Space,density and extra-pair matings have opposing impacts on male and female reproductive success

Many territorial species have a mating system characterized by males establishing home ranges in the breeding grounds prior to females, resulting in males competing for territories and females choosing a mate upon their arrival. It remains unknown, however, how the outcomes of decisions surrounding territory establishment and mate choice are influenced by the spatial configuration of the breeding grounds. We use a spatially explicit, individual-based model to investigate the sex-specific effects of these decisions on reproductive success. In our model, males that arrive earlier obtain higher quality territories and improve their chances for extra-pair copulations. Females can choose their mate to maximize the quality of the male or to attempt to minimize the density of other females near their nesting site to avoid competition. Females therefore face a tradeoff between high-density regions around high-quality males and low-quality males in areas of low competition. Our model predicts a negative correlation between male and female reproductive success under a wide range of conditions when the majority of the territories are on the margins of the breeding area. Most notably, this sexual conflict arises as an edge effect suggesting that fragmentation of breeding habitats could impact the consequences of mate choice in many species with territorial breeding habits.     

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.     

Correlates of male mating success and female choice in a lek-breeding antelope

We investigated factors underlying variation in male matingsuccess in Uganda kob (Kobus kob thomasi), a lek-breeding antelope.We found that only heavy (and, possibly, relatively old) malesheld lek territories and that female choice was an importantdeterminant of nonrandom mating patterns at leks. Our measureof male mating success was closely related to the historicalpopularity of the territory that a male defended, and individualfemales showed consistent preferences for particular lek territories,despite changes in territory ownership. Male success increasedwith body weight and declined independently of territory effectsduring each bout of lek territory tenure. We also found someevidence that female kob copied one another's choice of matesbecause females arriving at a lek tended to join territoriesthat already had relatively large harems on them. When comparedacross leks, average male mating success increased with leksize. Our results suggest that female kob may use a suite ofmale- and territory-based cues in mate choice at leks and, asa result, mate with particularly large males. However, we wereunable to determine whether female kob gain any direct or indirectbenefits through mate choice at leks.     

Relatedness,body size and paternity in the alpine newt,Triturus alpestris

Sexual selection has traditionally been investigated assuming that male quality is as skewed as patterns of male reproductive success can sometimes be. Recently, female choice has been investigated under the model of genetic compatibility, which assumes that each individual female has her own 'best' mate and there is no overall optimal choice for all females. We investigated female mate choice in the newt species Triturus alpestris, a member of a genus where female choice has been investigated only within the context of the optimal male (female choice for condition-dependent traits). We provided females with two males that differed in one condition-dependent trait (body size) and overall genetic composition. Both male body size and female body size did not influence paternity, but the degree of genetic relatedness between females and potential mates did. Two components of fitness (fecundity and hatching success) did not differ between singly and multiply sired clutches, indicating that females do not employ polyandry as a means of increasing offspring fitness through genetic bet-hedging. Instead, we hypothesize that females may mate initially for fertility assurance, but prefer less-related males as the most genetically compatible mates.     

Red coloration of male northern cardinals correlates with mate quality and territory quality

I investigated how mate quality and territory quality influencean extravagant ornament in a socially monogamous species thatdefends multipurpose territories. Northern cardinals (Cardinaliscardinalis) are a highly dichromatic, socially monogamous species,and males are a brilliant red. I conducted a 3-year field studyof northern cardinals and found that redder males produced moreoffspring in a breeding season. Two selective factors mediatedthis fitness gain. Redder males were paired with earlier breedingfemales, an established measure of mate quality in birds. Second,redder males obtained territories of higher quality, as measuredby vegetation density. Interactions among these factors werealso important in explaining variance in male reproductive success.Multivariate analysis indicated that earlier breeding increasedreproductive success independent of territory quality. In turn,territory quality contributed to male reproductive success throughits effect on nest survival and possibly through its role in attractingan earlier breeding female.     

