Annual survival of adult Atlantic Puffins Fratercula arctica is positively correlated with Herring Clupea harengus availability

Atlantic Herring is a keystone species in several marine ecosystems, supporting intensive fisheries as well as many predators including seabirds. Biomass of this stock in eastern North America has declined considerably in recent years, potentially putting at risk populations of its predators. Although adult survival in seabirds is considered robust to moderate changes in food availability, it is also the life‐history component most critical to sustaining populations of long‐lived birds. To investigate the possibility that Atlantic Puffin survival has been affected by reduced abundance of its main prey, we analysed the encounter histories of 2999 Atlantic Puffins ringed on Machias Seal Island to estimate annual adult survival for the years 1999–2011 and assess trends in survival and the effects of several biological and environmental covariates. Features of Puffin biology and resighting procedures likely to introduce heterogeneity into our resighting probabilities were accounted for and models of survival were assessed using standard methods. We used the variance components procedure in Program MARK and survival estimates from a time‐varying model to estimate the process variance (biological variation in survival) accounted for by suspected covariates of survival. Two proxies of food availability each explained more than half of the variation in annual survival: fishery landings of Atlantic Herring (52%) and per cent (by mass) of 1‐group Herring in the diet of Puffin chicks (51%). In addition to these proxies, May sea‐surface temperature accounted for 37% of variance in survival, but winter values of North Atlantic Oscillation showed no effect. Of those parameters of Puffin biology examined, chick growth rate explained 19% of the process variance in annual survival; laying date, fledging condition and fledging date all explained no variance. A decline in fishery landings of Herring since the early 1990s, and a concurrent decline in adult Puffin survival, reinforces concern for the health of the population of Herring, a keystone forage fish in this region, and of the community of marine predators in the Gulf of Maine that rely on Herring for their survival and reproduction.     

Effects of food restriction across stages of juvenile and early adult development on body weight,survival and adult life history

Organisms have to allocate limited resources among multiple life‐history traits, which can result in physiological trade‐offs, and variation in environmental conditions experienced during ontogeny can influence reproduction later in life. Food restriction may lead to an adaptive reallocation of the limited resources among traits as a phenotypically plastic adjustment, or it can act as an overall constraint with detrimental effects throughout reproductive life. In this study, we investigated experimentally the effects of food restriction during different stages of the juvenile and early adult development on body weight, survival and reproductive success in females and males of the European earwig Forficula auricularia. Individuals either received limited or unlimited access to food across three different stages of development (fully crossed) allowing us to identify sensitive periods during development and to test both additive and interactive effects of food limitation across stages on development and reproduction. Food restriction during the early and late juvenile stage had additive negative effects on juvenile survival and adult body weight. With regard to reproductive success of females which produce up to two clutches in their lifetime, restriction specifically in the late juvenile stage led to smaller first and second clutch size, lower probability of second clutch production and reduced hatching success in the second clutch. Reproductive success of females was not significantly affected when their male mates experienced food restriction during their development. Our findings in general support the ‘silver‐spoon’ hypothesis in that food restriction during juvenile development poses constraints on development and reproduction throughout life.     

The non-lethal effects of predators and the influence of food availability on life history of adult Chironomus tentans (Diptera: Chironomidae)

1. We used a laboratory experiment to determine effects of a predator (other than straightforward prey consumption) and food availability, during the larval stage, on adult size, age at emergence and fecundity of Chironomus tentans. 2. Predator presence and decreased food availability resulted in reduced adult emergence. 3. Predator presence and food availability resulted in smaller size and greater age at emergence of male and female chironomids. There were no significant interactions between effects of predator presence and food availability. 4. Predator presence had no significant effect on fecundity. 5. Smaller size and greater age at emergence can have important implications for adult survival, size and age at first reproduction and, thus, intrinsic rate of population growth.     

Evolution of a primary consumer in response to low and high food availability shapes life history traits and population demography

Hydrobiologia - To test the hypotheses that individuals of rotifers adapted to high food levels are smaller at maturity than those adapted to low food levels, and that selection history has...     

