921 resultados para GALAPAGOS-ISLANDS


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Many species of Apiaceae are found in the Macaronesien Region. Several have been introduccd by human activities, but a number of taxa is endemic to the different archipelagos or even rrstrictcd to a single island. The following enumeration is based mainly on HANSEN & SUNDING ( 1993). In the Arores 28 different taxa of Apiaceae occur; among them four endemic species [AUIMI; hrrrrii WATSON, A. trifoliatum (WATSON) TKEL., Clrtrc~,y~l~~ll~r~~~ cl:oricrm TREL.. SOErich trwrictr GUTIINICK ex SEUB.]. In Madeira the Apiaceae are very diverse and consist ol’ 29 species and subspecies. From the archipelago two monotypic genera, rC/c/trtio. velitru~rr t/ccipicvr.s (SCHRAD. & J. C. WENDL.) Ho~+hl. md kJorli:ia edu[is LOWE and ~hrcc cndcmic species [Oemmrlre diwricore (R. BR.) MABB.. I/nperrr/orio lotvei COSS. and Burrirr~r hre~$~lirrnr LOWE] are described. The Canary Islands have the highest numbcr of plant-species and a high level of endemism. 5-l taxa of Apiaceae are recorded including three endemic genera (Rtrrheopsis A. HANSEX & KUNKEL, Todm-oa PARL. and Tiqyrmm PARL.) and further I5 endemic taxa. The Apiaceae are represented in the Cape Verde Islands by I2 species. Most of the taxa have been introduced by human activities (LOBIN & ZIZKA 1957) like Amvhm grm’eo- 1efr.s L., Apirm grmvolerrs L, Foerricrrhrr urlgore MILL.. Corimrtlru~t~ srrtirvrrrr L. or Petrosilerrm crisprrm (FRILL.) A.W.HILL. These species are cultivated and some of them later became \\esdy. Other species like Ciclosper- UWL /e/~fo/~/l~ll~rrtr (PER%) SPRAGUE (= Apimr leproplr~llrr~rr) are weeds of cultivated grounds or wasted lands. All these species are today widespread in temperate. subtropical or tropical regions all over the world. The only native species are to be found in the endemic genus To~wI~~I~~~ PARL.

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The African Republic of Cape Verde consists of nine inhabited and several uninhabited volcanic islands set out in the Atlantic Ocean, about 500 km off the most westerly point of the African mainland and 1500 km south of the Canary Islands @g. 2). Most are rugged and mountainous; three (Sal, Maio, and Boavista) are flat, desert islands with sand beaches. Precipitation is meagre and very erratic; indeed Cape Verde can be seen as an island extension of the arid Sahel zone. Three species of the genus Phoenix are recorded from the Cape Verde Islands, P. akzctyli&a L., P. canariensis Chabaud and P. atlantica A. Chev. While the former two species have almost certainly been introduced by man, the latter is said to be endemic to the islands. Perhaps because the Cape Verdes are a particularly isolated set of islands or because palms are notoriously awkward to collect, little is known about the taxonomy, origins and natural history of this species. Phoenix atlantica was described by the French botanist Auguste Chevalier (1935a) following field exploration in the Cape Verdes in 1934 (Chevalier 1934: 1153). Chevalier provided limited diagnostic characters, defining the species as a clustering palm with 2-6 trunks, 5-15 m in height with dark green leaves 2-3 m in length. He considered it to be most similar in form to P. &ctyZzjkra and P. canariensis, possessing characters of both (Chevalier 1935a). Chevalier’s description indicates that Phoenix atlantica can be distinguished easily from P. canariensis by its clustering growth form (P. canariensis always has a single, stout trunk) and its shorter, straighter leaves. However, the differences between P. atlantica and P. dactylzjkra appear much more subtle. For example, while P. dacfylifera is usually observed as single-stemmed, when left undisturbed for a number of years it becomes clustering like the Cape Verde Phoenix, so this character on its own is unreliable. Further alleged distinctions include acuminate (P. atlantica) versus rounded (P. dactylzjkra) petals in the male flowers (Chevalier 1935a, b, Greuter 1967: 249, and Brochmann et al. 1997), fruit 2 cm long (P. atlantica) versus fruit more than 2.5 cm long (P. dactyl&a) (Brochmann et al.

