A lek-breeding cichlid fish Pseudocrenilabrus philander was studied experimentally. Females in choice-chamber experiments showed no active choice for male size and colour, or for other male attributes, but preferred males which courted most actively. In a laboratory lek, the significant determinants of the strongly skewed mating success in males were territory size, side-shake and female chasing frequency. Together these three variables explained 79% of the variation in male mating success, with territory size alone accounting for 75% of the variation and the other two variables each accounting for 2% of the remaining variation. As there was no difference in territory quality in the laboratory lek, territory size became the principal measure of the effect of male-male competition since it was directly related to dominance. Both side-shake and female chasing could be identified as the basic factors influencing female choice, as they had an immediate effect on the display-response mating system of females. Thus, the relative importance of these three variables indicated that sexual selection in this particular lek mating species operated chiefly through the agency of intrasexual competition for dominance. However, both female behaviour and their requirement for a prolonged pre-spawning courtship had the effect of promoting male rivalry and favouring mating with dominant males. Although the intense male competition excluded subordinate males from practising normal courtship behaviour, competitively inferior males might "make the best of a bad situation" by facultatively adopting an alternative sneaking tactic to gain access to females. Spawning intrusions by females to steal freshly-laid eggs also occurred frequently. However, territorial males appeared to be relatively more tolerant of female intruders than male sneakers. Interference during spawning could lead to a longer pre-spawning courtship and even multiple-mating by females. The results of the present study and the behavioural evidence shown by males and females did not support the ʺrunaway selection modelʺ of the mating pattern in terms of sexual selection in leks, but conformed to the rival ʺwar propaganda modelʺ

In this thesis I investigated the genetic basis of several behaviours to answer questions surrounding the evolution and mechanistic basis of behaviour. Firstly, I took a single-gene approach to investigate the influence of fruitless (fru) on the courtship behaviour of Drosophila. fru is an alternatively-spliced transcription factor that is necessary for the production of male sexual behaviours, and has also been implicated in producing species-specific differences in courtship song. I investigated the patterns of selection acting on fru at the sequence level and found that positive selection was restricted to the alternatively spliced exons of fru. From this I hypothesised that the positively selected changes in fru would contribute to species-specific differences in courtship song. To test this I examined how isoform-specific fru loss-of-function mutants influence courtship song, and generated “species-swapped” flies whereby regions of fru that showed evidence for positive selection were transferred from four species of Drosophila, into D. melanogaster. Contrary to prediction, I found flies that lacked isoforms containing positively selected regions did not show any differences in courtship song. Unfortunately “species-swapped” flies were not generated in time to examine phenotypes and neuroanatomy as intended. Next, I examined the genetic basis of cold acclimation in two species of Drosophila using a transcriptomic approach. I found that the genes differentially expressed in response to cold acclimation were largely different in each of the species; however, the biological processes they were involved in were broadly similar. Finally, I investigated the transcriptomic changes associated with parental care in the burying beetle Nicrophorus vespilloides to determine if males and females alter the genes they express when parenting alone versus with a partner. I found that males greatly reduced their transcriptional response when parenting with a partner, suggesting they reduce the care they provide when present with a female.

The invasion of individuals into new habitats can pose a major threat to native species and to biodiversity itself. However, the consequences of invasions for native populations that are not fully reproductively isolated from their invaders are not yet well explored. Here I chose the Trinidadian guppy, Poecilia reticulata, to investigate how different population traits shaped the outcome of Haskins's introduction, a well-documented invasion of Guanapo river guppies into the Turure river. I especially concentrated on the importance of behaviour for invasive success. I investigated if the spread of Guanapo guppies is due to superiority in behaviour, life-history and/or genetics, or if the outcome of this translocation is due to chance. Despite the fact that by today the invasive front has passed the Turure's confluence with the River Quare many kilometres downstream of the introduction site, and the original genotype only survives in small percentages, as was revealed by genetic analysis in this and other studies, no obvious differences between invasive and native populations could be detected in any of the tested behavioural, life-history and genetic traits. When tested for mate choice, neither Guanapo nor Oropuche (Turure) males seemed to be able to distinguish between the population origin of females, but courted and mated at random. At the same time, females did not prefer to school with individuals of the same population over schooling with more distantly related females. The formation of mixed schools after an invasive event is therefore likely. Because female guppies showed a very low willingness to mate, even after having been separated from males for up to six months, sperm transfer through forced copulations will become more important. Taken together, these behaviours could increase the speed of population mixing after an invasion without the need for behavioural superiority of the invasive population. When tested for their schooling abilities, offspring of mixed parentage, in contrast to pure breds, displayed a large amount of variety in the time they spent schooling, a circumstance that can potentially influence survival rates and therefore the direction of gene pool mixing. Guanapo fish did not show reproductive superiority in a mesocosm experiment, where both populations were mixed in different proportions. On the contrary, in two out of three mixed treatments, the amount of Oropuche (Turure) alleles was significantly higher than expected from the proportion of initially stocked fish. The almost complete absence of distinguishable traits other than genetic variation between the examined populations that belong to different drainage systems, opposes the recent split of the guppy into two different species following drainage system borders, as is argued in this thesis. However, the successful invasion of the Turure by Guanapo guppies and the nearly entire disappearance of the original population can be explained in absence of differing population traits. Here I demonstrate how behavioural and genetic interactions between subspecies influence the outcome of biological invasions and second, how factors other than population traits, such as the geographic situation, can produce an advantageous situation for the invader even in the absence of population differences.

