The wide, unstable, braided riverbeds of the eastern South Island, New Zealand, have been inhabited by a diverse avifauna. Several species including the wrybill breed only on these rivers. Use is restricted mainly to the breeding season from September to December, so this was the critical study period. Previous, behaviourally oriented studies have occurred mainly in the high country catchments where habitat modification is slight. However, substantial bird numbers also occur on lowland riverbeds. These areas are subject to existing or planned water developments which may have negative impacts on the conservation of these habitats and bird species. The principal goal of this study was to add to the information necessary to conserve lowland riverbed habitat within multiple use planning strategies. Specific objectives associated with assessing breeding and feeding requirements were therefore hydrologically oriented. Study areas were chosen on the lower Rakaia and lower Ashley rivers. Both are braided but have markedly different flow regimes. The Rakaia is snowfed and has peak flows occurring during the breeding season. The Ashley is primarily rainfed and has a declining breeding season flow regime. Wrybills, black-fronted terns, banded dotterels, South Island pied oystercatchers, and pied stilts breed in these areas. The first two of these were selected as indicator species. It was assumed that because of their restricted habitat needs, flow requirements recommended to meet their needs would also meet those of most other species. Banded dotterels were also studied because of their close taxonomic relationship and overlapping distribution with wrybills. South Island pied oystercatchers and pied stilts were chosen to check the validity of the approach. Breeding, nest site requirements, microhabitat preferences for foraging, diets, home ranges and food supply were studied. Wrybill time-budgets were examined, and the incremental approach to impact assessment was applied to wrybill foraging needs. Breeding success for all species was dependent on the flow regime. In 1982 wrybill fledging success was moderate on the Rakaia, whereas in 1983 it was very low. Conversely, in both years fledging success was very high on the Ashley. This variability resulted from serious flooding on the Rakaia in 1983 which effected all species. Wrybills have nest site characteristics most closely approximating a habitat specialist, while the other species should be considered habitat generalists. Nests are generally close to water, near minor braids, and on non-vegetated shingle substrates. On average there is a higher chance of nests being flooded on the Rakaia than on the Ashley where predation is more likely to reduce nesting success. Vegetation encroachment threatens nest site provision and floods are presently the only natural regular of exotic plants such as lupin. Banded dotterel home ranges were significantly smaller than wrybills, and on an intra-specific basis were smaller on the Ashley. A correlation existed between home range size and habitat quality, so that small wrybill home ranges were dominated by the occurrence of productive minor braids, and larger ones by less productive major channels. Time-budgets provided further insights into the influence of hydrological factors on wrybill ecology. Wrybill time-budgets appear to be inflexible because a high proportion of time is devoted to foraging, with relatively little time available for other activities. Resource depression on the Rakaia in 1983 lessened the chances for wrybills to breed successfully because sufficient food could not be gathered to provide for breeding energy needs. This did not occur on the Ashley River where flows were generally more stable. From a management viewpoint, development strategies which lead to greater flow fluctuations will have a detrimental impact on wrybills. The foraging patterns for all species except black-fronted terns were examined. There was a general preference for aquatic habitats, particularly those associated with minor braids and disconnected pools. Depth and substrate use were studied in detail for wrybills and banded dotterels. Wrybills displayed consistent use patterns between rivers, which reflected specialisation in habitat use. Banded dotterel habitat use varied considerably. Diet was studied by faecal analysis. Both wrybills and banded dotterels fed on invertebrates of aquatic and terrestrial origin. For wrybills it was noticeable that Ephemeroptera larvae did not dominate the diet as had previously been reported for high country catchments. Coleoptera, Hemiptera, and Ephemeroptera were important on the Rakaia with Trichoptera replacing Ephemeroptera larvae on the Ashley. Banded dotterels were more reliant on Coleoptera and Hemiptera on both rivers. Pitfall trapping results showed that terrestrial invertebrate availability was dependent on the proximity of water. Fewer floods on the Ashley led to a more consistent food supply on that river. This helps explain the greater bird density on this river. Severe flooding in 1983 appeared to seriously depress aquatic invertebrate densities on the Rakaia. The incremental approach to impact assessment was applied to wrybill foraging requirements. Depth, substrate, and water velocity preferences were included within a weighted usable area model already developed for fisheries use on the Rakaia River. Over the range of median to low flows studied, weighted usable area increased with declining discharge. A simplified usable width approach was applied to a highly braided section of the Ashley River. Here, usable width declined with falling discharges. This inter-basin difference could be explained with reference to the braiding pattern of each river. The main study objectives were achieved, but the indicator species management approach was of limited value in areas other than nest site requirements. Pied stilts and South Island pied oystercatchers fed at greater depths than wrybills, and often used different microhabitats. However, for foraging, wrybills need appeared adequate indicators of banded dotterel requirements.

