Beluga whales (Delphinapterus leucas) and narwhals (Monodon monoceros) are arctic specialists. Both species show philopatry to their summer grounds, though the reason for this site tenacity is not well understood. Aside from migration routes, little is known about other aspects of monodontid ecology, such as their mating and feeding ecology. An understanding of the feeding ecology of a species may provide some insights into their mating ecology, and vice versa. The purpose of this thesis is to relative testes mass and dietary biomarkers to gain insights in the mating and feeding ecology of both species, as well as possible links between the two. Relative testes and brain masses and body masses of odontocetes were collected from the literature and analysed for correlations between sexual size dimorphism (SSD), relative brain mass, and relative testes mass. Results indicate that odontocete species follow a pattern of increasing SSD with decreasing testes mass. An examination of reproductive tracts from belugas and narwhal collected across the Canadian arctic was performed to examine differences in beluga and narwhal mating systems. Belugas were found to have larger relative testes masses, and narwhal testes masses were correlated with tusk length, indicating that sperm competition may play a larger role in the beluga mating system than for narwhal, and narwhal tusks may be honest indicators of male fitness. Investigations of narwhal and beluga feeding ecology using dietary biomarkers were conducted. In the summer, belugas appear to be congregating and feeding in the estuary plume during the summer, as opposed to along ice floe edges in the spring. Spring diets are representative of diets consumed during the beluga mating season, and no sexual segregation in carbon isotopes or fatty acids was apparent. There was no evidence for sexual segregation in feeding habits outside the mating season, either. Conversely, narwhal showed some evidence of sexual segregation outside the mating season, and the sexes may be feeding in different food webs. Results suggest that belugas may have a more promiscuous mating system, while narwhals are more polygynous. Implications for conservation for both species are discussed.

Evolution is not always straight-forward, as selection pressures may differ between different generations of the same species. This thesis focuses on the evolution of life history of the model species, the Green-veined White butterfly Pieris napi. In central Sweden P. napi has two generations per year. The directly developing summer generation is short-lived and time stressed, compared to the diapausing generation. In paper I polyandry, defined as female mating rate, was shown to differ between generations but was unaffected by environmental factors. In paper II both males and females of the direct developing generation were shown to eclose more immature than the diapausing generation, indicating larval time constraints. Consistent with this, diapausing males mated sooner than direct developers. Directly developing females, however, mated sooner after eclosion than diapausing females, even though they are more immature. This was shown to negatively affect fecundity, but can pay off when the season is short. Paper III shows that directly developing males have less sex pheromones at eclosion than diapausers, and the differences in sex pheromone production is consistent with developmental time constraints and the differences in mating system. In P. napi and other polyandrous butterflies, males transfer a large, nutritious ejaculate at mating. Large ejaculates confer advantages under sperm competition, but as they are costly, males should adjust ejaculate size to the risk of sperm competition. In paper IV we found that males transfer on average 20% larger spermatophores under high male competition than at low competition. The same effect could be observed if we added male sex pheromone to the air in a mating cage without male-male competition. Paper V shows that males of the two generations respond differently to an increase in male-male competition, with diapausing males transferring larger spermatophores than direct developers at high male competition risk. / <p>At the time of the doctoral defence the following paper was unpublished and had a status as follows: Paper 5: Submitted manuscript.</p>

The mating behaviour and reproductive ecology of the big-handed crab Heterozius rotundifrons was studied at Kaikoura between November 1997 and December 1998. H. rotundifrons was found at mean densities of 7.6 per m² (± 1.4) within the middle and low shore levels and varied little between seasons. The variance! mean ratio indicated that males and females aggregated within these shore levels. The sex ratio was significantly female biased during the majority of the year. Allometric growth rates indicated that males and females reached sexual maturity at 11 mm carapace width (CW). In males, spermatozoa production occurred between 9-9.99 mm CW. Ovigerous females were present every month except February. The first broods of the year were produced in March which coincides with a decrease in the female gonado-somatic index (GSI). These broods were incubated for approximately nine months whereas broods produced in August were incubated for only five months. Female brood production appeared to be cyclical, alternating between a winter incubation period and a summer incubation period. The completed cycle takes approximately three years with two broods produced during the cycle. Fecundity increased with female size but egg mortality was quite high (19%). Instantaneous mortality rate increased with increasing brood development. Females mate when recently moulted (soft-shelled). Although females moulted through out the year, in small numbers, there was a peak in female moulting during October and November. The operational sex ratio (OSR) was male biased during all months of the year. Females released an attractant prior to moulting which initiated pre-copulatory mate guarding by the male. Once the female moulted, copulation occurred approximately 6 h later. Copulation lasted for approximately 3 h and was followed by a period of post-copulatory mate guarding. Males increased the duration of post-copulatory mate guarding if another male was present. Large males out competed small males for receptive females. Males used their large cheliped to subdue competitors and to provide protection for the soft female. Mate guarding was shown to reduce cannibalism from other females. Spermatozoa are packaged in spermatophores within the vas deferens of males but are quickly dehisced within the spermathecae (ventral-type) of newly mated females. Last male to copulate probably achieves the highest level of paternity. Postcopulatory mate guarding by the male was found and ejaculates were found in discrete packets within the spermatheca. Sperm competition appeared to be important because large males displaced small males during copulation, males left when a female was still receptive and the females could retain sperm between moults. It is concluded that H. rotundifrons probably has a polygynous mating system in which males compete for soft females (female centered competition)

