Find research datasets worth reusing

Data from: Experimental evaluation of the robustness of the growth-stress tolerance trade-off within the perennial grass Dactylis glomerata

1. A core tenet of functional ecology is that the vast phenotypic diversity observed in the plant kingdom could be partly generated by a trade- off between the ability of plants to grow quickly and acquire resources in rich environments vs. the ability to conserve resources and avoid mortality under stress. However, experimental demonstrations remain scarce and potentially blurred by phylogenetic constraints in cross-species analyses. Here we experimentally decoupled growth potential and stress survival by applying an off-season stress on contrasting populations of the perennial grass Dactylis glomerata exhibiting a range of seasonal dormancy. 2. Seventeen populations of D. glomerata, originating from a latitudinal gradient from Norway to Morocco, were subjected to three types of dehydration stress: winter frost in Norway, summer drought, and early spring (off-season) drought stress in the south of France. Growth rate, and two leaf traits (leaf width and leaf dry matter content) suspected to be involved in the adaptation to dehydration stress, were monitored under optimal conditions. We quantified plant dehydration survival as the amount of plant recovery after a severe stress. 3. Nordic populations were found to be winter dormant. Winter and summer dormant populations better survived frost and summer drought, respectively. However, no trade-off between growth potential and dehydration survival was detected in non-dormant plants in early spring when dehydration occurred unseasonably for all populations. Furthermore, Mediterranean populations better survived an early spring drought. 4. Our results highlight the importance of assessing plant growth potential as a response to seasonal environmental cues. They suggest that growth potential and stress survival trade-off when plants exhibit seasonal dormancy but can be functionally independent at other seasons. Consequently, the growth-stress survival relationship could be better described as a dynamic linkage rather than a constant and general trade-off. Moreover, leaf trait values, such as thinner and more lignified leaves reflecting drought adaptation, may have contributed to the improved drought-stress survival without resulting in a cost to growth. 5. Further exploration of the growth-stress survival relationship should permit deciphering the suite of plant traits and trait covariations involved in plants' responses to increasing stress.

opencc-zeroDec 2013View details →

Data from: Food supplementation fails to reveal a trade-off between incubation and self-maintenance in female house wrens

Incubating birds must allocate their time and energy between maintaining egg temperature and obtaining enough food to meet their own metabolic demands. We tested the hypothesis that female house wrens (Troglodytes aedon) face a trade-off between incubation and self-maintenance by providing females with supplemental food during incubation. We predicted that food supplementation would increase the amount of time females devoted to incubating their eggs, lower their baseline plasma corticosterone levels (a measure of chronic stress), and increase their body mass, haematocrit (a measure of anaemia), and reproductive success relative to control females. As predicted, food-supplemented females spent a greater proportion of time incubating their eggs than control females. Contrary to expectation, however, there was no evidence that food supplementation significantly influenced female baseline plasma corticosterone levels, body mass, haematocrit, or reproductive success. However, females with high levels of corticosterone at the beginning of incubation were more likely to abandon their nesting attempt after capture than females with low levels. Corticosterone significantly increased between the early incubation and early nestling stages of the breeding cycle in all females. These results suggest that although food supplementation results in a modest increase in incubation effort, it does not lead to significantly lower levels of chronic stress as reflected in lower baseline corticosterone levels. We conclude that female house wrens that begin the incubation period with low levels of plasma corticosterone can easily meet their own nutritional needs while incubating their eggs, and that any trade-off between incubation and self-feeding does not influence female reproductive success under the conditions at the time of our study.

Data from: Predators modify the thermal dependence of life-history trade-offs.

Although life histories are shaped by temperature and predation, their joint influence on the interdependence of life-history traits is poorly understood. Shifts in one life history trait often necessitates shifts in another – structured in some cases by trade-offs – leading to differing life history strategies among environments. The offspring size-number trade-off connects three traits whereby a constant reproductive allocation (R) constrains how the number (O) and size (S) of offspring change. Increasing temperature and size-independent predation decrease size at and time to reproduction which can lower R through reduced time for resource accrual or size-constrained fecundity. We investigated how O, S, and R in a clonal population of Daphnia magna change across their first three clutches with temperature and size-independent predation risk. Early in ontogeny, increased temperature moved O and S along a trade-off curve (constant R) towards fewer larger offspring. Later in ontogeny, increased temperature reduced R in the no-predator treatment through disproportionate decreases in O relative to S. In the predation treatment, R likewise decreased at warmer temperatures but to a lesser degree and more readily traded off S for O whereby the third clutch showed a constant allocation strategy of O vs S with decreasing R. Ontogenetic shifts in S and O rotated in a counterclockwise fashion as temperature increased and more drastically under risk of predation. These results show that predation risk can alter the temperature dependence of traits, and their interactions through trade-offs.

