Mating system, mating behavior and the evolution thereof is the foundation of this study. More specifically the effect of inbreeding on the evolution of mating behavior is investigated. To this end the pollinating fig wasp, Platyscapa awekei, lends itself to inquiry about inbreeding and the effect on its behavior. A pollinating fig wasp female will lay her eggs inside a syconium, and all offspring will mate with each other. Interestingly the abovementioned pollinating wasp exhibits male dispersal, not commonly expected to occur in a haplodiploid species observed to inbreed frequently. Several theories attempt to explain the evolution of male dispersal in this case, but very little work has been done on the effect of inbreeding on the choice to disperse. In order to study the effects of inbreeding it was necessary to be able to measure the inbredness of individuals. For this reason I developed micro satellite markers both to determine the inbredness of individuals but also to derive parentage from offspring genotypes. With the inbreeding status in hand I had to correlate this with fitness measures in order to derive the effect of inbreeding on this species. Interestingly I found both inbreeding and outbreeding depression, with optimal fitness at some point between fully inbred and fully outbred status. I give some explanations for the occurrence of dispersal in this species but come to the conclusion that dispersal is merely part of a mixed mating system and that more detailed work need to be done to derive what the specific effect of dispersal is on fitness. / Dissertation (MSc(Agric))--University of Pretoria, 2009. / Genetics / unrestricted

Not much is known about the mechanisms affecting the genetic composition of populations of different species. To investi­gate one of these potential mechanisms, mating behaviour, the fruit fly Drosophila melanogaster, was chosen as an experimen­tal animal. To quantify mating behaviour in easily measurable parameters, it was subdivided into several distinct components; mating activity, mating time, mating competition ability and male mating capacity. As behavioural components to a great extent are influenced by environmental conditions all experiments were performed under controlled temperature and humidity. All components of mating behaviour were estimated by introducing females and males into mating chambers. Mating behaviour seems to be one of the major factors affect­ing the genetic composition of Drosophila melanogaster popula­tions. The experiments performed showed that differences in mating properties led to a substantial sexual selection among the genotypes. This selection was of a stabilizing type with regard to characters associated to bristle number and Y chromo­somal chromatin. This selection situation seems to warrant the retention of intermediate phenotypes in a population and will therefore contribute to the genetic variation present. Differences in mating properties were also shown to be able to maintain a balanced polymorphism for allozyme variants in populations. This maintenance was obtained through different forms of balancing selection as heterozygous superiority in sexual activity and balancing selection between female and male genotypes. Heterozygous superiority or overdominance in fitness always leads to balanced polymorphism through segre­gation of individuals with lowered fitness. The balancing selection between the female and male genotypes is best looked upon as a form of marginal overdominance, conferring the aver­aged highest fitness to the heterozygous genotype, thereby maintaining the polymorphism of the population. / <p>Härtill 5 uppsatser</p> / digitalisering@umu

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)

