Variation In Resource Abundance Research Articles

The structure of Congolese shrew ensembles: competition and spatial variation in resource abundance

The structure of Congolese shrew ensembles: competition and spatial variation in resource abundance

Influences of submerged plant collapse on diet composition, breadth, and overlap among four crane species at Poyang Lake, China

BackgroundInterannual variation in resource abundance has become more unpredictable, and food shortages have increasingly occurred in the recent decades. However, compared to seasonal fluctuations in resource abundance, the influences of interannual variation in resource abundance on the dietary niches of consumers remain poorly understood. Poyang Lake, China, is a very important wintering ground for the globally endangered Siberian Crane (Leucogeranus leucogeranus), White-naped Crane (Grus vipio), and Hooded Crane (G. monacha), as well as the non-endangered Eurasian Crane (G. grus). Tubers of Vallisneria spp., the dominant submerged macrophytes at Poyang Lake, is an important food for cranes. Nevertheless, submerged macrophytes have experienced serious degradation recently. In this study, we used metabarcoding technology to explore the consequences of Vallisneria tuber collapse on the diet compositions, breadths, and overlaps of the four crane species based on fecal samples collected in winter 2017 (a year with tuber collapse) and winter 2018 (a year with high tuber abundance).ResultsCompared to previous studies, our study elucidates crane diets in an unprecedented level of detail. Vallisneria tubers was confirmed as an important food source of cranes. Surprisingly, the grassland plant Polygonum criopolitanum was also found to be an important food source in the feces of cranes. Agricultural fields were important foraging sites for Siberian Cranes, White-naped Cranes, and Hooded Cranes, providing foods that allowed them to survive in winters with natural food shortages. However, the three crane species preferred natural wetlands to agricultural fields when the abundance of natural foods was high. The abundance of Vallisneria tubers, and probably P. criopolitanum, greatly influenced the dietary compositions, breadths and overlap of cranes. During periods of preferred resource shortage, White-naped Cranes and Hooded Cranes widened their dietary niches, while Siberian Cranes maintained a stable niche width. The dietary niche overlap among crane species increased substantially under conditions of plentiful preferred food resources.ConclusionsOur study emphasizes the superior quality of natural wetlands compared to agricultural fields as foraging habitats for cranes. To provide safer and better foraging areas for cranes, it is urgent to restore the submerged plants at Poyang Lake. While high dietary niche overlap is often interpreted as intense interspecific competition, our study highlights the importance of taking food abundance into account.

Genetic relatedness and space use in two populations of striped hyenas (Hyaena hyaena)

Abstract Surprising social complexity and variability have recently been documented in several mammalian species once believed to be strictly solitary, and variation in resource abundance may drive this variation in sociality. Wagner et al. (Wagner, A. P., S. Creel, L. G. Frank, and S. T. Kalinowski. 2007. Patterns of relatedness and parentage in an asocial, polyandrous striped hyena population. Molecular Ecology 16:4356–4369) reported unusual space-use patterns among female striped hyenas (Hyaena hyaena) in central Kenya, where pairwise relatedness among females increased with the geographic distance separating them. The authors suggested that this pattern, very rare among mammals, might reflect attempts by females to avoid competition with close relatives for scarce resources in areas of range overlap. Here, we compare those data to new data, documenting genetic relatedness and space use in a previously unstudied wild population of striped hyenas in southern Kenya. We tested hypotheses suggesting that resource abundance and population density affect patterns of genetic relatedness and geographic distance in this species. Our results suggest that higher per capita prey density results in relaxed competition for food, and greater social tolerance among female striped hyenas. A hypothesis suggesting lower population density in the southern population was not supported. Relaxed resource competition also may lead to female–female cooperation in the southern population; we documented for the first time behavioral evidence of den sharing by adult female striped hyenas. Our data indicate that different populations of this little-studied species exhibit behavioral plasticity; in this case, markedly different space-use patterns and patterns of spatial relatedness under different ecological conditions.

