Active protection of unrelated offspring against parasitoids. A byproduct of self defense?

Natural enemies exert selection pressure on their prey. Predators and parasitoids drive their prey into the evolution of novel traits to cope with this stress. When eggs and juveniles are the target of enemies, defense strategies may rely on adults. However, it is not easy to predict whether adults should actively protect unrelated offspring. Females of the golden egg bug (Phyllomorpha laciniata) mainly oviposit on conspecifics of either sex. Females can also lay eggs on their food plant. Eggs placed on plants suffer from a higher mortality caused by natural enemies than eggs carried by bugs. Females never carry their own eggs and males are seldom related to the eggs they carry. We experimentally explored if conspecifics protect the eggs by studying the behavioral interaction between P. laciniata individuals and the specialist egg parasitoid Gryon bolivari. All bugs exhibited active responses against parasitoids regardless of the sex of the bug, the egg load, and their mating status. Most of the responses prevented parasitoids from reaching the eggs, and thus they reduced the risk of egg parasitization. Although responses of bugs were effective to overcome parasitoid attacks, we suggest that egg protection against parasitoids has evolved as a co-opted trait from a general defense of adult bugs against enemies. In this system, egg defense is not an individual's strategy to protect the offspring, but rather a consequence of the eggs being attached to one's body. It may also explain the low parasitization carried eggs suffer in the wild. The results further highlight the idea of conspecifics as an enemy-free space in P. laciniata.     

The values and vulnerabilities of ‘Star Wars Island’: exploring tensions in the sustainable management of the Skellig Michael World Heritage Site

This paper explores challenges in reconciling the cultural, economic and ecological pillars of the sustainable development concept. It does so by examining how conflicts in the management of an island off the Irish coast called Skellig Michael, which has been internationally designated for its significant cultural and ecological attributes, have been intensified by: (a) increasing tourist numbers; (b) a re-framing of the site’s identity and (c) changing visitor motivations. These have resulted from the amplified attention the island has received following the release of Star Wars: The Force Awakens and The Last Jedi in which it features prominently. Following a critical identification and discussion of the fault lines between different stakeholders involved in the conservation and use of the island, the paper advances a roadmap for action to help resolve animosity in the governance of the site and facilitate its sustainable management in the context of changing visitor numbers and profiles.     

Are politicians office or policy motivated? The case of U.S. governors' environmental policies

Are elected politicians primarily motivated by holding office, thus choosing environmental policies accordingly? Or are they motivated by the chance to implement their preferred environmental policies? Do governors have character, in the sense that they promise and implement environmental policies consistent with their own preferences? To answer these questions, we study the differences in environmental spending across both re-electable and lame duck governors from the two main political parties. In our empirical analysis, we make use of parametric and non-parametric regression-discontinuity approaches. While re-electable governors do not set significantly different policies, lame duck governors do. We argue that in the area of environmental policy governors appear to be primarily office motivated and lack character.     

Strategic implications of counter-geoengineering: Clash or cooperation?

Solar geoengineering has received increasing attention as an option to temporarily stabilize global temperatures. A key concern is that heterogeneous preferences over the optimal amount of cooling combined with low deployment costs may allow the country with the strongest incentive for cooling, the so-called free-driver, to impose a substantial externality on the rest of the world. We analyze whether the threat of counter-geoengineering technologies capable of negating the climatic effects of solar geoengineering can overcome the free-driver problem and tilt the game in favour of international cooperation. Our game-theoretical model of countries with asymmetric preferences allows for a rigorous analysis of the strategic interaction surrounding solar geoengineering and counter-geoengineering. We find that counter-geoengineering prevents the free-driver outcome, but not always with benign effects. The presence of counter-geoengineering leads to either a climate clash where countries engage in a non-cooperative escalation of opposing climate interventions (negative welfare effect), a moratorium treaty where countries commit to abstain from either type of climate intervention (indeterminate welfare effect), or cooperative deployment of solar geoengineering (positive welfare effect). We show that the outcome depends crucially on the degree of asymmetry in temperature preferences between countries.     

Did the pre-1980 use of in-stream structures improve streams? A reanalysis of historical data.

In the 1930s, after only three years of scientific investigation at the University of Michigan Institute for Fisheries Research, cheap labor and government-sponsored conservation projects spearheaded by the Civilian Conservation Corps allowed the widespread adoption of in-stream structures throughout the United States. From the 1940s through the 1970s, designs of in-stream structures remained essentially unchanged, and their use continued. Despite a large investment in the construction of in-stream structures over these four decades, very few studies were undertaken to evaluate the impacts of the structures on the channel and its aquatic populations. The studies that were undertaken to evaluate the impact of the structures were often flawed. The use of habitat structures became an "accepted practice," however, and early evaluation studies were used as proof that the structures were beneficial to aquatic organisms. A review of the literature reveals that, despite published claims to the contrary, little evidence of the successful use of in-stream structures to improve fish populations exists prior to 1980. A total of 79 publications were checked, and 215 statistical analyses were performed. Only seven analyses provide evidence for a benefit of structures on fish populations, and five of these analyses are suspect because data were misclassified by the original authors. Many of the changes in population measures reported in early publications appear to result from changes in fishing pressure that often accompanied channel modifications. Modern evaluations of channel-restoration projects must consider the influence of fishing pressure to ensure that efforts to improve fish habitat achieve the benefits intended. My statistical results show that the traditional use of in-stream structures for channel restoration design does not ensure demonstrable benefits for fish communities, and their ability to increase fish populations should not be presumed.     

