Sex and segregation in temperate bats

Many temperate insectivorous bats show marked sexual segregation during the summer, but in spectacular, pre-hibernation swarming, gather at caves to mate. In many species, sexual segregation is probably due to a gradient in aerial insect availability that confines females to lower elevations, where high reproductive costs are met by an abundant and reliable food supply. In the hawking and trawling Myotis daubentonii, we show that alongside inter-sexual segregation, there is intra-male segregation and suggest that this results from the exclusion of most males from high-quality habitat. These apparently excluded males suffer reduced foraging efficiency and mating success relative to males that roost with the females in summer. Changes in resources and behaviour at the end of the summer lead to a change in strategy that gives all males a chance to mate during swarming, but this does not overcome the paternity advantage to males that spend the summer with the females.     

Crenarchaeota and Euryarchaeota in temperate estuarine sediments

AIMS: Application of molecular techniques to ecological studies has unveiled a wide diversity of micro-organisms in natural communities, previously unknown to microbial ecologists. New lineages of Archaea were retrieved from several non-extreme environments, showing that these micro-organisms are present in a large variety of ecosystems. The aim was therefore to assess the presence and diversity of Archaea in the sediments of the river Douro estuary (Portugal), relating the results obtained to ecological data. METHODS AND RESULTS: Total DNA was extracted from sediment samples obtained from an estuary deprived of vegetation, amplified by PCR and the resulting DNA fragments cloned. The archaeal origin of the cloned inserts was checked by Southern blot, dot blot or colony blot hybridization. Recombinant plasmids were further analysed by restriction with AvaII and selected for sequencing. Phylogenetic analyses of 14 sequences revealed the presence of members of the domain Archaea. Most of the sequences could be assigned to the kingdom Crenarchaeota. CONCLUSION: Most of these sequences were closely related to those obtained from non-extreme Crenarchaeota members previously retrieved from diverse ecosystems, such as freshwater and marine environments. SIGNIFICANCE AND IMPACT OF THE STUDY: The presence of archaeal 16S rDNA sequences in temperate estuarine sediments emerges as a valuable contribution to the understanding of the complexity of the ecosystem.     

Subcanopy gaps in temperate and tropical forests

Abstract We present a model of gaps in the vertical structure of forest vegetation. The traditional model of a forest gap assumes the existence of a ‘hole’ in the uppermost canopy layer, often extending down to near the ground. The present model extends the concept to gaps at any level, including those in lower layers below an intact canopy or subcanopy. It assumes that gaps at any level represent spaces with unused resources, especially favourable for plant growth and survival. Evidence from temperate and tropical forests indicates that gaps in the subcanopy and understorey layers below intact canopies are common, and that plants have higher growth rates in them than in non-gap sites. We also extend this model to below-ground gaps in the root zone.     

Structure and pattern in temperate seasonal forests

Demography, spatial pattern, and diversity of canopy and subcanopy trees, shrubs, and lianas were compared in two cool and two warm temperate North American forests, paired at 30° and 40° north latitudes. All woody stems 1 cm dbh in 16 randomly located, non-contiguous plots totalling 1 ha at each of the four sites were measured, mapped, and identified. Basal area and overall density did not differ between latitudes. Demographic and spatial analyses revealed remarkable similarity in spatial dispersion, irrespective of density or species composition. At all sites, dispersion of canopy trees was random but all understory stems were uniformly distributed relative to all canopy trees. Species diversity and vertical structure differed between the warm and cool temperate sites, especially in species composition of individual strata. Associations of understory species relative to canopy species were more random at 30° than at 40° north, where a higher degree of association between canopy and understory species' patterns, coupled with their size class distributions, suggested more lengthy regeneration cycles and an alternation of species assemblages. The forests at 30°, those subject to periodic canopy disturbance by hurricanes, had more vertical mixing of species (i.e., canopy species represented in all size classes), more tree saplings, and significantly more shrub and liana species.     

The bioclimate in temperate and northern cities

Climate is a basic component of the human environment. Developments in building design and indoor climate control have contributed greatly to improving human health and comfort. By contrast, the possibilities for improving urban climatic conditions by deliberate planning have been poorly exploited. The structure and processes of the urban atmosphere in extratropical regions are briefly described. The impact of certain selected urban climates on human health is summarized. The need for relevant bioclimatological design tools for applications in urban planning is stressed, followed by a brief review of some recent work on human thermal comfort. It is argued that the modification of present day comfort criteria to reflect human adaptation to climate may be important for further improvements of indoor climate, as well as for deducing the emissions of air pollutants and greenhouse gases.     