Female breeding dispersal in wolverines, a solitary carnivore with high territorial fidelity

Individuals’ fidelity to an area provides insight into the stability of the spatial and temporal organisation of animals. Territorial fidelity is often influenced by reproductive success, age, the dispersion and predictability of resources, and intraspecific competition. We examined between-year territorial fidelity in wolverines (Gulo gulo), using location data from 47 individuals collected during 1993–2013 in northern Sweden, to assess the stability of the spatial organisation of this solitary carnivore. For females, we also determined residency status from 1 year to the next. The study population is characterized by a stable distribution of resident individuals, with both males and females showing higher fidelity at the total territory level compared to more intensively used core areas. In 86% of the yearly residency status estimates (n = 122), the female remained stationary. In the remaining 14% of the cases, females either vacated their territory (8% of residency statuses), or expanded into a neighbouring territory (6% of residency statuses). We documented six cases of breeding dispersal, representing one of the few known cases of breeding dispersal in long-lived large mammals. We suggest that this high territorial fidelity is enabled by wolverines’ caching and scavenging behaviours, which buffer the unpredictable and large spatiotemporal variation in resource abundance in this low-productivity area. Breeding dispersal may occur due to competition for high-quality territories in this saturated population, where females are forced to abandon their territory by competitors or bequeath territories to offspring. This study further highlights the complexity of the social and spatial dynamics for solitary carnivores.

Season-modulated responses of Neotropical bats to forest fragmentation.

Seasonality causes fluctuations in resource availability, affecting the presence and abundance of animal species. The impacts of these oscillations on wildlife populations can be exacerbated by habitat fragmentation. We assessed differences in bat species abundance between the wet and dry season in a fragmented landscape in the Central Amazon characterized by primary forest fragments embedded in a secondary forest matrix. We also evaluated whether the relative importance of local vegetation structure versus landscape characteristics (composition and configuration) in shaping bat abundance patterns varied between seasons. Our working hypotheses were that abundance responses are species as well as season specific, and that in the wet season, local vegetation structure is a stronger determinant of bat abundance than landscape‐scale attributes. Generalized linear mixed‐effects models in combination with hierarchical partitioning revealed that relationships between species abundances and local vegetation structure and landscape characteristics were both season specific and scale dependent. Overall, landscape characteristics were more important than local vegetation characteristics, suggesting that landscape structure is likely to play an even more important role in landscapes with higher fragment‐matrix contrast. Responses varied between frugivores and animalivores. In the dry season, frugivores responded more to compositional metrics, whereas during the wet season, local and configurational metrics were more important. Animalivores showed similar patterns in both seasons, responding to the same group of metrics in both seasons. Differences in responses likely reflect seasonal differences in the phenology of flowering and fruiting between primary and secondary forests, which affected the foraging behavior and habitat use of bats. Management actions should encompass multiscale approaches to account for the idiosyncratic responses of species to seasonal variation in resource abundance and consequently to local and landscape scale attributes.

Costs and benefits of reproducing under unfavorable conditions: an integrated view of ecological and physiological constraints in a cerrado shrub

Disentangling the relative importance of biotic and abiotic constraints in plant reproduction is a major challenge in reproductive ecology. Here, we tested the ‘resource limitation hypothesis’ that predicts a high-level ovule abortion under resource scarcity; the ‘flowering displacement hypothesis’ that predicts low levels of pollen limitation driven by relaxed competition for pollinators; and the ‘herbivory escape hypothesis’ that predicts low impact by natural enemies during unfavorable conditions. We followed reproductive phenology, measured the seasonal variation in resource abundance, and calculated initial ovule budgets to estimate the relative importance of each limiting factor on final reproductive output. Ovule fate was determined of ovules in different positions within the pods, and a germination experiment was conducted to identify bottlenecks at the germination stage. Despite marked decreases in resource availability during the dry season, reproduction consistently occurred during mid-to-late dry season. Destruction by natural enemies and abortion were the most likely ovule fates, with only 2.2 % of flower buds converted into ripe fruits. Ovule fates were not random along fruit positions, with higher likelihood of well-formed seeds in fruit tips and higher likelihood of ovule abortion and non-fertilized ovules near the fruit bases. The benefits derived from flowering displacement to the dry season include reduced competition for pollinators and synchronization of seedling establishment with the onset of the rainy season. However, we found no support for the herbivory escape hypothesis. We argue that a cost–benefit approach is a useful framework to understand the evolutionary ecology of phenological strategies in seasonal environments.

