Social factors of group spawning as an alternative mating tactic in the territorial males of the threespot wrasse <Emphasis Type="BoldItalic">Halichoeres trimaculatus</Emphasis>

In most labrid fishes, large males with bright terminal phase (TP) coloration normally defend mating territories and pair spawn after following (i.e., courting) solitary females. It has also been reported that the TP males may abandon their territories and participate in group spawning when mating groups of small non-territorial males with drab initial phase (IP) coloration frequently intrude into the territories of TP males. In the similar situation of the present study, however, the territorial TP males of the threespot wrasse, Halichoeres trimaculatus, did not always participate in group spawning but continued pair spawning. Only the TP males that had few opportunities to encounter solitary IP individuals participated in group spawning, frequently following the mating groups of IP individuals. It is therefore suggested that group spawning of the territorial TP males is regarded as a tactic of making the best of the bad situation by the TP males with few opportunities to pair spawn in an area where group spawning dominates.     

Interspecific variation in spawning time and male mating tactics of the parrotfishes on a fringing coral reef at Iriomote Island,Okinawa

Spawning time and male mating tactics of parrotfishes (family Scaridae) were investigated on a fringing coral reef at Iriomote Island, Okinawa. Spawning was observed in 14 species, and more frequently in more abundant species such as Chlorurus sordidus, Scarus rivulatus and Chlorurus bowersi. At the reef-edge spawning site, C. bowersi spawned at high tide, C. sordidus spawned both at high tide and in the early morning, whereas Calotomus carolinus and most of the Scarus species such as S. rivulatus spawned only in the early morning, mostly 0630–0830 h. Spawning only in the early morning irrespective of tide phase and moon age has seldom been reported from the scarid species of other localities. It is suggested that spawning in the early morning would be adaptive in species such as S. rivulatus, which migrated considerable distances (ca. 500 m) to the inshore feeding sites, in order to minimize feeding losses due to migration. For male mating tactics, pair spawning by territorial TP (terminal phase) males occurred in all 14 species, and streaking and group spawning by nonterritorial small IP (initial phase) males were seen more frequently in more abundant species. Moreover, group spawning by nonterritorial TP males, which were larger than the IP males but smaller than the territorial TP males, frequently occurred in S. rivulatus. Such mating tactics of TP males have not been reported from Scaridae.     

Group spawning results from the streaking of small males into a sneaking pair: male alternative reproductive tactics in the threespot wrasse Halichoeres trimaculatus

In many protogynous wrasses, large males with bright coloration (terminal phase males, TP males) establish mating territories and pair-spawn with females. In contrast, small primary males with drab coloration (initial phase males, IP males) are non-territorial and adopt three alternative reproductive tactics—group spawning, streaking, and sneaking. We investigated how IP males of the threespot wrasse Halichoeres trimaculatus use these tactics in different situations. The mating frequency of the IP males was positively correlated with their courtship frequency, but not with their body size. Larger IP males tended to attack the smaller ones at the mating sites. This indicates that the larger IP males attempted to exclude the smaller ones from mating with the intention of minimizing the number of IP males involved in group spawning and ultimately leading to pair spawning (sneaking). However, the larger IP males were unable to completely exclude the smaller males because the intensity of the attack by the larger IP males was weak. Consequently, the smaller IP males could easily streak into the sneaking of larger IP males, thereby resulting in group spawning.     

Male House Finches with Elaborate Songs have Higher Reproductive Performance

The elaborate songs of male animals are thought to function in either territory defense (male–male communication) or mate attraction (male–female communication). In non‐territorial animals, male vocalizations are expected to function primarily in mate attraction, yet the reproductive consequences of male vocalizations in non‐territorial animals are poorly described. Here we explore the relationship between male song and male reproductive performance in a free‐living population of house finches, Carpodacus mexicanus, a non‐migratory, non‐territorial songbird. Based on recordings of 20 males, we analyzed three song features (song length, number of unique syllables per song, and song rate) and compared male song with two measures of within‐pair reproductive performance (nest initiation date and clutch size) and one measure of extra‐pair reproductive performance (whether males sired extra‐pair young). We demonstrate a positive association between male song and within‐pair reproductive performance; males that sang long songs initiated their first clutch significantly earlier and males that sang songs at a faster rate had larger clutches. Despite the fact that only one of our recorded males sired extra‐pair young in the nest of another male, this male's songs were the most elaborate for two of three song features measured, anecdotally suggesting that male song may play a role in both within‐pair and extra‐pair partner choice. These results suggest that male song is a sexually selected trait in non‐territorial house finches.     

