title: The blowfly Chrysomya latifrons inhabits fragmented rainforests, but shows no population structure.

authors: Butterworth, Nathan J.

subjects: Diptera

abstract: Climate change and deforestation are causing rainforests to become increasingly fragmented, placing them at heightened risk of biodiversity loss. Invertebrates constitute the greatest proportion of this biodiversity, yet we lack basic knowledge of their population structure and ecology. There is a compelling need to develop our understanding of the population dynamics of a wide range of rainforest invertebrates so that we can begin to understand how rainforest fragments are connected, and how they will cope with future habitat fragmentation and climate change. Blowflies are an ideal candidate for such research because they are widespread, abundant, and can be easily collected within rainforests. We genotyped 188 blowflies (Chrysomya latifrons) from 15 isolated rainforests and found high levels of gene flow, a lack of genetic structure between rainforests, and low genetic diversity - suggesting the presence of a single large genetically depauperate population. This highlights that: (1) the blowfly Ch. latifrons inhabits a ~ 1000 km stretch of Australian rainforests, where it plays an important role as a nutrient recycler; (2) strongly dispersing flies can migrate between and connect isolated rainforests, likely carrying pollen, parasites, phoronts, and pathogens along with them; and (3) widely dispersing and abundant insects can nevertheless be genetically depauperate. There is an urgent need to better understand the relationships between habitat fragmentation, genetic diversity, and adaptive potential-especially for poorly dispersing rainforest-restricted insects, as many of these may be particularly fragmented and at highest risk of local extinction.

text: The blowfly Chrysomya latifrons inhabits fragmented rainforests, but shows no population structure. Climate change and deforestation are causing rainforests to become increasingly fragmented, placing them at heightened risk of biodiversity loss. Invertebrates constitute the greatest proportion of this biodiversity, yet we lack basic knowledge of their population structure and ecology. There is a compelling need to develop our understanding of the population dynamics of a wide range of rainforest invertebrates so that we can begin to understand how rainforest fragments are connected, and how they will cope with future habitat fragmentation and climate change. Blowflies are an ideal candidate for such research because they are widespread, abundant, and can be easily collected within rainforests. We genotyped 188 blowflies (Chrysomya latifrons) from 15 isolated rainforests and found high levels of gene flow, a lack of genetic structure between rainforests, and low genetic diversity - suggesting the presence of a single large genetically depauperate population. This highlights that: (1) the blowfly Ch. latifrons inhabits a ~ 1000 km stretch of Australian rainforests, where it plays an important role as a nutrient recycler; (2) strongly dispersing flies can migrate between and connect isolated rainforests, likely carrying pollen, parasites, phoronts, and pathogens along with them; and (3) widely dispersing and abundant insects can nevertheless be genetically depauperate. There is an urgent need to better understand the relationships between habitat fragmentation, genetic diversity, and adaptive potential-especially for poorly dispersing rainforest-restricted insects, as many of these may be particularly fragmented and at highest risk of local extinction.

year: 2023-03

title: Population genomic insights into invasion success in a polyphagous agricultural pest, Halyomorpha halys

authors: Parvizi, Elahe

subjects: gene flow

abstract: Invasive species are increasingly threatening ecosystems and agriculture by rapidly expanding their range and adapting to environmental and human-imposed selective pressures. The genomic mechanisms that underlie such rapid changes remain unclear, especially for agriculturally important pests. Here, we used genome-wide polymorphisms derived from native, invasive, and intercepted samples and populations of the brown marmorated stink bug (BMSB), Halyomorpha halys, to gain insights into population genomics processes that have promoted the successful global invasion of this polyphagous pest. Our analysis demonstrated that BMSB exhibits spatial structure but admixture rates are high among introduced populations, resulting in similar levels of genomic diversity across native and introduced populations. These spatial genomic patterns suggest a complex invasion scenario, potentially with multiple bridgehead events, posing a challenge for accurately assigning BMSB incursions to their source using reduced-representation genomic data. By associating allele frequencies with the invasion status of BMSB populations, we found significantly differentiated single nucleotide polymorphisms (SNPs) located in close proximity to genes for insecticide resistance and olfaction. Comparing variations in allele frequencies among populations for outlier SNPs suggests that BMSB invasion success has probably evolved from standing genetic variation. In addition to being a major nuisance of households, BMSB has caused significant economic losses to agriculture in recent years and continues to expand its range. Despite no record of BMSB insecticide resistance to date, our results show high capacity for potential evolution of such traits, highlighting the need for future sustainable and targeted management strategies.

