The genetic structure of Pacific Islanders

Human genetic diversity in the Pacific has not been adequately sampled, particularly in Melanesia. As a result, population relationships there have been open to debate. A genome scan of autosomal markers (687 microsatellites and 203 insertions/deletions) on 952 individuals from 41 Pacific populations now provides the basis for understanding the remarkable nature of Melanesian variation, and for a more accurate comparison of these Pacific populations with previously studied groups from other regions. It also shows how textured human population variation can be in particular circumstances. Genetic diversity within individual Pacific populations is shown to be very low, while differentiation among Melanesian groups is high. Melanesian differentiation varies not only between islands, but also by island size and topographical complexity. The greatest distinctions are among the isolated groups in large island interiors, which are also the most internally homogeneous. The pattern loosely tracks language distinctions. Papuan-speaking groups are the most differentiated, and Austronesian or Oceanic-speaking groups, which tend to live along the coastlines, are more intermixed. A small “Austronesian” genetic signature (always <20%) was detected in less than half the Melanesian groups that speak Austronesian languages, and is entirely lacking in Papuan-speaking groups. Although the Polynesians are also distinctive, they tend to cluster with Micronesians, Taiwan Aborigines, and East Asians, and not Melanesians. These findings contribute to a resolution to the debates over Polynesian origins and their past interactions with Melanesians. With regard to genetics, the earlier studies had heavily relied on the evidence from single locus mitochondrial DNA or Y chromosome variation. Neither of these provided an unequivocal signal of phylogenetic relations or population intermixture proportions in the Pacific. Our analysis indicates the ancestors of Polynesians moved through Melanesia relatively rapidly and only intermixed to a very modest degree with the indigenous populations there.     

The impact of the Austronesian expansion: evidence from mtDNA and Y chromosome diversity in the Admiralty Islands of Melanesia

The genetic ancestry of Polynesians can be traced to both Asia and Melanesia, which presumably reflects admixture occurring between incoming Austronesians and resident non-Austronesians in Melanesia before the subsequent occupation of the greater Pacific; however, the genetic impact of the Austronesian expansion to Melanesia remains largely unknown. We therefore studied the diversity of nonrecombining Y chromosomal (NRY) and mitochondrial (mt) DNA in the Admiralty Islands, located north of mainland Papua New Guinea, and updated our previous data from Asia, Melanesia, and Polynesia with new NRY markers. The Admiralties are occupied today solely by Austronesian-speaking groups, but their human settlement history goes back 20,000 years prior to the arrival of Austronesians about 3,400 years ago. On the Admiralties, we found substantial mtDNA and NRY variation of both Austronesian and non-Austronesian origins, with higher frequencies of Asian mtDNA and Melanesian NRY haplogroups, similar to previous findings in Polynesia and perhaps as a consequence of Austronesian matrilocality. Thus, the Austronesian language replacement on the Admiralties (and elsewhere in Island Melanesia and coastal New Guinea) was accompanied by an incomplete genetic replacement that is more associated with mtDNA than with NRY diversity. These results provide further support for the "Slow Boat" model of Polynesian origins, according to which Polynesian ancestors originated from East Asia but genetically mixed with Melanesians before colonizing the Pacific. We also observed that non-Austronesian groups of coastal New Guinea and Island Melanesia had significantly higher frequencies of Asian mtDNA haplogroups than of Asian NRY haplogroups, suggesting sex-biased admixture perhaps as a consequence of non-Austronesian patrilocality. We additionally found that the predominant NRY haplogroup of Asian origin in the Admiralties (O-M110) likely originated in Taiwan, thus providing the first direct Y chromosome evidence for a Taiwanese origin of the Austronesian expansion. Furthermore, we identified a NRY haplogroup (K-P79, also found on the Admiralties) in Polynesians that most likely arose in the Bismarck Archipelago, providing the first direct link between northern Island Melanesia and Polynesia. These results significantly advance our understanding of the impact of the Austronesian expansion and human history in the Pacific region.     

