Safety in numbers and the spatial scaling of density-dependent mortality in a coral reef fish

In coral reef fishes, density-dependent population regulation is commonly mediated via predation on juveniles that have recently settled from the plankton. All else being equal, strong density-dependent mortality should select against the formation of high-density aggregations, yet the juveniles of many reef fishes aggregate. In light of this apparent contradiction, we hypothesized that the form and intensity of density dependence vary with the spatial scale of measurement. Individual groups might enjoy safety in numbers, but predators could still produce density-dependent mortality at larger spatial scales. We investigated this possibility using recently settled juvenile bluehead wrasse, Thalassoma bifasciatum, a small, aggregating reef fish. An initial caging experiment demonstrated that juvenile bluehead wrasse settlers suffer high predation, and spatial settlement patterns indicated that bluehead wrasse juveniles preferentially settle in groups, although they are also found singly. We then monitored the mortality of recently settled juveniles at two spatial scales: microsites, occupied by individual fish or groups of fish and separated by centimeters, and sites, consisting of approximately 2400-m2 areas of reef and separated by kilometers. At the microsite scale, we measured group size and effective population density independently and found that per capita mortality decreased with group size but was not related to density. At the larger spatial scale, however, per capita mortality increased with settler density. This shift in the form of density dependence with spatial scale could reconcile the existence of small-scale aggregative behavior typical of many reef fishes with the population-scale density dependence that is essential to population stability and persistence.     

Ecological drivers of group living in two populations of the communally rearing rodent, Octodon degus

Intraspecific variation in sociality is thought to reflect a trade-off between current fitness benefits and costs that emerge from individuals' decision to join or leave groups. Since those benefits and costs may be influenced by ecological conditions, ecological variation remains a major, ultimate cause of intraspecific variation in sociality. Intraspecific comparisons of mammalian sociality across populations facing different environmental conditions have not provided a consistent relationship between ecological variation and group-living. Thus, we studied two populations of the communally rearing rodent Octodon degus to determine how co-variation between sociality and ecology supports alternative ecological causes of group living. In particular, we examined how variables linked to predation risk, thermal conditions, burrowing costs, and food availability predicted temporal and population variation in sociality. Our study revealed population and temporal variation in total group size and group composition that covaried with population and yearly differences in ecology. In particular, predation risk and burrowing costs are supported as drivers of this social variation in degus. Thermal differences, food quantity and quality were not significant predictors of social group size. In contrast to between populations, social variation within populations was largely uncoupled from ecological differences.     

Dispersal behaviour in a subsocial spider: group conflict and the effect of food availability

This study investigates proximate factors influencing dispersal behaviour in the subsocial spider Amaurobius ferox. Dispersal of spiderlings from the natal web occurred as a progressive sigmoidal function (mean duration of dispersal period=31 days), with considerable individual variability in developmental instar and body mass within the clutch at the time of dispersal. The spiderlings showed a significant decrease in group cohesion on the 6th day after their second moult, which corresponded to the beginning of the dispersal period. Mutual aggressiveness appeared when the spiderlings began to show predatory behaviour (4th day post-second moult) and increased over the course of the dispersal period. While lack of prey in the maternal nest accelerated dispersal behaviour, the addition of prey items lengthened the dispersal period in previously non-fed clutches. Individuals that dispersed were smaller than the remaining individuals when measured on the day 50% of the clutch had dispersed. Timing of the appearance of the developmental characters (second moult, predation activity, agonistic behaviour against siblings, reduction of group cohesion, dispersal) suggests that the dispersal trait might have evolved in consequence of these different functional behaviours. Received: 10 August 1999 / Received in revised form: 15 March 2000 / Accepted: 1 April 2000     

Laying-order effects on sperm numbers and on paternity: comparing three passerine birds with different life histories