Theoretical research has demonstrated that ecological interactions in sympatry or parapatry can generate disruptive selection that in concert with assortative mating can lead to speciation. However, empirical examples are few and restricted to terrestrial and lacustrine systems. New Zealand triplefin fishes (Family Tripterygiidae) are an ideal model system to study speciation in the sea, as they conform to the criteria of an adaptive radiation, being philopatric, speciose and abundant, and having largely sympatric distributions. This thesis investigates two key aspects of the New Zealand triplefin radiation: 1) which ecological traits are under selection?; and 2) which traits are potentially available for the development of assortative mating? Habitat use was identified as a possible key trait for selection and investigated in detail in this thesis. Habitat use of the majority of New Zealand triplefin species was censused quantitatively throughout most of their latitudinal range and analysed using novel statistical methods. Analyses showed that habitat use was highly divergent between species and thus diversification in habitat may have been a major component in the evolution of this clade. The phylogenetic analysis of habitat characters confirmed that there has been rapid evolution in habitat use among species. Habitat selection at settlement was highly species-specific, indicating that interspecific differences in adult habitat use may be the outcome of active habitat choice established at settlement. These species-specific habitat associations showed no evidence for geographic variation in habitat use. Laboratory trials and field observations of the sister-species pair Ruanoho decemdigitatus and R. whero showed that competition was linked with body size, with R. decemdigitatus being the larger and consequently dominant species. The second part of this thesis investigated which traits may have contributed to prezygotic isolation, and thus to assortative mating. Little evidence was found for divergence in breeding season or male colour patterns. However, divergence in habitat affected breeding habitat choice, as triplefins court and mate in the same territory as that occupied year round. This suggests that assortative mating in New Zealand triplefin species could be the by-product of adaptation to habitat resources. Body size affected mate choice and time at first maturity in the Ruanoho sister-species pair, suggesting that size is important in the maintenance of reproductive isolation in these species. Differences in body size may have also lead to assortative mating in other New Zealand triplefin sister-species pairs, as all sister-species pairs differ in maximum body size. The findings of this thesis invoke a strong role for ecologically-based selection in speciation, and support the hypothesis that adaptation to habitat has been a major factor in speciation in this system. / This PhD was funded by the New Zealand Royal Society (Marsden Fund 02-UOA-005 to Kendall Clements), the Tertiary Education Commission (Top Achiever Doctoral Scholarship), and the University of Auckland (University of Auckland Doctoral Scholarship.

Knowledge of the interactions among species and communities is vital for their management and protection. Increasingly, the role of marine protected areas in this regard is being recognised, primarily because of the potential for previously-harvested species to increase in density and biomass, and the linkages among species to be restored. Monitoring and research was conducted within and surrounding two marine reserves on the east coast of the North Island of New Zealand – Te Tapuwae o Rongokako, near Gisborne, and Te Angiangi, south of Napier. The aim was to describe the biological characteristics of spiny lobsters (Jasus edwardsii) in the absence of fishing, and to describe the effects of fishing and protection on lobster populations and the communities of which they are a component. Diver and pot surveys showed that lobsters were significantly more abundant within the reserves than in the surrounding fisheries and that the populations were comprised of a larger proportion of legal-sized individuals. Higher female fecundity within Te Tapuwae o Rongokako Marine Reserve compared with the surrounding fishery was proposed to be primarily a result of increased availability of large males within the reserve. The impact of the fishery on lobsters was also evidenced in the lower tail width to carapace length ratio of the fished population compared to the population within Te Tapuwae o Rongokako Marine Reserve, due to the minimum legal size for Jasus edwardsii in New Zealand being based on tail width. The largest tagging study ever to be conducted in a New Zealand marine reserve showed that sublegal male lobsters within Te Tapuwae o Rongokako Marine Reserve were growing on average faster than the same sized individuals outside the reserve, potentially as a result of the effects of handling and / or size-selective fishing. A decrease in growth rate over time was recorded in male lobsters within the reserve, which coincided with an increase in catch per unit effort and may indicate that density-dependent effects are operating. Distinct seasonal movements of tagged lobsters were recorded, with the vast majority of movements taking place within reefs. Where the boundaries of the reserve crossed reef habitat, significant movement of lobsters across the boundaries occurred. Lobsters within Te Tapuwae o Rongokako Marine Reserve not only exhibited cannibalistic behaviour but foraged during the day, including on intertidal reef platforms at high tide, potentially as a behavioural response to increased competition for food – behaviour not previously reported for this species. Outside the reserve, lobster bait apparently provided an alternative protein source but despite this supplementation of diet, these lobsters were in poorer nutritional condition, as evidenced by their lower body weights relative to carapace length and tail width for both sexes. Lobsters outside the reserve were also significantly more affected by a bacterial infection associated with handling, than lobsters within the reserve. These findings have significant implications for fisheries management and for the design and management of marine protected areas (MPAs). This study demonstrates that many of the biological parameters used in evaluating harvest strategies in the New Zealand lobster fishery may be biased unless collected from populations with a natural size structure, such as may occur within marine protected areas.