The honey possum Tarsipes rostratus, a marsupial endemic to South-Western Australia, feeds exclusively upon nectar and pollen. It is one of the smallest marsupials, with adult females (8-12g) significantly larger than adult males (6-9g). Honey possum males have the longest sperm (356µm) recorded for any mammaland the testes represent 4.2% body weight, amongst the largest recorded formammal species. These features suggest that sperm competition is an importantpart of the mating system. This study used a combination of field based studies,DNA analysis and histological examination of the female reproductive tract toinvestigate the life history, multiple paternity and reproduction of the honey possum innatural populations in the Fitzgerald River National Park (FRNP), on the south coastof Western Australia. This study drew upon earlier work on the honey possum in the FRNP in order to describe its life-history. The honey possum is short-lived (1-2 years), and attains sexual maturity whilst still growing. All four teats are occupied after birth, but the litter is reduced to 2 or 3 young during pouch life. The young have a relatively slow rate of growth. Breeding occurs continuously throughout the year, but is affected by the flowering phenologies of its foodplants. The greatest proportion of females with pouch-young occurs in winter; there are fewest pouch-young in autumn, a time of year when there is a dearth of flowers. Honey possums are essentially solitary animals, with no structured social unit, and male and female home ranges overlap. In captivity they are largely tolerant of one another, but larger females are behaviorally dominant to smaller females and to males. The densities and structure of the honey possum populations in the FRNP were analyzed from trapping data collected over 19 years. Population densities fluctuated significantly from season to season throughout the year, with changes in the flowering food resources available. There were also year-to-year differences in the intensity of those fluctuations, and these were significantly associated with rainfall in the previous year, and probably mediated through a lag effect in the flowering of the honey possum’s foodplants. The greatest densities of animals occurred over winter. In years following high rainfall, mean winter densities reached 88 individuals per hectare. The lowest densities occurred in spring, and in years following low rainfall mean spring densities fell to 8 individuals per hectare. Even at these lowest densities, there is still the potential for interaction between males and females. A succession from high to low, then back to high densities was seen during the three years of the present study (2000-2002) and this shadowed a similar succession of changes in rainfall. The proportion of females with pouch-young was significantly affected by the season, and by rainfall in the previous year. Years following low rainfall had a lower proportion of females in a condition to breed. The autumn dip in breeding that occurred in all years was exacerbated following dry years. Of those females that did breed in 2001, a time of low resources, there was no difference in the size of the litter compared to 2000 and 2002, times of higher resource availability. The sex-ratio of pouch young was at parity, but there was a slight bias towards males among both juveniles (56%) and adults (58%). This was probably due to the greater movements shown by males. Sex ratios were not affected by changes in rainfall and density. Male-biased dispersal was detected using genetic data and the movement patterns of males showed that they moved greater distances than females during their normal activity. Analysis of four microsatellite loci revealed extremely high levels of variation, with 28 to 50 alleles per locus and a mean expected heterozygosity of 0.95. These are amongst the highest seen in any microsatellite study of vertebrates. There was multiple paternity in 86% litters, using a minimum number of sires per litter method, and in 95% litters, using an estimated number of sires method based upon the relatedness of litter males. This indicates that multiple mating is frequent in female honey possums and is evidence for sperm competition. The estimated number of sires in a litter was often three or four. In 41% of cases, the number of sires was less than the number of young in the litter, indicating that some males were more successful at siring offspring than others. Nevertheless, no more than two offspring in a litter were known to have been sired by the same male. Despite marked fluctuations in density from high in 2000, to low in 2001, then high again in 2002, the level of multiple paternity remained equally high in all years. Embryonic diapause and female reproduction was investigated in the honey possum. All adult females examined, both with and without pouch-young, were either close to oestrus, had ovulated or were carrying conceptuses. The honey possum has a postpartum oestrus and it was evident that this occurs approximately 2-4 days after birth. Cleavage and formation of the unilaminar blastocyst appears to occur rapidly over approximately 5 days. Embryonic diapause proceeded in a two phase manner similar to other small possum species. The unilaminar blastocyst expanded rapidly at first; and then, from about 18-20 days after birth, the diameter of the blastocyst remained constant at approximately 1.2-1.8mm. No growth or development beyond the unilaminar stage was observed during pouch-life. The first signs of reactivation occurred during lactation, after pouch exit, and expansion of the blastocyst only occurred in one post-lactational female. The development of the corpus luteum appeared different to patterns described for other marsupials, but its formation coincided with the formation of the unilaminar blastocyst. The diameter of the corpus luteum remained constant throughout diapause. The histology of the reproductive tract was generally similar to other marsupials. There were no sperm storage crypts in the female reproductive tract. The length of pouch-life in the honey possum was 55-65 days, and the interval between litters of the same size varied between 65 and 100 days. Embryonic diapause may reduce the time between production of successive litters in the honey possum, but lifetime reproductive potential is reasonably low. Females had up to four litters over the period that they were captured. Thus, each litter represents a substantial proportion (25%) of a female’s lifetime reproductive output. Reproductive amortization occurred, with 61% loss overall, due to overproduction of ova, loss of conceptuses and reduction of the litter during lactation. The behavioural dominance of females suggests that multiple mating is an active strategy, and this presumably allows the genetic quality of their offspring to be maximized. Males that succeed in sperm competition may be of better intrinsic quality. Overproduction of conceptuses by females presents the opportunity for them to select those fertilized by intrinsically viable males or genetically compatible males. Sexually active males are present all year round. Females were not synchronous in their sexual receptivity, and this would lead to a skewed operational sex ratio, with more reproductive males than oestrous females. Since adult males are significantly smaller than adult females and possess no ornaments or armaments, it is unlikely that males overtly fight for access to females. Rather, males appear to monitor the reproductive status of females through smell, and probably compete in their ability to locate oestrous females. The risk and intensity of sperm competition is high, sexual selection for a large investment in spermatogenesis is evident and competition after copulation is probably an important factor in the mating system. It is likely that males, as well as females mate multiply, and the mating system is promiscuous.