Adaptive female choice for middle-aged mates in a lekking sandfly

Most theoretical models of age-related mate choice predict that females should prefer older males because they have proven survival ability. An alternative view is that older males represent inferior mates because of negative genetic correlations between early and late fitness components, or because older males have traded off longevity against other fitness components, have accumulated deleterious germ-line mutations, or are less well adapted to current conditions than more recently born individuals. While numerous studies have reported female choice for older males, few have explicitly examined the fitness consequences of such a preference. We present evidence from a lekking sandfly, Lutzomyia longipalpis, showing that choosy females discriminate against older males and gain a fitness benefit from their choice. When permitted free choice from an aggregation consisting of males aged zero to two days (young), four to six days (middle-aged) and eight to ten days (old), females preferentially mated with middle-aged males, but all measures of female reproductive success were independent of male age. In contrast, when a second set of females was randomly assigned single virgin males of known age, the eggs of those paired to old mates exhibited lower hatching success than the eggs of females mated to young or middle-aged males. These results suggest that females avoid mating with older males because they represent poorer quality mates. Age-related differences in male quality may have a genetic basis, but could equally well arise through a phenotypic decline in sperm quality or sperm transfer ability with male age. The lack of evidence of female discrimination against older males from other studies may be because these did not explore the reproductive success of the full age range of males.     

Direct and indirect mate choice on leks

Indirect mate choice is any behavior that restricts the individual's set of potential mates without discrimination of mate attributes directly, for example, by having preferences about where to mate. We analyzed a 14-year data set from great snipe (Gallinago media) leks for evidence of indirect mate choice based on relative and absolute position of lek territories. We found little or no effect of the centrality of territories on mating and no between-year consistency in the spatial distribution of matings within leks. Instead, the probability of matings occurring at a particular site increased if the current territory owner had mated the previous year. Furthermore, individual females returned in later seasons to mate with the same male as previously rather than at the same site. Previous work found that male interactions and dominance do not control matings and that females are very choosy about which territory they mate in. Here we show that this is because of the male occupying the territory rather than its position. We therefore conclude that direct female mate choice is the main behavioral process affecting variation in mating success among great snipe males, unlike in some lekking mammals where male competition and/or indirect mate choice appears more important.     

Territory and male quality do not influence settlement of yearling female willow ptarmigan

A common assumption in territory and mate selection models isthat individuals evaluate the qualities of territories and/orpartners and then choose the best ones. We determined whetherthis assumption was correct for yearling female willow ptarmigan(Lagopus lagopus). Yearling females did not choose partnersbased on the characteristics of the territories or of the malesthat we measured. In addition, the first females to settle didnot appear to obtain better territories or better partners thanthose settling later; date of settling was not related to subsequentsurvival, reproductive success, or quality of chicks produced.To evaluate whether choices of territories and partners wereconsistent among females, we manipulated settlement such thattwo sets of yearling females had the same suite of territoriesand males available. We found no consistent patterns of territoryand mate choice. We concluded that, in this population, yearlingfemales did not choose where to settle based on the relativequalities of territories or partners. Females may have beenunable to assess differences among territories when settlingbecause all territories were covered with snow.     

The Haremic Mating System and Mate Choice in the Wide-Eyed Flounder, Bothus podas

The social structure and reproductive behaviour of the wide-eyed flounder, Bothus podas, was studied in the coastal waters around the Azorean Islands. Both sexes are territorial throughout the year. Adult males defend large territories, which include several smaller female territories. Intraspecific agonistic behaviour was frequent and differed between sexes: males were more aggressive towards other males, while females were only aggressive towards each other and juveniles. During the reproductive season and only at dawn, territorial males court and mate successively with females in their territories, and females seem to show mating fidelity to their dominant male. Such territoriality and mating patterns indicate a haremic social system in the wide-eyed flounder. In order to identify potential factors influencing female mate choice acting on this haremic system, we examined male mating success and some of its potential correlates. We found no evidence for female preference for any of the males' physical or territory characteristics. However, courtship effort was strongly correlated with the total number of attempted and successful spawnings, indicating that females seem to mate preferentially with males that court them more vigorously. Thus, our data suggest that courtship plays an important role in determining male mating success in the wide-eyed flounder and, that it may possibly serve as an honest indicator of male `quality' for female choice.     