Theoretical research has demonstrated that ecological interactions in sympatry or parapatry can generate disruptive selection that in concert with assortative mating can lead to speciation. However, empirical examples are few and restricted to terrestrial and lacustrine systems. New Zealand triplefin fishes (Family Tripterygiidae) are an ideal model system to study speciation in the sea, as they conform to the criteria of an adaptive radiation, being philopatric, speciose and abundant, and having largely sympatric distributions. This thesis investigates two key aspects of the New Zealand triplefin radiation: 1) which ecological traits are under selection?; and 2) which traits are potentially available for the development of assortative mating? Habitat use was identified as a possible key trait for selection and investigated in detail in this thesis. Habitat use of the majority of New Zealand triplefin species was censused quantitatively throughout most of their latitudinal range and analysed using novel statistical methods. Analyses showed that habitat use was highly divergent between species and thus diversification in habitat may have been a major component in the evolution of this clade. The phylogenetic analysis of habitat characters confirmed that there has been rapid evolution in habitat use among species. Habitat selection at settlement was highly species-specific, indicating that interspecific differences in adult habitat use may be the outcome of active habitat choice established at settlement. These species-specific habitat associations showed no evidence for geographic variation in habitat use. Laboratory trials and field observations of the sister-species pair Ruanoho decemdigitatus and R. whero showed that competition was linked with body size, with R. decemdigitatus being the larger and consequently dominant species. The second part of this thesis investigated which traits may have contributed to prezygotic isolation, and thus to assortative mating. Little evidence was found for divergence in breeding season or male colour patterns. However, divergence in habitat affected breeding habitat choice, as triplefins court and mate in the same territory as that occupied year round. This suggests that assortative mating in New Zealand triplefin species could be the by-product of adaptation to habitat resources. Body size affected mate choice and time at first maturity in the Ruanoho sister-species pair, suggesting that size is important in the maintenance of reproductive isolation in these species. Differences in body size may have also lead to assortative mating in other New Zealand triplefin sister-species pairs, as all sister-species pairs differ in maximum body size. The findings of this thesis invoke a strong role for ecologically-based selection in speciation, and support the hypothesis that adaptation to habitat has been a major factor in speciation in this system. / This PhD was funded by the New Zealand Royal Society (Marsden Fund 02-UOA-005 to Kendall Clements), the Tertiary Education Commission (Top Achiever Doctoral Scholarship), and the University of Auckland (University of Auckland Doctoral Scholarship.

