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: The structure and average discrepancies of lattice rules for numerical integration

authors: Reddy, Muni Vasudewan

abstract: Lattice rules are equal-weight quadrature rules which are used in the approximation of multidimensional integrands over the s-dimensional unit cube [0,1]ˢ.  One of the problems encountered in the study of such rules is the unavailability of a unique representation. It is known that any lattice rule may be expressed in a canonical D - Z form in which D is a diagonal matrix whose diagonal entries are known as the invariants and Z is an integer matrix. Although D is unique in this canonical form, Z may be chosen in many different ways. Except for the case of so-called projection-regular and prime-power rules, no such unique Z is available. In the latter case of prime-power rules, the unique D - Z form developed is known as an ultratriangular form. Associated with each ultratriangular form is a set of column indices. Any lattice rule may be decomposed into prime-power components. In this thesis, a unique D - Z form is defined for a special class of lattice rules for which the component prime-power rules have a consistent set of column indices. This new unique form includes the known unique forms for projection-regular and prime-power rules as special cases. We also use the ultratriangular form for prime-power lattice rules to derive a formula to calculate the number of prime-power rules having a given set of invariants and column indices. 

The existing theory of lattice rules that is based on the generator matrix of the dual lattice has made the assumption that its representation in the so-called Hermite normal form is upper triangular. However, since projection-regular rules have a unique Z-matrix which is unit upper triangular, the corresponding generator matrix for the dual lattice is lower triangular. This suggests that a lower triangular Hermite normal form might be appropriate for study. We consider this situation and give the conditions on the lower triangular Hermite normal form which allow a projection-regular rule to be easily recognized. 

Number-theoretic rules are a class of lattice rules which are known to be particularly suitable for the approximation of multidimensional integrals in which the integrands are periodic. In the case of non-periodic integrands there is numerical evidence that the average L₂ discrepancy for these rules is smaller than the expected value for Monte-Carlo rules when the dimension s is less than 18. For non-periodic integrands, a vertex-modified version of the number-theoretic rule has been previously proposed. In s-dimensions these vertex-modified rules contain 2ˢ weights which may be chosen optimally so that the discrepancy is minimized. We shall compare the average discrepancy for these optimal vertex-modified number-theoretic rules with that for normal number-theoretic and Monte-Carlo rules. A similar comparison is also carried out between the averages for number-theoretic rules and for 2ˢ copy rules with approximately the same number of points. 

In the case of periodic integrands it has been shown that the average of Pα and the values of R for 2ˢ copy rules are smaller than those for number-theoretic rules. For this periodic case, we use an analogue of the L₂ discrepancy to carry out a similar comparison.

text: The structure and average discrepancies of lattice rules for numerical integration Lattice rules are equal-weight quadrature rules which are used in the approximation of multidimensional integrands over the s-dimensional unit cube [0,1]ˢ.  One of the problems encountered in the study of such rules is the unavailability of a unique representation. It is known that any lattice rule may be expressed in a canonical D - Z form in which D is a diagonal matrix whose diagonal entries are known as the invariants and Z is an integer matrix. Although D is unique in this canonical form, Z may be chosen in many different ways. Except for the case of so-called projection-regular and prime-power rules, no such unique Z is available. In the latter case of prime-power rules, the unique D - Z form developed is known as an ultratriangular form. Associated with each ultratriangular form is a set of column indices. Any lattice rule may be decomposed into prime-power components. In this thesis, a unique D - Z form is defined for a special class of lattice rules for which the component prime-power rules have a consistent set of column indices. This new unique form includes the known unique forms for projection-regular and prime-power rules as special cases. We also use the ultratriangular form for prime-power lattice rules to derive a formula to calculate the number of prime-power rules having a given set of invariants and column indices. 

The existing theory of lattice rules that is based on the generator matrix of the dual lattice has made the assumption that its representation in the so-called Hermite normal form is upper triangular. However, since projection-regular rules have a unique Z-matrix which is unit upper triangular, the corresponding generator matrix for the dual lattice is lower triangular. This suggests that a lower triangular Hermite normal form might be appropriate for study. We consider this situation and give the conditions on the lower triangular Hermite normal form which allow a projection-regular rule to be easily recognized. 

Number-theoretic rules are a class of lattice rules which are known to be particularly suitable for the approximation of multidimensional integrals in which the integrands are periodic. In the case of non-periodic integrands there is numerical evidence that the average L₂ discrepancy for these rules is smaller than the expected value for Monte-Carlo rules when the dimension s is less than 18. For non-periodic integrands, a vertex-modified version of the number-theoretic rule has been previously proposed. In s-dimensions these vertex-modified rules contain 2ˢ weights which may be chosen optimally so that the discrepancy is minimized. We shall compare the average discrepancy for these optimal vertex-modified number-theoretic rules with that for normal number-theoretic and Monte-Carlo rules. A similar comparison is also carried out between the averages for number-theoretic rules and for 2ˢ copy rules with approximately the same number of points. 

In the case of periodic integrands it has been shown that the average of Pα and the values of R for 2ˢ copy rules are smaller than those for number-theoretic rules. For this periodic case, we use an analogue of the L₂ discrepancy to carry out a similar comparison.

year: 2000

title: Rangatiratanga - Kawanatanga: Dealing with rhetoric

authors: Nikora, Linda Waimarie

abstract: Numbered among the few Maori appointed to an academic position during the late 1980s, I have seen our discipline and profession, in all its awkward self-consciousness, make genuine attempts to grapple the respond to questions and challenges delivered by Maori and Pakeha alike.  For example, Where is the Maori content in courses?  Why aren’t Maori graduating from professional training programmes?  Why are there not more Maori academics? Where is the place/space for Maori as practitioners, academics, researchers and decision-makers?  Why does it seem that Maori are always on the ‘client’ side of the professional/client equation?  Where are the Maori men?  In responding to these persistent challenges the professional and discipline in Aotearoa/New Zealand has been irreversibly changed, in my opinion.  The change has not been dramatic (psychology is somewhat averse to self-promotion) but, of those changes that have occurred, a definite contribution has been made to advancing Maori development, to building a more bicultural discipline and practice, and to supporting the strength of the Kawanatanga and Rangatiratanga dynamic whose importance I emphasize here.

text: Rangatiratanga - Kawanatanga: Dealing with rhetoric Numbered among the few Maori appointed to an academic position during the late 1980s, I have seen our discipline and profession, in all its awkward self-consciousness, make genuine attempts to grapple the respond to questions and challenges delivered by Maori and Pakeha alike.  For example, Where is the Maori content in courses?  Why aren’t Maori graduating from professional training programmes?  Why are there not more Maori academics? Where is the place/space for Maori as practitioners, academics, researchers and decision-makers?  Why does it seem that Maori are always on the ‘client’ side of the professional/client equation?  Where are the Maori men?  In responding to these persistent challenges the professional and discipline in Aotearoa/New Zealand has been irreversibly changed, in my opinion.  The change has not been dramatic (psychology is somewhat averse to self-promotion) but, of those changes that have occurred, a definite contribution has been made to advancing Maori development, to building a more bicultural discipline and practice, and to supporting the strength of the Kawanatanga and Rangatiratanga dynamic whose importance I emphasize here.

year: 2001