Visions for the future of transport: Approaching consensus?

Many cities and national authorities have made substantial progress in developing transport strategies to reconcile environmental pressures with the increasing demand for travel. However, there is still some doubt as to what are the key ingredients of a successful strategy and progress in implementing such changes has been slow. Research is needed to better understand what are the essential ingredients to a balanced transport policy, the constraints, which are preventing these from being implemented, and the acceptability of such changes. This paper reports on the outcomes of a project funded under the Rees Jeffreys Road Fund research programme 'From Realism to Reality', which aims to identify the elements necessary for a successful transport policy in the UK into the 21st century, The project seeks to develop a vision for the transport system of the future through an understanding of the extent of the current problems in the transport sector and an examination of the range and effectiveness of options and instruments available to resolve them. The paper examines a range of visions that are currently in the public domain. Results show that there is a degree of consistency in the general aims and objectives of such visions, but that there is rather less consensus in the means proposed to achieve those aims.     

Within-plant allocation of a chemical defense in Secale cereale. Is concentration the appropriate currency of allocation?

Summary. The among-leaves allocation of DIBOA, a hydroxamic acid associated with plant resistance, in the shoot of rye (Secale cereale) was evaluated over the vegetative development of the plant. The appropriateness of using the concentration of secondary metabolites, DIBOA in this case, as the parameter to evaluate defense allocation in plants is discussed. Both biological and statistical arguments are put forward to suggest that allocation of chemical defenses should refer to absolute content and not to concentration. Results showed that leaf age was significantly linked to leaf concentration of DIBOA, young leaves having higher concentrations. In contrast, leaf content of DIBOA, our proposed currency of allocation, was not significantly higher in younger leaves. Furthermore, a regression analysis showed that the DIBOA content of leaves was better explained by the leaf relative biomass (proportion of shoot biomass) than by leaf biomass itself. It is suggested that, rather than leaf age, leaf relative biomass is the major factor determining DIBOA allocation in rye shoots. It is proposed that studies addressing within-plant defense allocation should use chemical defense content as the currency, emphasizing the major factors driving this process and its underlying mechanisms. Likewise, it is proposed that studies aiming at characterizing optimal patterns of plant defense should use chemical defense concentration as the currency, and be accompanied by evaluations of the actual resistance against herbivores of the plant parts analyzed, together with the effect on plant fitness. Received 19 February 1999; accepted 28 April 1999.     

Timber Certification: Where Is the Voice of the Biologist?

Editor's note: This Conservation Forum begins with a reprinted editorial by Elizabeth Bennett from the August 2000 issue of Conservation Biology . Several papers were submitted in repsonse to that piece, and it is reprinted here to start this forum.     

Guppies as heterospecific facilitators: a precursor of exploratory behavior?

Behavior can explain population-level processes such as dispersal, yet connecting a specific behavioral phenomenon with a larger ecological pattern is often speculative rather than supported by experimental studies. We investigate how exploratory behavior may develop in the killifish, Rivulus hartii through association with another taxon, the guppy, Poecilia reticulata. We hypothesize that exploratory behavior is enhanced by nearby guppies, which embolden Rivulus to move along the river edge, through zones of high predation risk. We tested individual boldness in the presence of both guppies and conspecifics. We also tested for the effect of prior experience with guppies, comparing boldness in Rivulus from locations in which it was either allopatric to or sympatric with guppies. Guppies increased boldness in Rivulus, equivalent to the effect of conspecifics, and prior experience with guppies also increased boldness over that of inexperienced Rivulus. Sympatric Rivulus were shy compared with the allopatric ones when each was tested alone, but this relationship reversed when guppies were present, showing that boldness is a plastic trait that can be influenced by the population of origin. An experimental field-stream test showed that guppies increased movement of Rivulus under predation threat, supporting links in a conceptual framework that connects a behavioral phenomenon, exploratory boldness, with a larger ecological pattern, selection of favorable habitats that, in turn, can lead to increased reproduction and fitness relative to non-dispersers.     

Selective feeding of littoral harpacticoids on diatom algae: hungry gourmands?