Effects of tapeworm infection on male reproductive success and mating vigor in the red flour beetle,Tribolium castaneum

Parasites may exert negative effects on host survivorship and reproductive success. The effects of parasites on female host fitness have been well documented; however, the effects of parasites on the reproductive success of male hosts and particularly the underlying mechanisms that alter male fitness are not well understood. Previous studies demonstrated that infection by rat tapeworm (Hymenolepis diminuta) reduced the fitness of male red flour beetles (Tribolium castaneum) in an environment of female mate choice and strong male-male competition. The present study determined the role of female mate choice and male insemination capacity on observed fitness reduction of male beetles by the tapeworm parasites. We found that infected males showed reduced mating vigor and consequently inseminated fewer females than did uninfected males. Specifically, tapeworm infection reduced the number of offspring sired by a male by 14-22% even when male-male competition and female mate choice were absent. Further, the insemination capacity of males diminished by 30% because of infection. Female beetles did not discriminate against infected males in precopulatory mate choice experiments. Copulatory courtship, a determinant of postcopulatory female choice, was not significantly different between infected and uninfected males. Hence, we concluded that female beetles did not show either pre- or postcopulatory choice against tapeworm-infected males. Therefore, tapeworm-induced reduction in the reproductive success of male beetles possibly results from altered reproductive biology, such as lower mating vigor and decreased sperm quantity or quality.     

The social organization of feral peafowl

Peafowl are usually reported to have a mating system based on harem defence by adult males. In a small feral population near Oxford, males defended small (<1 ha) territories while females remained in one flock that ignored male territory boundaries. After mating, females become solitary. At no time did a female associate selectively with one male or remain within his territory, nor did males attempt to follow or guard female groups. Two out of four males were seen to mate. These differed from the other two in being neither very old nor very young; they held territories smaller than that of the young male and were no larger or longer-tailed. However, they spent more time displaying. We suggest that peafowl have a mating system similar to a lek: males defending small, clumped territories visited by females for mating.     

Indirect mate choice, direct mate choice and species recognition in a bower-building cichlid fish lek

Sexual selection arising through female mate choice typically favours males with larger, brighter and louder signals. A critical challenge in sexual selection research is to determine the degree to which this pattern results from direct mate choice, where females select individual males based on variation in signalling traits, or indirect mate choice, where male competition governs access to reproductively active females. We investigated female mate choice in a lekking Lake Malawi cichlid fish, Hemitilapia oxyrhynchus, in which males build and aggressively defend sand 'bowers'. Similar to previous studies, we found that male reproductive success was positively associated with bower height and centrality on the lek. However, this pattern resulted from males holding these territories encountering more females, and thus their greater success was due to indirect mate choice. Following initial male courtship, an increase in the relative mating success of some males was observed, but this relative increase was unrelated to bower size or position. Crucially, experimentally manipulating bowers to resemble those of a co-occurring species had no appreciable effect on direct choice by females or male spawning success. Together, these results suggest indirect mate choice is the dominant force determining male-mating success in this species, and that bowers are not signals used in direct mate choice by females. We propose that, in this species, bowers have a primary function in intraspecific male competition, with the most competitive males maintaining larger and more central bowers that are favoured by sexual selection due to higher female encounter rates.     

Nest and mate choice in the red bishop (Euplectes orix) : female settlement rules

We investigated female settlement in a colony of red bishops(Euplectes orix), a territorial and highly polygynous weaverbirdwidely distributed over sub-Saharan Africa. An earlier studyshowed that male reproductive success is mainly determinedby the number of nests a male builds in his territory, whichappeared to be a good indicator of male quality. Because malesprovide no parental care or food resources within the territory,females sharing a territory do not compete for material resourcesand might therefore be expected to settle preferentially interritories of males that build many nests to gain the possiblegenetic benefit of high-quality offspring. An analysis of femalesettlement, however, revealed that females did not show a preferencefor territories of males with many nests and that the distribution of female breeding attempts with regard to the number of vacantnests within a territory could be explained best by randomfemale settlement in 3 out of 4 years. Females settled moreoften than expected by chance (in 3 out of 4 years) in territoriesalready containing occupied nests, indicating that residentfemales did not discourage settlement of additional females.However, sharing a territory with other females might imposecosts in terms of an increased predation risk because nestsin territories that contained other nests with young sufferedfrom higher predation than nests in territories that did notcontain other nests with young. Females therefore might tradethe possible benefits of settling in territories of males withmany nests against the costs of sharing a territory with otherfemales. This might result in the mating pattern found withrandom female settlement and male reproductive success beingdirectly proportional to the number of nests built. We discuss possible implications of this mating pattern for sexual selectionon males.     

