Body Condition in Male Betta splendens Does Not Predict Their Ability to Perform Opercular Displays Under Hypoxic Conditions

Many fish, including the fighting fish Betta splendens , perform a display in which the opercula are extended away from the head and gills. Previous work has shown that opercular display rates by male B. splendens decrease under conditions of reduced dissolved oxygen (hypoxia). We tested the hypothesis that the ability to maintain opercular display rates under hypoxic conditions is related to body condition in male B. splendens . We also tested the hypothesis that females would show a greater preference for males performing this display under hypoxic conditions, when the display should be a more reliable indicator of male phenotypic quality. We found no evidence to support either hypothesis. Male opercular display rate in hypoxic conditions was unrelated to natural or experimentally induced variation in body condition. Female B. splendens showed no differential preference for the opercular display, assessed through the use of computer animated male stimuli, in either acute or chronic hypoxia. We conclude that the presence of an air-breathing organ in this species makes the opercular display an unreliable signal of male quality as measured by body condition.     

Song discrimination learning in zebra finches

Young male and female zebra finches, Taeniopygia guttata, were tested for their ability to discriminate between the song of their father or tutor and that of another male in two types of preference test, one with a male whose song was dissimilar to that of the father or tutor and one with a male who sang a similar song, on removal from the father, at 4 months and at 6 months of age. Birds that were isolated from their father at 25 days (group A) did not show a preference for their father's song whereas those isolated from the father at 35 days (groups B and C) learnt to prefer their father's song. In addition, group C, which were housed with tutor 1 from 35 to 70 days and with tutor 2 from 4 to 6 months of age, preferred their tutors' songs to those of other males. If one compares the strength of preference in the two types of test, group B showed a weaker preference for the father in tests with the father and a similar male. Further, group C showed a weaker preference in the test with tutor 1 versus a similar male. The possible influence of tutor, sibling and own song on the discrimination of the father's song is discussed, and the results are compared with those for song performance learning. Finally, the mother birds preferred their mate's song.     

Anwenden erlernter Fähigkeiten während einer Begegnung mit einem Partner

Rats had learnt special abilities in a test chamber. The next step was to test whether these special abilities would have any influence on social interactions in a test chamber. The behavior of male BDE-rats was tested in three different situations. 1. Rat A was able to handle a central lever to get food (ability f) and rat B had learnt to press a lever in front of the test chamber to get water (ability w). 2. Rat A had learnt both abilities (f and w) and rat B had learnt neither. 3. Both animals had learnt the abilities f and w. Subsequently it might be possible that in some special test-situations one of the animals will learn from the other. In control series, therefore, other rats had to learn the ability f or w, or f and w without the presence of another rat. The results suggested that the behavior of the rats was influenced by the learnt ability. Another result was that there is no connection between the learnt ability of an animal and its social rank. The learning results of the rats which learnt alone in the test chamber (control group) were better than the results of the subjects which had the chance to learn in the presence of a partner.     

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.     

Mating preference of female zebrafish, Danio rerio, in relation to male dominance

Mating success tends to be skewed toward dominant males, thoughfemale mate preferences may not always correlate with male dominance.In this study, we investigated the mating preferences of femalezebrafish, Danio rerio, in the absence of male–male competition.We paired females sequentially with males of known dominancerank, using a nested, repeated measures design, with egg productionas a measure of female mate preference. We predicted that femaleswould spawn more frequently and produce larger clutches whenpaired with males of higher dominance rank. We found significantdifferences among females in the size of clutches produced andamong males in the size of clutches received, but these differenceswere independent of male dominance rank. Male body size wasnot related to either dominance rank or clutch size received.These results indicate that females vary clutch size in relationto the males with which they are paired but that they do notfavor dominant males. Thus, male competition may normally overridefemale mate preference in zebrafish.     

Does leg-ring colour affect song tutor choice in zebra finches?

Young male zebra finches, Taeniopygia guttata, reared by their mothers alone showed no preference between males with red and with light-green colour rings in their choice of song tutor. Behavioural observations showed that the tutee associated more with the adult from which it was subsequently found to have learnt. In a second experiment, birds reared by both parents wearing either light-blue or light-green colour rings and then given a choice of tutors wearing these ring combinations also showed no preference between them. These young males did, however, more often approach the tutor ringed as their parents had been. This may explain why they did not show more interest in the tutor whose song they learnt. The majority of the tutors were used twice, with the ring colour swapped before they were used the second time. There was a strong tendency for the same male to be copied by the two young birds exposed to him. This could not be attributed to a difference in song rate between the two tutors. Further work will be required to discover the basis of that individual's greater attractiveness. Copyright 1999 The Association for the Study of Animal Behaviour.     

