Find research datasets worth reusing

Data from: Incubation under climate warming affects learning ability and survival in hatchling lizards

Despite compelling evidence for substantial individual differences in cognitive performance, it is unclear whether cognitive ability influences fitness of wild animals. In many animals, environmental stressors experienced in utero can produce substantial variation in the cognitive abilities of offspring. In reptiles, incubation temperatures experienced by embryos can influence hatchling brain function and learning ability. Under climate warming, the eggs of some lizard species may experience higher temperatures, which could affect the cognitive abilities of hatchlings. Whether such changes in cognitive abilities influence the survival of hatchlings is unknown. To determine whether incubation-induced changes in spatial learning ability affect hatchling survival, we incubated velvet gecko, Amalosia lesueurii, eggs using two fluctuating temperature regimes to mimic current (cold) versus future (hot) nest temperatures. We measured the spatial learning ability of hatchlings from each treatment, and released individually marked animals at two field sites in southeastern Australia. Hatchlings from hot-incubated eggs were slower learners than hatchlings from cold-incubated eggs. Survival analyses revealed that hatchlings with higher learning scores had higher survival than hatchlings with poor learning scores. Our results show that incubation temperature affects spatial learning ability in hatchling lizards, and that such changes can influence the survival of hatchlings in the wild.

Data from: Natural history and survival in stage 1 Val30Met transthyretin familial amyloid polyneuropathy

Objectives: To assess natural history and treatment effect on survival among transthyretin-associated familial amyloid polyneuropathy (TTR-FAP) Val30Met patients. Methods: Multi-institutional, hospital-based study of TTR-FAP Val30Met patients prospectively followed-up until December 2016, grouped into untreated (n = 1,771), liver transplant (LTx) (n = 957) or tafamidis-treated (n = 432) cohorts. Standardized mortality ratios (SMR), Kaplan-Meier and Cox methods were used to estimate excess mortality, survival probabilities and adjusted hazard ratios (HR) for all-cause mortality, respectively. Results: Disease-modifying treatments decreased TTR-FAP excess mortality from ten to four (SMR 3.92, 95% CI 2.64–5.59). Median overall survival of untreated and LTx-treated cohorts was 11.61 (95% CI 11.14–11.87) and 24.73 years (95% CI 22.90-27.09), respectively, and was not reached in the tafamidis-treated cohort (maximum follow-up, 10 years). Both disease-modifying treatments improved survival. Among early-onset patients (<50 years of age) tafamidis reduced the mortality risk compared with untreated patients by 91% (HR 0.09, 95% CI 0.03–0.25, p < 0.001) and with LTx-treated patients by 63% (HR 0.37, 95% CI 0.14–1.00, p = 0.050). Previous tafamidis treatment did not affect mortality risk after LTx (HR 0.83, 95% CI 0.25-2.78, p = 0.763). Among late-onset patients (≥50 years), tafamidis reduced mortality risk by 82% compared with untreated patients (HR 0.18, 95% CI 0.06-0.49, p = 0.001). Conclusions: LTx and tafamidis convey substantial survival benefits, but TTR-FAP mortality remains higher than in the general population. These results strongly reinforce the importance of timely diagnosis and earlier treatment, boosting the pursuit for an increased life expectancy.

opencc-zeroDec 2014View details →

Data from: Simultaneous declines in summer survival of three shorebird species signals a flyway at risk

