Find research datasets worth reusing

Data from: Intraspecific trait variation and trade-offs within and across populations of a toxic dinoflagellate

Intraspecific trait diversity can promote the success of a species, as complementarity of functional traits within populations may enhance its competitive success and facilitates resilience to changing environmental conditions. Here, we experimentally determined the variation and relationships between traits in 15 strains of the toxic dinoflagellate Alexandrium ostenfeldii derived from two populations. Measured traits included growth rate, cell size, elemental composition, nitrogen uptake kinetics, toxin production and allelochemical potency. Our results demonstrate substantial variation in all analyzed traits both within and across populations, particularly in nitrogen affinity, which was even comparable to interspecific variation across phytoplankton species. We found distinct trade-offs between maximum nitrogen uptake rate and affinity, and between defensive and competitive traits. Furthermore, we identified differences in trait variation between the genetically similar populations. The observed high trait variation may facilitate development and resilience of harmful algal blooms under dynamic environmental conditions.

opencc-zeroDec 2013View details →

Data from: Does the niche-breadth or trade-off hypothesis explain the abundance-occupancy relationship in avian haemosporidia?

Two hypotheses have been proposed to explain the abundance-occupancy relationship (AOR) in parasites. The niche-breadth hypothesis suggests that host generalists are more abundant and efficient at colonizing different host communities than specialists. The trade-off hypothesis argues that host specialists achieve high density across their hosts' ranges, whereas generalists incur the high cost of adaptation to diverse immuno-defense systems. We tested these hypotheses using 386 haemosporidian cytochrome-b lineages (1894 sequences) recovered from 2318 birds of 103 species sampled in NW Africa, NW Iberia, W Greater Caucasus, and Transcaucasia. The number of regions occupied by lineages was associated with their frequency suggesting the presence of AOR in avian Haemosporidia. However, neither hypothesis provided a better explanation for the AOR. Although, the host-generalist Plasmodium SGS1 was over 3 times more abundant than other widespread lineages, both host specialists and generalists were successful in colonizing all study regions and achieved overall high prevalence.

Data from: Female ornamentation and the fecundity trade-off in a sex-role reversed pipefish

Sexual ornaments found only in females are a rare occurrence in nature. One explanation for this is that female ornaments are costly to produce and maintain and, therefore, females must trade-off resources related to reproduction to promote ornament expression. Here, we investigate whether a trade-off exists between female ornamentation and fecundity in the sex-role reversed, wide-bodied pipefish, Stigmatopora nigra. We measured two components of the disk-shaped, ventral-striped female ornament, body width and stripe thickness. After controlling for the influence of body size, we found no evidence of a cost of belly width or stripe thickness on female fecundity. Rather, females that have larger ornaments have higher fecundity and thus accurately advertise their reproductive value to males without incurring a cost to fecundity. We also investigated the relationship between female body size and egg size and found that larger females suffered a slight decrease in egg size and fecundity, although this decrease was independent of female ornamentation. More broadly, considered in light of similar findings in other taxa, lack of an apparent fecundity cost of ornamentation in female pipefish underscores the need to revisit theoretical assumptions concerning the evolution of female ornamentation.

opencc-zeroDec 2009View details →

Data from: Is local adaptation in Mimulus guttatus caused by trade-offs at individual loci?

Local adaptation is considered to be the result of fitness trade-offs for particular phenotypes across different habitats. However, it is unclear whether such phenotypic trade-offs exist at the level of individual genetic loci. Local adaptation could arise from trade-offs of alternative alleles at individual loci or by complementary sets of loci with different fitness effects of alleles in one habitat but selective neutrality in the alternative habitat. To evaluate the genome-wide basis of local adaptation, we performed a field-based quantitative trait locus (QTL) mapping experiment on recombinant inbred lines (RILs) created from coastal perennial and inland annual races of the yellow monkeyflower (Mimulus guttatus) grown reciprocally in native parental habitats. Overall, we detected 19 QTLs affecting one or more of 16 traits measured in two environments, most of small effect. We identified 15 additional QTL effects at two previously identified candidate QTLs (DIVERGENCE [DIV]). Significant QTL by environment interactions were detected at the DIV loci, which was largely attributable to genotypic differences at a single field site. We found no detectable evidence for trade-offs for any one component of fitness, although DIV2 showed a trade-off involving different fitness traits between sites, suggesting that local adaptation is largely controlled by non-overlapping loci. This is surprising for an outcrosser, implying that reduced gene flow prevents the evolution of individuals adapted to multiple environments. We also determined that native genotypes were not uniformly adaptive, possibly reflecting fixed mutational load in one of the populations.