<p>This thesis focuses on reproduction in a simultaneous hermaphrodite with internal fertilization; the nudibranch <i>Aeolidiella glauca</i>. Unlike most other nudibranchs, where copulation is the rule, <i>A</i>. <i>glauca</i> was found to transfer sperm via external spermatophores that were attached to the partner's back. Despite elaborate courtship the actual spermatophore transfer, which always involved two animals only, was of short duration. In most matings (88%) spermatophores were reciprocally exchanged. </p><p><i>A. glauca</i> was further found to be very promiscuous. During mating and sperm transfer the receiver exerts considerable control over sperm, and manipulative behaviours designed to increase the donor's reproductive success are thus likely to have evolved. An example of such manipulative behaviour may be <i>A. glauca's</i><b> </b>unique spermatophore avoidance behaviour. I found that slugs carrying a sign of previous mating activity, i.e. a spermatophore, were discriminated against in a situation where mate choice was possible. The presence of spermatophores was further found to reduce slugs' ability to interrupt matings, and displace other slugs. Body size, however, had no direct effect on displacement in <i>A. glauca</i> as small slugs interrupted matings as successfully as large ones. Furthermore, pair formation and mating were found to be random with respect to size. This was true also for pairs formed in the field. </p><p>In addition to mate choice hermaphrodites may increase their reproductive success by differential sex allocation. I tested whether differing mate encounter rates had any effects on allocation to male and female function in <i>A. glauca</i>. Slugs with more mating opportunities mated more, and had higher proportional spermatophore production that others. As predicted they also laid significantly fewer eggs than slugs presented with partners less often.</p>

This thesis focuses on reproduction in a simultaneous hermaphrodite with internal fertilization; the nudibranch Aeolidiella glauca. Unlike most other nudibranchs, where copulation is the rule, A. glauca was found to transfer sperm via external spermatophores that were attached to the partner's back. Despite elaborate courtship the actual spermatophore transfer, which always involved two animals only, was of short duration. In most matings (88%) spermatophores were reciprocally exchanged. A. glauca was further found to be very promiscuous. During mating and sperm transfer the receiver exerts considerable control over sperm, and manipulative behaviours designed to increase the donor's reproductive success are thus likely to have evolved. An example of such manipulative behaviour may be A. glauca's<b> </b>unique spermatophore avoidance behaviour. I found that slugs carrying a sign of previous mating activity, i.e. a spermatophore, were discriminated against in a situation where mate choice was possible. The presence of spermatophores was further found to reduce slugs' ability to interrupt matings, and displace other slugs. Body size, however, had no direct effect on displacement in A. glauca as small slugs interrupted matings as successfully as large ones. Furthermore, pair formation and mating were found to be random with respect to size. This was true also for pairs formed in the field. In addition to mate choice hermaphrodites may increase their reproductive success by differential sex allocation. I tested whether differing mate encounter rates had any effects on allocation to male and female function in A. glauca. Slugs with more mating opportunities mated more, and had higher proportional spermatophore production that others. As predicted they also laid significantly fewer eggs than slugs presented with partners less often.

Männliche Säugetiere konkurrieren um eine nicht-teilbare Ressource (empfängnisbereite Weibchen) und sind üblicherweise das abwandernde Geschlecht, weshalb Kooperation zwischen Männchen der Intuition zu widersprechen scheint. Wenn die Kooperation jedoch für beide Partner vorteilhaft ist, indem sich z.B. ihr Paarungs-/Fortpflanzungserfolg erhöht, kann Kooperation eine plausible Strategie sein. Koalitionen können opportunistisch sein, also kurzfristig einen direkten Nutzen bieten, oder für einen zukünftigen Fortpflanzungserfolg und Aufstieg in der Rangordnung sorgen. Welche Art von Koalition auftritt, hängt von dem Konkurrenzpotential innerhalb einer Gruppe ab, das von der Fähigkeit des alpha-Männchen, rezeptive Weibchen zu monopolisieren, bestimmt wird. Es wird davon ausgegangen, dass Männchen den Rang bzw. die Stärke von potentiellen Koalitionspartnern und Kontrahenten abwägen müssen, um einen Partner zu rekrutieren, so dass die gemeinsame intrinsische Kampfkraft ausreicht um den Kontrahenten zu besiegen. Alternativ können Männchen vorherige Erfahrungen mit Gruppenmitgliedern nutzen, um zu entscheiden wen sie rekrutieren ("attitudinal partner choice") und verlässliche Partner wählen. Unter