How robust are Palearctic migrants to habitat loss and degradation in the Sahel?

The Sahel region of West Africa is an important wintering ground for Palearctic migrants. It is, however, undergoing significant anthropogenic degradation that is likely to reduce its value in this regard. Despite there being evidence that the populations of several Palearctic species may be determined by conditions on their Sahelian wintering grounds, there are almost no baseline data on their habitat use there and so the effects that habitat change might have on their future density and distribution cannot be determined. This study measured which habitat variables were associated with the presence of Common Whitethroat Sylvia communis, Lesser Whitethroat S. curruca and Subalpine Warbler S. cantillans by carrying out point counts and habitat measurements at 1861 points at 16 sites in northern Nigeria during the winters of 2001 and 2002. Common Whitethroats were most common at intermediate tree heights and densities of Salvadora persica (with this effect strongest in the pre‐migratory period), and increased as Balanites aegyptiaca density increased initially, although this effect levelled off at higher Balanites densities. Subalpine Warblers were most common at intermediate tree heights and Balanites densities, increased as Acacia and Salvadora density increased, decreased with tree density and were least common at intermediate shrub densities. Lesser Whitethroats were most common at intermediate tree heights, Acacia and Salvadora densities, increased with Balanites density, and decreased with tree density and diversity. The shallow slopes of the significant relationships found between Palearctic warbler species and habitat parameters suggest that the group may be robust to habitat degradation, with densities remaining relatively constant across a wide range of habitat types. Common Whitethroats, in particular, appear to be able to survive in extremely degraded habitats, yet may be vulnerable to the disappearance of Salvadora, the fruit of which may allow pre‐migratory fattening.     

Fluorescence-Activated Cell-Sorting Analysis of Fibronectin Peptides Binding to Trypanosoma cruzi Trypomastigotes1

ABSTRACT. The binding of synthetic peptides modeled from the sequence of the cell attachment site of fibronectin to T. cruzi trypomastigote surface receptors was investigated by fluorescence-activated cell-sorting analysis using fluorescein-labeled peptides. Peptides with the sequence Arg-Gly-Asp-Ser bound to the parasite surface. A low percentage of fresh parasites recently liberated from infected fibroblasts had the capacity to bind the peptide. In contrast, these parasites showed a time-dependent several-fold increase in their ability to bind the Arg-Gly-Asp-Ser-containing peptides during extracellular incubation. From these observations, it appears that the expression of surface receptors on a particular, mature stage of the parasite parallels its ability to adhere to and infect host cells.     

CHEMICAL COMMUNICATION IN INSECT COMMUNITIES: A GUIDE TO INSECT PHEROMONES WITH SPECIAL EMPHASIS ON SOCIAL INSECTS

• 1 Chemical communication plays an important part in the lives of insects, and particularly in lives of those that live in groups or social organizations.
• 2 Chemicals which are used in communication in the general sense are called semiochemicals, and there are a number of subdivisions recognized under this title.
• 3 Pheromones are a category of semiochemicals which are used for communication between individuals of the same species.
• 4 Pheromones are in turn subdivided into primer and releaser pheromones. The former produce a relatively long-lasting physiological change in the receiver, and the latter stimulate the receiver to some immediate behavioural response.
• 5 Far more is known about releaser pheromones at present because they are easier to study.
• 6 Nine categories of releaser pheromone are recognized here, used by both social and non-social insects.
• 7 Sex pheromones are widely used to bring the sexes together for mating, and they have been extensively studied in Lepidoptera.
• 8 Invitation pheromones, encouraging the species to feed or oviposit at an explored site, are not extensively known.
• 9 Aggregation pheromones are designed to bring individuals together into groups which may be temporary in sub-social insects, or permanent in social insects.
• 10 Dispersal or spacing pheromones are used by other species to reduce intraspecific competition for scarce resources.
• 11 Alarm pheromones are a broad and sometimes unclearly defined group which communicate alarm or attack, chiefly in colonial species.
• 12 Trail pheromones, applied to a surface by an individual, to be followed by another, are confined to Hymenoptera, Isoptera and a few Lepidoptera as far as is known.
• 13 Territorial and home range pheromones may be widely distributed, but as yet few of them have been recognized.
• 14 Surface and funeral pheromones are even less well known. Surface pheromones may play a large part in species or colony recognition.
• 15 We can expect the number and complexity of pheromones to be much greater in social insects, a part of the subject which until now has received relatively less attention.
• 16 As our understanding of the subject grows we may expect other categories to be added to this list.

