Assessing Short‐ and Long‐Term Repeatability and Stability of Personality in Captive Zebra Finches Using Longitudinal Data

Assessing behavioural consistency is crucial to understand the evolution of personality traits. In the present study, we examined the short‐ and long‐term repeatability and stability of two unrelated personality traits – exploratory tendencies and struggling rate – using captive female zebra finches ( Taeniopygia guttata). We performed two experimental sessions of behavioural tests with a 7‐mo interval, which represents up to one quarter of a zebra finch's life expectancy. We showed that, overall, exploratory tendencies and struggling rate were significantly repeatable in the short term. However, only exploratory tendencies were repeatable in the long term. We found interindividual differences in short‐term stability of exploratory tendencies, but not struggling rate, providing evidence for differences in intraindividual variability. In the long term, struggling rate significantly decreased between the two experimental sessions, whereas exploratory tendencies remained stable. Finally, the amount of interindividual variation measured at both sessions did not differ. Our results suggest that short‐ and long‐term repeatability and stability of personality may vary between individuals, depending on the behavioural trait under scrutiny. As a consequence, deducing personality from measures realized earlier in a subject's life should be performed with caution. We discuss the implications of inter‐ and intraindividual variation in personality consistency on individual fitness.     

Sex‐specific pathways of parental age effects on offspring lifetime reproductive success in a long‐lived seabird

The conditions under which individuals are reared vary and sensitivity of offspring to such variation is often sex‐dependent. Parental age is one important natal condition with consequences for aspects of offspring fitness, but reports are mostly limited to short‐term fitness consequences and do not take into account offspring sex. Here we used individual‐based data from a large colony of a long‐lived seabird, the common tern Sterna hirundo, to investigate longitudinal long‐term fitness consequences of parental age in relation to both offspring and parental sex. We found that recruited daughters from older mothers suffered from reduced annual reproductive success. Recruited sons from older fathers were found to suffer from reduced life span. Both effects translated to reductions in offspring lifetime reproductive success. Besides revealing novel sex‐specific pathways of transgenerational parental age effects on offspring fitness, which inspire studies of potential underlying mechanisms, our analyses show that reproductive senescence is only observed in the common tern when including transgenerational age effects. In general, our study shows that estimates of selective pressures underlying the evolution of senescence, as well as processes such as age‐dependent mate choice and sex allocation, will depend on whether causal transgenerational effects exist and are taken into account.     

Comparison between the life cycles of two Soleidae, the common sole, Solea solea, and the thickback sole, Microchirus variegatus, in the Bay of Biscay (France)

The life history of two Soleidae, the common sole, Solea solea, and the thickback sole, Microchirus variegatus, were compared in the Bay of Biscay in an attempt to set out factors which could explain settlement styles known to be different between juveniles of each species. Common sole juveniles had been shown to depend on coastal and estuarine nurseries, and the thickback sole to develop in open-sea nurseries, although the spawning grounds and spawning season of both species overlapped (offshore and at springtime, respectively). For this study, data on adult, juvenile and larva distributions were obtained from cruises carried out in the Bay of Biscay during the last decade. In addition, growth rate of larvae and planktonic interval duration, estimated by means of otolith increment analysis, were compared, as well as literature-derived information on behaviour of larvae. By comparing larval features, it appeared that thickback sole did not obtain the advantage of a slightly longer pelagic life span for an increased dispersal, due to an early shift to benthic behaviour. Other evidence was given by more specifically stated distributions that the further and deeper offshore spawning of M. variegatus, compared to S. solea, was a likely key-factor of the juvenile settlement process. This could explain why the thickback sole, contrary to the common sole, never reach coastal areas and thus settle offshore, in waters deeper than 30 m.     

