Review. Biogeography of the fauna of French Polynesia: Diversification within and between a series of hot spot archipelagos

Department of Environmental Science, University of California, 137 Mulford Hall, Berkeley, CA 94720-3114, USA.
Philosophical Transactions of The Royal Society B Biological Sciences (Impact Factor: 7.06). 11/2008; 363(1508):3335-46. DOI: 10.1098/rstb.2008.0124
Source: PubMed


The islands of French Polynesia cover an area the size of Europe, though total land area is smaller than Rhode Island. Each hot spot archipelago (Societies, Marquesas, Australs) is chronologically arranged. With the advent of molecular techniques, relatively precise estimations of timing and source of colonization have become feasible. We compile data for the region, first examining colonization (some lineages dispersed from the west, others from the east). Within archipelagos, blackflies (Simulium) provide the best example of adaptive radiation in the Societies, though a similar radiation occurs in weevils (Rhyncogonus). Both lineages indicate that Tahiti hosts the highest diversity. The more remote Marquesas show clear examples of adaptive radiation in birds, arthropods and snails. The Austral Islands, though generally depauperate, host astonishing diversity on the single island of Rapa, while lineages on other islands are generally widespread but with large genetic distances between islands. More recent human colonization has changed the face of Polynesian biogeography. Molecular markers highlight the rapidity of Polynesian human (plus commensal) migrations and the importance of admixture from other populations during the period of prehistoric human voyages. However, recent increase in traffic has brought many new, invasive species to the region, with the future of the indigenous biota uncertain.

