Environmental change mediates mate choice for an extended phenotype,but not for mate quality

Sexual cues, including extended phenotypes, are expected to be reliable indicators of male genetic quality and/or provide information on parental quality. However, the reliability of these cues may be dependent on stability of the environment, with heterogeneity affecting how selection acts on such traits. Here, we test how environmental change mediates mate choice for multiple sexual traits, including an extended phenotype–‐the structure of male‐built nests – in stickleback fish. First, we manipulated the dissolved oxygen (DO) content of water to create high or low DO environments in which male fish built nests. Then we recorded the mate choice of females encountering these males (and their nests), under either the same or reversed DO conditions. Males in high DO environments built more compact nests than those in low DO conditions and males adjusted their nest structure in response to changing conditions. Female mate choice for extended phenotype (male nests) was environmentally dependent (females chose more compact nests in high DO conditions), while female choice for male phenotype was not (females chose large, vigorous males regardless of DO level). Examining mate choice in this dynamic context suggests that females evaluate the reliability of multiple sexual cues, taking into account environmental heterogeneity.     

Female mate preference in goby Eviota prasina: do secondary sexual traits influence female choice?

Males of the small gobiid fish Eviota prasina have longer dorsal fins than females and use their dorsal fins for courtship displays and male-male competition. We examined the influence of male dorsal fin length as well as the frequency of courtship displays on female mate preference using sequential choice experiments. Females responded more frequently to courting males with longer dorsal fins than males with shorter dorsal fins. This indicates female mate preference on the basis of male dorsal fin length in this goby. In addition, the logistic regression analysis showed that male courtship frequency positively influenced female mate preference. Since males incur costs to produce and maintain longer dorsal fins and to perform frequent courtship displays, these secondary sexual traits may indicate the quality of physical characteristics. In E. prasina, only males conducted parental care for eggs in their nests. Therefore, females may be able to ensure greater survival rates as well as higher genetic quality of their offspring by choosing males with better qualities based on these male traits.     

Mate Choice and Mating Pattern in a Stream Goby of the Genus Rhinogobius

The mate choice and mating pattern of a benthic goby Rhinogobius sp. CB (cross band type) were investigated in the Kamo River, Shikoku, Japan. During the breeding season, gravid females assumed a nuptial color and either males or females initiated a courtship display. Males preferentially courted a female of similar size to lead her to his nest, whereas females courted more frequently when they encountered a large male. Eggs in any one nest were always at the same developmental stage. Sampling data of nesting males and females indicated that, in more than half the nests, males gathered more than one female before spawning. In some nests with eggs, two or three females had spent ovaries, indicating that the eggs were laid by multiple females within a short span of time. However, a comparison between the total number of eggs which females would spawn in one nest and the number of eggs actually deposited suggested that eggs were contributed by one female in most nests. This low level of polygyny in spite of multiple female availability is attributed to a limited available spawning area of the nest.     

Odour cues from suitors’ nests determine mating success in a fish

Animals use a range of sensory cues for finding food, avoiding predators and choosing mates. In this regard, the aquatic environment is particularly suitable for the use of olfactory and other chemical cues. Nevertheless, mate choice research, even on aquatic organisms, has focused on visual signals, while chemical cues relevant in sexual selection have been assumed to be ‘intrinsic’ excretions of mate candidates. Here, using the sand goby Pomatoschistus minutus, a small fish with paternal egg care, we investigated the possibility that ‘extrinsic’ chemical cues in the males’ nests could also have a significant contribution to mating success. We found that females strongly avoided laying eggs into nests subject to the odour of Saprolegnia water moulds (an egg infection) and that this effect was independent of the females’ initial, visually based preference for males. To the best of our knowledge, this is the first study to show that chemical cues related to parental failure can play a large role in sexual selection.     

