The size of weapons and testes can be central to male reproductive success. Yet, the expression of these traits is often extremely variable. Studies are needed that take a more complete organism perspective, investigating the sources of variation in both traits simultaneously and using developmental conditions that mimic those in nature. In this study, we investigated the components of variation in weapon and testis sizes using the leaf‐footed cactus bug,
Adverse conditions may be the norm rather than the exception in natural populations. Many populations experience poor nutrition on a seasonal basis. Further, brief interludes of inbreeding can be common as population density fluctuates and because of habitat fragmentation. Here, we investigated the effects of poor nutrition and inbreeding on traits that can be very important to reproductive success and fitness in males: testes mass, sperm concentration, and sperm viability. Our study species was
- NSF-PAR ID:
- 10017928
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Ecology and Evolution
- Volume:
- 6
- Issue:
- 14
- ISSN:
- 2045-7758
- Format(s):
- Medium: X Size: p. 4792-4799
- Size(s):
- ["p. 4792-4799"]
- Sponsoring Org:
- National Science Foundation
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Abstract Narnia femorata (Hemiptera: Coreidae) on three natural developmental diets. We show that the developmental diet has profound effects on both weapon and testis expression and scaling. Intriguingly, males in the medium‐quality diet express large weapons but have relatively tiny testes, suggesting complex allocation decisions. We also find that heritability, evolvability, and additive genetic variation are highest in the high‐quality diet for testis and body mass. This result suggests that these traits may have an enhanced ability to respond to selection during a small window of time each year when this diet is available. Taken together, these results illustrate that normal, seasonal fluctuations in the nutritional environment may play a large role in the expression of sexually selected traits and the ability of these traits to respond to selection. -
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Abstract Infection can cause hosts to drastically alter their investment in key life‐history traits of reproduction and defence. Infected individuals are expected to increase investment in defence (e.g., by increasing immune function) and, due to trade‐offs, investment in other traits (e.g., current reproduction) should decrease. However, the terminal investment hypothesis postulates that decreased lifespan due to infection and the associated reduction in the expectation for future offspring will favour increased investment towards current reproduction. Variation in intrinsic condition will likely influence shifts in reproductive investment post‐infection, but this is often not considered in such assessments. For example, the extent of inbreeding can significantly impact an individual's lifetime fitness and may influence its reproductive behaviour following a threat of infection. Here, we investigated the effects of inbreeding status on an individual's reproductive investment upon infection, including the propensity to terminally invest. Male crickets (
Gryllodes sigillatus ) from four genetically distinct inbred lines and one outbred line were subjected to a treatment from an increasing spectrum of simulated infection cue intensities, using heat‐killed bacteria. We then measured reproductive effort (calling effort), survival and immune function (antibacterial activity, circulating haemocytes and haemocyte microaggregations). Inbred and outbred males diverged in how they responded to a low‐dose infection cue: relative to unmanipulated males, outbred males decreased calling effort, whereas inbred males increased calling effort. Moreover, we found that inbred males exhibited higher antibacterial activity and numbers of circulating haemocytes compared with outbred males. These results suggest that an individual's inbreeding status may have consequences for context‐dependent shifts in reproductive strategies, such as those triggered by infection. -
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Abstract Floral odours play an important role in attracting insect pollinators. Because pollinators visit flowers to obtain pollen and nectar rewards, they should prefer floral odour profiles associated with the highest‐rewarding flowers (honest signals). In previous work, bumblebees exhibited a preference for flowers from outbred over inbred
Mimulus guttatus plants. Pollen is the only floral reward inM. guttatus , and pollen viability (a reliable indicator of protein content) is reduced in inbred plants. Yet, differences in pollen viability did not explain the observed preferences.In this study, we examined the floral volatile profiles of inbred and outbred
