Kin-mediated plasticity in alternative reproductive tactics

Conditional strategies occur when the relative fitness pay-off from expressing a given phenotype is contingent upon environmental circumstances. This conditional strategy model underlies cases of alternative reproductive tactics, in which individuals of one sex employ different means to obtain reproduction. How kin structure affects the expression of alternative reproductive tactics remains unexplored. We address this using the mite Rhizoglyphus echinopus , in which large males develop into aggressive ‘fighters’ and small males develop into non-aggressive ‘scramblers.’ Because only fighters kill their rivals, they should incur a greater indirect fitness cost when competing with their relatives, and thus fighter expression could be reduced in the presence of relatives. We raised mites in full-sibling or mixed-sibship groups and found that fighters were more common at higher body weights in full-sibling groups, not less common as we predicted (small individuals were almost exclusively scramblers in both treatments). This result could be explained if relatedness and cue variability are interpreted signals of population density, since fighters are more common at low densities in this species. Alternatively, our results may indicate that males compete more intensely with relatives in this species. We provide the first evidence of kin-mediated plasticity in the expression of alternative reproductive tactics.

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Toward an understanding of the chemical ecology of alternative reproductive tactics in the bulb mite (Rhizoglyphus robini)

10.21203/rs.3.rs-677523/v1 ◽

2021 ◽

Author(s):

Adam N. Zeeman ◽

Isabel M. Smallegange ◽

Emily Burdfield Steel ◽

Astrid T. Groot ◽

Kathryn A. Stewart

Keyword(s):

Body Size ◽

Chemical Ecology ◽

Alternative Reproductive Tactics ◽

Relative Fitness ◽

Pheromone Production ◽

Reproductive Tactics ◽

Female Mimicry ◽

Significant Difference ◽

Nutritional Environment ◽

Bulb Mite

Abstract BackgroundUnder strong sexual selection, certain species evolve distinct intrasexual, alternative reproductive tactics (ARTs). In many cases, ARTs can be viewed as environmentally-cued threshold traits, such that ARTs coexist if their relative fitness alternates over the environmental cue gradient. Surprisingly, the chemical ecology of ARTs has been underexplored in this context. To our knowledge, no prior study has directly quantified pheromone production for ARTs in a male-polymorphic species. Here, we used the bulb mite—in which males are either armed fighters that kill conspecifics, or unarmed scramblers—as a model system to gain insight into the role of pheromones in the evolutionary maintenance of ARTs. Given that scramblers forgo investment into weaponry, we tested whether scramblers produce higher pheromone quantities than fighters, which would improve the fitness of the scrambler phenotype, e.g. through female mimicry to avoid aggression from competitors. To this end, we sampled mites from a rich and a poor nutritional environment and quantified their production of the female sex pheromone α-acaridial through gas chromatography analysis. ResultsWe found a positive relationship between pheromone production and body size, but males exhibited a steeper slope in pheromone production with increasing size than females. Females exhibited a higher average pheromone production than males. We found no significant difference in slope of pheromone production over body size between fighters and scramblers. However, scramblers reached larger body sizes and higher pheromone production than fighters, providing some evidence for a potential female mimic strategy adopted by large scramblers. Pheromone production was significantly higher in mites from the rich nutritional environment than the poor environment. ConclusionFurther elucidation of pheromone functionality in bulb mites, and additional inter- and intrasexual comparisons of pheromone profiles are needed to determine if the observed intersexual and intrasexual differences in pheromone production are adaptive, if they are a by-product of allometric scaling, or diet-mediated pheromone production under weak selection. We argue chemical ecology offers a novel perspective for research on ARTs and other complex life-history traits.

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Impact of male alternative reproductive tactics on female costs of sexual conflict under variation in operational sex ratio and population density

Ecology and Evolution ◽

10.1002/ece3.3631 ◽

2017 ◽

Vol 8 (1) ◽

pp. 584-591 ◽

Cited By ~ 1

Author(s):

Erica Jeffery ◽

Alex Córdoba‐Aguilar ◽

Bernard Roitberg

Keyword(s):

Population Density ◽

Sex Ratio ◽

Sexual Conflict ◽

Alternative Reproductive Tactics ◽

Operational Sex Ratio ◽

Reproductive Tactics

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Toward an understanding of the chemical ecology of alternative reproductive tactics in the bulb mite (Rhizoglyphus robini)

BMC Ecology and Evolution ◽

10.1186/s12862-021-01956-w ◽

2022 ◽

Vol 22 (1) ◽

Author(s):

Adam N. Zeeman ◽

Isabel M. Smallegange ◽

Emily Burdfield Steel ◽

Astrid T. Groot ◽

Kathryn A. Stewart

Keyword(s):