The origins of subsistence agriculture in Oceania and the potentials for future tropical food crops

Subsistence agriculture in the Pacific Islands has a complex prehistory centered on western Melanesia. Based on an analysis of cultigen provenience, a sequential model of a three-tiered crop structure of indigenous agricultural systems has been derived: (1) The independent early domestication of endemic species in the New Guinea region; (2) introduction of species from Southeast Asia; (3) the advent of American crop plants. The temporal sequence has archaeological and linguistic confirmation of 10 000 years ago for the beginnings of agriculture, 6000 years for Southeast Asian introduction, with the sweet potato contributing in Polynesia in prehistory, and in Melanesia only in post-Columbian times. Recent research directed toward issues of domestication in New Guinea and subsistence prehistory in Australia on three genera,Canarium, Colocasia andIpomoea, exemplify under-recognized resources with quite different potentials for economic botany. Unlike past exploitation of indigenous plant resources, future users of plants such as those exemplified, and especially where commercialization is involved, cannot avoid addressing intellectual property rights that pertain to species domesticated, selected or conserved by peoples of the non-industri-alized world.     

Affinities among Melanesians,Micronesians, and Polynesians: a neutral biparental genetic perspective

The human colonization of Remote Oceania, the vast Pacific region including Micronesia, Polynesia, and Melanesia beyond the northern Solomon Islands, ranks as one of the greatest achievements of prehistory. Many aspects of human diversity have been examined in an effort to reconstruct this late Holocene expansion. Archaeolinguistic analyses describe a rapid expansion of Austronesian-speaking "Lapita people" from Taiwan out into the Pacific. Analyses of biological markers, however, indicate genetic contributions from Pleistocene-settled Near Oceania into Micronesia and Polynesia, and genetic continuity across Melanesia. Thus, conflicts between archaeolinguistic and biological patterns suggest either linguistic diffusion or gene flow across linguistic barriers throughout Melanesia. To evaluate these hypotheses and the general utility of linguistic patterns for conceptualizing Pacific prehistory, we analyzed 14 neutral, biparental genetic (short tandem repeat) loci from 965 individuals representing 27 island Southeast Asian, Melanesian, Micronesian, and Polynesian populations. Population bottlenecks during the colonization of Remote Oceania are indicated by a statistically significant regression of loss of heterozygosity on migration distance from island Southeast Asia (r = 0.78, p < 0.001). Genetic and geographic distances were consistently correlated (r > 0.35, p < 0.006), indicating extensive gene flow primarily focused among neighboring populations. Significant correlations between linguistic and geographic patterns and between genetic and linguistic patterns depended upon the inclusion of Papuan speakers in the analyses. These results are consistent with an expansion of Austronesian-speaking populations out of island Southeast Asia and into Remote Oceania, followed by substantial gene flow from Near Oceanic populations. Although linguistic and genetic distinctions correspond at times, particularly between Western and Central-Eastern Micronesia, gene flow has reduced the utility of linguistic data within Melanesia. Overall, geographic proximity is a better predictor of biparental genetic relationships than linguistic affinities.     

Pollen as the link between floral phenotype and fitness

Pollen plays a key role in plant reproductive biology. Despite the long history of research on pollen and pollination, recent advances in pollen-tracking methods and statistical approaches to linking plant phenotype, pollination performance, and reproductive fitness yield a steady flow of exciting new insights. In this introduction to the Special Issue “Pollen as the Link Between Phenotype and Fitness,” we start by describing a general conceptual model linking functional classes of floral phenotypic traits to pollination-related performance metrics and reproductive fitness. We use this model as a framework for synthesizing the relevant literature, highlighting the studies included in the Special Issue, and identifying gaps in our understanding and opportunities for further development of the field. The papers that follow in this Special Issue provide new insights into the relationships between pollen production, presentation, flower morphology, and pollination performance (e.g., pollen deposition onto stigmas), the role of pollinators in pollen transfer, and the consequences of heterospecific pollen deposition. Several of the studies demonstrate exciting experimental and analytical approaches that should pave the way for continued work addressing the intriguing role of pollen in linking plant phenotypes to reproductive fitness.     