opencc-zeroDec 2016View details →

Data from: Experimental manipulation reveals a trade-off between weapons and testes

Theory predicts a trade-off between sexually-selected weapons used to secure mates and post-copulatory traits used to maximize fertilization success. However, individuals that have a greater capacity to acquire resources from the environment may invest more in both pre- and post-copulatory traits, and trade-offs may not be readily apparent. Here, we manipulate the phenotype of developing individuals to examine allocation trade-offs between weapons and testes in Mictis profana (Hemiptera: Coreidae), a species where the hind legs are sexually selected weapons used in contests over access to females. We experimentally prevented males from developing weapons by inducing them to autotomize their hind legs before the final molt to adulthood. We compared trait expression in this group to males where autotomy was induced in the mid legs, which are presumably not under sexual selection to the same extent. We found males without weapons invested proportionally more in testes mass than those with their mid legs removed. Males that developed to adulthood without weapons did not differ from the mid leg removal group in other traits potentially under pre-copulatory sexual selection, other post-copulatory traits, or naturally selected traits. In addition, a sample of adult males from the same population in the wild revealed a positive correlation between investment in testes and weapons. Our study presents a critical contribution to a growing body of literature suggesting the allocation of resources to pre- and post-copulatory sexual traits is influenced by a resource allocation trade-off and that this trade-off may only be revealed with experimental manipulation.

Data from: Camponotus floridanus ants incur a trade-off between phenotypic development and pathogen susceptibility from their mutualistic Endosymbiont Blochmannia

Various insects engage in microbial mutualisms in which the reciprocal benefits exceed the costs. Ants of the genus Camponotus benefit from nutrient supplementation by their mutualistic endosymbiotic bacteria, Blochmannia, but suffer a cost in tolerating and regulating the symbiont. This cost suggests that the ants face secondary consequences such as susceptibility to pathogenic infection and transmission. In order to elucidate the symbiont's effects on development and disease defence, Blochmannia floridanus was reduced in colonies of Camponotus floridanus using antibiotics. Colonies with reduced symbiont levels exhibited workers of smaller body size, smaller colony size, and a lower major-to-minor worker caste ratio, indicating the symbiont's crucial role in development. Moreover, these ants had decreased cuticular melanisation, yet higher resistance to the entomopathogen Metarhizium brunneum, suggesting that the symbiont reduces the ants' ability to fight infection, despite the availability of melanin to aid in mounting an immune response. While the benefits of improved growth and development likely drive the mutualism, the symbiont imposes a critical trade-off. The ants' increased susceptibility to infection exacerbates the danger of pathogen transmission, a significant risk given ants' social lifestyle. Thus, the results warrant research into potential adaptations of the ants and pathogens that remedy and exploit the described disease vulnerability.

Data from: Trade-offs in female signal apparency to males offer alternative anti-harassment strategies for color polymorphic females

Color polymorphisms are known to influence receiver behavior, but how they affect a receiver's ability to detect and recognize individuals in nature is usually unknown. I hypothesized that polymorphic female damselflies represent an evolutionary stable strategy, maintained by trade-offs between the relative apparency of morphs to male receivers. Using field experiments on Enallagma hageni and focal studies of E. hageni and E. boreale, I tested for the first time the predictions that 1) green heteromorphs and blue andromorphs gain differential protection from sexual harassment via background crypsis and sexual mimicry respectively, and 2) female morphs behaviorally optimize their signal apparency to mate-searching males. First, based on male reactions elicited by females, against a high contrast background the two morphs did not differ in being detected by males and once detected, did not differ in being recognized (eliciting sexual reactions). However, on green ferns, heteromorphs were detected less often (elicited only fly-bys) than andromorphs but once detected, the morphs did not differ in being recognized. In contrast, when perched on a dowel with two male signal distractors, andromorphs were detected less often and once detected, were recognized less often than heteromorphs. Second, in fields where females foraged, andromorphs perched higher on vegetation than heteromorphs, and were more often in the vicinity of males. Neither harassment rates nor evasive behaviors differed between morphs. Males aggregated in high density near shore where solitary females were rare. Equilibrium frequencies of these and other color morphs should reflect the relative ease with which receivers detect and recognize them in the context where they are encountered.