We studied benthic harpacticoid grazing on diatom algae from two sites on the White Sea intertidal sandflat. Diatoms from sediments and from harpacticoid gut contents were sampled in situ, identified and counted, and grazing rates were calculated by two ways: (1) using potential daily ration estimations and (2) from the gut content and gut-residence time data. Paraleptastacus kliei did not contain any diatoms in the guts and presumably fed on other objects (bacteria or flagellates). Two other dominating species studied, Heterolaophonte minuta and Huntemannia jadensis, contained an average of 604 and 222 diatom cells per specimen. Diet composition differed significantly from the natural algal community. Two diatoms of intermediate cell size (Nitzschia palea var. debilis and Navicula sp.) contributed 92–97% of gut content for H. minuta and 58–81% for Hn. jadensis, whereas these diatoms amounted to only about 10% of biomass in native community. Mean consumption rates were estimated as 50–200 μg of wet biomass/day/cm², so the harpacticoids grazed only between 3 and 11% of the total microalgae biomass per day. The grazing impact on the two preferred diatom populations, however, was much more intensive, 10–30% per day for Navicula sp. and 55–228% for N. palea. Therefore, native harpacticoid populations demonstrate highly selective feeding and could be strongly limited by their food in spite of seemingly plentiful total abundance of microphytobenthos. This disproportionally high grazing pressure upon some species apparently could affect the structure of microalgae communities resulting in low relative abundance of mid-sized forms. We hypothesize that a very dynamic spatio-temporal distribution of epibenthic harpacticoids (short-living micropatches) may be the possible adaptation to such local food limitation.     

Social learning of predators by coral reef fish: does observer number influence acquisition of information?

Prey that are capable of continuously learning the identity of new predators whilst adjusting the intensity of their responses to match their level of risk, are often at a substantive advantage. Learning about predators can occur through direct experience or through social learning from experienced individuals. Social learning provides individuals with an effective means of acquiring information while reducing the costs associated with direct learning. Under a natural setting, social learning is likely to occur between more than two individuals. As such, investigating the effect that group size has on the ability of individuals to acquire information is vital to understanding social learning dynamics. Given the characteristics of coral reefs and the biology of coral reef fishes, these habitats are an ideal medium to test whether group size affects the transmission of information. Using newly settled damselfish (Pomacentrus amboinensis), we examined whether the number of observers present influences transmission of information. We showed that: (1) predator recognition is socially transmitted from predator-experienced to predator-naïve individuals regardless of group size, and that (2) the level of response displayed by the observer does not differ following learning in different sized groups. Our study highlights that information on predator identities is able to be passed onto group members quickly without a dilution of information content.     

State-of-the-science assessment of non-asbestos amphibole exposure: Is there a cancer risk?

The distinction between amphibole asbestos fibers and non-asbestos amphibole particles has important implications for assessing potential cancer risks associated with exposure to amphibole asbestos or amphibole-containing products. Exposure to amphibole asbestos fibers can pose a cancer risk due to its ability to reside for long periods of time in the deep lung (i.e., biopersistence). In contrast, non-asbestos amphibole particles are usually cleared rapidly from the lung and do not pose similar respiratory risks even at high doses. Most regulatory and public health agencies, as well as scientific bodies, agree that non-asbestos amphiboles possess reduced biological (e.g., carcinogenic) activity. Although non-asbestos amphibole minerals have been excluded historically from Federal regulations, non-asbestos structures may be counted as asbestos fibers on the basis of dimensional criteria specified in analytical protocols. Given the potential to mischaracterize a non-asbestos structure as a “true” asbestos fiber, our objective was to assess whether exposure to non-asbestos amphiboles that may meet the dimensional criteria for counting as a fiber pose a cancer risk similar to amphibole asbestos. We reviewed analytical methods as well as the mineralogical, epidemiological, and toxicological literature for non-asbestos amphiboles. No evidence of demonstrable cancer effects from exposure to non-asbestos amphiboles that may be counted as fibers, under certain assessment protocols, was found. Data gaps (industrial hygiene data for amphibole-exposed cohorts), inconsistencies (analytical laboratory methods/protocols used to count fibers), and sources of potential bias from misclassification of exposure were identified.     

Mechanisms of selective attention in grasshopper choruses: who listens to whom?

In many rhythmically signaling species of acoustic insects and anurans, males form choruses at typical population densities. Recent findings that females may prefer leading calls indicate that the timing of a male's signals relative to those of neighboring choruses is an important component of mate attraction. Within a chorus, however, males cannot time their calls such that they lead all neighbors. Hence, they are expected to show selective attention toward only a subset of the group. We used field playback experiments to determine the incidence of and mechanism(s) responsible for selective attention in choruses of the territorial grasshoppers Ligurotettix coquilletti and L. planum. Our data revealed significant selective attention in both species and are inconsistent with either fixed-threshold or fixed-number mechanisms. Rather, regulation of selective attention by a sliding-threshold mechanism is supported. We discuss these results in the context of the evolution of chorus structure. Received: 24 September 1997 / Accepted after revision: 28 February 1998     

Influence of interspecific competitors on behavioral thermoregulation: developmental or acute plasticity?

Behavioral Ecology and Sociobiology - Deep-diving sperm whales have a complex social structure and the largest brain of any animal, but very little is known about the ontogeny of their diving,...