Amphicarpy is a form of diversified bet-hedging expressed mostly in annual plants, where two types of offspring are produced with two distinct ecological roles: longrange aerial dispersers and highly competitive subterranean, sedentary fruit. Emex spinosa is a semi-arid, amphicarpic annual, inhabiting habitats with different levels of environmental variation. We tested the hypothesis that, in E. spinosa, bet-hedging may be ''finetuned'' by plasticity in the phenotype ratio (aerial/subterranean fruit mass) as a function of environmental conditions. We conducted a greenhouse experiment, manipulating nutrient availability and intraspecific density, to determine the pattern of ratio shifts. In order to determine whether the integrated strategy is an adaptation to variable habitats, a similar common garden experiment was conducted, comparing two natural populations differing in environmental variability. The offspring ratio shifted in response to both nutrient availability and plant density. In pots containing single plants the ratio increased steeply with nutrient availability, while in pots containing eight plants a more moderate increase occurred. These shifts were the result of plasticity in allocation to both achene types, as well as ontogenetic effects on aerial achene production. The degree of response increased with the heterogeneity of the habitat of origin. We found evidence for an adaptive integrated strategy, with bet-hedging ''fine-tuned'' by phenotypic plasticity. Strenuous conditions tended to shift the offspring ratio towards securing subterranean reproductive success, while favorable conditions resulted in a shift towards dispersible achenes.

Structural complexity generally reduces predation and cannibalism rates. Although the benefits from this effect vary among environmental contexts and through time, it has been the common explanation for high species abundance in complex habitats. We hypothesized that oviposition habitat selection for structural complexity depends on the expected trophic function of the progeny. In Salamandra infraimmaculata larvae, expected trophic function is dictated by their sequence of deposition. First cohorts cannibalize later-arriving cohorts, while all compete for shared prey resources. In a mesocosm experiment, we show that gravid salamanders facing conspecific-free pools preferred structurally simple habitats (no rocks), while females facing only pools with older conspecific larvae preferred complex habitats (with rocks). Context-dependent preference of habitat complexity for managing food/safety trade-offs may be extended from classic foraging patch decisions to breeding habitat selection. These trade-offs vary with dynamic larval processes such as priority effects and ontogenetic diet shifts, potentially leading to complex maternal parturition behaviours.

BackgroundTable olives (Olea europaea L.), despite their widespread production, are still harvested manually. The low efficiency of manual harvesting and the rising costs of labor have reduced the profitability of this crop. A selective abscission treatment, inducing abscission of fruits but not leaves, is crucial for the adoption of mechanical harvesting of table olives. In the present work we studied the anatomical and molecular differences between the three abscission zones (AZs) of olive fruits and leaves.ResultsThe fruit abscission zone 3 (FAZ3), located between the fruit and the pedicel, was found to be the active AZ in mature fruits and is sensitive to ethephon, whereas FAZ2, between the pedicel and the rachis, is the flower active AZ as well as functioning as the most ethephon induced fruit AZ. We found anatomical differences between the leaf AZ (LAZ) and the two FAZs. Unlike the FAZs, the LAZ is characterized by small cells with less pectin compared to neighboring cells. In an attempt to differentiate between the fruit and leaf AZs, we examined the effect of treating olive-bearing trees with ethephon, an ethylene-releasing compound, with or without antioxidants, on the detachment force (DF) of fruits and leaves 5 days after the treatment. Ethephon treatment enhanced pectinase activity and reduced DF in all the three olive AZs. A transcriptomic analysis of the three olive AZs after ethephon treatment revealed induction of several genes encoding for hormones (ethylene, auxin and ABA), as well as for several cell wall degrading enzymes. However, up-regulation of cellulase genes was found only in the LAZ. Many genes involved in oxidative stress were induced by the ethephon treatment in the LAZ alone. In addition, we found that reactive oxygen species (ROS) mediated abscission in response to ethephon only in leaves. Thus, adding antioxidants such as ascorbic acid or butyric acid to the ethephon inhibited leaf abscission but enhanced fruit abscission.ConclusionOur findings suggest that treating olive-bearing trees with a combination of ethephon and antioxidants reduces the detachment force (DF) of fruit without weakening that of the leaves. Hence, this selective abscission treatment may be used in turn to promote mechanized harvest of olives.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-017-1035-1) contains supplementary material, which is available to authorized users.

Bees are important plant pollinators in agricultural and natural ecosystems. High average annual losses of honey bee (Apis mellifera) colonies in some parts of the world, and regional population declines of some mining bee species (Andrena spp.), are attributed to multiple factors including habitat loss, lack of quality forage, insecticide exposure, and pathogens, including viruses. While research has primarily focused on viruses in honey bees, many of these viruses have a broad host range. It is therefore important to apply a community level approach in studying the epidemiology of bee viruses. We utilized high-throughput sequencing to evaluate viral diversity and viral sharing in sympatric, co-foraging bees in the context of habitat type. Variants of four common viruses (i.e., black queen cell virus, deformed wing virus, Lake Sinai virus 2, and Lake Sinai virus NE) were identified in honey bee and mining bee samples, and the high degree of nucleotide identity in the virus consensus sequences obtained from both taxa indicates virus sharing. We discovered a unique bipartite + ssRNA Tombo-like virus, Andrena-associated bee virus-1 (AnBV-1). AnBV-1 infects mining bees, honey bees, and primary honey bee pupal cells maintained in culture. AnBV-1 prevalence and abundance was greater in mining bees than in honey bees. Statistical modeling that examined the roles of ecological factors, including floral diversity and abundance, indicated that AnBV-1 infection prevalence in honey bees was greater in habitats with low floral diversity and abundance, and that interspecific virus transmission is strongly modulated by the floral community in the habitat. These results suggest that land management strategies that aim to enhance floral diversity and abundance may reduce AnBV-1 spread between co-foraging bees.

The negative effects of habitat fragmentation and population isolation on population viability, genetic variability and structuring are well documented, and conservation plans failing to take into account spatial population structure and connectivity can be ineffectual. Of special concern are populations at the periphery of the species range that might show reduced genetic diversity, thus affecting their adaptive potential at environmental margins. We investigated genetic variability and differentiation of the globally near threatened and locally endangered fire salamander Salamandra infraimmaculata in northern Israel, an area that represents the periphery of this species' distribution range. Analyses of variability in 15 microsatellite loci from 20 sites revealed substantial population structuring, most of which was due to a strong subdivision between two regions separated by a heavily urbanized valley. In addition, levels of genetic variability within populations were lowest in the peripheral, southernmost populations. These results suggest that the conservation plans for this species should recognize the lower diversity and increased divergence in the peripheral regions, and take into account the observed spatial population structure when devising strategies and measures to ensure the species persistence. bs_bs_banner Animal Conservation. Print ISSN 1367-9430 L. Blank et al. Population genetic structure of fire salamander Animal Conservation 16 (2013) 412-421