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Among birds, several body composition traits typically decrease in size or mass during breeding likely as a result of competing demands during this critical life history stage. However, a recent outdoor captive study in an Arctic-breeding cold-specialist songbird (snow buntings - Plectrophenax nivalis) demonstrated that these birds maintain winter cold acclimatization during the spring and summer, despite facing summer temperatures much warmer than on their Arctic breeding grounds. This suggests that buntings may face a cumulative physiological cost during breeding: having to support a winter phenotype while also upregulating additional traits for reproduction. The current study aimed to test this hypothesis. Between 2016 and 2019, we examined how body composition and metabolic performance (thermogenic capacity and physiological maintenance costs) changed from prebreeding to chick provisioning in free-living birds captured at the northern limit of their breeding range in the Canadian Arctic (Alert, NU, 82°). While body mass and fat reserves deceased significantly between pre-breeding and territory defense independent of thermal conditions, cold endurance and associated traits remained stable and elevated up to the nestling provisioning period, as long as ambient temperature remained below a threshold level of 0-2°C. These results indicate that snow buntings must maintain a high thermogenic capacity after arrival on the breeding grounds if temperatures remain below freezing, regardless of whether birds are actively breeding or not. In this context, our research suggests that these birds, and possibly other arctic breeding songbirds, may experience cumulative physiological costs during years with a late onset of spring, when breeding activities (i.e., egg production and incubation) begin while temperatures are still below 0-2°C. [ABSTRACT FROM AUTHOR]

Sturgeons are a unique group of species that were historically widespread across the northern hemisphere. According to the latest IUCN Red list assessment, more than 80% of the species globally are threatened with extinction, making it essential to identify the life stages at which they are suffering from impacts the most, while at the same time to compare among river systems and populations based on standardized assessment techniques. All sturgeon have similar but not identical, life-history strategies. Therefore, monitoring techniques developed for one sturgeon species would be applicable to most other species. Monitoring can be conducted at each life stage. However, while each life stage will provide different information about the population, not all will necessarily help to assess population trend or status. Life stages that are highly variable prove to be less quantifiable even after expending very high effort. Collectively, these assessments could be very informative on population status, limitations, and trends. However, monitoring at each stage is time-consuming and expensive. Clearly defined objectives are therefore required when embarking on an assessment program. The objective of this study was to review the assessment techniques used for the different life stages including eggs, drifting larvae, age-0, juveniles, subadults, and adults to provide a common basis for population assessments that can be standardized to some extent and thus facilitate comparisons between the results obtained. For this purpose, this review presented the most common assessment techniques for each life stage, assessed the pros and cons of assessing each life stage, and examined if the methodology was qualitative or quantitative to assist in establishing long-term monitoring initiatives. [ABSTRACT FROM AUTHOR]

Among birds, several body composition traits typically decrease in size or mass during breeding likely as a result of competing demands during this critical life history stage. However, a recent outdoor captive study in an Arctic-breeding cold-specialist songbird (snow buntings – Plectrophenax nivalis) demonstrated that these birds maintain winter cold acclimatization during the spring and summer, despite facing summer temperatures much warmer than on their Arctic breeding grounds. This suggests that buntings may face a cumulative physiological cost during breeding: having to support a winter phenotype while also upregulating additional traits for reproduction. The current study aimed to test this hypothesis. Between 2016 and 2019, we examined how body composition and metabolic performance (thermogenic capacity and physiological maintenance costs) changed from pre-breeding to chick provisioning in free-living birds captured at the northern limit of their breeding range in the Canadian Arctic (Alert, NU, 82°). While body mass and fat reserves deceased significantly between pre-breeding and territory defense independent of thermal conditions, cold endurance and associated traits remained stable and elevated up to the nestling provisioning period, as long as ambient temperature remained below a threshold level of 0–2°C. These results indicate that snow buntings must maintain a high thermogenic capacity after arrival on the breeding grounds if temperatures remain below freezing, regardless of whether birds are actively breeding or not. In this context, our research suggests that these birds, and possibly other arctic breeding songbirds, may experience cumulative physiological costs during years with a late onset of spring, when breeding activities (i.e., egg production and incubation) begin while temperatures are still below 0–2°C.

