title: A New Species of Pittosporum Described from the Poor Knights Islands, Northland, Aotearoa/New Zealand

authors: Carter, Sophie N

subjects: Science & Technology

abstract: Here we describe Pittosporum roimata Gemmill & S.N. Carter, the only vascular plant endemic to the Poor Knights Islands, Northland, Aotearoa/New Zealand. This new species has previously been referred to as a distinct yellow-flowered variant of Pittosporum cornifolium (tāwhiri karo, wharewhareatua), a morphologically similar epiphytic shrub known from both main islands of New Zealand as well as other off shore islands. We have segregated this new species from P. cornifolium based on morphology, DNA sequence variation, as well as distribution. Pittosporum roimata is distinguished from P. cornifolium by flowers with yellow petals, larger inflorescences, and producing several terminal fruits per stem. Herbarium specimens of P. roimata statistically have larger leaves and shorter petioles than specimens of P. cornifolium. Pittosporum roimata is locally common on the islands of Tawhiti Rahi, Aorangi, and Aorangaia, growing on rocky substrates associated with Xeronema callistemon (raupo taranga) and Metrosideros excelsa (pōhutukawa). Using the current New Zealand Threat Classification System, we suggest a preliminary classification of this new species as ‘at risk/naturally uncommon’ qualified data poor [DP], one location [OL].

text: A New Species of Pittosporum Described from the Poor Knights Islands, Northland, Aotearoa/New Zealand Here we describe Pittosporum roimata Gemmill & S.N. Carter, the only vascular plant endemic to the Poor Knights Islands, Northland, Aotearoa/New Zealand. This new species has previously been referred to as a distinct yellow-flowered variant of Pittosporum cornifolium (tāwhiri karo, wharewhareatua), a morphologically similar epiphytic shrub known from both main islands of New Zealand as well as other off shore islands. We have segregated this new species from P. cornifolium based on morphology, DNA sequence variation, as well as distribution. Pittosporum roimata is distinguished from P. cornifolium by flowers with yellow petals, larger inflorescences, and producing several terminal fruits per stem. Herbarium specimens of P. roimata statistically have larger leaves and shorter petioles than specimens of P. cornifolium. Pittosporum roimata is locally common on the islands of Tawhiti Rahi, Aorangi, and Aorangaia, growing on rocky substrates associated with Xeronema callistemon (raupo taranga) and Metrosideros excelsa (pōhutukawa). Using the current New Zealand Threat Classification System, we suggest a preliminary classification of this new species as ‘at risk/naturally uncommon’ qualified data poor [DP], one location [OL].

year: 2018-04-01

title: Interactions between ship rats and house mice

authors: Bridgman, Lucy Jade

subjects: Rattus rattus

abstract: Interactions between coexisting invasive species can cause complications when their populations are managed to protect native biodiversity. The ship rat (Rattus rattus) is a widespread invasive species often targeted for management because of its negative impacts on native wildlife, particularly in otherwise mammal-depauperate ecosystems such as in New Zealand. However, where ship rats are removed, another common, coexisting invasive species, the house mouse (Mus musculus), is often detected more frequently, which may undermine the benefit of the management operation for biodiversity. The aim of this study was to better understand why house mice become more abundant, or potentially also more active and detectable, when released from suppression by ship rats through determining the mechanism involved. The hypothesised mechanisms were: exploitation competition, interference competition and intraguild predation. 

Focusing on New Zealand, I reviewed diet studies of ship rats and house mice to have a clearer understanding of the resources they may share. I found that whilst some features of their diets differ, ship rats and house mice do show overlap in the range of food items they consume. Therefore they could compete for these shared resources if they were limited. However, in captive experiments I confirmed that ship rats exhibit predatory aggression towards house mice and therefore have potential to directly negatively influence mouse populations regardless of resource availability. 

In response to the threat of predation by ship rats, house mice exhibited avoidance of caged rats during further captive experiments and this restricted their foraging choices. In the field, the foraging behaviour of mice in podocarp-broadleaf forest was also limited by the risk posed from abundant ship rats, which prevented them from accessing resources. In similar habitat at Pureora Forest Park during a longer term study of mouse populations, mice captured when ship rats were abundant had lower body mass compared to those captured when ship rats were controlled, an effect that was not offset by supplementary feeding.

At Pureora, the ship rat control operations did not achieve optimal low ship rat levels, however, despite small mouse sample sizes, both the abundance of mice measured by live-trapping and their activity in tracking tunnels were positively affected. These measures were moderately correlated indicating that activity was related to mouse abundance. However, capture probability varied seasonally and according to rat abundance in unexpected ways, indicating more subtle and complex potential influences of ship rats on the probability of detecting mice. 

