title: Interactions between freshwater mussels and non-native species

authors: Moore, Thomas Peter

subjects: conservation

abstract: Biological invasions contribute to ecosystem change globally, with a disproportionate and intensified impact in freshwaters. This process is exacerbated in modified systems such as hydrogeneration reservoirs that promote favourable conditions for non-native species proliferation. One of the major threats from non-native species is the introduction of novel interactions that may be particularly impactful on species in affiliate (dependent) relationships and that have narrow habitat requirements during early life-stages. Freshwater mussels (Bivalvia: Unionida) are sessile benthic organisms in affiliate relationships with host fish on which they complete their ectoparasitic life-stage. Attached larvae (glochidia) transform on suitable fish hosts before dropping off as juveniles on surficial sediments. Significant disruption to such interactions may lead to local extinction if affiliate partners are unable to be replaced (i.e., by non-native fish) or the availability of critical life-supporting habitats is reduced (e.g., by non-native macrophytes). Non-native species may play a role in reducing recruitment leading to the adult-skewed mussel population size-structures commonly observed. Accordingly, this thesis contributes knowledge of the interactions between unionid mussels and non-native species in modified freshwater ecosystems, and provides information to assist in species and reservoir management for unionid mussel conservation.

The thesis outputs are presented as chapters that have been published in, submitted to, or prepared for scientific journals. A general introduction (Chapter 1) provides context for a global meta-analysis of non-native species and unionid mussel interactions that highlighted non-native fish and macrophytes as potential threats to New Zealand mussels (Chapter 2). Accordingly, a laboratory experiment on three non-native fish (brown bullhead catfish, Ameiurus nebulosus; rudd, Scardinius erythrophthalmus; and goldfish, Carassius auratus) found mussel glochidia were not transformed in ecologically viable numbers compared to a known host fish (Gobiomorphus cotidianus) for a New Zealand unionid (Echyridella menziesii; Chapter 3). This finding suggested that shifts towards fish communities dominated by non-native species have potential to disrupt the obligate glochidial life-stage of unionid mussels.

Dense beds of non-native macrophytes (Ceratophyllum demersum and Egeria densa) were found to produce adverse anoxic and hypoxic conditions potentially fatal to mussels in a field survey of Karāpiro, the most downstream in the Waikato River hydrogeneration reservoir chain (Chapter 4). Here, adverse conditions at the sediment-water interface in littoral zones were mediated by reservoir management of water-level and water-flow, and by macrophyte control via herbicide application in the lower-lacustrine section. A subsequent field survey extended the Chapter 4 results to show that effects of non-native macrophytes at the sediment-water interface depended on macrophyte species and overarching hydrology, whereby adult-skewed mussel population size-structures were present in the lower-lacustrine of Karāpiro but not in the upper-riverine section where recruitment was occurring (Chapter 5).

The final chapter combined previous findings to show how various hypothetical scenarios of fish and macrophyte invasions could operate separately (non-native fish only) or in combination to disrupt E. menziesii recruitment (Chapter 6). This hypothetical analysis highlighted the importance of considering the threats of both non-native fish and macrophytes, which operate primarily on different stages of the unionid life-cycle, in freshwater mussel conservation and management. Due to the long life-span of unionids, recognition of non-native species impacts contributing to adult-skewed mussel population size-structures may provide an opportunity to restore disrupted mechanisms supporting their recruitment before local extinction occurs. Globalisation and energy demand facilitate continued biotic homogenisation and loss of associated ecosystem services. In this context, the role of management in preventing and mitigating the impacts of biological invasions on sensitive species with affiliate relationships will become increasingly important in freshwater ecosystems in the future.

