Fungal associates of the tree-killing bark beetle,Ips typographus,vary in virulence,ability to degrade conifer phenolics and influence bark beetle tunneling behavior

The bark beetle Ips typographus carries numerous fungi that could be assisting the beetle in colonizing live Norway spruce (Picea abies) trees. Phenolic defenses in spruce phloem are degraded by the beetle's major tree-killing fungus Endoconidiophora polonica, but it is unknown if other beetle associates can also catabolize these compounds. We compared the ability of five fungi commonly associated with I. typographus to degrade phenolic compounds in Norway spruce phloem. Grosmannia penicillata and Grosmannia europhioides were able to degrade stilbenes and flavonoids faster than E. polonica and grow on minimal growth medium with spruce bark constituents as the only nutrients. Furthermore, beetles avoided medium amended with phenolics but marginally preferred medium colonized by fungi. Taken together our results show that different bark beetle-associated fungi have complementary roles in degrading host metabolites and thus might improve this insect's persistence in well defended host tissues.     

Rewiring and indirect effects underpin modularity reshuffling in a marine food web under environmental shifts

Species are characterized by physiological and behavioral plasticity, which is part of their response to environmental shifts. Nonetheless, the collective response of ecological communities to environmental shifts cannot be predicted from the simple sum of individual species responses, since co‐existing species are deeply entangled in interaction networks, such as food webs. For these reasons, the relation between environmental forcing and the structure of food webs is an open problem in ecology. To this respect, one of the main problems in community ecology is defining the role each species plays in shaping community structure, such as by promoting the subdivision of food webs in modules—that is, aggregates composed of species that more frequently interact—which are reported as community stabilizers. In this study, we investigated the relationship between species roles and network modularity under environmental shifts in a highly resolved food web, that is, a “weighted” ecological network reproducing carbon flows among marine planktonic species. Measuring network properties and estimating weighted modularity, we show that species have distinct roles, which differentially affect modularity and mediate structural modifications, such as modules reconfiguration, induced by environmental shifts. Specifically, short‐term environmental changes impact the abundance of planktonic primary producers; this affects their consumers’ behavior and cascades into the overall rearrangement of trophic links. Food web re‐adjustments are both direct, through the rewiring of trophic‐interaction networks, and indirect, with the reconfiguration of trophic cascades. Through such “systemic behavior,” that is, the way the food web acts as a whole, defined by the interactions among its parts, the planktonic food web undergoes a substantial rewiring while keeping almost the same global flow to upper trophic levels, and energetic hierarchy is maintained despite environmental shifts. This behavior suggests the potentially high resilience of plankton networks, such as food webs, to dramatic environmental changes, such as those provoked by global change.     

The functional roles of species in metacommunities,as revealed by metanetwork analyses of bird–plant frugivory networks

Understanding how biodiversity and interaction networks change across environmental gradients is a major challenge in ecology. We integrated metacommunity and metanetwork perspectives to test species’ functional roles in bird–plant frugivory interactions in a fragmented forest landscape in Southwest China, with consequences for seed dispersal. Availability of fruit resources both on and under trees created vertical feeding stratification for frugivorous birds. Bird–plant interactions involving birds feeding only on‐the‐tree or both on and under‐the‐tree (shared) had a higher centrality and contributed more to metanetwork organisation than interactions involving birds feeding only under‐the‐tree. Moreover, bird–plant interactions associated with large‐seeded plants disproportionately contributed to metanetwork organisation and centrality. Consequently, on‐the‐tree and shared birds contributed more to metanetwork organisation whereas under‐the‐tree birds were more involved in local processes. We would expect that species’ roles in the metanetwork will translate into different conservation values for maintaining functioning of seed‐dispersal networks.     

Seed mucilage evolution: Diverse molecular mechanisms generate versatile ecological functions for particular environments

Plant myxodiasporous species have the ability to release a polysaccharidic mucilage upon imbibition of the seed (myxospermy) or the fruit (myxocarpy). This is a widespread capacity in angiosperms providing multiple ecological functions including higher germination efficiency under environmental stresses. It is unclear whether myxodiaspory has one or multiple evolutionary origins and why it was supposedly lost in several species. Here, we summarize recent advances on three main aspects of myxodiaspory. (a) It represents a combination of highly diverse traits at different levels of observation, ranging from the dual tissular origin of mucilage secretory cells to diverse mucilage polysaccharidic composition and ultrastructural organization. (b) An asymmetrical selection pressure is exerted on myxospermy-related genes that were first identified in Arabidopsis thaliana. The A. thaliana and the flax intra-species mucilage variants show that myxospermy is a fast-evolving trait due to high polymorphism in a few genes directly acting on mucilage establishment. In A. thaliana, these actors are downstream of a master regulatory complex and an original phylogenetic overview provided here illustrates that this complex has sequentially evolved after the common ancestor of seed plants and was fully established in the common ancestor of the rosid clade. (c) Newly identified myxodiaspory ecological functions indicate new perspectives such as soil microorganism control and plant establishment support.     

The effect of nest aggregation on the reproductive behaviour of the peacock blenny Salaria pavo

The effect of nest aggregation in courtship behaviour was tested experimentally in an ecologically constrained, sex-role reversed population of the peacock blenny Salaria pavo . Mixed sex groups of eight males and eight females were tested in experimental tanks, containing eight potential nests either aggregated or dispersed. In the aggregated treatment, males spent more time inside their nests and monopolized other potential nests, causing a female-biased operational sex ratio (OSR). In the aggregated treatment, females also expressed more courtship behaviour. The results in general support the prediction that the aggregation of nests promotes male monopolization of potential nests, resulting in fewer nest-holding males and therefore a female-biased OSR that leads to the reversal of sex roles.     

