title: Revisiting Elton's copepods: lake construction has altered the distribution and composition of calanoid copepods in the British Isles

authors: Duggan, Ian C.

subjects: Science & Technology

abstract: It is now widely accepted that the construction of new lakes, ponds and reservoirs facilitates the invasion of non-indigenous aquatic species, due largely to low biotic resistance from native communities. The role played by constructed waters appears to be a particularly frequent feature of zooplankton invasions. Charles Elton, in his classic 1927 book “Animal Ecology”, noted that the estuarine calanoid copepod Eurytemora velox had invaded constructed inland waters in Britain and highlighted the lack of a key species, Eudiaptomus gracilis, in allowing its establishment. At the time, Elton’s observations were dismissed and his findings largely consigned to obscurity. Using occurrence records gathered since this time and current knowledge of calanoid copepod ecology and invasion biology, we re-examined the distributions of three species of freshwater calanoid copepods in the British Isles to: 1) determine the legacy of lake and pond construction on their distributions, and 2) reassess the conclusions made by Elton in light of this knowledge. The lack of natural lakes in the south and east of England, and the subsequent widespread development of new lakes and ponds, has altered calanoid copepod distributions. The common E. gracilis occurs frequently in the north and west of the British Isles in natural lakes, and is found in the south and east in constructed waters. The estuarine E. velox was found only in 3 natural freshwater sites, all in close proximity to the coast, but has been recorded in 23 constructed sites, many of these well inland. Elton noted a general lack of co-existence between E. velox and E. gracilis, with the relatively slow establishment rates of E. gracilis thought key in allowing the estuarine species to invade. However, subsequent collections suggest long-term cooccurrence of these species at some sites. We suggest that E. velox has now successfully invaded freshwaters in the British Isles. Eudiaptomus vulgaris is not known from natural lakes, but has been recorded in several constructed waters, and appears to have invaded Britain facilitated by lake construction. Current knowledge supports Elton’s contention that constructed waters are more readily invaded than natural waters, and that biotic resistance due to the presence of key species is important. While some specific criticisms of Elton’s ideas were valid, we argue that Elton’s concepts regarding constructed waters and invasions were in many ways correct and prescient of current understanding.

text: Revisiting Elton's copepods: lake construction has altered the distribution and composition of calanoid copepods in the British Isles It is now widely accepted that the construction of new lakes, ponds and reservoirs facilitates the invasion of non-indigenous aquatic species, due largely to low biotic resistance from native communities. The role played by constructed waters appears to be a particularly frequent feature of zooplankton invasions. Charles Elton, in his classic 1927 book “Animal Ecology”, noted that the estuarine calanoid copepod Eurytemora velox had invaded constructed inland waters in Britain and highlighted the lack of a key species, Eudiaptomus gracilis, in allowing its establishment. At the time, Elton’s observations were dismissed and his findings largely consigned to obscurity. Using occurrence records gathered since this time and current knowledge of calanoid copepod ecology and invasion biology, we re-examined the distributions of three species of freshwater calanoid copepods in the British Isles to: 1) determine the legacy of lake and pond construction on their distributions, and 2) reassess the conclusions made by Elton in light of this knowledge. The lack of natural lakes in the south and east of England, and the subsequent widespread development of new lakes and ponds, has altered calanoid copepod distributions. The common E. gracilis occurs frequently in the north and west of the British Isles in natural lakes, and is found in the south and east in constructed waters. The estuarine E. velox was found only in 3 natural freshwater sites, all in close proximity to the coast, but has been recorded in 23 constructed sites, many of these well inland. Elton noted a general lack of co-existence between E. velox and E. gracilis, with the relatively slow establishment rates of E. gracilis thought key in allowing the estuarine species to invade. However, subsequent collections suggest long-term cooccurrence of these species at some sites. We suggest that E. velox has now successfully invaded freshwaters in the British Isles. Eudiaptomus vulgaris is not known from natural lakes, but has been recorded in several constructed waters, and appears to have invaded Britain facilitated by lake construction. Current knowledge supports Elton’s contention that constructed waters are more readily invaded than natural waters, and that biotic resistance due to the presence of key species is important. While some specific criticisms of Elton’s ideas were valid, we argue that Elton’s concepts regarding constructed waters and invasions were in many ways correct and prescient of current understanding.

year: 2017

title: Restriction in Program Algebra

authors: Jackson, Marcel

subjects: Science & Technology

abstract: We provide complete classifications of algebras of partial maps for a significant swathe of combinations of operations not previously classified. Our focus is the many subsidiary operations that arise in recent considerations of the ‘override’ and ‘update’ operations arising in specification languages. These other operations turn out to have an older pedigree: domain restriction, set subtraction and intersection. All signatures considered include domain restriction, at least as a term. Combinations of the operations are classified and given complete axiomatizations with and without the presence of functional composition. Each classification is achieved by way of providing a concrete representation of the corresponding abstract algebras as partial maps acting on special kinds of filters determined with respect to various induced orders. In contrast to many negative results in the broader area, all of the considered combinations lead to finite axiomatizations.

text: Restriction in Program Algebra We provide complete classifications of algebras of partial maps for a significant swathe of combinations of operations not previously classified. Our focus is the many subsidiary operations that arise in recent considerations of the ‘override’ and ‘update’ operations arising in specification languages. These other operations turn out to have an older pedigree: domain restriction, set subtraction and intersection. All signatures considered include domain restriction, at least as a term. Combinations of the operations are classified and given complete axiomatizations with and without the presence of functional composition. Each classification is achieved by way of providing a concrete representation of the corresponding abstract algebras as partial maps acting on special kinds of filters determined with respect to various induced orders. In contrast to many negative results in the broader area, all of the considered combinations lead to finite axiomatizations.

year: 2022-07-19

title: Possibilities of transformation: discourses of difference in organisational communication

authors: Jones, Deborah Helen

abstract: In this thesis I set out to create an interdisciplinary location from which to address the relationship between gender and communication in an organisational context. I draw on feminist and post-structuralist theory to ask the question: How is ‘difference’ constructed in organisational communication? I use the term ‘difference’ here to indicate that I am interested in how ‘gender’ works in relationship with other kinds of difference, especially in relation to ethnic difference.

