title: Fitness consequences of population bottlenecks in an invasive blowfly

authors: Croft, Lillian

subjects: biological invasion

abstract: Invasive species often undergo demographic bottlenecks that cause a decrease in genetic diversity and associated reductions in population fitness. Despite this, they manage to thrive in novel environments. Investigating the effects of inbreeding and genetic bottlenecks on population fitness for invasive species is, therefore, key to understanding how they may survive in new environments. We used the blowfly Calliphora vicina (Sciences, Mathématiques et Physique, 1830, 2, 1), which is native to Europe and was introduced to Australia and New Zealand, to examine the effects of genetic diversity on population fitness. We first collected 59 samples from 15 populations across New Zealand and one in Australia, and used 20,501 biallelic SNPs to investigate population genomic diversity, structure and admixture. We then explored the impacts of repeated experimental bottlenecks on population fitness by creating inbred and outbred lines of C. vicina and measuring a variety of fitness traits. In wild-caught samples, we found low overall genetic diversity, signals of genetic admixture and limited (<3%) genetic differentiation between North and South Island populations, with genetic links between the South Island and Australia. Following experimental bottlenecks, we found significant reductions in fitness for inbred lines. However, fitness effects were not felt equally across all phenotypic traits. Moreover, they were not enough to cause population collapse in any experimental line, suggesting that C. vicina (when under relaxed selection, as in laboratory settings) may be able to compensate for population bottlenecks even when highly inbred. Our results demonstrate the value of a tractable experimental system for investigating processes that may facilitate or hamper biological invasion.

text: Fitness consequences of population bottlenecks in an invasive blowfly Invasive species often undergo demographic bottlenecks that cause a decrease in genetic diversity and associated reductions in population fitness. Despite this, they manage to thrive in novel environments. Investigating the effects of inbreeding and genetic bottlenecks on population fitness for invasive species is, therefore, key to understanding how they may survive in new environments. We used the blowfly Calliphora vicina (Sciences, Mathématiques et Physique, 1830, 2, 1), which is native to Europe and was introduced to Australia and New Zealand, to examine the effects of genetic diversity on population fitness. We first collected 59 samples from 15 populations across New Zealand and one in Australia, and used 20,501 biallelic SNPs to investigate population genomic diversity, structure and admixture. We then explored the impacts of repeated experimental bottlenecks on population fitness by creating inbred and outbred lines of C. vicina and measuring a variety of fitness traits. In wild-caught samples, we found low overall genetic diversity, signals of genetic admixture and limited (<3%) genetic differentiation between North and South Island populations, with genetic links between the South Island and Australia. Following experimental bottlenecks, we found significant reductions in fitness for inbred lines. However, fitness effects were not felt equally across all phenotypic traits. Moreover, they were not enough to cause population collapse in any experimental line, suggesting that C. vicina (when under relaxed selection, as in laboratory settings) may be able to compensate for population bottlenecks even when highly inbred. Our results demonstrate the value of a tractable experimental system for investigating processes that may facilitate or hamper biological invasion.

year: 2024

title: Review: Electronic Music, Vol. III, Música Viva Competition Prize Winners 2004—2005—2006

authors: Whalley, Ian

subjects: music

abstract: This collection, the third in a series from Miso Records in Portugal, collates the prizewinners of the Música Viva Competition from 2004 to 2006. The competition has assumed increasing importance on the international circuit, with 2006 being the seventh year it has been held. Entry to the competition is limited to composers under the age of 35. The last few years has attracted an average of 120 applicants from a range of nationalities.

text: Review: Electronic Music, Vol. III, Música Viva Competition Prize Winners 2004—2005—2006 This collection, the third in a series from Miso Records in Portugal, collates the prizewinners of the Música Viva Competition from 2004 to 2006. The competition has assumed increasing importance on the international circuit, with 2006 being the seventh year it has been held. Entry to the competition is limited to composers under the age of 35. The last few years has attracted an average of 120 applicants from a range of nationalities.