Elaborate sexual ornaments evolve because mate choice exerts strong sexual selection favouring individuals with high levels of ornament expression. Consequently, even at evolutionary equilibrium, life history theory predicts that ornamental traits should be under directional sexual selection that opposes contrasting selection to reduce the costs associated with their maintenance. Otherwise, the resources used to maintain ornaments should be used to improve other life history functions. Elaborate female ornaments have only evolved in a few species, despite females commonly experiencing strong sexual selection. One explanation for this rarity is that male preferences for female ornaments may be self-limiting: females with higher mating success become less attractive because of the lower paternity share they provide to mates with every additional sperm competitor. The unusual species in which female ornaments do occur can provide rare insight into how selection can favour the expression of expensive characters in females despite their costs. The main goal of my thesis was to determine how sexual selection acts on exaggerated sexual ornaments, and give new insight into how these ornaments may have evolved, in spite of the self-limiting nature of selection on male preferences. To determine the strength of sexual selection acting on female ornamentation in dance flies, we developed new microsatellite markers to assess polyandry rates by genotyping stored sperm in wild female dance flies. We first used polyandry rates to determine whether ornament expression was associated with higher mating success in female Rhamphomyia longicauda, a species that has evolved two distinct and exaggerated female ornaments. Contrary to our predictions, we found no evidence that females with larger ornaments enjoy higher mating success. We then compared polyandry rates in R. longicauda to those of two other species of dance fly, one (Empis aestiva) that has i independently evolved female ornaments on its legs, and another (E. tessellata) that does not possess any discernable female ornaments. We also estimated the opportunity for sexual selection, which we found to be similar and relatively low in all three species. Moreover, the standardized sexual selection gradients for ornaments were weak and non-significant in all three species. Females with more elaborate ornaments, in both within- and cross-species comparisons, therefore did not enjoy higher mating success. Overall, these results suggested that sexual selection operates rather differently in females compared to males, potentially explaining the general rarity of female ornaments. Our amplifications of stored sperm were able to reveal more than just mate numbers. We developed new methods to study patterns of sperm storage in wild female dance flies. We investigated how the skew in sperm genotypes from mixed sperm stores changed with varying levels of polyandry. Our data suggested that sperm stores were dominated by a single male in R. longicauda, and that the proportion of sperm contributed by this dominant male was largely independent of the number of rival males’ sperm present in the spermatheca. These results were consistent with the expectation of males using sperm ‘offence strategies’ in sperm competition and that the most successful male is likely to be the female’s last partner before oviposition. As a whole, my thesis contributed new molecular resources for an understudied and fascinating group of organisms. It exploited these new resources to provide the first estimates of lifetime mating success in several related species, and suggested that the general prediction that ornament expression should covary with sexual selection intensity does not seem to hold in this group. Instead, both the unusual prevalence of ii ornaments and the inconsistent evidence for sexual selection that sustains them in dance flies may owe their existence to the confluence of two important factors. First, the conditions under which sperm competition occurs: as last male precedence is likely, males are selected to prefer the most gravid females to secure a high fraction of her offspring’s paternity as they are unlikely to mate again before oviposition. Second, potent sexually antagonistic coevolution between hungry females and discerning males: females have evolved ornaments to disguise their stage of egg maturity to receive the benefits of nuptial gifts, while males face the challenge of distinguishing between gravidity and ornamentation in females.

