Drugs and parasites: global experiments in life history evolution?

Recent work has shown that the evolution of Drosophila melanogaster resistance to attack by the parasitoid Asobara tabida is constrained by a trade-off with larval competitive ability. However, there are two very important questions that need to be answered. First, is this a general cost, or is it parasitoid specific? Second, does a selected increase in immune response against one parasitoid species result in a correlated change in resistance to other parasitoid species? The answers to both questions will influence the coevolutionary dynamics of these species, and also may have a previously unconsidered, yet important, influence on community structure.     

Diversity in the Monogenea and Digenea: does lifestyle matter?

If the cestodes are excluded, then the parasitic platyhelminths of fishes divide neatly into the external and monoxenous Monogenea and the internal and heteroxenous Digenea. Both groups have apparently had long associations of coevolution, host switching and adaptation with fishes and have become highly successful in their respective habitats. Current estimates of species richness for the two groups suggest that they may be remarkably similar. Here we consider the nature of the diversity of the Monogenea and Digenea of fishes in terms of richness of species and higher taxa to determine what processes may be responsible for observed differences. The Monogenea includes at least two super-genera (Dactylogyrus and Gyrodactylus) each of which has hundreds of species; no comparable genera are found in the Digenea. Possible reasons for this difference include the higher host specificity of monogeneans and their shorter generation time. If allowance is made for the vagaries of taxonomic 'lumping' and 'splitting', then there are probably comparable numbers of families of monogeneans and digeneans in fishes. However, the nature of the families differ profoundly. Richness in higher taxa (families) in the Digenea is explicable in terms of processes that appear to have been unimportant in the Monogenea. Readily identifiable sources of diversity in the Digenea are: recolonisation of fishes by taxa that arose in association with tetrapods; adoption of new sites within hosts; adoption of new diets and feeding mechanisms; adaptations relating to the exploitation of ecologically similar groups of fishes and second intermediate hosts; and adaptations relating to the exploitation of phylogenetic lineages of molluscs. In contrast, most higher- level monogenean diversity (other than that associated with the subclasses) relates principally to morphological specialisation for attachment by the haptor.     

Parasitism and survival in a damselfly: does host sex matter?

We present experimental data on the survivorship of damselflies infested by parasitic water mites from a population in field cages. In addition, we show correlative laboratory data under simulated severe weather conditions. In the manipulative experiment, parasitized females' individual condition, which was measured as weight at emergence, was an important determinant of survival under field conditions. In contrast, such a relationship did not occur in males and unparasitized females. It was found in the laboratory experiment that water mites as well as weight at emergence both contributed significantly to the reduced survivorship of male and female damselflies. It was concluded that the impact of parasitism depends on environmental conditions and that host sexes differ in their responses to parasitism. This is discussed in the light of immunocompetence in invertebrates.     

Temperature,rainfall and butterfly morphology: does life history theory match the observed pattern?

Butterfly distribution and abundance is known to be influenced by temperature and rainfall. What is not clear, however, is how life history and flight morphological traits are affected by changes in local weather conditions. During the period 1989–1999, we explored the effects of ambient temperature and rainfall during larval development on adult phenotypic traits (body mass, forewing loading, forewing surface area and forewing length) in a Swedish population of the speckled wood butterfly Pararge aegeria. As different seasonal cohorts correspond to different developmental pathways (larval hibernating, pupal hibernating and directly developing), we analysed these morphological time series relative to developmental pathway. Phenotypic variation in response to the temperature and rainfall levels experienced during larval development differed in both magnitude and direction depending on the developmental pathway, and hence seasonal cohort, examined (i.e. there was a pathway‐specific response). We suggest that through its developmental flexibility P. aegeria may be able to adjust to variation in weather conditions over time. Other less flexible species, however, may not be so fortunately buffered. To truly estimate the impact of climate change on biodiversity more fine‐scale, local studies are required that examine the mechanisms underlying the response of species to climate change.     

Adaptive strategies and life history characteristics in a warming climate: Salmon in the Arctic?