There is increasing concern about the world's animal migrations. With many land-use and climatological changes occurring simultaneously, pinning down the causes of large-scale conservation problems requires sophisticated and data-intensive approaches. Declining shorebird numbers along the East Asian–Australasian Flyway, in combination with data on habitat loss along the Yellow Sea (where these birds refuel during long-distance migrations), indicate a flyway under threat. If habitat loss at staging areas indeed leads to flyway-wide bird losses, we would predict that: (i) decreases in survival only occur during the season that birds use the Yellow Sea, and (ii) decreases in survival occur in migrants that share a reliance on the vanishing intertidal flats along the Yellow Sea, even if ecologically distinct and using different breeding grounds. Monitored from 2006–2013, we analysed seasonal apparent survival patterns of three shorebird species with non-overlapping Arctic breeding areas and considerable differences in foraging ecology, but a shared use of both north-west Australian non-breeding grounds and the Yellow Sea coasts to refuel during northward and southward migrations (red knot Calidris canutus piersmai, great knot Calidris tenuirostris, bar-tailed godwit Limosa lapponica menzbieri). Distinguishing two three-month non-breeding periods and a six-month migration and breeding period, and analysing survival of the three species and the three seasons in a single model, we statistically evaluated differences at both the species and season levels. Whereas apparent survival remained high in north-west Australia, during the time away from the non-breeding grounds survival in all three species began to decline in 2011, having lost 20 percentage points by 2012. By 2012 annual apparent survival had become as low as 0.71 in bar-tailed godwits, 0.68 in great knots and 0.67 in red knots. In a separate analysis for red knots, no mortality occurred during the migration from Australia to China. In the summers of low summer survival, weather conditions were benign in the Arctic breeding areas. We argue that rapid seashore habitat loss in the Yellow Sea is the most likely explanation of reduced summer survival, with dire (but uncertain) forecasts for the future of these flyway populations. This interpretation is consistent with recent findings of declining shorebird numbers at seemingly intact southern non-breeding sites. Policy implications. Due to established economic interests, governments are usually reluctant to act for conservation, unless unambiguous evidence for particular cause–effect chains is apparent. This study adds to an increasing body of evidence that habitat loss along the Yellow Sea shores explains the widespread declines in shorebird numbers along the East Asian–Australasian Flyway and threatens the long-term prospects of several long-distance migrating species. To halt further losses, the clearance of coastal intertidal habitat must stop now.

Data from: A small badge of longevity: opposing survival selection on the size of white and black wing markings

According to handicap principle, exaggerated ornamental traits are supposed to exert costs on their bearers. However, there is much less theoretical and practical consensus about whether and under which conditions ornament expression should positively correlate with survival. We measured age-related variation and survival selection on the size of white wing patches and black wing tips in a long-lived monogamous seabird, the common gull Larus canus. Males had larger white patches than females but patch size showed concave relationship with age irrespective of sex, suggesting that white patch size was prone to senescence in both sexes. Extent of wing tip abrasion correlated negatively with the size of white patch, suggesting, in agreement with the Zahavian handicap hypothesis that only individuals with largest ornaments are able of maintaining them and not paying cost of displaying them. Areas of white wing patches and black wing tips correlated negatively. Irrespective of sex, survival selection favored birds with larger white wing patches and smaller black wing tips, which suggests that white and black wing markings may have coevolved as reverse components of a single ornament. Altogether, our results provide an evidence for the case where survival selection on ornamental traits in females is not weaker than in males. Absence of sex differences with respect to most of observed patterns is consistent with a prediction that among monogamous long-lived species with biparental care, mutual mate choice leads to evolution of elaborate ornamental traits in both sexes.

Data from: Evaluation of acoustic telemetry grids for determining aquatic animal movement and survival

1. Acoustic telemetry studies have frequently prioritized linear configurations of hydrophone receivers, such as perpendicular from shorelines or across rivers, to detect the presence of tagged aquatic animals. This approach introduces unknown bias when receivers are stationed for convenience at geographic bottlenecks (e.g., at the mouth of an embayment or between islands) as opposed to deployments following a statistical sampling design. 2. We evaluated two-dimensional acoustic receiver arrays (grids: receivers spread uniformly across space) as an alternative approach to provide estimates of survival, movement, and habitat use. Performance of variably-spaced receiver grids (5–25 km spacing) was evaluated by simulating (1) animal tracks as correlated random walks (speed: 0.1–0.9 m/s; turning angle standard deviation: 5–30 degrees); (2) variable tag transmission intervals along each track (nominal delay: 15–300 seconds); and (3) probability of detection of each transmission based on logistic detection range curves (midpoint: 200–1500 m). From simulations, we quantified i) time between successive detections on any receiver (detection time), ii) time between successive detections on different receivers (transit time), and iii) distance between successive detections on different receivers (transit distance). 3. In the most restrictive detection range scenario (200 m), the 95th percentile of transit time was 3.2 days at 5 km grid spacing, 5.7 days at 7 km, and 15.2 days at 25 km; for the 1500 m detection range scenario, it was 0.1 days at 5 km, 0.5 days at 7 km, and 10.8 days at 25 km. These values represented upper bounds on the expected maximum time that an animal could go undetected. Comparison of the simulations with pilot studies on three fishes (walleye Sander vitreus, common carp Cyprinus carpio, and channel catfish Ictalurus punctatus) from two independent large lake ecosystems (lakes Erie and Winnipeg) revealed shorter detection and transit times than what simulations predicted. 4. By spreading effort uniformly across space, grids can improve understanding of fish migration over the commonly employed receiver line approach, but at increased time cost for maintaining grids.