Knowledge of the interactions among species and communities is vital for their management and protection. Increasingly, the role of marine protected areas in this regard is being recognised, primarily because of the potential for previously-harvested species to increase in density and biomass, and the linkages among species to be restored. Monitoring and research was conducted within and surrounding two marine reserves on the east coast of the North Island of New Zealand – Te Tapuwae o Rongokako, near Gisborne, and Te Angiangi, south of Napier. The aim was to describe the biological characteristics of spiny lobsters (Jasus edwardsii) in the absence of fishing, and to describe the effects of fishing and protection on lobster populations and the communities of which they are a component. Diver and pot surveys showed that lobsters were significantly more abundant within the reserves than in the surrounding fisheries and that the populations were comprised of a larger proportion of legal-sized individuals. Higher female fecundity within Te Tapuwae o Rongokako Marine Reserve compared with the surrounding fishery was proposed to be primarily a result of increased availability of large males within the reserve. The impact of the fishery on lobsters was also evidenced in the lower tail width to carapace length ratio of the fished population compared to the population within Te Tapuwae o Rongokako Marine Reserve, due to the minimum legal size for Jasus edwardsii in New Zealand being based on tail width. The largest tagging study ever to be conducted in a New Zealand marine reserve showed that sublegal male lobsters within Te Tapuwae o Rongokako Marine Reserve were growing on average faster than the same sized individuals outside the reserve, potentially as a result of the effects of handling and / or size-selective fishing. A decrease in growth rate over time was recorded in male lobsters within the reserve, which coincided with an increase in catch per unit effort and may indicate that density-dependent effects are operating. Distinct seasonal movements of tagged lobsters were recorded, with the vast majority of movements taking place within reefs. Where the boundaries of the reserve crossed reef habitat, significant movement of lobsters across the boundaries occurred. Lobsters within Te Tapuwae o Rongokako Marine Reserve not only exhibited cannibalistic behaviour but foraged during the day, including on intertidal reef platforms at high tide, potentially as a behavioural response to increased competition for food – behaviour not previously reported for this species. Outside the reserve, lobster bait apparently provided an alternative protein source but despite this supplementation of diet, these lobsters were in poorer nutritional condition, as evidenced by their lower body weights relative to carapace length and tail width for both sexes. Lobsters outside the reserve were also significantly more affected by a bacterial infection associated with handling, than lobsters within the reserve. These findings have significant implications for fisheries management and for the design and management of marine protected areas (MPAs). This study demonstrates that many of the biological parameters used in evaluating harvest strategies in the New Zealand lobster fishery may be biased unless collected from populations with a natural size structure, such as may occur within marine protected areas.

The establishment of protected areas (PAs) has been the key national strategy in biodiversity conservation, through preserving the unique wildlife and ecosystems in Indonesia. As well as their status as sites rich in biodiversity, PAs are also important for socio-economic interactions. Hence the management of PAs has been fraught with technical, social and economic problems. To ensure greater local participation and support in tropical forest conservation initiatives, it is vital to understand how local stakeholders perceive them. This research was undertaken in Gorontalo Province by examining the views of local stakeholders through a combination of qualitative interviews and quantitative ranking exercises. The findings revealed that respondents only understood the concept of biodiversity on a general level. Most respondents defined biodiversity in terms of its elements; only a few were able to describe the interactional attributes, by which biodiversity functions within the ecosystems. Their appreciation of forest biodiversity was primarily due to economic and ecological benefits they derive from local forests. Accordingly, respondents ranked the provision of ecological services from the forests as the strongest reason for protecting it. Using Wood et al. (2000) analytical framework to examine the root causes of biodiversity loss, the findings indicated respondents’ familiarity with human-induced forces resulting in the degradation and loss of natural forests, and they understood how these affect local biodiversity, both within and beyond the forest. Some critical disconnections between national policy in forest conservation and the reality of the local use of forest resource became apparent. At the core of these disconnections was an unequal share of benefits of such policy to local stakeholders. They identified extraction of species and physical alteration of the forest ecosystem as direct drivers of forest loss; these were perceived as rooted in poverty, institutional failures in forest management, ignorance of the wider forest functions, and conflict of development policies at the local level. The main reason for biodiversity loss can be summed up as widespread and persistent failure to properly understand, quantify, or value the goods, services, functions and capital value of the natural forests, at both national and local levels. Overall, most respondents held negative attitudes towards protected forests and their positive attitudes towards conservation activities were linked with tangible benefits they enjoy from the forest. A key finding of this study is that the conservation of biodiversity cannot be considered in isolation from broader patterns of natural resource use and the socio-political context in which people carry out their lives. This study suggests that the implementation of the centrally-controlled and preservationist conservation approach in Gorontalo has been ineffective in achieving conservation goals. This is due to the lack of a clear connection between this policy and the reality of local forest users.