The influence of oxygen stress on female choice for male nest structure in the common goby

This study examines the role of dissolved oxygen in modifying female mate choice in the common goby, Pomatoschistus microps. Experimental manipulations of nests showed that under normal (saturated) oxygen conditions, females preferred to spawn in nests with the most elaborate construction, that is, those with the most sand on top and the smallest entrance. Such manipulated nests proved less vulnerable to detection by an egg predator, the shore crab, Carcinus maenas, but these small entrances may reduce oxygenation of eggs. Indeed, in a low oxygen environment females with a choice between nests of high build and nests of low build did not significantly prefer either. This may have been due to weakened preference or perhaps detection of a mismatch between the male's parental quality and the increased ventilation needs of eggs when nest entrance sizes are small and ambient oxygen levels are low. When nests were not manipulated, those males that built small entrances fanned their eggs more often, such that hatching success in the absence of a predator was not related to the initial size of the nest entrance area. Thus, under normal oxygen conditions males may initially build nests with the smallest entrance they are capable of ventilating successfully, and females choosing such males gain from nest camouflage. Under low oxygen, the risk that manipulated males may be unable to compensate fully may outweigh such benefits, and females may use other criteria that signal willingness to provide parental care. Copyright 1999 The Association for the Study of Animal Behaviour.     

Male mating success in relation to food availability in the common goby

In a feeding experiment with the common goby Pomatoschistus microps , there was no female preference for well-fed males, although these males had a higher mating success. This suggests that care should be taken about drawing conclusions regarding mate choice and mating success based on mate preference tests alone.     

Size-assortative nest choice in the absence of competition in males of the sand goby,Pomatoschistus minutus

Synopsis Size-assortative choice of nest site is commonly found among fish with paternal care. This pattern can be explained either by the superior competitive ability of large males for preferred large nests, or by a choice of nest size that is related to the male's own body size. Choice of nest size was studied in males of a small marine fish, the sand goby Pomatoschistus minutus, by providing artificial nest sites in laboratory and field experiments. A positive correlation between nest size and male size, indicating a size-assortative nest choice process, was found in both aquarium and field experiments. This is argued to be the outcome of a preference for an optimal nest size and not to be due to competition, as (a) a surplus of nest sites was available to the individuals in nature; (b) in the aquarium experiments, single males of all sizes, when offered a choice between a smaller and a larger nest site, showed a preference for nests in proportion to their body size and not for the largest available nests; and (c) in the aquaria, when single males were offered only a small or only a large nest site, small males abstained from building nests in the large sites, whereas in the small nest sites males of all sizes built nests. My conclusion is that size assortative nest choice occurred in the absence of competition, which thus is not a necessary condition for size-assortative nesting, contrary to what is commonly assumed in many studies. This preference may represent a compromise (or trade-off) between the advantage of a nest large enough to accommodate many eggs and a smaller one with lower maintenance and defence costs.     

Male mating success and female mate choice in the river sculpin,Cottus nozawae (Cottidae)

Synopsis Mating success of males and its correlates were investigated in a natural population of the polygynous fluvial sculpinCottus nozawae. Furthermore, the female mate preference of this species was examined experimentally under alternative conditions for mating in a stream. The mating success of individual males (the number of females with which a male mated) ranged between 0 and 8 with a mean of 2.41 in 1983 and 2.52 in 1989, in a population of which the sex ratio was about 1 : 2 in both years, skewed toward females. Mainly due to the excess of nests without egg masses and the few nests with one egg mass, the distribution of male mating success did not fit a Poisson distribution, indicating its non-randomness. Male mating success was not correlated either with the size of the nest rocks or with the male size, suggesting that these two variables are not determinants of mating success. The mate choice experiments demonstrated that females of this species more frequently chose smaller males as mates whose nests already contained eggs than large males without eggs. Additionally, an analysis of stomach contents of guarding males suggested that the parental males ate their own eggs during egg guarding (filial-cannibalism). Based on these results and on a comparison of reproductive characteristics with congeneric species, it is suggested that one of the most important determinants for female mate choice inCottus species may be whether or not parental males are filial egg cannibals.     