昆虫成虫蜕皮激素研究进展

绝大多数成体昆虫羽化后,幼虫期间负责蜕皮激素合成的前胸腺即发生退化,但在一些内部生理及外部环境因子的调控下,某些成体组织(如生殖腺)可扮演类似前胸腺的角色合成与分泌蜕皮激素。蜕皮激素的功能发挥是经受体介导的,包括核受体(如EcR/USP)和膜受体(如DopEcR),它们广泛表达于成体许多组织,参与成虫行为、生殖、寿命、滞育及免疫应答等众多方面的调节,对维持基本的生理功能具有重要作用。就成虫蜕皮激素的产生组织及影响其滴度的因素、成虫蜕皮激素受体概述与组织分布、成虫蜕皮激素信号通路的功能发挥等研究进展方面加以综述。     

The Role of Zoos in Modern Society—A Comparison of Zoos' Reported Priorities and What Visitors Believe They Should Be

Modern zoos are required to fulfill a growing number of responsibilities including scientific research, wildlife conservation, public recreation, and education. With so many roles and responsibilities and limited funds, zoos have to prioritize their activities in relation to their own specified goals, objectives, and mission statements. Given their desire to nurture community relations and educational opportunities, it is important to determine the extent to which zoos are prioritizing their activities, according to visitors' expectations. This paper presents empirical research of a two staged mixed-methods investigation into zoo priorities from both zoos' and visitors' perspectives. The first stage involved an online questionnaire to which more than 190 zoos across 52 countries reported their priorities and activities. We then undertook in-depth case studies in nine institutions, enabling direct observation of each site within its context, including face-to-face visitor interviews. Our research contrasts the priority given to zoo activities from each perspective and indicates that educating visitors, including school children, is the highest priority activity from the zoos' perspective and that of their visitors. The findings also show that visitors place high value on learning about actions they can take to help conservation efforts. Some inconsistencies between zoos' and visitors' priorities were also evident, such as the different emphasis placed on viewing endemic species, and zoos being a place for people to relax and socialize. The implications of these findings are discussed.     

Autophagy in plants: Physiological roles and post‐translational regulation

In eukaryotes, autophagy helps maintain cellular homeostasis by degrading and recycling cytoplasmic materials via a tightly regulated pathway.Over the past few decades, significant progress has been made towards understanding the physiological functions and molecular regulation of autophagy in plant cells. Increasing evidence indicates that autophagy is essential for plant responses to several developmental and environmental cues, functioning in diverse processes such as senescence, male fertility, root meristem maintenance, responses to nutrient starvation,and biotic and abiotic stress. Recent studies have demonstrated that, similar to nonplant systems,the modulation of core proteins in the plant autophagy machinery by posttranslational modifications such as phosphorylation, ubiquitination,lipidation, S-sulfhydration, S-nitrosylation, and acetylation is widely involved in the initiation and progression of autophagy. Here, we provide an overview of the physiological roles and posttranslational regulation of autophagy in plants.     

Cooperative nest‐defence behaviour and territory quality in a resident and socially monogamous passerine

Nest defence is a fundamental aspect of parental care in secondary cavity‐nesting birds, and predation or competition for nesting sites can involve different defensive behaviours. Because habitat quality determines breeding success, we were interested in whether breeding pairs of the Eurasian nuthatch, Sitta europaea, established in more favourable environment also manifest higher probability of cooperative behaviour during their nest‐site defence. To explore this relationship, we quantified behavioural displays of both parents and analysed activity budget ethogram data from simulated territorial intrusions performed in the chick‐feeding phase with one conspecific and two different heterospecific stimuli (dummies of nuthatch, starling and woodpecker). We found that paired individuals shared their roles during nest‐site defence to a considerable extent. Males had a significantly higher number of attacks on intruders than females, and females performed more threat displays and controls of the brood than males. Multinomial analysis of the cooperative behaviour suggested that pairs in a high‐quality territory had higher probability of reciprocal substitution of different roles towards a balance between attacks, threat displays and nest controls. Contrary to this, pairs in a low‐quality territory had less likely pairwise combinations of simultaneous behavioural states that are associated with effective nest‐site defence. The difference in response probability according to territory quality was, however, highly variable in view of the stimulus that was used in simulated territorial intrusion. Because individual roles and the complex behavioural repertoire of pairs altered in response to territory quality and potential nest‐site competitor or brood predator, our results suggest that the cooperative nest‐defence behaviour could be linked to the breeding success of this year‐round territorial species living in a heterogeneous forest habitat.     

The evolution of sex roles in mate searching

Searching for mates is a critical stage in the life cycle of most internally, and many externally, fertilizing species. Males usually invest more in this costly activity than females, but the reasons for this are poorly understood. Previous models have shown that female‐biased parental investment, including anisogamy, does not by itself select for male‐biased mate searching, so it requires additional explanations. Here, we correct and expand upon earlier models, and present two novel hypotheses that might explain the evolution of male‐biased mate searching. The “carry‐over hypothesis” states that females benefit less from searching if the associated costs affect other stages of the life cycle, rather than arising only while searching. It is relevant to the evolution of morphological traits that improve searching efficiency but are also expressed in other contexts. The “mating window hypothesis” states that females benefit less from searching if their life cycle includes intervals during which the exact timing of mating does not matter for the appropriate timing of reproduction (e.g., due to sperm storage or delayed embryo implantation). Such intervals are more likely to exist for females given the general pattern of greater female parental investment. Our models shed new light on classic arguments about sex role evolution.