A revision of the Nasa ranunculifolia group (Nasa ser. Grandiflorae pro parte,Loasaceae)

The monophyletic Nasa ranunculifolia group (Nasa ser. Grandiflorae pro parte) is revised on the basis of extensive field studies and a revision of copious herbarium material. All species of this group are from the high Andes of Peru and Ecuador (mostly 3000–4300 m). The overall degree of morphological divergence is much lower than in other groups of Nasa and many of the various local ‘races’ are best recognized as ecogeographically isolated subspecies. Thus, six species and 13 subspecies are recognized on the basis of differences in leaf and floral morphology, growth habit, life history and distribution. Nasa ranunculifolia, N. macrantha, N. cymbopetala and N. macrorrhiza are united as subspecies under N. ranunculifolia. An additional five subspecies of N. ranunculifolia are newly described (ssp. pamparomasii, ssp. guzmangoensis, ssp. bolivarensis, ssp. patazensis and ssp. huanucoensis). Nasa rugosa is subdivided into four subspecies, three of them new (ssp. llaqtacochaensis, ssp. gracilipes and ssp. pygmaea). Nasa tulipadiaboli sp. nov. and N. basilica sp. nov. are described as new species. Eight taxa (seven subspecies and one species) are endemic to the Amotape–Huancabamba Zone, and seven of them (six subspecies and one species) are new to science. Only a single species ranges into the Amotape–Huancabamba Zone from the south, underscoring the high levels of endemism (and taxonomic novelty) in this area. Illustrations, distribution maps, a key and diagnoses are given for all taxa recognized. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 167 , 47–93.     

The influence of pre-floral growth and development on the pathway of floral development, dry matter distribution and seed yield in oilseed rape (Brassica napus L.)

Patterns of floral development, dry matter distribution and seed yield were examined in winter oilseed rape plants subjected to different pre-floral growth environments. The duration of pre-floral growth and plant size at flower initiation, measured in terms of total mainstem leaf number, were manipulated by varying the temperature between seedling emergence and flower initiation. Exposure of seedlings to low temperatures from cotyledon expansion onwards markedly reduced the duration of pre-floral growth and the number of leaves on the mainstem. The subsequent development pattern of plants was largely dependent on the date of flower initiation and therefore vernalisation requirement. Indeed, the period of growth from flower initiation to maturity, considered on the basis of thermal time, was directly related to the duration of pre-floral growth and mainstem leaf number. The thermal durations of the bud development phase and flowering period in plants exposed to different pre-floral cold treatments but with a common date of flower initiation were similarly linked to these two parameters. Plants exposed to prolonged periods of low temperature treatment from cotyledon expansion onwards initiated fewer mainstem leaves during a relatively short pre-floral growth phase and their yield potential was limited by a reduction in branch and flower numbers. Plants maintained at higher temperatures produced more mainstem leaves during an extended period of pre-floral growth and supported a greater number of branches and flowers. However, this additional yield potential was not realised due to a reduction in seed numbers and mean seed weight. It appeared that seed yield of these plants was limited by increased competition between an excessive number of lower branches and flowers, a problem apparently created by excessive pre-floral growth. Minimal competition for available assimilates between the limited number of branches of plants with a shorter pre-floral growth phase and fewer mainstem leaves, resulted in lower levels of pod abortion, greater seed production and ultimately increased seed yields.     

Birth seasonality and offspring production in threatened neotropical primates related to climate

Given the threatened status of many primate species, the impacts of global warming on primate reproduction and, consequently, population growth should be of concern. We examined relations between climatic variability and birth seasonality, offspring production, and infant sex ratios in two ateline primates, northern muriquis, and woolly monkeys. In both species, the annual birth season was delayed by dry conditions and El Niño years, and delayed birth seasons were linked to lower birth rates. Additionally, increased mean annual temperatures were associated with lower birth rates for northern muriquis. Offspring sex ratios varied with climatic conditions in both species, but in different ways: directly in woolly monkeys and indirectly in northern muriquis. Woolly monkeys displayed an increase in the proportion of males among offspring in association with El Niño events, whereas in northern muriquis, increases in the proportion of males among offspring were associated with delayed onset of the birth season, which itself was related, although weakly, to warm, dry conditions. These results illustrate that global warming, increased drought frequency, and changes in the frequency of El Niño events could limit primate reproductive output, threatening the persistence and recovery of ateline primate populations.     