Evidence of reduced individual heterogeneity in adult survival of long‐lived species

The canalization hypothesis postulates that the rate at which trait variation generates variation in the average individual fitness in a population determines how buffered traits are against environmental and genetic factors. The ranking of a species on the slow‐fast continuum – the covariation among life‐history traits describing species‐specific life cycles along a gradient going from a long life, slow maturity, and low annual reproductive output, to a short life, fast maturity, and high annual reproductive output – strongly correlates with the relative fitness impact of a given amount of variation in adult survival. Under the canalization hypothesis, long‐lived species are thus expected to display less individual heterogeneity in survival at the onset of adulthood, when reproductive values peak, than short‐lived species. We tested this life‐history prediction by analysing long‐term time series of individual‐based data in nine species of birds and mammals using capture‐recapture models. We found that individual heterogeneity in survival was higher in species with short‐generation time (< 3 years) than in species with long generation time (> 4 years). Our findings provide the first piece of empirical evidence for the canalization hypothesis at the individual level from the wild.     

Body mass and individual fitness in female ungulates: bigger is not always better

In female vertebrates, differences in fitness often correspond to differences in phenotypic quality, suggesting that larger females have greater fitness. Variation in individual fitness can result from variation in life span and/or variation in yearly reproductive success, but no study has yet assessed the relationships between the components of fitness and phenotypic quality while controlling for life span. We tried to fill this gap using data from long-term monitoring (23 years) of marked roe deer and bighorn sheep, two ungulates with very different life histories. In both species, we found a strong positive relationship between an adult female's mass and her probability of reaching old age: over the long term, bigger is indeed better for ungulate females. On the other hand, we found no evidence in either species that heavier females had higher fitness when differences in life span were accounted for: over the short term, bigger is not necessarily better. Our results indicate that, while broad differences in phenotypic quality affect individual fitness, when differences in life span are accounted for phenotypic quality has no residual effect on fitness. Therefore, within a given range of phenotypic quality, bigger is not always better, for reasons which may differ between species.     

Experimental evidence of gradual size‐dependent shifts in body size and growth of fish in response to warming

A challenge facing ecologists trying to predict responses to climate change is the few recent analogous conditions to use for comparison. For example, negative relationships between ectotherm body size and temperature are common both across natural thermal gradients and in small‐scale experiments. However, it is unknown if short‐term body size responses are representative of long‐term responses. Moreover, to understand population responses to warming, we must recognize that individual responses to temperature may vary over ontogeny. To enable predictions of how climate warming may affect natural populations, we therefore ask how body size and growth may shift in response to increased temperature over life history, and whether short‐ and long‐term growth responses differ. We addressed these questions using a unique setup with multidecadal artificial heating of an enclosed coastal bay in the Baltic Sea and an adjacent reference area (both with unexploited populations), using before‐after control‐impact paired time‐series analyses. We assembled individual growth trajectories of ~13,000 unique individuals of Eurasian perch and found that body growth increased substantially after warming, but the extent depended on body size: Only among small‐bodied perch did growth increase with temperature. Moreover, the strength of this response gradually increased over the 24 year warming period. Our study offers a unique example of how warming can affect fish populations over multiple generations, resulting in gradual changes in body growth, varying as organisms develop. Although increased juvenile growth rates are in line with predictions of the temperature–size rule, the fact that a larger body size at age was maintained over life history contrasts to that same rule. Because the artificially heated area is a contemporary system mimicking a warmer sea, our findings can aid predictions of fish responses to further warming, taking into account that growth responses may vary both over an individual's life history and over time.     

DEVELOPMENTAL MODE AND SPECIES GEOGRAPHIC RANGE IN REGULAR SEA URCHINS (ECHINODERMATA: ECHINOIDEA)

Among marine benthic organisms, the ability to disperse, primarily during the larval stage, is widely thought to influence the extent of species geographic range. Because related species often differ in their modes of larval development (pelagic, feeding larvae; pelagic, nonfeeding larvae; or brooded development), and these can have dramatically different planktonic intervals, the mode of development may influence geographic range. A global survey of 215 regular echinoids shows that species with pelagic, feeding larvae have significantly larger ranges than those with pelagic, nonfeeding larvae, but there is no difference in ranges between species with pelagic, nonfeeding larvae and those with brooded development. These patterns are maintained within the Cidaroida and the Temnopleuroida, which account for the great majority of species with pelagic, nonfeeding development and brooded development. This limited effect of developmental mode on geographic range is found among species occurring predominantly in waters shallower than 100 m. For species occurring deeper than 100 m, there is no significant difference in geographic range related to type of development. The relationship between developmental mode and species range was examined more closely for circa 30 species for which the developmental period was known from laboratory observations. Adjusting the developmental times to a common temperature, 20°C, using realistic values for Q₁₀ from 2.0 to 3.6, showed a highly significant, negative correlation between egg volume and developmental time, indicating the potential for developmental mode to influence the planktonic interval. However, there was no relationship between time in the plankton, estimated from unadjusted developmental times, and extent of species geographic range. These results suggest that developmental mode may influence extent of species geographic ranges indirectly through the consequences of dispersal for gene flow or recovery from disturbance.     

