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Biomedical subjects

Geoffrey K Chambers

Publications and source records attributed to Geoffrey K Chambers.

6 recordsLinked to original sources
PubMed2006

Natal philopatry does not lead to population genetic differentiation in Buller's albatross (Thalassarche bulleri bulleri).

Genetic variability in the only two existing populations of Buller's albatross (Thalassarche bulleri bulleri) was assessed using six polymorphic microsatellite loci. Large biological samples were obtained from both the Snares (n = 99) and the Solander Islands (n = 27). Several measures of genetic differentiation including F(ST) and R(ST) and a principal coordinates analysis (PCO) suggest a complete absence of genetic structure between three breeding colonies on the Snares Islands, and between them and one breeding colony on the Solander Islands. Mark/recapture studies of recently banded albatross chicks on the Snares found high natal philopatry in T. b. bulleri, but the microsatellite DNA data suggest that sufficient gene flow still occurs between all four breeding colonies to maintain a genetically homogeneous population overall.

Animals↗
PubMed2005

Human evolution in Polynesia.

The number of eastern Polynesian females required to found the Maori population of Aotearoa (New Zealand) has been recalculated. Our estimates use computer simulations that incorporate realistic sigmoid population growth models and include previously published and new mitochondrial DNA (mtDNA) 3' hypervariable region 1 sequences from Măori (N = 109) and other eastern Polynesian (N = 125) volunteers. Approximately 190 (170-230) women are estimated to have been present in the founding waka (canoes). This new figure is more than double the previous estimate (Murray-McIntosh et al. 1998). Our claim for a large Maori founding population fits well with Măori oral history and has additional support from Măori paleodemography studies based on fertility estimates (Brewis et al. 1990; Pool 1991). An increasing body of data, including our own, supports the concept of planned multiple settlement voyages to Aotearoa by Polynesian navigators, leading us to suggest that theories for an "accidental discovery" of Aotearoa can now be completely disregarded. Four rare and novel Măori mtDNA haplotypes have been identified in the present study, but we are unable to assign the immediate origin of Măori to an exact Pacific island "homeland" because these haplotypes are not currently known elsewhere in Polynesia. We also discuss briefly the ultimate origin of all Polynesians (including Măori) in a wider context. In general, we support the emerging consensus for Pacific origins most closely encapsulated by the "slow boat" model (Oppenheimer and Richards 2001a). Previously "competing" models for the settlement of Oceania are seen as extremes in a continuum of possibilities with the slow boat representing an "intermediate" model. We suggest that a complete account is now close, incorporating data from all relevant interdisciplinary fields to provide a "synthetic total evidence theory."

Biological Evolution↗
PubMed2003

The effective mutation rate at Y chromosome short tandem repeats, with application to human population-divergence time.

We estimate an effective mutation rate at an average Y chromosome short-tandem repeat locus as 6.9x10-4 per 25 years, with a standard deviation across loci of 5.7x10-4, using data on microsatellite variation within Y chromosome haplogroups defined by unique-event polymorphisms in populations with documented short-term histories, as well as comparative data on worldwide populations at both the Y chromosome and various autosomal loci. This value is used to estimate the times of the African Bantu expansion, the divergence of Polynesian populations (the Maoris, Cook Islanders, and Samoans), and the origin of Gypsy populations from Bulgaria.

Chromosome Mapping↗
PubMed2002

Combined data, Bayesian phylogenetics, and the origin of the New Zealand cicada genera.

We have applied Bayesian and maximum likelihood methods of phylogenetic estimation to data from four mitochondrial genes (COI, COII, 12S, and 16S) and a single nuclear gene (EF1alpha) from several genera of New Zealand, Australian, and New Caledonian cicada taxa. We specifically focused on the heterogeneity of phylogenetic signal among the different data partitions and the biogeographic origins of the New Zealand cicada fauna. The Bayesian analyses circumvent many of the problems associated with other statistical tests for comparing data partitions. We took an information-theoretic approach to model selection based on the Akaike Information Criterion (AIC). This approach indicated that there was considerable uncertainty in identifying the best-fit model for some of the partitions. Additionally, a large amount of uncertainty was associated with many parameter estimates from the substitution model. However, a sensitivity analysis on the combined dataset indicated that the model selection uncertainty had little effect on estimates of topology because these estimates were largely insensitive to changes in the assumed model. This outcome suggests strong signal in our data. Our analyses support a New Caledonian affiliation of the New Zealand cicada genera Maoricicada, Kikihia, and Rhodopsalta and Australian affinities for the genera Amphipsalta and Notopsalta. This result was surprising, given that previous cicada biologists suspected a close relationship between Amphipsalta, Notopsalta, and Rhodopsalta based on genitalic characters. Relationships among the closely related genera Maoricicada, Kikihia, and Rhodopsalta were poorly resolved, the mitochondrial data and the EF1alpha data favoring different arrangements within this clade.

Animals↗
PubMed2002

The genetics of alcoholism in Polynesians: alcohol and aldehyde dehydrogenase genotypes in young men.

BACKGROUND: The last 10 years have seen growing recognition of the significance of the genes encoding enzymes responsible for hepatic alcohol metabolism as protective factors in the development of alcoholism. METHODS: We have developed DNA sequencing assays for measuring genetic variation at the alcohol dehydrogenase 2 (ADH2), ADH3, and aldehyde dehydrogenase 2 (ALDH2) loci. These have been used to survey volunteer control subjects from three New Zealand ethnic groups (white, Asian, and Polynesian) and young male alcoholics recruited from white and New Zealand Maori patients in a local treatment program. RESULTS: The allele frequency values for whites and Asians obtained in our study closely match those obtained previously in other laboratories. Our data (the first for Polynesians) are 0.42 for ADH2*2, 0.78 for ADH3*1, and 0.00 for ALDH2*2. In the New Zealand Maori alcoholic patients, the ADH2*2 frequency is significantly lower (0.15; p < 0.01). The frequency of ADH3*1 is also lower in this group (0.60), but this value is not significant (0.05 < p < 0.06). CONCLUSIONS: In young male New Zealand Maori, the ADH2*2 allele is a protective factor against alcoholism even in the absence of ALDH2*2.

Alcohol Dehydrogenase↗