Variation between and within the sexes in body size preferences

Although it is often assumed that males and females have mating preferences for larger individuals of the other sex, potential underlying differences between male and female preferences for body size are not commonly investigated. Here, sexual differences in body size preferences are examined in the poeciliid fish, Brachyrhaphis rhabdophora. Females preferred larger males to smaller males, but preference did not appear to be affected by female size. One population-level analysis for males did not indicate an overall preference for larger females. A closer examination, however, revealed an effect of male size on preference; larger males preferred larger females, while smaller males preferred smaller females. It appears then that females, regardless of size, share a preference for large males, but males differ in their behaviour, depending on their body size. In addition, while the degree of difference in size between paired females did not appear to affect male preference, the degree of difference in size between paired males strongly affected female preference; the greater the difference, the more strongly females preferred the larger male. Thus, intersexual selection is found to operate in both sexes, but how it operates appears to differ. Intrasexual and intersexual differences in mating behaviour may be missed when evaluating population-wide preferences. That is, there can be underlying differences in how the sexes respond and the consequences of such differences should be considered when investigating mate choice. The results are considered in terms of the evolution of mating preferences, alternative mating strategies, assortative mating, the maintenance of trait variation in a population, and current methods to evaluate mating preferences.     

Learning large-scale spatial relationships in a maze and effects of MK-801 on retrieval in the rhesus monkey

Monkeys have strong abilities to remember the visual properties of potential food sources for survival in the nature. The present study demonstrated the first observations of rhesus monkeys learning to solve complex spatial mazes in which routes were guided by visual cues. Three monkeys were trained in a maze (6 m x 6 m) included of four different mazes. We recorded the cue and cup errors, latencies, and pathway for each trial. The data showed that monkeys learned the target place after three days in the first maze and spent a shorter time in learning the following mazes. The maze was an efficient method to measure the ability and proceeding of spatial memory in monkeys. Moreover, working memory can also be tested by using the maze. MK-801 at 0.02 mg/kg but not at 0.005 mg/kg impaired monkeys' retrieval of spatial memory after they learned all four mazes. The present maze may provide an efficient method to help bridging the gap in cognition between nonhuman primates and humans, and in particular to gain insight into human cognitive function and dysfunction.     

Repeatability of Male Mate Choice in the Mosquitofish, Gambusia holbrooki

Male mate choice has evolved in many species in which female fecundity increases with body size. In these species, males are thought to have been selected to favour mating with large females over smaller ones, thereby potentially increasing their reproductive success. While male mate choice is known to occur, it is less well studied than female mate choice and little is known about variation in mating preference among individual males. Here, we presented individual male eastern mosquitofish ( Gambusia holbrooki ) with paired females that differed in body size, and we quantified their mate preference on two consecutive days, allowing us to assess repeatability of preferences expressed. When males were allowed to view paired stimulus females, but not to acquire chemical or tactile cues from them, they exhibited a strong preference for large females over smaller ones. However, individual males were not consistent in the strength of their preference and repeatability was not significant. When individual males were allowed to fully interact with pairs of females, the males again exhibited a preference for large females over smaller ones, as revealed by a greater number of attempted copulations with large females than with smaller ones. In the latter social context, individual male preference was significantly repeatable. These results indicate that male eastern mosquitofish from our Florida study population possess, on average, a mating preference for larger females and that this preference is repeatable when males socially interact freely with females. The significant repeatability for mating preference, based on female body size, obtained for male mosquitofish in the current study is consistent with the presence of additive genetic variation for such preferences in our study population and thus with the opportunity for the further evolution of large body size in female mosquitofish through male mate choice.     

What do male tench, Tinca tinca, advertise with morphological ornaments?

In contrast to females, tench Tinca tinca (L.) males have large pelvic fins with a thickened and bent second fin ray. Males also produce notable ventral protuberances during breeding, but the function of these male ornaments is not known. Using wild-caught fish, we found that both the size of pelvic fins and ventral protuberance were dependent on body mass/length ratio but not necessarily on condition. Plasma testosterone concentration and relative gonad mass were positively correlated with condition factor. Plasma testosterone concentration was not related to measures of non-specific immune function, but correlated positively with the size of pelvic fins corrected for body length. However, the studied male ornaments were not related to the measures of immune defence or to the load of Diplostomum spp. We did not find evidence for male–male dominance or female preference for large male characteristics within the natural variation in these traits. Thus, our study suggests that also other mechanisms than sexual selection on good genes might contribute to the maintenance of sexual dimorphism in tench.     