Data from: Survival to independence in relation to pre-fledging development and latitude in songbirds across the globe

Species differ strongly in their life histories, including the probability of survival. Annual adult survival was investigated extensively in the past, whereas juvenile survival, and especially survival to independence, received much less attention. Yet, they are critical for our understanding of population demography and life-history evolution. We investigated post-fledging survival to independence (i.e. survival upon leaving the nest until nutritional independence) in 74 species of passerine birds worldwide based on 100 population level estimates extracted from published literature. Our comparative analyses revealed that survival to independence increased with the length of nestling period and relative fledging mass (ratio of fledging mass to adult body mass). At the same time, species with higher nest predation rates had shorter nestling periods and lower relative fledging mass. Thus, we identify an important trade-off in life history strategies: staying longer in the nest may improve post-fledging survival due to enhanced flight ability and sensory functions, but at the cost of a longer exposure to nest predators and increased mortality due to nest predation. Additionally, post-fledging survival to independence did not differ between species from the northern temperate zone vs species from the tropics and southern hemisphere. However, analyses of post-fledging survival curves suggest that 1) daily survival rates are not constant and improve quickly upon leaving the nest, and 2) species in the tropics and southern hemisphere have higher daily post-fledging survival rates than northern temperate species. Nevertheless, due to the accumulation of mortality risk during their much longer periods of post-fledging care, overall survival until independence is comparable across latitudes. Obtaining high-quality demographic data across latitudes to evaluate the generality of these findings and mechanisms underlying them should be a research priority.

Data from: Male and female helper effects on maternal investment and adult survival in red-winged fairy-wrens

Despite its importance for the evolution of cooperative breeding, it has proven difficult to determine whether helpers improve their recipients' fitness. Helpers affect fitness in multiple ways, both positive and negative, but their effects can also be concealed through reduced maternal investment. Furthermore, determining the direction of causation is difficult, as helper presence may indicate a productive territory, rather than high productivity indicating an effect of help. In cooperatively breeding red-winged fairy-wrens (Malurus elegans) groups reduce care when they have male helpers, but groups with female helpers do not, so nestlings receive more food. Thus our predictions vary with helper sex rather than helper number, and by studying within-group changes with regard to group composition we separate phenotypically plastic responses from among-group correlations. Females did not reduce egg size in response to an increasing number of female helpers. However, more male or female helpers allowed females to lay larger clutches and more female helpers reduced re-nesting intervals. There was mixed support for a benefit of load lightening: Helpers, but not breeders, gained survival benefits with increasing number of male helpers. However, helper survival decreased with the number of female helpers, suggesting that increased competition counterbalanced these male helper benefits. We also found consistent among-group differences, which would have erroneously been interpreted as helper effects had we not disentangled the within-group changes with regard to group composition. This study highlights the importance of assessing carers' benefits in relation to both group composition and size, and of investigating the within-individual plastic response of helper effects.

opencc-zeroDec 2012View details →

Data from: Genetic consequences of a century of protection: serial founder events and survival of the little spotted kiwi (Apteryx owenii)