opencc-zeroDec 2018View details →

Data from: Evolutionary design of a flexible, seasonally migratory, avian phenotype: why trade gizzard mass against pectoral muscle mass?

Migratory birds undergo impressive body remodelling over the course of an annual cycle. Prior to long-distance flights, red knots (Calidris canutus islandica) reduce gizzard mass while increasing body mass and pectoral muscle mass. Although body mass and pectoral muscle mass are functionally linked via their joint effects on flight performance, gizzard and pectoral muscle mass are thought to be independently regulated. Current hypotheses for observed negative within-individual covariation between gizzard and pectoral muscle mass in free-living knots are based on a common factor (e.g., migration) simultaneously affecting both traits, and/or protein limitation forcing allocation decisions. We used diet manipulations to generate within-individual variation in gizzard mass and test for independence between gizzard and pectoral muscle mass within-individuals outside the period of migration and under conditions of high protein availability. Contrary to our prediction, we observed a negative within-individual covariation between gizzard and pectoral muscle mass. We discuss this result as a potential outcome of an evolved mechanism underlying body remodelling associated with migration. Although our proposed mechanism requires empirical testing, this study echoes earlier calls for greater integration of studies of function and mechanism, and in particular, the need for more explicit consideration of the evolution of mechanisms underlying phenotypic design.

opencc-zeroDec 2016View details →

Data from: Trade-offs in the multi-use potential of managed boreal forests

1. Implementing multi-use forest management to account for both commercial and non-commercial ecosystem services is gaining increased global recognition. Despite its spatial extent, and great economic and ecological values, few studies have evaluated the boreal forest and its management to assess the potential for simultaneous delivery of a suite of ecosystem services. 2. Using data from a Swedish long-term experiment this study explores how biodiversity of the ground vegetation and potential delivery of multiple ecosystem services (timber production, carbon (C) storage and non-timber forest products) are influenced by two common silvicultural practices (thinning, fertilization and their interaction). 3. Diversity (diversity indices and species richness) of the ground vegetation was higher in thinned than in unthinned forest, something partly explained by six species of lichens that only occurred in thinned forest. In addition, supply of lichens for reindeer forage was three times higher in thinned forest. Fertilization negatively affected the lingonberry shrub (Vaccinium vitis-idaea). Timber production increased with fertilization, but decreased with thinning. The potential for C storage was highest in fertilized forests, which, apart from having the highest timber production, also supported the highest standing tree biomass. 4. The silvicultural practices evaluated induced trade-offs among the ecosystem features studied as thinning increased biodiversity of the ground vegetation, production potential of wild berries and lichens, but reduced timber production and the forest's potential for C storage. Fertilization, had the opposite effect, promoting the potential for C storage at the expense of biodiversity and the ecosystem services delivered by the ground vegetation. 5. Synthesis and applications. Silvicultural practice had a pronounced effect on the multi-use output, and trade-offs among values were common. Nevertheless, our study demonstrates that silvicultural practices that are currently adopted in Sweden can be used to adjust the multi-use potential output of forests, suggesting that commonly used practices can be applied to maintain, or even increase the multi-use potential of the boreal forest biome, if management objectives are allowed to vary across the landscape. A prerequisite for this is site specific management objectives that clearly determine the desired output.

opencc-zeroDec 2014View details →

Data from: Discovery of an unknown diversity of Leucinodes species damaging Solanaceae fruits in sub-Saharan Africa and moving in trade (Insecta, Lepidoptera, Pyraloidea)