Observations and modeling of aboveground tree carbon stocks and fluxes following a bark beetle outbreak in the western United States

Bark beetle epidemics result in tree mortality across millions of hectares in North America. However, few studies have quantified impacts on carbon (C) cycling. In this study, we quantified the immediate response and subsequent trajectories of stand‐level aboveground tree C stocks and fluxes using field measurements and modeling for a location in central Idaho, USA that experienced an outbreak of mountain pine beetle (Dendroctonus ponderosae Hopkins). We measured tree characteristics in lodgepole pine (Pinus contorta) plots spanning a range of structure and mortality conditions. We then initialized the forest vegetation simulator, an individual tree‐based model, with these measurements and simulated the response of aboveground production of C fluxes as well as trajectories of C stocks and fluxes in the coming decades. Mountain pine beetles killed up to 52% of the trees within plots, with more larger trees killed. C stocks in lodgepole pine were reduced by 31–83% following the outbreak, and plot‐level C fluxes decreased 28–73%. Modeled C stocks increased nearly continuously following the infestation, recovering to preoutbreak levels in 25 years or less. Simulated aboveground tree C fluxes increased following the immediate postoutbreak decrease, then subsequently declined. Substantial variability of C stocks and fluxes among plots resulted from the number and size of killed and surviving trees. Our study illustrates that bark beetle epidemics alter forest C cycling unlike stand‐replacement wildfires or clear‐cut harvests, due in part to incomplete mortality coupled with the preference by beetles for larger trees. The dependency of postoutbreak C stocks and fluxes on stand structure suggests that C budget models and studies in areas experiencing mountain pine beetle disturbances need to include size distribution of trees for the most accurate results.     

Dispersal and upstream migration of an amphidromous neritid snail: implications for restoring migratory pathways in tropical streams

1. The amphidromous life cycle of several species of neritid snails, shrimp and gobies throughout the tropics includes juveniles that migrate from the ocean to breed in fresh water. In many Hawaiian streams, the decline of Neritina granosa, an endemic gastropod, has been associated with habitat degradation and water withdrawal, which are common factors affecting tropical rivers around the world. 2. We investigated the effects of water withdrawal and density on dispersal and upstream migration of N. granosa using three experimental treatments: (i) reduced flow (RF) owing to a stream diversion, (ii) natural flow (NF) and (iii) natural flow with artificially increased snail density. For each treatment, snails were differentially tagged and released in a stream without a natural, extant population of N. granosa. 3. Capture rates ranged from 17 to 65% over a 63‐day period following release. Captures on 2–6 days after release measured initial dispersal and migration, whereas longer‐term migration rates were calculated from snails captured 16–63 days after release. Snails under NF displayed positive rheotactic behaviour, with only 3–12% demonstrating initial downstream movement. Under RF, 22–77% of snails moved downstream or showed no bias either way. 4. Initial mean upstream migration rate (UMR) was 0.25, 0.66 and 1.16 m day^?1 under RF, NF and natural flow with increased snail density, respectively. Longer‐term migration rates did not differ significantly between treatments, and the overall mean was 0.62 m day^?1. 5. Principal component analysis and generalised linear models were used to identify habitat characteristics important to UMR, with habitat and reach‐scale hydraulics as the most important factors. The relationship between discharge and UMR suggested it would take 11–35 years for snails to migrate past the most upstream water diversion. However, rates from published studies of neritid snail species migrating en masse or in long lines under natural situations suggested that N. granosa could migrate above stream diversions within 72 days–2.5 years (when in an aggregation) and 29 days–1.1 years (when following in long lines of individuals). 6. An understanding of upstream neritid snail migration can be used for the management and conservation of this and other migratory species in tropical streams.     