We present the outcome of a century of post-bottleneck isolation of a long-lived species, the little spotted kiwi (Apteryx owenii, LSK) and demonstrate that profound genetic consequences can result from protecting few individuals in isolation. LSK were saved from extinction by translocation of five birds from South Island, New Zealand to Kapiti Island 100 years ago. The Kapiti population now numbers some 1200 birds and provides founders for new populations. We used 15 microsatellite loci to compare genetic variation among Kapiti LSK and the populations of Red Mercury, Tiritiri Matangi and Long Islands that were founded with birds from Kapiti. Two LSK native to D'Urville Island were also placed on Long Island. We found extremely low genetic variation and signatures of acute and recent genetic bottleneck effects in all four populations, indicating that LSK have survived multiple genetic bottlenecks. The Long Island population appears to have arisen from a single mating pair from Kapiti, suggesting there is no genetic contribution from D'Urville birds among extant LSK. The Ne/NC ratio of Kapiti Island LSK (0.03) is exceptionally low for terrestrial vertebrates and suggests that genetic diversity might still be eroding in this population, despite its large census size.

Data from: Hidden survival heterogeneity of three common eider populations in response to climate fluctuations

(1) Understanding how individuals and populations respond to fluctuations in climatic conditions is critical to explain and anticipate changes in ecological systems. Most such studies focus on climate impacts on single populations without considering inter- and intra-population heterogeneity. However, comparing geographically dispersed populations limits the risk of faulty generalizations and helps to improve ecological and demographic models. (2) We aimed to determine whether differences in migration tactics among and within populations would induce inter- or intra-population heterogeneity in survival in relation to winter climate fluctuations. Our study species was the Common eider (Somateria mollissima), a marine duck with a circumpolar distribution, which is strongly affected by climatic conditions during several phases of its annual cycle. (3) Capture-mark-recapture (CMR) data were collected in two arctic (northern Canada and Svalbard) and one subarctic (northern Norway) population over a period of 18, 15 and 29 years, respectively. These three populations have different migration tactics and experience different winter climatic conditions. Using multi-event and mixture modelling, we assessed the association between adult female eider survival and winter conditions as measured by the North Atlantic Oscillation index. (4) We found that winter weather conditions affected survival of female eiders from each of these three populations. However, different mechanisms seemed to be involved. Survival of the two migrating arctic populations was impacted directly by changes in the NAO, whereas the subarctic resident population was affected by the NAO with time lags of two to three years. Moreover, we found evidence for intra-population heterogeneity in the survival response to the winter NAO in the Canadian eider population, where individuals migrate to distinct wintering areas. (5) Our results illustrate how individuals and populations of the same species can vary in their responses to climate variation. We suspect that the found variation in survival response of birds to winter conditions is partly explained by differences in migration tactic. Detecting and accounting for inter- and intra-population heterogeneity will improve our predictions concerning the response of wildlife to global changes.

opencc-zeroDec 2013View details →

Data from: Haldane's rule revisited: do hybrid females have a shorter lifespan? Survival of hybrids in a recent contact zone between two large gull species

Haldane's rule predicts that particularly high fitness reduction should affect the heterogametic sex of interspecific hybrids. Despite the fact that hybridization is widespread in birds, survival of hybrid individuals is rarely addressed in studies of avian hybrid zones, possibly because of methodological constraints. Here, having applied capture-mark-recapture models to an extensive, 19-year-long dataset on individually marked birds, we estimate annual survival rates of hybrid individuals in the hybrid zone between herring (Larus argentatus) and Caspian (L. cachinnans) gulls. In both parental species, males have a slightly higher survival rate than females (model-weighted mean ± SE: herring gull males 0.88 ± 0.01, females 0.87 ± 0.01, Caspian gull males 0.88 ± 0.01, females 0.87 ± 0.01). Hybrid males do not survive for a shorter time than non-hybrid ones (0.88 ± 0.01), whereas hybrid females have the lowest survival rate among all groups of individuals (0.83 ± 0.03). This translates to a shorter adult (reproductive) lifespan (on average by 1.7-1.8 years, i.e. ca 25%) compared to non-hybrid females. We conclude that, in line with Haldane's rule, the lower survival rate of female hybrids may contribute to selection against hybrids in this hybrid zone.

