Male Alternative Reproductive Tactics Research Articles

Squid male alternative reproductive tactics are determined by birth date.

Alternative reproductive tactics (ARTs) are discontinuous phenotypes associated with reproduction, observed in males of many species. Typically, large males adopt a tactic of competing with rivals for mating, while small males adopt a tactic of stealing fertilization opportunities from the large males. The 'birth date hypothesis', proposing that the date of birth influences the determination of each male's reproductive tactic, has been tested only in teleost fish to date. Here, the birth date hypothesis was tested in ARTs of Japanese spear squid Heterololigo bleekeri (consort/sneaker) by analysing statolith growth increments. The birth date significantly differed between consorts (early-hatched) and sneakers (late-hatched). However, no differences were detected in growth history up to 100 days from hatching. Most immature males caught during the reproductive season were larger than sneakers, and their hatch date was similar to that of consorts, suggesting that these immature males had already been following a life-history pathway as a consort. These results indicate that ARTs of H. bleekeri are determined based on their hatch date in early life. This study firstly suggests that the birth date hypothesis applies to aquatic invertebrates, suggesting that the mechanism by which birth date determines the individual phenotype is a phenomenon more common than previously believed.

Modelling the impacts of male alternative reproductive tactics on population dynamics.

Observations of male alternative reproductive tactics (ARTs) in a variety of species have stimulated the development of mathematical models that can account for the evolution and stable coexistence of multiple male phenotypes. However, little attention has been given to the population dynamic consequences of ARTs. We present a population model that takes account of the existence of two male ARTs (guarders and sneakers), assuming that tactic frequencies are environmentally determined and tactic reproductive success depends on the densities of both types. The presence of sneakers typically increases overall population density. However, if sneakers comprise a sufficiently large proportion of the population-or, equivalently, if guarders are sufficiently rare-then it is possible for the total population to crash to extinction (in this extreme regime, there is also an Allee effect, i.e. a threshold density below which the population will go extinct). We apply the model to the example of the invasive round goby (Neogobius melanostomus). We argue that ARTs can dramatically influence population dynamics and suggest that considering such phenotypic plasticity in population models is potentially important, especially for species of conservation or commercial importance.

Female reproductive fluid and male seminal fluid: a non-gametic conflict for post-mating control.

Growing evidence shows that non-gametic components released by both males and females can significantly drive sperm competition outcomes. Seminal fluid (SF) was shown to influence paternity success by affecting rival males' sperm performance, and, in some species with male alternative reproductive tactics, to selectively decrease the fertilization success of males of the opposite tactic. Female reproductive fluid (FRF) has been proven to differentially influence ejaculates of different males and bias fertilization towards specific partners. Whether, and with what outcome, these two processes can intersect to influence sperm competition is still unknown. Here we explore this scenario in the grass goby (Zosterisessor ophiocephalus), a fish with territorial-sneaker reproductive tactics, where sneaker males can exploit the territorials' SF while penalizing territorial sperm performance with their own fluid. To test whether FRF can rebalance the ejaculate competition in favour of territorial males, we used in vitro fertilization with a SF mixture (territorial + sneaker), using increasing concentrations of FRF, to simulate the natural conditions that ejaculates encounter towards the eggs. Our findings revealed a differential effect of FRF on the different tactics' fertilization success, favouring territorial ejaculates, possibly through an attenuation of the detrimental effects of sneaker SF, and enabling females to regain control over the fertilization process.

Social Environment Influences the Temporal Dynamics of Sneak-Spawning in a Fish with Alternative Reproductive Tactics.