Body Size ◽

Chemical Ecology ◽

Alternative Reproductive Tactics ◽

Relative Fitness ◽

Pheromone Production ◽

Reproductive Tactics ◽

Female Mimicry ◽

Significant Difference ◽

Nutritional Environment ◽

Bulb Mite

Abstract Background Under strong sexual selection, certain species evolve distinct intrasexual, alternative reproductive tactics (ARTs). In many cases, ARTs can be viewed as environmentally-cued threshold traits, such that ARTs coexist if their relative fitness alternates over the environmental cue gradient. Surprisingly, the chemical ecology of ARTs has been underexplored in this context. To our knowledge, no prior study has directly quantified pheromone production for ARTs in a male-polymorphic species. Here, we used the bulb mite—in which males are either armed fighters that kill conspecifics, or unarmed scramblers (which have occasionally been observed to induce mating behavior in other males)—as a model system to gain insight into the role of pheromones in the evolutionary maintenance of ARTs. Given that scramblers forgo investment into weaponry, we tested whether scramblers produce higher quantities of the putative female sex-pheromone α-acaridial than fighters, which would improve the fitness of the scrambler phenotype through female mimicry by allowing avoidance of aggression from competitors. To this end, we sampled mites from a rich and a poor nutritional environment and quantified their production of α-acaridial through gas chromatography analysis. Results We found a positive relationship between pheromone production and body size, but males exhibited a steeper slope in pheromone production with increasing size than females. Females exhibited a higher average pheromone production than males. We found no significant difference in slope of pheromone production over body size between fighters and scramblers. However, scramblers reached larger body sizes and higher pheromone production than fighters, providing some evidence for a potential female mimic strategy adopted by large scramblers. Pheromone production was significantly higher in mites from the rich nutritional environment than the poor environment. Conclusion Further elucidation of pheromone functionality in bulb mites, and additional inter- and intrasexual comparisons of pheromone profiles are needed to determine if the observed intersexual and intrasexual differences in pheromone production are adaptive, if they are a by-product of allometric scaling, or diet-mediated pheromone production under weak selection. We argue chemical ecology offers a novel perspective for research on ARTs and other complex life-history traits.

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Toward an understanding of the chemical ecology of alternative reproductive tactics in the bulb mite (Rhizoglyphus robini)

10.1101/2021.06.30.450527 ◽

2021 ◽

Author(s):

Adam N Zeeman ◽

Isabel M. Smallegange ◽

Emily Burdfield-Steel ◽

Astrid T. Groot ◽

Kathryn A. Stewart

Keyword(s):

Body Size ◽

Chemical Ecology ◽

Alternative Reproductive Tactics ◽

Relative Fitness ◽

Pheromone Production ◽

Reproductive Tactics ◽

Female Mimicry ◽

Significant Difference ◽

Nutritional Environment ◽

Bulb Mite

Background Under strong sexual selection, certain species evolve distinct intrasexual, alternative reproductive tactics (ARTs). In many cases, ARTs can be viewed as environmentally cued threshold traits, such that ARTs coexist if their relative fitness alternates over the environmental cue gradient. Surprisingly, the chemical ecology of ARTs has been underexplored in this context. To our knowledge, no prior study has directly quantified pheromone production for ARTs in a male polymorphic species. Here, we used the bulb mite — in which males are either armed fighters that kill conspecifics, or unarmed scramblers — as a model system to gain insight into the role of pheromones in the evolutionary maintenance of ARTs. Given that scramblers forgo investment into weaponry, we tested whether scramblers produce higher pheromone quantities than fighters, which would improve the fitness of the scrambler phenotype, e.g. through female mimicry to avoid aggression from competitors. To this end, we sampled mites from a rich and a poor nutritional environment and quantified their production of the female sex pheromone α acaridial through gas chromatography analysis. Results We found a positive relationship between pheromone production and body size, but males exhibited a steeper slope in pheromone production with increasing size than females. Females exhibited a higher average pheromone production than males. We found no significant difference in slope of pheromone production over body size between fighters and scramblers. However, scramblers reached larger body sizes and higher pheromone production than fighters, providing some evidence for a potential female mimic strategy adopted by large scramblers. Pheromone production was significantly higher in mites from the rich nutritional environment than the poor environment. Conclusion Further elucidation of pheromone functionality in bulb mites, and additional inter and intrasexual comparisons of pheromone profiles are needed to determine if the observed intersexual and intrasexual differences in pheromone production are adaptive, if they are a byproduct of allometric scaling, or diet mediated pheromone production under weak selection. We argue chemical ecology offers a novel perspective for research on ARTs and other complex life-history traits.

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