Successful captive-breeding and re-introduction programs must have the ability to breed a surplus of genetically suitable animals for release into the wild. Unfortunately, many individuals in captive breeding programs often do not reproduce even when they are apparently healthy and presented with genetically appropriate mates. Mate choice can affect multiple parameters of reproductive sperformance, including mating success, offspring production, survival, and fecundity. We investigated the role of mate preference and personality on the reproductive performance of male and female giant pandas (Ailuropoda melanoleuca) as measured by intromission success and litter production. We conducted these studies on giant pandas at the China Conservation and Research Center for the Giant Panda (Bifengxia, Sichuan, China.) from February-May 2011, 2012, and 2013. In Chapter 2, we compared reproductive performance between individuals mated with preferred and nonpreferred males of the focal female (female preference), the focal male (male preference), and mutual mate choice perspective. There were four types of reproductive pairings in our mutual mate choice analyses: females and males that preferred each other (P-P), females that preferred the male but the male did not prefer the female (P-NP), females that did not prefer the male but the male preferred the female (NP-P), and females and males that did not prefer each other (NP-NP). Pairing giant pandas with a preferred partner increased the probability of intromission success and producing a cub. Of the 25 females mated to a preferred partner, 72% had successful intromission, 64% produced cubs, and 52% reared their own cubs versus 31%, 12%, 12% for females mated to their nonpreferred partner (N = 16). Male giant panda mate preference showed similar results. Of the 24 males that were mated with their preferred females, 75% had successful intromission, 77.8% produced cubs, and 92.9% produced cubs that were maternally reared versus 31%, 60%, 66.7% for males mated with their nonpreferred females (N = 16). There was a statistically significant difference in intromission success and cub production for P-P pairings versus NP-NP pairings. Of the twelve P-P mate dyads 83% had successful intromission, 90% produced cubs, and 88.9% had mothers rear their cubs. Of the four P-NP mate dyads 50% had successful intromission, 50% produced cubs, and 100% had the mother rear their cub. Of the seven NP-P mate dyads 57% had successful intromission, 50% produced cubs, and 100% had the mothers rear their cubs. Of the three NP-NP mate dyads 0% had successful intromission resulting in 0% producing cubs and having mother-rear cubs. In addition, we took into account various life and breeding history factors that may have affected reproductive performance such as birth location, rearing, previous sexual history with the opposite sex and familiarity status directly prior to breeding. Mate pairings that were familiar with each other as measured by successfully producing a cub in the past, had increased intromission success. Females mated to heavier males had more intromissions and produced more cubs than females mated to smaller males. In Chapter 3 and 4, we investigated the effect of personality on reproductive performance measurements. Recently, personality of individual animals has been implicated in the failure or success of captive management and breeding of threatened and endangered species. Measurements of personality included novel object tests (where behaviors of individual giant pandas were scored toward a novel object for one hour) and keeper surveys (where the primary keeper rated giant pandas on 23 adjectives describing personality); both measures significantly correlated with variation in long-term and specific mating dyad reproductive performance. In Chapter 3 we evaluated the effect of personality on long-term reproductive performance. Our results show that for both male and female giant pandas, `fearful' individuals had lower natural mating success and cub production. In addition, `aggressive' female giant pandas had increased natural mating success but decreased cub production. Males did not show these relationships between `aggressive' personality types and reproductive performance. Female giant pandas that were labeled as `aggressive' had higher frequencies of positive mating behaviors but `fearful of conspecifics' females had lower frequencies. Males labeled `fearful of conspecifics' and with high `playful-clever' component scores had a lower frequency of positive mating behaviors. In Chapter 4 we further investigated the effects of personality within a specific mating dyad. Recent studies suggest that mate compatibility within personality types can improve reproductive performance measurements such as mating success, offspring survivorship, and offspring quality. We investigated the effect of personality compatibility on reproductive performance through analyzing mate dyad similarity in personality (similar versus dissimilar), specific personality combinations, and relative personality scores (male scores higher or lower than female scores). The specific personality combinations were: females and males that were both low on the personality component (L_L), females were low but males were high (L_H), females were high but males were low (H_L), and females and males were both high (H_H). Our results suggest that giant pandas appear to be assortatively mating based on aggressive, fearful, and stereotypical-excitable personality traits. Mate dyads that were dissimilar on the stereotypical-excitable component score were more likely to have successful intromission than pairs that were similar. L_H mate dyads on the aggressive and stereotypical-excitable personality traits had increased intromission success and cub production than all other possible personality combinations. L_L on fearfulness had higher intromission success but not higher cub production than all other possible personality combinations. Mate dyads composed of males ranked high on the aggressive component relative to the female resulted in higher reproductive performance and cub production. In captive breeding programs, mates are traditionally selected solely on the basis of genetic parameters to minimize loss of genetic diversity and inbreeding coefficients. Our results suggest that integrating genetic with behavioral measures of preference, breeding history factors, and personality would increase the reproductive output of the giant panda captive-breeding program. We stress the importance of considering husbandry practices to accommodate personality traits and ultimately increase reproductive performance in the captive population while simultaneously maintaining both genetic and behavioral diversity.