opencc-zeroDec 2013View details →

Data from: Linkage and trade-off in trophic morphology and behavioral performance of birds

1. Bill closing behaviour involves a complex suite of tissue types, kinematics, morphological states and muscle architectural arrangements that has been under the scrutiny of natural selection for millions of years. Hence, an evolutionary shift to specialize in closing force may come at a cost to closing velocity and vice versa. 2. Using field measurements on behavioural performance and morphological data from museum specimens, we tested predictions of the force–velocity trade-off hypothesis in 18 species of North American birds with diverse phylogenetic and ecological backgrounds. 3. Linear models revealed that size and shape are excellent predictors of both bite force and closing velocity. However, taken one at a time, they each have a somewhat unique set of morphological predictors. In-lever length, mandibular depth and bill width comprise the best model of prediction for force, while a combination of out-lever length and total skull length provides the best prediction of closing velocity. Additionally, in our sample, only force is size-dependent. Hence, the predicted trade-off is revealed only after correcting bite force for head size. 4. Various modes of predation and decoupled morphological prediction models for performance suggest that specialization towards one strategy (e.g. increase force) may not necessarily come at a cost to the other. towards one strategy (e.g. increase force) may not necessarily come at a cost to the other.

opencc-zeroDec 2012View details →

Data from: Optimizing the trade-off between spatial and genetic sampling efforts in patchy populations: towards a better assessment of functional connectivity using an individual-based sampling scheme

Genetic data are increasingly used in landscape ecology for the indirect assessment of functional connectivity, i.e. the permeability of landscape to movements of organisms. Among available tools, matrix correlation analyses (e.g. Mantel tests or mixed models) are commonly used to test for the relationship between pairwise genetic distances and movement costs incurred by dispersing individuals. When organisms are spatially clustered, a population-based sampling scheme (PSS) is usually performed, so that a large number of genotypes can be used to compute pairwise genetic distances on the basis of allelic frequencies. Because of financial constraints, this kind of sampling scheme implies a drastic reduction in the number of sampled aggregates, thereby reducing sampling coverage at the landscape level. We used matrix correlation analyses on simulated and empirical genetic datasets to investigate the efficiency of an individual-based sampling scheme (ISS) in detecting isolation-by-distance and isolation-by-barrier patterns. Provided that pseudo-replication issues are taken into account (e.g. through restricted permutations in Mantel tests), we showed that the use of inter-individual measures of genotypic dissimilarity may efficiently replace inter-population measures of genetic differentiation: the sampling of only three or four individuals per aggregate may be sufficient to efficiently detect specific genetic patterns in most situations. The ISS proved to be a promising methodological alternative to the more conventional PSS, offering much flexibility in the spatial design of sampling schemes and ensuring an optimal representativeness of landscape heterogeneity in data, with few aggregates left unsampled. Each strategy offering specific advantages, a combined use of both sampling schemes is discussed.

Data from: Trade-offs in parasitism efficiency and brood size mediate parasitoid coexistence, with implications for biological control of the invasive emerald ash borer