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New data on the distributibn and conservation status of some angiosperms of the Cape Verde Islands, W Africa Intensive field work aud analysis of the state of biodiversity ou all islands during the years iYY.3 lo IYYY Icd lo lhc publication ol’several contributions lo the flora and vegelalion of the archipclago of Cabo Verde (Brochniann & al. 1997, Gornes & Vera-Cruz 1993. Gonles & al. I9YSa-h. 1998, Games 1997. Kilian & Leyens 1994, Leyens 1998. Leyens & Lobin 1995, Lobin & al. 1995) as well as to the compilation of the First Red Data List for the Cape Verde Islnuds (Lcyrus & Lobin 1996). the elaboration of the National Strategy for Biodiversity Conservation (SIPA 19YY) and ! compilation of all areas in urgent need of protection (Leyens unpubl. diplonla thc.\is IYYJ. Gwnes & al. iu prep.). As part UC the activities of the lnstituto National de Invcstig;u$o c Dcscnvolvitucnto Agriirio (INIDA) and the Dcpurtamcnto de GeociSncias do Institute Supcriot de Educ;u$o t ISE) iutcnsive t’icld studies were conducted PI many diffcrctu localilics OII xcvcr;~I islands. resulting in a thesis tGo~nes IY97) and several terminal study papers (Luz IYYY. Cosi;t 1994. Gonsalvez 1999). The results show that the vegetation and flora of the islands arc still IWI fully known and much more field work is needed. hllhot~gh Sanliiqw is one of lhc islands whcrc lhc firs1 holanicill iIlVcxligilliollx wcrr c:crriul WI (Wcbh 1x49. Schruidt 1x52. Chcvalicr IY35) and where uu~ny intensive field studirs wcrc

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Partial DNA sequences from two mitochondrial (mt) and one nuclear gene (cytochrome b, 12S rRNA, and C-mos) were used to estimate the phylogenetic relationships among the six extant species of skinks endemic to the Cape Verde Archipelago. The species form a monophyletic unit, indicating a single colonization of the islands, probably from West Africa. Mabuya vaillanti and M. delalandii are sister taxa, as indicated by morphological characters. Mabuya fogoensis and M. stangeri are closely related, but the former is probably paraphyletic. Mabuya spinalis and M. salensis are also probably paraphyletic. Within species, samples from separate islands always form monophyletic groups. Some colonization events can be hypothesized, which are in line with the age of the islands. C-mos variation is concordant with the topology derived from mtDNA.

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The size, growth and spawning characteristics of pompano dolphin (N=150) and common dolphinfish (N=36) caught off the Canary Islands between May and September 1995 and between July and September 1996 were examined. Fork length (FL) of pompano dolphin was in the range 28.3-62.8 cm. In 1995, the mean length increased significantly from June to September. However, in 1996, the mean length was significantly larger in July than in September. The overall length-weight relationship was W=0.0287*FL2.774 (r=0.97), while these relationships by sex were as follows: W=0.031*FL2.758 (r=0.98) and W=0.0282*FL2.776 (r=0.97), for males and females respectively. Spawning takes place at the beginning of the Summer (June-July). All the individuals obtained showed developing gonads, but females showed a higher gonadosomatic index (GSI) than males. The highest GSI values were obtained in June (x- =3.10±1.73), and decreased progressively towards the end of the season (September), when the average of this index was x- = 1.86±0.87. Similarly, the condition index decreased significantly from June to September. The proportion of females was always significantly higher than males, except in July 1996 when it was 1:1. There was a high correspondence between growth rates determined by annuli scale interpretation and modal progression analysis. According to scale annuli interpretation, the individuals caught showed more than five age classes. However, there are doubts about age assignation from scales. Fork length of common dolphinfish was in the range of 76.5-103.0 cm. The length-weight relationships obtained for all the specimens caught was W=0.00095FL3.527 (r=0.96), while these relationships by sex were as follows: W=0.00398FL3.222 (r=0.94) and W=0.01656FL2.873 (r=0.91), for males and females respectively. Spawning probably takes place at the beginning of the Summer. All the individuals obtained showed developing gonads, although the GSI of females were higher than males. The highest GSI values were obtained in June (x- =5.50±2.17). In the same way, the condition index decreased from May to June. The proportion of females was always slightly higher than males (1:1.4), but the ratio was not significantly different from 1:1

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The oceanic crust fragments exposed in central America, in north-western South America, and in the Caribbean islands have been considered to represent accreted remnants of the Caribbean-Colombian Oceanic Plateau (CCOP). On the basis of trace element and Nd, