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

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.

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

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.

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

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.

Alternative Reproductive Tactics

2020 ◽  
pp. 429-446
Author(s):  
Shawn Garner ◽  
Bryan Neff
Keyword(s):  
Body Size ◽  
Small Body ◽  
Large Body ◽  
Morphological Differentiation ◽  
Alternative Reproductive Tactics ◽  
Reproductive Tactics ◽  
Aggressive Interactions ◽  
Single Sex ◽  
Female Mimicry ◽  
Mating Opportunities

Alternative reproductive tactics (ARTs) describe variation among individuals of a single sex in the tactics used to obtain mating opportunities. In crustaceans, ARTs have been observed in multiple taxa and take a variety of forms. ARTs are most commonly observed in males and are generally associated with intense competition among males to monopolize access to breeding females. ARTs frequently involve a guard tactic that competes with other males to monopolize access to females, while a second usurper tactic foregos competition with other males and instead obtains mating opportunities through sneaking behavior. Guard and usurper tactics may be expressed conditionally based on a male’s ability to guard a female (e.g. his body size, the abundance of competitors), or may be expressed as discrete phenotypes that can also include morphological differentiation. For example, in Jassa amphipods the guard tactic is associated with large body size and an enlarged “thumb” on the claw that is used in aggressive interactions with other males, while the usurper tactic is associated with small body size and a reduced thumb. The usurper tactic can take two forms in a marine isopod: small males (gamma) use sneaking behavior to avoid competition with large males (alpha), whereas intermediate-sized males (beta) use female mimicry to avoid competition. Overall, ARTs are well-represented in crustaceans, with many opportunities for continued study to better characterize these unique adaptations.

scholarly journals The role of genetic diversity in the evolution and maintenance of environmentally-cued, male alternative reproductive tactics

2019 ◽  
Author(s):  
KA Stewart ◽  
R Draaijer ◽  
MR Kolasa ◽  
IM Smallegange
Keyword(s):  
Genetic Variation ◽  
Genetic Differentiation ◽  
Genetic Correlations ◽  
Alternative Reproductive Tactics ◽  
Population Variation ◽  
Reproductive Tactics ◽  
Genetic Profiling ◽  
Significant Difference ◽  
The Face ◽  
Bulb Mite

AbstractBackgroundAlternative reproductive tactics (ARTs) are taxonomically pervasive strategies adopted by individuals to maximize reproductive success within populations. Even for conditionally-dependent traits, consensus postulates most ARTs involve both genetic and environmental interactions (GEIs), but to date, quantifying genetic variation underlying the threshold disposing an individual to switch phenotypes in response to an environmental cue has been a difficult undertaking. Our study aims to investigate the origins and maintenance of ARTs within environmentally disparate populations of the microscopic bulb mite, Rhizoglyphus robini, that express ‘fighter’ and ‘scrambler’ male morphs mediated by a complex combination of environmental and genetic factors.ResultsUsing never-before-published individual genetic profiling, we found all individuals across populations are highly inbred with the exception of scrambler males in stressed environments. In fact within the poor environment, scrambler males and females showed no significant difference in genetic differentiation (Fst) compared to all other comparisons, and although fighters were highly divergent from the rest of the population in both poor or rich environments (e.g., Fst, STRUCTURE), fighters demonstrated approximately three times less genetic divergence from the population in poor environments. AMOVA analyses further corroborated significant genetic differentiation across subpopulations, between morphs and sexes, and among subpopulations within each environment.ConclusionOur study provides new insights into the origin of ARTs in the bulb mite, highlighting the importance of GEIs: genetic correlations, epistatic interactions, and sex-specific inbreeding depression across environmental stressors. Asymmetric reproductive output, coupled with the purging of highly inbred individuals during environmental oscillations, also facilitates genetic variation within populations, despite evidence for strong directional selection. This cryptic genetic variation also conceivably facilitates stable population persistence even in the face of spatially or temporally unstable environmental challenges. Ultimately, understanding the genetic context that maintains thresholds, even for conditionally-dependent ARTs, will enhance our understanding of within population variation and our ability to predict responses to selection.

scholarly journals Alternative reproductive tactics and sex‐biased gene expression: the study of the bulb mite transcriptome

2014 ◽  
Vol 4 (5) ◽  
pp. 623-632 ◽  
Author(s):  
Michal T. Stuglik ◽  
Wiesław Babik ◽  
Zofia Prokop ◽  
Jacek Radwan
Keyword(s):  
Gene Expression ◽  
Alternative Reproductive Tactics ◽  
Reproductive Tactics ◽  
Bulb Mite

scholarly journals Genetic correlations across genetically determined and developmentally plastic alternative reproductive tactics