opencc-zeroDec 2013View details →

Data from: Survival of the fattest? Indices of body condition do not predict viability in the brown anole (Anolis sagrei)

1. Measures of body mass and length are commonly used to derive indices of condition, which are often assumed to reflect the energetic state of an animal and, by extension, to predict its fitness. However, the relationship between condition and fitness is rarely quantified, and the appropriate method(s) for deriving indices of condition are frequently debated. 2. Data from a decade of mark-recapture studies involving over 4,600 individual lizards (Anolis sagrei) and 41 replicates of selection across seven populations were used to test the common assumption that condition, as estimated from body mass and length, is a strong predictor of adult survival, an important component of fitness. Inferences about natural selection were compared between two alternative indices of condition: the popular residual index (Ri), and the scaled mass index (Mi), which was recently proposed as a more appropriate method. 3. Linear, quadratic, and correlational selection gradients obtained using Ri and Mi were highly correlated with one another. Relative to variance in selection among replicates and to error associated with the estimation of selection gradients, variance due to the use of alternative condition indices was minor and effectively negligible. 4. Contrary to the intuitive prediction that individuals in better condition should exhibit higher survival, there was no evidence for strong or consistent linear (directional) selection for higher condition indices in either males or females. Significant quadratic (stabilizing or disruptive) selection on condition was similarly rare in both sexes. Correlational selection favored combinations of large size and high condition in males, but not females. 5. Collectively, these results indicate that inferences about natural selection may be robust to the choice between indices of condition, but that indices of condition can be unreliable as proxies for fitness, particularly when relationships between fitness components and condition are contingent upon interactions with other traits.

Data from: Short-term and medium-term survival of critically ill patients with solid tumours admitted to the intensive care unit: a retrospective analysis

Objectives: Patients with cancer frequently require unplanned admission to the Intensive Care Unit (ICU). Our objectives were to assess hospital and 180-day mortality in patients with a non-haematological malignancy and unplanned ICU admission, and to identify which factors present on admission were the best predictors of mortality. Design: Retrospective review of all patients with a diagnosis of solid tumours following unplanned admission to the ICU between 1st August 2008 and 31st July 2012. Setting: Single centre tertiary care hospital in London (UK) Participants: 300 adult patients with non-haematological solid tumours requiring unplanned admission to the ICU. Interventions: None Primary and secondary outcomes: Hospital and 180-day survival Results: 300 patients were admitted to the ICU (median age 66.5 years; 61.7% male). Survival to hospital discharge and 180-days were 69% and 47.8%, respectively. Greater number of failed organ systems on admission was associated with significantly worse hospital survival (p<0.001) but not with 180-day survival (p=0.24). In multivariate analysis, predictors of hospital mortality were the presence of metastases [odds ratio (OR 1.97), 95% confidence interval (CI) 1.08-3.59], Acute Physiology and Chronic Health Evaluation II (APACHE II) score (OR 1.07, 95% CI 1.01-1.13) and a Glasgow Coma Scale score <7 on admission to ICU (OR 5.21, 95% CI 1.65-16.43). Predictors of worse 180-day survival were the presence of metastases (OR 2.82, 95% CI 1.57-5.06), APACHE II score (OR 1.07, 95% CI 1.01-1.13) and sepsis (OR 1.92, 95% CI 1.09-3.38). Conclusions: Short and medium-term survival in patients with solid tumours admitted to ICU is better than previously reported, suggesting that the presence of cancer alone should not be a barrier to ICU admission.

opencc-zeroDec 2014View details →

Data from: An R package for analyzing survival using continuous-time open capture-recapture models