The relative importance of orange spot coloration and total length of males in female guppy mate preference

Female mate choice by multiple male traits is an important current topic in animal behavior. However, the relative importance among the multiple cues in female choice is not explored in most cases. Female guppies Poecilia reticulata use both the color saturation of orange spots and the total length of males as mate choice criteria. In the present study, we used digitally modified video playbacks to examine the relative importance of these two male traits to female mate preferences. We initially examined the effective difference in the color saturation of orange spots as well as that in total length between two stimulus male images. Females only showed a strong preference for a bright male image (compared to the dull image) when the difference in color saturation was large (91% versus 25%). Conversely, females only exhibited a preference for larger size when they were presented a choice between two relatively small male images (total length 26.0 mm versus 23.0 mm). When two male images in which both the two traits were modified were presented to females, they prioritized male images possessing higher color saturation of orange spots, indicating the color saturation of male orange spots to be a more important factor than the total length in their mate choice. The color saturation of orange spots may convey more reliable information about the males to the females than their total lengths. These findings imply that females may rank multiple male criteria depending on relative benefits or costs derived from their mate choice based on each criterion.     

On the role of sexual selection in ecological divergence: a test of body‐size assortative mating in the eastern newt Notophthalmus viridescens

Speciation processes initiated by divergent selection often fail to complete; yet, how sexual selection is involved in the progress of ecological speciation is rarely understood. Intraspecific body‐size variation affects mate preference and male–male competition, which can consequently lead to assortative mating based on body size. In the present study, we tested the importance of body size difference in the potential of assortative mating between the two eastern newt subspecies, larger Notophthalmus viridescens viridescens and smaller Notophthalmus viridescens dorsalis. Through differential expression of life‐cycle polyphenism, these two subspecies are adapted to contrasting environments, which has likely led to the subspecific body‐size difference. We found that males of both subspecies preferred larger females of N. v. viridescens as mates presumably because of the fecundity advantage of larger females. On the other hand, no evidence of female choice was found. Larger males of N. v. viridescens exhibited greater competitive ability and gained primary access to larger females of their own kind. However, smaller males were able to overcome their inferior competitive ability by interfering with larger males' spermatophore transfer and sneakily mating with larger females. Thus, the subspecific body‐size difference importantly affected sexual selection processes, resulting in nonrandom but not completely assortative mating patterns between the larger and smaller subspecies. Although life‐cycle polyphenism facilitates the intraspecific ecological divergence within N. v. viridescens sexual selection processes, namely smaller males' mate preference for larger females and sexual interference during spermatophore transfer, may be halting completion of the ecological speciation. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 884–897.     

Relationship of sexual dimorphism in canine size and body size to social,behavioral, and ecological correlates in anthropoid primates

Among anthropoid primates there are interspecific differences in the degree of sexual dimorphism in both body size and canine size. Within the suborder body size dimorphism and canine size dimorphism are positively correlated,r=0.76. This correlation suggests that the two dimorphisms are equally developed in some species, while in other species there is a differential degree of sexual dimorphism. An analysis of these results and their relation to social organization and other ecological variables reveals: (1) the degree of canine size dimorphism is closely related to the amount of male intrasexual selection in a given mating system; and (2) the degree of body size dimorphism is also related to male intrasexual selection, but may be modified (either enhanced or diminished) by selection pressure from factors such as habitat, diet, foraging behavior, antipredator behavior, locomotory behavior, and female preference.     

条纹短攀鲈的雄性个体大小、雌性偏好以及雄性之间的竞争

本研究考察了条纹短攀鲈(Trichopsis vittata)雄性个体的身体大小对雌性个体性偏好的影响以及对雄性之间竞争的影响。本研究设立了两种处理来研究雌性个体的性偏好以及雄性之间的竞争。在一种处理中,放入同样大小的雄性个体,而在另一种处理中,放入大小不同的雄性个体。结果表明,雄性个体的大小不影响雌性条纹短攀鲈的性偏好。在对雄性之间竞争的研究中,发现个体较大的个体获胜的次数比较多。在个体大小相同的处理中,雄性之间打斗的持续时间比另一种处理中的打斗持续时间长。对这两种处理中不同对抗行为的比较表明,个体大小相同处理组中的发声、咬、以及总体对抗行为发生得更为频繁。对个体大小不同处理组中的大、小个体的进一步观察也揭示出体型大的个体比体型小的个体有更多的追逐行为和更少的逃脱行为。这些结果表明,在雄性个体比雌性个体大的物种中,体型的性两型可能与雄性之间的竞争有关,而不是与雌性偏好有关。     

Preferences for Call Spectral Properties in Hyla intermedia

We studied the pattern of variation in the spectral properties of male advertisement calls and female preference functions for these same properties in the Italian treefrog (Hyla intermedia). The call spectral properties (fundamental and dominant frequencies) were highly negatively correlated with body size, they showed low within‐individual variation, and, at the population level, they were found to be under weak stabilizing selection. In two‐choice discrimination tests, females did not show preferences between calls with fundamental and dominant frequencies within two standard deviations from the population mean, whereas females significantly discriminated against calls when their frequencies were three (or more) standard deviations above or below the population mean. Consistent with the observed permissiveness in female preference over the call spectral structure, in the natural population, we found no evidence either of directional selection on male body size or of a size‐assortative mating pattern. The pattern of preferences observed at the population level did not mirror the preferences of individual females. In fact, in a multi‐trial discrimination experiment, females showed significant differences in their choice between the average frequency call and a two standard deviation lower than average frequency alternative, for which no significant preferences were observed at the population level. Variations in preference were not found to correlate with female body size.     

