title: Genetic diversity and phylogeography of New Zealand and Antarctic arthropods

authors: McGaughran, Angela

abstract: Historical climatic and geological changes and ecological factors ( e.g. population size, dispersal abilities) are conducive to shaping genetic differentiation among natural populations. This thesis examines these issues in a phylogeographic context by looking at patterns of genetic diversity and dispersal of arthropods in two geographic regions. 
In southern New Zealand and its outlying islands, regional genetic divergence was revealed using mtDNA (COi) analysis for populations of idoteid isopods. Divergence within Austridotea benhami was < 2.0%. However, divergence within A. lacustris reached up to 10% with four main groupings: 1) Chatham Islands; 2) Campbell Island; 3) Fiordland; and 4) east coast South Island and Stewart Island. Similarly, A. annectens showed two main groups (4.4% diverg~nt): 1) Chatham Islands; and 2) east coast South Island and Stewart Island. These patterns are likely to be the result of geographical isolation, with some populations showing divergence corresponding to the availability of habitat (e.g. the divergence of A. lacustris and A. annectens on Chatham Islands may relate to the availability of this habitat - 4 Mya). Additionally, divergence of A. lacustris on Campbell Island and Fiordland may indicate a rare founder event or environmental change that resulted in population isolation. Overall, genetic data and geological history indicated that rare dispersal / events (or range expansion and population extinction), particularly during the Pliocene, may have played an important role in shaping the present-day distribution and genetic structure of freshwater idoteid isopods throughout New Zealand and its outlying islands.
In Antarctica, analysis of patterns of mtDNA (COI) diversity and the geographic distribution of haplotypes among populations of the springtail Gomphiocephalus hodgsoni and the mite Stereotydeus mollis also revealed (congruent) patterns of genetic sub-structuring. Furthermore, genetic discontinuities suggested limited dispersal opportunities and isolation-by-distance for these taxa. Haplotype diversity within Wright and Victoria Valleys (St. John's, Olympus and Asgard ranges) was found to be higher here than in other areas and the distribution of haplotypes across sites was very heterogeneous. G. hodgsoni and S. mollis populations harboured eight and 23 new mtDNA haplotypes, respectively and showed links to previously sampled populations across southern Victoria Land. Accordingly, it is possible that this region may represent a primary location of a refugial source population from which many extant populations in southern Victoria Land have expanded since the Pleistocene and Holocene. 
Collectively, these studies revealed limited current dispersal and high levels of regional genetic differentiation for three arthropod taxa from fragmented habitats in both New Zealand and Antarctica. It provided insight into the biogeographic processes underlying modem distribution patterns of these taxa and highlighted the utility of the phylogeographic approach in reconstructing biotic history to further / knowledge of the relationships that exist between population processes and patterns of species diversity. Additionally, genetic analyses such as those performed here provided a basis to re-evaluate populations from a biodiversity perspective. Specifically, the New Zealand study clarified specific and generic relationships for potential reassessment of conservation status, while the Antarctic study identified biodiversity hotspots and priorities for conservation strategies (e.g. specially protected areas).

text: Genetic diversity and phylogeography of New Zealand and Antarctic arthropods Historical climatic and geological changes and ecological factors ( e.g. population size, dispersal abilities) are conducive to shaping genetic differentiation among natural populations. This thesis examines these issues in a phylogeographic context by looking at patterns of genetic diversity and dispersal of arthropods in two geographic regions. 
In southern New Zealand and its outlying islands, regional genetic divergence was revealed using mtDNA (COi) analysis for populations of idoteid isopods. Divergence within Austridotea benhami was < 2.0%. However, divergence within A. lacustris reached up to 10% with four main groupings: 1) Chatham Islands; 2) Campbell Island; 3) Fiordland; and 4) east coast South Island and Stewart Island. Similarly, A. annectens showed two main groups (4.4% diverg~nt): 1) Chatham Islands; and 2) east coast South Island and Stewart Island. These patterns are likely to be the result of geographical isolation, with some populations showing divergence corresponding to the availability of habitat (e.g. the divergence of A. lacustris and A. annectens on Chatham Islands may relate to the availability of this habitat - 4 Mya). Additionally, divergence of A. lacustris on Campbell Island and Fiordland may indicate a rare founder event or environmental change that resulted in population isolation. Overall, genetic data and geological history indicated that rare dispersal / events (or range expansion and population extinction), particularly during the Pliocene, may have played an important role in shaping the present-day distribution and genetic structure of freshwater idoteid isopods throughout New Zealand and its outlying islands.
In Antarctica, analysis of patterns of mtDNA (COI) diversity and the geographic distribution of haplotypes among populations of the springtail Gomphiocephalus hodgsoni and the mite Stereotydeus mollis also revealed (congruent) patterns of genetic sub-structuring. Furthermore, genetic discontinuities suggested limited dispersal opportunities and isolation-by-distance for these taxa. Haplotype diversity within Wright and Victoria Valleys (St. John's, Olympus and Asgard ranges) was found to be higher here than in other areas and the distribution of haplotypes across sites was very heterogeneous. G. hodgsoni and S. mollis populations harboured eight and 23 new mtDNA haplotypes, respectively and showed links to previously sampled populations across southern Victoria Land. Accordingly, it is possible that this region may represent a primary location of a refugial source population from which many extant populations in southern Victoria Land have expanded since the Pleistocene and Holocene. 
Collectively, these studies revealed limited current dispersal and high levels of regional genetic differentiation for three arthropod taxa from fragmented habitats in both New Zealand and Antarctica. It provided insight into the biogeographic processes underlying modem distribution patterns of these taxa and highlighted the utility of the phylogeographic approach in reconstructing biotic history to further / knowledge of the relationships that exist between population processes and patterns of species diversity. Additionally, genetic analyses such as those performed here provided a basis to re-evaluate populations from a biodiversity perspective. Specifically, the New Zealand study clarified specific and generic relationships for potential reassessment of conservation status, while the Antarctic study identified biodiversity hotspots and priorities for conservation strategies (e.g. specially protected areas).

