A major genome region underlying artemisinin resistance in malaria

Evolving resistance to artemisinin-based compounds threatens to derail attempts to control malaria. Resistance has been confirmed in western Cambodia and has recently emerged in western Thailand, but is absent from neighboring Laos. Artemisinin resistance results in reduced parasite clearance rates (CRs) after treatment. We used a two-phase strategy to identify genome region(s) underlying this ongoing selective event. Geographical differentiation and haplotype structure at 6969 polymorphic single-nucleotide polymorphisms (SNPs) in 91 parasites from Cambodia, Thailand, and Laos identified 33 genome regions under strong selection. We screened SNPs and microsatellites within these regions in 715 parasites from Thailand, identifying a selective sweep on chromosome 13 that shows strong association (P = 10(-6) to 10(-12)) with slow CRs, illustrating the efficacy of targeted association for identifying the genetic basis of adaptive traits.     

Soil fauna alter the effects of litter composition on nitrogen cycling in a mineral soil

Plant chemical composition and the soil community are known to influence litter and soil organic matter decomposition. Although these two factors are likely to interact, their mechanisms and outcomes of interaction are not well understood. Studies of their interactive effects are rare and usually focus on carbon dynamics of litter, while nutrient dynamics in the underlying soil have been ignored. A potential mechanism of interaction stems from the role fauna plays in regulating availability of litter-derived materials in the mineral soil. We investigated the role of soil fauna (meso, macro) in determining the effect of surface-litter chemical composition on nitrogen mineralization and on the micro-food web in mineral soils. In a field setting we exposed mineral soil to six types of surface-applied litter spanning wide ranges of multiple quality parameters and restricted the access of larger soil animals to the soils underlying these litters. Over six months we assessed litter mass and nitrogen loss, nitrogen mineralization rates in the mineral soils, and soil microbes and microfauna. We found evidence that the structure of the soil community can alter the effect of surface-litter chemical composition on nitrogen dynamics in the mineral soil. In particular, we found that the presence of members of the meso- and macrofauna can magnify the control of nitrogen mineralization by litter quality and that this effect is time dependent. While fauna were able to affect the size of the micro-food web they did not impact the effect of litter composition on the abundance of the members of the micro-food web. By enhancing the strength of the impact of litter quality on nitrogen dynamics, the larger fauna can alter nitrogen availability and its temporal dynamics which, in turn, can have important implications for ecosystem productivity. These findings contribute to evidence demonstrating that soil fauna shape plant litter effects on ecosystem function.     

Legacies of plant litter on carbon and nitrogen dynamics and the role of the soil community

There is increasing awareness of the importance of ecological legacies in contemporary ecosystem processes. Decomposition is regulated by a set of interacting hierarchically organized factors. As spatial and temporal scales decrease, decomposition is largely dependent on the quality of resources and the decomposer community, but whether and how these factors manifest via historical legacy effects is not well understood. We tested whether the history of plant litter inputs had short-term legacy effects on contemporary litter and soil organic matter carbon (C) and nitrogen (N) mineralization. Using a field/laboratory microcosm approach, we exposed soils to two litters of contrasting chemistry and, after adding fresh substrates, we monitored C and N dynamics. In a parallel experiment, we manipulated the soil community to reduce litter-history impacts on its composition and size to investigate whether the soil community could be an important contributor to legacy effects We found strong short-term litter legacy effects on contemporary litter and soil N mineralization, the duration of which was dependent on the contemporary substrate for decomposition. These strong effects were not consistent with the home field advantage phenomenon, as exposure to a specific litter did not favor the decomposition of the same litter when it was applied as a contemporary substrate. Reduction of the litter-history effects on soil biota decreased the impact of litter history on N immobilization, suggesting that plant litter impacts on the soil community may be an important component of plant litter legacies on N decomposition. In contrast to N, litter legacies appeared to be much less important for C decomposition, suggesting that legacy effects might uncouple contemporary C and N dynamics.     