2019 ◽  
Author(s):  
Jessica K. Abbott ◽  
Oscar Rios-Cardenas ◽  
Molly Morris
Keyword(s):  
Body Size ◽  
Genetic Correlation ◽  
Genetic Correlations ◽  
Phenotypic Expression ◽  
Alternative Reproductive Tactics ◽  
Phenotypic Trait ◽  
Sexual Antagonism ◽  
Reproductive Tactics ◽  
Genetic Conflict ◽  
Genetically Determined

AbstractAlternative reproductive tactics occur when individuals of the same sex have a suite of morphological and/or behavioural traits that allow them to pursue different reproductive strategies. A common pattern is e.g. the existence of “courter” and “sneaker” tactics within males. We have previously argued that alternative reproductive tactics should be subject to genetic conflict over the phenotypic expression of traits, similar to sexual antagonism. In this process, which we called intra-locus tactical conflict, genetically determined tactics experience conflicting selection on a shared phenotypic trait, such as body size, but a positive genetic correlation between tactics in body size prevents either tactic from reaching its optimum. Recently, other authors have attempted to extend this idea to developmentally plastic alternative reproductive tactics, with mixed results. However, it is not clear whether we should expect intra-locus tactical conflict in developmentally plastic tactics or not. We have therefore run a series of simulation models investigating under what conditions we should expect to see positive estimates of the inter-tactical genetic correlation, since a positive genetic correlation is a prerequisite for the existence of intra-locus tactical conflict. We found that for autosomal, X-linked, and Y-linked genetically-determined tactics, estimated inter-tactical genetic correlations were generally high. However, for developmentally plastic tactics, the genetic correlation depends on the properties of the switching threshold between tactics. If it is fixed, then estimated genetic correlations are positive, but if there is genetic variation in the switch-point, then any sign and magnitude of estimated genetic correlation is possible, even for highly heritable traits where the true underlying correlation is perfect. This means that caution should be used when investigating genetic constraints in plastic phenotypes.

scholarly journals The evolution of genetic and conditional alternative reproductive tactics

2016 ◽  
Vol 283 (1825) ◽  
pp. 20152945 ◽  
Author(s):  
Leif Engqvist ◽  
Michael Taborsky
Keyword(s):  
Body Size ◽  
Size Variation ◽  
Alternative Reproductive Tactics ◽  
Disruptive Selection ◽  
Relevant Parameter ◽  
Reproductive Tactics ◽  
Adaptive Diversification ◽  
Size Dependent ◽  
Mortality Causes ◽  
Genetically Determined

Frequency-dependent selection may drive adaptive diversification within species. It is yet unclear why the occurrence of alternative reproductive tactics (ARTs) is highly divergent between major animal taxa. Here we aim to clarify the environmental and social conditions favouring the evolution of intra-population variance of male reproductive phenotypes. Our results suggest that genetically determined ARTs that are fixed for life evolve when there is strong selection on body size due to size-dependent competitiveness, in combination with environmental factors reducing size benefits. The latter may result from growth costs or, more generally, from age-dependent but size-independent mortality causes. This generates disruptive selection on growth trajectories underlying tactic choice. In many parameter settings, the model also predicts ARTs to evolve that are flexible and responsive to current conditions. Interestingly, the conditions favouring the evolution of flexible tactics diverge considerably from those favouring genetic variability. Nevertheless, in a restricted but relevant parameter space, our model predicts the simultaneous emergence and maintenance of a mixture of multiple tactics, both genetically and conditionally determined. Important conditions for the emergence of ARTs include size variation of competitors, which is inherently greater in species with indeterminate growth than in taxa reproducing only after reaching their terminal body size. This is probably the reason why ARTs are more common in fishes than in other major taxa.

scholarly journals Sperm and alternative reproductive tactics: a review of existing theory and empirical data

2020 ◽  
Vol 375 (1813) ◽  
pp. 20200075
Author(s):  
Matthew C. Kustra ◽  
Suzanne H. Alonzo
Keyword(s):  
Sperm Competition ◽  
Empirical Data ◽  
Alternative Reproductive Tactics ◽  
Theme Issue ◽  
Reproductive Tactics ◽  
Comprehensive Review ◽  
Trade Offs ◽  
Significant Difference ◽  
General Expectation ◽  
Sperm Traits