year: 2009

title: Carbon dioxide and methane emissions from the Te Arawa lakes of Rotorua, New Zealand

authors: Santoso, Arianto Budi

subjects: global carbon cycle

abstract: One of the biggest issues confronting humankind today is global warming due to the rapidly increasing greenhouse gas (GHG) emissions, namely CO₂, CH₄ and N₂O. The Intergovernmental Panel for Climate Change (IPCC) has prepared an emission reduction strategy. So far, inland waters, including lakes and reservoirs, have not been included in the global carbon cycle. However, the contribution of inland waters to global CO₂ and CH₄ emissions has been identified to be important. Inland waters are also known to be a major sink for GHG emissions by attenuating carbon that would otherwise be transported from the terrestrial landscape to the ocean. Lakes are also very sensitive to climate change as well as to human impacts generally, and these effects will need to be considered in understanding the future role of lakes in the global carbon cycle.
This study aimed to improve understanding of CO₂ and CH₄ emissions from lakes, and to quantify these emissions under changing climate and nutrient loading regimes in a regionally discrete group of lakes of volcanic origin in North Island of New Zealand. It included a comprehensive field study of one lake, application of process-based numerical modelling to the lake, and collation and critical analysis of existing datasets for the group of lakes. The primary study site was Okaro, a monomictic eutrophic lake where a major restoration program has been in place for more than one decade. The study also extended to 10 other lakes in order to give insights into effects of different nutrient and mixing regimes on carbon sources and sinks
Based on observations over a one-period (September 2013 – October 2014), Lake Okaro accumulated CO₂ and CH₄ in the hypolimnion during summer stratification. These gases were entrained into surface waters as lake started to turnover just prior to complete mixing in winter. As recorded in many other eutrophic lakes, the net CO₂ flux was mostly from the atmosphere to the lake. However, CO₂, together with CH₄, escaped from the lake as a pulsed emission in winter.  Using a simple annual mass balance model it was calculated that, ~31% of CH₄ sourced from the sediment escaped to the atmosphere through diffusive flux. The remainder was likely to be oxidized in the water column. The model also showed that on an annual basis the net CO₂ emission is out of the lake. These findings suggest that eutrophic lakes may actually be net emitters of greenhouse gases and that pulsed emissions may be an important contributor to the direction of the flux. This study did not account for CH₄ ebullition, however, and therefore the magnitude of GHG emissions from this lake is likely to be lower than predicted. 
The effects on CO₂ and CH₄ emissions from Lake Okaro of a warming climate and changes in nutrient loads was simulated using a coupled hydrodynamic-ecological model (GLM-AED2). Future possible changes were simulated by altering model forcing data, increasing air temperature by 2.5 °C. Internal and external nutrient (nitrogen and phosphorus) loads were also either halved or increased by one half. Model simulations showed that annual CO₂ uptake by the lake was enhanced under a warmer climate, but emissions of CH₄ increased during lake overturn as a result of greater diffusive fluxes. Total GHG emissions, as CO₂ equivalent (kg CO₂-eq m⁻² y⁻¹), from the lake were predicted with model simulations to increase by 27% under a warming climate, relative to present conditions. This increase would be reduced to 19% if nutrient loading was halved.
A first-order diagenesis model was used to estimate the carbon deposition in the 11 Te Arawa lakes. The most productive lakes, using chlorophyll a as a proxy, had higher rates of carbon deposition in the bottom sediments than the less productive lakes. However, burial efficiency (buried carbon: deposited carbon) was lower in productive lakes meaning that most of the deposited carbon in these lakes is remineralized back into the water column. This remineralization process can be associated with CO₂ and CH₄ emissions from the lake.
The results of this study highlight that eutrophic lakes may contribute emit higher levels of GHGs to the atmosphere than has previously been estimated, primarily as a result of pulsed emissions associated with the onset of seasonal mixing, at least in monomictic lakes.  Eutrophication and climate warming are likely to enhance GHG emissions from lakes. The findings from this study have important implications for global GHG fluxes and indicate that fluxes into or from lakes need to be included in inventories. Reducing nutrient loads to lakes could offset some of the predicted increases in emissions of GHGs that are likely to occur with climate warming.