Correlation between male size and territory quality: consequence of male competition or predation susceptibility?

Territory characteristics correlate with male characteristics in several species. This can result from male competition for the best territories, or from males varying in their ability to pay other costs of territoriality, such as predation risk costs. In a population of threespine sticklebacks, Gasterosteus aculeatus , we found the biggest males to defend the biggest territories with a low structural complexity and a high female encounter rate. By experimentally manipulating competition intensity and habitat structure, we show that both male competition and predation exposure influenced the distribution of territories among males. Males increased the size of their territory when a neighbouring male was removed, whereas they reduced their territory when habitat complexity and cover from predators were reduced, with large males reducing their territory size less than smaller males. This suggests that large males occupy large, open territories both because of their superior competitive ability and because of their either lower predation susceptibility or higher risk-taking. Large, open territories were beneficial in mate attraction and male competition and predation exposure therefore biased mating opportunities towards large males. This suggests that cost of territoriality to males may reduce mate choice costs to females by securing that large males are encountered more often than small males, and by providing an additional cue, territory quality, which indicates which males are worth inspecting.     

Male Age Affects Female Mate Preference and Reproductive Performance in the Cabbage Beetle, <Emphasis Type="Italic">Colaphellus bowringi</Emphasis>

The influence of male age on female mate preference and reproductive performance in the cabbage beetle, Colaphellus bowringi was examined, using male and female adults of varying ages (young, middle-aged and old) after a single mating. In a simultaneous choice test, females of all age class preferentially mated with middle-aged males. Mating duration was positively related to male age. Longevity of females was not significantly affected by male age. Young females paired to middle-aged males had significantly higher egg production than those paired to old males, and the eggs of females paired to middle-aged males exhibited significantly higher hatching success than the eggs of females mated to young or old males. These results suggest that middle-aged males are more advantageous for female fitness than young and old males.     

Mate choice in Pied Flycatchers Ficedula hypoleuca: can females use song to find high‐quality males and territories?

High-quality male Pied Flycatchers Ficedula hypoleuca (defined by brighter plumage, better condition and more experience) have previously been shown to have larger syllable repertoires and greater song versatility than males of inferior quality. Thus, by preferring more complex songs, females could choose a high-quality male. Females may also use song as a cue to find a high-quality territory since early arriving males may obtain the best territories and these males have more complex songs than late-arriving males. We found that males with more complex songs had a greater chance of becoming paired and stayed unpaired for a shorter period than males with less elaborate songs. When controlling for arrival order, however, only strophe versatility was still correlated with pairing order. Males defending popular territories had more complex and longer songs and were also in better body condition than males in less popular territories. A multiple logistic regression showed that song length was important in explaining whether a male defended a popular nestbox or not. Thus, male arrival time seems to be important in deciding the quality of a male's territory, which in turn explains female choice. However, song quality seems to add important information. Thus, females could find both high-quality males and high-quality territories by using song cues during mate choice.     

Male Age and Experience Increases Mating Success but Not Female Fitness in the Mexican Fruit Fly

Male age and sexual experience are important condition parameters that can influence mate choice and female fitness, yet they are seldom studied simultaneously. Here, we investigated the effect of male age and previous sexual experience on mating success and female fitness in the Mexican fruit fly, Anastrepha ludens (Diptera: Tephritidae). Males were either young or old, sexually experienced or naïve. Older and sexually experienced males obtained more copulations. However, females did not receive benefits in terms of lifetime fecundity, fertility, or longevity from mating with these males. Results suggest that males become more competitive as they age and gain sexual experience and may be able to maintain a high quality ejaculate compared to young males. Older experienced males may be manipulating females into preferentially mating with them at no benefit to females. Alternatively, females may prefer mating with older more experienced males and possibly receive other indirect benefits, but this remains to be tested.     