Male and female preferences for nest characteristics under paternal care

Nests play a critical role for offspring development across the animal kingdom. Nest quality may contribute to the builder's extended phenotype and serve as an ornament during mate choice. We examined male and female nest choice in the common goby (Pomatoschistus microps), a benthic fish with male‐only parental care where females deposit eggs in male‐built nests. Using prebuilt nest models, we independently manipulated two candidate nest quality traits: (a) nest entrance width with a role in oxygen ventilation, and (b) extent of sand cover with a role in camouflage. In simultaneous choice trials, male gobies exhibited no preference for any nest model type. This suggests that initial characteristics of a nesting substrate have minor importance for males, which usually remodel the nest. Females were given a choice between two males occupying either entrance‐ or cover‐manipulated nests. The same pair of males was then exposed to a second female but now with alternated nest types assigned. Most females were consistent in choosing the same, typically the heavier male of the two regardless of nest properties. However, the females that chose the same nest regardless of the male preferred low over high sand coverage and narrow over wide nest entrance. Our results indicate that females base their mating decision on a combination of male phenotype and nest traits. While we found no indication that females are attracted to highly decorated nests, our study is the first in fishes to disentangle a preference for narrow (and thus more protective) nest entrances independent of nest coverage.     

Elaborate Nests in a Weaverbird: A Role for Female Choice?

Studies on sexual selection have focused on behaviour and morphology, but several groups of animals build elaborate structures associated with acquiring a mate. I investigated female choice for nests built by male baya weavers (Ploceus philippinus). Nest choice by females should be strong, as nests are obvious direct benefits provided by males. I used a field experiment supplemented with correlational information to ask whether females appear to base mate choice decisions on male behaviour, nest architecture, and nest location. When the nests of highly visited males were exchanged with those of poorly visited males, female visits remained highest at the original male and location. I found no relationship between female choice and male display or other behaviour. Correlational analyses show that nest location was a better predictor of female choice than was nest architecture. These data suggest that current female choice is driven more by access to safe nesting sites rather than to well‐built nests, possibly because all males are able to build nests of adequate quality. However, nest architecture is unlikely to be irrelevant to females, and its role deserves further investigation.     

Effect of clutch size on male egg-fanning behavior and hatching success in the goby, Eviota prasina (Klunzinger)

In fish that exhibit paternal care, the females often choose their mates on the basis of male traits that are indicative of the parental ability of the males. In a marine goby, Eviota prasina, males tend their eggs within their nests until hatching, and females prefer males that have longer dorsal fins and exhibit courtship behavior with a higher frequency as their mates. In order to clarify the relationship between these sexually selected traits and the parental ability of males of E. prasina, the factors affecting the hatching success of eggs within male nests and the male parental care behavior were examined in an aquarium experiment. Females spawned their eggs in male nests and the clutch size of females showed a high individual variation (range = 88-833 eggs). The hatching success of eggs within male nests showed a positive correlation with the time spent by males in fanning eggs and the clutch size. In contrast to the prediction, however, the hatching success did not show a significant correlation with the sexually selected traits, i.e., the male dorsal fin length and the frequency of courtship displays. Moreover, multiple regression analysis indicated that the time spent by the males in fanning was the most important factor affecting the survival rate of the eggs. The time spent by males in fanning behavior was influenced by the clutch size within their nests; the fanning behavior of males occurred with a higher frequency when they tended larger clutches. Males are required to invest a greater effort in egg-tending behavior to achieve a higher hatching success when they receive larger clutches, probably due to the greater reward for their parental behavior. Based on their mate choice, females may obtain other benefits such as high quality offspring.     

Effects of resource holding potential and resource value on tenure at nest sites in sand gobies

Over a broad range of animal systems, male reproductive successdepends on resource holding potential (RHP) and resource quality.In a field study, we randomly combined males of different sizeswith nests of different sizes to investigate the relative roleof resource holding potential and resource quality in determininga sand goby, Pomatoschistus minutus, male's nest tenure. Individuallymarked small and large males were given either small or largeflowerpots for nests in isolation and were exposed to intrudersafter they had built nests. We found that nest tenure was longerfor big males and owners of big nests. In most cases (34 of51) the original nest owner was replaced by a bigger male. Thesereplacements by larger males were probably due to takeoversby stronger intruders. Replacement males were larger at bignests. Our results support resource defense theory, as individualswith higher RHP and more valuable resources defended their nestfor longer. On nine occasions males abandoned their nests. Ownersof these nests were larger than the nest owners that were replaced.Hence, our results may provide an example of a situation inwhich sand goby males are able to judge the reproductive valueof their current situation and act accordingly.     