Evolutionary and ecological success is decoupled in mammals

Aim

To identify which factors distinguish ecologically successful mammalian clades (i.e., clades with a large combined range size) from less successful ones.

Location

Global.

Methods

We estimated the total range sizes for each individual mammalian subfamily and used phylogenetic regressions to identify the relative importance of factors related to colonization ability (body size and niche width) and adaptability (rate of evolution of body size and rate of evolution of climatic preference) in determining these ranges. We then estimated the importance of the same factors on the variation in diversification rate within mammals.

Results

We found strong support for a link between total range size and traits related to colonization ability. In particular, we found larger total range sizes among clades containing larger bodied species and clades with wider climatic niche width, while we did not find support for any predictors related to adaptability being linked to total range size. We also found that traits related to increased range size were associated with reduced diversification rate.

Main Conclusions

Range size for mammalian clades is mainly predicted by colonization ability, suggesting that most clades are limited by dispersal rather than their ability to adapt to new environments. The most ecologically successful (i.e., most widespread) mammalian clades tend to possess traits that reduce geographical isolation among populations, but the same traits tend to decrease diversification rates. Our results unveil a decoupling between evolutionary and ecological success in mammals.

     

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.     

Size‐Dependent Male Mate Preference and its Association with Size‐Assortative Mating in a Mangrove Snail,Littoraria ardouiniana

In many animals, body size plays a crucial role in mating success in the context of competition and preference for mates. Increasing evidence has shown that male mate preference can be size‐dependent and, therefore, an important driver of size‐assortative mating. To test this theory, mate choice experiments were performed during the three consecutive stages of mating behaviour, namely trail following, shell mounting and copulation, in the dioecious mangrove snail, Littoraria ardouiniana. These experiments identified two possible forms of size‐dependent male mate preference which could contribute to the formation of size‐assortative mating in these snails. Firstly, whereas small males were unselective, large males were selective and preferred to follow mucus trails laid by large females. Alternatively, the results can also be interpreted as all males were selective and adopted a mating strategy of selecting females similar to, or larger than, their own sizes. Both small and large males also copulated for longer with large than with small females, and this was more pronounced in large males. When two males encountered a female, they engaged in physical aggression, with the larger male excluding the smaller male from copulating with the female. This study, therefore, demonstrated that size‐dependent male mate preference may, along with male–male competition, play an important role in driving size‐assortative mating in these mangrove snails, and this may also be the case in other species that exhibit male mate choice.     

Nestling growth and song repertoire size in great reed warblers: evidence for song learning as an indicator mechanism in mate choice

Females of many songbird species show a preference for mating with males that have larger song repertoires, but the advantages associated with this preference are uncertain. We tested the hypothesis that song complexity can serve as an indicator of male quality because the development of the brain regions underlying song learning and production occurs when young birds typically face nutritional and other stresses, so that song reflects how well a male fared during post-hatch development. A key prediction of this hypothesis is that variation in nestling condition should correspond to variation in the adult song repertoires of individuals. We used data from a long-term study of the great reed warbler (Acrocephalus arundinaceus) to test this prediction, correlating two measures of nestling development with subsequent repertoire size of males. We found that the length of the innermost primary feather, a standard measure of development, significantly predicted first-year repertoire size. The relationship between repertoire size and body mass was nearly significant, in spite of the large variance inherent in this measure. These data support the idea that song may provide females with information about a male's response to developmental stress, which in turn is expected to correlate with indirect or direct benefits she might receive.     

Increase in song frequency decreases spermatophore size: correlative evidence of a macroevolutionary trade-off in katydids (Orthoptera: Tettigoniidae)

In many katydids, the male feeds his mate with a large gelatinous spermatophore. Males of most species also produce elaborate calling songs. We predicted a negative relationship between spermatophore size and call frequency because of trade-offs between these two costly traits. Our comparative analysis controlling phylogeny and body size supported this prediction. Although call frequency is expected to decrease with increasing body size, after controlling for phylogeny, both variables were not related. Finally, given that song frequency and spermatophore size are likely targets of sexual selection, we examined the relationship between these variables and sexual size dimorphism (SSD) which can be influenced by sexual selection on body size. We found that only female body size was positively related to SSD, suggesting that natural and/or sexual selection on female body size may be stronger than sexual selection on male and spermatophore size.