1. Parasitoids often are selected for use as biological control agents because of their high host specificity, yet such host specificity can result in strong interspecific competition. Few studies have examined whether and how various extrinsic factors (such as parasitism efficiency, i.e. the ability to optimize host-finding attack rates) influence the outcome of competition between parasitoids, even though they could have profound effects on the implementation of classical biological control programmes. 2. To determine the potential influence of extrinsic competition and coexistence on host suppression efficacy, we compared parasitism by two larval parasitoids (Tetrastichus planipennisi and Spathius galinae) of the invasive emerald ash borer (EAB) Agrilus planipennis, under different host densities, parasitoid densities, host plant sizes and parasitoid–host ratios. 3. Spathius galinae had significantly higher parasitism efficiency (≈4 times), but significantly lower brood size (>6 times) than that of T. planipennisi. The attack rates of hosts increased significantly with parasitoid density, whereas host density did not significantly affect multiparasitism. The parasitism rate of T. planipennisi on small host logs was significantly higher than that on large logs, while host plant (log) size had no significant impact on S. galinae parasitism. 4. The multiparasitism rate was rather low regardless of host log size and parasitoid/host density, indicating that intrinsic competition between the two species of parasitoids might seldom occur in the field. The two species of parasitoids could therefore coexist in the same habitat, and any adverse effects on the suppression of EAB populations caused by competitive behaviour between the two species of parasitoids would likely be negligible. 5. Synthesis and applications. Our findings suggest that introducing multiple species of parasitic natural enemies could be feasible for management of invasive species, but it is important to examine multiple extrinsic factors simultaneously when evaluating interspecific competition between them. Among these different extrinsic factors, we found that coexistence between parasitoids can be mediated by trade-offs in their parasitism efficiency and brood sizes. Thus, the differences in life-history traits of natural enemies could be used to select among biological control agents being considered for releases.

opencc-zeroJul 2019View details →

Data from: A functional trade-off between trophic adaptation and parental care predicts sexual dimorphism in cichlid fish

Although sexual dimorphism is widespread in nature, its evolutionary causes often remain elusive. Here we report a case where a sex-specific conflicting functional demand related to parental care but not to sexual selection explains sexual dimorphism in a primarily trophic structure, the gill rakers of cichlid fishes. More specifically, we examined gill raker length in a representative set of cichlid fish species from Lake Tanganyika featuring three different parental care strategies: (i) uni-parental mouthbrooding, whereby only one parental sex incubates the eggs in the buccal cavity; (ii) bi-parental mouthbrooding, whereby both parents participate in mouthbrooding; and (iii) nest guarding without any mouthbrooding involved. As predicted from these different parental care strategies, we find sexual dimorphism in gill raker length to be present only in uni-parental mouthbrooders, but neither in bi-parental mouthbrooders nor in nest guarders. Moreover, variation in the extent of sexual dimorphism among uni-parental mouthbrooders appears to be related to trophic ecology. Overall, we present a so far unrecognised scenario for the evolution of sexual dimorphism that is not related to sexual selection or initial niche divergence between sexes. Instead, sexual dimorphism in gill raker length in uni-parental mouthbrooding cichlid fish appears to be the consequence of a sex-specific functional trade-off between a trophic function present in both sexes, and a reproductive function present only in the brooding sex.

opencc-zeroDec 2018View details →

Data from: Resource allocation trade-offs and the loss of chemical defences during apple domestication

Background and Aims: Most crops have been dramatically altered from their wild ancestors with the primary goal of increasing harvestable yield. A long-held hypothesis is that increased allocation to yield has reduced plant investment in defence and resulted in crops that are highly susceptible to pests. However, clear demonstrations of these trade-offs have been elusive due to the many selective pressures that occur concurrently during crop domestication. Methods: To provide a robust test of whether increased allocation to yield can alter plant investment in defence, this study examined fruit chemical defence traits and herbivore resistance across 52 wild and 56 domesticated genotypes of apples that vary >26-fold in fruit size. Ninety-six phenolic metabolites were quantified in apple skin, pulp and seeds, and resistance to the codling moth was assessed with a series of bioassays. Key Results: The results show that wild apples have higher total phenolic concentrations and a higher diversity of metabolites than domesticated apples in skin, pulp and seeds. A negative phenotypic relationship between fruit size and phenolics indicates that this pattern is driven in part by allocation-based trade-offs between yield and defence. There were no clear differences in codling moth performance between wild and domesticated apples and no overall effects of total phenolic concentration on codling moth performance, but the results did show that codling moth resistance was increased in apples with higher phenolic diversity. The concentrations of a few individual compounds (primarily flavan-3-ols) also correlated with increased resistance, primarily driven by a reduction in pupal mass of female moths. Conclusions: The negative phenotypic relationship between fruit size and phenolic content, observed across a large number of wild and domesticated genotypes, supports the hypothesis of yield–defence trade-offs in crops. However, the limited effects of phenolics on codling moth highlight the complexity of consequences that domestication has for plant–herbivore interactions. Continued studies of crop domestication can further our understanding of the multiple trade-offs involved in plant defence, while simultaneously leading to novel discoveries that can improve the sustainability of crop production.