The larvae of the Old World genera Leucinodes Guenée, 1854 and Sceliodes Guenée, 1854 are internal feeders in the fruits of Solanaceae, causing economic damage to cultivated plants like Solanum melongena and S. aethiopicum. In sub-Saharan Africa five nominal species of Leucinodes and one of Sceliodes occur. One of these species, the eggplant fruit and shoot borer L. orbonalis Guenée, 1854, is regarded as regularly intercepted from Africa and Asia in Europe, North and South America and is therefore a quarantine pest on these continents. We investigate the taxonomy of African Leucinodes and Sceliodes based on morphological characters in wing pattern, genitalia and larvae, as well as mitochondrial DNA, providing these data for identification of all life stages. The results suggest that both genera are congeneric, with Sceliodes syn. n. established as junior subjective synonym of Leucinodes. L. orbonalis is described from Asia and none of the samples investigated from Africa belong to this species. Instead, sub-Saharan Africa harbours a complex of eight endemic Leucinodes species. Among the former nominal species of Leucinodes (and Sceliodes) from Africa, only L. laisalis (Walker, 1859), comb. n. (Sceliodes) is confirmed, with Leucinodes translucidalis Gaede, 1917, syn. n. as a junior subjective synonym. The other African Leucinodes species were unknown to science and are described as new: L. africensis sp. n., L. ethiopica sp. n., L. kenyensis sp. n., L. malawiensis sp. n., L. pseudorbonalis sp. n., L. rimavallis sp. n. and L. ugandensis sp. n. An identification key based on male genitalia is provided for the African Leucinodes species. Most imports of Leucinodes specimens from Africa into Europe refer to Leucinodes africensis, which has been frequently imported with fruits during the last 50 years. In contrast, L. laisalis has been much less frequently recorded, and L. pseudorbonalis as well as L. rimavallis only very recently in fruit imports from Uganda. Accordingly, interceptions of Leucinodes from Africa into other continents will need to be re-investigated for their species identity and will likely require, at least in parts, revisions of the quarantine regulations. The following African taxa are excluded from Leucinodes: Hyperanalyta Strand, 1918, syn. rev. as revised synonym of Analyta Lederer, 1863; Analyta apicalis (Hampson, 1896), comb. n. (Leucinodes); Lygropia aureomarginalis (Gaede, 1916), comb. n. (Leucinodes); Syllepte hemichionalis Mabille, 1900, comb. rev., S. hemichionalis idalis Viette, 1958, comb. rev. and S. vagans (Tutt, 1890), comb. n. (Aphytoceros). Deanolis iriocapna (Meyrick, 1938), comb. n. from Indonesia is originally described and misplaced in Sceliodes, and L. cordalis (Doubleday, 1843), comb. n. (Margaritia) from New Zealand, L. raondry (Viette, 1981), comb. n. (Daraba) from Madagascar as well as L. grisealis (Kenrick, 1912), comb. n. (Sceliodes) from New Guinea are transferred from Sceliodes to Leucinodes. While Leucinodes is now revised from Africa, it still needs further revision in Asia.

opencc-zeroDec 2012View details →

Data from: Ancient trade routes shaped the genetic structure of horses in eastern Eurasia

Animal exchange networks have been shown to play an important role in determining gene flow among domestic animal populations. The Silk Road is one of the oldest continuous exchange networks in human history, yet its effectiveness in facilitating animal exchange across large geographic distances and topographically challenging landscapes has never been explicitly studied. Horses are known to have been traded along the Silk Roads; however, extensive movement of horses in connection with other human activities may have obscured the genetic signature of the Silk Roads. To investigate the role of the Silk Roads in shaping the genetic structure of horses in eastern Eurasia we analysed microsatellite genotyping data from 455 village horses sampled from 17 locations. Using least-cost path methods, we compared the performance of models containing the Silk Roads as corridors for gene flow with models containing single landscape features. We also determined whether the recent isolation of former Soviet Union countries from the rest of Eurasia has affected the genetic structure of our samples. The overall level of genetic differentiation was low, consistent with historically high levels of gene flow across the study region. The spatial genetic structure was characterised by a significant, albeit weak, pattern of isolation by distance across the continent with no evidence for the presence of distinct genetic clusters. Incorporating landscape features considerably improved the fit of the data; however, when we controlled for geographic distance, only the correlation between genetic differentiation and the Silk Roads remained significant, supporting the effectiveness of this ancient trade network in facilitating gene flow across large geographic distances in a topographically complex landscape.