text: Interactions between freshwater mussels and non-native species Biological invasions contribute to ecosystem change globally, with a disproportionate and intensified impact in freshwaters. This process is exacerbated in modified systems such as hydrogeneration reservoirs that promote favourable conditions for non-native species proliferation. One of the major threats from non-native species is the introduction of novel interactions that may be particularly impactful on species in affiliate (dependent) relationships and that have narrow habitat requirements during early life-stages. Freshwater mussels (Bivalvia: Unionida) are sessile benthic organisms in affiliate relationships with host fish on which they complete their ectoparasitic life-stage. Attached larvae (glochidia) transform on suitable fish hosts before dropping off as juveniles on surficial sediments. Significant disruption to such interactions may lead to local extinction if affiliate partners are unable to be replaced (i.e., by non-native fish) or the availability of critical life-supporting habitats is reduced (e.g., by non-native macrophytes). Non-native species may play a role in reducing recruitment leading to the adult-skewed mussel population size-structures commonly observed. Accordingly, this thesis contributes knowledge of the interactions between unionid mussels and non-native species in modified freshwater ecosystems, and provides information to assist in species and reservoir management for unionid mussel conservation.

The thesis outputs are presented as chapters that have been published in, submitted to, or prepared for scientific journals. A general introduction (Chapter 1) provides context for a global meta-analysis of non-native species and unionid mussel interactions that highlighted non-native fish and macrophytes as potential threats to New Zealand mussels (Chapter 2). Accordingly, a laboratory experiment on three non-native fish (brown bullhead catfish, Ameiurus nebulosus; rudd, Scardinius erythrophthalmus; and goldfish, Carassius auratus) found mussel glochidia were not transformed in ecologically viable numbers compared to a known host fish (Gobiomorphus cotidianus) for a New Zealand unionid (Echyridella menziesii; Chapter 3). This finding suggested that shifts towards fish communities dominated by non-native species have potential to disrupt the obligate glochidial life-stage of unionid mussels.

Dense beds of non-native macrophytes (Ceratophyllum demersum and Egeria densa) were found to produce adverse anoxic and hypoxic conditions potentially fatal to mussels in a field survey of Karāpiro, the most downstream in the Waikato River hydrogeneration reservoir chain (Chapter 4). Here, adverse conditions at the sediment-water interface in littoral zones were mediated by reservoir management of water-level and water-flow, and by macrophyte control via herbicide application in the lower-lacustrine section. A subsequent field survey extended the Chapter 4 results to show that effects of non-native macrophytes at the sediment-water interface depended on macrophyte species and overarching hydrology, whereby adult-skewed mussel population size-structures were present in the lower-lacustrine of Karāpiro but not in the upper-riverine section where recruitment was occurring (Chapter 5).

The final chapter combined previous findings to show how various hypothetical scenarios of fish and macrophyte invasions could operate separately (non-native fish only) or in combination to disrupt E. menziesii recruitment (Chapter 6). This hypothetical analysis highlighted the importance of considering the threats of both non-native fish and macrophytes, which operate primarily on different stages of the unionid life-cycle, in freshwater mussel conservation and management. Due to the long life-span of unionids, recognition of non-native species impacts contributing to adult-skewed mussel population size-structures may provide an opportunity to restore disrupted mechanisms supporting their recruitment before local extinction occurs. Globalisation and energy demand facilitate continued biotic homogenisation and loss of associated ecosystem services. In this context, the role of management in preventing and mitigating the impacts of biological invasions on sensitive species with affiliate relationships will become increasingly important in freshwater ecosystems in the future.

year: 2020

title: Toward Large-Scale Continuous EDA: A Random Matrix Theory Perspective

authors: Kabán, Ata

subjects: Science & Technology

abstract: Estimations of distribution algorithms (EDAs) are a major branch of evolutionary algorithms (EA) with some unique advantages in principle. They are able to take advantage of correlation structure to drive the search more efficiently, and they are able to provide insights about the structure of the search space. However, model building in high dimensions is extremely challenging, and as a result existing EDAs may become less attractive in large-scale problems because of the associated large computational requirements. 
Large-scale continuous global optimisation is key to many modern-day real-world problems. Scaling up EAs to large-scale problems has become one of the biggest challenges of the field. 
This paper pins down some fundamental roots of the problem and makes a start at developing a new and generic framework to yield effective and efficient EDA-type algorithms for large-scale continuous global optimisation problems. Our concept is to introduce an ensemble of random projections to low dimensions of the set of fittest search points as a basis for developing a new and generic divide-and-conquer methodology. Our ideas are rooted in the theory of random projections developed in theoretical computer science, and in developing and analysing our framework we exploit some recent results in nonasymptotic random matrix theory.
MATLAB code is available from http://www.cs.bham.ac.uk/∼axk/rpm.zip