The colonization of the Pacific: the story according to human leukocyte antigens.

The human leukocyte antigen (HLA) distributions in 16 Pacific populations have been collated from published and unpublished reports. Gene frequency and linkage disequilibrium relationships among groups show that Australians and Papuans share a common ancestry, that coastal Melanesia has about 16% Austronesian admixture, and that Fiji is truly intermediate between Melanesia and Polynesia. In Polynesia, Cook Islanders show closer affinity with populations of Western Polynesia than with Maoris and Easter Islanders, in contrast to their linguistic affiliations, but otherwise HLA distributions show a clear division between the populations of Eastern and Western Polynesia. This study emphasizes the contribution the HLA system can make to anthropological studies and has provided a version of colonization of the Pacific compatible with theories based on prodigious efforts in many disciplines.     

A new species of Procamallanus (Nematoda: Camallanidae) from Pacific eels (Anguilla spp.)

A new species of parasitic nematode, Procamallanus (Procamallanus) pacificus n. sp., is described from the stomach of the Pacific shortfinned eel, Anguilla obscura (type host), and from the speckled longfin eel, Anguilla reinhardtii, from northern New Caledonia (Melanesia, South Pacific); from Anguilla sp. (cf. obscura) from the Fiji Islands (Melanesia, South Pacific); and from the giant mottled eel Anguilla marmorata from Futuna Island (Wallis and Futuna Islands, Polynesia). Although a total of 450 nematodes were collected, all specimens were females; this suggests either an extremely rare occurrence of males or parthenogenetic reproduction in this species. Procamallanus pacificus differs markedly from all congeners from fish hosts in possessing a greater number (4-9) of caudal mucrons in the female and by other morphological features. This parasite might become a serious pathogen of cultured eels in the region of the South Pacific. Batrachocamallanus Jackson and Tinsley, 1995 is considered a junior synonym of Procamallanus Baylis, 1923, to which 2 species are transferred as Procamallanus occidentalis (Jackson and Tinsley, 1995) n. comb. and Procamallanus siluranae (Jackson and Tinsley, 1995) n. comb. One third-stage larva of Procamallanus (Spirocamallanus) sp. was also recorded from Anguilla sp. (cf. obscura) from the Fiji Islands.     

A cautionary tale on ancient migration detection: mitochondrial DNA variation in Santa Cruz Islands,Solomon Islands

Over the past decade, the origin of the first Malayo-Polynesian settlers of the island Pacific has become a contentious issue in molecular anthropology as well as in archaeology and historical linguistics. Whether the descendants of the ancestral Malayo-Polynesian speakers moved rapidly through Indonesia and Island Melanesia in a few hundred years, or whether they were the product of considerable intermingling within the more westerly part of the latter region, it is widely accepted that they were the first humans to colonize the distant Pacific islands beyond the central Solomon Islands approximately 3,000 years ago. The Santa Cruz Islands in the Eastern Solomons would have most likely been the first in Remote Oceania to be colonized by them. Archaeologically, the first Oceanic Austronesian settlement of this region appears to have been overlain by various later influences from groups farther west in a complex manner. Molecular anthropologists have tended to equate the spread of various Austronesian-speaking groups with a particular mitochondrial variant (a 9-base-pair [bp] deletion with specific D-loop variants). We have shown before that this is an oversimplified picture, and assumed that the Santa Cruz situation, with its series of intrusions, would be informative as to the power of mitochondrial DNA haplotype interpretations. In the Santa Cruz Islands, the 9-bp deletion is associated with a small number of very closely related hypervariable D-loop haplotypes resulting in a star-shaped Bandelt median network, suggesting a recent population expansion. This network is similar to Polynesian median networks. In a pairwise mismatch comparison, the Santa Cruz haplotypes have a bimodal distribution, with the first cluster being composed almost entirely of the 9-bp-deleted haplotypes-again attesting to their recent origins. Conversely, the nondeleted haplogroups bear signatures of more ancient origins within the general region. Therefore, while the profiles of the two sets of haplotypes indicate very distinctive origins in different populations with divergent expansion histories, the sequence of their introduction into the Santa Cruz Islands clearly does not follow simply.     