My results indicate that the main mechanism by which ship rats suppress house mice is intraguild predation. This is because though apparently food restricted, house mice did not access resources I provided for them when ship rats were abundant, which rules out exploitation competition. Ship rats appear to view house mice as prey and opportunistically consume them, which differentiates intraguild predation from interference competition as the latter is primarily driven by resource defence. Even if predation events are rare, my research demonstrates that the risk effects of avoiding an abundant opportunistic predator appear to have a strong influence on the abundance and distribution of house mice.

text: Interactions between ship rats and house mice Interactions between coexisting invasive species can cause complications when their populations are managed to protect native biodiversity. The ship rat (Rattus rattus) is a widespread invasive species often targeted for management because of its negative impacts on native wildlife, particularly in otherwise mammal-depauperate ecosystems such as in New Zealand. However, where ship rats are removed, another common, coexisting invasive species, the house mouse (Mus musculus), is often detected more frequently, which may undermine the benefit of the management operation for biodiversity. The aim of this study was to better understand why house mice become more abundant, or potentially also more active and detectable, when released from suppression by ship rats through determining the mechanism involved. The hypothesised mechanisms were: exploitation competition, interference competition and intraguild predation. 

Focusing on New Zealand, I reviewed diet studies of ship rats and house mice to have a clearer understanding of the resources they may share. I found that whilst some features of their diets differ, ship rats and house mice do show overlap in the range of food items they consume. Therefore they could compete for these shared resources if they were limited. However, in captive experiments I confirmed that ship rats exhibit predatory aggression towards house mice and therefore have potential to directly negatively influence mouse populations regardless of resource availability. 

In response to the threat of predation by ship rats, house mice exhibited avoidance of caged rats during further captive experiments and this restricted their foraging choices. In the field, the foraging behaviour of mice in podocarp-broadleaf forest was also limited by the risk posed from abundant ship rats, which prevented them from accessing resources. In similar habitat at Pureora Forest Park during a longer term study of mouse populations, mice captured when ship rats were abundant had lower body mass compared to those captured when ship rats were controlled, an effect that was not offset by supplementary feeding.

At Pureora, the ship rat control operations did not achieve optimal low ship rat levels, however, despite small mouse sample sizes, both the abundance of mice measured by live-trapping and their activity in tracking tunnels were positively affected. These measures were moderately correlated indicating that activity was related to mouse abundance. However, capture probability varied seasonally and according to rat abundance in unexpected ways, indicating more subtle and complex potential influences of ship rats on the probability of detecting mice. 

My results indicate that the main mechanism by which ship rats suppress house mice is intraguild predation. This is because though apparently food restricted, house mice did not access resources I provided for them when ship rats were abundant, which rules out exploitation competition. Ship rats appear to view house mice as prey and opportunistically consume them, which differentiates intraguild predation from interference competition as the latter is primarily driven by resource defence. Even if predation events are rare, my research demonstrates that the risk effects of avoiding an abundant opportunistic predator appear to have a strong influence on the abundance and distribution of house mice.

year: 2012

title: Sweet as – the [ADJ + as] intensifier construction in Māori English/ Aotearoa English.

authors: Calude, Andreea S.

abstract: We introduce the Waikato Māori English Conversation (MEC) corpus, which consists of 43 dyadic conversations between 49 young adults who self-recorded informal conversations with close friends, in their own homes, with no topic of conversation specified (83 hours of dialogue; nearly 800,000 words). The resulting materials are colloquial and unstructured, capturing a wider range of pragmatic and stylistic modes than is possible in a standard sociolinguistic interview. Here, we report on one such feature, the [ADJ + as] construction, for example: ‘sorry some of the questions are like awkward as’ and ‘that caused a big as drama eh’. This intensifier construction has been identified as a distinctive New Zealand English (NZE) innovation, yet little has been written about this it. However, the Waikato MEC corpus presents the opportunity to analyse the construction in a more systematic manner and to fill existing gaps in analyses of Māori English grammar.

text: Sweet as – the [ADJ + as] intensifier construction in Māori English/ Aotearoa English. We introduce the Waikato Māori English Conversation (MEC) corpus, which consists of 43 dyadic conversations between 49 young adults who self-recorded informal conversations with close friends, in their own homes, with no topic of conversation specified (83 hours of dialogue; nearly 800,000 words). The resulting materials are colloquial and unstructured, capturing a wider range of pragmatic and stylistic modes than is possible in a standard sociolinguistic interview. Here, we report on one such feature, the [ADJ + as] construction, for example: ‘sorry some of the questions are like awkward as’ and ‘that caused a big as drama eh’. This intensifier construction has been identified as a distinctive New Zealand English (NZE) innovation, yet little has been written about this it. However, the Waikato MEC corpus presents the opportunity to analyse the construction in a more systematic manner and to fill existing gaps in analyses of Māori English grammar.

year: 2025