Theoretical research has demonstrated that ecological interactions in sympatry or parapatry can generate disruptive selection that in concert with assortative mating can lead to speciation. However, empirical examples are few and restricted to terrestrial and lacustrine systems. New Zealand triplefin fishes (Family Tripterygiidae) are an ideal model system to study speciation in the sea, as they conform to the criteria of an adaptive radiation, being philopatric, speciose and abundant, and having largely sympatric distributions. This thesis investigates two key aspects of the New Zealand triplefin radiation: 1) which ecological traits are under selection?; and 2) which traits are potentially available for the development of assortative mating? Habitat use was identified as a possible key trait for selection and investigated in detail in this thesis. Habitat use of the majority of New Zealand triplefin species was censused quantitatively throughout most of their latitudinal range and analysed using novel statistical methods. Analyses showed that habitat use was highly divergent between species and thus diversification in habitat may have been a major component in the evolution of this clade. The phylogenetic analysis of habitat characters confirmed that there has been rapid evolution in habitat use among species. Habitat selection at settlement was highly species-specific, indicating that interspecific differences in adult habitat use may be the outcome of active habitat choice established at settlement. These species-specific habitat associations showed no evidence for geographic variation in habitat use. Laboratory trials and field observations of the sister-species pair Ruanoho decemdigitatus and R. whero showed that competition was linked with body size, with R. decemdigitatus being the larger and consequently dominant species. The second part of this thesis investigated which traits may have contributed to prezygotic isolation, and thus to assortative mating. Little evidence was found for divergence in breeding season or male colour patterns. However, divergence in habitat affected breeding habitat choice, as triplefins court and mate in the same territory as that occupied year round. This suggests that assortative mating in New Zealand triplefin species could be the by-product of adaptation to habitat resources. Body size affected mate choice and time at first maturity in the Ruanoho sister-species pair, suggesting that size is important in the maintenance of reproductive isolation in these species. Differences in body size may have also lead to assortative mating in other New Zealand triplefin sister-species pairs, as all sister-species pairs differ in maximum body size. The findings of this thesis invoke a strong role for ecologically-based selection in speciation, and support the hypothesis that adaptation to habitat has been a major factor in speciation in this system. / This PhD was funded by the New Zealand Royal Society (Marsden Fund 02-UOA-005 to Kendall Clements), the Tertiary Education Commission (Top Achiever Doctoral Scholarship), and the University of Auckland (University of Auckland Doctoral Scholarship.

The Blue Penguin (Eudyptula minor) is assumed to be declining over much of its range, largely due to introduced predators. Anecdotal evidence suggests that one of the areas of declining population is the West Coast of the South Island. The purpose of this study was to determine the reasons for the assumed decline of blue penguins in South Westland. This was done by studying breeding ecology at several blue penguin colonies to assess the importance of breeding success and adult mortality on the penguin population. Three blue penguin colonies in South Westland, at Five Mile and Three Mile beaches south of Okarito, and at the Wanganui River mouth near Harihari, were monitored throughout the 2008/09 breeding season. During each burrow visit the number of eggs and chicks were recorded as well as the date of laying, hatching or fledging. Five colonies of blue penguin were also monitored in Buller over the same breeding season in a study conducted by the West Coast Blue Penguin Trust, a community trust based on the West Coast. The results of both studies were compared to determine the effect of predator control on breeding parameters, such as breeding success. Of 137 eggs laid in South Westland, 108 chicks survived until fledging, giving an overall breeding success of 78.8%. In Buller, 64 chicks survived to fledging from 101 eggs laid, resulting in an overall breeding success of 63.4%. Breeding success was significantly higher at penguin colonies in South Westland, compared to the Buller colonies. There was no evidence that predator control had an effect on breeding success in South Westland or Buller. The mean number of chicks fledged per pair that produced eggs was 1.55 in South Westland and 1.16 in Buller. The overall proportion of occupied breeding burrows compared to the total number of suitable burrows at the South Westland sites was 73.8% (n = 103). At the Buller sites, only 60.3 % (n = 151) of the total number of burrows was occupied. Road kills are a major threat to blue penguins in Buller due to the proximity of colonies to the state highway. Fortunately, incidences of road death in South Westland are rare and due to the distance from roads, do not pose a significant threat to South Westland blue penguins. Further study of blue penguin colonies in South Westland is needed to learn more about annual variation in breeding productivity and to determine if breeding success is consistently high over an extended time period. If this is the case, then the cause of blue penguin decline on the West Coast is unlikely to be due to problems with breeding as the breeding success during this study is one of the highest recorded for blue penguins. Although there was no apparent effect of predator control on breeding productivity during this study there is evidence from other locations that predators, in particular stoats, have contributed to the decline of blue penguin populations. More research into the impact of predators on penguins over a longer period of time is needed on the West Coast before a change is made to how predators are managed.

