Forest restoration treatments indirectly diversify pollination networks via floral- and temperature-mediated effects.

In North American conifer forests, a variety of federally initiated thinning programs are implemented to restore pre-European settlement forest structures, but these changes may impact ecosystem function via impacts on sensitive biotic communities. Across the wildland-urban interface of the Front Range region of Colorado, agencies associated with the Collaborative Forest Landscape Restoration Program (CFLRP) have implemented thinning treatments across thousands of hectares of ponderosa pine forest; here we leverage these treatments as an experimental framework to examine thinning effects on a pollinator community. We measured variation in forest structure and sampled bee community assemblages using multiple methods (trapping and netting) to compare bee biodiversity and patterns of floral visitation by bees (bee-flower networks) between mechanically thinned stands that were 3-10 years after treatment and nonthinned stands. Three key findings emerged: (1) Native bee abundance, richness, and diversity were 120%, 53%, and 37% greater, respectively, in thinned stands. In addition, nestedness, richness, and abundance of bee-flower interactions were all substantially higher in thinned stands, and there was increased functional redundancy in bee assemblages after thinning. (2) Structural equation modeling indicated that variation in temperature and floral abundance were mediated by canopy openness and correlated with bee richness and abundance, thereby indirectly driving variation in bee-flower interactions. (3) Four floral species (Penstemon virens, Cerastium arvense, Erysimum capitatum, and Geranium caespitosum) were identified as key connectors in bee-flower interaction networks, though these were not necessarily the most abundant flowering plants. Our analyses indicate that native bee α-diversity and bee-flower interactions positively responded to thinning treatments, and these effects were indirectly driven by canopy removal. We conclude that CFLRP treatments have conservation value for native bee communities. Further monitoring is warranted to evaluate the longevity of these effects.

The effect of natural disturbances on forest biodiversity: an ecological synthesis.

Disturbances alter biodiversity via their specific characteristics, including severity and extent in the landscape, which act at different temporal and spatial scales. Biodiversity response to disturbance also depends on the community characteristics and habitat requirements of species. Untangling the mechanistic interplay of these factors has guided disturbance ecology for decades, generating mixed scientific evidence of biodiversity responses to disturbance. Understanding the impact of natural disturbances on biodiversity is increasingly important due to human-induced changes in natural disturbance regimes. In many areas, major natural forest disturbances, such as wildfires, windstorms, and insect outbreaks, are becoming more frequent, intense, severe, and widespread due to climate change and land-use change. Conversely, the suppression of natural disturbances threatens disturbance-dependent biota. Using a meta-analytic approach, we analysed a global data set (with most sampling concentrated in temperate and boreal secondary forests) of species assemblages of 26 taxonomic groups, including plants, animals, and fungi collected from forests affected by wildfires, windstorms, and insect outbreaks. The overall effect of natural disturbances on α-diversity did not differ significantly from zero, but some taxonomic groups responded positively to disturbance, while others tended to respond negatively. Disturbance was beneficial for taxonomic groups preferring conditions associated with open canopies (e.g. hymenopterans and hoverflies), whereas ground-dwelling groups and/or groups typically associated with shady conditions (e.g. epigeic lichens and mycorrhizal fungi) were more likely to be negatively impacted by disturbance. Across all taxonomic groups, the highest α-diversity in disturbed forest patches occurred under moderate disturbance severity, i.e. with approximately 55% of trees killed by disturbance. We further extended our meta-analysis by applying a unified diversity concept based on Hill numbers to estimate α-diversity changes in different taxonomic groups across a gradient of disturbance severity measured at the stand scale and incorporating other disturbance features. We found that disturbance severity negatively affected diversity for Hill number q = 0 but not for q = 1 and q = 2, indicating that diversity-disturbance relationships are shaped by species relative abundances. Our synthesis of α-diversity was extended by a synthesis of disturbance-induced change in species assemblages, and revealed that disturbance changes the ß-diversity of multiple taxonomic groups, including some groups that were not affected at the α-diversity level (birds and woody plants). Finally, we used mixed rarefaction/extrapolation to estimate biodiversity change as a function of the proportion of forests that were disturbed, i.e. the disturbance extent measured at the landscape scale. The comparison of intact and naturally disturbed forests revealed that both types of forests provide habitat for unique species assemblages, whereas species diversity in the mixture of disturbed and undisturbed forests peaked at intermediate values of disturbance extent in the simulated landscape. Hence, the relationship between α-diversity and disturbance severity in disturbed forest stands was strikingly similar to the relationship between species richness and disturbance extent in a landscape consisting of both disturbed and undisturbed forest habitats. This result suggests that both moderate disturbance severity and moderate disturbance extent support the highest levels of biodiversity in contemporary forest landscapes.