In the warming Arctic, aquatic habitats are in flux and salmon are exploring their options. Adult Pacific salmon, including sockeye (Oncorhynchus nerka), coho (O. kisutch), Chinook (O. tshawytscha), pink (O. gorbuscha) and chum (O. keta) have been captured throughout the Arctic. Pink and chum salmon are the most common species found in the Arctic today. These species are less dependent on freshwater habitats as juveniles and grow quickly in marine habitats. Putative spawning populations are rare in the North American Arctic and limited to pink salmon in drainages north of Point Hope, Alaska, chum salmon spawning rivers draining to the northwestern Beaufort Sea, and small populations of chum and pink salmon in Canada’s Mackenzie River. Pacific salmon have colonized several large river basins draining to the Kara, Laptev and East Siberian seas in the Russian Arctic. These populations probably developed from hatchery supplementation efforts in the 1960’s. Hundreds of populations of Arctic Atlantic salmon (Salmo salar) are found in Russia, Norway and Finland. Atlantic salmon have extended their range eastward as far as the Kara Sea in central Russian. A small native population of Atlantic salmon is found in Canada’s Ungava Bay. The northern tip of Quebec seems to be an Atlantic salmon migration barrier for other North American stocks. Compatibility between life history requirements and ecological conditions are prerequisite for salmon colonizing Arctic habitats. Broad-scale predictive models of climate change in the Arctic give little information about feedback processes contributing to local conditions, especially in freshwater systems. This paper reviews the recent history of salmon in the Arctic and explores various patterns of climate change that may influence range expansions and future sustainability of salmon in Arctic habitats. A summary of the research needs that will allow informed expectation of further Arctic colonization by salmon is given.     

Labs in the Field? Rocky Mountain Biological Stations in the Early Twentieth Century

Biological field stations proliferated in the Rocky Mountains region of the western United States during the early decades of the twentieth century. This essay examines these Rocky Mountain field stations as hybrid lab-field sites from the perspective of the field side of the dichotomy: as field sites with raised walls rather than as laboratories whose walls with the natural world have been lowered. Not only were these field stations transformed to be more like laboratories, but they were also embedded within the particular regional environmental and institutional context of the Rocky Mountains. Using the University of Colorado's Mountain Laboratory at Tolland and other contemporaneous sites as examples, this essay analyzes key features of these sites, including their location within transportation networks, buildings, equipment, personnel, scheduling, recreational and social activities, and other material and social practices on the ground. Considering both the distinctive and shared characteristics of the Rocky Mountain field stations in comparison to other types of field stations provides a more complete picture of the diversity and range of lab-field hybrid sites in the biological sciences in the early twentieth-century United States.     

Seed positioning in extruded pellets: does it matter?

Extruded pellets containing activated carbon (AC) can be used to sow native seeds while simultaneously applying herbicide to control invasive species. Incorporating AC in pellets has been demonstrated to protect native seeds; however, there may be unintended detrimental impacts to seedling emergence. We aimed to optimize seed position within pellets to maximize emergence and survival of the perennial shrub Jacksonia furcellata. Seeds were positioned at 2 mm (top), 6 mm (middle), and 12 mm (bottom) within pellets (with or without AC), sown on or below the soil surface, and compared to non-pelleted seeds sown under the soil surface in the equivalent positions (2, 6, and 12 mm depth). Trays were treated with a pre-emergent herbicide (Simazine) or left unsprayed. Emergence (without herbicide) was significantly higher from seeds positioned at the bottom of pellets without AC sown on the soil surface (70%), compared to non-pelleted seeds sown at the bottom (12 mm below the soil surface; 57%). However, emergence was inhibited when seeds were positioned in the middle (6 mm) of pellets with AC (32%). When treated with Simazine, survival was highest from seeds positioned at the bottom of pellets with AC (60%), compared to pellets without AC (15%) and non-pelleted seeds sown at the bottom (12 mm below the soil surface; 15%). Jacksonia furcellata seeds positioned at the bottom of pellets, sown on the soil surface, shows promise to minimize negative impacts to emergence, and maximize herbicide protection. Further testing with additional species is required to refine pellet production (e.g. recipe, extrusion, and shape) for optimal emergence.     

Drug resistance in Leishmania: does it really matter?

Treatment failure (TF) jeopardizes the management of parasitic diseases, including leishmaniasis. From the parasite’s point of view, drug resistance (DR) is generally considered as central to TF. However, the link between TF and DR, as measured by in vitro drug susceptibility assays, is unclear, some studies revealing an association between treatment outcome and drug susceptibility, others not. Here we address three fundamental questions aiming to shed light on these ambiguities. First, are the right assays being used to measure DR? Second, are the parasites studied, which are generally those that adapt to in vitro culture, actually appropriate? Finally, are other parasite factors – such as the development of quiescent forms that are recalcitrant to drugs – responsible for TF without DR?     

