Interactions Between Habitat Use and Patterns of Abundance in Coral-dwelling Fishes of the Genus <Emphasis Type="Italic">Gobiodon</Emphasis>

Coral-dwelling fishes from the genus Gobiodon are some of the most habitat specialised fishes on coral reefs. Consequently, we might expect that their population dynamics will be closely associated with the abundance of host corals. I used a combination of log-linear modelling and resource selection ratios to examine patterns of habitat use among eight species of Gobiodon in Kimbe Bay, Papua New Guinea. I then used multiple regression analysis to investigate relationships between the abundance of each species of Gobiodon and the abundance of the corals they inhabited. Each species of Gobiodon used one or more species of coral more frequently than expected by chance. The pattern of habitat use exhibited by each species of Gobiodon did not vary among reef zones or among reefs with different exposures to prevailing winds, despite changes in the relative abundances of corals among reef zones. This consistency in habitat use might be expected if the coral species inhabited confer considerable fitness advantages and, therefore, are strongly preferred. For most species of Gobiodon, abundances among reef zones and exposure regimes were correlated with the abundance of the coral species usually inhabited. Therefore, it appears that habitat availability helps determine abundances of most species of Gobiodon in Kimbe Bay. In addition to correlations with habitat availability, the abundances of G. histrio, G. quinquestrigatus, G. rivulatus (dark form) and the group others were also associated with particular reef zones and exposure regimes. Therefore, in these species, reef type appears to influence patterns of abundance independently of coral availability. In contrast to other species of Gobiodon, the abundance of the most specialised species, Gobiodon sp.A, was not closely associated with the abundance of the only coral species it inhabited. This study demonstrates that even for habitat specialised species, the relationship between habitat availability and abundance varies widely and is multiscale.     

Parental effects and gender specialization in a tropical heterostylous shrub

Abstract.— Male sterility in hermaphroditic species may represent the first step in the evolution toward dioecy. However, gender specialization will not proceed unless the male-sterile individuals compensate for fitness lost through the male function with an increase in fitness through the female function. In the distylous shrub Erythroxylum havanense , thrum plants are partially male-sterile. Using data collected throughout eight years, we investigated whether thrum individuals have an increased performance as female parents, thereby compensating for their loss of male fitness. We found that thrum plants outperformed pins in the probabilities of seed maturation and germination and long-term growth of the seedlings. In turn, pollen from pin plants achieved greater pollen tube growth rates. Our results suggest that the superior performance of the progeny of thrum maternal plants is a consequence of better seed provisioning via effects of the maternal environment, cytotype or nuclear genes. Overall, our results suggest that E. havanense is evolving toward a dioecious state through a gynodioecious intermediate stage. This evolutionary pathway is characterized by an unusual pattern of gender dimorphism with thrums becoming females and pins becoming males. We propose that this pattern may be better explained by the interaction between male-sterility cytoplasmic genes and the heterostyly supergene.     

Do Herbivore-Induced Plant Volatiles Influence Predator Migration and Local Dynamics of Herbivorous and Predatory Mites?

If predators lack information on the prey's position, prey have more chance to escape predation and will therefore reach higher population densities. One of the many possible cues that predators may use to find their prey are herbivore-induced plant volatiles. Although their effects on the behaviour of foraging predators have been well studied, little is known about how these prey-related odours affect predator–prey dynamics on a plant. We hypothesise that herbivore-induced plant volatiles provide the major cue eliciting predator arrestment on prey-infested leaves and that the response to these volatiles ultimately leads to lower prey densities. To test this hypothesis experimentally, we created two types of odour-saturated environments: one with herbivore-induced plant volatiles (treatment), and one with green-leaf volatiles (control). An odour-free environment could not be tested because herbivores require plants for population growth. We measured the rate at which predatory mites (Phytoseiulus persimilis) immigrate, emigrate and exploit a single leaf infested by two-spotted spider mites (Tetranychus urticae). The experiments did not show a significant difference between treatment and control. At best, there was a somewhat higher rate of predator (and possibly also prey) emigration in the treatment. The lack of a pronounced difference between treatment and control indicates that at the spatial scale of the experiments random searching for prey was as effective as directional searching. Alternatively, predators were arrested in the prey patch by responding not merely to herbivore-induced plant volatiles, but also to other prey-related cues, such as web and faeces. Based on our current experience we advocate to increase the spatial scale of the experiment (>1m²) and we provide other suggestions for improving the set-up.     

How is fruit production regulated in the dioecious fleshy-fruited shrub Rhamnus alpinus?