In birds, the number of sperm trapped between the perivitelline membranes around the ovum is an estimate of sperm numbers present at the time and place of fertilisation in the female reproductive tract. Sperm numbers may vary among species and between eggs in a clutch and can provide information about sperm utilisation and mechanisms of sperm competition. Here, we describe patterns of variation in sperm numbers through the egg-laying sequence in three passerines in which extra-pair paternity is common, but copulation behaviour differs. Sperm numbers showed no systematic change across the laying sequence in blue tits (Cyanistes caeruleus), but decreased significantly with laying order in bluethroat (Luscinia svecica) and tree swallow (Tachycineta bicolor) clutches. This is consistent with observations that blue tits regularly copulate throughout the laying sequence, while bluethroats stop mate guarding and tree swallows reduce their copulation frequency once the first egg is laid. Nevertheless, cases of a sudden increase in sperm numbers in clutches of bluethroats and tree swallows suggest that successful inseminations also occurred after laying started. In blue tits and bluethroats, sperm numbers were not higher on extra-pair sired eggs than on eggs sired by the social male, suggesting that extra-pair copulations are not timed to the period of peak fertility for each egg. More extra-pair offspring originated from eggs laid early in the sequence in blue tits, while there was no systematic bias in bluethroats. Our results suggest that copulations during the laying sequence are predominantly performed by within-pair males in our study species.     

Low roost-site fidelity in pallid bats: associated factors and effect on group stability

Despite potential costs of changing roost or densites, many animals frequently move between roosts or dens. Pallid bats (Antrozous pallidus) change diurnal roost sites frequently and also reportedly have a variety of cooperative social behaviors, many of which are associated with the care of developing offspring. Roost switching is likely to increase the costs of maintaining the group stability expected with social cooperation. Pallid bats roosting in rock crevices in central Oregon were studied with radiotelemetry to (1) examine characteristics of day roosts, (2) determine what ecological factors were correlated with low roost fidelity, and (3) examine the temporal stability of roosting groups of pregnant and lactating bats. Pallid bats changed roosts an average of once every 1.4 days throughout the summer. The bats exhibited seasonal shifts in roost use, occupying roosts behind thin slabs of rock in cool weather and roosts in deep rock crevices in warm weather. Roost switching was not correlated with daily variations in weather conditions or with structural characteristics of the diurnal roosts, although switching may have allowed bats to maintain familiarity with several roosts that vary in microclimate. Roost switching was positively correlated with ectoparasite load. High ectoparasite levels were correlated with lower body weights in lactating females (Fig. 3), suggesting that parasites may be costly to the bats. Roost switching may be a strategy to decrease ectoparasite loads by interrupting the reproductive cycles of those parasites that spend at least part of their life cycle on the walls of the roost. Both pregnant and lactating pallid bats frequently changed their diurnal roost location, but lactating bats tended to travel shorter distances between consecutive roosts. Lactating bats were more likely to continue to associate with particular roostmates despite changes in the location of the diurnal roost (Fig. 4) and were less likely to roost alone. Although the stability of groups of lactating bats was not absolute, evidence supported the prediction that such groups are more cohesive than are those of pregnant bats. Received: 20 June 1995/Accepted after revision: 13 July 1996     

Porous materials for the recovery of rare earth elements,platinum group metals,and other valuable metals: a review

Environmental Chemistry Letters - The demand for valuable metals such as rare earth elements and platinum group metals is rising fast in the context of the depletion of natural resources...     

Green supply chain management in the chemical industry: structural framework of drivers

ABSTRACT

The main purpose of Green Supply Chain Management (GSCM) is to improve the quality of supply chain management strategies and environmental performance. As per current statistics, the chemical industry is growing fast in Bangladesh. In order to compete for global competition, GSCM is essential in this sector. This paper proposes a systematic approach of structural framework whose aim is to enhance the probability of constructive implementation of GSCM in the field chemical industry in Bangladesh. Therefore, this framework evaluates the appropriate interrelationship along with the drivers of GSCM in the chemical industry. In total, eight drivers were finalized from an associated literature review with the help of survey and by taking expert opinions via the Delphi methodology. In addition to MICMAC analysis, the driving and the dependence powers for all the drivers were determined. Moreover, the structural frameworks for the drivers were developed by means of total interpretive structural modeling (TISM) technique. As a result, the findings indicate that the most significant driver was supplier pressure and willingness and the most important barrier was high cost. Finally, the main objective of this research is expected to help industrial managers to evaluate and understand the critical areas where they should emphasize to implement GSCM in the chemical industry.     