Reproductive Success Associated with Territoriality, Sneaking, and Grouping in Male Rose Bitterlings, Rhodeus ocellatus (Pisces: Cyprinidae)

The spawning success of male rose bitterlings, Rhodeus ocellatus, adopting an alternative reproductive style, was estimated through behavioural data and electrophoretic paternal analyses in field observations and experiments. Three mating patterns were observed: territoriality, sneaking, and grouping. Mating patterns depended on a male's relative size and on local male density (the number of males around a spawning spot: a mussel). Spawning patterns (pair spawning, pair spawning with sneaker, and group spawning) varied with local male density. Time-budget data of the territorial males indicated a trade-off between chasing and courtship behaviour as local male density changed. Females deposited appoximately only 1 egg per egg-laying into the mussels. As a result of isozyme analysis, a minimum of 12% (two out of 17) of the offspring in the sample were found to have been fathered by sneaker males in pair spawning with sneaker. I scored through behavioural data the mating success per spawning for each pattern, on an individual basis. The average reproductive success per spawning for each pattern was: territorial (0.61), sneaking (0.31) and grouping (0.11), and thus the successes of the patterns were not equal. Accordingly, the alternative reproductive styles of male rose bitterlings are best interpreted as alternative phenotypes in a conditional behaviour.     

Pre-oviposition Ejaculation in Externally Fertilizing Fish: How Sneaker Male Rose Bitterlings Contrive to Mate

Pre-oviposition ejaculation as a mating tactic of sneaker males in the rose bitterling, Rhodeus ocellatus, was studied under natural and artificial conditions. In a small pond in Yao city, Osaka, Japan, the operational sex ratio of males and females was found to be approximately 3.5:1 and the proportion of males to the mussels, which serve as spawning beds for the rose bitterling, was approximately 2:1. Competitively subordinate rose bitterling males which spawned into the mussels participated in mating by sneaking, because not all males could occupy territories around the mussels. The sneaker males often released sperm not only after but also before egg-laying (this ejaculation movement by the male before egg-laying is termed ‘pre-oviposition ejaculation’). In pair spawning with sneaker, the sneakers frequently performed pre-oviposition ejaculations, which territorial males never performed. In the field, pre-oviposition ejaculations by sneakers coincided with the leading of females by territorial males. Under artificial conditions, I demonstrated by using electrophoretic paternal analyses that the pre-oviposition ejaculations by the sneakers were more effective than the post-oviposition ejaculations by the territorial males. In addition, there were negative size-dependences in ejaculation achievement rate and fertilization success of the sneaker 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.     

Description of alternative male reproductive tactics in a shell-brooding cichlid, Telmatochromis vittatus, in Lake Tanganyika

Telmatochromis vittatus (Cichlidae) is a Tanganyikan substrate brooder which spawns in the gastropod-shell nests of a cichlid, Lamprologus callipterus. We describe male reproductive tactics of T. vittatus in and around the shell nests, where males of various sizes were found. Based on utilization patterns of the shell nests, interactions among males, and spawning behaviors, males could be categorized into four types based on reproductive tactics and in order of body size: sneaker males, satellite males, territorial males and piracy males. Size range of males in tactic groups rarely overlapped. Territorial males defended shell nests harboring multiple females, but during pair-spawning they were occasionally taken over by large piracy males that visited several nests repeatedly. Small sneaker males darted to pair-spawning territorial males and might ejaculate sperm. Satellite males did not perform parasitic spawning but pair-spawned in a single shell outside the nests. Spawning of satellite males was infrequently parasitized. The largest gonado-somatic index (GSI) was found in sneaker males followed by piracy males, territorial males and satellite males, suggesting that gonadal investment of males using the four tactics may be consistent with intensity or risk of sperm competition.     

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.     

Spatial Dispersion and Nonmigratory Spawning in the Bluehead Wrasse (Thalassoma bifasciatum)

Earlier studies of the behavior of the bluehead wrasse Thalassoma bifasciatum have shown it to be a migratory spawner with large terminal-phase males defending temporary spawning territories. We describe a variant social structure where fish occupy permanent home ranges, spawn within or near these home ranges, and are not territorial. Movements of identified terminal-phase and intermediate males and females were mapped in the backreef areas of three coral reefs in Puerto Rico. Locations of spawns were then compared with these home-range maps. All fish used most or all of their morning home range during the afternoon spawning period. Both terminal-phase males and females spawned within or near their home ranges. Males were relatively tolerant of other males during the afternoon spawning period: only one in five encounters between large males resulted in aggressive chases. The location of chases bore no relation to spawning sites, areas of morning foraging, or to home-range borders. A Monte Carlo computer simulation was used to measure home-range dispersion of terminal-phase and intermediate males at our main site. If males were territorial, we should expect their home ranges to be significantly overdispersed within the cumulative area they occupied. During the first year male home ranges were overdispersed but during the second year they were randomly dispersed, even though the same number of terminal-phase males occupied the same study site both years. Differences in social behavior between backreef areas and other areas reported in the literature, and found in other portions of our reefs, may be related to differences in feeding ecology between populations and between different portions of the same reef.     