Rapid evolution of thermal plasticity in mountain lake Daphnia populations

Populations at risk of extinction due to climate change may be rescued by adaptive evolution or plasticity. Selective agents, such as introduced predators, may enhance or constrain plastic or adaptive responses to temperature. We tested responses of Daphnia to temperature by collecting populations from lakes across an elevational gradient in the presence and absence of fish predators (long‐term selection). We subsequently grew these populations at two elevations in field mesocosms over two years (short‐term selection), followed by a common‐garden experiment at two temperatures in the lab to measure life‐history traits. Both long‐term and short‐term selection affected traits, suggesting that genetic variation of plasticity within populations enabled individuals to rapidly evolve plasticity in response to high temperature. We found that short‐term selection by high temperature increased plasticity for growth rate in all populations. Fecundity was higher in populations from fishless lakes and body size showed greater plasticity in populations from warm lakes (long‐term selection). Neither body size nor fecundity were affected by short‐term thermal selection. These results demonstrate that plasticity is an important component of the life‐history response of Daphnia, and that genetic variation within populations enabled rapid evolution of plasticity in response to selection by temperature.     

Reproductive adaptations of Antarctic benthic invertebrates

The majority of Antarctic benthic invertebrates so far studied do not produce pelagic larvae, but develop non-pelagically by means of egg capsules, brooding or viviparity. The predominance of protected development in the Antarctic benthos is primarily due to the short period of summer phytoplankton abundance and the low sea temperature. Such conditions make it difficult for a larva to complete pelagic development before food becomes scarce in the surface waters. Prosobranch gastropods illustrate some important aspects of Antarctic benthic invertebrate reproduction. Species which develop non-pelagically have an aseasonal or prolonged spawning period. They produce a small number of large yolky eggs which remain in the benthos and develop slowly, giving rise to large, fully competent juveniles. Conversely, one species with free development has a short, synchronous spawning period during early summer, producing larvae which can benefit from the phytoplankton bloom. Protected development by means of brooding will limit dispersion, but transport on floating algae and by anchor ice may partially compensate for this in the Antarctic.     

Quantifying individual heterogeneity and its influence on life‐history trajectories: different methods for different questions and contexts

Heterogeneity among individuals influences the life‐history trajectories we observe at the population level because viability selection, selective immigration and emigration processes, and ontogeny change the proportion of individuals with specific trait values with increasing age. Here, we review the two main approaches that have been proposed to account for these processes in life‐history trajectories, contrasting how they quantify ontogeny and selection, and proposing ways to overcome some of their limitations. Nearly all existing approaches to model individual heterogeneity assume either a single normal distribution or a priori known groups of individuals. Ontogenetic processes, however, can vary across individuals through variation in life‐history tactics. We show the usefulness of describing ontogenetic processes by modelling trajectories with a mixture model that focuses on heterogeneity in life‐history tactics. Additionally, most methods examine individual heterogeneity in a single trait, ignoring potential correlations among multiple traits caused by latent common sources of individual heterogeneity. We illustrate the value of using a joint modelling approach to assess the presence of a shared latent correlation and its influence on life‐history trajectories. We contrast the strengths and limitations of different methods for different research questions, and we exemplify the differences among methods using empirical data from long‐term studies of ungulates.     