The ‘resource tracking hypothesis’ proposes that a serial regulation of maternal investment might occur at different sequential stages, each establishing a limit for the subsequent ones. Pollinator attraction, resource limitation, selective fruit abortion and climatic conditions can determine the maternal adjustments at each stage. Using a combination of observational and experimental approaches, we studied the maternal regulation of fruit production and seed set in the fleshy-fruited shrub Rhamnus alpinus. Fleshy fruits are especially costly, and the regulation of their production especially interesting. We found that the production of fruits is regulated at two sequential stages, as predicted by the resource-tracking hypothesis. The first stage is related to the number of flowers initiated per branch, which is positively related to the previous year growth of the branch considered, i.e., to the strength of the branch as a sink. Besides, significant variation between females and populations suggests additional micro-environmental or genetic effects. The second stage has to do with the number of flowers that develop into fruits, 72% in 1998 and only 54% in 1999. This stage showed a more complex regulation pattern, though the final number of fruits produced per branch was also related to the strength of the branch. The ability of the species to translocate resources from other branches could compensate for local resource scarcity, as we showed by experimental defoliation and girdling. Although pollen was required for fruit development, pollen supplementation did not increase the proportion of flowers that developed into fruits. We provide evidence that both micro-environmental and genetic effects, as well as climatic conditions may control fruit set, and suggest that the quality of the pollen in the stigma could also determine which flowers are developed into fruits. Overall, our results confirm the resource tracking hypothesis, and indicate that further mechanisms modulate final fruit production.

Zusammenfassung

Nach der „resource tracking”-Hypothese kann die serielle Regulation der mütterlichen Investition in verschiedenen sequenziellen Stadien stattfinden, wobei jedes ein Limit für die folgenden festlegt. Attraktivität für Bestäuber, Ressourcenlimitierung, selektiver Fruchtabwurf und klimatische Bedingungen können die mütterlichen Anpassungen in jedem Stadium bestimmen. Unter Verwendung einer Kombination von Beobachtungen und experimentellen Ansätzen untersuchten wir die mütterliche Regulation der Fruchtproduktion und den Samenansatz bei dem Beerenstrauch Rhamnus alpinus. Beeren sind besonders kostenintensiv und die Regulation ihrer Produktion daher besonders interessant. Wir fanden heraus, dass die Produktion der Früchte in zwei sequentiellen Schritten entsprechend der „resource tracking”-Hypothese reguliert wird. Das erste Stadium steht in Beziehung zur Anzahl der Blüten, die pro Ast angelegt werden. Diese hängt positiv mit dem Vorjahreswachstum des jeweiligen Astes zusammen, d. h. mit der Stärke des Astes als Senke. Die signifikante Variation zwischen weiblichen Sträuchern und Populationen lässt darüber hinaus zusätzliche Mikroumwelt- und genetische Effekte vermuten. Das zweite Stadium hat mit der Anzahl der Blüten zu tun, die sich zu Früchten entwickeln, 72% 1998 und nur 54% 1999. Dieses Stadium zeigte ein komplizierteres Regulationsmuster, obwohl die endgültige Anzahl von produzierten Früchten pro Ast ebenfalls mit der Stärke des Astes zusammenhing. Die Fähigkeit der Art Ressourcen aus anderen Ästen zu verteilen konnte lokale Ressourcenmängel kompensieren. Dies konnten wir durch experimentelle Defoliation und Entrinden zeigen. Obwohl Pollen für die Fruchtentwicklung notwendig war, erhöhte eine Ergänzung von Pollen den Anteil der Blüten nicht, die sich zu Früchten entwickelten. Wir sorgen damit für Beweise, dass sowohl Mikroumwelt- als auch genetische Effekte sowie klimatische Bedingungen den Fruchtansatz kontrollieren und schlagen vor, dass die Qualität der Pollen auf der Narbe ebenfalls bestimmen könnte, welche Blüten sich zu Früchten entwickeln. Insgesamt bestätigen unsere Ergebnisse die „resource tracking”-Hypothese und zeigen, dass weitere Mechanismen die entgültige Fruchtproduktion modulieren.     

Consequence of herbivory for the fitness cost of herbicide resistance: photosynthetic variation in the context of plant-herbivore interactions

The cost of adaptations may depend on environmental conditions. We consider how the fitness cost of resistance to the herbicide triazine in Amaranthus hybridus interacts with folivory from the beetle Disonycha glabrata. Triazine-resistant (TR) genotypes suffer a fitness cost because of a pleiotropic reduction in the light reaction of photosynthesis, which in turn often leads to a reduction in photosynthetic rate. We found that the fitness cost of triazine resistance was 360% greater in the presence than absence of D. glabrata. This resulted from multiple phenotypic trade-offs, with TR plants suffering greater herbivory and displaying a diminished tolerance of damage. Our work highlights the importance of incorporating appropriate ecological variation into the assessment of fitness trade-offs. The results of this study also illustrate the potential for herbivores to impose selection on photosynthetic variation, and for variation in resource acquisition to obscure fitness costs.     