Introduction: Culture Without Cultures—The Culture Effect

Anthropology has often been handmaiden to administrative and political activity that requires bounded social groups mapped onto territories and possessing defining characteristics such as language, values and behaviours. This introductory essay sets the scene for the papers in this Issue which show that actual sets of social relations in their particular places cannot easily be made to conform with this hermetic construct. Acknowledging this, post‐colonial theory has been driven to theorise borderlands, hybridisation and metissage, liminal and interstitial social spaces. Yet these necessarily reinforce and privilege primary concepts of the pure and the central, the bounded and situated. This paper places the hermetic view of culture in its formative period, which also saw the emergence of nationalism and scientific atomism. The paper proposes that positing pure and bounded cultures, even as an idealised abstraction, is an error of theory which is influenced by an attachment to metaphors of the material world, usually ‘Euclidean’. Finally, the paper explores ways that analyses of cultural interrelation, such as those in this Special Issue, can proceed without imagining a resulting ‘culture’, and what this may do for the political landscape of localised cultural rights.     

Biogeographic anomaly or human introduction: a cryptogenic population of tree skink (Reptilia: Squamata) from the Cook Islands,Oceania

Archaeological and molecular data have revealed that the present day faunas of many island groups in Melanesia, Polynesia, and Micronesia are not representative of the biodiversity generated within this region on an evolutionary timescale. Erroneous inferences regarding the mechanisms of speciation and the significance of long distance dispersal in shaping the present diversity of these island systems have resulted from this incomplete diversity and distributional data. The lizard fauna east of Samoa has been suggested to derive entirely from human‐mediated introductions, a distribution congruent with biogeographic patterns for other Pacific species. Distinguishing between introduced populations and those that result from natural colonization events is difficult, although molecular data provide a useful means for elucidating population history and identifying the likely sources of introductions. We use molecular data (1726 bp of mitochondrial DNA and 286 bp of nuclear DNA) to evaluate a population of arboreal lizards from the Cook Islands and to determine whether this arboreal skink population is the sole endemic component of the lizard fauna east of Samoa or the result of human‐mediated introduction. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 318–328.     

Freezer anthropology: new uses for old blood

Archived blood fractions (plasma, settled red cells, white cells) have proved to be a rich and valuable source of DNA for human genetic studies. Large numbers of such samples were collected between 1960 and the present for protein and blood group studies, many of which are languishing in freezers or have already been discarded. More are discarded each year because the usefulness of these samples is not widely understood. Data from DNA derived from 10-35-year-old blood samples have been used to address the peopling of the New World and of the Pacific. Mitochondrial DNA haplotypes from studies using this source DNA support a single wave of migration into the New World (or a single source population for the New World), and that Mongolia was the likely source of the founding population. Data from Melanesia have shown that Polynesians are recent immigrants into the Pacific and did not arise from Melanesia.     

Sharpening the focus; the business of epithelial cell biology. An interview with Chris Potten by David Pearton

Dr Chris Potten is a singularly influential figure in the field of epithelial biology. His contributions have been seminal and include the introduction of the epidermal proliferative unit and of the concept of epidermal stem cells. With around 400 scientific papers and reviews to his credit as well as two books, he has certainly made his mark. His contributions have been recognised by the award of the Curie medal and recently the Weiss medal for radiation biology. Dr. Potten graciously agreed to be interviewed for this Special Issue of The International Journal of Developmental Biology. This interview was conducted via e-mail during June -August 2003.     