Major changes in trophic dynamics in large, deep sub-alpine Lake Maggiore from 1940s to 2002: a high resolution comparative palaeo-neolimnological study

1. We describe the changes in trophic dynamics in Lake Maggiore from c. 1943 to 2002 using subfossil cladoceran data from a high resolution sediment record, long‐term contemporary data series and historical information. During this period the lake went through a eutrophication phase until 1980 followed by oligotrophication. 2. During the eutrophication period a major increase occurred in the abundance of Chydorus sphaericus, the proportion of planktonic cladocerans and total abundance of cladocerans in the sediment. Since 1980 the abundance declined again and subfossil Eubosmina mucro length and contemporary Daphnia body length increased, most probably as a result of higher abundance of invertebrate predators. 3. Changes in the fish stock composition caused by the introduction of exotic fish during the pre‐eutrophication period and a complete ban on fishing because of Dichloro‐diphenil‐ethanes (DDTs) pollution of the lake (during oligotrophication) could also be detected in the community assemblage and size structure of the sediment zooplankton. 4. We found good correspondence between trophic changes inferred from cladoceran subfossils (community composition, size and predation pressure) and contemporary data, suggesting that sediment samples can be used to infer past development in trophic dynamics, including predation by fish and pelagic invertebrates in lakes with scarce neolimnological data. 5. Furthermore, by combining palaeolimnological cladoceran data rarely obtained from contemporary samples (e.g. benthic and plant‐associated cladocerans, mucro length of bosminids) with contemporary data of organisms poorly represented in the sediment record (e.g. remains of Bythotrephes and fishes) a more complete understanding of changes in trophic dynamics was obtained. 6. The detection in the sediments of meteorological events whose effects on zooplankton had been recorded in the long‐term studies also provided evidence that eutrophication tends to override climate signals. 7. We conclude that a combined palaeo‐neolimnological approach can be a powerful tool for elucidating past changes in the trophic dynamics of lakes and the interaction with climate induced changes, not least when high resolution sediment records are available.     

Warming shelf seas drive the subtropicalization of European pelagic fish communities

Pelagic fishes are among the most ecologically and economically important fish species in European seas. In principle, these pelagic fishes have potential to demonstrate rapid abundance and distribution shifts in response to climatic variability due to their high adult motility, planktonic larval stages, and low dependence on benthic habitat for food or shelter during their life histories. Here, we provide evidence of substantial climate‐driven changes to the structure of pelagic fish communities in European shelf seas. We investigated the patterns of species‐level change using catch records from 57 870 fisheries‐independent survey trawls from across European continental shelf region between 1965 and 2012. We analysed changes in the distribution and rate of occurrence of the six most common species, and observed a strong subtropicalization of the North Sea and Baltic Sea assemblages. These areas have shifted away from cold‐water assemblages typically characterized by Atlantic herring and European sprat from the 1960s to 1980s, to warmer‐water assemblages including Atlantic mackerel, Atlantic horse mackerel, European pilchard and European anchovy from the 1990s onwards. We next investigated if warming sea temperatures have forced these changes using temporally comprehensive data from the North Sea region. Our models indicated the primary driver of change in these species has been sea surface temperatures in all cases. Together, these analyses highlight how individual species responses have combined to result in a dramatic subtropicalization of the pelagic fish assemblage of the European continental shelf.     

Short‐ and long‐term costs of reproduction in a migratory songbird

Costs of reproduction represent a common life‐history trade‐off. Critical to understanding these costs in migratory species is the ability to track individuals across successive stages of the annual cycle. We assessed the effects of total number of offspring fledged and date of breeding completion on pre‐migratory body condition, the schedule of moult and annual survival in a migratory songbird, the Savannah Sparrow Passerculus sandwichensis. Between 2008 and 2010, moult was delayed for individuals that finished breeding later in the breeding period and resulted in reduced lean tissue mass during the pre‐migratory period, suggesting an indirect trade‐off between the timing of breeding completion and condition just prior to migration. Lean tissue mass decreased as the number of offspring fledged increased in 2009, a particularly cool and wet year, illustrating a direct trade‐off between reproductive effort and condition just prior to migration in years when weather is poor. However, using a 17‐year dataset from the same population, we found that parents that fledged young late in the breeding period had the highest survival and that number of offspring fledged did not affect survival, suggesting that individuals do not experience long‐term trade‐offs between reproduction and survival. Taken together, our results suggest that adult Savannah Sparrows pay short‐term costs of reproduction, but that longer‐term costs are mitigated by individual quality, perhaps through individual variation in resource acquisition.     