Linking lab activity with growth and movement in the wild: explaining pace-of-life in a trout stream

Theory suggests that consistent individual differences in activity are linked to life history where high activity is associated with rapid growth, high dispersal tendency, and low survival (the pace-of-life syndrome hypothesis). We addressed this influential hypothesis by combining behavioral studies with fine-scale positional scoring in nature, estimating how individual movement strategies in brown trout ( Salmo trutta ) associate with fitness correlates (growth and survival) in the wild. Initial dispersal in the wild was positively related to the laboratory activity. Moreover, the growth of individuals with high laboratory activity decreased with increasing home range size, whereas the growth of individuals with lower laboratory activity increased slightly with increasing home range size. Survival in the wild was not associated with laboratory activity. Our results do not support the original pace-of-life syndrome hypothesis. As an alternative explanation, we suggest that the growth of individuals adopting a high-activity strategy is more sensitive to variation in resource abundance (indicated by home range size) than the fitness individuals adopting a more passive strategy.

The seasonal dynamic of ant‐flower networks in a semi‐arid tropical environment

1. Several studies have recently focused on the structure of ecological networks involving ants and plants with extrafloral nectaries; however, little is known about the effects of temporal variation in resource abundance on the structure of ant–plant networks mediated by floral nectar.2. In this study, it was evaluated how strong seasonality in resource availability in a semi‐arid tropical environment affects the structure of ant–flower networks. We recorded ants collecting floral nectar during two seasons (from December 2009 to January 2013): dry and green seasons. Then, we built interaction networks for flower‐visiting ants in the Brazilian Caatinga separately for each combination of transect and season.3. In general, strong seasonality directly influenced patterns of ant–flower interactions and the overall complexity of these ecological networks. During the dry season, networks were more connected, less modular, and exhibited greater niche overlap of flower‐visiting ants than during the green season. Moreover, resource utilisation by ants during the dry season tended to be more aggregated. These findings indicate that during the dry season, ant species tended to share many resource bases, probably owing to lower overall resource availability during this season. Species composition of the ant network component was highly season specific; however, a central core of highly generalised ants was present during both seasons.4. The stability of this central core between seasons could strongly affect the ecological and evolutionary dynamics of these interaction networks. This study contributes to the understanding of the structure and dynamics of ant‐flower interactions in extremely seasonal environments.

Differential effects of food availability and nest predation risk on avian reproductive strategies

Spatial and temporal variation in resource abundance and predation risk can favor the evolution of phenotypic plasticity as a means of tracking changing environments. However, because food abundance and predation risk often covary in nature, few studies have separated their effects or tested whether different phenotypic traits respond to the same sources of environmental variation. We investigated patterns of parental investment and behavior over a 7-year period in 2 island populations of orange-crowned warblers (Oreothlypis celata) that showed little genetic divergence but experienced dramatic temporal variation in rainfall and spatial variation in nest predation risk. The amount of rainfall in each year was correlated with food abundance, and birds on both islands initiated breeding earlier and laid larger clutches in wetter years. In contrast, the rate at which parents visited their nests was not affected by rainfall but was negatively correlated with nest predation risk both within and between islands. Our results suggest that although the effects of food availability and nest predation have been viewed as mutually exclusive drivers of entire suites of life-history and behavioral traits, these traits can differ in their sensitivity to resource abundance or mortality risk, and traits that are often correlated can be decoupled under appropriate environmental conditions.

Seasonal Variation in Resource Abundance and Anatomically Modern Human Adaptations: The Blue Highways Project, NW Ethiopia

Seasonal Variation in Resource Abundance and Anatomically Modern Human Adaptations: The Blue Highways Project, NW Ethiopia

Seasonal differences in population-, ensemble- and community-level responses of bats to landscape structure in Amazonia

The amount (composition) and spatial arrangement (configuration) of forest patches in fragmented landscapes influence the accessibility, as well as the abundance and diversity of resources available to bats. Moreover, tropical fruit and insect abundance differ seasonally in response to changes in precipitation, and many bats in the family Phyllostomidae employ seasonal reproductive strategies. Because reproductive activities involve constraints on time and energy as well as increased nutritional demands, foraging behavior and home range size may differ between wet and dry seasons. Nonetheless, seasonal variation in response to landscape structure by bats has not been examined previously. Consequently, population-, ensemble- and assemblage-level responses of phyllostomids to landscape composition and configuration were quantified separately during the wet and dry season at three circular focal scales (1, 3 and 5 km radii) for 14 sites in fragmented lowland Amazon forest. Responses to landscape characteristics were scale-dependent, species-specific, and seasonal. Abundances of frugivores responded to landscape composition in the dry season and to landscape configuration in the wet season. Conversely, abundances of animalivores responded to landscape configuration in the dry season and to landscape composition in the wet season. Divergent responses to landscape structure between seasons suggest that variation in resource abundance and diversity play a significant role in structuring population-, ensemble- and assemblage-level patterns. As such, considerations of the effects of dietary flexibility and reproductive constraints on foraging strategies and habitat use may be important when designing management plans that successfully promote long-term persistence of biodiversity in fragmented landscapes.