Capture–recapture software packages have proven to be very powerful tools for analysing factors affecting survival in wild populations. However, all such packages are limited to discrete-time protocols. Appropriate survival analysis tools are still lacking for data acquired from continuous-time protocols. We have developed a statistical method and propose an r package for analysing such data based on an extension of classical survival analysis models incorporating an inhomogeneous Poisson process for modelling capture histories. First, data were simulated from a continuous-time protocol. These data were used to (i) compare survival estimation biases of discrete- and continuous-time approaches and (ii) investigate the performance and accuracy of our r package for four types of covariates: factors varying between individuals (like sex), in time (like climatic factors), both in time and between individuals (like physical condition) and age (as a categorical factor). Secondly, the r package has been applied to a real data set for survival analysis of cats in the Kerguelen archipelago (regrouping 682 cats over 20 years) as an illustrative example. Results of the simulated data analysis show that the method performs better than its discrete-time counterpart for analysing data acquired from continuous-time protocols. It provides unbiased parameter estimates for all parameters except those that vary both in time and between individuals – which is not surprising, since in our case, these factors were not updated in continuous time (i.e. only upon capture). When applied to the Kerguelen cat data set, the results suggest that survival is lower in juveniles than in adults and subadults, varies between study sites and increases with physical condition, and this latter effect being more important in females than in males. Sex, season, temporal linear trend in survival and the NDVI vegetation index were also tested but were not found to be significant. However, confidence intervals were too large (due to a low recapture rate) for excluding such effects. Further analyses are still needed for rigorous covariate testing in this context. In conclusion, continuous-time approaches – such as that presented in this paper – should be preferred when data acquired from continuous-time protocols is analysed.

opencc-zeroJun 2019View details →

Data from: Phylogeography of Dendrolimus punctatus (Lepidoptera: Lasiocampidae): population differentiation and last glacial maximum survival

Although the Masson pine moth, Dendrolimus punctatus, is one of the most destructive forest pest insects and is an endemic condition in China, we still do not fully understand the patterns of how its distribution range varies in response to Quaternary climatic oscillations. Here we sequenced one maternally inherited mitochondrial gene (COI) and biparentally inherited nuclear data (ITS1 and ITS2 ) among 23 natural populations across the entire range of the species in China. A total of 51 mitotypes and 38 ribotypes were separately obtained using mtDNA and ITS1 data. Furthermore, significant phylogeographical structure (NST > GST, P < 0.01) were detected. The spatial distribution of mitotypes implied that two distinct groups existed in the species: one in the southwest distribution, including 10 locations, and the other located in the northeast region of China. It is suggested, therefore that each group was derived from ancestors that occupied different isolated refugia during previous periods, possibly Last Glacial Maximum (LGM). Mismatch distribution and Bayesian population dynamics analysis suggested the population size underwent sudden expansion, which is consistent with the results of ecological niche modelling (ENM). As a typical phytophagous insect, the history of population expansion was in accordance with the host plants, providing abundant food resources and habitat. Intraspecific success rate of barcoding identification was lower than interspecific ones, indicating a level of difficulty in barcoding individuals from different populations. However, it still provides an early insight into the pattern of genetic diversity within a species.

Data from: Approximate Bayesian computation analysis of EST-associated microsatellites indicates that the broadleaved evergreen tree Castanopsis sieboldii survived the Last Glacial Maximum in multiple refugia in Japan

Climatic changes have played major roles in plants' evolutionary history. Glacial oscillations have been particularly important, but some of their effects on plants' populations are poorly understood, including the numbers and locations of refugia in Asian warm temperate zones. In the present study, we investigated the demographic history of the broadleaved evergreen tree species Castanopsis sieboldii (Fagaceae) during the last glacial period in Japan. We used approximate Bayesian computation (ABC) for model comparison and parameter estimation for the demographic modelling using 27 EST associated microsatellites. We also performed the species distribution modelling (SDM). The results strongly support a demographic scenario that the Ryukyu Islands and the western parts in the main islands (Kyushu and western Shikoku) were derived from separate refugia and the eastern parts in the main islands and the Japan Sea groups were diverged from the western parts prior to the coldest stage of the Last Glacial Maximum (LGM). Our data indicate that multiple refugia survived at least one in the Ryukyu Islands, and the other three regions of the western and eastern parts and around the Japan Sea of the main islands of Japan during the LGM. The SDM analysis also suggests the potential habitats under LGM climate conditions were mainly located along the Pacific Ocean side of coastal region. Our ABC-based study helps efforts resolve the demographic history of a dominant species in warm temperate broadleaved forests during and after the last glacial period, which provides a basic model for future phylogeographical studies using this approach.