Linking energetics and overwintering in temperate insects

Overwintering insects cannot feed, and energy they take into winter must therefore fuel energy demands during autumn, overwintering, warm periods prior to resumption of development in spring, and subsequent activity. Insects primarily consume lipids during winter, but may also use carbohydrate and proteins as fuel. Because they are ectotherms, the metabolic rate of insects is temperature-dependent, and the curvilinear nature of the metabolic rate-temperature relationship means that warm temperatures are disproportionately important to overwinter energy use. This energy use may be reduced physiologically, by reducing the slope or elevation of the metabolic rate-temperature relationship, or because of threshold changes, such as metabolic suppression upon freezing. Insects may also choose microhabitats or life history stages that reduce the impact of overwinter energy drain. There is considerable capacity for overwinter energy drain to affect insect survival and performance both directly (via starvation) or indirectly (for example, through a trade-off with cryoprotection), but this has not been well-explored. Likewise, the impact of overwinter energy drain on growing-season performance is not well understood. I conclude that overwinter energetics provides a useful lens through which to link physiology and ecology and winter and summer in studies of insect responses to their environment.     

Brood reduction in temperate and sub-tropical ospreys

Summary In an effort to understand patterns and causes of nestling loss in Ospreys (Pandion haliaetus), I studied brood reduction in three eastern U.S. Osprey colonies during 1978 and 1979. The colonies, located in Florida Bay (1) and on coastal Long Island, N.Y. (2), differed in the average daily amount of food delivered to nestlings; Florida nests received 43% and 11% less fish per day than nests in the two N.Y. colonies, largely because latitude and season restricted day length and thus foraging time for the winter-breeding Florida Ospreys. Increased distance from stable food sources accounted for the lower rate of feeding at one of the N.Y. colonies. Variation in clutch size in the three colonies reflected differences in latitude more than in food availability; average clutch sizes in Long Island were larger than Florida clutches by 0.5 of an egg, but were similar to each other and to those in other northeastern U.S. Osprey populations.Increased nestling loss coincided with reduced food delivery rates and, in food stressed colonies, this loss was 2–3 times greater than any recorded for Ospreys. Starvation was the primary cause of nestling death, with mortality concentrated on third chicks, which hatched on average 3.9 d later and from eggs 5.6% smaller than chicks hatching first. Sibling aggression accounted for the preferential feeding of older nestmates,but only in colonies or nests where food was limited. Aggressive chicks nearly always stopped fighting after being fed. This behavior provided a reversible mechanism for controling brood reduction that was based on nutrition. Growth rates of young measured during the first half of the growth period were more variable between colonies than within nests. This is interpreted as reflecting both the differences in colony food delivery rates as well as the evolutionary pressures of sibling competition to equalize the growth of nestmates.     

Nitrogen cycling in tropical and temperate savannas

Savannas are the most common vegetation type in the tropics and subtropics, ranging in physiognomy from grasslands with scattered woody plants to woodlands with heterogeneous grass cover. Productivity and organic matter turnover in savannas are controlled by interactions between water and nutrient availability, and this basic environmental structure is modified by fire frequency and land management practices. We compared temperate and tropical savannas in order to understand the strength of nitrogen (N) limitation of productivity. American tropical and temperate savannas are N limited systems, and the N cycle differs according to the woody plant density, fire frequency, land use change, N deposition and N fixation. Grazing and conversion to pasture have been the predominant land-use changes in most savannas. In the Cerrado and the Llanos tropical savannas, intensified use of fire for pasture management is leading to decreased woody plant density. Oppositely, in the Chaco and North American temperate savannas, fire suppression and grazing are leading to increases in woody density. In addition, the higher soil P availability in the Gran Chaco and the higher N deposition in North American savannas may be contributing to increases of N cycling and net productivity rates. Some aspects of the N budget for savannas of the American continent are still unclear and require further analysis to determine rates of N fixation, and to understand how spatial and temporal soil heterogeneity control N fluxes through soil solution and into streams.     

Home heating in temperate Australia

Background, aim, and scope  

Home heating is an important component of life in inland temperate Australia, and firewood remains a common and relatively inexpensive fuel. However, supplies of firewood are becoming scarce, and excessive smoke pollution is becoming a problem in some places, partly due to poor management of fires. The alternative energy sources are electricity and gas, and the aim of this study is to compare the relative merits of these three energy sources for their impacts on the physical environment.     