solchen Bedingungen kann die Wahl des Koalitionspartners durch Sozialbeziehungen beeinflusst werden. Diese Doktorarbeit sollte Aufschluss geben über die Kooperation zwischen Männchen, indem die Paarungskonkurrenz und Sozialbeziehungen von Männchen und der Einfluss von Koalitionen in einer gruppenlebenden, wilden Primatenart, dem Berberaffen (Macaca sylvanus), untersucht wurden. Dazu habe ich einen Bottom-Up-Ansatz genutzt, indem ich die vollständige Folge von Ereignissen analysierte, die zu Kooperation zwischen Männchen führte. Ich habe bestimmt, inwiefern Männchen den reproduktiven Zustand von Weibchen feststellen können, um das Potential zur Paarungskonkurrenz innerhalb von Gruppen empirisch abschätzen zu können. Ich habe das "Priority-of-Access"-Modell als Grundlage für eine Erforschung der männlichen Paarungskonkurrenz genutzt und habe die Faktoren untersucht, die zu Abweichungen von den Vorhersagen des Modells führen, vornehmlich das Verhalten der Weibchen und die männliche Koalitionsbildung. Die artspezifische Messung der Konkurrenz zwischen Männchen erlaubte eine kritische Evaluation eines mathematischen Modells, das konzipiert wurde, um verschiedene Typen von Koalitionsbildung innerhalb von Gruppen vorherzusagen (Pandit/van Schaik-Koalitionsmodell). Im Besonderen habe ich untersucht, wie die Vorhersagen des Modells zu empirischen Daten zweier Arten mit variablem Konkurrenzpotential (Berberaffen und Assam-Makaken, M. assamensis) passen. Die Sozialbeziehungen von Männchen wurden analysiert, um festzustellen, ob Berberaffen selbst in Zeiten intensiver Konkurrenz (während der Paarungszeit) langfristige Beziehungen formen. Schlussendlich wurde die Stärke männlicher Sozialbeziehungen untersucht um zu ermitteln, ob sie einen Anpassungswert durch die Kooperation in der Koalitionsbildung bieten, oder ob Koalitionspartner allein aufgrund ihres Dominanzstatus ausgewählt wurden. Es wurden Daten zweier Gruppen freilebender Berberaffen im Mittleren Atlasgebirge Marokkos von September 2009 bis August 2011 gesammelt. Ich habe über 2000 Stunden Verhaltensdaten aller Männchen in beiden Gruppen nach der Focus-Tier-Methode sowie ad libitum gesammelt, und 549 Koalitionen verschiedener Größe und unterschiedlichen Erfolges beobachtet. Zusätzlich wurden 155 weibliche Kotproben analysiert, um das Datum der Empfängnis mittels Enzymimmunassays von Gestagenmetaboliten festzustellen. Außerdem wurden weibliche Sexualschwellungen visuell eingestuft, um die Synchronität der Empfängnisse zu ermitteln. Die Analyse der weiblichen Hormonkonzentrationen zeigt, dass die Ovulation am wahrscheinlichsten im Zeitraum maximaler Sexualschwellung standfand. Allerdings konzentrierte sich das männliche Paarungsverhalten stärker auf die fertile Phase, was impliziert, das Männchen mehr als nur die Schwellungen an sich als Information nutzen können. Die Paarungshäufigkeit der Männchen stieg im Einklang mit dem sexualen Sozialverhalten der Weibchen. Bemerkenswerterweise zeigen meine Ergebnisse, dass Männchen gleichermaßen in Paarungen während der fertilen und nicht-fertilen (d.h. nach der Empfängnis) Phasen der Sexualschwellungen investieren. Obwohl diese zusätzlichen Sexualschwellungen das Monopolisierungspotential hochrangiger Männchen verringern, waren Paarungen zu Gunsten hochrangiger Männchen verschoben. Hochrangige Männchen haben aber keinen so großen Anteil der Paarungen erzielt, wie vom "Priority-of-Access"-Modell vorhergesagt wird. Weibchen haben regelmäßig Paarungen initiiert, in erster Linie mit mittelrangigen Männchen, was deren Paarungserfolg erhöhte, während Koaltionsbildung von Männchen deren Paarungserfolg unabhängig davon erhöhte. Regelmäßige Assoziationen mit Weibchen waren kostspielig für Männchen, da sie Ziele überbrückender Koalitionen ("bridging coalitions") wurden, was ihre zukünftigen Paarungsmöglichkeiten einschränkte. Hochrangige Männchen haben ihren Paarungserfolg nicht direkt mittels überbrückender Koalitionen ("bridging coalitions") erhöht, minderten aber den Einfluss des weiblichen Verhaltens. Außerdem bildeten Berberaffenmännchen langfristige Sozialbeziehungen die durch die höchst kompetitiven Paarungzeiten hindurch bestehen blieben. Männchen mit einer starken sozialen Bindung wurden mit höherer Wahrscheinlichkeit als Koalitionspartner rekrutiert, was nahe legt, dass für Männchen mehr als nur der Rang der