Early Environmental Influences on Growth of Arcto-Norwegian Cod, Gadus Morhua, From The 0-group To Adults

A high growth rate for Arcto-Norwegian cod, Gadus morhua, in the Barents Sea and adjacent areas from the larva period to the 0-group enhances survival and ultimately recruitment to the fishery. However, it appeared that high growth rates for a cohort through the 0-group were not continued as the cohort ages. Based on survey data, there was a significant negative correlation between the average length at the 0-group and its average length at ages 2 through 8. We provided evidence suggesting that this phenomenon was caused by the inter-annual variability in inflow of warm, prey-rich Atlantic water into the Barents Sea from the Norwegian Sea. Enhanced inflow provided favorable conditions for cod growth during the larva and juvenile pelagic intervals. However, this same strong inflow carried a proportion of the cohort farther to the east in the Barents Sea, where the bottom water is colder than in the west. The colder conditions experienced by such cohorts, as compared to cohorts that have a more westerly settlement, led to slower growth prior to age 2. Slow growth during this interval appeared to be the reason for these cohorts' relatively smaller mean length at older ages.     

Chemical cues, defence metabolites and the shaping of pelagic interspecific interactions

Several observations and model calculations suggest that chemically mediated interactions can structure planktonic food webs. However, only recently have improvements in chemical methods, coupled with ecological assays, led to the characterization of chemical cues that affect the behaviour and/or physiology of planktonic organisms. We are currently beginning to elucidate if or how chemical signals can directly affect the interactions between species and even shape complex community structures in aquatic systems. Here, we highlight recent research on the nature and action of chemical signals in the pelagic marine and freshwater environments, with an emphasis on kairomones and defence metabolites.     

Lotic meiofaunal community dynamics: colonisation, resilience and persistence in a spatially and temporally heterogeneous environment

1.  The spatial and temporal dynamics of lotic meiofaunal communities were examined with a focus on colonisation, maintenance of populations in lotic environments and persistence of meiofaunal communities.
2.  Lotic meiofaunal colonisation of new habitats may take place via a number of mechanisms and is rapid at both the patch scale (within hours–days) and the drainage basin scale (within 20 years). Successional patterns in lotic meiofaunal communities are evident although data are extremely limited.
3.  Lotic meiofaunal communities appear to be resilient to high flow disturbances. Resilience is moderated by the availability of in-stream refugia and habitat hydrology. Lotic meiofauna may also adopt a 'refuge as habitat' approach to such disturbances.
4.  Lotic cyclopoid copepods possess a common suite of life history characteristics that confers resilience to disturbances. Compared to pelagic planktonic species they have short generation times, many descendants per reproductive cycle and long lifespans. Females in 'source' populations are likely to survive disturbances and so could continuously reproduce over a long period of time producing large numbers of offspring which develop rapidly and recolonise 'sink' areas of the stream.
5.  Persistence of lotic meiofaunal communities is highly variable. Meiofaunal persistence does not increase with increasing proportions of in-stream flow refugia.     

The Dilution effect and the Space fill effect: Seeking to offset statistical artifacts when analyzing animal space use from telemetry fixes

Statistical analysis of the spatial dispersion of telemetry locations (fixes) has an important role in ecological studies on animal space use, in particular in the context of home range behaviour. A home range typically emerges as a complex mixture of both short term and long term memory-dependence in movement and side fidelity. An extended statistical mechanical framework – the Multi-scaled Random Walk model (MRW) – seeks to account for the complexity from memory effects on individual space use. In particular, four main classes of movement can be distinguished from analysis of the fractal dimension of the spatial dispersion of fixes; Brownian motion-like (including classic random walk and correlated random walk), Levy walk-like, memory-enhanced Brownian motion-like and MRW-like. The two former classes represent memory-less space use, whilst the latter two classes are memory enhanced. The statistical mechanical approach behind this classification ideally requires large sets of fixes for analysis, and it is also necessary to adjust for two statistical artifacts, the Dilution effect and the Space fill effect. We describe the nature of these artifacts based on output from simulations, and propose statistical model modifications to minimize their influence on parameter estimation. We illustrate the analysis and modification protocols on data from simulations of individual space use and on telemetry fixes from 11 free-ranging domestic sheep, Ovis aries. The material for analysis of the sheep data is very limited (ca. 140 fixes per individual), a common issue for applied ecology. Some fixes were also lost due to occasionally very long-range sallies by the individual (missing signal). The study area was thus too narrowly defined to embed the sheep's true space use during the given sampling period. Still, the proposed methods allows for tweaking consistent parameter estimation from the data, given a close focus on the statistical artifacts.     

