Phylogenetic position of Dunaliella acidophila (Chlorophyceae) based on ITS and rbcL sequences
Assunçao P, Jaén-Molina R, Caujapé-Castells J, De la Jara A, Carmona L, Freijanes K, Mendoza H
Journal of Applied Phycology 2011 (in press, DOI 10.1007/s10811-011-9676-1)
Dunaliella acidophila is one of the most extreme acidophiles on earth and is able to survive in highly acidic habitats. This characteristic has made this organism the universal model for the study of abiotic stress. Although D. acidophila is currently circumscribed to the subgenus Pascheria within Dunaliella Teodoresco (Chlorophyceae), its taxonomic position has stirred controversy. The comparison of D. acidophila CCAP19/35 internal transcribed spacers (including ITS2 secondary structure analysis) and RuBisCo large subunit (rbcL) sequences with other Dunaliella species confirms that D. acidophila should maintain its phylogenetic position within the genus Dunaliella, suggesting its inclusion within the subgenus Dunaliella. Furthermore, the ITS1 and ITS2 data revealed that D. acidophila was highly divergent from the other freshwater species assessed, D. lateralis, with which it barely shares a 56.8% similarity.
The colonization history of Juniperus brevifolia (Cupressaceae) in the Azores islands
Rumeu B, Caujapé-Castells J, Blanco-Pastor JL, Jaén-Molina R, Nogales M, Elías RB, Vargas P
PLoS ONE 6(11): e27697. doi:10.1371/journal.pone.0027697 (2011)
Background: A central aim of island biogeography is to understand the colonization history of insular species using current distributions, fossil records and genetic diversity. Here, we analyze five plastid DNA regions of the endangered Juniperus brevifolia, which is endemic to the Azores archipelago.
Methodology/Principal Findings: The phylogeny of the section Juniperus and the phylogeographic analyses of J. brevifolia based on the coalescence theory of allele (plastid) diversity suggest that: (1) a single introduction event likely occurred from Europe; (2) genetic diversification and inter-island dispersal postdated the emergence of the oldest island (Santa Maria, 8.12 Ma); (3) the genetic differentiation found in populations on the islands with higher age and smaller distance to the continent is significantly higher than that on the younger, more remote ones; (4) the high number of haplotypes observed (16), and the widespread distribution of the most frequent and ancestral ones across the archipelago, are indicating early diversification, demographic expansion, and recurrent dispersal. In contrast, restriction of six of the seven derived haplotypes to single islands is construed as reflecting significant isolation time prior to colonization.
Conclusions/Significance: Our phylogeographic reconstruction points to the sequence of island emergence as the key factor to explain the distribution of plastid DNA variation. The reproductive traits of this juniper species (anemophily, ornithochory, multi-seeded cones), together with its broad ecological range, appear to be largely responsible for recurrent inter-island colonization of ancestral haplotypes. In contrast, certain delay in colonization of new haplotypes may reflect intraspecific habitat competition on islands where this juniper was already present.
La flora endémica terrestre canaria en la sociedad de la información: una visión molecular
Caujapé-Castells J
El Periodico del Museo Elder 1: 11-15 (2011)
Teniendo en cuenta las incertidumbres sobre el presente de la biodiversidad, puede parecer una osadía investigar el pasado de la flora endémica de una región insular tan rica, compleja y variable como Canarias a través de variables invisibles (la información que contiene la molécula de ADN) para derivar algunas conclusiones de futuro sostenible. Pero en el año internacional de la biodiversidad, y aunque sea solamente desde el punto de vista de la biología molecular, vale la pena apuntar lo que creemos saber, lo que imaginamos y lo que ciertamente ignoramos sobre la diversidad vegetal terrestre del archipiélago.
Jesters, red queens, boomerangs and surfers: A molecular outlook on the diversity of the Canarian endemic flora
Caujapé-Castells J
Pp. 284-324 In: Bramwell D, Caujapé Castells J (eds) The Biology of Island Floras. Cambridge University Press, London (2011)
The interpretation of the present molecular phylogenetic dataset for the Canarian flora in the light of the known tectonic-climatic changes in the Atlantic basin reveals an extremely dynamic scenario of recurrent island colonization, dispersal, speciation and extinction, mainly developed in several discrete time periods after the emergence in the Miocene of the easternmost islands, where reciprocal biodiversity interchange with mainland NW Africa was probably not uncommon. Consistently, the population genetic dataset reveals significantly higher genetic variation levels in Fuerteventura, Lanzarote and Gran Canaria than in the four westernmos islands. This finding further suggests that the higher ecological uniformity and the much lesser geographic complexity of (especially) Fuerteventura and Lanzarote could have fostered abundant genetic swamping and the formation of syngameons, consisting of incipient species that still retain crossing compatibility. Whilst rife gene flow among genotypes that might have been previously isolated in the mainland must have aided to maintain species cohesion and to promote rapid monophyly in these islands, the resulting high genetic variation levels could have been determinant to the successful colonization of the westernmost islands, where more complex geographical and ecologicas features feasibly promoted selection processes and gene flow cessation. This "surfing syngameon" hypothesis also predicts that much higher levels of gene flow should stall evolutionary change within the two easternmost islands, thereby contributing to explain their presently lower taxonomic richness. In sharp contrast, ther prevalent influence of selection and drift on the westernmost island colonizers would tend to exacerbate their genetic differences relative to the easternmost congeners, and would partially account for the much richer biotic content of these islands. Critically, both the molecular phylogenetic and the population genetic datasets have heterogeneous weaknesses that impinge on our present capability to thoroughly assess hypotheses on pre- and post-colonization evolution in the Canarian archipelago, and converge to beget at least as many new challenges for the future as insightful answers they did provide to long-standing questions.
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