Local variability in population structure and density of the protogynous reef herbivoreSparisoma viride

Synopsis We compare the (relative) abundance of life phases [juveniles (JU), initial phase (IP) and terminal phase (TP) fish], social categories (territorial and group adults), and fish following alternative mating styles, in three local populations of the protogynous reef herbivore,Sparisoma viride, on the fringing reef of Bonaire (Netherlands Antilles). In order to determine the adaptive significance of variations in social organization, they are related to the density of conspecifics and other herbivores and to the availability of food, shelter and mating sites. The most striking difference is the high abundance of JU and group fish at one location (Playa Frans) and the total absence of group fish at another (Red Slave). These differences are coherent with a gradient in population density, total herbivore density, scarid grazing pressure, and reproductive output, all of which are highest at Playa Frans and lowest at Red Slave. Exposure to waves and currents shows an inverse trend. The differences in the relative abundance of territorial fish can be explained by the concept of economic defendability, which is reduced at higher population density. In a life history context, small TP group males represent bachelors that sacrifice current reproduction for better future prospects. As predicted by life history theory, early sex change is promoted at sites where the future rewards are higher (higher spawning rates of large TP males) and where the costs incurred during the bachelor phase are reduced (more spawning opportunities for group TP males). At Red Slave an alternative male mating style (streaking) appears to be promoted by the lack of a refuge for group TP males and by a dense gorgonian canopy, allowing IP males to reside inside territories. We conclude that most observed differences in population structure can be considered adaptive in an ecological and in a life history context. Population density is a major factor in both contexts. Analysis of the variability in adult density in relation to JU density and the availability of food and shelter indicates that theS. viride populations at Bonaire are not totally controlled by stochastic processes. Considering the small spatial scale and the high dispersal of the planktonic embryos and larvae, the observed variability in behavioural and life history traits ofS. viride points to a high degree of phenotypic plasticity.     

Testosterone Manipulation of Male Attractiveness has no Detectable Effect on Female Home-Range Size and Behavior During the Fertile Period

Female dark‐eyed juncos (Junco hyemalis) are socially monogamous, but they engage in extra‐pair copulations (EPCs). We examined spatial activity and behavior of female juncos during their fertile period to determine whether they engaged in tactics likely to facilitate EPCs and whether any such tactics varied with the attractiveness of their social mates. We manipulated the attractiveness of social mates by implanting experimental males with tubes containing testosterone (T‐males) and control males with empty tubes (C‐males). Previous findings in free‐living juncos showed that females mated to C‐males were more likely to produce extra‐pair young than females mated to T‐males. We radio‐tracked 13 females (eight C‐mated, five T‐mated) for an average of 15 h each over 3 d during their fertile periods. We predicted that C‐mated females, to compensate for the induced relative unattractiveness of their social mates, would foray from their territories to seek EPCs and as a result would have larger home ranges than T‐mated females. Females of both treatment groups made extra‐territorial forays, some of considerable distances, but we observed no EPCs during forays. Further, neighboring T‐ and C‐males frequently made incursions into the home ranges of T‐ and C‐mated females but we saw no EPCs during these incursions. Our ability to detect statistical differences was limited by sample size, but given that constraint, we found no detectable difference in female home‐range size in relation to the treatment of their mates, nor did other female behavior differ according to male treatment. Male behavior was significantly affected by testosterone treatment. C‐males guarded their mates more closely than did T‐males. We conclude that female juncos make extra‐territorial movements during their fertile period without regard to male attractiveness (testosterone treatment), but we found no evidence that these function as a special tactic to gain EPCs.     