opencc-zeroDec 2019View details →

Data from: Population variation in density-dependent growth, mortality and their trade-off in a stream fish

<ol> <li>Important variation in the shape and strength of density-dependent growth and mortality is observed across animal populations. Understanding this population variation is critical for predicting density-dependent relationships in natural populations, but comparisons among studies are challenging as studies differ in methodologies and in local environmental conditions.</li> <li>Consequently, it is unclear whether: (1) the shape and strength of density-dependent growth and mortality are population-specific; (2) the potential trade-off between density-dependent growth and mortality differs among populations; and (3) environmental characteristics can be related to population differences in density-dependent relationships.</li> <li>To elucidate these uncertainties, we manipulated the density (0.3-7 fish/m2) of young-of-the-year brook trout (Salvelinus fontinalis) simultaneously in three neighboring populations in a field experiment in Newfoundland, Canada. Within each population, our experiment included both spatial (three sites per stream) and temporal (three consecutive summers) replication.</li> <li>We detected temporally consistent population variation in the shape of density-dependent growth (negative linear and negative logarithmic), but not for mortality (positive logarithmic). The strength of density-dependent growth across populations was reduced in sections with a high percentage of boulder substrate, whereas density-dependent mortality increased with increasing flow, water temperature, and more acidic pH. Neighbouring populations exhibited different mortality-growth trade-offs: the ratio of mortality-to-growth increased linearly with increasing density at different rates across populations (up to 4-fold differences), but also increased with increasing temperature.</li> <li>Our results are some of the first to demonstrate temporally consistent, population-specific density-dependent relationships and trade-offs at small spatial scales that match the magnitude of interspecific variation observed across the globe. Furthermore, key environmental characteristics explain some of these differences in predictable ways. Such population differences merit further attention in models of density-dependence and in science-based management of animal populations.</li> </ol>

Data from: The trade-off between clutch size and egg mass in tree swallows (Tachycineta bicolor) is modulated by female body mass

Egg production is a costly component of reproduction for female birds in terms of energy expenditure and maternal investment. Because resources are typically limited, clutch size and egg mass are expected to be constrained, and this putative trade-off between offspring number and size is at the core of life history theory. Nevertheless, empirical evidence for this trade-off is equivocal at best, as individual heterogeneity in resource acquisition and allocation may hamper the detection of the negative correlation between egg number and mass within populations. Here, we investigated how female body mass and landscape composition influences clutch size, egg mass, and the relationship between these two traits. To do so, we fitted linear mixed models using data from tree swallows Tachycineta bicolor breeding in a network of 400 nestboxes located along a gradient of agricultural intensity between 2004 and 2011. Our dataset comprised 1463 broods for clutch size analyses and 4371 eggs (from 847 broods laid between 2005–2008) for egg mass analyses. Our results showed that agricultural intensity negatively impacted clutch size, but not egg mass nor the relationship between these two traits. Female mass, on the other hand, modulated the trade-off between clutch size and egg mass. For heavier females, both traits increased jointly, without evidence of a trade-off. However, for lighter females, there was a clear negative relationship between clutch size and egg mass. This work shows that accounting for individual heterogeneity in body mass allows the detection of a clutch size/egg mass trade-off that would have remained undetected otherwise. Identifying habitat and individual effects on resource allocation towards reproductive traits may help bridging the gap between predictions from theory and empirical evidence on life history trade-offs.

opencc-zeroDec 2019View details →

Data from: Extra-pair mating opportunities mediate parenting and mating effort trade-offs in a songbird

In socially monogamous species with bi-parental care, males may face a trade-off between providing parental care and pursuing extra-pair matings. The "parenting-mating trade-off" hypothesis predicts that high-quality males – who have greater potential to gain extra-pair matings, e.g. larger males usually win the competition for extra-pair mating – should reduce parental care and spend more time looking for extra-pair matings. However, the trade-off between parenting and mating efforts may be complicated by variation in the availability of extra-pair mating opportunities. By using field data of hair-crested drongos (Dicrurus hottentottus), a species exhibiting bi-parental incubation behavior, collected in central China from 2010 to 2017, we tested whether the potential negative relationship between male quality and paternal care was dependent on the number of nearby fertile females. We found that male drongos mainly seek extra-pair matings during the incubation period and high-quality individuals (males with longer tarsi) are more likely to sire extra-pair offspring. In agreement with the "parenting-mating trade-off" hypothesis, high-quality males incubated less by recessing longer between incubation bouts. However, this was only the case when sufficient fertile females nearby for extra-pair mating opportunities. Females compensated for reduced male care, but this was independent of male quality. This suggests that the reduction in care by high-quality males might be a direct response to extra-pair mating opportunities rather than facilitated by differential allocation of females. Our results indicate that individual quality and available mating opportunities may shape the optimal trade-off between parental care and seeking additional matings for males.

