Binding of Trypanosoma congolense to the Walls of Small Blood Vessels*

SYNOPSIS The mesenteric microvasculature was studied in rats and rabbits infected with Trypanosoma congolense. By examining vessels in the living animals, trypanosomes were observed to adhere to vessel walls by their anterior ends. It was evident from stained preparations of the vessels that the microcirculation contained 4–1400 times as many trypanosomes as were free in the cardiac blood. Parasites were more numerous in very small vessels than in larger vessels, and they were clustered in groups within the small vessels. The localization of T. congolense in the microvasculature is demonstrated and it is shown that this localization is established by attachment of the organism to the vessel wall.     

Embryogenesis: a Question of Pattern

Embryogenesis in plants appears superficially to be a relativelysimple process in terms of morphological development and itis the case that most organogenesis takes place in the post-embryonicphase of the life cycle. This apparent simplicity allows usto exploit embryogenesis as a model experimental system to studythe relationship between gene expression and morphogenesis,which is arguably the most important question in developmentalbiology. However, we are only just beginning to describe changesin gene expression during embryogenesis and to identify regulatorynetworks. Recent work, exploiting transgenic techniques andthe generation and characterization of mutants, points the wayahead in dissecting this developmental process at the molecularlevel. Key words: Plant embryogenesis, pattern formation, developmental mutants, gene expression     

Detection Dogs: An Effective Technique for Bush Dog Surveys

ABSTRACT Detailed ecological data on the bush dog (Speothos venaticus) have been lacking, since standard field techniques, such as camera traps, have had little success recording their presence. This study eliminates dependence on visitation rate and switches the focus to locating evidence (e.g., olfactory) associated with the species’ natural behavior and movement patterns. Over a 3-month period, a detection dog located multiple (n = 11, 4 confirmed and 7 potential) bush dog areas in Upper Paraná Atlantic Forest of Misiones Argentina. These positive results demonstrate that detection dogs can provide species-specific data on the bush dog despite the rugged terrain and dense forest vegetation they may occupy. The ecological data collected using this technique allow effective conservation strategies to be developed, wildlife corridors and biological crossings to be designed, and species distributions to be examined.     

Linking ecological function to species composition in ecological restoration: Seed removal by ants in recreated woodland

Evaluations of ecological restoration typically focus on associating measures of structural properties of ecosystems (e.g. species diversity) with time since restoration efforts commenced. Such studies often conclude a failure to achieve restoration goals without examining functional performance of the organism assemblages in question. We compared diversity and composition of ant assemblages and the rates of seed removal by ants in pastures, 4‐ to 10‐year old revegetated areas and remnants of Cumberland Plain Woodland, and an endangered ecological community in Sydney, Australia. Ant assemblages of forest remnant sites had significantly higher species richness, significantly different species composition and a more complex functional group structure in comparison with ant assemblages of pasture and revegetated sites, which did not differ significantly. However, the rates of seed removal by ants in revegetated sites were similar to those in forest remnants, with the rates in pasture sites being significantly lower. Approximately, one‐third of all ant species were observed to remove seeds. Forest remnant sites had significantly different assemblages of seed removing ant species from those in pasture and revegetated sites. These results demonstrate that similar ant assemblages of unrestored and restored areas can function differently, depending on habitat context. Evaluation of restoration success by quantifying ecosystem structure and function offers more insights into ecosystem recovery than reliance on structural data alone.     

Effects of floods on fish assemblages in an intermittent prairie stream

1. Floods are major disturbances to stream ecosystems that can kill or displace organisms and modify habitats. Many studies have reported changes in fish assemblages after a single flood, but few studies have evaluated the importance of timing and intensity of floods on long‐term fish assemblage dynamics. 2. We used a 10‐year dataset to evaluate the effects of floods on fishes in Kings Creek, an intermittent prairie stream in north‐eastern, Kansas, U.S.A. Samples were collected seasonally at two perennial headwater sites (1995–2005) and one perennial downstream flowing site (1997–2005) allowing us to evaluate the effects of floods at different locations within a watershed. In addition, four surveys during 2003 and 2004 sampled 3–5 km of stream between the long‐term study sites to evaluate the use of intermittent reaches of this stream. 3. Because of higher discharge and bed scouring at the downstream site, we predicted that the fish assemblage would have lowered species richness and abundance following floods. In contrast, we expected increased species richness and abundance at headwater sites because floods increase stream connectivity and create the potential for colonisation from downstream reaches. 4. Akaike Information Criteria (AIC) was used to select among candidate regression models that predicted species richness and abundance based on Julian date, time since floods, season and physical habitat at each site. At the downstream site, AIC weightings suggested Julian date was the best predictor of fish assemblage structure, but no model explained >16% of the variation in species richness or community structure. Variation explained by Julian date was primarily attributed to a long‐term pattern of declining abundance of common species. At the headwater sites, there was not a single candidate model selected to predict total species abundance and assemblage structure. AIC weightings suggested variation in assemblage structure was associated with either Julian date or local habitat characteristics. 5. Fishes rapidly colonised isolated or dry habitats following floods. This was evidenced by the occurrence of fishes in intermittent reaches and the positive association between maximum daily discharge and colonisation events at both headwater sites. 6. Our study suggests floods allow dispersal into intermittent habitats with little or no downstream displacement of fishes. Movement of fishes among habitats during flooding highlights the importance of maintaining connectivity of stream networks of low to medium order prairie streams.     

