| 1. |
- Arnqvist, Göran, 1961-, et al.
(författare)
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Mating rate and fitness in female bean weevils
- 2005
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Ingår i: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 16:1, s. 123-127
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Tidskriftsartikel (refereegranskat)abstract
- Females of most animal taxa mate with several males during their lifespan. Yet our understanding of the ultimate causes of polyandry is incomplete. For example, it is not clear if and in what sense female mating rates are optimal. Most female insects are thought to maximize their fitness by mating at an intermediate rate, but it has been suggested that two alternative fitness peaks may be observed if multiple costs and benefits interact in determining the relationship between mating rate and fitness. We studied the relationship between female fitness and mating rate in the bean weevil, Callosobruchus maculatus (Coleoptera: Bruchidae), a species in which several distinct direct effects of mating to females have been reported. Our results show that female fitness, measured as lifetime offspring production, is lowest at an intermediate mating rate. We suggest that this pattern is the result of multiple direct benefits to mating (e.g., sperm replenishment and hydration/nutrition effects) in combination with significant direct costs to mating (e.g., injury from male genitalia). Females mating at low rates may efficiently minimize the costs of mating, whereas females mating at high rates instead may maximize the benefits of mating. If common, the existence of bimodal relationships between female mating rate and fitness may help explain the large intra- and interspecific variation in the degree of polyandry often seen in insects.
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| 2. |
- Aronsson, Marianne, et al.
(författare)
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Importance of internal pattern contrast and contrast against the background in aposematic signals.
- 2009
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Ingår i: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 20:6, s. 1356-1362
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Tidskriftsartikel (refereegranskat)abstract
- Aposematic color patterns that signal prey unprofitability are suggested to work best when there is high contrast within the animal color pattern or between the animal and its background. Studies show that prey contrast against the background increases the signal efficiency. This has occasionally been extended to also explain the presence of internal patterns. We used domestic chicks, Gallus gallus domesticus, to investigate the relative importance for avoidance learning of within-prey pattern contrast and prey contrast against the background. In a series of trials, birds were first trained to avoid artificially made aposematic mealworms that were plain red or red with black stripes, and to discriminate them from palatable brown mealworms, on either a red or a brown background. Second, we investigated how the birds generalized between striped and nonstriped prey. The chicks showed faster avoidance learning when the basic color of the aposematic prey (red) contrasted with the background color (brown). However, there was no similar effect of internal pattern contrast. The generalization test showed a complete generalization between the nonstriped and the striped prey. We conclude that contrasting internal patterns do not necessarily affect predator avoidance learning the same way as shown for prey-to-background contrast in aposematic prey.
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| 3. |
- Berglund, Anders, et al.
(författare)
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An intimidating ornament in a female pipefish
- 2009
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Ingår i: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 20:1, s. 54-59
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Tidskriftsartikel (refereegranskat)abstract
- A sexually selected signal may serve a dual function being both attractive to mates and deterring rivals. Presently, there are few unambiguous demonstrations of an ornament functioning in both a mate choice and mate competition context and none regarding female ornaments. We have shown earlier that a temporary ornament, a striped pattern, in a sex-role reversed female pipefish, Syngnathus typhle, attracts males. Here we show that this ornament also intimidates rival females: in one experiment a male could interact with either 1 or 2 females. Latency until copulation was longer when 2, rather than 1, females were present. Moreover, when 2 females were present, competition lasted longer and time until mating took place increased when females displayed their ornaments more equally. In another experiment, a focal female could see 1 stimulus female and 1 stimulus male, the latter 2 being unaware of each other. The ornament of the stimulus female was manipulated, either strengthened by being painted black or left unaltered by being sham-painted. As a result, focal females experiencing black-painted stimulus females decreased courtship as well as competitive activities compared with focal females seeing sham-painted females. Moreover, focal females seeing black-painted females displayed less of their own ornament compared with controls. This decrease was due to a decrease in display toward males rather than to stimulus females. Thus, this female ornament indeed has a dual function, attracting mates and deterring rivals. In addition, the social costs invoked by this intimidating effect on rivals may help to maintain signal honesty.
