Are behavioural responses to predation cues linked across life cycle stages?

1. Prey organisms can perceive cues to predation hazard and adopt low‐risk behaviours to increase survival. Animals with complex life cycles, such as insects, can exhibit such anti‐predatory behaviours in multiple life stages. 2. Cues to predation risk may induce ovipositing females to choose habitats with low predation risk. Cues to predation risk may also induce larvae to adopt facultative behaviours that reduce risk of predation. 3. One hypothesis postulates that anti‐predation behaviours across adult and larval stages may be negatively associated because selection for effective anti‐predator behaviour in one stage leads to reduced selection for avoidance of predators in other stages. An alternative hypothesis suggests that selection by predation favours multi‐component defences, with both avoidance of oviposition and facultative adoption of low‐risk behaviours by larvae. 4. Laboratory and field experiments were used to determine whether defensive responses of adult and larval mosquitoes are positively or negatively associated. The study tested effects of waterborne cues from predatory Toxorhynchites theobaldi on oviposition choices and larval behaviours of three of its common prey: Culex mollis, Limatus durhamii and Aedes albopictus. 5. Culex mollis shows strong anti‐predator responses in both life stages, consistent with the hypothesis of a multi‐component behavioural defence. The other two species showed no detectable responses to waterborne predator cues in either adult or larval stages. Larvae of these unresponsive species were significantly more vulnerable to this predator than was C. mollis. 6. For these mosquitoes, species appear either to have been selected for multi‐component defences against predation or to act in ways that could be called predator‐naïve.     

Sudden expansion of a single brown bear maternal lineage across northern continental Eurasia after the last ice age: a general demographic model for mammals?

The brown bear has proved a useful model for studying Late Quaternary mammalian phylogeography. However, information is lacking from northern continental Eurasia, which constitutes a large part of the species' current distribution. We analysed mitochondrial DNA sequences (totalling 1943 bp) from 205 bears from northeast Europe and Russia in order to characterize the maternal phylogeography of bears in this region. We also estimated the formation times of the sampled brown bear lineages and those of its extinct relative, the cave bear.
Four closely related haplogroups belonging to a single mitochondrial subclade were identified in northern continental Eurasia. Several haplotypes were found throughout the whole study area, while one haplogroup was restricted to Kamchatka. The haplotype network, estimated divergence times and various statistical tests indicated that bears in northern continental Eurasia recently underwent a sudden expansion, preceded by a severe bottleneck. This brown bear population was therefore most likely founded by a small number of bears that were restricted to a single refuge area during the last glacial maximum. This pattern has been described previously for other mammal species and as such may represent one general model for the phylogeography of Eurasian mammals. Bayesian divergence time estimates are presented for different brown and cave bear clades. Moreover, our results demonstrate the extent of substitution rate variation occurring throughout the phylogenetic tree, highlighting the need for appropriate calibration when estimating divergence times.     

Acclimation of isoprene emission and photosynthesis to growth temperature in hybrid aspen: resolving structural and physiological controls

Acclimation of foliage to growth temperature involves both structural and physiological modifications, but the relative importance of these two mechanisms of acclimation is poorly known, especially for isoprene emission responses. We grew hybrid aspen (Populus tremula x P. tremuloides) under control (day/night temperature of 25/20 °C) and high temperature conditions (35/27 °C) to gain insight into the structural and physiological acclimation controls. Growth at high temperature resulted in larger and thinner leaves with smaller and more densely packed chloroplasts and with lower leaf dry mass per area (M_A). High growth temperature also led to lower photosynthetic and respiration rates, isoprene emission rate and leaf pigment content and isoprene substrate dimethylallyl diphosphate pool size per unit area, but to greater stomatal conductance. However, all physiological characteristics were similar when expressed per unit dry mass, indicating that the area‐based differences were primarily driven by M_A. Acclimation to high temperature further increased heat stability of photosynthesis and increased activation energies for isoprene emission and isoprene synthase rate constant. This study demonstrates that temperature acclimation of photosynthetic and isoprene emission characteristics per unit leaf area were primarily driven by structural modifications, and we argue that future studies investigating acclimation to growth temperature must consider structural modifications.     