How much effort is required for proper monitoring? Assessing the effects of different survey scenarios in a dry acidic grassland

Questions: The quality of any inferences derived from field studies or monitoring programmes depends on expenditure of time and effort to make the underlying observations. Here, we used a long‐term data set from a succession‐monitoring scheme to assess the effect of different survey scenarios. We asked: (1) how well does a survey reflect successional processes if sampling effort varies (a) in space (b) in length of total observation period, (c) in observation frequency and (d) with a combination of these factors? (2) What are the practical implications for devising monitoring programmes? Location: Lignite mining region of Central Germany, post‐mining landscape of Goitzsche (Saxony‐Anhalt). Methods: Based on our full data set, we constructed subsamples. For the full data set and all subsets, we constructed Markov models and compared them based on the predictions made. We assessed effects of survey intensity on model performance using generalized linear models and multiple logistic regressions. Results: Exploring the effects of different survey scenarios revealed significant effects of all three main features of survey intensity (sample size, length, frequency). The most important sampling feature was study length. However, we found interactive effects of sample size with study length and observation interval on model predictions. This indicates that for long‐term observations with multiple recording intervals a lower sample size in space is required to reveal the same amount of information as required in a shorter study or one with fewer intervals. Conversely, a high sample size may, to some degree, compensate for relatively short study periods. Conclusions: Monitoring activities should not be restricted to intensive sampling over only a few years. With clearly limited resources, a decrease of sampling intensity in space, and stretching these resources over a longer period would probably pay off much better than totally abandoning monitoring activities after an intensive, but short, campaign.     

A dispersive migration in the Atlantic Puffin and its implications for migratory navigation

Navigational control of avian migration is understood, largely from the study of terrestrial birds, to depend on either genetically or culturally inherited information. By tracking the individual migrations of Atlantic Puffins, Fratercula arctica, in successive years using geolocators, we describe migratory behaviour in a pelagic seabird that is apparently incompatible with this view. Puffins do not migrate to a single overwintering area, but follow a dispersive pattern of movements changing through the non-breeding period, showing great variability in travel distances and directions. Despite this within-population variability, individuals show remarkable consistency in their own migratory routes among years. This combination of complex population dispersion and individual route fidelity cannot easily be accounted for in terms of genetic inheritance of compass instructions, or cultural inheritance of traditional routes. We suggest that a mechanism of individual exploration and acquired navigational memory may provide the dominant control over Puffin migration, and potentially some other pelagic seabirds, despite the apparently featureless nature of the ocean.     

Multiple anthropogenic stressors cause ecological surprises in boreal lakes

The number of combinations of anthropogenic stressors affecting global change is increasing; however, few studies have empirically tested for their interactive effects on ecosystems. Most importantly, interactions among ecological stressors generate nonadditive effects that cannot be easily predicted based on single‐stressor studies. Here, we corroborate findings from an in situ mesocosm experiment with evidence from a whole‐ecosystem manipulation to demonstrate for the first time that interactions between climate and acidification determine their cumulative impact on the food‐web structure of coldwater lakes. Interactions among warming, drought, and acidification, rather than the sum of their individual effects, best explained significant changes in planktonic consumer and producer biomass over a 23‐year period. Further, these stressors interactively exerted significant synergistic and antagonistic effects on consumers and producers, respectively. The observed prevalence of long‐ and short‐term ecological surprises involving the cumulative impacts of multiple anthropogenic stressors highlights the high degree of uncertainty surrounding current forecasts of the consequences of global change.