Data from: Female sociality and sexual conflict shape offspring survival in a Neotropical primate

Most mammals live in social groups in which members form differentiated social relationships. Individuals may vary in their degree of sociality, and this variation can be associated with differential fitness. In some species, for example, female sociality has a positive effect on infant survival. However, investigations of such cases are still rare, and no previous study has considered how male infanticide might constrain effects of female sociality on infant survival. Infanticide is part of the male reproductive strategy in many mammals, and it has the potential to override, or even reverse, effects of female reproductive strategies, including sociality. Therefore, we investigated the relationships between female sociality, offspring survival, and infanticide risk in wild white-faced capuchin monkeys using long-term data from Santa Rosa, Costa Rica. Female capuchins formed differentiated bonds, and bond strength was predicted by kin relationship, rank difference, and the presence of female infants. Most females formed stable bonds with their top social partners, although bond stability varied considerably. Offspring of highly social females, who were often high-ranking females, exhibited higher survivorship during stable periods compared with offspring of less social females. However, offspring of highly social females were more likely to die or disappear during periods of alpha male replacements, probably because new alpha males are central to the group, and therefore more likely to target the infants of highly social, central females. This study shows that female sociality in mammals can have negative fitness consequences that are imposed by male behavior.

Data from: Additive effects of plant chemotype, mutualistic ants and predators on aphid performance and survival

1. Cascading effects in ecological systems acting across three or more trophic levels can be either of a resource-based (bottom-up) or natural enemy-based (top-down) nature. But, due to their complexity these effects are often considered separately and their relative strength, acting simultaneously, remains unknown. 2. In a semi-natural field experiment using tansy (Tanacetum vulgare L.) and the specialised tansy aphid Metopeurum fuscoviride Stroyan as a model system, we compared the effects of four distinct plant chemotypes (i.e. bottom-up), defined by the bouquet of their volatile terpenoids, on aphid population dynamics by manipulating the presence/absence of mutualistic ants and presence/absence of naturally-occurring predators (i.e. top-down). 3. Predators reduced aphid abundance and colony survival but did not reduce initial growth rate due to a time lag until predators arrived on the plants. Ants directly benefited initial aphid growth rates and abundance, even in the absence of predators, but not the number of days an aphid colony persisted on the plant. 4. Plant chemotype directly affected aphid growth rate and final abundances across the different plants and indirectly affected the abundances of tending ants and predators through effects on aphids. We found that tending ants were more abundant on one plant chemotype. Although ant abundance did not affect aphid population development, it became clear that ants had a preference towards aphids on certain chemotypes. However, a higher number of predators led to a lower number of aphids. 5. The results confirm the importance of plant chemical variation, acting through multiple effects on many species in arthropod communities, and support results from field studies. In a natural population, with a diverse selection of host-plant variants, aphid populations and their interacting species can therefore be structured at the level of an individual plant. Specialist aphids on patchily-distributed host plants can exhibit metacommunity dynamics at very local scales. Plant within-species variation within a local population is often ignored in metacommunity ecology, yet our work shows that this can have strong effects on insect-ant-natural enemy dynamics and therefore future research should incorporate this into current theory and experimental studies.

opencc-zeroDec 2014View details →

Data from: Context-dependent survival, fecundity, and predicted population-level consequences of brucellosis in African buffalo