Bumblebee (Hymenoptera: Apidae) Visitation Frequency Drives Seed Yields and Interacts with Site-Level Species Richness to Drive Pollination Services in Sunflower.

Understanding whether pollinator behaviors and species richness drive crop yields is a key area of investigation in pollination ecology. Using sunflower as a study species we describe variation in mean floral visitation times among bee taxa and test how interactions between bee richness and the proportion of bumblebees in localized communities impact seed yield. Seven bee genera commonly visited sunflower including Agapostemon, Bombus, Halictus, Lasioglossum, Megachile, Melissodes, and Svastra. Mean visitation times to sunflower varied across genera and Bombus and Halictus spp. spent the most time foraging on inflorescences, but the number of visits by Bombus spp. was the only parameter associated with increased yields. Experimental pollination deficit reduced seed development and yields, and these effects were stronger in stands of wild-type sunflower in the field compared to a confection variety grown in the greenhouse. Relationships between bee richness and pollination services differed for potted and wild sunflower: when bees had short-term access to potted sunflower, bee richness and relative Bombus abundances were not associated with pollination quotients. When bees had long-term access to wild sunflower, relative Bombus abundances predicted pollination services but were modified by site-level bee richness: as richness increased, the effects of Bombus abundance decreased. Our studies demonstrate that bee species richness is not always a clear predictor of pollination services; instead, our results underscore the importance of specific taxa when species richness is low (here, bumblebees), and show that the effects of bee functional groups important for pollination may be modified by changes in site-level species richness.

Interspecific variation in spruce constitutive and induced defenses in response to a bark beetle-fungal symbiont provides insight into traits associated with resistance.

Differences in defensive traits of tree species may predict why some conifers are susceptible to bark beetle-fungal complexes and others are not. A symbiotic fungus (Leptographium abietinum (Peck) M.J. Wingf.) associated with the tree-killing bark beetle (Dendroctonus rufipennis Kirby) is phytopathogenic to host trees and may hasten tree decline during colonization by beetles, but defense responses of mature trees to the fungus have not been experimentally examined. To test the hypothesis that interspecific variation in spruce resistance is explained by defense traits we compared constitutive (bark thickness and constitutive resin ducts) and induced defenses (resin flow, monoterpene composition, concentration, phloem lesion formation and traumatic resin ducts) between two sympatric spruces: Engelmann spruce (Picea engelmannii Parry ex Engelm.-a susceptible host) and blue spruce (Picea pungens Engelm.-a resistant host) in response to fungal inoculation. Four central findings emerged: (i) blue spruce has thicker outer bark and thinner phloem than Engelmann spruce, which may restrict fungal access to phloem and result in less beetle-available resource overall; (ii) both spruce species induce monoterpenes in response to inoculation but blue spruce has higher constitutive monoterpene levels, induces monoterpenes more rapidly, and induces higher concentrations over a period of time consistent with spruce beetle attack duration; (iii) Engelmann and blue spruce differed in the monoterpenes they upregulated in response to fungal inoculation: blue spruce upregulated α-pinene, terpinolene and γ-terpinene, but Engelmann spruce upregulated 3-carene and linalool; and (iv) blue spruce has a higher frequency of constitutive resin ducts and produces more traumatic resin ducts in annual growth increments than Engelmann spruce, though Engelmann spruce produces more resin following aseptic wounding or fungal inoculation. These findings suggest that higher constitutive resin duct densities and monoterpene concentrations, as well as the ability to rapidly induce specific monoterpenes in response to L. abietinum inoculation, are phenotypic traits associated with hosts resistant to spruce beetle colonization.

Livestock grazing is associated with seasonal reduction in pollinator biodiversity and functional dispersion but cheatgrass invasion is not: Variation in bee assemblages in a multi-use shortgrass prairie.