Dissecting the drivers of population cycles: Interactions between parasites and mountain hare demography

There is a growing awareness that cyclic population dynamics in vertebrate species are driven by a complex set of interactions rather than a single causal factor. While theory suggests that direct host-parasite interactions may destabilise population dynamics, the interaction between host and parasite may also influence population dynamics through indirect effects that result in delayed responses to either density or to life-history traits. Using empirical data on mountain hares (Lepus timidus) infected with a nematode parasite (Trichostrongylus retortaeformis), we developed an individual-based model (IBM) that incorporated direct effects and delayed life-history effects (DLHEs) of a macroparasite, alternative transmission mechanisms and seasonality in host population dynamics. The full model describes mean characteristics of observed mountain hare time series and parasite abundance, but by systematically removing model structure we dissect out dynamic influences of DLHEs. The DLHEs were weakly destabilising, increasing the propensity for cyclic dynamics and suggesting DLHEs could be important processes in host-parasite systems. Further, by modifying model structure we identify a strong influence of parasite transmission mechanism on host population stability, and discuss the implications for parasite aggregation mechanisms, host movement and natural geographical variation in host population dynamics. The effect of T. retortaeformis on mountain hares likely forms part of a complex set of interactions that lead to population cycles.     

Climate change and forests of the future: managing in the face of uncertainty.

We offer a conceptual framework for managing forested ecosystems under an assumption that future environments will be different from present but that we cannot be certain about the specifics of change. We encourage flexible approaches that promote reversible and incremental steps, and that favor ongoing learning and capacity to modify direction as situations change. We suggest that no single solution fits all future challenges, especially in the context of changing climates, and that the best strategy is to mix different approaches for different situations. Resources managers will be challenged to integrate adaptation strategies (actions that help ecosystems accommodate changes adaptively) and mitigation strategies (actions that enable ecosystems to reduce anthropogenic influences on global climate) into overall plans. Adaptive strategies include resistance options (forestall impacts and protect highly valued resources), resilience options (improve the capacity of ecosystems to return to desired conditions after disturbance), and response options (facilitate transition of ecosystems from current to new conditions). Mitigation strategies include options to sequester carbon and reduce overall greenhouse gas emissions. Priority-setting approaches (e.g., triage), appropriate for rapidly changing conditions and for situations where needs are greater than available capacity to respond, will become increasingly important in the future.     

The effect of inhibitors of photosynthesis on zooxanthellae in corals and other marine invertebrates

The effect of the selective photosynthesis inhibitors Monuron (CMU), Diuron (DCMU) and methyl viologen on intact algal-marine invertebrate symbiotic associations was studied. CMU or DCMU (5x10^-4M) completely inhibited photosynthesis, both in intact branches, and in suspensions of isolated zooxanthellae from the reef-building coral Pocillopora damicornis. The inhibitory effect was totally reversible in 1 to 3 h after removal of the inhibitor. Similar inhibition of photosynthesis occurred in 8 other marine coelenterates symbiotic with zooxanthellae, and in 1 marine gastropod symbiotic with functional chloroplasts. Neither CMU nor DCMU appeared to affect behavior of the various hosts, such as swimming, phototaxis, phototropism, photoreception, tentacle contraction, ciliary beating and locomotion. Methyl viologen, however, was ineffective in inhibiting photosynthesis in intact P. damicornis at low concentrations, and lethal to the tissues at high concentrations. These observations indicate that CMU and DCMU are potential useful tools for investigation of symbiotic associations. DCMU (5x10^-4M) also reversibly inhibited light-enhanced calcification in P. damicornis. This strongly suggests that light-enhanced calcification is largely photosynthesis dependent, and probably not dependent on some other photobiological effect.Contribution No. 385, Hawaii Institute of Marine Biology, University of Hawaii     

