Genetic diversity and differentiation processes in the ploidy series of Olea europaea L.: a multiscale approach from subspecies to insular populations

Geographical isolation and polyploidization are central concepts in plant evolution. The hierarchical organization of archipelagos in this study provides a framework for testing the evolutionary consequences for polyploid taxa and populations occurring in isolation. Using amplified fragment length polymorphism and simple sequence repeat markers, we determined the genetic diversity and differentiation patterns at three levels of geographical isolation in Olea europaea : mainland-archipelagos, islands within an archipelago, and populations within an island. At the subspecies scale, the hexaploid ssp. maroccana (southwest Morocco) exhibited higher genetic diversity than the insular counterparts. In contrast, the tetraploid ssp. cerasiformis (Madeira) displayed values similar to those obtained for the diploid ssp. guanchica (Canary Islands). Geographical isolation was associated with a high genetic differentiation at this scale. In the Canarian archipelago, the stepping-stone model of differentiation suggested in a previous study was partially supported. Within the western lineage, an east-to-west differentiation pattern was confirmed. Conversely, the easternmost populations were more related to the mainland ssp. europaea than to the western guanchica lineage. Genetic diversity across the Canarian archipelago was significantly correlated with the date of the last volcanic activity in the area/island where each population occurs. At the island scale, this pattern was not confirmed in older islands (Tenerife and Madeira), where populations were genetically homogeneous. In contrast, founder effects resulted in low genetic diversity and marked genetic differentiation among populations of the youngest island, La Palma.     

Facies analysis of lower permian platform carbonates,sverdrup basin,canadian arctic archipelago

Summary The Asselian-Sakmarian strata of the Fosheim-Hamilton subbasin represent a distinct 15 000 km² depocentre located at the northeast margin of the main Sverdrup Basin in the Canadian Arctic Archipelago. Approximately 35 high-frequency cycles composed mainly of platformal carbonates with subaqueous evaporites accumulated at a time of renewed rifting activity in this subbasin. A general depositional model based on the facies analysis of the Asselian-Sakmarian strata shows that the carbonate platforms surrounding the Fosheim-Hamilton subbasin were segmented by the position of critical interfaces including the: 1) base of the fairweather wave abrasion zone; 2) base of the storm wave abrasion zone; and 3) base of the photic zone. The base of the fairweather wave abrasion zone divided the platforms into two broad parts; an inner shelf with a relatively quiet, semi-restricted lagoon and more agitated, open marine barries and shoals and an open marine mid-shelf with numerous reefal and non-reefal subenvironments extending from the base of fairweather wave abrasion zone to below the photic zone. Outer shelf and associated slope and basin were not present within the Fosheim-Hamilton subbasin but were present farther west along the margin of the main Sverdrup Basin.     

Zoogeography of Pacific Ocean islands: a comparison of the rotifer faunas of Easter Island and the Galápagos archipelago

During September 1990, an extensive sampling of the freshwaters of Easter Island was conducted. The resulting list of rotifer species, supplemented by taxa present in samples collected during a previous trip to the island, is compared with that of another oceanic island of volcanic origin, namely Santa Cruz, Galápagos archipelago. In spite of less research, Santa Cruz has a richer rotifer fauna which, unlike Easter Island, includes endemic species. Possible causes for the faunal poverty of Easter Island are: large source-to-target distance, small target size, uniformity of the target island's ecosystems and limited age of its aquatic biotopes.     

Island hopping across the central Pacific: mitochondrial DNA detects sequential colonization of the Austral Islands by crab spiders (Araneae: Thomisidae)