AbstractSeveral predictions of sperm competition theory are not well supported empirically. One potential reason is that most current theory and empirical research ignore how the social environment influence the temporal dynamics of mating. We propose that understanding these dynamics is key to understanding sexual selection and improving the predictive power of theory. To demonstrate the importance of these dynamics, we quantify how males' social role, interactions among males, and current social environment influence the timing of mating in Symphodus ocellatus, a species with three alternative male reproductive tactics. Nesting males spawn synchronously with females; sneakers and satellites sneak-spawn with some time delay. Satellites also cooperate with nesting males. We found that satellites have shorter sneak-spawning delays than sneakers, a benefit of their cooperation with nesting males. Sneak-spawning delays decreased with increasing nest activity for sneakers but not for satellites, suggesting that sneakers may benefit from increased sperm competition intensity. Current sperm competition models ignore this potential benefit, which may be why the prediction that males should decrease investment when sperm competition involves more than two males is not well supported. Our study provides insight into mechanisms that drive variation in the timing of spawning, which could explain mismatches between theoretical and empirical results.

Male alternative reproductive tactics and sperm competition: a meta-analysis.

ABSTRACTIn many animal species, males may exhibit one of several discrete, alternative ways of obtaining fertilisations, known as alternative reproductive tactics (ARTs). Males exhibiting ARTs typically differ in the extent to which they invest in traits that improve their mating success, or the extent to which they face sperm competition. This has led to the widespread prediction that males exhibiting ARTs associated with a high sperm competition risk, or lower investment into traits that improve their competitiveness before mating, should invest more heavily into traits that improve their competitiveness after mating, such as large ejaculates and high‐quality sperm. However, despite many studies investigating this question since the 1990s, evidence for differences in sperm and ejaculate investment between male ARTs is mixed, and there has been no quantitative summary of this field. Following a systematic review of the literature, we performed a meta‐analysis examining how testes size, sperm number and sperm traits differ between males exhibiting ARTs that face either a high or low sperm competition risk, or high or low investment in traits that increase mating success. We obtained data from 92 studies and 67 species from across the animal kingdom. Our analyses showed that male fish exhibiting ARTs facing a high sperm competition risk had significantly larger testes (after controlling for body size) than those exhibiting tactics facing a low sperm competition risk. However, this effect appears to be due to the inappropriate use of the gonadosomatic index as a body‐size corrected measure of testes investment, which overestimates the difference in testes investment between male tactics in most cases. We found no significant difference in sperm number between males exhibiting different ARTs, regardless of whether sperm were measured from the male sperm stores or following ejaculation. We also found no significant difference in sperm traits between males exhibiting different ARTs, with the exception of sperm adenosine triphosphate (ATP) content in fish. Finally, the difference in post‐mating investment between male ARTs was not influenced by the extent to which tactics were flexible, or by the frequency of sneakers in the population. Overall, our results suggest that, despite clear theoretical predictions, there is little evidence that male ARTs differ substantially in investment into sperm and ejaculates across species. The incongruence between theoretical and empirical results could be explained if (i) theoretical models fail to account for differences in overall resource levels between males exhibiting different ARTs or fundamental trade‐offs between investment into different ejaculate and sperm traits, and (ii) studies often use sperm or ejaculate traits that do not reflect overall post‐mating investment accurately or affect fertilisation success.

Environmental influence on life-history traits in male squid Uroteuthis edulis with alternative reproductive tactics

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 days). 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.

The Evolution of Social Behaviour

The Evolution of Social Behaviour

Reproductive biology of pioneer round gobies (Neogobius melanostomus Pallas, 1814) at the edge of their invasion front in three small rivers (Lower Danube Basin, Bulgaria)

Reproductive traits are among the most important biological characteristics that facilitate or impede the establishment of non-native fish into new environments. In several tributaries of the Lower River Danube (Bulgaria), the round goby (Neogobius melanostomus Pallas, 1814) is a recent invader. Specimens from the edge of the invasion front were collected monthly (March 2017 to May 2018) from each river. The pioneer individuals displayed relatively small body sizes. First maturation of females occurs at 49 mm total length. Based on the dynamics of oocyte size and GSI, it was established that spawning begins in early spring, at a relatively low water temperature (6-7 °C). The breeding season extended from March to June. Average absolute fecundity was 162 ± 62 oocytes, while average relative fecundity was 94 oocytes/g ± 24. Female fecundity is linearly dependent on the length and weight. Both of the known male alternative reproductive tactics were observed. Body condition factor was lowest during April for both sexes. The relationship between reproductive traits and invasive potential in N. melanostomus is discussed.

