title: The role of thermal tolerance in biological invasion

authors: Wilde, Margot

abstract: Biological invasion and climate change are among the greatest threats to biodiversity currently. Several factors influence what makes a successful invasive species. Among these is the thermal tolerance of the invasive species. An organism’s thermal physiology underpins many aspects of its life, including the habitats in which it can survive, its reproduction and its development. Climate change is increasing global average temperatures at an unprecedented pace, which is increasing thermal stress on virtually all life around the world. These effects are particularly pronounced in ectotherms, which are reliant on environmental temperature to set their body temperature and drive their metabolism. Insects comprise a significant proportion of globally important invasive species. As well as being ectothermic, they have a complex life cycle with a number of developmental stages, all of which may be influenced by environmental temperatures. Invasive species can often tolerate or adapt to a broad range of environmental conditions. They may therefore be expected to have a broader thermal tolerance than their native counterparts, and than other invasives that have a narrower invaded range.  

This research used a blowfly model to investigate how thermal tolerance differed across temperatures, using a static temperature assay to measure thermal knockdown time. Key foci included the effects of both developmental heat acclimation and adult heat tolerance on thermal performance.  In Chapter 2, variation in adult heat tolerance was assessed across three temperatures (41℃, 42℃, 43℃) in five blowfly species invasive to New Zealand. I found that the two more globally invasive species in the study exhibited higher heat tolerance than the three less invasive Calliphora species, whose native ranges are generally more temperate. In Chapter 3, the effect of developmental temperature on adult knockdown time in a single species (Calliphora stygia) was assessed. I showed that C. stygia reared at the lowest temperature (18℃) had the highest knockdown time and the smallest body size, while those reared at 26℃ 1 exhibited  the shortest knockdown time and an intermediate body size, with those reared at 22℃ being the largest.   

Collectively, my results indicate that adult heat tolerance varies between invasive blowfly species, but that developmental acclimation temperature may not have a significant effect on adult heat tolerance. Given the increasing global temperatures seen with climate change, the effects of invasive species are likely to increase, with some species likely to do better than others in a warming world. Thermal performance will undoubtedly play a role in filtering out the ‘winners’ and ‘losers’, therefore further research into both heat and cold tolerance in both laboratory and field settings are crucial.

text: The role of thermal tolerance in biological invasion Biological invasion and climate change are among the greatest threats to biodiversity currently. Several factors influence what makes a successful invasive species. Among these is the thermal tolerance of the invasive species. An organism’s thermal physiology underpins many aspects of its life, including the habitats in which it can survive, its reproduction and its development. Climate change is increasing global average temperatures at an unprecedented pace, which is increasing thermal stress on virtually all life around the world. These effects are particularly pronounced in ectotherms, which are reliant on environmental temperature to set their body temperature and drive their metabolism. Insects comprise a significant proportion of globally important invasive species. As well as being ectothermic, they have a complex life cycle with a number of developmental stages, all of which may be influenced by environmental temperatures. Invasive species can often tolerate or adapt to a broad range of environmental conditions. They may therefore be expected to have a broader thermal tolerance than their native counterparts, and than other invasives that have a narrower invaded range.  

This research used a blowfly model to investigate how thermal tolerance differed across temperatures, using a static temperature assay to measure thermal knockdown time. Key foci included the effects of both developmental heat acclimation and adult heat tolerance on thermal performance.  In Chapter 2, variation in adult heat tolerance was assessed across three temperatures (41℃, 42℃, 43℃) in five blowfly species invasive to New Zealand. I found that the two more globally invasive species in the study exhibited higher heat tolerance than the three less invasive Calliphora species, whose native ranges are generally more temperate. In Chapter 3, the effect of developmental temperature on adult knockdown time in a single species (Calliphora stygia) was assessed. I showed that C. stygia reared at the lowest temperature (18℃) had the highest knockdown time and the smallest body size, while those reared at 26℃ 1 exhibited  the shortest knockdown time and an intermediate body size, with those reared at 22℃ being the largest.   

Collectively, my results indicate that adult heat tolerance varies between invasive blowfly species, but that developmental acclimation temperature may not have a significant effect on adult heat tolerance. Given the increasing global temperatures seen with climate change, the effects of invasive species are likely to increase, with some species likely to do better than others in a warming world. Thermal performance will undoubtedly play a role in filtering out the ‘winners’ and ‘losers’, therefore further research into both heat and cold tolerance in both laboratory and field settings are crucial.

year: 2025

title: Unsteady free surface flow induced by a line sink in a fluid of finite depth

authors: Stokes, Tim E.

abstract: The unsteady withdrawal of fluid from a reservoir of finite depth with a free surface through a line sink is considered. A numerical method is used to investigate the evolution of a free surface in several different geometric and initial configurations, and it is shown that there are some critical flow parameters at which the flow changes its nature. The existence of steady states is also considered. Results both with and without surface tension are included and placed in context with previous work. Inclusion of surface tension reveals that solutions either evolve to a steady state or drawdown. As the sink is moved off the base, the behaviour becomes consistent with flows in a fluid of infinite depth, and consequently flows can be classified as either “shallow” or “deep” depending on their drawdown behaviour.

text: Unsteady free surface flow induced by a line sink in a fluid of finite depth The unsteady withdrawal of fluid from a reservoir of finite depth with a free surface through a line sink is considered. A numerical method is used to investigate the evolution of a free surface in several different geometric and initial configurations, and it is shown that there are some critical flow parameters at which the flow changes its nature. The existence of steady states is also considered. Results both with and without surface tension are included and placed in context with previous work. Inclusion of surface tension reveals that solutions either evolve to a steady state or drawdown. As the sink is moved off the base, the behaviour becomes consistent with flows in a fluid of infinite depth, and consequently flows can be classified as either “shallow” or “deep” depending on their drawdown behaviour.

