Male dimorphism, territoriality and mating success in the tropical damselfly, Paraphlebia zoe Selys (Odonata: Megapodagrionidae)

The tropical damselfly Paraphlebia zoe has two male morphs: a black-winged (BW) male which is associated with territorial defense of oviposition sites; and a hyaline-winged (HW) male similar in appearance to females, and, compared to the black morph, less frequently found defending territories. In a wild population of this species, we first assessed the relationship between phenotypic traits [male morph, size and territorial status (being territorial or non-territorial)], their role on mating success, and the degree to which a particular territory may contribute to male mating success. Second, to relate a physiological basis of being territorial we compared both morphs in terms of muscular fat reserves and thoracic muscle, two key traits related to territory defense ability. Males of both morphs defended territories although the BW males were more commonly found doing this. BW males were larger than HW males and size predicted being territorial but only within HW males (territorial males were larger) but not in BW males. Male mating success was related to territorial status (territorial males achieved a higher mating success), but not to morph or size. Furthermore, territory identity also explained mating success with some territories producing more matings than others. The BW morph stored more fat reserves which may explain why this morph was more likely to secure and defend a place than the HW morph. However, the HW morph showed higher relative muscle mass which we have interpreted as a flexible strategy to enable males to defend a territory. These results are distant to what has been found in another male dimorphic damselfly, Mnais pruinosa, where the advantage of the non-territorial morph relies on its longevity to compensate in mating benefits compared to the territorial morph.     

Nutritional reserves regulate male participation in Mediterranean fruit fly leks

1. The mating system of Mediterranean fruit flies ( Ceratitis capitata , Diptera: Tephritidae), is based on male leks that form on the foliage of trees. Following observations that not all males participate in leks, the hypotheses that (a) small males are absent from leks and (b) males with inadequate nutrient reserves are unable to participate in leks were examined.
2. The size and weight of lekking males ( n = 183) and resting males captured at the same time in the vicinity of leks ( n = 148) were established. In addition, using biochemical techniques, the amounts of sugar, glycogen, lipid and protein in each individual were established quantitatively.
3. There was no significant size difference between lekking and resting males. However, lekking males were significantly heavier and contained significantly more sugars and protein than resting males.
4. In conclusion, leks are exclusive, and only males with adequate nutritional reserves may join. Thus, in this species, reproductive success is closely linked to foraging success.     

Increased energy investment in testes following territory acquisition in a maternal mouthbrooding cichlid

Underwater observations conducted in Lake Tanganyika showed that males of a maternal mouthbrooding cichlid, Petrochromis fasciolatus, defended a mating territory for at least several months, but left at approximately noon every day. After the experimental removal of males from their territories, new owners occupied the vacated territories within several days. New owners exhibited higher body-condition factors and fat indices than the original owners. These results suggest that the new owners had not previously occupied a territory, considering the physical exhaustion of owners owing to the energy expenditure on territory maintenance and mating behaviors and a limited time for feeding. Original owners had heavier testes than new owners, despite similar body sizes. This disparity in testis weight suggests that energy investment in testes increases following territory acquisition. Among males that newly occupied a territory during the observation period, larger individuals occupied territories sooner, suggesting that large body size facilitates competition for territory. It is concluded that energy investment in testes is delayed for somatic growth until territory acquisition.     

To lek or not to lek: mating strategies of male fallow deer

We studied the mating system of fallow deer (Dama dama) for6 years in central Italy. Males in this population could defendterritories that were either single, clumped in leks, or satelliteto leks. The most highly successful males in our study werein leks. When we considered all males, there were no significantdifferences in average copulatory success according to territorytype because many lek males did not achieve any copulations,which were seen in only a few lek territories. The variancein copulatory success, however, was much greater for leks thanelsewhere. Single territories were occupied for shorter timesduring the rut than lek territories. Fighting among males wasmore frequent in the lek, even when we excluded highly successfullek males from the analysis. Chases of nonterritorial malesand harem size were correlated with the number of copulationsachieved by individual males, but did not vary according toterritory type. Copulatory success of some individuals increasedwith age, but there were no age differences among males holdingdifferent types of territories. Satellite males switched tolek territoriality in the course of one rut, but switches fromsingle territory to lek territory were rare. We suggest thatmales in single territories are inferior competitors that selecta low-risk, lowbenefit strategy, whereas those in lek territorieswhere no copulations were seen may be attempting to establishthemselves on the lek to increase their copulatory success infuture years.     