Trade‐off mediated by pyrrolizidine alkaloids predicts alternative reproductive tactics in ithomiine butterflies

1. Trade‐offs between male mating success and survival are the basis of alternative male reproductive tactics.2. Adult male Greta morgane butterflies acquire protective pyrrolizidine alkaloids (PAs) from plants and use PA‐derived pheromones to attract females. Adult females acquire PAs from male spermatophores, thereby obtaining chemical defence against predation while avoiding costs of PA toxicity and sequestration.3. We found that males that fed longer on PA‐containing plants were more successful at mating, but males fed a diet containing PAs had a shorter lifespan than males fed a diet without PAs. Together, these results demonstrate a trade‐off between survival and reproduction in relation to male feeding behaviour.4. As predicted by the alternative reproductive tactics hypothesis, we found that some males fed preferentially on PA‐containing plants while others specialised on PA‐free plants.

Alternative reproductive tactics in male freshwater fish influence the accuracy of species recognition.

Sexual conflict can result in coercive mating. Because males bear low costs of heterospecific mating, coercive males may engage in misdirected mating attempts toward heterospecific females. In contrast, sexual selection through consensual mate choice can cause mate recognition cues among species to diverge, leading to more accurate species recognition. Some species show both coercive mating and mate choice‐associated courtship behaviors as male alternative reproductive tactics. We hypothesized that if the selection pressures on each tactic differ, then the accuracy of species recognition would also change depending on the mating tactic adopted. We tested this hypothesis in the guppy (Poecilia reticulata) and mosquitofish (Gambusia affinis) by a series of choice experiments. Poecilia reticulata and G. affinis males both showed imperfect species recognition and directed all components of mating behavior toward heterospecific females. They tended to direct courtship displays more frequently toward conspecific than heterospecific females. With male P. reticulata, however, accurate species recognition disappeared when they attempted coercive copulation: they directed coercions more frequently toward heterospecific females. We also found that heterospecific sexual interaction had little effect on the fecundity of gravid females, which suggests that prepregnancy interactions likely underpin the exclusion of G. affinis by P. reticulata in our region.

A study of tactical and sexual dimorphism in cognition with insights for sexual conflict

The sexes may have different optima in cognitive traits due to differences in life history strategies and the expense of investing in metabolically costly brain tissue. However, given genetic correlations, each sex could be constrained from reaching its cognitive optimum due to intralocus sexual conflict. We compared learning performance of two male alternative reproductive tactics and females from known genotypes (both sire and dam) in the livebearing fish Xiphophorus multilineatus. We predicted that females' learning performance would align with the learning performance of their sire's genotype due to genetic correlation of cognitive traits. Using a classical conditioning assessment (associating a flashing light with a food reward), we detected mating tactic dimorphism in learning performance, with the behaviourally plastic sneaker males outperforming the behaviourally fixed courter males. Unexpectedly, females sired by the faster-learning sneaker males performed significantly worse than sneaker males. We also detected an influence of brain size on female learning performance. Previous studies have found that females invest more in offspring sired by courter males, and we therefore hypothesize that maternal effects could potentially mitigate the influence of sexual conflict on a cognitive trait.

Kin-Mediated Male Choice and Alternative Reproductive Tactics in Spider Mites.