Data from: A transmission-virulence evolutionary trade-off explains attenuation of HIV-1 in Uganda

Evolutionary theory hypothesizes that intermediate virulence maximizes pathogen fitness as a result of a trade-off between virulence and transmission, but empirical evidence remains scarce. We bridge this gap using data from a large and long-standing HIV-1 prospective cohort, in Uganda. We use an epidemiological-evolutionary model parameterised with this data to derive evolutionary predictions based on analysis and detailed individual-based simulations. We robustly predict stabilising selection towards a low level of virulence, and rapid attenuation of the virus. Accordingly, set-point viral load, the most common measure of virulence, has declined in the last 20 years. Our model also predicts that subtype A is slowly outcompeting subtype D, with both subtypes becoming less virulent, as observed in the data. Reduction of set-point viral loads should have resulted in a 20% reduction in incidence, and a three years extension of untreated asymptomatic infection, increas ing opportunities for timely treatment of infected individuals.

opencc-zeroDec 2013View details →

Data from: The jack-of-all-trades is master of none: a pathogen's ability to infect a greater number of host genotypes comes at a cost of delayed reproduction.

A trade-off between a pathogen's ability to infect many hosts and its reproductive capacity on each host genotype is predicted to limit the evolution of an expanded host range, yet few empirical results provide evidence for the magnitude of such trade-offs. Here, we test the hypothesis for a trade-off between the number of host genotypes that a fungal pathogen can infect (host genotype range) and its reproductive capacity on susceptible plant hosts. We utilized strains of the oat crown rust fungus that carried widely varying numbers of virulence (avr) alleles known to determine host genotype range. We quantified total spore production and the expression of four pathogen life history stages: infection efficiency, time until reproduction, pustule size, and spore production per pustule. In support of the trade-off hypothesis, we found that virulence level, the number of avr alleles per pathogen strain, was correlated with significant delays in the onset of reproduction and with smaller pustule sizes. Modeling from our results, we conclude that trade-offs have the capacity to constrain the evolution of host genotype range in local populations. In contrast, long term trends in virulence level suggests that the continued deployment of resistant host lines over wide regions of the USA has generated selection for increased host genotype range.

opencc-zeroDec 2016View details →

Data from: When do trade-offs occur? The roles of energy constraints and trait flexibility in a bushcricket

In many animal species, the expression of sexually-selected traits is negatively correlated with survival traits such as immune function, a relationship termed a 'trade-off'. But an alternative in which sexually-selected traits are positively correlated with survival traits is also widespread. The nature of inter-trait relationships may be largely determined by overall energy expenditure, energy availability, and trait flexibility, with trade-offs expected when individuals are subject to energy constraints. We tested this hypothesis in Ephippiger diurnus, a European bushcricket in which males are distinguished by two prominent sexually-selected traits, acoustic calls and a large spermatophore transferred to the female at mating, and where immune function may be critical in survival. E. diurnus are distributed as small, isolated populations that are differentiated genetically and behaviorally. We analyzed songs, spermatophores, and the immune function in male individuals from eight populations spanning a range of song types. As predicted, we only found trade-offs in those populations that expended more energy on song and were less flexible in their ability to adjust that expenditure. Ultimately, energy constraints and resulting trade-offs may limit the evolution of song exaggeration in E. diurnus populations broadcasting long calls comprised of multiple 'syllables'.