year: 2008

title: For staff at the Eastern Institute of Technology, is Ōtātara a placeless geography? Or a geography of significance?

authors: Passey, Emma

subjects: Ōtātara

abstract: This thesis explores the experience of place for a group of tertiary employees in a regional area of New Zealand. Staff based at EIT Hawke’s Bay in Taradale, Napier can see the Ōtātara Pā Reserve from several vantage points on campus, and often visit because of its immediate proximity. Originally, joined and now adjacent, the cultural significance of this land for Māori over some centuries prior to Pākehā settlement, is still being uncovered. Through a series of interviews, the historical significance of this place is joined with the experiences of staff in being in this space. A range of meanings including belonging, attachment and sense of location were described by participants, showing the development over time of threads of connection for themselves, family, community and also staff members.

Ideas in the literature of place were considered including attachment to meaningful locations and landscape. A particular interest in the thesis was bringing this more general literature into focus for a New Zealand place, which has substantial Māori history connections including for participants of both Māori and Pākehā backgrounds. Several methodological issues were discussed within a series of interviews including cultural appropriateness and representation. The researchers transition from an English cultural upbringing, to developing and extending indigenous landscape knowledge, illustrates the changing recognition and involvement in an increasingly bi-cultural New Zealand, and demonstrates the implications of this in understanding place attachment.

Findings from this research were organised in three main chapters. The first, recounted historical material about Ōtātara, Māori and Pākehā times, exploring ideas of place and belonging. It also provided a natural anchor for the second and third chapters, which reported the findings of EIT staff enjoying being within, and feeling the presence of that history. Several themes emerged and were summarised as embodied landscape experiences, and the intriguing dimensions of social relationships and place for these tertiary staff.
Place is important across the social sciences as it is for other disciplines. It evokes on the one hand aspirations and ideals of an aesthetic and spiritual nature but at the same time, reminds human beings of their literal and biological being in time and space. The present study has contributed to this wider narrative by looking at one example and in one national bi-cultural setting.

The question posed at the start of the thesis considered whether EIT staff view Ōtātara as a place of significance or a geography which does not matter. The historical connections and physical closeness between EIT and Ōtātara, mean that the Institution and the landscape are inextricably linked. People are equally bonded to this place through culture and lived experiences. Often unconscious or incidental associations are handed down through the generations, within the organisation and throughout the wider community.
How we now occupy this place in a modern world, how we share the (hi)stories and become authors of new ones, will have a profound influence on the ways that staff continue to connect and develop feelings of belonging. Related to this, an idea about an institutional-wide hīkoi around the boundaries of the campus and Ōtātara is offered as an addendum. Our responsibility as educators is to signal to future generations that this is a landscape of significance ensuring that Ōtātara continues to be acknowledged as a taonga for EIT employees, and that it is nurtured in the same way as it nurtures us.

text: For staff at the Eastern Institute of Technology, is Ōtātara a placeless geography? Or a geography of significance? This thesis explores the experience of place for a group of tertiary employees in a regional area of New Zealand. Staff based at EIT Hawke’s Bay in Taradale, Napier can see the Ōtātara Pā Reserve from several vantage points on campus, and often visit because of its immediate proximity. Originally, joined and now adjacent, the cultural significance of this land for Māori over some centuries prior to Pākehā settlement, is still being uncovered. Through a series of interviews, the historical significance of this place is joined with the experiences of staff in being in this space. A range of meanings including belonging, attachment and sense of location were described by participants, showing the development over time of threads of connection for themselves, family, community and also staff members.

Ideas in the literature of place were considered including attachment to meaningful locations and landscape. A particular interest in the thesis was bringing this more general literature into focus for a New Zealand place, which has substantial Māori history connections including for participants of both Māori and Pākehā backgrounds. Several methodological issues were discussed within a series of interviews including cultural appropriateness and representation. The researchers transition from an English cultural upbringing, to developing and extending indigenous landscape knowledge, illustrates the changing recognition and involvement in an increasingly bi-cultural New Zealand, and demonstrates the implications of this in understanding place attachment.

Findings from this research were organised in three main chapters. The first, recounted historical material about Ōtātara, Māori and Pākehā times, exploring ideas of place and belonging. It also provided a natural anchor for the second and third chapters, which reported the findings of EIT staff enjoying being within, and feeling the presence of that history. Several themes emerged and were summarised as embodied landscape experiences, and the intriguing dimensions of social relationships and place for these tertiary staff.
Place is important across the social sciences as it is for other disciplines. It evokes on the one hand aspirations and ideals of an aesthetic and spiritual nature but at the same time, reminds human beings of their literal and biological being in time and space. The present study has contributed to this wider narrative by looking at one example and in one national bi-cultural setting.

The question posed at the start of the thesis considered whether EIT staff view Ōtātara as a place of significance or a geography which does not matter. The historical connections and physical closeness between EIT and Ōtātara, mean that the Institution and the landscape are inextricably linked. People are equally bonded to this place through culture and lived experiences. Often unconscious or incidental associations are handed down through the generations, within the organisation and throughout the wider community.
How we now occupy this place in a modern world, how we share the (hi)stories and become authors of new ones, will have a profound influence on the ways that staff continue to connect and develop feelings of belonging. Related to this, an idea about an institutional-wide hīkoi around the boundaries of the campus and Ōtātara is offered as an addendum. Our responsibility as educators is to signal to future generations that this is a landscape of significance ensuring that Ōtātara continues to be acknowledged as a taonga for EIT employees, and that it is nurtured in the same way as it nurtures us.

year: 2021