text: Toward Large-Scale Continuous EDA: A Random Matrix Theory Perspective Estimations of distribution algorithms (EDAs) are a major branch of evolutionary algorithms (EA) with some unique advantages in principle. They are able to take advantage of correlation structure to drive the search more efficiently, and they are able to provide insights about the structure of the search space. However, model building in high dimensions is extremely challenging, and as a result existing EDAs may become less attractive in large-scale problems because of the associated large computational requirements. 
Large-scale continuous global optimisation is key to many modern-day real-world problems. Scaling up EAs to large-scale problems has become one of the biggest challenges of the field. 
This paper pins down some fundamental roots of the problem and makes a start at developing a new and generic framework to yield effective and efficient EDA-type algorithms for large-scale continuous global optimisation problems. Our concept is to introduce an ensemble of random projections to low dimensions of the set of fittest search points as a basis for developing a new and generic divide-and-conquer methodology. Our ideas are rooted in the theory of random projections developed in theoretical computer science, and in developing and analysing our framework we exploit some recent results in nonasymptotic random matrix theory.
MATLAB code is available from http://www.cs.bham.ac.uk/∼axk/rpm.zip

year: 2016

title: ‘Pakeha Bill’: William John McClear, a Pakeha who lived at Te Aroha

authors: Hart, Philip

abstract: Born in Ireland to a Scottish soldier named McAleer, McClear, as he would re-name himself, was uncertain of his age, his birthplace, and the spelling of his name – for, like his parents, he was illiterate. After his drunken father, who abandoned his wife and family, sold him to unknown Maori at an unknown date, he was educated in a Maori school and was unable to speak English until the early 1870s, when he was living with Ngati Rahiri at Omahu pa, at Te Aroha. When Pakeha visitors first met him in 1877, he was a popular resident there and known as Pakeha Bill (or Pakeha William).
Possiby involved in mining before the Te Aroha rush, he both invested in and mined in several claims there from 1880 onwards, and at the end of that decade was one of a small group of Waiorongomai miners who took up a claim at Thames. When not mining, he took whatever jobs were available, struggling financially, in part because of a fondness for drink. As, unlike other Pakeha Maori, there was no evidence of his forming a close relationship with any Maori women, he did not benefit from a Maori wife’s landholdings, and he died in poverty.

text: ‘Pakeha Bill’: William John McClear, a Pakeha who lived at Te Aroha Born in Ireland to a Scottish soldier named McAleer, McClear, as he would re-name himself, was uncertain of his age, his birthplace, and the spelling of his name – for, like his parents, he was illiterate. After his drunken father, who abandoned his wife and family, sold him to unknown Maori at an unknown date, he was educated in a Maori school and was unable to speak English until the early 1870s, when he was living with Ngati Rahiri at Omahu pa, at Te Aroha. When Pakeha visitors first met him in 1877, he was a popular resident there and known as Pakeha Bill (or Pakeha William).
Possiby involved in mining before the Te Aroha rush, he both invested in and mined in several claims there from 1880 onwards, and at the end of that decade was one of a small group of Waiorongomai miners who took up a claim at Thames. When not mining, he took whatever jobs were available, struggling financially, in part because of a fondness for drink. As, unlike other Pakeha Maori, there was no evidence of his forming a close relationship with any Maori women, he did not benefit from a Maori wife’s landholdings, and he died in poverty.

year: 2016