Insect declines and agroecosystems: does light pollution matter?

Drastic declines in insect populations, ‘Ecological Armageddon’, have recently gained increased attention in the scientific community, and are commonly considered to be the consequence of large‐scale factors such as land‐use changes, use of pesticides, climate change and habitat fragmentation. Artificial light at night (ALAN), a pervasive global change that strongly impacts insects, remains, however, infrequently recognised as a potential contributor to the observed declines. Here, we provide a summary of recent evidence of impacts of ALAN on insects and discuss how these impacts can drive declines in insect populations in light‐polluted areas. ALAN can increase overall environmental pressure on insect populations, and this is particularly important in agroecosystems where insect communities provide important ecosystem services (such as natural pest control, pollination, conservation of soil structure and fertility and nutrient cycling), and are already under considerable environmental pressure. We discuss how changes in insect populations driven by ALAN and ALAN itself may hinder these services to influence crop production and biodiversity in agricultural landscapes. Understanding the contribution of ALAN and other factors to the decline of insects is an important step towards mitigation and the recovery of the insect fauna in our landscapes. In future studies, the role of increased nocturnal illumination also needs to be examined as a possible causal factor of insect declines in the ongoing ‘Ecological Armageddon’, along with the more commonly examined factors. Given the large scale of agricultural land use and the potential of ALAN to indirectly and directly impact crop production and biodiversity, a better understanding of effects of ALAN in agroecosystems is urgently needed.     

Impact factor in cytopathology journals: what does it reflect and how much does it matter?

B. AbdullGaffar
Impact factor in cytopathology journals: what does it reflect and how much does it matter? Objective: To study the trends of impact factor (IF) in four cytopathology journals. To investigate the factors that might influence IF in cytopathology literature and whether IF has any impact on cytopathology practice. Methods: The IFs of four cytopathology journals were searched from 2005 to 2009. The IFs and their relationships with the types and number of publications, publishers, the official societies, readership, the quality of their contents, the topics covered and the levels of evidence were compared. Results: Cancer Cytopathology (CC) had the highest IF. Acta Cytologica (AC) had the lowest IF, which appeared to be in decline. Cytopathology (C) and Diagnostic Cytopathology (DC) had a slow but steady increase in their IF. Components that might influence these differences could include the category and the society of the journal, targeted readers and certain types of publications. Publishers, the number of publications, the types of topics covered and the levels of evidence probably have no major effect on IF. Conclusions: IF has its own benefits and original applications. IF is a quantitative measure that does not reflect the levels of evidence in cytopathology journals. IF should not be abandoned because it might encourage competition between cytopathology journals, but it should not dictate their contents.     

Preference for children and subsequent fertility in Matlab: does wife-husband agreement matter?

This study examines wife-husband preference for children and subsequent fertility for a period of 5 years in the treatment and comparison areas of Matlab, Bangladesh. The two data sets used were: the In-depth Survey (1984) and the Demographic Surveillance System (1984-89). In the case of wives' preferences for children, subsequent childbearing was 13.8% higher than desired in the treatment area and 44.7% higher than desired in the comparison area. After controlling for all variables in the model, the likelihood of giving birth was 1.78 times higher for wives who wanted no more children, but whose husbands did want more, compared with couples where neither husband nor wife wanted more children. For couples where the wife wanted more, but the husband did not want more children, the likelihood of giving birth was 0.63 times that of couples where both the husband and wife wanted more children. This finding suggests that to enhance the decline in fertility in these two areas of Matlab, it will be necessary to motivate both wives and husbands to cease childbearing.     

Sex allocation and nestling survival in a dimorphic raptor: does size matter?

Fisher's theory predicts equal sex ratios at the end of parentalcare if the costs and benefits associated with raising eachsex of offspring are equal. In raptors, which display variousdegrees of reversed sexual size dimorphism (RSD; females thelarger sex), sex ratios biased in favor of smaller males areonly infrequently reported. This suggests that offspring ofeach sex may confer different fitness advantages to parents.We examined the relative returns associated with raising eachsex of offspring of the brown falcon Falco berigora, a medium-sizedfalcon exhibiting RSD (males approximately 75% of female bodymass) and subsequent sex ratios. Female nestlings hatched eitherfirst or second did not receive more food nor did they hatchfrom larger eggs or remain dependent on parents for longer periodsthan male offspring from these hatch orders. Together with previousstudies this result indicates that even in markedly dimorphicspecies, the required investment to raise the larger sex islikely to be less than that predicted by body size differencesalone. Moreover, among last-hatched nestlings, both sexes faceda reduced food allocation and suffered a slower growth rateand thus final body size, with a concurrent increased probabilityof mortality. For last-hatched females the reduction in foodallocation was more marked, with complete mortality of all last-hatchedfemale nestlings monitored in this study. Once independent,males of any size but only larger females are likely to be recruitedinto the breeding population. The sex-biased food allocationamong last-hatched offspring favoring males thus reflects therelative returns to parents in raising a small member of eachsex.     