Understanding how natural selection drives diversification in nature has been at the forefront of biological research for over a century. The main idea is simple: natural selection favours individuals best suited to pass on their genes. However, the journey from birth to reproduction is complex as organisms experience multiple developmental stages, each influenced by genetic and environmental factors (Orr, 2009). These complexities compound even further as each stage of development might be governed by a unique underlying set of alleles and genes. In this issue of Molecular Ecology, Goebl et al. (2022) examine the role of natural selection in driving ecotypic divergence across different life history stages of the prairie sunflower Helianthus petiolaris. The authors used reciprocal transplant experiments, demographic models, and genomic sequencing to explore fitness variation across developmental stages. They show how natural selection impacts population divergence across multiple life history stages and evaluate the resulting allele frequency changes. Goebl et al. link these results to the role of chromosomal inversions, thus furthering our understanding of how ecological divergence proceeds in the face of gene flow. Below, we explore these results in detail and complement their interpretation by considering the evolution of genetic correlations amongst traits governing fitness. [ABSTRACT FROM AUTHOR]

This study deals with Ulnaria species found and described from two regions of China with large climate differences during the period of 2014-2022. The first region, located in the Wuling Mountains and Hunan province, has a subtropical climate and the second in Qinghai, a northwest province of China, has a highland continental climate which is characterized by a cold and long winter and warm, short summer. Previously there were nine new Ulnaria species published from the first region. This study describes 14 additional new Ulnaria taxa, nine of which were found in the first region and five of which were found in the second region. A key to the Ulnaria species that have been described from China is provided. The main morphological characteristics for 63 Ulnaria taxa are summarized in Appendices which allow the division of these Ulnaria taxa into three groups: the seven members of group one all possess both uniseriate striae and valve marginal spines, the 42 members of group two all possess uniseriate or mostly uniseriate striae but without the valve marginal spines, and the 14 members of group three all possess mostly biseriate striae and without valve marginal spines. To summarize the morphological characters of the published Ulnaria taxa and 14 taxa described in this study several conclusions for the characterization of Ulnaria are drawn: 1) each cell has two valve-appressed, long plate-like plastids; 2) living cells of many Ulnaria species often lie in girdle view on a slide because they have deep mantles and some copulae associated with either the epivalve or the hypovalve so that the cell depth is often larger than the valve width; 3) the basic structures forming a valve include sternum, virgae, and vimines/viminules; 4) the valvocopula is a closed hoop which has a similar ultrastructure in all Ulnaria taxa but differs from the other copulae in structure; 5) the configuration of girdle bands is a common condition; 6) the life history of Ulnaria can be divided into the four series of successive stages: auxospore, initial cell, pre-normal vegetative cell, and normal vegetative cell, which is very similar to the life history of Hannaea inaequidentata (Lagerstedt) Genkal and Kharitonov; 7) the closed valvocopula is proposed as a definition character for the genus Ulnaria because demonstrating all girdle bands closed is impracticable. [ABSTRACT FROM AUTHOR]

In this study, the dominant mechanism that defines the species assembly in an old‐growth temperate forest was investigated by analyzing the species specificity of demographic parameters in relation to the life history stage, testing the hypotheses that early life stages should be more critical for sub‐canopy species than canopy species. Data for 17 major tree species in the Ogawa Forest Reserve (OFR) in Japan were analyzed, together with data from early stages (seed production, seed dispersal, and seedling emergence) to dbh‐based transition probability and survival stages (5–80 cm). Both datasets were subjected to principal components analysis (PCA): one included tree of dbh < 35 cm for all species (small‐sized trees of all species [SSAS]) and the other included tree species with dbh ≥ 55 cm (large‐sized species [LSS]). The most influential was the growth–survival trade‐off for trees at small‐to‐middle‐sized stages (dbh: 10–40 cm), which captured a moderate proportion of the demographic variation (24.3%–26.4%). At these stages, some Quercus species were characterized by higher growth, and some Fagus and Acer species by shade tolerance. Behavior during early‐to‐late life stages was the second most important dimension, for SSAS, sub‐canopy tree species showed high survival at early life stages than canopy species as the second important dimension, which differed between the SSAS‐ and LSS‐based PCAs. The relationship between functional traits and PCA axis dimensions varied with PCA type and dimension. The growth–survival trade‐off in the OFR was closely associated with maximum tree height, a proxy for life form, and specific leaf area a proxy for shade tolerance. This finding implies a significant role for the growth–survival trade‐off in stable species coexistence by maintaining mutual claims to vertical light resources and allowing the more efficient use of the forest canopy space. However, there was no significant association between wood density and demographic variables. Our study shows that interspecies relationships vary with the life history stage and that early life stages are more critical for sub‐canopy species than canopy species in temperate forests, where the entire life history of the trees must be considered focusing on the difference in life forms. [ABSTRACT FROM AUTHOR]