The plant biodiversity of the Wadi Allaqi Biosphere Reserve (Egypt): impact of Lake Nasser on a desert wadi ecosystem

A data set comprising 95 stands of desert vegetation, collected from the Wadi Allaqi Biosphere Reserve and its environs within the South-Eastern Desert of Egypt during 1985–90, was analysed using multivariate procedures (two-way indicator species analysis: TWINSPAN; detrended correspondence analysis: DCA; canonical correspondence analysis: CCA), to produce a classification of plant communities in the area, and to examine the relationships of these plant communities to natural and man-induced features of the physical environment of the area (in particular, the influence of Lake Nasser, a major impoundment of the River Nile formed in 1964). The vegetation classification produced groupings broader, in both floristic and ecological terms, than those found by earlier studies of this area. In total 78 plant species were recorded from four phytogeographic elements. Four principal vegetation groups were identified, of which one is new to the area, and is the result of major environmental changes affecting the downstream part of the Wadi Allaqi system, following periodic flooding of the wadi by Lake Nasser during the past 30 years. This community was indicated by Tamarix nilotica. There was a strongly-zoned (downstream–upstream) pattern to the vegetation within this lower part of Wadi Allaqi, which appears to be a function of the probability of flooding by the lake. The remaining three vegetation groups occur higher in the wadi basin. Groundwater-dependence appeared to be important in defining a group indicated by Acacia tortilis, as well as the Tamarix nilotica group. The two remaining groups, characterized respectively by Acacia ehrenbergiana and Cullen plicatum, represent vegetation groups which are precipitation-dependent, and which tolerate drier conditions within the Allaqi system.     

Projected changes in the organic carbon stocks of cropland mineral soils of European Russia and the Ukraine, 1990–2070

In this paper, we use the Rothamsted Carbon Model to estimate how cropland mineral soil carbon stocks are likely to change under future climate, and how agricultural management might influence these stocks in the future. The model was run for croplands occurring on mineral soils in European Russia and the Ukraine, representing 74 Mha of cropland in Russia and 31 Mha in the Ukraine. The model used climate data (1990–2070) from the HadCM3 climate model, forced by four Intergovernmental Panel on Climate Change (IPCC) emission scenarios representing various degrees of globalization and emphasis on economic vs. environmental considerations. Three land use scenarios were examined, business as usual (BAU) management, optimal management (OPT) to maximize profit, and soil sustainability (SUS) in which profit was maximized within the constraint that soil carbon must either remain stable or increase. Our findings suggest that soil organic carbon (SOC) will be lost under all climate scenarios, but less is lost under the climate scenarios where environmental considerations are placed higher than purely economic considerations (IPCC B1 and B2 scenarios) compared with the climate associated with emissions resulting from the global free market scenario (IPCC A1FI scenario). More SOC is lost towards the end of the study period. Optimal management is able to reduce this loss of SOC, by up to 44% compared with business as usual management. The soil sustainability scenario could be run only for a limited area, but in that area was shown to increase SOC stocks under three climate scenarios, compared with a loss of SOC under business as usual management in the same area. Improved agricultural soil management will have a significant role to play in the adaptation to, and mitigation of, climate change in this region. Further, our results suggest that this adaptation could be realized without damaging profitability for the farmers, a key criteria affecting whether optimal management can be achieved in reality.     

Use of Camera-Trapping to Estimate Puma Density and Influencing Factors in Central Brazil

Abstract: We used remotely triggered cameras to collect data on Puma (Puma concolor) abundance and occupancy in an area of tropical forest in Brazil where the species' status is poorly known. To evaluate factors influencing puma occupancy we used data from 5 sampling campaigns in 3 consecutive years (2005 to 2007) and 2 seasons (wet and dry), at a state park and a private forest reserve. We estimated puma numbers and density for the 2007 sampling data by developing a standardized individual identification method. We based individual identification on 1) time-stable parameters (SP; physical features that do not change over time), and 2) time-variable parameters (VP; marks that could change over time such as scars and botfly marks). Following individual identification we established a capture-recapture history and analyzed it using closed population capture-mark-recapture models. Puma capture probability was influenced by camera placement (roads vs. trails), sampling year, and prey richness. Puma occupancy was positively associated with species richness and there was a correlation between relative puma and jaguar (Panthera onca) abundance. Identifications enabled us to generate 8 VP histories for each photographed flank, corresponding to 8 individuals. We estimated the sampled population at 9 pumas (SE = 1.03, 95% CI = 8–10 individuals) translating to a density of 3.40 pumas/100 km². Information collected using camera-traps can effectively be used to assess puma population size in tropical forests. As habitat progressively disappears and South American felines become more vulnerable, our results support the critical importance of private forest reserves for conservation.