Data from: Sexual fidelity trade-offs promote regulatory variation in the prairie vole brain

Individual variation in social behavior seems ubiquitous, but we know little about how it relates to brain diversity. Among monogamous prairie voles, levels of vasopressin receptor (encoded by the gene avpr1a) in brain regions related to spatial memory predict male space use and sexual fidelity in the field. We find that trade-offs between the benefits of male fidelity and infidelity are reflected in patterns of territorial intrusion, offspring paternity, avpr1a expression, and the evolutionary fitness of alternative avpr1a alleles. DNA variation at the avpr1a locus includes polymorphisms that reliably predict the epigenetic status and neural expression of avpr1a, and patterns of DNA diversity demonstrate that avpr1a regulatory variation has been favored by selection. In prairie voles, trade-offs in the fitness consequences of social behaviors seem to promote neuronal and molecular diversity.

Data from: Trade-offs in berry production and biodiversity under prescribed burning and retention regimes in Boreal forests

1. Green tree retention and prescribed burning are practices used to mitigate negative effects of forestry. Beside their effects on biodiversity, these practices should also promote non-timber forest products (NTFPs). We assessed: (1) how prescribed burning and tree retention influence NTFPs by examining production of bilberry Vaccinium myrtillus and cowberry; Vaccinium vitis-idaea (2) if there are synergies or trade-offs in the delivery of these NTFPs in relation to delivery of species richness, focusing on five groups of forest dwelling species. 2. We used a long-term experiment located in eastern Finland with three different harvesting treatments: clearcut-logging, logging with retention patches and unlogged, which were combined with or without prescribed burning. Eleven years after the treatment application, we scored plant cover and berry production in different microhabitats within these treatments, while species richness data for five species groups (ground-layer lichens and bryophytes, vascular plants, saproxylic beetles, pollinators – here bees and hoverflies) were collected at the stand level. 3. Logging favoured cowberry production, particularly for plants growing in the vicinity of stumps. Logging was detrimental for cover and berry production of bilberry. Retention mitigated these negative effects slightly, but cover and berry production were still substantially lower compared to unlogged forests. Prescribed burning increased cowberry production in retention patches and in unlogged forest. Bilberry production decreased with burning, except in unlogged forest where the effect was neutral. 4. No single management treatment simultaneously favoured all values - NTFPs and richness - and trade-offs among values were common. Only bilberry production and beetle diversity were higher under retention forestry, or in unlogged stands, compared to logged stands. Prescribed burning favoured many values when performed in combination with retention forestry, or in unlogged stands, but different treatment combinations favoured different species groups. 5. Synthesis and applications. Our results demonstrate that widely-applied conservation practices in managed forests are unlikely to benefit all ecosystem values everywhere. If high multi-functionality is desired, managing at a landscape scale, countering the local trade-offs among values, may be more appropriate than the stand scale conservation practices commonly practiced today.

opencc-zeroDec 2015View details →

Data from: Trade-offs in an ant–plant–fungus mutualism

Species engaged in multiple, simultaneous mutualisms are subject to trade-offs in their mutualistic investment if the traits involved in each interaction are overlapping, which can lead to conflicts and affect the longevity of these associations. We investigate this issue via a tripartite mutualism involving an ant plant, two competing ant species and a fungus the ants cultivate to build galleries under the stems of their host plant to capture insect prey. The use of the galleries represents an innovative prey capture strategy compared with the more typical strategy of foraging on leaves. However, because of a limited worker force in their colonies, the prey capture behaviour of the ants results in a trade-off between plant protection (i.e. the ants patrol the foliage and attack intruders including herbivores) and ambushing prey in the galleries, which has a cascading effect on the fitness of all of the partners. The quantification of partners' traits and effects showed that the two ant species differed in their mutualistic investment. Less investment in the galleries (i.e. in fungal cultivation) translated into more benefits for the plant in terms of less herbivory and higher growth rates and vice versa. However, the greater vegetative growth of the plants did not produce a positive fitness effect for the better mutualistic ant species in terms of colony size and production of sexuals nor was the mutualist compensated by the wider dispersal of its queens. As a consequence, although the better ant mutualist is the one that provides more benefits to its host plant, its lower host–plant exploitation does not give this ant species a competitive advantage. The local coexistence of the ant species is thus fleeting and should eventually lead to the exclusion of the less competitive species.

