Testing the beneficial acclimation hypothesis: temperature effects on mating success in a butterfly

Traditionally, it has been assumed that all acclimation changesto the phenotype enhance the performance of an individual organismin the environment in which those changes were induced (beneficialacclimation hypothesis [BAH]), a theory that has been repeatedlychallenged in recent years. We here use a full-factorial designwith 2 developmental and 2 acclimation temperatures to testtheir effects on reproductive performance in the tropical butterfly,Bicyclus anynana. Competition experiments among virgin malesfrom different thermal groups revealed that, at 20 °C, bothgroups acclimated to 20 °C achieved more than twice as manymatings as those acclimated to 27 °C, whereas at 27 °C,only one group (acclimated to 27 °C) outperformed all others.Chill-coma recovery times were also longer for butterflies thatdeveloped at higher temperatures, indicating that butterfliesresponded physiologically to the temperatures at which theywere reared. Our results support the BAH at least in part, anddo not support any alternative hypotheses.     

Delayed mating and its cost to female reproduction in the butterfly,Eurema hecabe

The timing of mating of females under semi-natural condition, male ejaculate production and their effects on female fecundity were examined inEurema hecabe. Age of the first mating of females varied, and the number of matings increased with age. Male spermatophore production depended on age and body mass. The spermatophore mass at the second mating depended only on the interval between the first and second matings. The timing of the first mating and the spermatophore mass did not affect female fecundity. The timing of mating of females relative to the role of male spermatophores in female fecundity and male mating strategy are discussed.     

Natural variation in female mating frequency in a polyandrous butterfly: effects of size and age

In the polyandrous gift-giving butterfly Pieris napi, females mature at a smaller size than males under poor food conditions, so it has been suggested that females can compensate for their smaller size through nuptial feeding. We tested this hypothesis by assessing female polyandry in relation to female size in a study of a wild bivoltine population and in a laboratory experiment. Contrary to expectation, larger females had a higher mating frequency. In the wild population female polyandry was positively correlated with size and in the laboratory experiment larger females were also more polyandrous. Hence, smaller females cannot compensate for their size by increasing their mating frequency, perhaps because the rate of spermatophore breakdown sets the limit for polyandry and larger females are able to break down the spermatophore faster. In addition, the lifetime number of matings for wild females varied between one and five. As previous studies indicate that female fitness in P. napi appears to increase monotonically with number of mates as a result of the increase in spermatophore material received, it is surprising that 12% of the wild females in the oldest age classes had mated only once and that another 35-40% had mated only twice. This apparently maladaptive behaviour is discussed in terms of sexually antagonistic coevolution and whether environmental conditions influence optimal mating frequency. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Male genital morphology and its influence on female mating preferences and paternity success in guppies

In internally fertilizing species male genitalia often show a higher degree of elaboration than required for simply transferring sperm to females. Among the hypotheses proposed to explain such diversity, sexual selection has received the most empirical support, with studies revealing that genital morphology can be targeted by both pre-and postcopulatory sexual selection. Until now, most studies have focused on these two episodes of selection independently. Here, we take an alternative approach by considering both components simultaneously in the livebearing fish, Poecilia reticulata. We allowed females to mate successively (and cooperatively) with two males and determined whether male genital length influenced the female's propensity to mate with a male (precopulatory selection, via female choice) and whether male genital size and shape predicted the relative paternity share of subsequent broods (postcopulatory selection, via sperm competition/cryptic female choice). We found no evidence that either episode of sexual selection targets male genital size or shape. These findings, in conjunction with our recent work exposing a role of genital morphology in mediating unsolicited (forced) matings in guppies, further supports our prior speculation that sexual conflict may be an important broker of genital evolution in this species.     

Sex-specific fitness effects of nutrient intake on reproduction and lifespan

Diet affects both lifespan and reproduction [1-9], leading to the prediction that the contrasting reproductive strategies of the sexes should result in sex-specific effects of nutrition on fitness and longevity [6, 10] and favor different patterns of nutrient intake in males and females. However, males and females share most of their genome and intralocus sexual conflict may prevent sex-specific diet optimization. We show that both male and female longevity were maximized on a high-carbohydrate low-protein diet in field crickets Teleogryllus commodus, but male and female lifetime reproductive performances were maximized in markedly different parts of the nutrient intake landscape. Given a choice, crickets exhibited sex-specific dietary preference in the direction that increases reproductive performance, but this sexual dimorphism in preference was incomplete, with both sexes displaced from the optimum diet for lifetime reproduction. Sexes are, therefore, constrained in their ability to reach their sex-specific dietary optima by the shared biology of diet choice. Our data suggest that sex-specific selection has thus far failed fully to resolve intralocus sexual conflict over diet optimization. Such conflict may be an important factor linking nutrition and reproduction to lifespan and aging.     