Lekking, resource defense, and harassment in two subspecies of lechwe antelope

For lek-breeding in ungulate populations to continue, benefitsto males defending lek territories and to females visiting leksmust outweigh the costs. In this study, Kafue lechwe males onleks gained higher mating rates than nonlekking males, a resultof sexually receptive females leaving herds and aggregatingon leks. When the numbers of females on leks were experimentallyreduced, benefits to males decreased, resulting in males graduallyabandoning lek territories. A comparison with a population ofnonlekking, resource-defending black lechwe showed that matingattempts by estrous females in herds were disrupted by harassingmales eight times more frequently in a population of lek-breedingKafue lechwe than in the nonlekking black lechwe. Despite thefact that there were fewer Kafue lechwe females on single territories,harassment of estrous females by males was greater on singleterritories of Kafue lechwe than on leks and greater than onblack lechwe resource territories. Females were also absenton Kafue lechwe single territories for long periods becauseof erratic, widespread movements of compact herds resultingfrom unpredictable distributions of resources. In contrast,black lechwe females were more evenly dispersed over homogeneousresources and for a given territory, females were likely tobe present most of the time. Therefore, unlike black lechwe,male Kafue lechwe find it uneconomical to defend resource territories.Thus, costs to estrous females mating off leks and the absenceof benefits to males attempting to defend resource-based territoriesmay be important cofactors in the appearance of lek-breedingin some ungulate populations     

Black holes, mate retention, and the evolution of ungulate leks

In some ungulates living in unstable herds, females in estrusleave their usual groups and join males defending mating territories.During the 12-24 h before mating, females commonly move severaltimes between males. These movements are commonly caused byharems being disrupted by young males or by overenthusiasticcourtship by the territorial male. When females leave a territorythey typically move to its nearest neighbor. Under these circumstances,clusters of territories can retain estrous females until theymate and leave the lek. This paper develops a model to investigatethe benefits of defending clustered versus dispersed territoriesto males and the consequences of variation in the rate of femalemovement between territories (P_m) and the tendency for femalesto move from one territory to a neighboring territory (a). Wherefemales move between territories at least once every 24 h (P_m< 0.04) and usually move to neighboring territories (a <0.5), the mating success of males is inversely related to thedistance from their territory to its nearest neighbor, and malesdefending clustered territories have higher mating rates thanthose defending dispersed territories. This process may be importantin the initial evolution of ungulate leks, which may resembleblack holes, attracting and retaining estrous females untilthey mate and their estrus ceases. It provides one possibleexplanation of the evolution of ungulate leks that does notrely on female preferences for mating with particular phenotypiccategories of males.     

Fat and sassy: factors underlying male mating success in a butterfly

Theory predicts that male mating success depends on resource holding potential (RHP), which is reflected by proxies of condition, such as body mass, fat content, strength, or weaponry. In species lacking any physical means to inflict injuries upon combatants, such as butterflies, the factors determining mating success are less clear. Against this background, we explored the determinants of male mating success in the tropical butterfly Bicyclus anynana Butler (Lepidoptera: Nymphalidae: Satyrinae), by comparing physiological, immunological, and morphological traits between winning and losing males. Our results showed that successful males are characterized by a better flight performance, evidenced by having longer wings, a heavier thorax, a lighter abdomen, a higher fat content, and higher phenoloxidase expression levels than their unsuccessful counterparts, when being compared after their first mating. Males that won three consecutive trials against the same combatant were also characterized by a better flight performance, having larger forewings, a higher body mass, and a higher fat content. Thus, successful males were larger and in better condition than unsuccessful ones. Strikingly, many differences found indicated an enhanced flight performance for the former, which we suggest ultimately plays the key role for male mating success in B. anynana. As fat is the main energy source for flying insects, being crucial to flight endurance and in turn presumably to male mating success, it may represent a key determinant at the proximate level.     