Livestock grazing and non-native plant species affect rangeland habitats globally. These factors may have important effects on ecosystem services including pollination, yet, interactions between pollinators, grazing, and invasive plants are poorly understood. To address this, we tested the hypothesis that cattle grazing and site colonization by cheatgrass (Bromus tectorum) impact bee foraging and nesting habitats, and the biodiversity of wild bee communities, in a shortgrass prairie system. Bee nesting habitats (litter and wood cover) were marginally improved in non-grazed sites with low cheatgrass cover, though foraging habitat (floral cover and richness, bare soil) did not differ among cattle-grazed sites or non-grazed sites with low or high cheatgrass cover. However, floral cover was a good predictor of bee abundance and functional dispersion. Mean bee abundance, richness, diversity and functional diversity were significantly lower in cattle-grazed habitats than in non-grazed habitats. Differences in bee diversity among habitats were pronounced early in the growing season (May) but by late-season (August) these differences eroded as Melissodes spp. and Bombus spp. became more abundant at study sites. Fourth-corner analysis revealed that sites with high floral cover tended to support large, social, polylectic bees; sites with high grass cover tended to support oligolectic solitary bees. Both cattle-grazed sites and sites with high cheatgrass cover were associated with lower abundances of above-ground nesting bees but higher abundance of below-ground nesters than non-grazed sites with low cheatgrass cover. We conclude that high cheatgrass cover is not associated with reduced bee biodiversity or abundance, but cattle grazing was negatively associated with bee abundances and altered species composition. Although floral cover is an important predictor of bee assemblages, this was not impacted by cattle grazing and our study suggests that cattle likely impact bee communities through effects other than those mediated by forbs, including soil disturbance or nest destruction. Efforts aimed at pollinator conservation in prairie habitats should focus on managing cattle impacts early in the growing season to benefit sensitive bee species.

Bark beetle outbreak enhances biodiversity and foraging habitat of native bees in alpine landscapes of the southern Rocky Mountains.

Landscape-scale bark beetle outbreaks alter forest structure with direct and indirect effects on plants and animals in forest ecosystems. Using alpine spruce forest and a native bee community as a study system, we tested how tree mortality from bark beetles impacts bee foraging habitats and populations. Bees were collected across the growing season (early-, middle-, and late-season) for two years using passive trapping methods, and collections were used to analyze patterns in species abundances and diversity. Three important findings emerged: (1) forest stands that were post-outbreak had 62% higher floral density and 68% more floral species during peak bloom, respectively, than non-affected stands; (2) bee captures were highest early-season (June) and were not strongly affected by bark beetle outbreak; however, mean number of bee species and Shannon-Weiner diversity were significantly higher in post-outbreak stands and this effect was pronounced early in the growing season. Corresponding analysis of ß-diversity indicated higher accumulation of bee biodiversity in post-outbreak stands and a turnover in the ratio of Bombus: Osmia; (3) bee captures were linked to variation in foraging habitat, but number of bee species and diversity were more strongly predicted by forest structure. Our results provide evidence of increased alpine bee biodiversity in post-outbreak stands and increased availability of floral resources. We conclude that large-scale disturbance from bark beetle outbreaks may drive shifts in pollinator community composition through cascading effects on floral resources, mediated via mortality of overstory trees.

Effects of Site Thermal Variation and Physiography on Flight Synchrony and Phenology of the North American Spruce Beetle (Coleoptera: Curculionidae, Scolytinae) and Associated Species in Colorado.

Spruce beetle, Dendroctonus rufipennis Kirby, is associated with forest mortality in Colorado and across western North America, yet it is not well understood how thermal variability affects basic population processes such as flight phenology. However, phenology-temperature relationships are important for understanding patterns of ecosystem disturbance, especially under projected climate warming. Here, we use a multiyear trapping study to test the hypothesis that spruce beetle flight synchrony, timing, and fitness traits (body size) are affected by variation in regional temperature and physiography. Large quantities of co-colonizing scolytines (Polygraphus convexifrons) (Coleoptera: Curculionidae, Scolytinae) and predatory beetles (Thanasimus undulatus) (Coleoptera: Cleridae) that may affect D. rufipennis populations also responded to spruce beetle synthetic pheromone lures. Relationships between flight patterns and environmental conditions were also analyzed for these species. The winter of 2018 was warmer and drier than winter 2017 and was associated with earlier flight for both scolytine species across most sites. The most important environmental factor driving D. rufipennis flight phenology was accumulated growing degree-days, with delayed flight cessation under warmer conditions and larger beetles following a warm winter. Flight was consistently more synchronous under colder growing season conditions for all species, but synchrony was not associated with winter temperatures. Warmer-than-average years promoted earlier flight of D. rufipennis and associated species, and less synchronous, prolonged flight across the region. Consequently, climate warming may be associated with earlier and potentially extended biotic pressure for spruce trees in the Rocky Mountain region, and flight phenology of multiple scolytines is plastic in response to thermal conditions.