Agent-based and multi-agent simulations: coming of age or in search of an identity?

The promise of agent-based for explicating properties of social systems has not yet been fully realized. Agent models sometimes provide only a veneer of, rather than substantive engagement with, social behavior. The problem will be illustrated with Axelrod's model for evolution of ethnocentrism (a biological model) versus Schelling's model for spatial segregation based on preferences (a cultural model). The examples show the need to incorporate both the biological and cultural basis for behavior through a schema that includes behavior based on cultural/cognitive processing of information and behavior based on biological/cognitive processing of information. An example of an agent-based model that implements decision making in this manner is discussed. The model accounts for heterogeneity in behavior outcomes and leads to two main predictions: (1) small scale, hunter-gatherer societies in resource scarce environments will have stable adaptations less affected by variation in resource abundance in comparison to groups in resource rich regions where inter-group conflict is more likely and (2) the relationship between community size, population size and administrative complexity will have two distinct patterns, one for patrilineally organized societies and the other for matrilineally organized societies. Both predictions have been verified empirically.

Energetic costs of male reproduction in a scramble competition mating system

1. The assumption that the primary limitations on reproductive success differ between the sexes is inherent in traditional sexual selection theory. Although the energy that can be allocated to reproduction is assumed to be the main limitation to females, the ability to attract and defend oestrous females is assumed to be the primary limitation to males. 2. Estimates of the energetic costs of reproduction in male mammals are, however, limited and have largely been obtained from sexually dimorphic species exhibiting female defence mating systems. These studies often reveal that the energetic cost of male reproduction is similar to or even exceeds that of females, and therefore challenge long-held assumptions of inter-sexual reproductive limitations, but their generality is little known. 3. We coupled measurements of energy expenditure with detailed behavioural observations of reproductive male North American red squirrels (Tamiasciurus hudsonicus). This species displays minimal sexual dimorphism and exhibits a scramble competition mating system, under which sexual selection favours enhanced mate searching effort by males. 4. We conducted the study over 2 years characterized by a substantial variation in upcoming natural food availability and across two study populations that experienced either natural food abundance or an ad libitum food-supplementation to investigate the influence of resource availability on male reproductive energy expenditure. 5. Under natural conditions, mean energy expenditure of males across the 2 years was high, approximating that of females during lactation. Furthermore, in the anticipation of high upcoming natural food availability and resultant offspring survival, expenditure approximately doubled (from 290 +/- 7 to 579 +/- 73 kJ day(-1)). When current food availability (and consequently the density of receptive females) was experimentally elevated, males displayed the highest levels of energy expenditure we recorded (873 +/- 98 kJ day(-1)). 6. Our results provide compelling evidence that the energy available for reproductive allocation places a strong limitation on reproduction in male North American red squirrels and contribute to previous work suggesting that high and limiting energetic costs of male reproduction may be a general feature of mammalian reproduction.

High niche overlap between two successfully coexisting pairs of Lake Malawi cichlid fishes

Many species in high-diversity assemblages appear to coexist in similar ecological niches. It has been proposed that interspecific resource partitioning in these assemblages may only occur during periods of resource scarcity. We tested this hypothesis by measuring resource abundance, dietary overlap, foraging rate, and territoriality in a Lake Malawi rock cichlid assemblage over a period of 1 year. Our study examined two pairs of morphologically similar species, with each pair comprising one native species and one invader species that has successfully established after being translocated from another region of the lake. All four species changed their diet and foraging rate in response to seasonal variation in resource abundance. However, dietary overlap within both species pairs remained high in all seasons and was not influenced by resource availability. Similarly, territoriality did not decline during periods of low resource availability, suggesting no decrease in the strength of interspecific competition. These data suggest that these species pairs are successfully coexisting despite substantial niche overlap during resource scarcity. Thus, the coexistence of species within this radiation may not depend on the evolution of divergent resource use patterns.