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| 4. |
- Berglund, Anders, et al.
(författare)
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Sex-role reversal revisited : choosy females and ornamented, competitive males in a pipefish
- 2005
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Ingår i: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 16:3, s. 649-655
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Tidskriftsartikel (refereegranskat)abstract
- In the pipefish Syngnathus typhle sex roles are reversed, that is, females compete more intensely than males over mates. However, competition over mates among individuals of one sex does not necessarily prevent members of that same sex from being choosy, and choosiness in the other sex does not prevent competition within it. In an experiment we allowed a female pipefish to choose freely between two males, after which we released the males and let the three interact. Comparisons with earlier results show that both sexes courted partners and competed with consexuals. However, females courted more often than did males, and courtship was more frequent in treatments involving large individuals than in treatments with small individuals. Males competed among themselves for access to mates but for a shorter duration than females in the same situation. Males displayed an ornament towards females but not to males during mating competition. Females, however, used their ornament in both contexts. Females did not always mate with the male of their previously made choice, which we interpret as females being constrained by male-male competition, male motivation to mate, or both. Thus, in this sex-role reversed species, mate choice in the more competitive sex may be circumvented and even overruled by mate competition and mating willingness in the least competitive sex. Hence, sex roles should not be considered as sexes being either choosy or competitive but rather that males and females may exhibit different combinations of choice and competition.
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| 5. |
- Billing, Anna M., et al.
(författare)
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No terminal investment in pipefish males : Only young males exhibit risk-prone courtship behavior
- 2007
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Ingår i: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 18:3, s. 535-540
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Tidskriftsartikel (refereegranskat)abstract
- Animals are expected to trade-off current and future reproduction in order to maximize lifetime reproductive success. Old individuals may accept higher risks during courtship and mate choice as their residual reproductive value (RRV) diminishes (the terminal investment hypothesis). Alternatively, young individuals may be forced to take higher risks during courtship to compensate for their lower competitiveness and/or attractiveness (the compensation hypothesis). In this study, we used the sex-role reversed pipefish Syngnathus typhle to test how mate choice and courtship behavior of males with different RRV were affected by an increase in predation risk. Males of different ages were given the opportunity to court and choose between 2 partners. In half of the trials, a predator was present in a separate aquarium. We found no support for the terminal investment hypothesis: no difference in response to the increased predation risk by males of different ages was evident. In agreement with the compensation hypothesis, young males invested more in courtship behavior compared with older males. In addition, in the absence of a predator, we found that a high female activity was important for male mate choice decisions. During increased predation risk, this relationship was, however, reversed and males preferred less active, and thus less conspicuous, partners. This suggests that both female activity and size are important factors for male mating decisions in this species and that these decisions mainly are affected by predation risk and advantages in mate acquisition.
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| 6. |
- Bischoff, Linda L., et al.
(författare)
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Long-term effects of early parasite exposure on song duration and singing strategy in great tits
- 2009
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Ingår i: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 20:2, s. 265-270
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Tidskriftsartikel (refereegranskat)abstract
- Song is a sexually selected trait in many bird species and has been suggested to function as a signal of a male's health and parasite resistance. Here we present an experimental field study on the long-term effects of parasite exposure early in life on adult bird song. We exposed nestling great tits (Parus major) to ectoparasitic hen fleas (Ceratophyllus gallinae) and on their recruitment into the local breeding population assessed the response to a playback of a challenging male in their breeding territory. We show, to our knowledge for the first time in a wild bird population, that parasite exposure early in life affects bird song: song duration of males that were exposed to parasites early in life was reduced by 32% compared with males that grew up in a flea-free environment. Early parasite exposure also significantly reduced the degree of song overlap with the playback, which has been shown to correlate with social status. There was no effect of early parasite exposure on the number of different song types sung or on the latency until the males started the vocal response to the playback. These results suggest that mates or rivals can use song duration and song overlap as proxies for an individual's exposure to parasites early in life. It thereby highlights both the importance of parasites in maintaining honesty of sexually selected traits and the costs of parasitism in terms of reduced attractiveness and competitiveness.