Horned larks on the Tibetan Plateau adjust the breeding strategy according to the seasonal changes in the risk of nest predation and food availability

Songbirds in seasonal environments often adjust their breeding strategy according to spatial or temporal changes in breeding conditions. Here we investigate how horned larks Eremophila alpestris, a multi‐brooded songbird on the Tibetan Plateau, responded to the changing risk of nest predation and food availability across breeding attempts. We showed that both nest concealment and food supply increased with plant growth, and horned larks adjusted their breeding strategies accordingly. First they selected nest‐sites where predator density was low, which enhanced nest survival. Second, clutch size increased with improving breeding conditions. They did not adopt an ‘egg‐size’ strategy as egg size did not change with laying sequence or breeding attempt. Instead, they adopted the ‘brood survival (feeding later‐hatched nestlings more)’ and ‘brood reduction (feeding early‐hatched nestlings more)’ strategies during early and later attempts. Moreover, nestlings’ growth varied with breeding attempt: more energy was invested into the growth of body mass during the first attempt but more energy was expended on the growth of linear structures during later attempts. This difference in energy allocation reflected changing food availability. We suggest that temporal changes of environmental factors are also the important force driving the evolution of avian breeding strategies.     

Coping with an unpredictable and stressful environment: the life history and metabolic response to variable food and host availability in a polyphagous tephritid fly

The way energy resources are used under variable environmental conditions lies at the heart of our understanding of resource management and opportunism in many organisms. Here we sought to determine how a time-limited, synovigenic and polyphagous insect with a high reproductive-potential (Anastrephaludens), copes behaviourally and metabolically with environmental unpredictability represented by constant and variable regimes of host availability and variation in food quality. We hypothesized that an adaptive response to a windfall of nutritious food would be the rapid accumulation of energy metabolites (whole body lipids, glycogen and proteins) in the female. We also studied patterns of oogenesis as an indicator of egg-reabsorption under stressful environmental conditions. As predicted, patterns of energy metabolites were mainly driven by the quality and temporal pattern of food availability. In contrast, patterns of host availability had a lower impact upon metabolites. When given constant access to high quality nutrients, after an initial increase early in life, whole body lipids and glycogen were regulated downward to a steady-state level and somatic protein levels did not vary. In contrast, when food uncertainty was introduced, whole body lipid, glycogen and protein oscillated sharply with peaks associated with pulses of high-quality food. Production of eggs was highest when offered continuous access to hosts and high quality food. Importantly, females fully recovered their reproductive capacity when fruit became available following a period of host deprivation. With no evidence of egg resorption and high levels of egg dumping, it appears that egg dumping may favour the continuous production of eggs such that the female’s reproductive tissues are ready to respond to rapid changes in the availability of hosts. Our results exemplify the capacity of insects to maximize reproduction under variable and stressful environmental conditions.     

Latitudinal trends in adult body size of Dolly Varden, with special reference to the food availability hypothesis

The food availability hypothesis (FAH) predicts that the relative productivity of ocean and freshwater habitats changes with latitude, and that anadromy will evolve when ocean productivity is greater than that in neighboring freshwater habitats, or vice versa. In data sets for the anadromous salmonid species Salvelinus malma, we show that the relative body size at maturity of anadromous populations is much larger in the northern limits of their ranges than that of fluvial populations, and, conversely, that of fluvial populations is slightly smaller at the southern limits than that of anadromous populations, supporting the FAH for the evolution of migration behavior in salmonids. Received: October 4, 2001 / Accepted: January 7, 2002     

From breeding pairs to fox towns: the social organisation of arctic fox populations with stable and fluctuating availability of food

Food availability can impact group formation in Carnivora. Specifically, it has been suggested that temporal variation in food availability may allow a breeding pair to tolerate additional adults in their territory at times when food abundance is high. We investigate group occurrence and intraspecific tolerance during breeding in a socially flexible canid, the arctic fox (Vulpes lagopus). We compare Iceland and Sweden where resource conditions differ considerably. A breeding pair was the most common social unit in both populations, but as predicted, groups were more frequent where food abundance varied substantially between years (Sweden: 6 %) than where food availability was stable (Iceland: ≤2 %). Within Sweden, supplemental feeding increased group occurrence from 6 to 21 %, but there was no effect of natural variation in lemming (Lemmus lemmus) availability since group formation was rare also at lemming highs. Thus, additional factors appeared to influence the trade-off between intraspecific territoriality and tolerance. We report two cases where related females showed enduring social relationships with good-neighbour strategies. Related females also engaged in alloparental behaviour in a ‘fox town’ with 31 foxes (4 adults, 3 litters). In contrast, when unrelated foxes bred close to each other, they moved or split their litters during summer, presumably because of territorial conflict. We suggest that fluctuating food availability is linked to group formation in this Arctic carnivore, but also when food availability increases, additional factors such as relatedness, alloparental benefits, competition and predator defence appear necessary to explain group formation.     