Lactate dehydrogenases in Antarctic and temperate fish species

1. The kinetics of lactate dehydrogenase (both forward and back reaction) in cardiac and skeletal muscle of an Antarctic teleost have been compared with a temperate teleost of comparable morphology and ecology. 2. In both species the forward reaction (pyruvate to lactate) is maximally activated at 2.5-4 mM pyruvate and inhibited above this level. 3. The Michaelis constant (Km) for pyruvate is not significantly different between muscle types or between species when measured at their normal environmental temperature. 4. Km for pyruvate varies with temperature in a positive direction. 5. The back reaction (lactate to pyruvate) is maximally activated by 12-16 mM lactate but only in skeletal muscle of the antarctic species is there inhibition above this level. 6. The Km for lactate is significantly (P less than 0.05) lower in the Antarctic fish cardiac muscle. 7. While the two species are morphologically and ecologically similar, differences at the biochemical level are discussed with respect to environmental temperature range and conservation of enzymic characteristics.     

Naphthalene biodegradation in temperate and arctic marine microcosms

Naphthalene, the smallest polycyclic aromatic hydrocarbon (PAH), is found in abundance in crude oil, its major source in marine environments. PAH removal occurs via biodegradation, a key process determining their fate in the sea. Adequate estimation of PAH biodegradation rates is essential for environmental risk assessment and response planning using numerical models such as the oil spill contingency and response (OSCAR) model. Using naphthalene as a model compound, biodegradation rate, temperature response and bacterial community composition of seawaters from two climatically different areas (North Sea and Arctic Ocean) were studied and compared. Naphthalene degradation was followed by measuring oxygen consumption in closed bottles using the OxiTop^® system. Microbial communities of untreated and naphthalene exposed samples were analysed by polymerase chain reaction denaturing gradient gel electrophoresis (PCR–DGGE) and pyrosequencing. Three times higher naphthalene degradation rate coefficients were observed in arctic seawater samples compared to temperate, at all incubation temperatures. Rate coefficients at in situ temperatures were however, similar (0.048 day^?1 for temperate and 0.068 day^?1 for arctic). Naphthalene biodegradation rates decreased with similar Q₁₀ ratios (3.3 and 3.5) in both seawaters. Using the temperature compensation method implemented in the OSCAR model, Q₁₀ = 2, biodegradation in arctic seawater was underestimated when calculated from the measured temperate k₁ value, showing that temperature difference alone could not predict biodegradation rates adequately. Temperate and arctic untreated seawater communities were different as revealed by pyrosequencing. Geographic origin of seawater affected the community composition of exposed samples.     

Photosynthesis-irradiance relationships in polar and temperate phytoplankton populations

Summary Analyses of some 700 photosynthesis-irradiance (P-I) experiments made on natural marine phytoplankton assemblages in over six years of field work are summarized. Observed variations in P-I parameters are discussed in relation to geographical location, sample depth and temporal cycles (diel to interannual). Results suggest that P-I characteristics and therefore regional primary production are largely under physical control; temperature and light appear to be the most important environmental covariables.     

Exogonadal oogenesis in a temperate holothurian

Unusual structures were detected on the visceral peritoneum of the ovarian tubules in about 5%-10% of female sea cucumbers (Cucumaria frondosa) collected off Newfoundland, eastern Canada. The condition varied from mild to severe, with localized castration observed in the most heavily affected tubule sections. Investigation of the structures using histology, transmission electron microscopy (TEM), and gene analysis revealed that they were oocytes at different stages of development, growing singly or in groups of up to six. Their size and composition were consistent with those of oocytes found in the lumen of the ovaries, although "exogonadal" oocytes were devoid of a vitelline coat and presented few cortical granules. TEM sections suggest that the atypical oocytes emerged from the peritoneum and grew toward the coelomic cavity, and that they were not in direct contact with the basal lamina or the inner germinal layers. Similar masses have been observed in C. frondosa from the Gulf of St. Lawrence (Québec, Canada) and the Barents Sea (Russia), and in C. japonica from Russia and Psolus fabricii from Canada. The possibility that exogonadal oogenesis is attributable to anthropogenic disturbances should be investigated even though some of the affected specimens originate from presumably pristine locations.     

Algal nitrogen fixation in temperate regions

Summary A review of the few earlier investigations of nitrogen fixation by blue-green algae in temperate soils is presented. The extent of fixation by free-living algae in soil at three locations near Uppsala is discussed and compared with fixation by symbiotic algae living as phycobionts or cephalodia in lichens.