No description available.

[Truncated abstract] Despite the costs associated with mating, females of many taxa solicit multiple mates during a single reproductive event (polyandry). Polyandry is clearly adaptive when females gain direct benefits from males at mating. However, polyandry has also been shown to increase female fitness in the absence of direct benefits. Thus, a number of genetic benefit hypotheses have been developed to account for the origin of this behaviour. Although not mutually exclusive, a distinction lays between genetic benefits that propose defense against reproductive failure (nonadditive genetic effects), and those that propose benefits from intrinsic sire effects (additive genetic effects). Nonadditive genetic benefits of polyandry have been documented in a number of species; by soliciting multiple mates females can avoid inbreeding and other forms of incompatibility between parental genotypes. Polyandry may also increase female reproductive success when genetically superior males have greater success in sperm competition, and produce better quality offspring. An inevitable consequence of polyandry is that sperm from rival males will overlap in the female reproductive tract and compete to fertilise the ova. The outcome of sperm competition is typically determined by bias in sperm use by the females, interactions between parental genotypes, and ejaculate characteristics that provide a fertilisation advantage. Thus, sperm competition is recognised as a persuasive force in the evolution of male reproductive traits. Comparative analyses across species, and competitive mating trials within species have suggested that sperm competition can influence the evolution of testis size and sperm production, and both sperm form and sperm function. ... After six generations of selection I observed phenotypic divergence in litter size - litter size increased in the polyandrous lines but not in the monandrous lines. This result was not attributable to inbreeding depression, or environmental/maternal effects associated with mating regime. Genetic benefits associated with polyandry could account for this result if increased litter size were attributable to increased embryo survival. However, males from the polyandrous lineages were subject to sperm competition, and evolved ejaculates with more sperm, suggesting that evolutionary increases in litter size may in part be due to improved male fertility. Finally, Chapter Five is an investigation of the natural variation in levels of polyandry in the wild, and the potential for sperm competition to drive macroevolutionary changes in male reproductive traits among geographically isolated island populations of house mice. I sampled seven island populations of house mice along the coast of Western Australia and, by genotyping pregnant females and their offspring, determined the frequency of multiply sired litters within each population. I applied the frequency of multiple paternity as an index of the risk of sperm competition, and looked for selective responses in testis size and ejaculate traits. I found that the risk of sperm competition predicted testis size across the seven island populations. However, variation in sperm traits was not explained by the risk of sperm competition. I discuss these results in relation to sperm competition theory, and extrinsic factors that influence ejaculate quality.

Inbreeding can have profound negative effects on individuals by reducing fertility and viability. In populations, inbreeding depression can reduce growth rates and increases extinction risk. The aims of this thesis are to investigate inbreeding depression in male guppies (Poecilia reticulata) and to study the evolution of mechanisms for inbreeding avoidance in females, using guppies from a feral population in Queensland, Australia. Male guppies are highly polymorphic in their sexual ornamentation, indeed they show one of the most extreme polymorphisms observed in nature. Female guppies exhibit complex mate choice based on preferences for ornamentation, as well as social context. I aim is to examine how these factors of inbreeding avoidance alter sexual selection. In male guppies I found strong inbreeding depression in male sperm numbers, which is amplified under semi-natural compared to laboratory conditions (Chapter 2). Moreover, inbreeding depression results in low fertility under sperm competition: an experiment using artificial insemination techniques reveals that highly inbred males are heavily disadvantaged in gaining paternity (Chapter 3). On population level, inbreeding depression is manifest in reduced growth rates, predominantly in the early stages of inbreeding (Chapter 4). Population growth at inbreeding coefficients f=0.375-0.59 did not seem to lead to inbreeding depression, whereas lower levels of inbreeding reduced population growth. Although the growth rates in inbred populations appear normal, severe inbreeding depression is uncovered after outbred immigrants are added. Specifically, male immigrants are most efficient in short-term genetic rescue, probably due to insemination of large numbers of females whereas females are limited in the number of eggs they can produce (Chapter 4). Male ornamental traits show significant inbreeding depression in semi-natural conditions only (Chapters 2 & 3). Inbreeding avoidance mechanisms seem to have evolved in females: they prefer courtship displays of non-inbred males (Chapter 2), unfamiliar males (Chapter 5) and males with rare patterns (Chapter 6). This preference might increase the mating success of immigrants, and may have evolved to facilitate the avoidance of inbreeding. Together with context-independent preferences for ornament combinations (Chapter 6), it also offers an explanation for the maintenance of polymorphism in this species.