Diet and size influence sexual advertisement and copulatory success of males in Mediterranean fruit fly leks

1. The objective of the work reported here was to test the hypothesis that in insects that invest considerable energy in sexual displays and courtship, foraging successfully for food affects their subsequent performance and copulatory success in leks. Accordingly, the interactions between body size and diet on initiation of lekking behaviour and copulatory success in male Mediterranean fruit flies Ceratitis capitata (Diptera: Tephritidae) were investigated. 2. Protein‐fed males were heavier and contained more protein and less lipid reserves than protein‐deprived males. Protein‐fed males were more likely to emit pheromone in leks and, consequently, were more likely to copulate than protein‐deprived males. Furthermore, protein‐fed males tended to start calling earlier than their nutritionally deprived competitors. 3. Though size was not related to initiation of lek behaviour, large males were more likely to copulate than small males. Among protein‐fed males, large individuals tended to mate earlier than smaller individuals. 4. Generally, in lek mating systems where a considerable investment of time and energy is required by males, foraging successfully for nutritional resources prior to engaging in territorial or courtship behaviour is essential for reproductive success.     

Male Cheetah Social Organization and Territoriality

Patterns of territory ownership in male cheetahs inhabiting the Serengeti Plains are described, and factors affecting territorial behaviour are examined. Body size and age were factors influencing whether males became territorial, and single males usually had to join up with others in order to oust residents. Both size of male coalition and body size of its members were associated with length of tenure on territories. Limited data suggest that territory owners were probably no more likely to encounter females than were non-territorial males but there was a suggestion that they suffered lower survivorship costs than non-territorial males.     

Uganda kob prefer high-visibility leks and territories

In lekking species, where males provide estrous females withlittle more than sperm, it has been widely supposed that theonly possible benefits to females of mate choice are genetic.We studied female choice of leks and territories in a reduncineantelope, the Uganda kob (Kobus kob thomasi), and found thatfemales consistently preferred high-visibility mating sites.Leks were elevated and had shorter grass and fewer thicketsthan the surrounding areas. Changes in the number of male andfemale kob on 10 leks were correlated with changes in surroundinggrass height, and both females and males preferred leks withexperimentally reduced grass height over neighboring controls.Within a lek, territory popularity was the primary determinantof male daily mating success, and females preferred territoriesrelatively far from thickets, but removal of thickets did notaffect female territory preferences. Because lion hunting successon kob increases with grass height and thicket density, femalesmay benefit directly from these preferences by reducing therisk of predation.     

Differences in size and energy content affect the territorial status and mating success of a neotropical dragonfly

In male odonates, both size and fat content are related to territory defence and mating success. Males that are larger and have higher energy reserves win relatively more disputes for territory and attract more females. Wing colour has also been regarded as a mechanism that influences agonistic behaviour between males, as wing pigmentation might be regarded as a sign of male quality. In this study, we analysed whether a set of male physical (body size and wing colour), physiological (body fat content) and behavioural (disputes between males) characteristics were involved in the territory defence and mating behaviour of the neotropical dragonfly Zenithoptera lanei Santos, 1941 (Anisoptera: Libellulidae). Males were characterised as territorial whenever they warded‐off other males and remained in the same place within the pond for two consecutive days. In general, these territorial males were larger and had more abdominal and thoracic fat, engaged in pursuits more frequently, spent more time on sexual behaviour and female guarding, and mated more in comparison to subordinate males. By evaluating whether the percentage of wing area covered by black ink influenced male behaviour, we found that territorial males tended to act aggressively towards other males whose wings were partially painted, and sexually towards females irrespective of wing area painted. In Z. lanei, both body size and fat content play a role in defining territoriality. By subduing competitors and dominating preferred locations within high‐quality sites, these males are likely to be visited by females and engage in mating.     

Components of male fitness in relation to body size in Epirrita autumnata (Lepidoptera, Geometridae)

Abstract. 1. The effect of body size on different components of male fitness was studied for Epirrita autumnata , a geometrid known for its eruptive population dynamics. Body size is the main determinant of female fecundity in this species.
2. Longevity of males was found to have a weak negative correlation with body size at low temperatures. No significant correlation was found at higher temperatures.
3. We found no correlation between male size and female fecundity or egg size which is consistent with the small size of spermatophores in this species.
4. Small and large males were equally successful when allowed to compete for females in laboratory conditions.
5. In one or two field collections, males found mating were larger than males found singly. Large males also had an advantage in finding of virgin females, offered experimentally. No size-assortative mating was recorded.
6. We conclude that size-dependent mate location ability is the factor accounting for most of the variance in male fitness in E.autumnata. The dependence of fitness on body size may well be equally strong in males and females.     

