features (e.g., water sources, human presence (visited)/absence (unvisited)) and bird-level traits (e.g., body condition, age, sex) in 2?years. We used a nested PCR protocol (mitochondrial (mt)DNA cytochrome b (cyt b) gene) and microscopy to determine haemosporidian infections. Prevalence was analyzed using a general linear multi-model (glmulti) approach with Akaike information criterion corrected for small samples (AICc), with subsequent model inferences using a GLMM on the best selected model, considering bird species as a random factor. Analyses were conducted for the main understory bird species (Blackcap – Sylvia atricapilla, Chaffinch – Coereba flaveola, Great Tit – Parus major, Blue Tit – Cyanistes caeruleus, European Robin – Erithacus rubecula, Blackbird – Turdus merula, Song Thrush – Turdus philomelos). We further conducted spatial autocorrelation analyses for all haemosporidian infections, and classification and regression trees (CARTs) for focal species. We analyzed a total of 544 samples of seven bird species. In 2011 prevalence for Haemoproteus/Plasmodium was 25.8% and 11.7% for Leucocytozoon. In 2013 prevalence for Haemoproteus/Plasmodium was 26.5% and 35.5% for Leucocytozoon. Haemosporidian prevalence was significantly different between some focal species. There was a negative association between distance to the nearest water source and prevalence in the year 2011, and the opposite pattern for the year 2013. However, when analyzed for the six focal species separately, such a relationship could change from a negative to a positive one, or there could be no relationship at all. For Leucocytozoon there was higher prevalence in the section of the forest visited by humans. We did not find spatial autocorrelation for prevalence across the study site, but there were statistically significant local spatial clusters in the visited section. Although there were similar responses of prevalence to some factors, infection patterns were generally bird species-specific. Thus, prevalence is a labile epidemiological parameter, varying spatiotemporally in an idiosyncratic way.     

Bounded hybrid superiority in an avian hybrid zone: effects of mate, diet, and habitat choice

There has been considerable debate in the study of hybrid zones as to whether hybrids may be superior to parental types within the area of contact (bounded hybrid superiority). In birds, naturally occurring hybridization is relatively common, and hybridization within this group always involves mate choice. If hybrids are superior, females choosing heterospecific mates should be expected to show higher fitness under the conditions prevalent in the hybrid zone. Hybrid superiority under these circumstances would reduce reinforcement and thereby help to maintain the hybrid zone. To examine this issue, we studied reproductive performances of hybrids and parental species of gulls (Larus occidentalis and Larus glaucescens) at two colonies within a linear hybrid zone along the west coast of the United States. This hybrid zone contains predominantly gulls of intermediate phenotype. Previous studies indicated that hybrids were superior to one or both parental types, but provided no data on possible mechanisms that underlie this hybrid superiority. Using a hybrid index designed specifically for these species, we identified to phenotype more than 300 individuals associated with nests, including both individual males and females within 73 pairs in the central portion of the hybrid zone and 74 pairs in the northern portion of the hybrid zone. There was little evidence of assortative mating, and what little there was resulted solely because of pairings within intergrades. In the central hybrid zone, females paired with hybrid males produced larger clutches and hatched and fledged more chicks compared with females paired to western gull males. This was a result of heavy predation on eggs in sand habitat, where male western gulls established territories. In contrast, many hybrid males established territories in vegetated cover that was less vulnerable to predation. In the northern part of the hybrid zone, clutch size did not differ among pair categories, however, there were differences in hatching and fledging success, with females paired to hybrid males showing better success compared to females paired to glaucous-winged gull males. Hybrids showed better hatching and fledging success in the north because hybrids are more like western gulls than glaucous-winged gulls in foraging behavior, taking a higher percentage of fish in their diet, which enhances chick growth and survival. This is believed to be the first documentation of bounded hybrid superiority that delineates the mechanisms that underlie hybrid superiority.     

Floristic assessment of an Afromontane grassland fragmentation experiment in a pine plantation

Twenty-four grassland fragments were established in an area of high botanical diversity planted with Pinus patula plantations. This area is representative of the eastern Drakensberg escarpment, containing a large number of endemic plant taxa. The experimental fragments comprise six replicates of two fragment sizes (0.25 and 1.5 ha), with a similar grouping of control plots in adjacent undisturbed grassland designated for conservation. The plots form the basis of a long-term study on fragmented plant and animal communities. Vegetation surveys were performed using nearest neighbour step point and Braun–Blanquet techniques. Analysis of similarity (anosim ) indicates that in neither the large nor small fragments do the control plots differ significantly in floristic structure from the experimental fragments. Five variations of the Themeda triandra-dominated grassland were identified, corresponding to slight variations in ground moisture. The experimental fragments and control plots were sufficiently similar to be analysed as replicates within the fragmentation study. This forms the foundation for the long-term analysis of plant communities within the fragments, as well as for analyses of insect and vertebrate communities within the fragments.     