Engelmann Spruce Chemotypes in Colorado and their Effects on Symbiotic Fungi Associated with the North American Spruce Beetle.

Conifer secondary metabolites play a key role in mechanisms of resistance to biotic disturbance, especially by bark beetles and beetle-associated microorganisms. Here, we describe variation in constitutive monoterpenes isolated from Engelmann spruce, Picea engelmannii, phloem across fourteen high-elevation populations in the Rocky Mountains of Colorado, and test interactions between phloem monoterpenes and an endophloedic symbiotic fungus, Leptographium abietinum, associated with the North American spruce beetle, Dendroctonus rufipennis. We consistently identified ten monoterpenes in Engelmann spruce phloem, and the trees in our samples could be classified into two geographically interspersed chemical phenotypes, or 'chemotypes': one in which α- and ß-pinene were the most abundant monoterpenes, and one in which 3-carene was the most abundant monoterpene. Media amended with low concentrations of α-pinene, ß-pinene, 3-carene, myrcene, and terpinolene stimulated growth of L. abietinum. Increasing monoterpene concentrations uniformly retarded fungal growth. Linalool completely suppressed fungal growth at all concentrations, while terpinolene completely suppressed growth at low and intermediate concentrations, indicating relatively high toxicity of these compounds. Tests with monoterpene blends representing the 'average' monoterpene composition of each chemotype indicated that representative chemotypes are equivalent in fungistatic activity, with chemotype blends being inhibitory even at low concentrations. Total constitutive monoterpene abundances in Engelmann spruce phloem ranged from 42 to 1796 µg/g. Induction of Engelmann spruce phloem monoterpenes in response to L. abietinum or other biotic agents has yet to be quantified, but is important for further understanding Engelmann spruce resistance to the D. rufipennis-L. abietinum complex.

Laboratory and Field Evaluation of the Entomopathogenic Fungus Beauveria bassiana (Deuteromycotina: Hyphomycetes) for Population Management of Spruce Beetle, Dendroctonus rufipennis (Coleoptera: Scolytinae), in Felled Trees and Factors Limiting Pathogen Success.

An isolate of the entomopathogenic fungus Beauveria bassiana (Bals.) Vuill. (Deuteromycotina: Hyphomycetes) was tested for its ability to reduce survival and reproduction of spruce beetle, Dendroctonus rufipennis (Kirby) (Coleoptera: Scolytinae), under laboratory and field conditions. Conidial suspension applied directly to adults or to filter papers that adults contacted had a median survival time of 3-4 d in laboratory assays and beetles died more rapidly when exposed to conidial suspension than when treated with surfactant solution only. In the field, conidial suspension was applied to the surface of felled and pheromone-baited Engelmann spruce (Picea engelmannii) trees using a backpack sprayer. Mortality of colonizing parent beetles (F0), reproduction (abundance of F1 offspring in logs), and emergence of F1 beetles from logs was compared between treated and nontreated logs. Application of spore suspension increased mortality of F0 adults by 36% on average. Total F1 reproduction was reduced by 17% and emergence from logs was reduced by 13% in treated logs, but considerable variability in reproduction and emergence was observed. Viable spores were re-isolated from treated logs up to 90 d after application, indicating that spores are capable of long-term persistence on the tree bole microhabitat. Subsequent in vitro tests revealed that temperatures below 15°C and exposure to spruce monoterpenes likely limit performance of B. bassiana under field conditions, but exposure to low-intensity light or interactions with spruce beetle symbiotic fungi were not strongly inhibitory. It is concluded that matching environmental tolerances of biocontrol fungi to field conditions can likely improve their usefulness for control of spruce beetle in windthrown trees.

The ecology of yeasts in the bark beetle holobiont: a century of research revisited.