Female Medflies Mate Selectively with Young Males but Gain No Apparent Fitness Benefits

Species in which female choice is not strongly shaped by male-controlled resources present a challenge to sexual selection research, because it is typically difficult to identify the male phenotypic cues used in female mate selection or the fitness benefits accruing from such selection. In such species, mate selection is presumably based on direct benefits associated with sperm quantity or quality and/or indirect benefits relating to the viability or mating probability of the progeny. Across animal taxa in general, male age has received considerable attention as a potential indicator of these fitness benefits, and the importance of male age in affecting female choice and fitness has been investigated in various insect species with highly variable results. The present study examined whether females of the Mediterranean fruit fly (medfly), Ceratitis capitata (Wied.), a lek-forming species, discriminate among potential mates on the basis of male age and whether this selectivity results in fitness benefits to the females. Both young (10 days old) and old (40 days old) females were offered males from two groups differing in age by 10, 20, or 30 days. Young females mated randomly when the age difference between the younger and older males was 10 days but mated preferentially with the younger males when the age difference was 20 or 30 days. Old females did not discriminate among males of different ages. Although young females showed mate selectivity, we found no differences in fecundity, fertility, or larval viability between young females mated to 10 versus 40 day old males.     

Experimental evidence for female choice and energetic costs of male tail elongation in red-collared widowbirds

The black nuptial plumage of the highly polygynous male red‐collared widowbird (Euplectes ardens) comprises a red carotenoid‐based collar patch and a long graduated tail (c. 22 cm). Tail length was the strongest predictor of male mating success in a previous selection analysis, motivating this experimental test of the relative importance of tail plumes in male contest competition and female choice. Males were assigned to either a short (12.5 cm) or control (20 cm) tail manipulation prior to territory establishment. Male contest competition was unaffected by the tail treatments as the shortened‐ and control‐tailed males were equally successful in acquiring territories of similar size and quality. In contrast, however, although the longer‐tailed control males spent less time in flight and courtship displays, they attracted significantly more prospecting and nearly three times as many nesting females to their territories compared to the short‐tailed males. In further support of tail length as the primary mate choice cue, none of the other measured and potential female cues (e.g. body size, collar colorimetrics, territorial behaviours or territory quality) influenced male reproductive success. In addition to potentially increasing detectability (‘signal efficacy’), the long tail is also a likely indicator of male quality (‘signal content’). Despite the higher activities of short‐tailed males, control‐tailed males showed a steeper decline in condition (relative body mass) during the breeding season. Furthermore, both short‐ and control‐tailed residents lost more condition than did the short‐ and control‐treated floaters (males not establishing territories), suggesting an interaction between tail length and the costs of territory acquisition, defence and courtship displays. These results confirm the role of mate choice and honest quality advertising as the main selection pressures behind elongated tails in widowbirds. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 86 , 35–43.     

Pre-dawn infidelity: females control extra-pair mating in superb fairy-wrens

Despite great interest in the use of extra-pair mating as a tool for examining female choice and intersexual selection, the underlying assumption of female control has proved difficult to verify empirically. We combined microsatellite genotyping and radiotelemetry of fertile females in order to investigate mate choice in superb fairy-wrens Malurus cyaneus, the bird with the highest known rate of extra-pair fertilization. All five females radio tracked during the peak of fertility, two to four days before the first egg is laid, undertook pre-dawn forays. All extra-pair young produced by the female were sired by a male visited during their forays, indicating that females control extra-pair fertilizations. In a larger sample of paternity data, some broods were sired by two extra-group males. In virtually all the cases the territory of the two sires were on an identical linear trajectory from the female's territory. This again suggests that extra-group paternity in superb fairy-wrens is directly linked to female extra-territorial forays. In other species mixed paternity has been taken to indicate that females attempt to insure against infertile pairings or try to maximize the genetic diversity of their brood. However, in fairy-wrens the likelihood of multiple extra-group paternity increased greatly as females traversed more territories in order to mate, perhaps suggesting that females which foray further are more likely to have difficulties locating the preferred male.