Data from: Reproductive effort and success of males in scramble competition polygyny: evidence for trade-offs between foraging and mate-search

1. Patterns of male reproductive allocation provide insight into life-history characteristics. The trade-offs associated with resource and female group defense are well-defined. However, less is understood about trade-offs in species that practice scramble-competition polygyny, where successful strategies may favor competitive mate-searching rather than contest competition and fighting. 2. White-tailed deer (Odocoileus virginianus) practice scramble-competition polygyny where solitary males search for and assess receptivity of females scattered across the landscape. Physically mature males are expected to do most of the breeding because of the high energetic costs of reproduction and high social status. However, young males may collectively sire one-third of offspring. To gain a better understanding of trade-offs associated with scramble-competition polygyny, we quantified metrics associated with reproductive effort and success. 3. We quantified changes in body mass of harvested males, energetic costs of locomotion based on movements of GPS radio-collared males, and timing of reproduction via temporal genetic parentage assignments. 4. Young males (1.5 and 2.5 years old) sired offspring, but their mating success was mainly limited to peak rut, when most females were in estrus. Furthermore, multiple paternity was common, indicating opportunistic reproduction. Reproductive effort, indexed by body mass loss, was highest in prime-age males (5.5-6.5 years old). Surprisingly, young and post-prime males also exhibited significant body mass loss, indicative of investment in reproductive effort. Movement rates increased 2 to 4-fold during rut as a function of mate-search activities, but cost of locomotion would cause only about one-third of observed body mass loss. Because males are capital breeders, we infer most of body mass loss is due to reduced foraging. 5. In scramble-competition polygyny, the repeated location of potential mates and assessment of their estrous status appear to be important constituents of male mating strategies. Therefore mating success may be influenced by time management and spatial memory, and not based solely on social dominance. Thus, reproductive effort should be greater for individuals capable of reducing time foraging. For those that cannot, opportunistic mating opportunities may arise when operative adult sex ratios are low. Our analyses reveal valuable insight into the trade-offs associated with scramble-competition polygyny.

opencc-zeroDec 2016View details →

Data from: Climatic factors shape plastic trade-offs in the polyphenic black scavenger fly Sepsis thoracica (Diptera: Sepsidae)

Aim: Trade-offs allow individuals to optimize their fitness by tailoring the investment into different traits to variable environmental conditions, such as along geographic gradients. Trade-offs thus can help in adjusting to changing thermal and insolation profiles, especially in small ectotherms, whose body temperature typically follows environmental temperatures closely. Two traits usually involved in latitudinal adaptation are body size and melanism. Since both traits are costly, individuals need to optimize investment into each trait. Here we studied how environmental factors influence this trade-off in the short and long term. Location: Europe Methods: We raised flies from 15 latitudinal populations at three constant temperatures in a laboratory common garden to differentiate plastic and evolutionary responses to temperature. We further analysed how the different insolation components of the populations' habitats influenced the evolution of the trade-off. Results: Male Sepsis thoracica (Diptera: Sepsidae) feature a sigmoid relationship between melanism and body size, defining two strikingly different male morphs: obsidian (small and black) and amber (large and orange). This relationship was altered by the developmental temperature, documenting its plasticity. The relationship further evolved across populations in response to the environmental characteristics of their habitat, notably temperature, insolation and UV radiation, suggesting that plasticity also has an underlying genetic basis. Nevertheless, melanism, but not body size, merely slightly increased with latitude. Main Conclusions: As the plastic and evolutionary responses of the relationship to temperature differed, plasticity does not necessarily follow the direction of evolution of this trade-off, but rather adds to it. Our study evinces the role of several environmental factors in shaping the evolution of a plastic melanism – body size relationship defining a rare male polymorphism in temperate sepsid flies.