Abstract In this study, the dominant mechanism that defines the species assembly in an old‐growth temperate forest was investigated by analyzing the species specificity of demographic parameters in relation to the life history stage, testing the hypotheses that early life stages should be more critical for sub‐canopy species than canopy species. Data for 17 major tree species in the Ogawa Forest Reserve (OFR) in Japan were analyzed, together with data from early stages (seed production, seed dispersal, and seedling emergence) to dbh‐based transition probability and survival stages (5–80 cm). Both datasets were subjected to principal components analysis (PCA): one included tree of dbh

Biological steroids were traditionally thought to be synthesized exclusively by the adrenal glands and gonads. Recent decades have seen the discovery of neurosteroid production that acts locally within the central nervous system to affect physiology and behavior. These actions include, for example, regulation of aggressive behavior, such as territoriality, and locomotor movement associated with migration. Important questions then arose as to how and why neurosteroid production evolved and why similar steroids of peripheral origin do not always fulfill these central roles? Investigations of free-living vertebrates suggest that synthesis and action of bioactive steroids within the brain may have evolved to regulate expression of specific behavior in different life history stages. Synthesis and secretion of these hormones from peripheral glands is broadcast throughout the organism via the blood stream. While widespread, general actions of steroids released into the blood might be relevant for regulation of morphological, physiological, and behavioral traits in one life history stage, such hormonal release may not be appropriate in other stages. Specific and localized production of bioactive steroids in the brain, but not released into the periphery, could be a way to avoid such conflicts. Two examples are highlighted. First, we compare the control of territorial aggression of songbirds in the breeding season under the influence of gonadal steroids with autumnal (non-breeding) territoriality regulated by sex steroid production in the brain either from circulating precursors such as dehydroepiandrosterone or local central production of sex steroids de novo from cholesterol. Second, we outline the production of 7α-hydroxypregnenolone within the brain that appears to affect locomotor behavior in several contexts. Local production of these steroids in the brain may provide specific regulation of behavioral traits throughout the year and independently of life history stage.

Exploring the variation in functional traits in plants from different perspectives not only helps reveal the adaptation of plants to their environment but also reflects the ecological strategies of plants. In this study, three species of arbuscular mycorrhizal (AM) trees and three species of ectomycorrhizal (EM) trees were selected in the Heilongjiang Liangshui National Nature Reserve. To investigate the similarities and differences between the functional traits of the two mycorrhizal types of trees at different life history stages, hydraulic traits, anatomical traits, leaf functional traits, and stoichiometry of each species were measured at different life history stages. Traits such as mean vessel area, hydraulic weighted vessel diameter and nitrogen content appeared to be relatively important traits in this study, and all traits were more strongly correlated in AM trees. The sapwood-specific hydraulic conductivity, leaf-specific hydraulic conductivity, vessel density, vessel lumen fraction, nitrogen content and phosphorus content of EM species were significantly higher than those of AM species, while the total vessel area, mean vessel area, hydraulic weighted vessel diameter and density of primary leaf veins of EM species were significantly lower than those of AM species. The leaf mass per area and leaf dry matter content of saplings were significantly lower than those of juvenile trees and adult trees. Most of the trait variation interspecific and intraspecific, and the variability of hydraulic and anatomical traits such as sapwood-specific hydraulic conductivity, leaf-specific hydraulic conductivity, vessel density and total vessel area was relatively large. Leaf dry matter content, hydraulic weighted vessel diameter, vessel density and the vessel lumen fraction contributed significantly to whole branch hydraulic conductivity. It is evident that plastic adjustment and synergistic variation in functional traits are important mechanisms by which plants with different mycorrhizal types and at different life history stages can adapt to different environments. • Trait variation occurs between and within specie. • All traits were more strongly correlated in arbuscular mycorrhiza species. • Ectomycorrhiza species tend to produce more and smaller vessels. • Arbuscular mycorrhiza species have a larger vessel area and fewer vessels overall [ABSTRACT FROM AUTHOR]