     

Cybrids and tetrad sterility for developing true potato seed hybrids

Potato cybrids result from the fusion between cytoplasm and nuclear gene donors. Such genetic materials are an alternative means to broaden the breeding pool by non‐sexual gene transfer. Tetrad pollen sterility provides also another source of male sterility with some potential for true potato seed breeding. The objective of this research was to investigate cybrid‐derived offspring for both agronomic and reproductive characteristics in two contrasting Peruvian locations, and to examine new exotic germplasm for tetrad sterility, with the aim of broadening the breeding pool available at the Centro Internacional de la Papa (CIP). The cybrids were derived from fusions between Y‐245.7, a clone with tetrad sterility, and Atzimba. These cybrids were crossed with selected male parents from the CIP breeding population, and their hybrid offspring were tested in La Molina (coastal desert) and Huancayo (cool highlands). In addition, other clones with tetrad sterility were also crossed with selected testers to determine their breeding value. There were significant differences for tuber yield, style length, and berry number among the hybrid offspring, and the genotype by environment interaction was significant for tuber yield and berry number. The top 25% highest yielding cybrid‐derived offspring across both locations showed the same tuber yield although they were significantly different for some of the reproductive characteristics. With the exception of one cybrid, the others did not exhibit segregation for tetrad sterility in their hybrid offspring, which were male fertile. However, the offspring derived from crosses between other sources of tetrad sterility and the same testers all showed tetrad sterility, and some of them had outstanding tuber yield at La Molina. The lack of segregation for tetrad sterility in these new crosses suggests that the non‐cybrid, male sterile, female parents are triplex or quadriplex for the Tr nuclear locus, which interacts with a sensitive cytoplasm (e.g. Trs from S. verrucosum or S. stoloniferum) to produce tetrad sterility in potato.     

Growth of potato cultivars in response to application of phosphate fertiliser

Three experiments examined the response of potato cultivars from different maturity groups to fertiliser phosphorus application under conditions of relatively low residual soil P. Initial expansion of the leaf canopy was much more rapid following P application and maximum cover was attained sooner. In the absence of applied P, maximum ground cover was reduced substantially in early-maturing cultivars but not in maincrop cultivars. At early harvests, all cultivars showed very large growth responses to P application, but cv. Rocket grown from well-sprouted seed showed a significantly larger response than cv. Desiree. In the absence of applied P, ground cover was in some cases higher at later growth stages allowing a substantial degree of growth compensation so that final harvests showed only small effects of P application on dry matter yields. At final harvests, no significant interactions between cultivar and phosphorus fertiliser level were found for either dry matter production or P uptake despite some apparent effects. Phosphorus application increased dry matter production through increased interception of solar radiation with no effect on efficiency of utilisation.     

A Frightening Device for Deterring Deer Use of Cattle Feeders

Abstract: The presence of bovine tuberculosis (TB) in cattle can negatively impact a state's economy and cattle industry. In Michigan, USA, wild white-tailed deer (Odocoileus virginianus) are a reservoir for reinfecting cattle herds. Although direct TB transmission between deer and cattle is rare, infected deer may contaminate cattle feed. To mitigate this risk, we designed and evaluated a deer-resistant cattle feeder (DRCF) device for deterring deer from feeders. The device delivered negative stimuli to condition deer to avoid cattle feeders. We tested the device by conducting a comparative change experiment at a high-density captive white-tailed deer operation in northeastern lower Michigan using pretreatment and treatment periods and random allocation of DRCF protection to 3 of 6 feeders during the treatment period. We used animal-activated cameras to collect data on deer use of feeders. Deer use was similar at protected and unprotected feeders during the pretreatment period but was lower at protected feeders during the treatment period. Deer-resistant cattle feeders were 100% effective during the first 2 treatment weeks, 94% during the first 5 weeks, but effectiveness then dropped to 61% during the final week. Excluding problems associated with low battery power and infrared sensors, DRCFs were 99% effective at deterring deer. Our results suggest that DRCFs can effectively limit deer use of cattle feed, potentially with minimal impact on feeding behavior of cattle, thus reducing potential transmission of bovine TB through contaminated feed. By employing DRCFs in bovine TB endemic areas, especially at times that deer are food stressed, agencies and producers can practically and economically reduce the potential for bovine TB to be transmitted from deer to cattle.     