Avoiding Predators: Expectations and Evidence in Primate Antipredator Behavior

Predation and antipredator behavior are important but poorly studied influences on the evolution of primate societies. I review recent evidence of predation and antipredator strategies among primates. I describe patterns of antipredator behavior and attempt to explain the variation among primate taxa and among antipredator strategies. I use predation by chimpanzees on red colobus and antipredator strategies by the colobus as a case study of how a primate prey species may respond to the threat of predation.     

Different nest predator faunas and nest predation risk on ground and shrub nests at forest ecotones: an experiment and a review

This study examined predator faunas of artificial ground and shrub nests and whether nest predation risk was influenced by nest site, proximity to forest edge, and habitat structure in 38 grassland plots in south-central Sweden. There was a clear separation of predator faunas between shrub and ground nests as identified from marks in plasticine eggs. Corvids accounted for almost all predation on shrub nests whereas mammals mainly depredated ground nests. Nest predation risk was significantly greater for shrub than for ground nests at all distances (i.e. 0, 15 and 30 m) from the forest edge. However, nest predation risk was not significantly related to distance to forest edge, but significantly increased with decreasing distance to the nearest tree. Different corvid species robbed nests at different distances from the forest edge, with jays robbing nests closest to edges. We conclude that the relationship between the predation risk of grassland bird nests and distance to the forest edge mainly depends on the relative importance of different nest predator species and on the structure of the forest edge zone. A review of published articles on artificial shrub and ground nest predation in the temperate zone corroborated the results of our own study, namely that shrub nests experienced higher rates of depredation in open habitats close to the forest edge and that avian predators predominantly robbed shrub nests. Furthermore, the review results showed that predation rates on nests in general are highest <50 m inside the forest and lower in open as well as forest interior habitats (≥50 m from the edge). Received: 16 March 1998 / Accepted: 30 July 1998     

Species richness effects on grassland recovery from drought depend on community productivity in a multisite experiment

Biodiversity can buffer ecosystem functioning against extreme climatic events, but few experiments have explicitly tested this. Here, we present the first multisite biodiversity × drought manipulation experiment to examine drought resistance and recovery at five temperate and Mediterranean grassland sites. Aboveground biomass production declined by 30% due to experimental drought (standardised local extremity by rainfall exclusion for 72–98 consecutive days). Species richness did not affect resistance but promoted recovery. Recovery was only positively affected by species richness in low‐productive communities, with most diverse communities even showing overcompensation. This positive diversity effect could be linked to asynchrony of species responses. Our results suggest that a more context‐dependent view considering the nature of the climatic disturbance as well as the productivity of the studied system will help identify under which circumstances biodiversity promotes drought resistance or recovery. Stability of biomass production can generally be expected to decrease with biodiversity loss and climate change.     

Microbial community structure and functions differ between native and novel (exotic-dominated) grassland ecosystems in an 8-year experiment

Plant and Soil - Grasslands dominated by non-native (exotic) species have replaced purely native-dominated areas in many parts of the world forming ‘novel’ ecosystems. Altered...     

Forward hysteresis and backward bifurcation caused by culling in an avian influenza model

The emerging threat of a human pandemic caused by the H5N1 avian influenza virus strain magnifies the need for controlling the incidence of H5N1 infection in domestic bird populations. Culling is one of the most widely used control measures and has proved effective for isolated outbreaks. However, the socio-economic impacts of mass culling, in the face of a disease which has become endemic in many regions of the world, can affect the implementation and success of culling as a control measure. We use mathematical modeling to understand the dynamics of avian influenza under different culling approaches. We incorporate culling into an SI model by considering the per capita culling rates to be general functions of the number of infected birds. Complex dynamics of the system, such as backward bifurcation and forward hysteresis, along with bi-stability, are detected and analyzed for two distinct culling scenarios. In these cases, employing other control measures temporarily can drastically change the dynamics of the solutions to a more favorable outcome for disease control.     

Effects of water-level fluctuations on the littoral benthic fish community in lakes: a mesocosm experiment

Changes in the water level of lakes, either natural or man-made,are important environmental perturbations for eulittoral benthicfish communities. In outdoor mesocosm experiments, we testedthe effects of decreasing shelter availability due to autumnlake-level decrease on the behavior and the growth of two littoralbenthic dwellers, the juvenile burbot and the stone loach. Thetwo species showed significantly different changes in behaviorwhen shelter availability decreased. Burbot built up a distincthierarchy when shelter became sparse, with larger fish beingsignificantly more successful in competing for suitable shelterthan smaller conspecifics. The hierarchy, however, ceased whenshelter availability decreased below a certain level. The largestfish then increasingly abandoned shelter use, while smallerfish persisted with their sheltering behavior. Stone loach,in contrast, showed no hierarchical order or size-related shelteruse. Only burbot showed a significant relationship between theability to occupy the preferred shelter and the somatic growth.These two species provide an example of different strategiesto deal with environmental perturbations like lake-level decrease,with the stenoecious, dominant strategy of the burbot and theeuryoecious, evasive strategy of stone loach. The results demonstratethe importance of conducting behavioral studies under as naturalconditions as possible.