Aim Phylogenetic studies concerning island biogeography have been concentrated in a fraction of the numerous hot‐spot archipelagos contained within the Pacific Ocean. In this study we investigate relationships among island populations of the thomisid spider Misumenops rapaensis Berland, 1934 across the Austral Islands, a remote and rarely examined southern Pacific hot‐spot archipelago. We also assess the phylogenetic position of M. rapaensis in relation to thomisids distributed across multiple Polynesian archipelagos in order to evaluate the proposed hypothesis that thomisid spiders colonized Polynesia from multiple and opposing directions. The data allow an examination of genetic divergence and species accumulation in closely related lineages distributed across four Polynesian archipelagos. Location The study focused on four Polynesian hot‐spot archipelagos: the Austral, Hawaiian, Marquesan and Society islands. Methods Mitochondrial DNA sequences comprising c. 1400 bp (portions of cytochrome oxidase subunit I, ribosomal 16S and NADH dehydrogenase subunit I) were obtained from thomisid spiders (64 specimens, representing 33 species) collected in the Australs, the Hawaiian Islands, the Society Islands, the Marquesas, Tonga, Fiji, New Zealand, New Caledonia and North and South America. Phylogenetic analyses using parsimony, maximum‐likelihood and Bayesian approaches were employed to resolve relationships of M. rapaensis to other Polynesian Misumenops and across the Austral Islands. Results Rather than grouping with other Misumenops spp. from the archipelagos of the Society Islands, Marquesas and Hawaiian Islands, M. rapaensis appears more closely related to Diaea spp. from Tonga, Fiji, New Zealand and New Caledonia. Phylogenetic analyses strongly support M. rapaensis as monophyletic across the Austral Islands. Misumenops rapaensis sampled from the two older islands (Rurutu and Tubuai) form reciprocally monophyletic groups, while individuals from the younger islands (Raivavae and Rapa) are paraphyletic. Across the Austral Islands, M. rapaensis exhibits a surprising level of genetic divergence (maximally 11.3%), an amount nearly equivalent to that found across the 16 examined Hawaiian species (14.0%). Main conclusions Although described as a single morphologically recognized species, our results suggest that M. rapaensis comprises multiple genetically distinct lineages restricted to different Austral Islands. Phylogenetic relationships among the island populations are consistent with sequential colonization of this lineage down the Austral archipelago toward younger islands. Analyses support the hypothesis that thomisid spiders colonized the central Pacific multiple times and suggest that M. rapaensis arrived in the Austral Islands from a westward direction, while Misumenops found in neighbouring archipelagos appear to be more closely related to New World congeners to the east. Finally, our data detect asymmetrical rates of morphological evolution and species diversification following colonization of four different Polynesian archipelagos.     

Effects of ship traffic on archipelago waters off the Långnäs harbour in Åland,SW Finland

The relatively shallow archipelago waters off the Långnäs harbour area, eastern Åland (SW Finland) were studied before and after an expansion of the ferry traffic on July 1, 1999. The large ships (150–200 m long) caused increased vertical mixing, turbidity and stirring of the sediments, especially in the turning area outside the harbour. The vertical distribution of silicate as well as disturbed temperature conditions indicated artificial upwelling. Ship traffic also contributes to the eutrophication of the archipelago waters via increased recycling of nutrients due to elevated bottom temperature and increased mixing depth in the fairway. As the bloom-forming cyanobacterium Nodularia spumigena could be favoured in the fairway or adjacent areas, the occurrence of its toxin nodularin-R was monitored. However, only low toxin concentrations were recorded in the whole study area in 1999.     

Biogeographic,climatic and spatial drivers differentially affect α-, β- and γ-diversities on oceanic archipelagos

Island biogeographic studies traditionally treat single islands as units of analysis. This ignores the fact that most islands are spatially nested within archipelagos. Here, we took a fundamentally different approach and focused on entire archipelagos using species richness of vascular plants on 23 archipelagos worldwide and their 174 constituent islands. We assessed differential effects of biogeographic factors (area, isolation, age, elevation), current and past climate (temperature, precipitation, seasonality, climate change velocity) and intra-archipelagic spatial structure (archipelago area, number of islands, area range, connectivity, environmental volume, inter-island distance) on plant diversity. Species diversity of each archipelago (γ) was additively partitioned into α, β, nestedness and replacement β-components to investigate the relative importance of environmental and spatial drivers. Multiple regressions revealed strong effects of biogeography and climate on α and γ, whereas spatial factors, particularly number of islands, inter-island distance and area range, were key to explain β. Structural equation models additionally suggested that γ is predominantly determined by indirect abiotic effects via its components, particularly β. This highlights that β and the spatial arrangement of islands are essential to understand insular ecology and evolution. Our methodological framework can be applied more widely to other taxa and archipelago-like systems, allowing new insights into biodiversity origin and maintenance.     

Carbon metabolism in the subantarctic Kerguelen cabbage Pringlea antiscorbutica R. Br.: environmental controls over carbohydrates and proline contents and relation to phenology

The subantarctic Brassicaceae Pringlea antiscorbutica R. Br. (Kerguelen cabbage) was used as a model to study the physiological adaptations of higher plants to the subantarctic environment. ¹³C-nuclear magnetic resonance permitted, in combination with biochemical methods, the identification and quantification of the major solutes in leaves, stem and roots. As characterized in many Brassicaceae, proline was a major solute in all organs of the plants, and its accumulation was mainly controlled by salt stress rather than temperature. Glucose was the major soluble sugar in the leaves, whilst sucrose and starch accumulated in stems and roots. Over a period of 1 year we found strong correlations between (i) glucose content in leaves and irradiance, and (ii) starch content in non-photosynthetic organs and air temperature. The pattern of carbohydrate accumulation indirectly indicated that photosynthetis was sustained throughout the year, even during cold days when the temperature remained near 0 °C. This is consistent with the direct gas exchange measurements showing that photosynthetic capacity is mainly influenced by irradiance and weakly by temperature. Taken together, these characteristics demonstrated that the growth and development cycle occurs without a period of dormancy.