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Available from: Rosemary G Gillespie, May 09, 2014
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    • "Some hotspot volcanic archipelagos, such as Hawaii, Australs, and Marquesas, are arranged linearly by the age of emergence of islands. In such archipelagos, colonization patterns may follow a progression rule, reflecting the successive colonization of islands in the order of their formation (Funk and Wagner 1995; Gillespie et al. 2008). The colonization pattern can be less evident in archipelagos with a more complex geological history, such as the Azores (Amorim et al. 2012), Canaries (Sanmart ın et al. 2008), Cape Verde (Carranza et al. 2001), or Galapagos (Sequeira et al. 2008). "
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    ABSTRACT: A key challenge in island biogeography is to quantity the role of dispersal in shaping biodiversity patterns among the islands of a given archipelago. Here, we propose such a framework. Dispersal within oceanic archipelagos may be conceptualized as a spatio-temporal process dependent on: (1) the spatial distribution of islands, because the probability of successful dispersal is inversely related to the spatial distance between islands and (2) the chronological sequence of island formation that determines the directional asymmetry of dispersal (hypothesized to be predominantly from older to younger islands). From these premises, directional network models may be constructed, representing putative connections among islands. These models may be translated to eigenfunctions in order to be incorporated into statistical analysis. The framework was tested with 12 datasets from the Hawaii, Azores, and Canaries. The explanatory power of directional network models for explaining species composition patterns, assessed by the Jaccard dissimilarity index, was compared with simpler time-isolation models. The amount of variation explained by the network models ranged from 5.5% (for Coleoptera in Hawaii) to 60.2% (for Pteridophytes in Canary Islands). In relation to the four studied taxa, the variation explained by network models was higher for Pteridophytes in the three archipelagos. By the contrary, small fractions of explained variation were observed for Coleoptera (5.5%) and Araneae (8.6%) in Hawaii. Time-isolation models were, in general, not statistical significant and explained less variation than the equivalent directional network models for all the datasets. Directional network models provide a way for evaluating the spatio-temporal signature of species dispersal. The method allows building scenarios against which hypotheses about dispersal within archipelagos may be tested. The new framework may help to uncover the pathways via which species have colonized the islands of a given archipelago and to understand the origins of insular biodiversity
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    • "A comprehensive understanding of partulid diversification processes requires not only a range-wide perspective, but also the development of finer scale within-archipelago and within-island phylogenies. This has been best developed for the Society Island radiation where a number of workers have proposed a “progression rule” model of evolution – lineages sequentially colonize newer islands within an archipelago as they are formed [4] - for the well-studied Partula species of Moorea and Tahiti [43,46,49-53]. In this model, neighboring older islands (Leeward group) seeded the younger islands (Windward group), first Moorea, then Tahiti, via single colonization events and subsequent speciation occurred in situ within each island [43,46,49-53]. "
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    ABSTRACT: Background: Partulid tree snails are endemic to Pacific high islands and have experienced extraordinary rates of extinction in recent decades. Although they collectively range across a 10,000 km swath of Oceania, half of the family's total species diversity is endemic to a single Eastern Pacific hot spot archipelago (the Society Islands) and all three partulid genera display highly distinctive distributions. Our goal was to investigate broad scale (range wide) and fine scale (within-Society Islands) molecular phylogenetic relationships of the two widespread genera, Partula and Samoana. What can such data tell us regarding the genesis of such divergent generic distribution patterns, and nominal species diversity levels across Oceania? Results: Museum, captive (zoo) and contemporary field specimens enabled us to genotype 54 of the ~120 recognized species, including many extinct or extirpated taxa, from 14 archipelagoes. The genera Partula and Samoana are products of very distinct diversification processes. Originating at the western edge of the familial range, the derived genus Samoana is a relatively recent arrival in the far eastern archipelagoes (Society, Austral, Marquesas) where it exhibits a stepping-stone phylogenetic pattern and has proven adept at both intra-and inter- archipelago colonization. The pronounced east-west geographic disjunction exhibited by the genus Partula stems from a much older long-distance dispersal event and its high taxonomic diversity in the Society Islands is a product of a long history of within-archipelago diversification. Conclusions: The central importance of isolation for partulid lineage persistence and diversification is evident in time-calibrated phylogenetic trees that show that remote archipelagoes least impacted by continental biotas bear the oldest clades and/or the most speciose radiations. In contemporary Oceania, that isolation is being progressively undermined and these tree snails are now directly exposed to introduced continental predators throughout the family's range. Persistence of partulids in the wild will require proactive exclusion of alien predators in at least some designated refuge islands.
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    • "All other entimine radiations studied on oceanic islands to date involve flightless lineages. These include Syzygops on the Mascarene Islands (Williams 2000), Laparocerus within Macaronesia (Machado 2006, 2007a,b, 2008; Machado et al. 2008), Rhyncogonus within Polynesia (Gillespie et al. 2008), Ectemnorhinus of the Prince Edward Islands (Grobler et al. 2006) and Galapaganus from the Galapagos Islands (Sequeira et al. 2008). While geographical isolation within islands has apparently acted to facilitate speciation within island invertebrate radiations (e.g. "
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    ABSTRACT: The phytophagous beetle family Curculionidae is the most species-rich insect family known, with much of this diversity having been attributed to both co-evolution with food plants and host shifts at key points within the early evolutionary history of the group. Less well understood is the extent to which patterns of host use vary within or among related species, largely because of the technical difficulties associated with quantifying this. Here we develop a recently characterized molecular approach to quantify diet within and between two closely related species of weevil occurring primarily within dry forests on the island of Mauritius. Our aim is to quantify dietary variation across populations and assess adaptive and nonadaptive explanations for this and to characterize the nature of a trophic shift within an ecologically distinct population within one of the species. We find that our study species are polyphagous, consuming a much wider range of plants than would be suggested by the literature. Our data suggest that local diet variation is largely explained by food availability, and locally specialist populations consume food plants that are not phylogenetically novel, but do appear to represent a novel preference. Our results demonstrate the power of molecular methods to unambiguously quantify dietary variation across populations of insect herbivores, providing a valuable approach to understanding trophic interactions within and among local plant and insect herbivore communities.
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