1. Chronic infections may have negative impacts on wildlife populations, yet their effects are difficult to detect in the absence of long-term population monitoring. Brucella abortus, the bacteria responsible for bovine brucellosis, causes chronic infections and abortions in wild and domestic ungulates, but its impact on population dynamics is not well understood. 2. We report infection patterns and fitness correlates of bovine brucellosis in African buffalo based on (1) 7 years of cross-sectional disease surveys and (2) a 4-year longitudinal study in Kruger National Park (KNP), South Africa. We then used a matrix population model to translate these observed patterns into predicted population-level effects. 3. Annual brucellosis seroprevalence ranged from 8·7% (95% CI = 1·8–15·6) to 47·6% (95% CI = 35·1–60·1) increased with age until adulthood (>6) and varied by location within KNP. Animals were on average in worse condition after testing positive for brucellosis (F = −5·074, P < 0·0001), and infection was associated with a 2·0 (95% CI = 1·1–3·7) fold increase in mortality (χ2 = 2·039, P = 0·036). Buffalo in low body condition were associated with lower reproductive success (F = 2·683, P = 0·034), but there was no association between brucellosis and pregnancy or being observed with a calf. 4. For the range of body condition scores observed in the population, the model-predicted growth rate was λ = 1·11 (95% CI = 1·02–1·21) in herds without brucellosis and λ = 1·00 (95% CI = 0·85–1·16) when brucellosis seroprevalence was 30%. 5. Our results suggest that brucellosis infection can potentially result in reduced population growth rates, but because these effects varied with demographic and environmental conditions, they may remain unseen without intensive, longitudinal monitoring.

Data from: Family morph matters: factors determining survival and recruitment in a long-lived polymorphic raptor

From an evolutionary perspective recruitment into the breeding population represents one of the most important life history stages and ultimately determines the effective population size. In order to contribute to the next generation, offspring must survive to sexual maturity, secure a territory and find a mate. In this study we explore factors influencing both offspring survival and their subsequent recruitment into the local breeding population in a long-lived urban raptor, the black sparrowhawk (Accipiter melanoleucus). Adult black sparrowhawks show discrete colour polymorphism (dark and light morphs) and in South Africa morphs are distributed clinally with the highest proportion of dark morphs (c.75%) present in our study population on the Cape Peninsula. Parental morph was associated with both survival and recruitment. For survival, parental morph combination was important – with young produced by pairs of contrasting morphs having higher survival rates than young fledged from like-pairs. The association between recruitment and morph was more complex; with an interaction between male morph and breeding time, whereby recruitment of offspring from dark morph fathers was more likely when fledging earlier in the season. The opposite relationship was found for light morph fathers, with their offspring more likely to be recruited if fledged later in the season. This interaction may be due to differential morph-specific hunting success of fathers (males contribute most food provisioning), linked to background matching and crypsis in different weather conditions. Dark morph males may hunt more successfully in rainier and cloudier conditions which occur more frequently earlier in the breeding season and light morph males may be more successful later on, when weather conditions become increasingly brighter and drier. Our results reveal a complex situation whereby the family morph combination influences survival, and the father morph specifically recruitment, revealing morph specific benefits dependent on the timing of breeding. These empirical data are amongst the first to support the idea that differential fitness consequence of morph combination may explain balanced polymorphism in a vertebrate population.

Data from: Road salt and organic additives affect mosquito growth and survival: an emerging problem in wetlands

The global increase in the application rate of road salts such as sodium chloride (NaCl) has led to concern about their negative effects on roadside habitats and freshwater ecosystems. To reduce the application rate of NaCl and minimize the ecological effects of road salts, transportation agencies are continuously seeking alternative salts such as magnesium chloride (MgCl 2) and organic additives such as beet juice and distillation byproducts. Yet, there is remarkably little information about how these road salt alternatives and additives affect aquatic communities, including their effects on mosquito populations. Nonetheless, understanding how anthropogenic factors such as road salts and salt additives affect mosquito populations could help minimize threats to human health, especially in urban environments. We used outdoor, freshwater mesocosms to experimentally investigate how the road salt MgCl 2 and two organic additives affect mosquito (Culex restuans) survival and emergence. Additionally, we measured changes to abiotic aspects of the environment that could affect mosquito larvae during development. We found that increased concentrations of MgCl 2 reduced mosquito survival while organic additives increased food resources that, in turn, reduced the average time to emergence for mosquitoes. Additionally, the organic additives reduced dissolved oxygen (DO) to hypoxic levels, which might negatively affect mosquito predators such as fish. In the absence of toxic concentrations of MgCl 2 or other salts, reduced predation coupled with the faster emergence times, means that organic additives, might increase mosquito population size. More comprehensive studies of multi-trophic interactions in freshwater ecosystems should be conducted before agencies promote the application of alternative road salts and road salt additives.