Maternal effects and range expansion: a key factor in a dynamic process?

Species that depend on ephemeral habitat often evolve distinct dispersal strategies in which the propensity to disperse is closely integrated with a suite of morphological, behavioural and physiological traits that influence colonizing ability. These strategies are maintained by natural selection resulting from spatial and temporal variation in resource abundance and are particularly evident during range expansion. Yet the mechanisms that maintain close alignment of such strategies with resource availability, integrate suites of dispersal traits and generate variability in dispersal propensity are rarely known. Breeding females can influence offspring phenotype in response to changes in current environmental conditions, making maternal effects uniquely suited to bridge fluctuations in resource abundance in the maternal generation and variation in offspring dispersal ability. Western bluebirds' (Sialia mexicana) dependence on nest cavities--an ephemeral resource--has led to the evolution of two distinct dispersal phenotypes: aggressive males that disperse and non-aggressive males that remain philopatric and cooperate with their relatives. Over the last 40 years, western bluebirds rapidly expanded their geographical range, providing us with an opportunity to test, in newly established populations, the importance of maternal effects for generating variability in dispersal propensity. Here, I show that, under variable resource conditions, breeding females group offspring of different competitive ability in different positions in the egg-laying order and, consequently, produce aggressive males that are more likely to disperse when resources are low and non-aggressive philopatric males when resources are abundant. I then show experimentally that the association between resource availability and sex-specific birth order is robust across populations. Thus, this maternal effect enables close tracking of resource availability and may explain how variation in dispersal is generated in newly colonized populations. More generally, these results suggest that, as a key source of variation in colonizing phenotypes, maternal effects are of crucial importance for understanding the dynamics of range expansion.

Disentangling the effects of forage, social rank, and risk on movement autocorrelation of elephants using Fourier and wavelet analyses

The internal state of an individual-as it relates to thirst, hunger, fear, or reproductive drive-can be inferred by referencing points on its movement path to external environmental and sociological variables. Using time-series approaches to characterize autocorrelative properties of step-length movements collated every 3 h for seven free-ranging African elephants, we examined the influence of social rank, predation risk, and seasonal variation in resource abundance on periodic properties of movement. The frequency domain methods of Fourier and wavelet analyses provide compact summaries of temporal autocorrelation and show both strong diurnal and seasonal based periodicities in the step-length time series. This autocorrelation is weaker during the wet season, indicating random movements are more common when ecological conditions are good. Periodograms of socially dominant individuals are consistent across seasons, whereas subordinate individuals show distinct differences diverging from that of dominants during the dry season. We link temporally localized statistical properties of movement to landscape features and find that diurnal movement correlation is more common within protected wildlife areas, and multiday movement correlations found among lower ranked individuals are typically outside of protected areas where predation risks are greatest. A frequency-related spatial analysis of movement-step lengths reveal that rest cycles related to the spatial distribution of critical resources (i.e., forage and water) are responsible for creating the observed patterns. Our approach generates unique information regarding the spatial-temporal interplay between environmental and individual characteristics, providing an original approach for understanding the movement ecology of individual animals and the spatial organization of animal populations.

A COMPARISON OF SHRUB-DOMINATED AND FORESTED HABITAT USE BY SPRING MIGRATING LANDBIRDS IN NORTHEASTERN PENNSYLVANIA

Abstract Long-term datasets reveal declines in many populations of landbird migrants, with declines especially evident in shrub-nesting species. Moreover, transitional shrub-dominated habitats are becoming scarce, reducing breeding habitat for these species. Because migrants often occupy habitats en route similar to those used in the breeding season, the persistence of shrub-dominated habitats may be especially critical for these species during passage. Because little is known about migrant-habitat relationships, especially at inland, unforested stopover sites, we compared the importance of forested and upland shrub-dominated habitat to spring migrating landbirds by comparing: (1) temporal and habitat-related variation in resource abundance, and (2) migrant use of forested vs. shrub-dominated habitat during stopover. We collected data on bird-habitat relationships and invertebrate abundance from both habitats at two sites in or near Lackawanna State Park, Lackawanna County, Pennsylvania. We captured and c...