verfügbaren Partner ausschlaggebend ist. Eine Prüfung des Pandit/van Schaik-Koalitionsmodells zeigte, dass unter hohem Konkurrenzpotential opportunistische Koalitionen genutzt werden sollten, um Zugang zu Weibchen zu gewinnen, die von hochrangigen Männchen monopolisiert sind. Indessen stimmten die empirischen Daten nicht mit den Vorhersagen unter mittlerem bis niedrigem Konkurrenzpotentials überein, bei dem männliche Affiliationen Rang-verändernde Koalitionen erleichtern könnten. Für diese werden vertrauenswürdige Partner benötigt, um die höherrangige Position zu verteidigen, sobald sie gewonnen wurde. Demnach können enge soziale Bindungen zwischen Männchen sowohl kurz- als auch langfristige Vorteile liefern, indem die Wahrscheinlichkeit, dass der Partner während einer Koalition abtrünnig wird, verringert wird. Zudem steht ein langfristiger Partner zur Verfügung, der erfolgreiche Rangveränderungen erleichtert wodurch enge soziale Bindungen letzlich sowohl den Status als auch den Paarungs-/Fortpflanzungserfolg erhöhen. Zusammenfassend erweitert meine Doktorarbeit die derzeitige Literatur über den Zusammenhang zwischen männlichen Fortpflanzungsstrategien, Sozialbeziehungen und Kooperation innerhalb von gruppenlebenden Säugetieren mit abwandernden Männchen. Durch die Untersuchung der vollständigen Beweiskette vom zwischenmännlichem Konkurrenzkampf hin zu Paarungserfolg und Kooperation durch das Schließen enger zwischenmännlicher Sozialbindungen, ergibt diese Studie ein umfassendes Bild mehrerer unabhängiger Forschungsansätze und könnte eine Vorlage für zukünftige Forschungsarbeiten bilden. Koalitionsbildung kann mutualistische Vorteile für beide Partner liefern, was nahelegt, dass Kooperation durch vorherige affiliative Interaktionen mit Gruppenmitgliedern durch "attitudinal partner choice" bestimmt sein könnte.

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 “risk allocation hypothesis” can predict how prey species will respond to predation risk, balancing vigilance with potentially risky behaviours. In order to maximize fitness, an optimal behavioural repertoire can evolve to respond to predation threat to allow for both survival and future fitness gains. High locomotor activity and time spent engaging in mating behaviours are expected to put Drosophila melanogaster at a greater risk to predation. With direct predator exposure, Drosophila are predicted to reduce activity and mating, which over years of exposure, will be reflected in evolved behavioural traits and evolved changes in the genome. Predation as a selective force shows alterations in flies genomes of experimentally evolved populations. Locomotor activity was found to be reduced in the presence of zebra jumping spiders (Salticus scenicus), presumably due to these spiders as visual hunters, using movement to detect prey. This behaviour is reflected in populations of Drosophila that have been constantly under selection by predators. Flies evolved with spider predators or mantid predators (Tenodera aridifolia sinensis) showed reduced locomotor activity when no predators are present. Interestingly, while alterations are seen for locomotory activity, the presumed risky behaviours of courtship and mating did not show an evolved response. Wild caught populations under threat from spiders, as well as the evolved populations when no predators were present showed no alterations in courtship or copulation behaviour. It appears that although there may be potential risks associated with mating behaviours, the benefits to future fitness when mating outweigh the potential costs from predation risks in Drosophila. / Thesis / Master of Science (MSc) / Predation is a profound selective force, with many anti-predator adaptations seen throughout the diversity of life. Antipredatory behavioural adaptations must balance immediate and future fitness effects, to maximize overall fitness. In Drosophila melanogaster, research into natural ecology and role of predation is generally lacking for behavioural & evolutionary studies. I will discuss research on the influence of predator exposure on Drosophila behaviours, as well as the evolution of Drosophila behaviours and genomes through experimentally evolved populations of Drosophila. While predation risk has resulted in changes in Drosophila locomotory activity, predation has not altered mating behaviours.