The sensitivity and response of climatic treelines in the Himalayas to climate change is still being debated. Regeneration of tree species in the treeline ecotone is considered a sensitivity indicator and thus of great scientific interest. The aim of this study is to detect predictor variables for regeneration densities of the major tree species in central Himalayan treeline ecotones (Abies spectabilis, Betula utilis, Rhododendron campanulatum), analysing five development stages from seedling to mature tree. We applied negative binomial generalized linear models with predictors selected from a wide range of soil, topography, climate and stand characteristic variables. We found considerably varying predictors across the tree species and their stages of development. Soil conditions, topography and climate, as well as competing and facilitating tree species, had high predictive power for population densities. These predictors were clearly species- and development stage-specific. Predictors' spatial- and development-specific heterogeneity induce a high degree of complexity and diversify any potentially linear response of tree population densities and treeline position to changing climatic conditions. [ABSTRACT FROM AUTHOR]

Natural secondary forest has a strong capacity to regrow naturally and recover biodiversity rapidly on abandoned lands. However, at the neighborhood scale, which can truly reflect the facilitative or competitive interactions among individual plants, the local diversity spatial structure in secondary forest and the feedback effects of neighborhood diversity on natural regeneration remain unclear, and this may be the key to properly understand the mechanisms of natural secondary forest species diversity recovery. To this end, this study established a dynamic plot in a rehabilitated secondary forest after disturbance and conducted a comprehensive survey of 68,336 individual plants with repeated measurements at 5-year interval to assess the characteristics of neighborhood diversity structure across life history stages and link the neighborhood species richness (NSR) effect translated by species interactions at species diversity structure with individual trees recruitment/mortality in secondary forest regeneration. The results showed that, compared with tropical and temperate natural forests, a higher proportion of diversity accumulators and a lower proportion of repellers in subtropical secondary forests resulted in neighborhood diversity structures characterized by heterospecific or high-diversity patches, which are beneficial to the maintenance or restoration of biodiversity. As an important supplement to the research on the relationship between diversity and productivity, our findings show a positive diversity–survival relationship in subtropical secondary forests. Importantly, we observed that the neighborhood diversity structure exhibited a trend of accumulator-dominated to neutral-dominant changes with life stage from sapling to adult, which, in turn, determined the direction and strength of NSR effects on recruitment/mortality. Specifically, diverse local neighborhoods at a later successional stage characterized with ‘neutral’ species–species interactions can act as a ‘welfare net’ by offering favorable microhabitats for the most vulnerable recruitments or saplings, i.e., the NSR effects that promoted individual recruitment/survival in our study. These results not only enrich our understanding of the biodiversity–productivity–survival relationship but also highlight the importance of retaining latesuccessional species of native trees in intensive forest production or in situ conservation policies. [ABSTRACT FROM AUTHOR]