Mate Choice and Spawning Success in the Fighting Fish Betta splendens: the Importance of Body Size, Display Behavior and Nest Size

Courtship displays should be exaggerated enough to attract mates and yet tempered so as not to deter them. We tested this hypothesis in the fighting fish Betta splendens by studying courtship displays and body size and their relationships with male parental quality and female fecundity, as well as the effects of display behavior and body size on mate choice decisions and spawning success. Because of their high degree of parental investment, males are expected to be discriminating in their choice of mates. Males who displayed more frequently built larger nests, a measure of parental quality, but larger males did not. When females were paired with males with high display rates, however, the pair had fewer eggs in their nest, even when accounting for female body mass. In a mate choice test using computer‐generated male stimuli that differed only in display behavior, females showed no preferences for displaying males vs. non‐displaying males, or for males with higher display rates vs. lower display rates. In similar tests in which the computer‐generated males differed only in size, females preferred larger males, but also preferred males that differed with respect to body size (negative assortative mating). Males preferred computer‐generated females that performed courtship displays over non‐displaying females, but showed no preferences for female body size. Neither a female's body size nor her display behavior was a significant predictor of her fecundity as estimated by the number of eggs released during spawning. Thus, our results suggest that female B. splendens must balance male parental quality (nest size) with the risk of potentially disruptive or dangerous behavior during spawning, and that females may minimize these risks through negative size‐assortative mating. Female display behavior, while unrelated to fecundity in our study, may attract males because it indicates reproductive readiness or serves a species‐recognition function.     

Comprehensive paternity assignment: genotype,spatial location and social status in song sparrows,Melospiza Melodia

Comprehensive, accurate paternity assignment is critical to answering numerous questions in evolutionary ecology. Yet, most studies of species with extra‐pair paternity (EPP) fail to assign sires to all offspring. Common limitations include incomplete and biased sampling of offspring and males, particularly with respect to male location and social status, potentially biasing estimated patterns of paternity. Studies that achieve comprehensive sampling and paternity assignment are therefore required. Accordingly, we genotyped virtually all males and >99% of 6‐day‐old offspring over 16 years in a song sparrow (Melospiza melodia) population and used three complementary statistical methodologies to attempt complete paternity assignment for all 2207 offspring. Assignments were highly consistent across maximum likelihood methods that used solely genotype data, and heuristic and integrated Bayesian analyses that included data describing individual locations. Sires were assigned to >99% of all genotyped offspring with ≥95% confidence, revealing an EPP rate of c. 28%. Extra‐pair sires primarily occupied territories neighbouring their extra‐pair offspring; spatial location was therefore highly informative for paternity assignment. EPP was biased towards paired territorial males, although unpaired territorial and floater males sired c. 13% of extra‐pair offspring. Failing to sample and include unpaired males as candidate sires would therefore substantially reduce assignment rates. These analyses demonstrate the integration of genetic and ecological information to achieve comprehensive paternity assignment and direct biological insight, illustrate the potential biases that common forms of incomplete sampling could have on estimated patterns of EPP, and provide an essential basis for understanding the evolutionary causes and consequences of EPP.     

Responses of territorial and floater male Red‐winged Blackbirds to models of receptive females

Red‐winged Blackbirds (RWBL; Agelaius phoeniceus) have a polygynous mating system and, because territorial males commonly have harems of two to five females, some second‐year (SY) and after‐second‐year (ASY) males do not establish nesting territories, but become floaters. Previous studies have revealed high rates of extra‐pair copulations in this species and that sexually mature male floaters and territory owners do not differ in size, testosterone levels, or reproductive capability, suggesting that floaters may occasionally gain paternity. During May and June 2008, we observed the behavioral responses of floater males to taxidermic mounts (models) of female RWBL placed in a precopulatory position. Floaters intruded into territories during 46% of model presentations, with 20% of intrusions by ASY floaters and 80% by SY floaters. During intrusions, ASY floaters attempted to copulate with models 93% of the time compared to 80% for SY floaters. Copulations were successful during 30% of attempts by ASY males and 25% of attempts by SY floaters. The frequency of intrusions by ASY and SY floaters, attempted copulations by SY floaters, and successful copulations by ASY floaters increased as territorial males spent more time off their territories. Responses of floater males toward models in our study suggest that floater male RWBL attempt to exploit available breeding opportunities. The lack of evidence for extrapair young (EPY) fathered by floater male RWBL in previous studies, combined with our results indicating that the presence of territorial males limits floater intrusions, copulation attempts, and successful copulations, suggests that the reproductive success of floater males is limited in part by the aggressive behavior of territorial males.     