Comparative LCAs for Curbside Recycling Versus Either Landfilling or Incineration with Energy Recovery (12 pp)

Background This article describes two projects conducted recently by Sound Resource Management (SRMG) – one for the San Luis Obispo County Integrated Waste Management Authority (SLO IWMA) and the other for the Washington State Department of Ecology (WA Ecology). For both projects we used life cycle assessment (LCA) techniques to evaluate the environmental burdens associated with collection and management of municipal solid waste. Both projects compared environmental burdens from curbside collection for recycling, processing, and market shipment of recyclable materials picked up from households and/or businesses against environmental burdens from curbside collection and disposal of mixed solid waste. Method logy. The SLO IWMA project compared curbside recycling for households and businesses against curbside collection of mixed refuse for deposition in a landfill where landfill gas is collected and used for energy generation. The WA Ecology project compared residential curbside recycling in three regions of Washington State against the collection and deposition of those same materials in landfills where landfill gas is collected and flared. In the fourth Washington region (the urban east encompassing Spokane) the WA Ecology project compared curbside recycling against collection and deposition in a wasteto- energy (WTE) combustion facility used to generate electricity for sale on the regional energy grid. During the time period covered by the SLO study, households and businesses used either one or two containers, depending on the collection company, to separate and set out materials for recycling in San Luis Obispo County. During the time of the WA study households used either two or three containers for the residential curbside recycling programs surveyed for that study. Typically participants in collection programs requiring separation of materials into more than one container used one of the containers to separate at least glass bottles and jars from other recyclable materials. For the WA Ecology project SRMG used life cycle inventory (LCI) techniques to estimate atmospheric emissions of ten pollutants, waterborne emissions of seventeen pollutants, and emissions of industrial solid waste, as well as total energy consumption, associated with curbside recycling and disposal methods for managing municipal solid waste. Emissions estimates came from the Decision Support Tool (DST) developed for assessing the cost and environmental burdens of integrated solid waste management strategies by North Carolina State University (NCSU) in conjunction with Research Triangle Institute (RTI) and the US Environmental Protection Agency (US EPA)1. RTI used the DST to estimate environmental emissions during the life cycle of products. RTI provided those estimates to SRMG for analysis in the WA Ecology project2. For the SLO IWMA project SRMG also used LCI techniques and data from the Municipal Solid Waste Life- Cycle Database (Database), prepared by RTI with the support of US EPA during DST model development, to estimate environmental emissions from solid waste management practices3. Once we developed the LCI data for each project, SRMG then prepared a life cycle environmental impacts assessment of the environmental burdens associated with these emissions using the Environmental Problems approach discussed in the methodology section of this article. Finally, for the WA study we also developed estimates of the economic costs of certain environmental impacts in order to assess whether recycling was cost effective from a societal point of view. Conclusions Recycling of newspaper, cardboard, mixed paper, glass bottles and jars, aluminum cans, tin-plated steel cans, plastic bottles, and other conventionally recoverable materials found in household and business municipal solid wastes consumes less energy and imposes lower environmental burdens than disposal of solid waste materials via landfilling or incineration, even after accounting for energy that may be recovered from waste materials at either type disposal facility. This result holds for a variety of environmental impacts, including global warming, acidification, eutrophication, disability adjusted life year (DALY) losses from emission of criteria air pollutants, human toxicity and ecological toxicity. The basic reason for this conclusion is that energy conservation and pollution prevention engendered by using recycled rather than virgin materials as feedstocks for manufacturing new products tends to be an order of magnitude greater than the additional energy and environmental burdens imposed by curbside collection trucks, recycled material processing facilities, and transportation of processed recyclables to end-use markets. Furthermore, the energy grid offsets and associated reductions in environmental burdens yielded by generation of energy from landfill gas or from waste combustion are substantially smaller then the upstream energy and pollution offsets attained by manufacturing products with processed recyclables, even after accounting for energy usage and pollutant emissions during collection, processing and transportation to end-use markets for recycled materials. The analysis that leads to this conclusion included a direct comparison of the collection for recycling versus collection for disposal of the same quantity and composition of materials handled through existing curbside recycling programs in Washington State. This comparison provides a better approximation to marginal energy usage and environmental burdens of recycling versus disposal for recyclable materials in solid waste than does a comparison of the energy and environmental impacts of recycling versus management methods for handling typical mixed refuse, where that refuse includes organics and non-recyclables in addition to whatever recyclable materials may remain in the garbage. Finally, the analysis also suggests that, under reasonable assumptions regarding the economic cost of impacts from pollutant emissions, the societal benefits of recycling outweigh its costs.     