Yeasts are extremely common associates of scolytine bark beetles, yet the basic ecology of yeasts in the bark beetle holobiont remains poorly understood. Yeasts are present in all beetle life stages and consistently isolated from adult, larval, and pupal integuments and mycangial structures, but yeasts are also found in oviposition galleries, pupal chambers, larval and adult digestive tracts, as well as phloem and xylem tissues. Yeasts in the Saccharomycetaceae family are the most prevalent associates, and most individual beetles are associated with only one or several yeast species. Kuraishia capsulata and Ogataea pini are the most commonly encountered yeast species in surveys of Dendroctonus and Ips beetles; most beetles that have been surveyed are vectors for one or both yeasts. Yeasts have significant but often overlooked functional roles in bark beetle ecology. Infochemicals resulting from volatile production by yeast have wide-ranging bioactivity for arthropods: Yeast emissions attract beetles at low concentrations but repel beetles at high concentrations, and yeast emissions can also serve as cues to predators and parasites of bark beetles. In some cases, yeasts can modify tree chemistry over time or metabolize toxic terpenoids, though potential consequences for beetle performance or the growth of nutritional fungi remain to be demonstrated. Also, the presence of yeast species can restrict or promote the establishment and growth of filamentous fungi, including mutualists, entomopathogens, and opportunistic saprophytes. The role of yeasts as nutritional symbionts has received mixed support, though a nutritional hypothesis has not been extensively tested. Continued research on the functional ecology of bark beetle-yeast associations is needed to better understand the emergent properties of these complex symbiont assemblages.

Microbial volatile emissions as insect semiochemicals.

We provide a synthesis of the literature describing biochemical interactions between microorganisms and insects by way of microbial volatile organic compound (MVOC) production. We evaluated the functionality and ecological context of MVOC signals, and explored important metabolic pathways involved in MVOC production. The cosmopolitan distribution of microorganisms creates a context for frequent, and frequently overlooked, insect responses to microbial emissions. There are numerous instances of MVOCs being closely associated with insect feeding behaviors, but some MVOCs are also powerful repellants. Emissions from microorganisms in situ may signal aspects of habitat suitability or potential exposure to entomopathogens. In some ecosystems, bacterial or fungal volatiles can also incite insect aggregations, or MVOCs can resemble sexual pheromones that elicit mating and oviposition behaviors from responding insects. A single microorganism or MVOC can have different effects on insect behaviors, especially across species, ontogenies, and habitats. There appears to be a multipartite basis for insect responses to MVOCs, and complex tritrophic interactions can result from the production of MVOCs. Many biochemical pathways for behaviorally active volatile production by microbial species are conserved across large taxonomic groupings of microorganisms. In addition, there is substantial functional redundancy in MVOCs: fungal tissues commonly produce polyketides and short-chain alcohols, whereas bacterial tissues tend to be more commonly associated with amines and pyrazines. We hypothesize that insect olfactory responses to emissions from microorganisms inhabiting their sensory environment are much more common than currently recognized, and that these signals represent evolutionarily reliable infochemicals. Insect chemoreception of microbial volatiles may contribute to the formation of neutral, beneficial, or even harmful symbioses and provide considerable insight into the evolution of insect behavioral responses to volatile compounds.

A survey of insect assemblages responding to volatiles from a ubiquitous fungus in an agricultural landscape.

We report here a first survey of insect orientation to fungal cultures and fungal volatiles from a community ecology perspective. We tested whether volatiles from a ubiquitous yeast-like fungus (Aureobasidium pullulans) are broadly attractive to insects in an agricultural landscape. We evaluated insect attraction to fungal cultures and synthetic compounds identified in fungal headspace (2-methyl-1-butanol, 3-methyl-1-butanol, 2-phenylethanol) in a spearmint (Mentha spicata L.) plantation. Three findings emerged: (1) 1,315 insects representing seven orders and 39 species oriented to traps, but 65 % of trapped insects were Dipterans, of which 80 % were hoverflies (Diptera: Syrphidae); (2) traps baited with A. pullulans caught 481 % more insects than unbaited control traps on average, and contained more diverse (Shannon's H index) and species rich assemblages than control traps, traps baited with Penicillium expansum, or uninoculated media; and (3) insects oriented in greatest abundance to a 1:1:1 blend of A. pullulans volatiles, but mean diversity scores were highest for traps baited with only 2-phenylethanol or 2-methyl-1-butanol. Our results show that individual components of fungal headspace are not equivalent in terms of the abundance and diversity of insects that orient to them. The low abundance of insects captured with P. expansum suggests that insect assemblages do not haphazardly orient to fungal volatiles. We conclude that volatiles from a common fungal species (A. pullulans) are attractive to a variety of insect taxa in an agricultural system, and that insect orientation to fungal volatiles may be a common ecological phenomenon.

Experimental infection of plants with an herbivore-associated bacterial endosymbiont influences herbivore host selection behavior.