text: Population genomic insights into invasion success in a polyphagous agricultural pest, Halyomorpha halys Invasive species are increasingly threatening ecosystems and agriculture by rapidly expanding their range and adapting to environmental and human-imposed selective pressures. The genomic mechanisms that underlie such rapid changes remain unclear, especially for agriculturally important pests. Here, we used genome-wide polymorphisms derived from native, invasive, and intercepted samples and populations of the brown marmorated stink bug (BMSB), Halyomorpha halys, to gain insights into population genomics processes that have promoted the successful global invasion of this polyphagous pest. Our analysis demonstrated that BMSB exhibits spatial structure but admixture rates are high among introduced populations, resulting in similar levels of genomic diversity across native and introduced populations. These spatial genomic patterns suggest a complex invasion scenario, potentially with multiple bridgehead events, posing a challenge for accurately assigning BMSB incursions to their source using reduced-representation genomic data. By associating allele frequencies with the invasion status of BMSB populations, we found significantly differentiated single nucleotide polymorphisms (SNPs) located in close proximity to genes for insecticide resistance and olfaction. Comparing variations in allele frequencies among populations for outlier SNPs suggests that BMSB invasion success has probably evolved from standing genetic variation. In addition to being a major nuisance of households, BMSB has caused significant economic losses to agriculture in recent years and continues to expand its range. Despite no record of BMSB insecticide resistance to date, our results show high capacity for potential evolution of such traits, highlighting the need for future sustainable and targeted management strategies.

year: 2022-10-17

title: Māori and the [potential] demographic dividend

authors: Jackson, Natalie

subjects: demography

abstract: This paper outlines a recently articulated concept in the demographic literature known as the ‘demographic dividend’, and connects it with key features of Māori and non- Māori demography. The dividend arises – or has the potential to arise - as each population passes through a particular point in its demographic transition. During these years, the maximum proportion of the population moves into the key working and income-earning age groups, and the minimum (comprised of youth and the elderly) is notionally dependent. With proactive and timely investment in the youthful base of the population, there is potential to convert the demographic dividend into two economic windfalls, the first arising as fertility decline causes youthful dependency to fall and the last large waves of young adults flood into the working age population, the second as the latter age and move on into the higher income earning age groups. However the window of opportunity to invest in the first dividend is fleeting, while failure to invest in that stage seriously compromises the second. This paper shows that for the Māori population, despite its relative youth, the first opportunity is already coming to an end and with it the potential gains of the second. But it also argues that there is a third window of opportunity which holds particular promise for Māori. This period will also be fleeting, but is arising in both absolute and relative terms as the relatively youthful Māori population co-exists alongside its structurally older counterpart, and together (with other New Zealanders) comprise an ‘economic dividend system’ that produces the potential for a ‘collateral dividend’.

text: Māori and the [potential] demographic dividend This paper outlines a recently articulated concept in the demographic literature known as the ‘demographic dividend’, and connects it with key features of Māori and non- Māori demography. The dividend arises – or has the potential to arise - as each population passes through a particular point in its demographic transition. During these years, the maximum proportion of the population moves into the key working and income-earning age groups, and the minimum (comprised of youth and the elderly) is notionally dependent. With proactive and timely investment in the youthful base of the population, there is potential to convert the demographic dividend into two economic windfalls, the first arising as fertility decline causes youthful dependency to fall and the last large waves of young adults flood into the working age population, the second as the latter age and move on into the higher income earning age groups. However the window of opportunity to invest in the first dividend is fleeting, while failure to invest in that stage seriously compromises the second. This paper shows that for the Māori population, despite its relative youth, the first opportunity is already coming to an end and with it the potential gains of the second. But it also argues that there is a third window of opportunity which holds particular promise for Māori. This period will also be fleeting, but is arising in both absolute and relative terms as the relatively youthful Māori population co-exists alongside its structurally older counterpart, and together (with other New Zealanders) comprise an ‘economic dividend system’ that produces the potential for a ‘collateral dividend’.

year: 2011-06