Recovering threatened plant species and their habitats: The need for integrated action

As an introduction to the Special Issue on the restoration of threatened plant species and their habitats,this editorial shows how the various papers in the issue address the range of in situ interventions involved in species population management and restoration of their habitat, together with examples of case studies implementing these actions. It stresses the need for integrating these various interventions.It highlights the importance of protected areas in providing a degree of protection for threatened species but also the need to complement this with actions at the species level to ensure the effective conservation and long term persistence of these species. It emphasizes that ecological restoration is a complement to, not a substitute for conservation, and that the balance of effort and allocation of resources between them is a key issue.     

Evolutionary approaches to cultural and linguistic diversity

Evolutionary approaches to cultural change are increasingly influential, and many scientists believe that a 'grand synthesis' is now in sight. The papers in this Theme Issue, which derives from a symposium held by the AHRC Centre for the Evolution of Cultural Diversity (University College London) in December 2008, focus on how the phylogenetic tree-building and network-based techniques used to estimate descent relationships in biology can be adapted to reconstruct cultural histories, where some degree of inter-societal diffusion will almost inevitably be superimposed on any deeper signal of a historical branching process. The disciplines represented include the three most purely 'cultural' fields from the four-field model of anthropology (cultural anthropology, archaeology and linguistic anthropology). In this short introduction, some context is provided from the history of anthropology, and key issues raised by the papers are highlighted.     

Use of the sago palmMetroxylon warburgii in the Polynesian Island,Rotuma

The manufacture of edible starch products from sago palms of the genus Metroxylon is common to indigenous people throughout Melanesia but is unknown in Polynesia, even in areas where Metroxylon species occur. We here report the use of Metroxylon as a starch source in the isolated Polynesian island of Rotuma. In Rotuma, Metroxylon warburgii (Heim) Beccari grows wild, but is likely the result of an aboriginal introduction from Melanesia. Samoan ethnohistorical accounts indicate that Metroxylon warburgii was introduced to Samoa from Rotuma. Rotuman manufacture of starch from M. warburgii appears to date from pre-European times as indicated by written accounts of early visitors to Rotuma and Rotuman oral histories. We provide details of the process of starch manufacture in Rotuma and speculate on possible means by which this technology was transferred from Melanesia to Rotuma.     

Melanesian origin of Polynesian Y chromosomes

BACKGROUND: Two competing hypotheses for the origins of Polynesians are the 'express-train' model, which supposes a recent and rapid expansion of Polynesian ancestors from Asia/Taiwan via coastal and island Melanesia, and the 'entangled-bank' model, which supposes a long history of cultural and genetic interactions among Southeast Asians, Melanesians and Polynesians. Most genetic data, especially analyses of mitochondrial DNA (mtDNA) variation, support the express-train model, as does linguistic and archaeological evidence. Here, we used Y-chromosome polymorphisms to investigate the origins of Polynesians. RESULTS: We analysed eight single nucleotide polymorphisms (SNPs) and seven short tandem repeat (STR) loci on the Y chromosome in 28 Cook Islanders from Polynesia and 583 males from 17 Melanesian, Asian and Australian populations. We found that all Polynesians belong to just three Y-chromosome haplotypes, as defined by unique event polymorphisms. The major Y haplotype in Polynesians (82% frequency) was restricted to Melanesia and eastern Indonesia and most probably arose in Melanesia. Coalescence analysis of associated Y-STR haplotypes showed evidence of a population expansion in Polynesians, beginning about 2,200 years ago. The other two Polynesian Y haplotypes were widespread in Asia but were also found in Melanesia. CONCLUSIONS: All Polynesian Y chromosomes can be traced back to Melanesia, although some of these Y-chromosome types originated in Asia. Together with other genetic and cultural evidence, we propose a new model of Polynesian origins that we call the 'slow-boat' model: Polynesian ancestors did originate from Asia/Taiwan but did not move rapidly through Melanesia; rather, they interacted with and mixed extensively with Melanesians, leaving behind their genes and incorporating many Melanesian genes before colonising the Pacific.     