Inbreeding can have profound negative effects on individuals by reducing fertility and viability. In populations, inbreeding depression can reduce growth rates and increases extinction risk. The aims of this thesis are to investigate inbreeding depression in male guppies (Poecilia reticulata) and to study the evolution of mechanisms for inbreeding avoidance in females, using guppies from a feral population in Queensland, Australia. Male guppies are highly polymorphic in their sexual ornamentation, indeed they show one of the most extreme polymorphisms observed in nature. Female guppies exhibit complex mate choice based on preferences for ornamentation, as well as social context. I aim is to examine how these factors of inbreeding avoidance alter sexual selection. In male guppies I found strong inbreeding depression in male sperm numbers, which is amplified under semi-natural compared to laboratory conditions (Chapter 2). Moreover, inbreeding depression results in low fertility under sperm competition: an experiment using artificial insemination techniques reveals that highly inbred males are heavily disadvantaged in gaining paternity (Chapter 3). On population level, inbreeding depression is manifest in reduced growth rates, predominantly in the early stages of inbreeding (Chapter 4). Population growth at inbreeding coefficients f=0.375-0.59 did not seem to lead to inbreeding depression, whereas lower levels of inbreeding reduced population growth. Although the growth rates in inbred populations appear normal, severe inbreeding depression is uncovered after outbred immigrants are added. Specifically, male immigrants are most efficient in short-term genetic rescue, probably due to insemination of large numbers of females whereas females are limited in the number of eggs they can produce (Chapter 4). Male ornamental traits show significant inbreeding depression in semi-natural conditions only (Chapters 2 & 3). Inbreeding avoidance mechanisms seem to have evolved in females: they prefer courtship displays of non-inbred males (Chapter 2), unfamiliar males (Chapter 5) and males with rare patterns (Chapter 6). This preference might increase the mating success of immigrants, and may have evolved to facilitate the avoidance of inbreeding. Together with context-independent preferences for ornament combinations (Chapter 6), it also offers an explanation for the maintenance of polymorphism in this species.

<p>The evolutionary goal of individuals is reproduction and sexual selection favours traits improving reproductive success. When males invest less than females in offspring, males have potentially a higher reproductive rate than females. This typically results in sex-specific reproductive strategies of male-male competition and female choice of mating partner. Under polyandry, sexual selection can continue after copulation as sperm competition and cryptic female choice. This thesis focuses on male and female pre- and post-copulatory reproductive strategies in the promiscuous red junglefowl, <i>Gallus</i> <i>gallus ssp.</i>, and its domestic subspecies the domestic fowl, <i>Gallus gallus</i> <i>domesticus</i>. Males impose high re-mating rates on females, which triggers female resistance in copulations. In addition, when sexual harassment increases, females re-mate at times of day when male mating propensity is lower, to avoid intense sexual harassment. Males allocate sperm supplies differentially according to (i) variation in female polyandry and own competitive ability, (ii) earlier sperm investment in a female, and (iii) female reproductive quality, signalled by female comb size. Males also perform ‘aspermic’ copulations (i.e. copulations with no semen transfer), which inhibit polyandry and in turn reduce sperm competition. In mating opportunities with relatives, males do not avoid inbreeding. However, females avoid inbreeding before copulation through kin recognition and after copulation by selecting against related males’ sperm. These results show that selection on males to re-mate at higher rates than females and copulate indiscriminately according to partner relatedness, trigger counteracting female responses, creating the potential for sexual conflict over fertilisation. Teasing apart pre- and post-copulatory strategies and the contribution of each sex therefore becomes crucial in order to understand the evolution of reproductive strategies and the mechanisms affecting paternity.</p>