A meta‐analysis of latitudinal variations in life‐history traits of roach,Rutilus rutilus,over its geographical range: linear or non‐linear relationships?

1. We collated information from the literature on life history traits of the roach (a generalist freshwater fish), and analysed variation in absolute fecundity, von Bertalanffy parameters, and reproductive lifespan in relation to latitude, using both linear and non-linear regression models. We hypothesized that because most life history traits are dependent on growth rate, and growth rate is non-linearly related with temperature, it was likely that when analysed over the whole distribution range of roach, variation in key life history traits would show non-linear patterns with latitude.
2. As fecundity depends strongly on length, and the length structure of females varied among populations, latitudinal patterns in fecundity were examined based on residuals from the length–fecundity relationship. The reproductive lifespan of roach was estimated as the difference between age at maturity and maximum age of females in each population.
3. The three life history traits of roach analysed all varied among populations and were non-linearly related to latitude. Only the relationship between reproductive lifespan and latitude was a better fit to a linear that to a quadratic model, although Loess smoothing curves revealed that this relationship was actually closer to biphasic than linear in form. A latitude of 50°N formed a break point in all three life history traits.
4. The negative relationships we have described between (i) fecundity and reproductive lifespan and (ii) fecundity and egg mass suggest that lower fecundity is compensated for by longer lifespan, while lower fecundity is compensated for by an increased egg mass, when analysed independently of location.     

The Torradovirus‐specific RNA2‐ORF1 protein is necessary for plant systemic infection

Tomato apex necrosis virus (ToANV, species Tomato marchitez virus, genus Torradovirus, family Secoviridae) causes a severe tomato disease in Mexico. One distinctive feature of torradoviruses compared with other members of the family Secoviridae is the presence of an additional open reading frame (ORF) in genomic RNA2 (denominated RNA2‐ORF1), located upstream of ORF2. RNA2‐ORF2 encodes a polyprotein that is processed into a putative movement protein and three capsid proteins (CPs). The RNA2‐ORF1 protein has homologues only amongst other torradoviruses and, so far, no function has been associated with it. We used recombinant and mutant ToANV clones to investigate the role of the RNA2‐ORF1 protein in various aspects of the virus infection cycle. The lack of a functional RNA2‐ORF1 resulted in an inability to systemically infect Nicotiana benthamiana and tomato plants, but both positive‐ and negative‐strand RNA1 and RNA2 accumulated locally in agroinfiltrated areas in N. benthamiana plants, indicating that the RNA2‐ORF1 mutants were replication competent. Furthermore, a mutant with a deletion in RNA2‐ORF1 was competent for virion formation and cell‐to‐cell movement in the cells immediately surrounding the initial infection site. However, immunological detection of the ToANV CPs in the agroinfiltrated areas showed that this mutant was not detected in the sieve elements even if the surrounding parenchymatic cells were ToANV positive, suggesting a role for the RNA2‐ORF1 protein in processes occurring prior to phloem uploading, including efficient spread in inoculated leaves.     

Reconciling variability and optimal behaviour using multiple criteria in optimization models

A major objective in behavioural and evolutionary ecology is to understand how animals make decisions in complex environments. Examinations of animal behaviour typically use optimization models to predict the choices animals ought to make. The performance of animals under specific conditions is then compared against the predicted optimal strategy. This optimization approach has come into question because model predictions often do not match animal behaviour exactly. This has led to serious scepticism about the ability of animals to exhibit optimal behaviour in complex environments. We show that conventional approaches that compare observed animal behaviour with single optimal values may bias the way we view real-world variation in animal performance. Considerable insight into the abilities of animals to make optimal decisions can be gained by interpreting why variability in performance exists. We introduce a new theoretical framework, called multi-objective optimization, which allows us to examine decision-making in complex environments and interpret the meaning of variability in animal performance. A multi-objective approach defines the set of efficient choices animals may make in attempting to reach compromises among multiple conflicting demands. In a multi-objective framework, we may see variation in animal choices, but, unlike single-objective optimizations where there is one best solution, this variation may represent a range of adaptive compromises to conflicting objectives. An important feature of this approach is that, within the set of efficient alternatives, no choice can be considered to yield higher fitness, a priori, than any other choice. Thus, variability and optimal behaviour may be entirely consistent. We illustrate our point using selected examples from foraging theory where there is already an optimization program in place.