Simple SummaryEvolutionary-grounded theories predict that any mating-related behavior should be influenced by the degree of genetic relatedness between the involved interactants. Close genetic relatedness may have beneficial and detrimental effects on evolutionary fitness. To optimize these trade-offs, mates should be able to discriminate kin and non-kin and adjust their behaviors accordingly. Here, we assessed kin-dependent mate choice and adjustment of alternative reproductive tactics (ARTs) in male spider mites. Our experiments suggest that male spider mites can assess kinship of rivals and prospective mates. Mate choice and expression of ARTs (fighting versus sneaking) were driven by direct and indirect fitness benefits arising from the degree of kinship of available mates and rival males competing for access to females. Depending on the social context (choice vs. no-choice, w/wo competition) and achievable fitness benefits, males seemed to use novelty as absolute decision rule and/or comparative evaluation in mate choice. Close kinship among rivals mitigated the males’ fighting propensity and favored adoption of the sneaking tactic. Overall, our study highlights kin-mediated plasticity in male choice and expression of ARTs and emphasizes the importance to consider different contexts and inclusive fitness benefit/cost trade-offs when interpreting mating preferences.Optimal outbreeding and kin selection theories state that the degree of kinship is a fundamental determinant in any mating system. However, the role of kinship in male choice and alternative reproductive tactics (ARTs) is poorly known. We assessed the influence of kinship on male choice and expression of ARTs in two populations of two-spotted spider mites Tetranychus urticae. Male spider mites guard premature females, which is an indicator of mate choice, and may conditionally adopt fighting or sneaking tactics to secure access to females. Males competing with kin or non-kin were offered one kin or non-kin female (experiment 1) and single males were presented a choice of kin and non-kin females (experiment 2). Under kin competition, males of both populations were more prone to guard non-kin than kin females at a 3:1 fighter:sneaker ratio. Under non-kin competition, all males were fighters. Under no-choice, males used novelty as indicator of genetic dissimilarity, serving as absolute decision rule for outbreeding. Under choice, comparative evaluation allowed males to preferentially guard females with higher reproductive potential. Overall, our study suggests that male spider mites can assess kinship of rivals and prospective mates. Kin discrimination allows adaptive, context-specific non-random mating preference and adjustment of ARTs.

Male Alternative Reproductive Tactics and Associated Evolution of Anatomical Characteristics in Loliginid Squid.

Loliginid squids provide a unique model system to explore male alternative reproductive tactics (ARTs) and their linkage to size, behavioral decision making, and possibly age. Large individuals fight one another and the winners form temporary consortships with females, while smaller individuals do not engage in male-male agonistic bouts but use various sneaker tactics to obtain matings, each with varying mating and fertilization success. There is substantial behavioral flexibility in most species, as smaller males can facultatively switch to the alternative consort behaviors as the behavioral context changes. These forms of ARTs can involve different: mating posture; site of spermatophore deposition; fertilization success; and sperm traits. Most of the traits of male dimorphism (both anatomical and behavioral) are consistent with traditional sexual selection theory, while others have unique features that may have evolved in response to the fertilization environment faced by each temporary or permanent male morph.

Life histories of anadromous salmon males reveal a trade-off between primary and secondary sexual traits

Abstract The life-history trade-off between investment in somatic growth and gonadal tissue is caused by individual energy limitations and results in individuals that adopt specific tactics to achieve reproduction. Allocation in primary and secondary sexual traits in Atlantic salmon males was studied by assessing life history traits (smolt size, sea age, growth rate) based on back-calculation of scales, ejaculate energy content (sperm ATP content, mass and density) and the size of secondary sexual traits. We found that males investing less in secondary sexual traits produce ejaculates with a higher energy content. Differences were found in the investment into primary and secondary sexual traits between fish that spent one year in the sea before returning to their spawning grounds (grilse) and multi-sea-winter adults, suggesting that different energy allocation patterns in reproductive effort reflect alternative developmental pathways. These findings are consistent with the pattern where multi-sea-winter male ejaculate investment relies principally on the resource acquisition in the ocean, whereas grilse ejaculate investment relies chiefly on the resource allocation of available surplus energy, thus representing alternative male reproductive tactics.