year: 2005

title: Notes on the hydrology of the Waikato River

authors: Ridall, G.T.

subjects: Waikato river

abstract: The catchment area of the Waikato River is 5,500 square miles. If its source is accepted as being the Upper Waikato, then its distance to the sea at Port Waikato including its journey through Lake Taupo is 266 miles. It rises, together with the Whangaehu, the Rangitikei and the Wanganui, between the volcanic region of Ruapehu 9,000 ft. above sea level and the Kaimanawa Ranges 5,000 ft. above sea level.
The river flows northwards for 34 miles into Lake Taupo, losing its identity into the Tongariro for the last 26 miles to the lake. It emerges from Lake Taupo resuming its proper name and, still flowing northwards, passes for more than 100 miles through a series of lakes formed by hydroelectric dams to Cambridge. From here it continues through a deeply incised channel to Ngaruawahia where it is joined by its major tributary, the Waipa River. From Ngaruawahia to the mouth, a distance of 60 miles, shallow lakes and peat swamps predominate on both sides of the river, many of them protected and drained and developed into rich dairy farms. From Mercer, 35 miles downstream of Ngaruawahia, where slight tidal effects are discernable at low flows, the river changes its general northerly direction to a westerly one and, still 9 miles from the mouth, enters the delta. Here it is fragmented into many channels before emptying into the broad expanse of Maioro Bay and finally emerges by two fairly narrow channels into the sea on the west coast, 25 miles south of Manukau Heads.

text: Notes on the hydrology of the Waikato River The catchment area of the Waikato River is 5,500 square miles. If its source is accepted as being the Upper Waikato, then its distance to the sea at Port Waikato including its journey through Lake Taupo is 266 miles. It rises, together with the Whangaehu, the Rangitikei and the Wanganui, between the volcanic region of Ruapehu 9,000 ft. above sea level and the Kaimanawa Ranges 5,000 ft. above sea level.
The river flows northwards for 34 miles into Lake Taupo, losing its identity into the Tongariro for the last 26 miles to the lake. It emerges from Lake Taupo resuming its proper name and, still flowing northwards, passes for more than 100 miles through a series of lakes formed by hydroelectric dams to Cambridge. From here it continues through a deeply incised channel to Ngaruawahia where it is joined by its major tributary, the Waipa River. From Ngaruawahia to the mouth, a distance of 60 miles, shallow lakes and peat swamps predominate on both sides of the river, many of them protected and drained and developed into rich dairy farms. From Mercer, 35 miles downstream of Ngaruawahia, where slight tidal effects are discernable at low flows, the river changes its general northerly direction to a westerly one and, still 9 miles from the mouth, enters the delta. Here it is fragmented into many channels before emptying into the broad expanse of Maioro Bay and finally emerges by two fairly narrow channels into the sea on the west coast, 25 miles south of Manukau Heads.

year: 1967

title: Significance of an early date from an adzed tree stump in Northland

authors: Higham, Thomas F.G.

abstract: Ogle, Jones, Sutton and Wallace (1998) have recently investigated the radiocarbon dating of a tree stump ('Ogle's stump’) which had evidence of adze marks, near the site of Taumatawhana pa, Houhora, Northland. The conventional radiocarbon age of 938 ± 31 BP was obtained at the Institute of Geological and Nuclear Sciences Ltd (formerly INS) laboratory in 1971. Ogle et al.(1998) considered the 'inbuilt age' of the wood (see McFadgen, 1982) and assessed its contribution to the radiocarbon determination. In this brief paper we re-evaluate that methodology and question the conclusion of Ogle et al. (1998) that the date is reliable. We are particularly concerned with the comparison of the date with an associated radiocarbon result obtained by Elliot et al. (1995) from a nearby site at Lake Taumatawhana, which we think is misleading.

text: Significance of an early date from an adzed tree stump in Northland Ogle, Jones, Sutton and Wallace (1998) have recently investigated the radiocarbon dating of a tree stump ('Ogle's stump’) which had evidence of adze marks, near the site of Taumatawhana pa, Houhora, Northland. The conventional radiocarbon age of 938 ± 31 BP was obtained at the Institute of Geological and Nuclear Sciences Ltd (formerly INS) laboratory in 1971. Ogle et al.(1998) considered the 'inbuilt age' of the wood (see McFadgen, 1982) and assessed its contribution to the radiocarbon determination. In this brief paper we re-evaluate that methodology and question the conclusion of Ogle et al. (1998) that the date is reliable. We are particularly concerned with the comparison of the date with an associated radiocarbon result obtained by Elliot et al. (1995) from a nearby site at Lake Taumatawhana, which we think is misleading.

year: 1998