Nitrogen cycling in a northern hardwood forest: Do species matter?

To investigate the influence of individual tree species on nitrogen (N) cycling in forests, we measured key characteristics of the N cycle in small single-species plots of five dominant tree species in the Catskill Mountains of New York State. The species studied were sugar maple (Acer saccharum), American beech (Fagus grandifolia), yellow birch (Betula alleghaniensis), eastern hemlock (Tsuga canadensis), and red oak (Quercus rubra). The five species varied markedly in N cycling characteristics. For example, hemlock plots consistently showed characteristics associated with "slow" N cycling, including low foliar and litter N, high soil C:N, low extractable N pools, low rates of potential net N mineralization and nitrification and low NO ₃ ^– amounts trapped in ion-exchange resin bags buried in the mineral soil. Sugar maple plots had the lowest soil C:N, and the highest levels of soil characteristics associated with NO ₃ ^– production and loss (nitrification, extractable NO ₃ ^– , and resin bag NO ₃ ^– ). In contrast, red oak plots had near-average net mineralization rates and soil C:N ratios, but very low values of the variables associated with NO ₃ ^– production and loss. Correlations between soil N transformations and litter concentrations of N, lignin, lignin:N ratio, or phenolic constituents were generally weak. The inverse correlation between net nitrification rate and soil C:N that has been reported in the literature was present in this data set only if red oak plots were excluded from the analysis. This study indicates that tree species can exert a strong control on N cycling in forest ecosystems that appears to be mediated through the quality of soil organic matter, but that standard measures of litter quality cannot explain the mechanism of control.     

Resilience and regime change in a southern Rocky Mountain ecosystem during the past 17?000 years

Paleoecological records indicate that subalpine forests in western North America have been resilient in response to multiple influences, including severe droughts, insect outbreaks, and widely varying fire regimes, over many millennia. One hypothesis for explaining this ecosystem resilience centers on the disruption of forest dynamics by frequent disturbance and climatic variability, and the resulting development of non-steady-state regimes dominated by early-successional conifers with broad climatic tolerances, such as lodgepole pine (Pinus contorta var. latifolia Engelm. ex Wats.). To evaluate this hypothesis, we independently reconstructed the vegetation, fire, and effective-moisture histories of a small, forested watershed at 2890 m elevation in southeastern Wyoming, USA, using sedimentary pollen and charcoal counts in conjunction with sedimentary lake-level indicators. The data indicate that prominent vegetation shifts (from sagebrush steppe to spruce–fir parkland at ca. 10.7 ka and spruce–fir parkland to pine-dominated forest at ca. 8.5 ka [ka stands for thousands of years before the present, defined as AD 1950]) coincided with changes in effective moisture. However, after lodgepole pine forests established at ca. 8.5 ka, similar hydroclimatic changes did not produce detectable vegetation responses. Fire history data show that other aspects of the ecosystem were responsive to changes in effective moisture at centennial timescales with prolonged fire-free episodes coinciding with periods of low effective moisture ca. 7.2–5.6 and 3.7–1.6 ka. Throughout our record, the ratio of ecosystem perturbation time (i.e., fire frequency and changes in effective moisture) to recovery time (assuming 200–600-year successional processes) falls within estimates of the ratio for non-steady state ecosystems. Frequent perturbations, therefore, may have prevented this ecosystem from reaching compositional equilibrium with the varied climatic conditions over the past 8.5 ka. Equilibrium states could have included more abundant spruce (Picea spp.) and fir (Abies spp.) than presently observed based on brief increases in pollen abundances of these taxa during prolonged dry, fire-free intervals. Our results show that, although current climate changes favor widespread disturbance in Rocky Mountain forests, the composition of these ecosystems could be highly resilient and recover through successional dynamics over the next few decades to centuries.