Content removed from thesis due to copyright restrictions: Seabrook-Davison, M. N. H., Weihong, J. J. & Brunton, D. H. (2010). "Survey of New Zealand Department of Conservation staff involved in the management and recovery of threatened species." Biological Conservation, 143: 212-219. doi: 10.1016/j.biocon.2009.10.005. Seabrook-Davison, M. N. H., Ji, W. & Brunton, D. H. (in press). "New Zealand lacks comprehensive threatened species legislation -- comparison with legislation in Australia and the USA." Pacific Conservation Biology, 16. / It is only recently that New Zealand wildlife managers have become aware of both the taxonomic range of New Zealand’ indigenous biodiversity and the number of species threatened with extinction. The entire New Zealand archipelago has been described as a biodiversity hotspot; a term with both negative and positive connotations as although its biodiversity is unique and diverse, it has lost three quarters of its primary vegetation and much of its remaining endemic biota is in decline. This thesis evaluated aspects of New Zealand’s approach to the management of biodiversity with an emphasis on methods used in the recovery of threatened species. Possible solutions are presented that New Zealand could investigate to improve the delivery of species recovery. A survey was conducted amongst Department of Conservation (DOC) staff to investigate management tools available to them. Results suggest that inadequate resources, staff shortages and an overwhelming workload have resulted in a failure to achieve comprehensive recovery of threatened species. A review of New Zealand wildlife conservation legislation and a comparison with the USA Endangered Species Act 1973 and Australian Environment Protection and Biodiversity Conservation Act 1999, suggests that a lack of dedicated threatened species legislation is hindering the effective recovery of New Zealand’s threatened species. The thesis concludes that New Zealand has the advantage of a large conservation estate but lacks an integrated national management approach to the conservation of its biodiversity. Considerable improvement of the management and recovery of threatened species can be achieved with the enacting of dedicated threatened species legislation. Keywords: Threatened species, biodiversity, biodiversity hotspot, conservation, management, recovery plans, recovery groups, Department of Conservation, legislation, threat classification system, listing, ecological function, ecosystem services, staff survey, New Zealand

Theoretical research has demonstrated that ecological interactions in sympatry or parapatry can generate disruptive selection that in concert with assortative mating can lead to speciation. However, empirical examples are few and restricted to terrestrial and lacustrine systems. New Zealand triplefin fishes (Family Tripterygiidae) are an ideal model system to study speciation in the sea, as they conform to the criteria of an adaptive radiation, being philopatric, speciose and abundant, and having largely sympatric distributions. This thesis investigates two key aspects of the New Zealand triplefin radiation: 1) which ecological traits are under selection?; and 2) which traits are potentially available for the development of assortative mating? Habitat use was identified as a possible key trait for selection and investigated in detail in this thesis. Habitat use of the majority of New Zealand triplefin species was censused quantitatively throughout most of their latitudinal range and analysed using novel statistical methods. Analyses showed that habitat use was highly divergent between species and thus diversification in habitat may have been a major component in the evolution of this clade. The phylogenetic analysis of habitat characters confirmed that there has been rapid evolution in habitat use among species. Habitat selection at settlement was highly species-specific, indicating that interspecific differences in adult habitat use may be the outcome of active habitat choice established at settlement. These species-specific habitat associations showed no evidence for geographic variation in habitat use. Laboratory trials and field observations of the sister-species pair Ruanoho decemdigitatus and R. whero showed that competition was linked with body size, with R. decemdigitatus being the larger and consequently dominant species. The second part of this thesis investigated which traits may have contributed to prezygotic isolation, and thus to assortative mating. Little evidence was found for divergence in breeding season or male colour patterns. However, divergence in habitat affected breeding habitat choice, as triplefins court and mate in the same territory as that occupied year round. This suggests that assortative mating in New Zealand triplefin species could be the by-product of adaptation to habitat resources. Body size affected mate choice and time at first maturity in the Ruanoho sister-species pair, suggesting that size is important in the maintenance of reproductive isolation in these species. Differences in body size may have also lead to assortative mating in other New Zealand triplefin sister-species pairs, as all sister-species pairs differ in maximum body size. The findings of this thesis invoke a strong role for ecologically-based selection in speciation, and support the hypothesis that adaptation to habitat has been a major factor in speciation in this system. / This PhD was funded by the New Zealand Royal Society (Marsden Fund 02-UOA-005 to Kendall Clements), the Tertiary Education Commission (Top Achiever Doctoral Scholarship), and the University of Auckland (University of Auckland Doctoral Scholarship.