A new molecular diagnostic tool for surveying and monitoring Triops cancriformis populations

© 2017 Sellers et al. The tadpole shrimp, Triops cancriformis, is a freshwater crustacean listed as endangered in the UK and Europe living in ephemeral pools. Populations are threatened by habitat destruction due to land development for agriculture and increased urbanisation. Despite this, there is a lack of efficient methods for discovering and monitoring populations. Established macroinvertebrate monitoring methods, such as net sampling, are unsuitable given the organism's life history, that include long lived diapausing eggs, benthic habits and ephemerally active populations. Conventional hatching methods, such as sediment incubation, are both time consuming and potentially confounded by bet-hedging hatching strategies of diapausing eggs. Here we develop a new molecular diagnostic method to detect viable egg banks of T. cancriformis, and compare its performance to two conventional monitoring methods involving diapausing egg hatching. We apply this method to a collection of pond sediments from the Wildfowl & Wetlands Trust Caerlaverock National Nature Reserve, which holds one of the two remaining British populations of T. cancriformis. DNA barcoding of isolated eggs, using newly designed species-specific primers for a large region of mtDNA, was used to estimate egg viability. These estimates were compared to those obtained by the conventional methods of sediment and isolation hatching. Our method outperformed the conventional methods, revealing six ponds holding viable T. cancriformis diapausing egg banks in Caerlaverock. Additionally, designed species-specific primers for a short region of mtDNA identified degraded, inviable eggs and were used to ascertain the levels of recent mortality within an egg bank. Together with efficient sugar flotation techniques to extract eggs from sediment samples, our molecular method proved to be a faster and more powerful alternative for assessing the viability and condition of T. cancriformis diapausing egg banks

Genetic factors affecting establishment during invasions : the introduction of the topmouth gudgeon (Pseudorasbora parva) and the rainbow trout (Oncorhynchus mykiss) in Europe

The study of biological invasions is a major research topic, both because of the ecological and economical damage caused by invasive species and also as a great natural experiment to study evolutionary responses of non-native populations to their new environment, and the factors influencing invasions. Introduced species often evolve rapidly, despite the assumed loss of genetic variation associated with bottlenecks during the invasion process. In order examine the processes and mechanisms affecting the outcome invasions I studied two non-native fish species, the topmouth gudgeon (Pseudorasbora parva) is an Asian cyprinid that is found in most European countries as a result of accidental introductions. Rainbow trout (Oncorhynchus mykiss) has been introduced from the United States for aquaculture and angling, however, despite numerous introductions, it has only been able to establish in few European waters. I used mitochondrial DNA and microsatellite markers to understand the invasion history of these species and the factors that influence their establishment success/failure. Part of the cytochrome b gene was analysed in European and native Asian P. parva populations and microsatellite markers were used to investigate the source populations of the species. The analyses elucidated the colonisation pattern of P. parva in Europe and supported the hypothesis that the species spread through long-distance and stepping-stone methods and originate from admixed source populations. In O. mykiss, part of the d-loop region of the mitochondrial genome was analysed to compare the phylogeographic structure of native US and introduced European populations to examine the spread of the species outside its native range, as well as to find out whether the resistant Hofer strain is the source population of the European rainbow trout populations. I found that European populations are likely to originate from various sources, mainly from California. The Hofer strain is likely to have contributed to some of the wild European populations. Assessing the role of these processes is fundamental in understanding invasive species and finding suitable management practices to control them. From an evolutionary point of view, I was able to detect some of the processes that are important during invasions, in these studies particularly the role of multiple introductions and introduction from genetically admixed source populations.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Genetic factors affecting establishment during invasions : the introduction of the topmouth gudgeon (Pseudorasbora parva) and the rainbow trout (Oncorhynchus mykiss) in Europe

The study of biological invasions is a major research topic, both because of the ecological and economical damage caused by invasive species and also as a great natural experiment to study evolutionary responses of non-native populations to their new environment, and the factors influencing invasions. Introduced species often evolve rapidly, despite the assumed loss of genetic variation associated with bottlenecks during the invasion process. In order examine the processes and mechanisms affecting the outcome invasions I studied two non-native fish species, the topmouth gudgeon (Pseudorasbora parva) is an Asian cyprinid that is found in most European countries as a result of accidental introductions. Rainbow trout (Oncorhynchus mykiss) has been introduced from the United States for aquaculture and angling, however, despite numerous introductions, it has only been able to establish in few European waters. I used mitochondrial DNA and microsatellite markers to understand the invasion history of these species and the factors that influence their establishment success/failure. Part of the cytochrome b gene was analysed in European and native Asian P. parva populations and microsatellite markers were used to investigate the source populations of the species. The analyses elucidated the colonisation pattern of P. parva in Europe and supported the hypothesis that the species spread through long-distance and stepping-stone methods and originate from admixed source populations. In O. mykiss, part of the d-loop region of the mitochondrial genome was analysed to compare the phylogeographic structure of native US and introduced European populations to examine the spread of the species outside its native range, as well as to find out whether the resistant Hofer strain is the source population of the European rainbow trout populations. I found that European populations are likely to originate from various sources, mainly from California. The Hofer strain is likely to have contributed to some of the wild European populations. Assessing the role of these processes is fundamental in understanding invasive species and finding suitable management practices to control them. From an evolutionary point of view, I was able to detect some of the processes that are important during invasions, in these studies particularly the role of multiple introductions and introduction from genetically admixed source populations.EThOS - Electronic Theses Online ServiceGBUnited Kingdo