Sexual selection can influence the mating system of an organism through multiple mechanisms. These mechanisms result in variation in reproductive success among individuals, and include scramble competition, endurance rivalries, contests, mate choice and cryptic choice, and sperm competition. Understanding the mating system of a species requires the identification of which processes are occurring, and to what degree. In this thesis, I explored the influence of mate choice mechanisms on the mating system of the terrestrial red-legged salamander, Plethodon shermani. I also documented the potential for post-copulatory processes (such as sperm competition and cryptic choice) to influence mating system dynamics. The evolution of mate choice requires (among other factors) variation in the reproductive value of potential mates. This variation is made apparent to choosy individuals through cues. Most animals use multiples cues incorporating many modalities to assess the reproductive quality of potential mates. In Chapter 2, I tested the contribution of two cues (chemical and visual) to mate choice by female P. shermani. I found that a male visual cue ("foot-dancing") increased courtship success. In contrast, delivery of non-volatile pheromones during courtship did not influence courtship success in the laboratory setting, but did affect the duration of one of the courtship stages. In Chapter 4, I identified a tactile cue that was significantly correlated with male reproductive success. Thus, P. shermani females could use at least three modalities to assess the reproductive quality of potential mates. Mate choice can also evolve in males. In Chapter 3, I tested this possibility in P. shermani. I found that males vary the reproductive effort they invest in a particular courtship based on the reproductive value of their partner, indicating male mate choice is occurring. A male invested most when paired with a female with large, well developed ova, and invested less with females that were non-gravid or had small ova. In addition to documenting male mate choice, I showed that the male visual display ("foot-dancing") that affected female mate choice was correlated with male condition, implying foot-dancing may be an honest indicator of male quality. Finally, in Chapter 5, I explored the potential for post-copulatory processes to influence the P. shermani mating system. The opportunity for sperm from multiple males to overlap in the female reproductive tract (i.e., the opportunity for females to mate multiply) is necessary for post-copulatory processes such as cryptic choice and sperm competition. The capacity for long-term sperm storage by females can increase the likelihood that this overlap in sperm from multiple males will occur. I found that females can store viable sperm for at least 9 months and in some cases beyond oviposition. In addition, I documented one female with sperm in her sperm storage organ from a mating that occurred 17 months earlier. Such lengthy sperm storage allows the possibility of sperm from one breeding season to interact with sperm from a subsequent season. Thus, the potential for post-copulatory sexual selection within this salamander system is high. / Graduation date: 2012

Evidence for reduced reproductive success (RS) of wild spawning hatchery-reared fish invites serious consideration with regard to the detrimental effects on subsequent generations of wild populations. Mate choice was evaluated as a potential mechanism contributing to these observed RS differences using a previous pedigree of wild spawning hatchery-reared and wild origin coho salmon (Oncorhynchus kisutch). Genetic variance at immune-relevant genes was used as ametric toexaminematechoice. Twoyears (2005 and2006)of threewild spawning mate pair classes were examined: wild x wild (W x W), hatchery x hatchery (H x H), and wild x hatchery (W x H). We tested for: (1) a departure from random expectations with regard to mate pair allelic diversity at immune-relevant markers, (2) a correlation between immune-relevant gene diversity and mate pair RS, and (3) distinguishable differences between mate choice strategies used by hatchery-reared and wild origin coho. Eight immune-relevant gene-linked microsatellite markers were used to evaluate mate choice; four linked to immune-relevant expressed sequence tags (ESTs) and four linked to the Major Histocompatibility Complex (MHC). We found evidence for non-random mating between 2006 W x H mate pairs at BHMS429,an MHC-linked marker, and at SsalR016TKU,an immune-relevantEST-linked marker, which was identified as a vasodilator-stimulated phosphoprotein. Non-random mating was also evident between 2005 H x H pairs at SsalR015TKU,an immune-relevantEST-linkedmarker,thoughno putativegene was identified. All other pair classes did not display a significant mate choice signature. We found a significant correlation between mate pair RS and immune gene diversity among 2005 and 2006 W x W mate pairs as well as 2006 W x H mate pairs. Notably, H x H mate pair RS was not correlated to immune gene diversity in either year. Results suggest that mate choice and genetic compatibility may influence fitness of wild spawning coho. / Graduation date: 2013