Males that exhibit alternative reproductive tactics (ARTs) often differ in the risk of sperm competition and the energetic trade-offs they experience. The resulting patterns of selection could lead to between-tactic differences in ejaculate traits. Despite extensive research on male ARTs, there is no comprehensive review of whether and what differences in sperm traits exist between male ARTs. We review existing theory on ejaculate evolution relevant to ARTs and then conduct a comprehensive vote-counting review of the empirical data comparing sperm traits between males adopting ARTs. Despite the general expectation that sneaker males should produce sperm that are more competitive (e.g. higher quality or performance), we find that existing theory does not predict explicitly how males adopting ARTs should differ in sperm traits. The majority of studies find no significant difference in sperm performance traits between dominant and sneaker males. However, when there is a difference, sneaker males tend to have higher sperm performance trait values than dominant males. We propose ways that future theoretical and empirical research can improve our understanding of the evolution of ejaculate traits in ARTs. We then highlight how studying ejaculate traits in species with ARTs will improve our broader knowledge of ejaculate evolution. This article is part of the theme issue ‘Fifty years of sperm competition’.

scholarly journals Environmental Influence on Life-History Traits in Male Squid Uroteuthis Edulis With Alternative Reproductive Tactics

2021 ◽  
Author(s):  
Yumeng Pang ◽  
Chih-Shin Chen ◽  
Tomohiko Kawamura ◽  
Yoko Iwata
Keyword(s):  
Life History ◽  
Body Size ◽  
Growth Rates ◽  
Life History Traits ◽  
Environmental Influence ◽  
Life Stage ◽  
Energy Allocation ◽  
Alternative Reproductive Tactics ◽  
Reproductive Tactics ◽  
Somatic Energy

Abstract Squid are characterized by flexible life-history traits (LHTs) that change in response to changing oceanic parameters. Male alternative reproductive tactics (ARTs), characterized by large-sized ‘consorts’ versus small-sized ‘sneakers’, are commonly observed in loliginid species. This study reports on LHTs flexibility in male squids displaying ARTs. LHTs of consorts and sneakers in Uroteuthis edulis, including body size, age, growth rate and gonado-somatic energy allocation, were compared among seasonal and geographical groups from Japan and Taiwan. The ratio of consorts to sneakers was highest in the group spawning in the ‘Japan-warm’ season (June-November), followed by that of the ‘Japan-cold’ season (December-May), and lowest in Taiwan (spring and autumn). LHTs were compared among cohorts separated by hatching season and catch location (Jwarm, Jcold and Taiwan cohorts). Mean body size of consorts showed no difference among cohorts, although Taiwan consorts were relatively younger than Japan consorts. Mean size and age of sneakers decreased with increased water temperature at hatching. Growth rates of consorts and sneakers were slightly different among cohorts, in accordance with differences of statolith increment widths during their early life stage (50-150 d). Growth rates of both consorts and sneakers were highest in the Taiwan cohort, followed by the Jwarm cohort, with the Jcold cohort lowest. Sneakers invested more both in mantle and gonadal weights than consorts in all cohorts. Gonado-somatic energy allocation patterns of consorts and sneakers were consistent at different temperatures. LHTs of U. edulis consorts and sneakers were strongly influenced by temperature, with higher flexibility in sneakers than consorts.

scholarly journals Steroid hormones in bluegill, a species with male alternative reproductive tactics including female mimicry

2007 ◽  
Vol 3 (6) ◽  
pp. 628-632 ◽  
Author(s):  
Rosemary Knapp ◽  
Bryan D Neff
Keyword(s):  
Mating Behaviour ◽  
Lepomis Macrochirus ◽  
Negative Relationship ◽  
Alternative Reproductive Tactics ◽  
Reproductive Tactics ◽  
Proximate Mechanisms ◽  
Female Mimicry ◽  
First Time ◽  
The Relationship ◽  
Satellite Males

The proximate mechanisms underlying the evolution and maintenance of within-sex variation in mating behaviour are still poorly understood. Species characterized by alternative reproductive tactics provide ideal opportunities to investigate such mechanisms. Bluegill ( Lepomis macrochirus ) are noteworthy in this regard because they exhibit two distinct cuckolder (parasitic) morphs (called sneaker and satellite) in addition to the parental males that court females. Here we confirm previous findings that spawning cuckolder and parental males have significantly different levels of testosterone and 11-ketotestosterone. We also report, for the first time, that oestradiol and cortisol levels are higher in cuckolders than in parental males. The two cuckolder morphs did not differ in average levels of any of the four hormones. However, among satellite males which mimic females in appearance and behaviour, there was a strong negative relationship between oestradiol levels and body length, a surrogate for age. This finding suggests that for satellite males, oestradiol dependency of mating behaviour decreases with increasing mating experience. Although such decreased hormone dependence of mating behaviour has been reported in other taxa, our data represent the first suggestion of the relationship in fishes.

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