M. guttatus to identify inbreeding effects and associations between volatile compounds and the number of viable pollen grains per flower, designated “PRQ ” (pollen reward quality). We also conducted pairwise choice tests withBombus impatiens to evaluate the ability of bees to discriminate between odours of rewarding and non‐rewarding flowers and to determine whether bumblebee preferences are explained by differences in the floral odours of inbred and outbred plants.Inbred plants exhibited reduced emission of β‐trans‐bergamotene, the second‐most abundant compound in the volatile blend of outbred plants. Furthermore, pollen and fertile anthers emitted nonadecane. Six other compounds in the floral blend were positively correlated with
PRQ . There was no overlap between compounds affected by inbreeding and compounds associated withPRQ .Even when given prior experience foraging on
M. guttatus , bumblebees did not distinguish between the floral odours of rewarding and non‐rewarding outbred plants. However, they preferred floral odours from non‐rewarding outbred plants over rewarding inbred plants. Bumblebees without prior experience of flowers preferred volatile blends with higher versus lower amounts of β‐trans‐bergamotene.Taken together, these results suggest that the volatile emissions of
M. guttatus provide reliable indicators of pollen rewards (potential honest signals), but that the preference of bumblebees for outbred plants is not driven by these cues but rather by a sensory bias for β‐trans‐bergamotene. This may represent a subtle form of deceit‐pollination that allows plants to attract pollinators while minimizing investment in costly rewards.A
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Premise Plant maternal effects on offspring phenotypes are well documented. However, little is known about how herbivory on maternal plants affects offspring fitness. Furthermore, while inbreeding is known to reduce plant reproductive output, previous studies have not explored whether and how such effects may extend across generations. Here, we addressed the transgenerational consequences of herbivory and maternal plant inbreeding on the reproduction of S
olanum carolinense offspring.Methods Manduca sexta caterpillars were used to inflict weekly damage on inbred and outbredS. carolinense maternal plants. Cross‐pollinations were performed by hand to produce seed from herbivore‐damaged outbred plants, herbivore‐damaged inbred plants, undamaged outbred plants, and undamaged inbred plants. The resulting seeds were grown in the greenhouse to assess emergence rate and flower production in the absence of herbivores. We also grew offspring in the field to examine reproductive output under natural conditions.Results We found transgenerational effects of herbivory and maternal plant inbreeding on seedling emergence and reproductive output. Offspring of herbivore‐damaged plants had greater emergence, flowered earlier, and produced more flowers and seeds than offspring of undamaged plants. Offspring of outbred maternal plants also had greater seedling emergence and reproductive output than offspring of inbred maternal plants, even though all offspring were outbred. Moreover, the effects of maternal plant inbreeding were more severe when plant offspring were grown in field conditions.
Conclusions This study demonstrates that both herbivory and inbreeding have fitness consequences that extend across generations even in outbred progeny.
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Abstract In
Drosophila , long sperm are favoured in sperm competition based on the length of the female's primary sperm storage organ, the seminal receptacle (SR ). This sperm–SR interaction, together with a genetic correlation between the traits, suggests that the coevolution of exaggerated sperm andSR lengths may be driven by Fisherian runaway selection. Here, we explore the costs and benefits of long sperm andSR genotypes, both in the sex that carries them and in the sex that does not. We measured male and female fitness in inbred lines ofDrosophila melanogaster derived from four populations previously selected for long sperm, short sperm, longSR s or shortSR s. We specifically asked: What are the costs and benefits of long sperm in males and longSR s in females? Furthermore, do genotypes that generate long sperm in males or longSR s in females impose a fitness cost on the opposite sex? Answers to these questions will address whether long sperm are an honest indicator of male fitness, male post‐copulatory success is associated with male precopulatory success, female choice benefits females or is costly, and intragenomic conflict could influence evolution of these traits. We found that both sexes have increased longevity in long sperm and longSR genotypes. Males, but not females, from longSR lines had higher fecundity. Our results suggest that sperm–SR coevolution is facilitated by both increased viability and indirect benefits of long sperm andSR s in both sexes.