Data from: Large-effect mutations generate trade-off between predatory and locomotor ability during arms race coevolution with deadly prey

Adaptive evolution in response to one selective challenge may disrupt other important aspects of performance. Such evolutionary trade-offs are predicted to arise in the process of local adaptation, but it is unclear if these phenotypic compromises result from the antagonistic effects of simple amino acid substitutions. We tested for trade-offs associated with beneficial mutations that confer tetrodotoxin (TTX) resistance in the voltage-gated sodium channel (NaV1.4) in skeletal muscle of the common garter snake (Thamnophis sirtalis). Separate lineages in California and the Pacific Northwest independently evolved TTX-resistant changes to the pore of NaV1.4 as a result of arms race coevolution with toxic prey, newts of the genus Taricha. Snakes from the California lineage that were homozygous for an allele known to confer large increases in toxin resistance (NaV1.4LVNV) had significantly reduced crawl speed compared to individuals with the ancestral TTX-sensitive channel. Heterologous expression of native snake NaV1.4 proteins demonstrated that the same NaV1.4LVNV allele confers a dramatic increase in TTX resistance and a correlated decrease in overall channel excitability. Our results suggest the same mutations that accumulate during arms race coevolution and beneficially interfere with toxin-binding also cause changes in electrophysiological function of the channel that may affect organismal performance. This trade-off was only evident in the predator lineage where coevolution has led to the most extreme resistance phenotype, determined by four critical amino acid substitutions. If these biophysical changes also translate to a fitness cost—for example, through the inability of T. sirtalis to quickly escape predators—then pleiotropy at this single locus could contribute to observed variation in levels of TTX resistance across the mosaic landscape of coevolution.

opencc-zeroDec 2013View details →

Data from: A conifer–angiosperm divergence in the growth vs shade tolerance trade-off underlies the dynamics of a New Zealand warm-temperate rain forest

1. A central tenet of forest ecology is that succession and regeneration dynamics are driven by an interspecific trade-off between juvenile growth rates in high light and shade tolerance. There is evidence, however, that a single trade-off axis may fail to explain the dynamics of mixed conifer-angiosperm rainforests in the southern hemisphere, especially in New Zealand. 2. We tested for growth vs shade tolerance trade-offs by measuring juvenile growth of five podocarps and five broadleaved canopy angiosperms across a wide range of light environments in a New Zealand warm-temperate rainforest. The light compensation point of growth was used as a measure of species light requirements, which we then compared with height growth in 10% light, approximating the environments encountered beneath small tree-fall gaps. 3. Despite considerable overlap between the ranges of both growth rates and compensation points found in the two lineages, major axis tests showed that the growth vs shade tolerance trade-off differed significantly between podocarp and angiosperm species. At a common compensation point, angiosperms were faster-growing than podocarps in 10% light. However, juveniles of these angiosperm species were notably scarce in the more open environments associated with forest margins. 4. Synthesis. A conifer–angiosperm divergence in the growth vs shade tolerance trade-off may explain long-standing problems of the dynamics of these forests. Although juveniles of most lowland podocarps can tolerate considerable shade, the more vigorous response of broadleaved angiosperms to small canopy openings enables them to out-compete podocarps in old-growth stands. The greater abundance of podocarp juveniles on forest margins cannot be attributed to them outcompeting angiosperm species where light is abundant, and is likely to reflect superior resistance to frost and/or drought. The drivers of the dynamics of New Zealand's podocarp–broadleaved forests therefore differ appreciably from those ascribed to tropical and north-temperate forests.

Data from: Reproductive trade-offs in extant hunter-gatherers suggest adaptive mechanism for the Neolithic expansion

The Neolithic demographic transition remains a paradox, because it is associated with both higher rates of population growth and increased morbidity and mortality rates. Here we reconcile the conflicting evidence by proposing that the spread of agriculture involved a life history quality–quantity trade-off whereby mothers traded offspring survival for increased fertility, achieving greater reproductive success despite deteriorating health. We test this hypothesis by investigating fertility, mortality, health, and overall reproductive success in Agta hunter-gatherers whose camps exhibit variable levels of sedentarization, mobility, and involvement in agricultural activities. We conducted blood composition tests in 345 Agta and found that viral and helminthic infections as well as child mortality rates were significantly increased with sedentarization. Nonetheless, both age-controlled fertility and overall reproductive success were positively affected by sedentarization and participation in cultivation. Thus, we provide the first empirical evidence, to our knowledge, of an adaptive mechanism in foragers that reconciles the decline in health and child survival with the observed demographic expansion during the Neolithic.