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.     

Genetic effects on mating success and partner choice in a social mammal

Mating behavior has profound consequences for two phenomena--individual reproductive success and the maintenance of species boundaries--that contribute to evolutionary processes. Studies of mating behavior in relation to individual reproductive success are common in many species, but studies of mating behavior in relation to genetic variation and species boundaries are less commonly conducted in socially complex species. Here we leveraged extensive observations of a wild yellow baboon (Papio cynocephalus) population that has experienced recent gene flow from a close sister taxon, the anubis baboon (Papio anubis), to examine how admixture-related genetic background affects mating behavior. We identified novel effects of genetic background on mating patterns, including an advantage accruing to anubis-like males and assortative mating among both yellow-like and anubis-like pairs. These genetic effects acted alongside social dominance rank, inbreeding avoidance, and age to produce highly nonrandom mating patterns. Our results suggest that this population may be undergoing admixture-related evolutionary change, driven in part by nonrandom mating. However, the strength of the genetic effect is mediated by behavioral plasticity and social interactions, emphasizing the strong influence of social context on mating behavior in socially complex species.     

Evidence for minority male mating success and minority female mating disadvantage in Drosophila ananassae

Frequency-dependent mating success was tested for three pairs of wild-type and mutant strains of Drosophila ananassae, MY and yellow body color (y), PN and claret eye color (ca), and TIR and cut wing (ct). The two strains of each pair were chosen for their approximately equal mating propensities. Multiple-choice experiments, using different experimental procedures, were employed. The tests were carried out by direct observation in Elens-Wattiaux mating chambers with five different sex ratios (4:16, 8:12, 10:10, 12:8, and 16:4). There was no assortative mating and sexual isolation between the strains, based on 2 x 2 contingency chi2 analysis and isolation estimate values. One-sided rare male mating advantages were found in two experiments, one for ca males and the other for wild-type males (TIR). However, no advantage was found for rare males in the experiment with MY and y flies. Mating disadvantages for rare females were found for sex-linked mutants (y and ct). Two different observational methods (removal or direct observation of mating pairs) imparted no overall significant effects on the outcome of the frequency-dependent mating tests.     

Male competition and female choice interact to determine mating success in the bluefin killifish

Whether male competition and female choice act in concert, independently,or in opposition is a critical issue for understanding sexualselection. In complex social systems, the outcomes of pairwiseinteractions may not be accurate indicators of how sexual selectionemerges. We investigated how female choice and male competitioninteract in the bluefin killifish, Lucania goodei, in a 3-stagedexperiment where 1) females could choose between 2 males, 2)those males could interact in the presence of that female, and3) females and males could freely interact and spawn. In thepairwise stages (1 and 2), females displayed pronounced preferencesbetween males and male competition produced a distinctly dominantindividual. None of the morphological traits, including color,measured in males were associated with either female preferenceor male dominance. When all 3 fish interacted (stage 3), maleactivity level was the sole predictor of spawning success. Maleswith elevated activity levels were more aggressive toward malesand females, exhibited intensified courtship, and obtained morespawns. Female preference did not predict the number of spawnswith a male, but it did predict her latency to spawn; femalesspawned more quickly with preferred males. Thus, male competitionand female choice interact to determine reproductive success,but there is evidence for conflict and a cost to females ofassociating with dominant males. Reproductive success in thisspecies is not easily predicted from simple measures of morphologyor female preference and is influenced by complex social interactions,both between males, and between males and females.     

Aspartokinase II from Bacillus subtilis is degraded in response to nutrient limitation

Aspartokinase II from Bacillus subtilis was shown by immunochemical methods to be regulated by degradation in response to starvation of cells for various nutrients. Ammonium starvation induced the fastest aspartokinase II decline (t1/2 = 65 min), followed by amino acid starvation (t1/2 = 80 min) and glucose limitation (t1/2 = 120 min). Loss of enzyme activity was closely correlated with the disappearance of the alpha subunit; degradation of the beta subunit was somewhat delayed or slower under some conditions. Pulse-chase experiments demonstrated that aspartokinase II was stable during exponential growth; the synthesis of the enzyme rapidly declined in response to nutrient exhaustion. The degradation of aspartokinase II was interrupted by inhibitors of energy production and protein synthesis but was not changed in a mutant lacking a major intracellular protease. Mutants lacking a normal stringent response displayed only a slight decrease in the rate of aspartokinase II degradation, even though aspartate transcarbamylase was degraded more slowly in the same mutant cells. These results indicate that although energy-dependent degradation of biosynthetic enzymes is a general phenomenon in nutrient-starved B. subtilis cells, the degradation of specific enzymes probably involves different pathways.     