Parental effects of male alternative reproductive tactics (ARTs) on ARTs of haploid sons

Abstract Alternative reproductive tactics (ARTs) represent distinct behavioural phenotypes to maximize reproductive success within the same sex, primarily males, and may be genetically and/or conditionally determined. Across animals, intragenerational determinants of conditional ARTs are relatively well understood but transgenerational (non‐genetic) effects of parental ARTs on filial ARTs are largely unknown. Here, we assessed parental effects of conditional male ARTs on sons' ARTs in arrhenotokous spider mites Tetranychus urticae. Arrhenotoky, that is, males arising from unfertilized and females from fertilized eggs, sets the stage for sexual and transgenerational conflicts between male mates and females and their sons. Male ARTs of T. urticae are dichotomous, fighting and sneaking, and apparent in male–male combat and pre‐copulatory guarding behaviour. Due to haplodiploidy, male ARTs can only exert non‐genetic effects on sons of their mates. We hypothesized that parental ART effects are likely to occur in T. urticae because maternal ART mating status (unmated, sneaker‐ or fighter‐mated) is indicative of the offspring' social environment and ART flexibility rather prevails in younger than older males. Fighter‐mated mothers produced more offspring than unmated mothers and had a more daughter‐biased offspring sex ratio than unmated and sneaker‐mated mothers. Sons of fighter‐mated mothers were more likely to guard and did so earlier than sons of unmated and sneaker‐mated mothers. Unmated and sneaker‐mated, but not fighter‐mated, mothers produced sneaker sons that were quicker to start guarding than were fighter sons. Proximately, parental ART effects on sons' ARTs were most likely mediated by differences in seminal fluids. Ultimately, observed alterations of sons' ARTs represent adaptive maternal responses to ART phenotypes rather than manipulation by male mates. Fighter‐mated mothers tuned filial ARTs to male‐competitive environments whereas unmated and sneaker‐mated mothers tuned them to benign environments. Observed alterations in reproductive traits of fighter‐mated mothers suggest adaptive manipulation by the fighter phenotype or aligned male and female interests. Overall, our study documents previously unknown transgenerational ART effects on haploid sons' ARTs. A free Plain Language Summary can be found within the Supporting Information of this article.

Selection on growth rates via a trade-off between survival to sexual maturity and longevity in the swordtail fish Xiphophorus multilineatus

There is growing evidence across taxa for a mortality-growth rate tradeoff, however the extent to which individuals experience selection both for and against growing faster in the wild can be difficult to assess. We used otoliths to assess growth rates in the wild for Xiphophorus multilineatus, a species of swordtail fish with genetically influenced male alternative reproductive tactics. The ARTs are thought to be maintained due to a trade-off between a higher probability of reaching sexual maturity (smaller sneaker males) and maturing later as a large male with higher mating success (larger courter males). We show that the early juvenile growth rates of the subadult courter males were faster as compared to the other juveniles, potentially suggesting selection for growing faster to increase the probability of reaching sexual maturity. However, variance in the early juvenile growth rates of adult courter males was reduced (truncating high values) as compared to the subadult courter males and overall growth rates were faster in the subadult courter males than the adult courter males. These results support a cost of growing faster as juveniles: reduced longevity as an adult. We also detected a negative relationship between the early growth rates of females and their age, further supporting a longevity cost to growing faster. While both male ARTs are likely to experience stabilizing selection on growth rates, the differences between the morphs in how they optimize this tradeoff in relation to overall fitness (courters optimize growing faster to increase probability of reaching sexual maturity, sneakers optimize longevity as adults) has the potential to lead to disruptive selection between the ARTs on growth rates. We show that the data collected here is consistent with the “growth-mortality optimization” hypothesis and highlight some of the challenges that stabilizing selection presents for examining adaptive variation of growth rates in a natural environment.