Effects of burial on leaf litter quality,microbial conditioning and palatability to three shredder taxa

Summary 1. Heterotrophic microorganisms are crucial for mineralising leaf litter and rendering it more palatable to leaf‐shredding invertebrates. A substantial part of leaf litter entering running waters may be buried in the streambed and thus be exposed to the constraining conditions prevailing in the hyporheic zone. The fate of this buried organic matter and particularly the role of microbial conditioning in this habitat remain largely unexplored. 2. The aim of this study was to determine how the location of leaf litter within the streambed (i.e. at the surface or buried), as well as the leaf litter burial history, may affect the leaf‐associated aquatic hyphomycete communities and therefore leaf consumption by invertebrate detritivores. We tested the hypotheses that (i) burial of leaf litter would result in lower decomposition rates associated with changes in microbial assemblages compared with leaf litter at the surface and (ii) altered microbial conditioning of buried leaf litter would lead to decreased quality and palatability to their consumers, translating into lower growth rates of detritivores. 3. These hypotheses were tested experimentally in a second‐order stream where leaf‐associated microbial communities, as well as leaf litter decomposition rates, elemental composition and toughness, were compared across controlled treatments differing by their location within the streambed. We examined the effects of the diverse conditioning treatments on decaying leaf palatability to consumers through feeding trials on three shredder taxa including a freshwater amphipod, of which we also determined the growth rate. 4. Microbial leaf litter decomposition, fungal biomass and sporulation rates were reduced when leaf litter was buried in the hyporheic zone. While the total species richness of fungal assemblages was similar among treatments, the composition of fungal assemblages was affected by leaf litter burial in sediment. 5. Leaf litter burial markedly affected the food quality (especially P content) of leaf material, probably due to the changes in microbial conditioning. Leaf litter palatability to shredders was highest for leaves exposed at the sediment surface and tended to be negatively related to leaf litter toughness and C/P ratio. In addition, burial of leaf litter led to lower amphipod growth rates, which were positively correlated with leaf litter P content. 6. These results emphasise the importance of leaf colonisation by aquatic fungi in the hyporheic zone of headwater streams, where fungal conditioning of leaf litter appears particularly critical for nutrient and energy transfer to higher trophic levels.     

Diazacon Inhibits Reproduction in Invasive Monk Parakeet Populations

Abstract: Throughout the United States, managers lack safe, effective methods to control expanding populations of the invasive monk parakeet (Myiopsitta monachus). Because the reproductive inhibitor diazacon (20,25 diazacholesterol) has been used effectively in captive monk parakeets, we provided diazacon-treated sunflower seeds to birds at electric utility substations inhabited by parakeets in south Florida, USA. Nest productivity (nestlings plus eggs with embryos) averaged 1.31 (SE = 0.45, n = 100 nests) at 6 treated sites compared to 4.15 (SE = 0.68, n = 50 nests) at 4 untreated sites, a 68.4% reduction. Exposure of native bird species to treated bait was infrequent. Diazacon is an effective means to reduce reproductive success of monk parakeets, and development of methods to limit exposure of nontarget birds will enable more widespread use of this useful population management technique.     

Spatial Partitioning of Predation Risk in a Multiple Predator-Multiple Prey System

ABSTRACT Minimizing risk of predation from multiple predators can be difficult, particularly when the risk effects of one predator species may influence vulnerability to a second predator species. We decomposed spatial risk of predation in a 2-predator, 2-prey system into relative risk of encounter and, given an encounter, conditional relative risk of being killed. Then, we generated spatially explicit functions of total risk of predation for each prey species (elk [Cervus elaphus] and mule deer [Odocoileus hemionus]) by combining risks of encounter and kill. For both mule deer and elk, topographic and vegetation type effects, along with resource selection by their primary predator (cougars [Puma concolor] and wolves [Canis lupus], respectively), strongly influenced risk of encounter. Following an encounter, topographic and vegetation type effects altered the risk of predation for both ungulates. For mule deer, risk of direct predation was largely a function of cougar resource selection. However, for elk, risk of direct predation was not only a function of wolf occurrence, but also of habitat attributes that increased elk vulnerability to predation following an encounter. Our analysis of stage-based (i.e., encounter and kill) predation indicates that the risk effect of elk shifting to structurally complex habitat may ameliorate risk of direct predation by wolves but exacerbate risk of direct predation by cougars. Information on spatiotemporal patterns of predation will be become increasingly important as state agencies in the western United States face pressure to integrate predator and prey management.