High-throughput metabolic screening of microalgae genetic variation in response to nutrient limitation

Metabolomics - Microalgae produce metabolites that could be useful for applications in food, biofuel or fine chemical production. The identification and development of suitable strains require...     

Multiple mating and its effect on the reproductive success of female Epiphyas postvittana (Lepidoptera: Tortricidae)

Abstract.

• 1 Multiple mating and its effect on reproductive performance of female Epiphyas postvittana (Walker) moths were studied under controlled conditions.
• 2 The age at which the moths mated for the first time ranged from the first to the tenth day after emergence, but 71% of first matings were during the first 3 days.
• 3 The majority (63%) of females had one or two spermatophores in the bursa copulatrix. Some (24%) were found with three to five spermatophores, whereas no successful mating occurred among 13% of individuals. The number of matings was partly dependent on the number of mates available to the female. Between the range of sex ratios of one male to one female and four males to one female maximal mating success occurred at the ratio of three males to one female.
• 4 Virgin females were capable of egg-laying, but mating stimulated and accelerated oviposition. Mated individuals laid twice as many eggs as unmated ones.
• 5 The level of copulatory activity did not influence the longevity of females irrespective of the number of males available to them.
• 6 Sex ratios with greater than one male to a female improved the reproductive success by marginally increasing fecundity and fertility.
• 7 It is concluded that multiple mating would enhance population growth, and is of particular benefit to populations with a preponderance of females, as is known to occur naturally in this species.

     

Variation in developmental time affects mating success and Allee effects

A fundamental question in biological conservation and invasion biology is why do some populations go extinct? Allee effects, notably those caused by mate location failure, are potentially key factors leading to the extinction of sparse populations. Several previous studies have focused on the inability of males and females to locate each other in space when populations are at low densities but here we investigate the effects of differences in the timing of male and female maturation on mating success. We develop a generalized model to clarify the role of protandry (the appearance of males before female emergence) and variability in adult maturation times. We show that temporal asynchrony can substantially reduce the probability of successful mating. We then apply this generalized model to estimate mating success in invading populations of the gypsy moth in North America in relation to local climate and its associated seasonality. Considerable geographic heterogeneity was observed in simulated mating success and this variability was not correlated with previous evaluations of bioclimatic requirements and habitat suitability. Furthermore, we found that the generalized model of temporal asynchrony provided reliable predictions and that detailed modeling of gypsy moth development was not necessary.     

Paternal effort and its relation to mating success in the European ground squirrel

The necessity for parental care is a driving force for determining mating systems and social organization. The European ground squirrel, Spermophilus citellus, is a polygynous, gregarious species in which male parental behaviour would not be expected. We had observed males digging in litter burrows that were later occupied by females and their offspring. Males never stayed overnight within these burrows. To determine whether this was some kind of paternal effort we tested the following hypotheses: (1) that male burrowing behaviour was directed towards the male's own offspring or towards the pregnant or lactating mother of the male's offspring; (2) that this behaviour had costs in terms of condition, decreased survival or fecundity; and (3) that it benefited offspring condition or survival. All three assumptions were met. Males worked on the litter burrow of their copulatory partners. Thus, this behaviour was directed towards the male's potential offspring. Male burrowing costs were seen in decreased foraging time and increased body mass loss. Offspring benefits were evident in increased mass at natal emergence. We conclude that male digging at litter burrows can be considered as paternal effort. Lastly, we considered the effects of polygyny on this male parental effort by comparing mating effort, mating success and paternal effort. High mating success was associated with high mating effort and low paternal effort. Moderate to low mating success was associated with lower mating effort and higher paternal effort, indicating a trade-off between the two.     

Transient response of Enterobacter aerogenes under a dual nutrient limitation in a chemostat.

Utilizing a chemostat with a dual nutrient limitation of nitrogen and phosphate, we examined the transient response of the culture following a pulse of one of the limiting nutrients (ammonia). This method provided quantitative evidence that cells can be grown under dual nutrient limitation. Furthermore, the pattern of response was consistent with the hypothesis that phosphate limitation restricts nucleic acid synthesis in the cell and that nitrogen limitation restricts protein synthesis. The net result is that under a phosphate limitation there is a restricted biosynthetic capacity which we feel is closely associated with the RNA content of the cell.