Pause and travel: How sneakers approach closer to spawning sites under territorial vigilance

Male alternative reproductive tactics typically consist of territorial and sneaking tactics. In substrate-brooding fishes, sneakers try to steal fertilizations by suddenly rushing towards females from outside the spawning sites, but they are usually caught through territorial vigilance before rushing. Nevertheless, attention is seldom paid to how sneakers overcome territorial vigilance, which limits the ecological and evolutionary understanding of alternative reproductive tactics. I addressed this issue in the triplefin blenny, Enneapterygius etheostoma, by analysing sneaker behaviour recorded in the wild. Prior to rushing, sneakers gradually got closer to the spawning sites while repeatedly pausing and moving forwards but spent most of their time pausing. They moved slowly for short distances. Territorial males detected about three-quarters of the sneaking attempts. A sneaker was detected usually immediately after starting to move, indicating that movement was a major cause of sneaking failure. Longer and faster movements were detected more frequently, particularly further from spawning sites. Movements were also detected more when territorial males faced towards, rather than away from, the sneakers. This suggests that both sneaker performance and the attentive state of territorial males affect sneaking success. Sneakers more frequently started moving from behind territorial males than from in front of them, and were then less frequently detected. In sum, sneakers seemed to conceal their movements through pause-travel locomotion, adjusting their movements and choosing favourable situations. Nevertheless, they were still detected by motion-sensitive territorial males.

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

BackgroundAlternative 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.

Growth and otolith morphology vary with alternative reproductive tactics and contaminant exposure in the round goby Neogobius melanostomus

Round goby Neogobius melanostomus sagittal (saccular) otolith morphology was compared between males of the two alternative reproductive tactics (termed guarder and sneaker males) and between males captured from sites of high or low contamination. Otolith size increased with fish size and also displayed an ontogenetic shift in shape, becoming relatively taller as otoliths grew in size. Despite a considerable overlap in age between males adopting the two reproductive tactics, size-at-age measurements revealed that guarder males are significantly larger than sneakers at any given age and that they invest more into somatic growth than sneaker males. Controlling for body size, sneaker males possessed heavier sagittal otoliths than guarder males. Subtle otolith shape differences were also found between the two male tactics and between sites of high and low contaminant exposure. Sneaker males had relatively shorter otoliths with more pronounced notching than guarder males. Fish captured at sites of high contamination had otoliths showing slower growth rates in relation to body size and their shapes had more pronounced caudal points and ventral protrusions when compared with fish captured at sites of low contamination. The results are discussed in relation to life-history tradeoffs between the male tactics in terms of reproductive and somatic investment as well as the putative metabolic costs of exposure to contaminants. Overall, this study reveals that male alternative reproductive tactics and environmental contaminants can have small, yet measurable, effects on otolith morphology and these factors should be accounted for in future research when possible.

Resource availability, mating opportunity and sexual selection intensity influence the expression of male alternative reproductive tactics.

The expression of alternative reproductive tactics can be plastic and occur simultaneously depending on cues that vary spatially or temporally. For example, variation in resources and sexual selection intensity is expected to influence the pay-off of each tactic and shape the decision of which tactic to employ. Males of the nuptial gift-giving spider Pisaura mirabilis can adopt three tactics: offering a genuine prey gift, a 'worthless' non-nutritious gift or no gift. We hypothesized that resources and/or male body condition, and mating opportunity and sexual selection intensity, vary over the course of the mating season to shape the co-existence of alternative traits. We measured these variables in the field over two seasons, to investigate the predictions that as the mating season progresses, (i) males become more likely to employ a gift-giving tactic, and (ii) the likelihood of switching from worthless to genuine gifts increases. Prey availability increased over the season and co-varied with the propensity of males to employ the gift-giving tactic, but we found no support for condition-dependent gift giving. Males responded to an increase in female availability by increasing their mating effort (gift production). Furthermore, the frequency of genuine gift use increased with sexual selection intensity, consistent with the assumption that sperm competition intensity increases with time. Our results suggest that the frequency of alternative tactics is shaped by seasonal changes in ecological factors and sexual selection. This leads to relaxed selection for the gift-giving tactic early in the season when females are less choosy and resources more scarce, and increased selection for genuine gifts later in the season driven by mating opportunity and risk of sperm competition.