Mating in a viscous universe: the race is to the agile, not to the swift

Charles Darwin's theory of natural selection has at its focal point the mating success of organisms. Among male animals, large body size is widely seen as the principal determinant of mating success. However, where mating takes place in a three-dimensional arena such as water, the arboreal habitat or air, small size with its concomitant aerobatic advantages might be advantageous. Despite considerable interest, the relationship between aerobatic ability and mating success has not yet been demonstrated in a single animal species. Here, we test the hypothesis that the known mating success of small male midges is due to their greater aerobatic ability. To do this, male midges collected from leks in the wild were flown and their flight paths in free flight were recorded on high-speed cameras in the laboratory. Four flight parameters that would seem relevant to male mate acquisition in flight, i.e. acceleration, maximum speed, tortuosity and turn-rate, were analysed with respect to body size. We show that, while in terms of maximum speed there was no detectable difference between small and large males, small males outperformed larger ones with respect to acceleration, tortuosity and turn-rate. We conclude that the hypothesis that small males gain their mating advantage through aerobatic superiority is consistent with the observations reported here.     

Reproductive success in male Japanese minnows,Pseudorasbora parva: observations under experimental conditions

To evaluate the spawning success of male Japanese minnows,Pseudorasbora parva, and female mate choice, spawning behaviour was observed under both artificial and experimental conditions. Larger males had larger territories and greater reproductive success. The body weight of territorial males decreased during the maintenance of territories, while that of non-territorial males increased significantly. When the weight of non-territorial males exceeded that of territorial males, the former began to establish new territories on the substrate, suggesting a conditional strategy by non-territorial males to trade off immediate reproductive success with growth and hence improve future reproductive success. Females chose males with larger body size, probably based on dominance rank rather than the quality (or size) of territory. It was concluded that females choose males of higher dominance rank and that males compete for large territories, both of which play an important part in male reproductive success.     

Role of sexual and natural selection in evolution of body size and shape: a phylogenetic study of morphological radiation in grouse

We use standardized independent contrasts (SICs) to elucidate the effect of ecology and mating systems on morphological radiation in grouse. The analysis of SICs for 38 skeletal measurements from 20 taxa, showed that changes in mating system had a significant effect on body size of both sexes. Sexual size dimorphism in grouse is consistent with Rensch's rule; the slope of the regression of male vs. female size SICs was 1.4, significantly >1. Changes in habitat were associated with accelerated rates of evolution of body proportions. SICs for male and female scores of size independent factors were directly proportional to each other (slope = 1), indicating extreme similarities between male and female ecology. Females, however, were better adapted to longer, more energy efficient flight than males. Size independent morphological differences among grouse are adaptive and are related to the differences in habitat and foraging behaviour among the species.     

Effect of larval food stress on male adult behaviour, morphology and reproductive investment in the butterfly Pararge aegeria

Males of several animals increase their reproductive success by territorial behaviour. In butterflies, males may defend a territory (i.e., territorial perching tactic), but this is assumed to be an energetically costly way to locate mates. Limitations of the energy budget may affect fight performance, and may, consequently, force males to adopt an alternative non-territorial searching behaviour (i.e., patrolling tactic) to maximize reproductive success. In this study, we tested to what extent behavioural tactics adopted by adult males of the butterfly Pararge aegeria (L.) were affected by the nutritional conditions during the larval stage. We compared the occurrence of territorial versus patrolling behaviour, lipid mass, flight muscle ratio, metabolic rate and spermatophore production of low quality males that were reared as a larva on drought-stressed host plants and control, high quality males. Low quality males were less likely to adopt the territorial perching tactic and emerged as adults with lower lipid mass than high quality males, but they were able to restore their lipid mass through adult feeding (and perhaps the breakdown of flight muscles). Host plant quality also affected spermatophore size. Independent of the larval food treatment, territorial perching males metabolised more lipids than non-territorial males, produced larger spermatophores and copulated for longer than males adopting non-territorial behaviour. We discuss the results relative to the co-existence of the behavioural tactics (perching and patrolling).     