Phylogeny and systematics of Melanesia’s most diverse gecko lineage (Cyrtodactylus,Gekkonidae, Squamata)

Oliver, P.M., Richards, S.J. & Sistrom, M. (2012). Phylogeny and systematics of Melanesia’s most diverse gecko lineage (Cyrtodactylus, Gekkonidae, Squamata). —Zoologica Scripta, 41, 437–454. The systematics and biogeographical history of the diverse fauna of New Guinea and surrounding islands (Melanesia) remain poorly known. We present a phylogeny for 16 of the 21 recognised Melanesian bent‐toed geckos in the genus Cyrtodactylus based on mitochondrial sequence data. These analyses reveal two divergent lineages of Cyrtodactylus within Melanesia. One includes a single recognised species with clear affinities to sampled taxa from Asia. The other comprises a relatively diverse radiation (likely 30+ species), not closely related to sampled extralimital taxa and centred on the Melanesian region (including Australia). Many taxa within this second lineage are endemic to islands surrounding New Guinea, and dispersal and speciation on peripheral islands appears to have played an important role in the accumulation of species diversity within this clade. In contrast, little diversity is centred upon montane areas, although we do identify at least one lineage closely associated with hill and lower montane forest that probably dates to at least the late Miocene. Our phylogenetic analyses also reveal numerous divergent lineages that require taxonomic attention, including at least two widespread taxa that are likely to be composite, additional specimens of Cyrtodactylus capreoloides (until recently known only from the holotype) and several divergent and completely novel lineages, two of which we introduce herein: Cyrtodactylus arcanus sp. n. and Cyrtodactylus medioclivus sp. n.     

Bioindication and Functional Response in Floodplain Systems: Where to from Here?

We synthesise the results of the papers in this Special Issue, place them within the context of current trends in floodplain research, and outline promising new avenues that emerge from the contributions. The indication system presented complements existing approaches by focussing on a quantitative indication of environmental parameters. A promising research line that emerges is an extension of the systematic comparison of taxonomic groups with contrasting traits in terms of their performance as quantitative indicators for different environmental parameters. The studies show similarities and dissimilarities in the traits explaining the functional response of plants, molluscs, carabids, and syrphids to site conditions but trait databases and studies on additional taxa are required before broad generalisations can be made. The rigorous study design developed for the RIVA project, of which all contributions in this Special Issue are a part, not only was essential for an improvement of the understanding of species environment relationships and the role biological traits play for it, it also provides a baseline for assessing future change as part of long‐term ecological monitoring of floodplains. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Clutch size in the tropical scincid lizard Emoia sanfordi, a species endemic to the Vanuatu Archipelago

The majority of species in the scincid genus Emoia (Squamata: Scincidae) have a fixed clutch size of two eggs per clutch and produce between two and four clutches per year. One lineage within Emoia, the Emoia samoensis species group, consists of 13 species occurring in Melanesia and the islands of the southwestern Pacific Ocean, and exhibits variation in clutch size, with previously reported clutch sizes of two to five eggs. Little is known about reproduction in several members of this lineage including Emoia sanfordi, a large-bodied lizard endemic to the archipelago of Vanuatu in the South Pacific. We analyzed reproduction and clutch size in E. sanfordi females and discovered that there is a substantial amount of intraspecific variation, with clutch size ranging from two to seven eggs, with a modal clutch size of five eggs. Females were reproductively active throughout the study period of June through October and appear to be laying multiple clutches. The variation in clutch size seen in E. sanfordi is congruent with the variation previously reported within other closely related species.