Climate, hydrologic disturbance, and succession: drivers of floodplain pattern

Floodplains are among the world's most threatened ecosystems due to the pervasiveness of dams, levee systems, and other modifications to rivers. Few unaltered floodplains remain where we may examine their dynamics over decadal time scales. Our study provides a detailed examination of landscape change over a 60-year period (1945-2004) on the Nyack floodplain of the Middle Fork of the Flathead River, a free-flowing, gravel-bed river in northwest Montana, USA. We used historical aerial photographs and airborne and satellite imagery to delineate habitats (i.e., mature forest, regenerative forest, water, cobble) within the floodplain. We related changes in the distribution and size of these habitats to hydrologic disturbance and regional climate. Results show a relationship between changes in floodplain habitats and annual flood magnitude, as well as between hydrology and the cooling and warming phases of the Pacific Decadal Oscillation (PDO). Large magnitude floods and greater frequency of moderate floods were associated with the cooling phases of the PDO, resulting in a floodplain environment dominated by extensive restructuring and regeneration of floodplain habitats. Conversely, warming phases of the PDO corresponded with decreases in magnitude, duration, and frequency of critical flows, creating a floodplain environment dominated by late successional vegetation and low levels of physical restructuring. Over the 60-year time series, habitat change was widespread throughout the floodplain, though the relative abundances of the habitats did not change greatly. We conclude that the long- and short-term interactions of climate, floods, and plant succession produce a shifting habitat mosaic that is a fundamental attribute of natural floodplain ecosystems.     

A study of reproduction and other life cycle phenomena in planktonic protists using an acridine orange fluorescence technique

The percentage of dividing individuals and temporal reproductive patterns were determined for natural populations of several planktonic protists including five species of tintinnids, a dinoflagellate, and a diatom. To obtain these data, a method was used in which the nuclei of planktonic ciliates and phytoplankters can be fluorescently stained with acridine orange at the time of collection and fixation. The technique is simple and can be used routinely in studies of reproduction or other life cycle phenomena of natural protistan populations. For the tintinnids, often more than half of the individuals were in some recognizable stage of fission; periodicity in the division process was only observed once and apparently followed a pulse of conjugation in the population. With the diatom Ditylum brightwellii the fluorescent staining technique yielded data on the extent and timing of division which were consistent with, but more complete than, previous enumerations of paired cells.The support of the National Science Foundation (OCE-7819566) is acknowledged     

Untangling the proximate causes and underlying drivers of deforestation and forest degradation in Myanmar

Political transitions often trigger substantial environmental changes. In particular, deforestation can result from the complex interplay among the components of a system—actors, institutions, and existing policies—adapting to new opportunities. A dynamic conceptual map of system components is particularly useful for systems in which multiple actors, each with different worldviews and motivations, may be simultaneously trying to alter different facets of the system, unaware of the impacts on other components. In Myanmar, a global biodiversity hotspot with the largest forest area in mainland Southeast Asia, ongoing political and economic reforms are likely to change the dynamics of deforestation drivers. A fundamental conceptual map of these dynamics is therefore a prerequisite for interventions to reduce deforestation. We used a system‐dynamics approach and causal‐network analysis to determine the proximate causes and underlying drivers of forest loss and degradation in Myanmar from 1995 to 2016 and to articulate the linkages among them. Proximate causes included infrastructure development, timber extraction, and agricultural expansion. These were stimulated primarily by formal agricultural, logging, mining, and hydropower concessions and economic investment and social issues relating to civil war and land tenure. Reform of land laws, the link between natural resource extraction and civil war, and the allocation of agricultural concessions will influence the extent of future forest loss and degradation in Myanmar. The causal‐network analysis identified priority areas for policy interventions, for example, creating a public registry of land‐concession holders to deter corruption in concession allocation. We recommend application of this analytical approach to other countries, particularly those undergoing political transition, to inform policy interventions to reduce forest loss and degradation.     

Rewilding in the face of climate change

Expansion of the global protected-area network has been proposed as a strategy to address threats from accelerating climate change and species extinction. A key step in increasing the effectiveness of such expansion is understanding how novel threats to biodiversity from climate change alter concepts such as rewilding, which have underpinned many proposals for large interconnected reserves. We reviewed potential challenges that climate change poses to rewilding and found that the conservation value of large protected areas persists under climate change. Nevertheless, more attention should be given to protection of microrefugia, macrorefugia, complete environmental gradients, and areas that connect current and future suitable climates and to maintaining ecosystem processes and stabilizing feedbacks via conservation strategies that are resilient to uncertainty regarding climate trends. Because a major element of the threat from climate change stems from its novel geographic patterns, we examined, as an example, the implications for climate-adaptation planning of latitudinal, longitudinal (continental to maritime), and elevational gradients in climate-change exposure across the Yellowstone-to-Yukon region, the locus of an iconic conservation proposal initially designed to conserve wide-ranging carnivore species. In addition to a continued emphasis on conserving intact landscapes, restoration of degraded low-elevation areas within the region is needed to capture sites important for landscape-level climate resilience. Extreme climate exposure projected for boreal North America suggests the need for ambitious goals for expansion of the protected-area network there to include refugia created by topography and ecological features, such as peatlands, whose conservation can also reduce emissions from carbon stored in soil. Qualitative understanding of underlying reserve design rules and the geography of climate-change exposure can strengthen the outcomes of inclusive regional planning processes that identify specific sites for protection.     