Although bacterial endosymbioses are common among phloeophagous herbivores, little is known regarding the effects of symbionts on herbivore host selection and population dynamics. We tested the hypothesis that plant selection and reproductive performance by a phloem-feeding herbivore (potato psyllid, Bactericera cockerelli) is mediated by infection of plants with a bacterial endosymbiont. We controlled for the effects of herbivory and endosymbiont infection by exposing potato plants (Solanum tuberosum) to psyllids infected with "Candidatus Liberibacter solanacearum" or to uninfected psyllids. We used these treatments as a basis to experimentally test plant volatile emissions, herbivore settling and oviposition preferences, and herbivore population growth. Three important findings emerged: (1) plant volatile profiles differed with respect to both herbivory and herbivory plus endosymbiont infection when compared to undamaged control plants; (2) herbivores initially settled on plants exposed to endosymbiont-infected psyllids but later defected and oviposited primarily on plants exposed only to uninfected psyllids; and (3) plant infection status had little effect on herbivore reproduction, though plant flowering was associated with a 39% reduction in herbivore density on average. Our experiments support the hypothesis that plant infection with endosymbionts alters plant volatile profiles, and infected plants initially recruited herbivores but later repelled them. Also, our findings suggest that the endosymbiont may not place negative selection pressure on its host herbivore in this system, but plant flowering phenology appears correlated with psyllid population performance.

Volatile emissions from an epiphytic fungus are semiochemicals for eusocial wasps.

Microbes are ubiquitous on plant surfaces. However, interactions between epiphytic microbes and arthropods are rarely considered as a factor that affects arthropod behaviors. Here, volatile emissions from an epiphytic fungus were investigated as semiochemical attractants for two eusocial wasps. The fungus Aureobasidium pullulans was isolated from apples, and the volatile compounds emitted by fungal colonies were quantified. The attractiveness of fungal colonies and fungal volatiles to social wasps (Vespula spp.) were experimentally tested in the field. Three important findings emerged: (1) traps baited with A. pullulans caught 2750 % more wasps on average than unbaited control traps; (2) the major headspace volatiles emitted by A. pullulans were 2-methyl-1-butanol, 3-methyl-1-butanol, and 2-phenylethyl alcohol; and (3) a synthetic blend of fungal volatiles attracted 4,933 % more wasps on average than unbaited controls. Wasps were most attracted to 2-methyl-1-butanol. The primary wasp species attracted to fungal volatiles were the western yellowjacket (Vespula pensylvanica) and the German yellowjacket (V. germanica), and both species externally vectored A. pullulans. This is the first study to link microbial volatile emissions with eusocial wasp behaviors, and these experiments indicate that volatile compounds emitted by an epiphytic fungus can be responsible for wasp attraction. This work implicates epiphytic microbes as important components in the community ecology of some eusocial hymenopterans, and fungal emissions may signal suitable nutrient sources to foraging wasps. Our experiments are suggestive of a potential symbiosis, but additional studies are needed to determine if eusocial wasp-fungal associations are widespread, and whether these associations are incidental, facultative, or obligate.

Body size phenotypes are heritable and mediate fecundity but not fitness in the lepidopteran frugivore Cydia pomonella.

The inheritance and functional roles of quantitative traits are central concerns of evolutionary ecology. We report two sets of experiments that investigated the heritability and reproductive consequences of body size phenotypes in a globally distributed lepidopteran frugivore, Cydia pomonella (L.). In our first set of experiments, we tested the hypotheses that (1) body size is heritable and (2) parental body size mediates egg production and offspring survival. Midparent-offspring regression analyses revealed that body mass is highly heritable for females and moderately heritable for males. The contribution of fathers to estimates of additive genetic variance was slightly greater than for mothers. Egg production increased with mean parental size, but offspring survival rates were equivalent. Based on this result, we tested two additional hypotheses in a second set of experiments: (3) male size moderates female egg production and egg fertility and (4) egg production, egg fertility, and offspring survival rate are influenced by female mating opportunities. Females paired with large males produced more eggs and a higher proportion of fertile eggs than females paired with small males. Females with multiple mating opportunities produced more fertile eggs than females paired with a single male. However, egg production and offspring survival rates were unaffected by the number of mating opportunities. Our experiments demonstrate that body mass is heritable in C. pomonella and that size phenotypes may mediate fecundity but not fitness. We conclude that male size can influence egg production and fertility, but female mate choice also plays a role in determining egg fertility.