Worldwide, pharmaceutical compounds continue to increase in our aquatic environment. The predominant route into nature is through wastewater treatment plants since the elimination of residual pharmaceuticals is still not mainstream in WWTPs. Fluoxetine is an antidepressant which is commonly prescribed to treat human depression. Wastewater residual fluoxetine is typically found in waters around the world, and can thus affect exposed organisms, such as fish and invertebrates. However, how fluoxetine may affect mating behaviour in exposed organisms remains poorly understood, and particularly so in invertebrates. This is hampering our understanding of the consequences of our medicine leaking into nature because mating behaviour often affects fitness, and invertebrates are key organisms in food chains. Therefore, I here experimentally investigated long-term effects of environmental relevant concentration of fluoxetine (20 ng L-1) on mating behaviours of male and female freshwater isopod Asellus aquaticus. I demonstrate that fluoxetine reduced male mating attempts with receptive females. Further, there was a tendency for fluoxetine exposure to increase latency to form pre-copula. There was no effect of fluoxetine exposure on male latency to encounter females or female responses toward males. These results indicate that fluoxetine also can affect isopods by reducing mating behaviour. In the long-term, if reproduction is delayed or reduced, it may cause a reduction in populations and thus, alter the whole ecosystem.

The Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), a major pest of horticulture in eastern Australia, is a relatively poor coloniser of new habitat. This thesis examines behavioural properties that might limit the ability of B. tryoni to establish new populations. As the potential for B. tryoni to establish an outbreak population may be most directly limited by mechanisms associated with dispersal and mating behaviour, these two factors were the focus of this research project. The relevance of dispersal and mating behaviour for control of outbreak populations was assessed. Dispersal (i) Dispersal patterns of males and females are not different. Dispersal of post-teneral male B. tryoni from a point within an orchard near Richmond, New South Wales, was monitored following temporally replicated releases. Application of sterile insect technique (SIT) requires knowledge of dispersal from a release point so that effective release rates can be determined. In addition, dispersal following introduction to new habitat can lead to low or negative population growth and an Allee effect. In Spring and Autumn, 2001 � 2003, three different strains of B. tryoni were released: (1) wild flies reared from infested fruit collected in the Sydney Basin; (2) a laboratory-reared strain with a colour mutation (white marks); and (3) sterile flies obtained by gamma-irradiation of a mass-reared strain. Dispersal was monitored using a grid of traps baited with the male attractant, cuelure. During the majority of releases, flies were massmarked using a self-marking technique and fluorescent pigment powder to enable identification of recaptured flies. A preliminary study found that fluorescent pigment marks had no effect on adult survival and marks did not fade significantly in the laboratory over a period of five weeks after eclosion. As cuelure repels inseminated sexually mature female B. tryoni, unbaited, coloured flat sticky traps, and black and yellow sticky sphere traps baited with a food lure (protein autolysate solution) were used to supplement traps baited with cuelure. The effectiveness of these two sticky trap types was assessed, and recaptures used to compare patterns of dispersal from a release point by male and female B. tryoni. Fluorescent yellow (chartreuse), green, and clear unbaited flat sticky traps were relatively ineffective for monitoring dispersal of sterile male and female B. tryoni, recapturing only 0.1% of released sterile flies. Monitoring dispersal with sticky ball traps baited with protein autolysate solution was more successful, with yellow spheres and black spheres recapturing 1.7% and 1.5%, respectively. Trap colour had no effect on recaptures on flat sticky traps or sticky spheres. Equal recapture rates on yellow and black sticky sphere traps suggests that the odour of yeast autolysate solution was more important than colour for attraction of post-teneral flies to traps. Using the results of recaptures on odoriferous black and yellow sticky sphere traps within one week of release, regression equations of male and female recaptures per trap were found to be similar (Figure 4-3). This is the first study to clearly indicate that post-teneral dispersal patterns of male and female B. tryoni released from a point do not differ, enabling the use of existing models to predict density of both sexes of B. tryoni following post-teneral dispersal. (ii) Males disperse further in Spring than in Autumn, but this is not temperature-related. Analysis of replicated recaptures in traps baited with cuelure revealed that dispersal of male B. tryoni in an orchard near Richmond, New South Wales, was higher in Spring than in Autumn (Figure 5-6). As the maximum daily temperature was significantly higher in Spring than in Autumn this result was unexpected, since earlier studies have found that B. tryoni disperse at the onset of cool weather in search of sheltered over-wintering sites. Dispersal of post-teneral B. tryoni may have