Have your cake and eat it too: male sand gobies show more parental care in the presence of female partners

Traditionally, male parental effort and mate attraction effortare expected to be in conflict as they compete for the sameresource budget. However, the quality of care provided by themale may be of a direct benefit to females and may provide animportant mate choice cue. In a laboratory experiment, we examinedhow males modified their parental behavior with respect to matingopportunity by allowing male sand gobies to mate with a singlefemale either in a big or small nest (a constraint on futuremating potential). We then exposed half of these males to thevisual stimulus from additional females and recorded male eggfanning and nest building (two components of care), courtshipbehavior, and reproductive success through out the brood cycle.We found that males fanned longer and more frequently and didmore nest construction in the presence of females and in bignests. Males guarding large nests courted females more thandid males guarding small nests. All males consumed eggs duringthe brood cycle, but complete clutch cannibalism was most frequentwhen males were guarding small nests in the absence of females.The pattern of filial cannibalism that we observed suggeststhat males prematurely terminated care when their reproductivepotential was low, that is, when there was little nest spacefor additional mating and no mates present. We found no supportfor a trade-off between mate attraction and parental care. Indeed,taken together our results suggest that males may use parentalcare as a courtship strategy and that males who invest in mateattraction also have higher parental effort.     

Breeding pattern and nest guarding in Sicyopterus lagocephalus, a widespread amphidromous Gobiidae

Amphidromous gobies are usually nest spawners. Females lay a large number of small eggs under stones or onto plant stems, leaves or roots while males take care of the clutch until hatching. This study investigates the breeding pattern and paternal investment of Sicyopterus lagocephalus in a stream on Reunion Island. In February 2007 and January 2010, a total of 170 nests were found and the presence of a goby was recorded at 61 of them. The number of eggs in the nests ranged from 5,424 to 112,000 with an average number of 28,629. We showed that males accepted a single female spawning in the nest and cared for the eggs until hatching. The probability for a nest to be guarded increased with the number of eggs within it, suggesting that paternal investment depends on a trade-off between the reproductive value of the current reproduction and future nesting events. We showed that large nest stones were occupied by large males (TL >80 mm), whereas smaller males (TL <50 mm) were found under smaller cobbles, probably because of male–male competition for available nests. Our results suggest that the male’s choice relies upon a similarity to the female size, while the female’s choice was based on both body and nest stone sizes.     

Male behaviour and female choice: Mate selection in the wren?

The European wren is frequently polygynous. Males occupy exclusive territories within which they spend much time displaying and building nests. They lead females to their nests in courtship. Males building the most nests during a season also make the most breeding attempts. Data collected in one of two years suggested that individual females may show a preference for males with the largest number of complete but vacant nests. There was no consistent correlation between male display behaviour and female mate choice. Data on breeding success may suggest why polygyny is adaptive for both males and females in this species.     

Female sand gobies prefer good fathers over dominant males

Female preference for males successful in male-male competition is generally assumed to result in mating with high quality males. Here I report results from an experiment disentangling the effects of intra- and intersexual selection in the sand goby, Pomatoschistus minutus, a marine fish that exhibits paternal care. I show that large males are successful in male–male competition, but contrary to what one would expect, dominants are not preferred by females and are not better at taking care of the eggs. Female preference, however, correlated with the subsequent hatching success of the eggs. Thus, female choice selects for good parenting. Hence, direct benefits in the form of superior paternal care can explain female choice in this species, supporting a good parent process of sexual selection. However, choosing on the outcome of male–male competition does not enable females to mate with the ''best'' males.     