My thesis is intended as a contribution to feminist communication theory, and specifically, to the emerging field of feminist organisational communication. Because of the approach I take to ‘communication’, this project addresses broad issues of identity, agency and discourse in organisations. In this sense, I also see the thesis as a contribution to organisational studies, and particularly to the study of organisational discourse, which opens up new relationships between ‘organisation’ and ‘communication’. Interdisciplinarity itself is a key issue in my thesis, as I set out to create connections between disciplinary fields in the service of contesting them, rather than seeking to create new boundaries. A second key focus is the development of theoretical sophistication in the field of gender and communication. I draw on feminist/post-structuralist theory, especially feminist readings of Michel Foucault’s work to generate this development. My third key focus is the issue of agency, which I see as central to theorising organisational transformation, and also as central to re-thinking communication theory.

My writing strategies demonstrate my commitments to reflexivity in developing feminist/post-structuralist research epistemologies, and I experiment with ways of paying attention to issues of authority throughout the thesis. This thesis is divided into two main parts. In Chapters 2 to 6, I set up a theoretical framework for feminist/post-structuralist accounts of gender and ethnicity, and weave this theory through the literatures of ‘gender and communication’, ‘cross-cultural communication’, and ‘organisational communication’. I set out to produce an ‘autocritique’, an opportunity to draw on developments in post-structuralist theory to think differently about feminist ‘organisational communication’, putting it within a broader framework of ‘difference’.

In the second part of the thesis, Chapters 7 to 12, I put issues generated by this theoretical framework in a specific organisational context, asking: How are gender and ethnic differences constructed in the discourses of Equal Employment Opportunities (EEO) and Biculturalism in New Zealand government organisations? Chapters 7 and 8 introduce my field studies methodology and research subjects, and provide background narratives which frame the historical and cultural context in which they were carried out. In Chapters 9 to 12 I carry out a discourse analysis of interviews with EEO and Biculturalism practitioners, and also analyse published and unpublished documents associated with ‘difference’ in employment policies. These accounts of field studies are intended as a series of experiments with theorising ‘organisational communication’ in different ways. I complete the thesis with a ‘Review’ (Chapter 13) in which I reflect on key theoretical threads, and on further questions that emerged during the project.

text: Possibilities of transformation: discourses of difference in organisational communication In this thesis I set out to create an interdisciplinary location from which to address the relationship between gender and communication in an organisational context. I draw on feminist and post-structuralist theory to ask the question: How is ‘difference’ constructed in organisational communication? I use the term ‘difference’ here to indicate that I am interested in how ‘gender’ works in relationship with other kinds of difference, especially in relation to ethnic difference.

My thesis is intended as a contribution to feminist communication theory, and specifically, to the emerging field of feminist organisational communication. Because of the approach I take to ‘communication’, this project addresses broad issues of identity, agency and discourse in organisations. In this sense, I also see the thesis as a contribution to organisational studies, and particularly to the study of organisational discourse, which opens up new relationships between ‘organisation’ and ‘communication’. Interdisciplinarity itself is a key issue in my thesis, as I set out to create connections between disciplinary fields in the service of contesting them, rather than seeking to create new boundaries. A second key focus is the development of theoretical sophistication in the field of gender and communication. I draw on feminist/post-structuralist theory, especially feminist readings of Michel Foucault’s work to generate this development. My third key focus is the issue of agency, which I see as central to theorising organisational transformation, and also as central to re-thinking communication theory.

My writing strategies demonstrate my commitments to reflexivity in developing feminist/post-structuralist research epistemologies, and I experiment with ways of paying attention to issues of authority throughout the thesis. This thesis is divided into two main parts. In Chapters 2 to 6, I set up a theoretical framework for feminist/post-structuralist accounts of gender and ethnicity, and weave this theory through the literatures of ‘gender and communication’, ‘cross-cultural communication’, and ‘organisational communication’. I set out to produce an ‘autocritique’, an opportunity to draw on developments in post-structuralist theory to think differently about feminist ‘organisational communication’, putting it within a broader framework of ‘difference’.

In the second part of the thesis, Chapters 7 to 12, I put issues generated by this theoretical framework in a specific organisational context, asking: How are gender and ethnic differences constructed in the discourses of Equal Employment Opportunities (EEO) and Biculturalism in New Zealand government organisations? Chapters 7 and 8 introduce my field studies methodology and research subjects, and provide background narratives which frame the historical and cultural context in which they were carried out. In Chapters 9 to 12 I carry out a discourse analysis of interviews with EEO and Biculturalism practitioners, and also analyse published and unpublished documents associated with ‘difference’ in employment policies. These accounts of field studies are intended as a series of experiments with theorising ‘organisational communication’ in different ways. I complete the thesis with a ‘Review’ (Chapter 13) in which I reflect on key theoretical threads, and on further questions that emerged during the project.

year: 1998