text: Carbon dioxide and methane emissions from the Te Arawa lakes of Rotorua, New Zealand One of the biggest issues confronting humankind today is global warming due to the rapidly increasing greenhouse gas (GHG) emissions, namely CO₂, CH₄ and N₂O. The Intergovernmental Panel for Climate Change (IPCC) has prepared an emission reduction strategy. So far, inland waters, including lakes and reservoirs, have not been included in the global carbon cycle. However, the contribution of inland waters to global CO₂ and CH₄ emissions has been identified to be important. Inland waters are also known to be a major sink for GHG emissions by attenuating carbon that would otherwise be transported from the terrestrial landscape to the ocean. Lakes are also very sensitive to climate change as well as to human impacts generally, and these effects will need to be considered in understanding the future role of lakes in the global carbon cycle.
This study aimed to improve understanding of CO₂ and CH₄ emissions from lakes, and to quantify these emissions under changing climate and nutrient loading regimes in a regionally discrete group of lakes of volcanic origin in North Island of New Zealand. It included a comprehensive field study of one lake, application of process-based numerical modelling to the lake, and collation and critical analysis of existing datasets for the group of lakes. The primary study site was Okaro, a monomictic eutrophic lake where a major restoration program has been in place for more than one decade. The study also extended to 10 other lakes in order to give insights into effects of different nutrient and mixing regimes on carbon sources and sinks
Based on observations over a one-period (September 2013 – October 2014), Lake Okaro accumulated CO₂ and CH₄ in the hypolimnion during summer stratification. These gases were entrained into surface waters as lake started to turnover just prior to complete mixing in winter. As recorded in many other eutrophic lakes, the net CO₂ flux was mostly from the atmosphere to the lake. However, CO₂, together with CH₄, escaped from the lake as a pulsed emission in winter.  Using a simple annual mass balance model it was calculated that, ~31% of CH₄ sourced from the sediment escaped to the atmosphere through diffusive flux. The remainder was likely to be oxidized in the water column. The model also showed that on an annual basis the net CO₂ emission is out of the lake. These findings suggest that eutrophic lakes may actually be net emitters of greenhouse gases and that pulsed emissions may be an important contributor to the direction of the flux. This study did not account for CH₄ ebullition, however, and therefore the magnitude of GHG emissions from this lake is likely to be lower than predicted. 
The effects on CO₂ and CH₄ emissions from Lake Okaro of a warming climate and changes in nutrient loads was simulated using a coupled hydrodynamic-ecological model (GLM-AED2). Future possible changes were simulated by altering model forcing data, increasing air temperature by 2.5 °C. Internal and external nutrient (nitrogen and phosphorus) loads were also either halved or increased by one half. Model simulations showed that annual CO₂ uptake by the lake was enhanced under a warmer climate, but emissions of CH₄ increased during lake overturn as a result of greater diffusive fluxes. Total GHG emissions, as CO₂ equivalent (kg CO₂-eq m⁻² y⁻¹), from the lake were predicted with model simulations to increase by 27% under a warming climate, relative to present conditions. This increase would be reduced to 19% if nutrient loading was halved.
A first-order diagenesis model was used to estimate the carbon deposition in the 11 Te Arawa lakes. The most productive lakes, using chlorophyll a as a proxy, had higher rates of carbon deposition in the bottom sediments than the less productive lakes. However, burial efficiency (buried carbon: deposited carbon) was lower in productive lakes meaning that most of the deposited carbon in these lakes is remineralized back into the water column. This remineralization process can be associated with CO₂ and CH₄ emissions from the lake.
The results of this study highlight that eutrophic lakes may contribute emit higher levels of GHGs to the atmosphere than has previously been estimated, primarily as a result of pulsed emissions associated with the onset of seasonal mixing, at least in monomictic lakes.  Eutrophication and climate warming are likely to enhance GHG emissions from lakes. The findings from this study have important implications for global GHG fluxes and indicate that fluxes into or from lakes need to be included in inventories. Reducing nutrient loads to lakes could offset some of the predicted increases in emissions of GHGs that are likely to occur with climate warming.

year: 2016