Male–male competition for large nests as a determinant of male mating success in a Japanese stream goby, Rhinogobius sp. DA

Males of the stream goby Rhinogobius sp. DA (dark type) court females in deep pools and care for the eggs under stones in shallow riffles. We studied male–male competition for access to females and nest sites to understand how male size influences the mating success of this species. In field observations, larger males won in fighting with other males. However, large males did not tend to monopolize courtship opportunities, and the frequency of successful courtships, after which males led the females to the nests, was not related to male body size. The fact that courted females always escaped from the fighting sites once males began fighting likely explains why male size was not positively related to courtship success. Large males occupied large nest stones, and the number of eggs received in the nest was correlated positively with nest size. In aquarium experiments with two tiles of different sizes provided as nesting materials, males always chose the larger nest and, when two males were introduced simultaneously, the larger one occupied the larger nest. These results suggested that male mating success of this goby is determined by male–male competition for large nests rather than for access to females. Received: June 9, 2000 / Revised: September 2, 2000 / Accepted: October 4, 2000     

Big is better: the importance of size for reproductive success in male Pomatoschistus minutus (Pallas) (Pisces, Gobiidae)

The sand goby, Pomatoschistus minutus , was used in aquarium experiments to study the importance of body size for the ability of males to gain access to nest sites and mates. When several male and female P. minutus were allowed to reproduce together, on average, half of the males built nests, and half of those males obtained eggs in their nests. Males with nests were significantly larger than males without nests, and nests with eggs belonged to males larger than the males with empty nests. In another experiment, when two males were competing for one nest, the largest male occupied the nest when both fish were put into the aquarium simultaneously. However, when the smaller male had been allowed to establish a nest before the larger male was introduced, the small male could usually retain the nest. Males with a body length < 50 mm did not build nests at all in the early part of the breeding season. In female choice experiments, no preference for larger males was found. Thus, male-male competition for nest sites and behavioural differences between different sized males seem to be the main factors influencing the non-random mating success in male P. minutus.     

Mate competition and resource competition are inter‐related in sexual selection

Sexual selection can be affected by the competition for limited breeding resources and/or the competition for limited mates. Although there is ample evidence for each type of competition by itself, little is known about their relative importance and interaction. To address these questions, we established 48 experimental breeding populations of the two‐spotted goby (Gobiusculus flavescens), a substrate‐breeding fish with paternal care. In three experimental treatments, males were limited in the access to either nest sites or mates or were provided with both nests and mates in excess. We quantified male competition behaviour (agonistic and courtship), the opportunity for selection and selection on male body size. Limited access to nests and mates produced similar opportunities for selection, but only limited access to mates increased male competitive behaviours and caused positive selection on male body size. Selection on body size in the mate‐limited treatment was due both to larger males being more likely to take up nests and to larger males being more likely to mate once they had a nest. These findings demonstrate that resource and mate limitation can differ in their effects on sexual selection. The results also reveal that resource and mating competition can be highly inter‐related and not always separated in time, implying that methods to disentangle the two processes must be chosen with care. Future research should consider experimental and analytical approaches similar to those of the present study in attempts to elucidate the interaction of resource and mating competition in animals.     

Does competition for nests affect genetic monogamy in Cory's shearwater Calonectris diomedea?

Most bird species are socially monogamous. However, extra‐pair copulations (EPCs), resulting in extra‐pair paternity (EPP), commonly occur. EPCs should allow females to adjust social mate choice and allow males that fail to obtain a nest a chance to avoid missing a breeding season, especially when poor nest supply constrains social mate choice. Procellariiformes (albatrosses and petrels) are socially monogamous seabirds which seldom divorce, even when nest availability constrains social mate choice. In Cory's shearwater Calonectris diomedea, a burrow‐nesting petrel, two studies conducted in the Mediterranean, where competition for nests is weak, detected no EPP. EPP remains to be investigated at localities where competition for nests is much stronger, such as Vila islet, Azores archipelago, Atlantic Ocean. We conducted a genetic (microsatellites) study over two successive years on Vila, involving the breeding pairs of the same 65 nests each year and their single chick. EPPs occurred each year, the overall rate being 11.6%. Coupling genetic analyses to a 7‐year demographic survey provided additional data on pair bonds and competition for nests. Overall, cuckoldry was unrelated to divorce, nest density and inbreeding avoidance, but was more frequent when the social male was small. Nest changes were more costly for males than for females, and some apparently unpaired males attempted to dislodge social males during within‐pair copulations. These results are compatible with the existence of a link between poor nest availability and EPP and confirm that even species considered strongly monogamous can adopt flexible mating strategies.