Predicted shifts in mean and extreme temperatures associated with climate change can have variable impacts on organisms, and the sign and magnitude of these impacts may depend upon local context. For Hedophyllum sessile, a habitat-forming intertidal kelp, the impacts of warming may vary with local density and position in the intertidal zone. To assess the potential context-dependence of warming, we manipulated H. sessile densities across an intertidal gradient and experimentally imposed periodic thermal stress in the field. The recruitment of H. sessile juveniles was unimodally related to shore level, peaking near the center of the species’ vertical distribution and falling off at the upper and lower distributional limits. Experimental warming tended to have mildly positive effects on recruitment lower on the shore regardless of adult density, and in upper zone, high density plots. However, warming had strongly negative effects on recruitment in upper zone, low density plots. Temperature manipulations also had context-specific effects on adult plant growth; seasonal increases in blade number and canopy cover were slightly enhanced by warming in high-density plots but greatly reduced by warming in low-density plots. Finally, experimental heating had context-dependent effects on an understory herbivore, the chiton Katharina tunicata, which increased in abundance following heating in high density plots but decreased in low density plots. Our results demonstrate that extreme temperature events can affect multiple species and multiple life history stages, and that the impacts of such events can depend upon both environmental (e.g. intertidal height) and biological (e.g. adult density) context.

Phenological shifts are a widely studied consequence of climate change. Little is known, however, about certain critical phenological events, nor about mechanistic links between shifts in different life-history stages of the same organism. Among angiosperms, flowering times have been observed to advance with climate change, but, whether fruiting times shift as a direct consequence of shifting flowering times, or respond differently or not at all to climate change, is poorly understood. Yet, shifts in fruiting could alter species interactions, including by disrupting seed dispersal mutualisms. In the absence of long-term data on fruiting phenology, but given extensive data on flowering, we argue that an understanding of whether flowering and fruiting are tightly linked or respond independently to environmental change can significantly advance our understanding of how fruiting phenologies will respond to warming climates. Through a case study of biotically and abiotically dispersed plants, we present evidence for a potential functional link between the timing of flowering and fruiting. We then propose general mechanisms for how flowering and fruiting life history stages could be functionally linked or independently driven by external factors, and we use our case study species and phenological responses to distinguish among proposed mechanisms in a real-world framework. Finally, we identify research directions that could elucidate which of these mechanisms drive the timing between subsequent life stages. Understanding how fruiting phenology is altered by climate change is essential for all plant species but is particularly critical to sustaining the large numbers of plant species that rely on animal-mediated dispersal, as well as the animals that rely on fruit for sustenance.

Abstract Background Birds, across their annual cycle, progress through sequences of life-history stages such as reproduction and molt. The mechanisms that control annual avian itineraries involve endocrine responses triggered by seasonal environmental factors, including changes in resource availability and/or photoperiod. However, at equatorial latitudes birds are exposed to different degrees of seasonality, and the mechanisms underlying phenology of birds near the equator remain less explored. We studied the silver-beaked tanager, an endemic Amazonian songbird, from an equatorial lowland population. Remarkably, in this species, song behavior has been shown to be seasonally aligned to minimal changes in day length near the equator. Here, we aimed to further explore the phenology of silver-beaked tanagers by assessing shifts of food sources utilization as potential ultimate factors. We measured triple isotopic tracers of carbon (δ13C), nitrogen (δ15N) and sulphur (δ34S) in blood and feathers of birds throughout a whole year. In addition, we assessed the degree of seasonality in the molting activity, in relation to circulating levels of corticosterone, as well as to testosterone as a proxy of the reproductive condition of males. Results There was important seasonal variation of δ34S values in relation to rainfall patterns and changes in estuarine water composition. Despite the seasonal rainfall, we found no substantial variation in the foraging ecology of birds over seasons. This was accompanied by uniform levels of corticosterone throughout the year, probably associated with the absence of drastic seasonal resource shortages. Even so, silver-beaked tanagers showed a marked seasonal molting schedule, which was related to variation in the circulating levels of both corticosterone and testosterone. Conclusions These findings suggest that foraging niche is not life history stage-dependent in silver-beaked tanagers, and highlight rainfall as an important environmental cue for bird phenology. Our stable isotope results encourage further studies addressing the influence of estuarine water dynamics on bird timing. In addition, the results suggest a primary role of steroid hormones in regulating seasonal life history stages under the absence of a marked photoperiod. Contrary to what might be expected for a tropical songbird, our physiological data in silver-beaked tanagers do not support reproduction-molt overlapping.