Community-based Monitoring of Natural Resource Use and Forest Quality in Montane Forests and Miombo Woodlands of Tanzania

A community-based monitoring system that focuses on natural resource use and forest quality in montane evergreen forest and miombo woodland areas was developed and implemented in 23 villages in 2002 as part of a participatory forest management regime in Iringa District, Tanzania. The scheme was developed to suit the needs and capacities of locally-elected natural resource committees managing and monitoring natural forests. Rather than measuring biodiversity, the monitoring is focused on resource extraction and disturbance. High levels of commitment to the monitoring were displayed by village level managers, and the preliminary feed-back indicates that the monitoring scheme provides them with the relevant information needed to suggest appropriate management interventions. While external support has been essential to cover development costs, natural resource revenue generated at village level can provide most of the running costs. Once developed, the scheme can, however, be transferred to similar areas at significantly lower costs that can be met by Tanzanian District budgets. Natural resource revenue generated from montane forests is generally much lower than in woodland areas due to restrictions on resource extraction imposed as a consequence of national and international interests. Opportunities to provide economic incentives for montane forest managers through direct utilisation of the resource are limited and it remains to be seen whether other non-economic incentives can sustain long term commitment in these biodiversity rich areas. Findings indicate that the key elements of this local resource utilisation monitoring scheme are simplicity, incentive mechanisms, transparency and accountability, and autonomy for local managers. However, the methods may not provide sufficient data on changes in biodiversity values in the high value forests and may need to be augmented by conventional monitoring by scientists funded by national or international institutions. Elements of the scheme are now being institutionalised within the forestry sector in Tanzania.     

Parallel Evolution,not Always so Parallel: Comparison of Small Benthic Charr, <Emphasis Type="Italic">Salvelinus alpinus</Emphasis>, from Grímsnes and Thingvallavatn,Iceland

Synopsis Iceland is unique in terms of geologically young freshwater systems and rapid adaptations of fresh water fishes to diverse habitats, e.g. lava with ground water flow. Iceland has six species of freshwater fishes, including Arctic charr, Salvelinus alpinus. Previous research has shown great diversity within this species. Four different morphs of Arctic charr are found in one lake, Thingvallavatn, including a small benthivorous charr. Similar populations of small benthic charr are known from several other Icelandic freshwater locations, including Nautavakir in Grímsnes. Our comparison of the small benthic charr morphs in Thingvallavatn and in Grímsnes showed that they are similar in morphology but distinguishable in several characteristics. Small benthic charr in Grímsnes and Thingvallavatn demonstrate similar adaptations and are an example of parallel evolution. However, subtle morphological differences between them indicate further specialized adaptations at each location.     

Mycorrhizas improve nitrogen nutrition of Trifolium repens after 8 yr of selection under elevated atmospheric CO2 partial pressure

Altered environmental conditions may change populations of arbuscular mycorrhizal fungi and thereby affect mycorrhizal functioning. We investigated whether 8 yr of free-air CO2 enrichment has selected fungi that differently influence the nutrition and growth of host plants. In a controlled pot experiment, two sets of seven randomly picked single spore isolates, originating from field plots of elevated (60 Pa) or ambient CO2 partial pressure (pCO2), were inoculated on nodulated Trifolium repens (white clover) plants. Fungal isolates belonged to the Glomus claroideum or Glomus intraradices species complex, and host plants were clonal micropropagates derived from nine genets. Total nitrogen (N) concentration was increased in leaves of plants inoculated with fungal isolates from elevated-pCO2 plots. These isolates took up nearly twice as much N from the soil as isolates from ambient-pCO2 plots and showed much greater stimulation of biological N2 fixation. The morpho-species identity of isolates had a more pronounced effect on N2 fixation and on root length colonized than isolate identity. We conclude that rising atmospheric pCO2 may select for fungal strains that will help their host plants to meet increased N demands.     

Vegetation in contrasting soil water sites of upland herbaceous grasslands and N:P ratios as indicators of nutrient limitation

Effects of differences in long-term water supply were examined on soil characteristics, primary production and species composition in a wet and a dry site of an upland herbaceous grassland. Also the responses of species to N and P enrichments were examined. N and P concentrations of non-legume species were positively related, indicating that biomass N:P ratios seem to be mainly determined by N:P supply ratios. Forbs had generally higher concentrations than graminoids. Intermittent water inundation of soil in the wet site resulted in greater soil N and P availability. The greater productivity of this site promoted the growth of forbs. A fertilizer experiment showed that biomass was limited by N only in the wet site, but by both nutrients in the dry one. The species with the higher N and P concentrations were favored more after N and P enrichment, respectively; however, species enhancement was not related to N:P ratios of species. This indicates that N and P concentrations of species, rather than N:P ratios of species, are better predictors of species responses to N and P enrichment. N:P ratios of whole communities were 8.73 for the wet and 11.36 for the dry site. These values in comparison with the responses of plant communities to N and P fertilization show that thresholds of N:P ratios indicative of N or P limitation are much lower than those found for European wetlands.