Thermal performance of squamate embryos with respect to climate,adult life history,and phylogeny

Reptiles are important model systems for examining the effect of temperature during development on the phenotype of individuals after hatching or birth. To assess whether squamate embryos exhibit adaptive variation in thermal biology, we derived three parameters: an index of developmental rate (DRI), the upper thermal limit for successful incubation, and the lower thermal limit for development for 28 species of lizard and 12 species of snake. The associations between developmental parameters and climatic and life‐history variables were examined using both conventional statistics and phylogenetically controlled analyses. Residual DRI (i.e. DRI corrected for stage at oviposition and hatchling mass) was strongly associated with phylogenetic relationship. By contrast, the upper limit for development was negatively related to the amount of precipitation during the warmest quarter of the year, and the lower thermal limit for development was positively related to temperature during the warmest quarter of the year and the activity body temperatures of adults. These latter observations indicate that embryonic thermal physiology is adapted to large‐scale environmental patterns, and that global climate change will impact embryonic development directly through impacts on nest temperature per se, as well as indirectly through impacts on the ability of gravid females to select suitable nest sites. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.     

Age‐specific maternal effects interact with larval food supply to modulate life history in Coleomegilla maculata

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Comparative life history of aspidiaceous ferns in northern Japan with reference to fertility during sporophyte development in relation to habitats

The life-cycle characteristics of ferns, in particular reproductive characteristics in relation to alternation of generations, have been studied in populations of 19 species of aspidiaceous ferns native to Hokkaido. The developmental age of the sporophyte was quantitatively expressed by the number of midrib branches of the leaf (NV; number of venation). The maximum developmental age (MNV) of the aspidiaceous ferns in Hokkaido ranged from 49 to 113. The initiation of fertility (IF) in the relative developmental age (RDA), percentages of any NV to the maximum NV of the leaf population) ranged from 15 to 65%. Ferns occurring on rocky cliffs initiated fertility at 15–21%, while ferns occurring on the forest floor initiated fertility at 41–65% in the RDA of a leaf population. Further observations were undertaken on 26 ferns of other families and revealed that there were correlations between habitat and maximum NV, and habitat and IF in the RDA. Ferns occurring on cliffs, on mossy rocks and on tree trunks, had lower maximum NV of the leaf and earlier initiation of fertility in the RDA, than those of ferns occurring on the forest floor, edge of forests and on grassland in Hokkaido. Ferns occurring in the exposed habitat seemed to behave as a r-strategist, while ferns occurring in the forest floor seemed to behave as a K-strategist.     

Comparison of the life history strategies of three Dysdercus true bugs (Heteroptera: Pyrrhocoridae), with special reference to their seasonal host plant use

The life history strategy and seasonal host plant use of three Dysdercus bugs (D. cingulatus, D. poecilus and D. decussatus) were compared based on 2 years of twice monthly observations on Ishigaki‐jima Island (24°N, 124°E) in the southernmost part of Japan. Dysdercus poecilus reproduced almost year round, exclusively on Sida rhombifolia, which bears fruit and/or seeds almost year round. Dysdercus cingulatus reproduced successively on various malvaceous and bombacaceous plant species, according to their seasonal fruiting cycles. Its robust reproduction was observed on Hibiscus makinoi during winter months and on Chorisia speciosa and Bombax ceiba in early summer, whereas small‐scale reproduction was observed on various malvaceous plant species during the summer and autumn months. Dysdercus decussatus reproduced on Hibiscus tiliaceus and Thespesia populnea during the summer months, when these host plants bear abundant fruit and/or seeds, and its adults formed conspicuous aggregations without copulation on the underside of the leaves of those plants from November to the subsequent May. Each Dysdercus species showed a species‐specific life history strategy according to the differences in the phenology of their host plants.     

Trophic links,nutrient fluxes,and natural history in the Allium ursinum food web,with particular reference to life history traits of two hoverfly herbivores (Diptera: Syrphidae)

The food web centering on Allium ursinum (Liliaceae) in a beech forest (Germany) is described, and temporal variation of active trophic links is related to species' life cycles. The most important insect herbivores are Cheilosia fasciata (a larval leaf miner) and Portevinia maculata (a larva bulb miner) (Diptera: Syrphidae). Energy, carbon and nitrogen flow in the food chain (Allium-Cheilosia-Phygadeuon ursini) are investigated and analysed with respect to differences in resource allocation by the leaf miner and its hymenoptereous parasitoid. In C. fasciata nitrogen is likely to be the limiting resource, while growth in Phygadeuon ursini appears energy-limited. Larval feeding habits of C. fasciata and Portevinia maculata determined the timing of the species' life cycles and, as a consequence, appeared to preclude the existence of a pupal parasitoid in Portevinia maculata. Further details of life history traits are demonstrated and discussed.