Value of long‐term ecological studies

Long‐term ecological studies are critical for providing key insights in ecology, environmental change, natural resource management and biodiversity conservation. In this paper, we briefly discuss five key values of such studies. These are: (1) quantifying ecological responses to drivers of ecosystem change; (2) understanding complex ecosystem processes that occur over prolonged periods; (3) providing core ecological data that may be used to develop theoretical ecological models and to parameterize and validate simulation models; (4) acting as platforms for collaborative studies, thus promoting multidisciplinary research; and (5) providing data and understanding at scales relevant to management, and hence critically supporting evidence‐based policy, decision making and the management of ecosystems. We suggest that the ecological research community needs to put higher priority on communicating the benefits of long‐term ecological studies to resource managers, policy makers and the general public. Long‐term research will be especially important for tackling large‐scale emerging problems confronting humanity such as resource management for a rapidly increasing human population, mass species extinction, and climate change detection, mitigation and adaptation. While some ecologically relevant, long‐term data sets are now becoming more generally available, these are exceptions. This deficiency occurs because ecological studies can be difficult to maintain for long periods as they exceed the length of government administrations and funding cycles. We argue that the ecological research community will need to coordinate ongoing efforts in an open and collaborative way, to ensure that discoverable long‐term ecological studies do not become a long‐term deficiency. It is important to maintain publishing outlets for empirical field‐based ecology, while simultaneously developing new systems of recognition that reward ecologists for the use and collaborative sharing of their long‐term data sets. Funding schemes must be re‐crafted to emphasize collaborative partnerships between field‐based ecologists, theoreticians and modellers, and to provide financial support that is committed over commensurate time frames.     

Aspects of insect chemical ecology: exploitation of reception and detection as tools for deception of pests and beneficial insects

Empirical exploitation of insect reception and detection at the peripheral neurosensory level has been extremely valuable for identifying pheromones and other semiochemicals, mainly by electroantennogram or single cell preparations coupled with capillary gas chromatography. Differential sensitivity to semiochemicals at the single‐cell level has allowed the identification of some of the most active semiochemicals relating to host location and, more importantly, to the avoidance of nonhosts. However, in terms of molecular recognition, there is still a considerable gap in understanding the detection of particular molecules and their discrimination from closely‐related chemical structures. New approaches will be needed to understand the processes of molecular recognition more precisely. Nevertheless, from electrophysiological studies to the most advanced molecular techniques, it has been possible to identify semiochemicals for the deception of pests in their quest to find plant and animal hosts, as well as mates. Even the deception of insects antagonistic to pests, particularly parasitoids, can now be exploited for managing pests in more sustainable systems. Successes in exploiting insect semiochemicals in the interests of better agriculture and animal husbandry are exemplified, and potential new ways of learning more about reception and detection for deception are discussed. This takes the subject beyond the management of pest and beneficial insects to wider commercial and social opportunities.     

Differing contributions of density dependence and climate to the population dynamics of three eruptive herbivores

1. Although both endogenous and exogenous processes regulate populations, the current understanding of the contributions from density dependence and climate to the population dynamics of eruptive herbivores remains limited. 2. Using a 17‐year time series of three cereal aphid species [Rhopalosiphum padi L., Metopolophium dirhodum (Walker), and Diuraphis noxia (Kurdumov)] compiled from a trapping network spanning the northwestern U.S.A., temporal and spatial patterns associated with population fluctuations, and modelled density dependence in aphid abundances were tested. These models were used to analyse correlations between climate and aphid abundances in the presence and absence of residual variance as a result of density‐dependent effects. 3. The temporal dynamics of aphid population fluctuations indicated periodicity, with no clear evidence for a spatial pattern underlying population fluctuations. 4. Aphid abundances oscillated in a manner consistent with delayed density dependence for all three aphid species, although the strength of these feedbacks differed among species. 5. Diuraphis noxia abundances were negatively correlated with increasing temperatures in the absence of density‐dependent effects, whereas M. dirhodum abundances were positively correlated with increasing cumulative precipitation in the presence of density‐dependent effects; yet, R. padi abundances were unrelated to climate variables irrespective of population feedbacks. 6. Our analysis suggests that endogenous feedbacks differentially regulate aphid populations in the northwestern U.S.A., and these feedbacks may operate at an expansive spatial scale. It is concluded that the contributions of density dependence and climate to aphid population dynamics are species‐specific in spite of similar ecological niches, with implications for assessing species responses to climate variability.     

Fast movement of densely aggregated prey increases the strength of anti-apostatic selection by wild birds

'Anti-apostatic' selection occurs when predators preferentially remove rare forms of prey, and has been demonstrated in both static (artificial) prey and moving (natural) prey. We performed 24 experiments at separate sites to test the effect of prey mobility on the strength of anti-apostatic selection by wild passerine birds. The prey were yellow and red Calliphora maggots and were presented in 9: 1 and 1: 9 ratios on a specially designed bird table. The temperature of the maggots, and hence their speed of movement, was adjusted by a combination of the ambient temperature and a candle under the bird table. Selection was anti-apostatic at all three classes of temperature and was strongest at the highest. We conclude that anti-apostatic selection on static prey is enhanced when they are made to move–possibly because the 'confusion effect' caused by the moving prey makes the birds concentrate more strongly on the rarer colours.     

Polymorphic microsatellite loci from the American goldfinch (Carduelis tristis) and their cross‐amplification in a variety of passerine species

Cardueline finches have become important models in studies of sexual selection. Here I describe eight polymorphic microsatellite loci isolated from the American goldfinch (Carduelis tristis) that are useful in parentage and heterozygosity studies. The number of alleles per locus ranged from eight to 38 based on 252 goldfinches. The markers are polymorphic in at least four other Cardueline finch species, and several amplify in nonfinch passerines including red‐winged blackbird (Agelaius phoeniceus), black‐throated blue warbler (Dendroica caerulescens) and tufted titmouse (Baeolophus bicolor), indicating they should be useful in paternity and population studies of a variety of species.