Biodiversity as both a cause and consequence of resource availability: a study of reciprocal causality in a predator–prey system

1. One of the oldest questions in ecology is how species diversity in any given trophic level is related to the availability of essential resources that limit biomass (e.g. water, nutrients, light or prey). Researchers have tried to understand this relationship by focusing either on how diversity is influenced by the availability of resources, or alternatively, how resource abundance is influenced by species diversity. These contrasting perspectives have led to a seeming paradox '... is species diversity the cause or the consequence of resources that limit community biomass?' 2. Here we present results of an experiment that show it is possible for species diversity and resource density to exhibit reciprocal causal relationships in the same ecological system. Using a guild of ladybeetle predators and their aphid prey, we manipulated the number of predator species in field enclosures to examine how predator diversity impacts prey population size. At the same time, we manipulated the abundance of aphid prey in discrete habitat patches within each enclosure to determine how smaller-scale spatial variation in resource abundance affects the number of co-occurring predator species. 3. We found that the number of ladybeetle species added to enclosures had a significant impact on aphid population dynamics because interference competition among the predators reduced per capita rates of predation and, in turn, the overall efficiency of the predator guild. At the same time, spatial variation in aphid abundance among smaller habitat patches generated variation in the observed richness of ladybeetles because more species occurred in patches where predators aggregated in response to high aphid density. 4. The results of our experiment demonstrate that it is possible for species diversity to simultaneously be a cause and a consequence of resource density in the same ecological system, and they shed light on how this might occur for groups of mobile consumers that exhibit rapid responses to spatial and temporal variation in their prey.

Food Shortage Disrupts Social Organization: The Case of Red Squirrels in Conifer Forests

A recent conceptual model of spatial organization in vertebrates, based upon changes in home range overlap with habitat quality, ‘the space-use model’, predicts large and strongly overlapping home ranges and absence of territorial behaviour in habitats with poor food availability. We investigated whether the model can be extended to predict intra-population variation in space-use in a habitat with strong temporal variation in resource abundance. We studied space use of Eurasian red squirrels (Sciurus vulgaris) in subalpine conifer forests over 4 years with strong fluctuations in seed production. Norway spruce dominated forests are resource limited habitats for squirrels, and tree seed availability is gradually depleted in the year following a poor seed-crop. Male and female squirrels responded to spruce seed-crop failure in 2000 by strongly increasing their home ranges and core-areas in the following year (mean MCP ± SE in summer and autumn, respectively: 2001, 122.9±14.1 ha and 84.3±9.4 ha, against 43.0±6.4 ha and 20.8±3.8 ha in 2002, and 22.7±1.5 ha and 21.4±2.0 ha in 2003). In 2001, half of the animals, those with the poorest quality pre-dispersal home ranges, emigrated to areas with more larch. Residents had multi-nuclear core-areas. Also, intra-sexual core-area overlap (males by males, females by females) was higher in 2001 and summer 2002, than in autumn 2002 and in 2003 (means ± SE in summer and autumn, respectively: males by males, 2001, 52±8 and 44±7%, 2002, 80±30 and 15±11%, 2003, 37±19 and 26±14%; females by females 2001, 52±10 and 112±32%, 2002, 55±27 and 0±0%, 2003, 12±8 and 0.1±0%). Red squirrels responded to food shortage by moving to patches with other food resources and abandoned the spacing pattern of reduced core-area overlap among males and nearly exclusive core-areas among females, found in less variable habitats. After richer seed-crops in 2001 and 2002, it took squirrels about a year to reduce the size of their home ranges and core-areas and return to a spacing pattern of stable home ranges and intra-sexual territoriality of adult females. These results are consistent with the space-use model and show that spacing behaviour in red squirrels is a plastic, conditional strategy with individuals adapting the size and/or location of their home ranges in relation to local distribution and abundance of food resources.

Ovarian dynamics in relation to host quality in the Walnut‐infesting Fly, Rhagoletis juglandis

Summary Reproductive behaviour is routinely studied with a view towards characterizing how an animal responds to variation in resource abundance and quality. This characterization is less commonly made with respect to reproductive physiology. In the Walnut‐infesting Fly, Rhagoletis juglandis, ovarian development is cued by the presence of the host fruit resource. In this study, I examined how ovarian development was affected by two host characteristics that relate to competition in the juvenile stages: fruit size and presence of conspecific larvae. Large fruit promoted egg maturation more than small fruit, and uninfested fruit promoted maturation more than larval‐infested fruit. Both effects were reproduced with artificial models of fruit. The functional significance of these effects and ramifications for individual‐level dynamics in oviposition behaviour are discussed.