On the maintenance and origin of alternative strategies in the Ruff Philomachus pugnax

This paper has tried to answer the question of how the independent and the satellite strategy of the Ruff originated and has been maintained during evolution. It is not intended as a report of a piece of completed research but gives a number of tentative, but testable hypotheses. Data are presented that independent males and satellites are equally successful in copulating, provided that almost all copulations occur on leks, and independent males and satellites spend an equal proportion of their time on leks. The extent that males with the different strategies are attached to leks is analysed. Within the group of independent males, considerable differences exist: a resident male is strongly attached to only one particular lek and a marginal male seems to sample many leks. A satellite male behaves intermediately: he is attached to a limited number of leks. The mechanism for the maintenance of both strategies could not be explained by competition for resources (copulations). Contests between independent males and satellites are asymmetric, the satellite being the weaker contestant. The mechanism seems to be due to enlarging the accessibility of the resource by cooperation between both strategies. The ideas on the origin of the system are based mainly on the behaviour of females. There is no relation between the distribution of leks and the size of a female's foraging area, except that most leks are situated along the migration route. It further seems that the number of copulating females in the Netherlands is larger than the number of males on leks, but the number of breeding females is much lower. It is suggested that many females copulate on migration, which is related to extreme breeding conditions in the north of the range. Apart from a change in the sex ratio from south to north, a change in the proportion of satellites is also predicted. The origin of the system is ascribed to the incompatibility between favourable food conditions for chicks and further possibilities for inter-male competition on leks in the same area. The satellite strategy is considered as being derived from a non-competitive strategy accompanying females on migration. In the phase of cooperation between resident and satellite males, individual recognition became important. This could be the factor underlying the evolution of white plumages in satellites and the extreme plumage diversity in independent males.     

Male Parasitic Spawning in Two Species of Triplefin Blenny (Tripterigiidae): Contrasts in Demography, Behaviour and Gonadal Characteristics

Axoclinus nigricaudus and A. carminalis are blennioid fishes from the Gulf of California, Mexico. Males show alternative mating tactics; territorial individuals attract females while non-territorial individuals parasitically spawn with territorial males' females. Demography and gonadal characteristics were related to the degree of parasitic spawning (sperm competition) within and between species. Males of both species showed bimodal size distributions that largely reflected the two tactics. Territorial males spawned much more frequently than non-territorial males, but parasitic spawning was significant. Non-territorial males were more common and rates of parasitic spawning were much higher in A. nigricaudus indicating that it experienced higher sperm competition. In agreement with sperm competition theory, relative testis weight was greater in A. nigricaudus. In A. nigricaudus, the majority of parasitic matings were by non-territorial males, whereas in A. carminalis, both male-types parasitised frequently. Accordingly, only in A. nigricaudus did non-territorial males have relatively heavier testis than territorial males. In both species the testicular gland, that produces accessory products for sperm transfer, was large in territorial males, but small or undeveloped in non-territorial males suggesting male-types differ in fertilisation mode.     

A selective trade-off for territoriality and non-territoriality in the polymorphic damselfly Mnais costalis

Males of the damselfly Mnais costalis occur as territorial orange-winged 'fighter' males or non-territorial clear-winged 'sneaker' males. Their morph life histories differ considerably but the estimated lifetime reproductive success is the same for the two morphs. In this study we compared the developmental and reproductive costs associated with the two morphs. Orange-winged male and female reproductive costs resulted in a decline in adult fat reserves with increasing age. In contrast, the fat reserves of clear-winged males remained constant with adult age. Body size was positively correlated with mating success in orange-winged males, but had no influence on the mating success of clear-winged males. The orange-winged male flight muscle ratios (FMRs) were significantly higher than the clear-winged male and female FMRs. However, there was no difference in the size-corrected fat reserves of the two morphs; both had higher fat reserves than females. The gain in mass between eclosion and reproduction in orange-winged males and females was almost double the mass gained by clear-winged males, suggesting that clear-winged male development is less costly. An experiment in which pre-reproductive levels of nutrition were manipulated confirmed this.