Growth and longevity of the protogynous parrotfish,Hipposcarus harid,Scarus ferrugineus and Chlorurus sordidus (Teleostei,Scaridae), off the eastern coast of the Red Sea

Growth and longevity were studied for three species of the family scaridae, the longnose parrotfish (Hipposcarus harid), rusty parrotfish (Scarus ferrugineus) and bullethead parrotfish (Chlorurus sordidus), sampled at the eastern coast of the Red Sea, off Saudi Arabia. The three species are protogynous hermaphrodites presenting two distinct phases whereby the initial phase includes females and primary males, and the terminal phase is exclusively secondary males transformed from females. Annual marks in the ctenoid scales from the three species were used to develop size‐at‐age plots. Linear relationships were found between the scale radius and standard length for the three species, and the relationships between body weight (w) and standard length (L) were estimated. Scales of these species increased in size consistently throughout life, even though the somatic growth rate decreased with age. Sex‐specific growth effects in the three species were demonstrated. Growth of initial phase females was the lowest, followed by the initial phase males and terminal phase males, the latter showing the fastest growth rates. Thus, transition to the terminal male identity was associated with enhanced growth, resulting in larger terminal males than females of equivalent size. The von Bertalanffy growth formula (VBGF) was estimated for H. harid, S. ferrugineus and C. sordidus (L_∞ = 43.92, 27.4 and 23.3; K = 0.067, 0.27 and 0.56; t₀ = ?6.92, ?4.98 and ?4.6, respectively). The relationship between growth and reproduction of these species is also discussed.     

Seasonal variation in male testosterone levels in a tropical bird with year‐round territoriality

Testosterone is important in mediating investment in competing activities such as territoriality, parental care, and maintenance behavior. Most studies of testosterone function have focused on temperate species and less is known about the role of testosterone in territoriality or variation in mating systems of tropical species. Results of studies of tropical species with year‐round territoriality indicate that territorial aggression during the non‐breeding season is maintained with low levels of testosterone, and increased levels of testosterone in males during the breeding season may increase mating opportunities or aid in competition for mates. We studied seasonal variation in testosterone levels of male Red‐throated Ant‐tanagers (Habia fuscicauda), a socially monogamous species with year‐round territoriality and with high levels of extra‐pair matings (41% of young), to determine if testosterone levels increased during the breeding season. We captured males during the non‐breeding and breeding seasons and collected blood samples for hormone analysis. We found that mean testosterone concentrations were low during the non‐breeding season (0.18 ± 0.05 [SD] ng/ml, range = 0.11–0.31 ng/ml), and significantly higher during the breeding season (2.37 ± 2.47 ng/ml, range = 0.14–6.28 ng/ml). Testosterone levels of breeding males were not related to aggression levels as measured by attack rates toward a stuffed decoy or singing rates during simulated territorial intrusions. These results suggest that the higher testosterone levels of breeding male Red‐throated Ant‐tanagers may be important in an extra‐pair mating context, possibly in display behavior or mate attraction, but additional study is needed to clarify the role of testosterone during the breeding season.     

Mating patterns of female Leon Springs pupfish Cyprinodon bovinus

In a field study of Leon Springs pupfish Cyprinodon bovinus, two questions about female promiscuity were investigated. First, were females selective in the males with whom they spawned or were they unselective, spawning randomly among males? Second, how promiscuous were the females, i.e. with how many males did they spawn? If simply spawning with many males maximized a female's reproductive success, then females might be expected to spawn randomly with as many males as possible. Alternatively, if females were selective but engaged in multiple mating, they would limit their spawning to preferred males. In the only wild population of this endangered fish, breeding males defend closely associated territories in the shallow margins of a single desert pool. No territories were observed elsewhere in the pool. Therefore, all territorial males were present simultaneously and females could survey all of them, depositing any number of eggs with one, a few or many males. Rather than spawning randomly, females surveyed many males first, visited relatively few males and ultimately spawned with a small fraction of those available males. With increasing numbers of spawns, however, females increased the number of different mates with whom they spawned. Thus, females showed a bet‐hedging tactic of having a narrow mate preference while also laying eggs in the territories of other males, possibly to reduce egg predation and to avoid inbreeding.     

A novel sexual pattern in serranid fishes: simultaneous hermaphrodites and secondary males in Serranus fasciatus

Synopsis Gulf of California populations of Serranus fasciatus are composed of functional simultaneous hermaphrodites and males. This is the first serranid known to have this sexual pattern which is functionally intermediate between the typical serranid patterns of simultaneous and protogynous hermaphroditism. Males of S. fasciatus are derived from hermaphrodites by resorption of ovarian tissue and proliferation of the extant testicular band. Distinct sexual roles are evident in spawning events. Hermaphrodites gain female function by pair spawning with males (124 and 125 observed spawns) and rarely with other hermaphrodites (1 of 125). Hermaphrodites gain male function by sneak spawning (9 of 125) and rarely by pair spawning with other hermaphrodites. Males exclusively pair spawned with hermaphrodites. Despite its unusual sexual pattern, S. fasciatus appears allied with other Serranus species based on similarities in gonad morphology.