opencc-zeroMay 2020View details →

Metabolic rate, context-dependent selection, and the competition-colonization trade-off

<p class="abstract_para">Metabolism is linked with the pace‐of‐life, co‐varying with survival, growth, and reproduction. Metabolic rates should therefore be under strong selection and, if heritable, become less variable over time. Yet intraspecific variation in metabolic rates is ubiquitous, even after accounting for body mass and temperature. Theory predicts variable selection maintains trait variation, but field estimates of how selection on metabolism varies are rare. We use a model marine invertebrate to estimate selection on metabolic rates in the wild under different competitive environments. Fitness landscapes varied among environments separated by a few centimeters: interspecific competition selected for higher metabolism, and a faster pace‐of‐life, relative to competition‐free environments. Populations experience a mosaic of competitive regimes; we find metabolism mediates a competition‐colonization trade‐off across these regimes. Although high metabolic phenotypes possess greater competitive ability, in the absence of competitors, low metabolic phenotypes are better colonizers. Spatial heterogeneity and the variable selection on metabolic rates that it generates is likely to maintain variation in metabolic rate, despite strong selection in any single environment.</p>

Data from: Regional drivers of clutch loss reveal important trade-offs for beach-nesting birds

Coastal birds are critical ecosystem constituents on sandy shores, yet are threatened by depressed reproductive success resulting from direct and indirect anthropogenic and natural pressures. Few studies examine clutch fate across the wide range of environments experienced by birds; instead, most focus at the small site scale. We examine survival of model shorebird clutches as an index of true clutch survival at a regional scale (∼200 km), encompassing a variety of geomorphologies, predator communities, and human use regimes in southeast Queensland, Australia. Of the 132 model nests deployed and monitored with cameras, 45 (34%) survived the experimental exposure period. Thirty-five (27%) were lost to flooding, 32 (24%) were depredated, nine (7%) buried by sand, seven (5%) destroyed by people, three (2%) failed by unknown causes, and one (1%) was destroyed by a dog. Clutch fate differed substantially among regions, particularly with respect to losses from flooding and predation. 'Topographic' exposure was the main driver of mortality of nests placed close to the drift line near the base of dunes, which were lost to waves (particularly during storms) and to a lesser extent depredation. Predators determined the fate of clutches not lost to waves, with the depredation probability largely influenced by region. Depredation probability declined as nests were backed by higher dunes and were placed closer to vegetation. This study emphasizes the scale at which clutch fate and survival varies within a regional context, the prominence of corvids as egg predators, the significant role of flooding as a source of nest loss, and the multiple trade-offs faced by beach-nesting birds and those that manage them.

Data from: Adaptation to climate change: trade-offs among responses to multiple stressors in an intertidal crustacean

Trade-offs may influence both physiological and evolutionary responses to co-occurring stressors, but their effects on both plastic and adaptive responses to climate change are poorly understood. To test for genetic and physiological trade-offs incurred in tolerating multiple stressors, we hybridized two populations of the intertidal copepod Tigriopus californicus that were divergent for both heat and salinity tolerance. Starting in the F2 generation, we selected for increased tolerance of heat, low salinity, and high salinity in replicate lines. After five generations of selection, heat-selected lines had greater heat tolerance but lower fecundity, indicating an energetic cost to tolerance. Lines selected for increased salinity tolerance did not show evidence of adaptation to their respective environments; however, hypo-osmotic selection lines showed substantial loss of tolerance to hyperosmotic stress. Neither of the salinity selection regimes resulted in diminished heat tolerance at ambient salinity; however, simultaneous exposure to heat and hypo-osmotic stress led to decreased heat tolerance, implying a physiological trade-off in tolerance to the two stressors. When we quantified the transcriptomic response to heat and salinity stress via RNA sequencing, we observed little overlap in the stress responses, suggesting the observed synergistic effects of heat and salinity stress were driven by competing energetic demands, rather than shared stress response pathways.