been affected by habitat suitability; it was found that seasonal trends in dispersal could have been influenced by local habitat variables. Low mean dispersal distances in Autumn may be explained by the presence of fruiting hosts in the orchard, or the availability of resources required by over-wintering flies. There was no significant correlation between temperature and mean dispersal distance, suggesting that higher rates of dispersal cannot be explained by temperature-related increases in activity. Recapture rate per trap was significantly negatively correlated with increasing daily maximum and average temperature. This may have consequences for detection of B. tryoni outbreaks in quarantine areas due to reduced cuelure trap efficiency. (iii) Maturity and source variation affect dispersal and response to cuelure. This research indicated that most male and female B. tryoni do not disperse far from a release point, suggesting that an invading propagule would not spread far in the first generation. However, there is considerable variation in flight capability among individuals. Comparison of wild, laboratory-reared white marks, and gamma-irradiated sterile male B. tryoni indicated that mean dispersal distance and redistribution patterns were not significantly affected by fly origin. Despite no difference in dispersal distance from the release point, recaptures of wild and sterile males per Lynfield trap baited with cuelure were highest within one week after release, whereas recaptures of white marks males per trap increased in the second week. This result may offer evidence to support the hypothesis that sterile male B. tryoni respond to cuelure at an earlier age. Rearing conditions used to produce large quantities of males for sterilisation by gamma-irradiation may select for earlier sexual maturity. Mating Behaviour (i) Density and sex ratio do not affect mating, except at low densities. Demographic stochasticity in the form of sex ratio fluctuations at low population density can lead to an observed Allee effect. The effect of local group density and sex ratio on mating behaviour and male mating success of a laboratory-adapted strain of B. tryoni was examined in laboratory cages. In the laboratory-adapted strain of B. tryoni used in this study, a group of one female and one male was sufficient for a good chance of mating success. The proportion of females mated and male mating success was not significantly affected by density or sex ratio, although variability in male mating success was higher at low density. This could indicate that mating success of B. tryoni can be reduced when local group density is low owing to decreased frequency in encounters between males and females. (ii) Mass-reared males exhibit aberrant mating behaviour, but this does not reduce mating success. Strong artificial selection in mass-rearing facilities may lead to decreased competitiveness of sterile males released in SIT programs as a result of alteration or loss of ecological and behavioural traits required in the field. The effects of domestication and irradiation on the mating behaviour of males of B. tryoni were investigated by caging wild, mass-reared and sterile (mass-reared and gammairradiated) males with wild females. Mating behaviour of mass-reared males was different from that of wild males, but behaviour of wild and sterile males was similar. Mass-reared males were found to engage in mounting of other males much more frequently than wild and sterile males, and began calling significantly earlier before darkness. Male calling did not appear to be associated with female choice of mating partners, although this does not exclude the possibility that calling is a cue used by females to discriminate between mating partners. Conditions used to domesticate and rear large quantities of B. tryoni for SIT may select for an alternative male mating strategy, with mass-reared males calling earlier and exercising less discrimination between potential mating partners. Despite differences in behaviour of wild, mass-reared and sterile males, frequency of successful copulations and mating success were similar. (iii) Pheromone-calling by males was increased in larger aggregations but this did not result in significantly more female visits. Finally, large laboratory cages with artificial leks were used to investigate the importance in B. tryoni of male group size for female visitation at lek sites and initiation of male pheromone-calling. Calling propensity of male B. tryoni was increased by the presence of conspecific males. Females visited the largest lek more frequently than single males, but there was no correlation between lek size and female visitation. Female B. tryoni had a limited capacity to perceive a difference between the number of calling males; female visitation at leks was only weakly associated with male calling, suggesting that lek size and the number of pheromone-calling males may not be the only factor important in locating mates in B. tryoni. The weak, but positive correlation between male calling and female visitation may indicate that passive attraction maintains lek-mating in B. tryoni. Further studies are essential on mating behaviour of B. tryoni, including identification of male mating aggregations in the field, measurement of habitat variables associated with male aggregations, the influence of density on wild B. tryoni mating success, and the role of pheromone-calling, in order to optimise use of SIT for control of this pest.