Trade‐offs in triple‐bottom‐line outcomes when recovering fisheries

Almost all environmental management comes at an economic cost that may not be borne equitably by all stakeholders. Here, we investigate how heterogeneity in catch and profits among fishers influences the trade‐off among the triple‐bottom‐line objectives of recovering a fish population, maximizing its economic value and distributing restrictions equitably across fishers. As a case‐study, we examine management reform of an ecologically and economically important coral reef fishery operating within the Great Barrier Reef Marine Park. Using a simulation model, we find that total profitability of the fishing industry is 40% lower if recovery plans are equitable when compared to the most economically efficient plan. However, efficient recovery plans were typically highly inequitable because they required some fishers to cease fishing. Equity was defined according to different norms, and the efficiency loss was greatest when catch losses were shared equally across fishers rather than in proportion to their historical catch. We then varied key social, economic and biological parameters to identify cases when equity and efficient recovery would trade‐off most strongly. Recovery plans could be both efficient and equitable when heterogeneity in fisher's catches and individual catch efficiencies was lower. If fishers were homogenous then equitable plans could have maximal economic efficiency. These results emphasize the importance of considering heterogeneity in individual fishers when designing recovery plans. Recovery plans that are inequitable may often fail to gain stakeholder support, so in fisheries with high heterogeneity we should temper our expectations for marked increases in profits.     

Larval rearing and development of Siganus lineatus (Pisces: Siganidae) from hatching through metamorphosis

Larvae of Siganus lineatus were hatched and reared through metamorphosis in a 7 000-1 tank covered with a translucent roof. The larvae were fed phytoplankton (mixed cultures), rotifers (Brachionus plicatilis), copepods (Oithona sp.), and Artemia nauplii. Thirty-five days were required for all the larvae to metamorphose; survival was 800 out of 5 000 (16%). The rearing period and rearing criteria are identical to those required for S. canaliculatus. Three important developmental stages were identified: the dark-head carnivorous stage (the gut is a simple coil), the brown-head omnivorous stage (the gut is elongated and convoluted), and the juvenile herbivorous stage (the gut is highly elongated and convoluted into a complex coil). Over-feeding on Artemia nauplii may result in deaths among brown-head and juvenile fishes; adjustment of the feeding regime when larvae begin to develop into the brown-head stage is considered important. Copepods are an excellent substitute for Artemia nauplii during this period     

Multiple Avenues to Gender in Strawberries

ABSTRACT

Common strawberry cultivars are hermaphrodites, producing both anthers and pistils in their flowers. However, octoploid Fragaria species are trioecious and different genotypes can be female with pistillate flowers, hermaphrodites, or males with staminate flowers. One female selection, F. virginiana High Falls 22 and three hermaphrodite selections, N8688, RH23, and Montreal River 10 were hybridized with five June-bearing cultivars. Seedlings of each family were planted in Ontario and Michigan. Two F. chiloensis selections Pigeon Point (female) and FRA1267 (hermaphrodite), were hybridized with 14 F. virginiana selections. Seedlings from each family were planted in Ontario and Minnesota. In all progeny, the presence or absence of anthers was recorded and a subjective scale used to estimate the percentage of fruit set (1–10 representing 10% intervals). Also, FRA1267 was crossed with one F. × ananassa selection and the progeny intercrossed and grown in Ontario. In the sib-crosses gender was recorded. In two female parents, the female progeny had on average a higher fruit set than the hermaphrodite progeny. F. virginiana genotypes varied in their fruit set, which suggested that there are a number of alleles involved in the fertility of hermaphrodites. In crosses, FRA1267 produced 80% females when used as a female parent and 100% hermaphrodites when used as a male parent. It is thought that the trait is inherited cytoplasmically or that the F. chiloensis alleles involved are epistatic when F. virginiana or F. × ananassa is used as a male parent.