Reported effects of inbreeding vary among taxa and may depend on a number of factors, including what trait is measured, temporal variability, parental effects, or life history stage. To understand the effects of inbreeding during early life history stages, we estimated the effects of individual-level heterozygosity on hatching success and first year survival in a Swedish population of sand lizards (Lacerta agilis) over a period of almost a decade, using over 4000 eggs, 400 clutches, and over 3000 juveniles. Heterozygosity had a positive effect on hatching success, in standardized laboratory conditions, but no effect on first year survival. Also, both of these measures of viability varied across the years of the study, demonstrating the importance of temporal heterogeneity in pre and post-hatching conditions. Finally, we identified both paternal and maternal identity effects on hatching success. Thus, we show that selection on heterozygosity was not consistent across developmental life stages, emphasizing the need of considering a number of ontogenic stages, as well as potential parental and environmental effects, when studying the effects of heterozygosity on viability in natural populations. [ABSTRACT FROM AUTHOR]

Biological steroids were traditionally thought to be synthesized exclusively by the adrenal glands and gonads. Recent decades have seen the discovery of neurosteroid production that acts locally within the central nervous system to affect physiology and behavior. These actions include, for example, regulation of aggressive behavior, such as territoriality, and locomotor movement associated with migration. Important questions then arose as to how and why neurosteroid production evolved and why similar steroids of peripheral origin do not always fulfill these central roles? Investigations of free-living vertebrates suggest that synthesis and action of bioactive steroids within the brain may have evolved to regulate expression of specific behavior in different life history stages. Synthesis and secretion of these hormones from peripheral glands is broadcast throughout the organism via the blood stream. While widespread, general actions of steroids released into the blood might be relevant for regulation of morphological, physiological, and behavioral traits in one life history stage, such hormonal release may not be appropriate in other stages. Specific and localized production of bioactive steroids in the brain, but not released into the periphery, could be a way to avoid such conflicts. Two examples are highlighted. First, we compare the control of territorial aggression of songbirds in the breeding season under the influence of gonadal steroids with autumnal (non-breeding) territoriality regulated by sex steroid production in the brain either from circulating precursors such as dehydroepiandrosterone or local central production of sex steroids de novo from cholesterol. Second, we outline the production of 7α-hydroxypregnenolone within the brain that appears to affect locomotor behavior in several contexts. Local production of these steroids in the brain may provide specific regulation of behavioral traits throughout the year and independently of life history stage.

Understanding how ecological networks are organised over the course of an organism’s lifetime is crucial for predicting the dynamics of interacting populations and communities across temporal scales. However, most studies so far considered only one life history stage at a time, such as adult, when studying networks of interacting species. Therefore, knowledge about how multiple life history stages affect the development and stability of plant–plant association networks is lacking. We measured the understory adult plant community and the soil seed bank across a plant age gradient of the nurse shrub Retama sphaerocarpa in an arid ecosystem in Spain. Using a multilayer network approach, we built adult understory–nurse and seed bank–nurse networks and analysed how network nestedness, species’ role, and species specificity varied between them and with nurse plant age. We found that seed bank and adult understory networks changed depending on nurse plant age in two different ways. With increasing nurse plant age, adult understory networks became significantly more nested than seed bank networks. The nested architecture of seed bank networks was therefore a poor predictor of adult understory network nestedness. The contribution and specificity of species to network nestedness increased with increasing nurse plant age more in the adult understory than in seed bank networks, despite high species turnover. Our data show that life history and ontogeny affect the development of plant–plant association networks. Niche construction and environmental filtering along nurse ontogeny seem pivotal mechanisms structuring adult understory networks while the assembly of seed bank networks seems rather stochastic. We highlight the importance of mature plant communities for maintaining rare species populations and supporting the stability of ecological communities through time. [ABSTRACT FROM AUTHOR]