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| 7. |
- Brodin, Tomas
(författare)
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Behavioral syndrome over the boundaries of life : carryovers from larvae to adult damselfly
- 2009
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Ingår i: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 20:1, s. 30-37
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Tidskriftsartikel (refereegranskat)abstract
- Activity is an important behavioral trait that mediates a trade-off between obtaining food for growth and avoiding predation. Active individuals usually experience a higher encounter rate with food items and suffer higher predation pressure than less active individuals. I investigated how activity of the damselfly Lestes congener is affected by larval state and predator presence and if larval behavioral type (BT) can be used to predict larval boldness, foraging success, and adult BT. Activity level of individual larvae was studied without predator at 2 different physiological states (hungry and fed) and in 2 predator treatments: familiar predator cues and unfamiliar predator cues. Larvae did not adjust their activity depending on state or when subjected to unfamiliar predator cues, but a general reduction in activity was seen in the familiar predator treatment. Hence, active individuals remained active compared with their conspecifics, independent of state or predator treatment. Active individuals were also bolder and more efficient foragers than their less active conspecifics. Furthermore, both adult activity and boldness were correlated with larval BT. The results illustrate that BT of a larvae is carried over many different situations keeping active larvae active even in maladaptive situations, demonstrating how a behavioral syndrome may constrain behavioral plasticity. Furthermore, results showed that behavioral syndromes can carry over from larvae through metamorphosis and dictate the BT of the adult.
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| 8. |
- Caesar, Sofia, et al.
(författare)
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Do polyandrous pygmy grasshopper females obtain fitness benefits for their offspring?
- 2009
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Ingår i: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 20:2, s. 354-361
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Tidskriftsartikel (refereegranskat)abstract
- Explanations for polyandry in insects invoke material and genetic benefits that enhance female fitness via the production of more viable or more variable offspring. Here we use the color polymorphic pygmy grasshopper, Tetrix subulata, to evaluate effects of male quality, mate color morph resemblance (a proxy for compatibility), and polyandry on offspring performance. We experimentally mated females with different numbers and color morph combinations of males and reared offspring under either sun-exposed or shaded conditions using a split-brood design. We find a significant male identity effect on egg hatchability, consistent with the hypothesis that males vary in paternal quality. Offspring viability posthatching varied in a complex manner with solar regime, mating treatment, and parental resemblance. The effects of parental color morph resemblance on offspring performance suggest a potential role of compatibility and offspring variability. Monandrous females produced more viable offspring than polyandrous females (under shaded conditions) and we suggest as a hypothesis that the expected positive influence of polyandry on offspring performance may have been outweighed by more intense competition and antagonistic interactions among half-siblings. That an effect of mating treatment was evident under shaded but not under sun-exposed conditions suggests that great care is called for when making inferences from studies that show negative results.
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| 9. |
- Edvardsson, Martin, et al.
(författare)
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Why do male Callosobruchus maculatus harm their mates?
- 2005
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Ingår i: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 16:4, s. 788-793
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Tidskriftsartikel (refereegranskat)abstract
- Males of the bruchid beetle Callosobruchus maculatus have spines on their intromittent organs that puncture the female reproductive tract during mating. Females kick their mates during copulation. If females are prevented from kicking the males, copulations last longer and the injuries females sustain are more severe. We tested whether or not these injuries represent real fitness costs that can be mitigated by kicking and also what males gain by inflicting them. Our results show that females do indeed suffer lowered lifetime fecundity if they are prevented from kicking. However, we could find no evidence that males gain benefits through harming their mates. It has been suggested that the way females respond to the harm may benefit the male causing it. Injured females may be less willing to remate to avoid sustaining further injuries, or they may respond by increasing their rate of oviposition if they perceive the injuries as a threat to their survival. In our study, however, females that were prevented from kicking did not respond by delaying remating or increasing their rate of oviposition. Furthermore, preventing females from kicking during their second copulation did not make their second mates more successful in sperm competition. This suggests that the spines have evolved for other reasons than harming the females, such as serving as an anchor during copulation, and that the harm they cause is a side effect of a male adaptation and is not itself adaptive for either sex.
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| 10. |
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