Data from: Trade-offs between growth rate, tree size and lifespan of mountain pine (Pinus montana) in the Swiss National Park

A within-species trade-off between growth rates and lifespan has been observed across different taxa of trees, however, there is some uncertainty whether this trade-off also applies to shade-intolerant tree species. The main objective of this study was to investigate the relationships between radial growth, tree size and lifespan of shade-intolerant mountain pines. For 200 dead standing mountain pines (Pinus montana) located along gradients of aspect, slope steepness and elevation in the Swiss National Park, radial annual growth rates and lifespan were reconstructed. While early growth (i.e. mean tree-ring width over the first 50 years) correlated positively with diameter at the time of tree death, a negative correlation resulted with lifespan, i.e. rapidly growing mountain pines face a trade-off between reaching a large diameter at the cost of early tree death. Slowly growing mountain pines may reach a large diameter and a long lifespan, but risk to die young at a small size. Early growth was not correlated with temperature or precipitation over the growing period. Variability in lifespan was further contingent on aspect, slope steepness and elevation. The shade-intolerant mountain pines follow diverging growth trajectories that are imposed by extrinsic environmental influences. The resulting trade-offs between growth rate, tree size and lifespan advance our understanding of tree population dynamics, which may ultimately improve projections of forest dynamics under changing environmental conditions.

opencc-zeroDec 2012View details →

Data from: Daily foraging patterns in free-living birds: exploring the predation-starvation trade-off

Daily patterns in the foraging behaviour of birds are assumed to balance the counteracting risks of predation and starvation. Predation risks are a function of the influence of weight on flight performance and foraging behaviours that may expose individuals to predators. Although recent research sheds light on daily patterns in weight gain, little data exist on daily foraging routines in free-living birds. In order to test the predictions of various hypotheses about daily patterns of foraging, we quantified the activity of four species of passerines in winter using radio frequency identification receivers built into supplemental feeding stations. From records of 472,368 feeder visits by tagged birds, we found that birds generally started to feed before sunrise and continued to forage at a steady to increasing rate throughout the day. Foraging in most species terminated well before sunset, suggesting their desired level of energy reserves was being reached before the end of the day. These results support the risk-spreading theorem over a long-standing hypothesis predicting bimodality in foraging behaviour purportedly driven by a tradeoff between the risks of starvation and predation. Given the increased energetic demands experienced by birds during colder weather, our results suggest that birds' perceptions of risk are biased towards starvation avoidance in winter.

Data from: Trade-offs and synergies between bird conservation and wildfire suppression in the face of global change

1. The combined effects of climate change and other factors, such as land use change or fire disturbance, pose daunting challenges for biodiversity conservation worldwide. 2. In this study, we predicted the future effectiveness of the Natura 2000 (N2000), the current network of protected areas (PA) in Europe, at maintaining and representing suitable environmental conditions for a set of 79 bird species between 2000 and 2050 in a fire-prone area strongly affected by land abandonment processes in NE Spain. We then compared PA performance against a set of alternative priority areas for conservation, which take into account fire–vegetation dynamics, selected by using a conservation planning tool (MARXAN). Fire–vegetation dynamics were modelled using a process-based model (MEDFIRE MODEL) under alternative fire management and climate change scenarios. Bird assemblage distributions were predicted using the spatially-explicit species assemblage modelling frameworkSESAMusing distribution models from individual species that hierarchically integrate climate change and wildfire–vegetation dynamics. 3. The amount of suitable environmental conditions within the N2000 network was predicted to fall by around 15%, on average, over the next decades in relation to the initial conditions, but could be partially modulated by fire management policies in the near future. The efficiency of the current PA system was predicted to decrease from 17.4 to 15% over the next decades. However, a more efficient PA system could be achieved with a conservation planning approach that explicitly considers fire–vegetation dynamics and their management. 4. Synthesis and applications: Our findings shed light on: (1) how the current Natura 2000 might still hold an important bird conservation value by 2050; (2) how the relocation of some protected areas could be considered along the next decades to substantially increase bird conservation effectiveness; and (3) how the integration of fire-vegetation dynamics, fire management policies and their objectives within conservation planning can provide 'win-win' solutions for bird conservation and fire prevention in fire-prone abandoned landscapes.