As animals move through life history stages, energy requirements for each stage will vary. Both daily and annual variation in the glucocoriticoid hormones (specifically corticosterone, or CORT, in birds) helps provide the variable energy needed through life history stages. In many bird species, CORT is higher in the breeding season when energy demands can be quite high and is often lower in the non-breeding season. Additionally, CORT has a role to play in the response to stressful stimuli and the level to which CORT is elevated following stressful events can vary through the annual cycle as well. Here we report on baseline and stress-induced CORT levels in both sexes of northern cardinals, Cardinalis cardinalis , a non-migrating, year-round territorial species across life history stages. Corticosterone is overall higher in the non-breeding season than the breeding season in both sexes. Males tend to have higher levels of stress-induced CORT than females, although the observed patterns are complex. Our findings differ from one of the more common profile reported in songbirds where breeding season CORT tends to be higher than non-breeding levels. A strong influence may be the prolonged breeding season seen in cardinals; lower levels of CORT during breeding may guard against adverse maternal effects, interruptions in breeding behaviors, or egg production. Additional investigation of species with similar ecologies to northern cardinals, and more populations of cardinals, may show that annual glucocorticoid profiles are more labile than previously appreciated. [ABSTRACT FROM AUTHOR]

A better understanding of factors affecting population change is needed to explain declines of long-distance migrants. As juvenile survival is generally an important determinant of population dynamics, assessing whether juvenile survival is primarily affected either during the post-fledging stage on the natal site or during the migration and winter stages (migration-winter) is important for developing conservation strategies. Here, we assess variation in stage-dependent survival of juvenile Northern Wheatears ( Oenanthe oenanthe), a threatened passerine in northwestern Europe. We estimate apparent survival in a Dutch coastal breeding population based on frequent resightings during the whole breeding season. We show that post-fledging survival on the natal grounds was not clearly different from survival during migration-winter and that late fledging reduces survival during both post-fledging and migration-winter. It is unknown which factors are causal to lower survival of late-fledged juveniles and this hampers effective conservation. Meanwhile, conservation measures focusing on nest protection should increase average juvenile survival in the remaining small populations in the short term because the number of successfully fledged early juveniles should increase. [ABSTRACT FROM AUTHOR]

The divergence between most stock assessments and studies in marine ecology is characterized by the low priority usually given to assessing the holding capacity of marine habitats. Habitats of high structural complexity are relatively uncommon in shelf waters, are contagiously distributed, and are damaged incidentally by bottom-towed gear. Structurally complex habitats are used by many demersal fish and crustaceans for predation abatement and as a site for feeding forays. Successive life-history stages typically migrate through several structurally complex habitats which recent studies show often to have fractal properties. One consequence of fractal structures as cover is a rapid reduction of protection from predators with growth in size: migration is the only response possible when further growth of the recruiting age class renders individuals in that habitat vulnerable to predation. A common feature of structurally complex habitats with high vulnerability at size is the occurrence of population bottlenecks. It is suggested that identifying and rectifying shortages of structured habitat, and eliminating habitat bottlenecks, will be effective in stock enhancement. This will require placing strict spatial constraints on the operation of bottom gear. This paper reviews new methods of estimating juvenile predation mortality, including mortality-at-age and mortality-at-life-history stage, which depend on the fractal characteristics of structurally complex habitats. [ABSTRACT FROM AUTHOR]

Biological characteristics of 'Kunimasu' ( Oncorhynchus kawamurae), poorly known even before the species was prematurely believed extinct, have now become apparent following the examination of 59 specimens from Lake Saiko, Yamanashi Prefecture, Japan and comparison with 58 examples of 'Himemasu' (kokanee of Oncorhynchus nerka in Japan), also from Lake Saiko. Significant ( p < 0.01) differences between Kunimasu and Himemasu from Lake Saiko occurred in counts of anal-fin rays, pectoral-fin rays, gill rakers (no overlap found) and pyloric caeca. Secondary sexual characters related to maturity level were also found in Kunimasu, the body being more compressed in pre-spawning and spawning males and females than in immature and maturing individuals. Furthermore, maturing male Kunimasu and Himemasu also differed in body shape. Body coloration of Kunimasu also differed according to level of maturity, the nuptial coloration in both sexes being olive-green when alive and black when fresh. Dark dots, found in ca. 40 % of Kunimasu individuals examined, were less distinct than in Himemasu. The spawning season of Kunimasu extended through winter and early spring in Lake Saiko, with spawning males and females remaining near the bottom, compared with non-spawning individuals which occupied the upper and middle profundal zones in the daytime. [ABSTRACT FROM AUTHOR]