Study of the life history of Capitella capitata (Polychaeta: Capitellidae) in Amakusa,South Japan including a comparison with other geographical regions

The life history of Capitella capitata (Fabricius), occurring in Amakusa, South Japan, was studied in detail through field investigations and laboratory experiments. The important life-history characteristics of this species in the present study area are described and compared with those reported in previous studies from various geographic regions. Though some life-history characteristics (extended breeding season throughout almost the whole year, parental brooding habit, and early maturation) are common to all localities, the reproductive mode, larval developmental pattern and morphology are very distinct among the worms from various localities. C. capitata showing these considerable geographical variations should not be treated as a single species. It is suggested that C. capitata, originally defined on the basis of morphological features of adult worms, needs to be subdivided into several species, subspecies, or biological races.     

Round your numbers in rank tests: exact and asymptotic inference and ties

Non-parametric statistical tests are commonly used in the behavioral sciences. Researchers need to be aware that non-parameteric methods involving ranks can perform unreliably as a result of very small amounts of noise added in the storage and manipulation of values by computers, causing spurious reduction in the number of ties. In order to avoid this problem, researchers should round values to an appropriate number of decimal places prior to the ranking procedure to ensure that data points whose values cannot be separated according to the precision of their measurement are recorded as having identical rank. We also recommend exact rather than asymptotic evaluation of p values in non-parametric statistical tests.     

Determination of ammonium uptake and regeneration rates using the seawater dilution method

We have developed a method for the determination of ammonium uptake and regeneration rates applying the principle of the seawater dilution technique. The method is based on the separation of uptake and regeneration processes in the dilution series. A model is used to estimate ammonium uptake and regeneration rates simultaneously, in addition to phytoplankton growth and grazing rates. The method was applied to dilution experiments conducted during a two-year study of the upwelling region off Oregon, USA. Ammonium uptake and regeneration rates determined with our method ranged from 0.5 to 3 mol l^-1d^-1 and from 0.2 to 2.9 mol l^-1d^-1, respectively. These values agree well with those from other studies applying ¹⁵N tracer techniques in the same or similar environments. We found a close coupling between ammonium uptake and regeneration, and a strong relationship between ammonium regeneration and grazing rates. In addition, the nutritional status of the phytoplankton community could be assessed by comparing instantaneous ammonium uptake rates with the specific phytoplankton growth rates. Using the dilution technique to determine ammonium uptake and regeneration rates of the plankton community is a promising alternative to the application of tracer techniques conventionally used to determine these rates.     

Predation, scramble competition, and the vigilance group size effect in dark-eyed juncos (Junco hyemalis)

In socially feeding birds and mammals, as group size increases, individuals devote less time to scanning their environment and more time to feeding. This vigilance “group size effect” has long been attributed to the anti-predatory benefits of group living, but many investigators have suggested that this effect may be driven by scramble competition for limited food. We addressed this issue of causation by focusing on the way in which the scan durations of free-living dark-eyed juncos (Junco hyemalis) decrease with group size. We were particularly interested in vigilance scanning concomitant with the handling of food items, since a decrease in food handling times (i.e. scan durations) with increasing group size could theoretically be driven by scramble competition for limited food resources. However, we showed that food-handling scan durations decrease with group size in an environment with an effectively unlimited food supply. Furthermore, this food-handling effect was qualitatively similar to that observed in the duration of standard vigilance scans (scanning exclusive of food ingestion), and both responded to changes in the risk of predation (proximity of a refuge) as one might expect based upon anti-predator considerations. The group size effects in both food-handling and standard scan durations may reflect a lesser need for personal information about risk as group size increases. Scramble competition may influence vigilance in some circumstances, but demonstrating an effect of competition beyond that of predation may prove challenging. Received: 22 September 1998 / Received in revised form: 1 February 1999 / Accepted: 14 February 1999