title: Phylogeography of New Zealand’s coastal benthos

authors: Ross, Philip M.

subjects: genetic differentiation

abstract: During the past 30 years, 42 molecular studies have been undertaken in New Zealand to examine the phylogeography of coastal benthic invertebrates and plants. Here, we identify generalities and/or patterns that have emerged from this research and consider the processes implicated in generating genetic structure within populations. Studies have used various molecular markers and examined taxonomic groups with a range of life histories and dispersal strategies. Genetic disjunctions have been identified at multiple locations, with the most frequently observed division occurring between northern and southern populations at the top of the South Island. Although upwelling has been implicated as a cause of this disjunction, oceanographic evidence is lacking and alternative hypotheses exist. A significant negative correlation between larval duration and genetic differentiation (r2 = 0.39, P < 0.001, n = 29) across all studies suggests that larval duration might be used as a proxy for dispersal potential. However, among taxa with short larval durations (<10 days) there was greater variability in genetic differentiation than among taxa with longer pelagic periods. This variability implies that when larval duration is short, other factors may determine dispersal and connectivity among populations. Although there has been little congruence between the phylogeographic data and recognised biogeographic regions, recent research has resolved population subdivision at finer spatial scales corresponding more closely with existing biogeographic classifications. The use of fast-evolving and ecologically significant molecular markers in hypothesis-driven research could further improve our ability to detect population subdivision and identify the processes structuring marine ecosystems.

text: Phylogeography of New Zealand’s coastal benthos During the past 30 years, 42 molecular studies have been undertaken in New Zealand to examine the phylogeography of coastal benthic invertebrates and plants. Here, we identify generalities and/or patterns that have emerged from this research and consider the processes implicated in generating genetic structure within populations. Studies have used various molecular markers and examined taxonomic groups with a range of life histories and dispersal strategies. Genetic disjunctions have been identified at multiple locations, with the most frequently observed division occurring between northern and southern populations at the top of the South Island. Although upwelling has been implicated as a cause of this disjunction, oceanographic evidence is lacking and alternative hypotheses exist. A significant negative correlation between larval duration and genetic differentiation (r2 = 0.39, P < 0.001, n = 29) across all studies suggests that larval duration might be used as a proxy for dispersal potential. However, among taxa with short larval durations (<10 days) there was greater variability in genetic differentiation than among taxa with longer pelagic periods. This variability implies that when larval duration is short, other factors may determine dispersal and connectivity among populations. Although there has been little congruence between the phylogeographic data and recognised biogeographic regions, recent research has resolved population subdivision at finer spatial scales corresponding more closely with existing biogeographic classifications. The use of fast-evolving and ecologically significant molecular markers in hypothesis-driven research could further improve our ability to detect population subdivision and identify the processes structuring marine ecosystems.

year: 2009

title: Multiple frequency range imaging to remove measurement ambiguity

authors: Payne, Andrew D.

subjects: range imaging system

abstract: Range imaging systems use a specialised sensor to capture an image where object distance (range) is measured for every pixel using time-of-flight. The scene is illuminated with an amplitude modulated light source, and the phase of the modulation envelope of the reflected light is measured to determine flight time, hence object distance for each pixel. As the modulation waveform is cyclic, an ambiguity problem exists if the phase shift exceeds 2π radians. To overcome this problem we demonstrate a method that superposes two different modulation frequencies within a single capture. This technique reduces the associated overhead compared with performing two sequential measurements, allowing the system to retain high range measurement precision at rapid acquisition rates. A method is also provided to avoid interference from aliased harmonics during sampling, which otherwise contaminate the resulting range measurement. Experimental results show the potential of the multiple frequency approach; producing high measurement precision while avoiding ambiguity. The results also demonstrate the limitation of this technique, where large errors can be introduced through a combination of a low signal to noise ratio and suboptimal selection of system parameters.

text: Multiple frequency range imaging to remove measurement ambiguity Range imaging systems use a specialised sensor to capture an image where object distance (range) is measured for every pixel using time-of-flight. The scene is illuminated with an amplitude modulated light source, and the phase of the modulation envelope of the reflected light is measured to determine flight time, hence object distance for each pixel. As the modulation waveform is cyclic, an ambiguity problem exists if the phase shift exceeds 2π radians. To overcome this problem we demonstrate a method that superposes two different modulation frequencies within a single capture. This technique reduces the associated overhead compared with performing two sequential measurements, allowing the system to retain high range measurement precision at rapid acquisition rates. A method is also provided to avoid interference from aliased harmonics during sampling, which otherwise contaminate the resulting range measurement. Experimental results show the potential of the multiple frequency approach; producing high measurement precision while avoiding ambiguity. The results also demonstrate the limitation of this technique, where large errors can be introduced through a combination of a low signal to noise ratio and suboptimal selection of system parameters.

year: 2009

title: Education leaders can reduce educational disparities

authors: Bishop, Russell

subjects: education

abstract: This chapter is about how education leaders can act to reduce educational disparities for indigenous and other minoritized peoples through strategic goal setting, supporting effective pedagogies of relations, promoting distributed leadership, enacting inclusivity, using evidence and owning the need for reform. Examples are drawn from a large-scale, theory-based education reform project called Te Kotahitanga which is currently running in 50 secondary schools in New Zealand. Developing a model for effective leadership needs to commence with the understanding that the key to change is teacher action supported by responsive structural reform (Elmore 2004). In our earlier work (Bishop et al. 2003, 2007) we investigated what effective teacher action looks like. This chapter presents a model of what “responsive structural reform” looks like in practice and what leaders need to do to implement and sustain gains made in student performance at the classroom, school and system-wide levels.

text: Education leaders can reduce educational disparities This chapter is about how education leaders can act to reduce educational disparities for indigenous and other minoritized peoples through strategic goal setting, supporting effective pedagogies of relations, promoting distributed leadership, enacting inclusivity, using evidence and owning the need for reform. Examples are drawn from a large-scale, theory-based education reform project called Te Kotahitanga which is currently running in 50 secondary schools in New Zealand. Developing a model for effective leadership needs to commence with the understanding that the key to change is teacher action supported by responsive structural reform (Elmore 2004). In our earlier work (Bishop et al. 2003, 2007) we investigated what effective teacher action looks like. This chapter presents a model of what “responsive structural reform” looks like in practice and what leaders need to do to implement and sustain gains made in student performance at the classroom, school and system-wide levels.

year: 2011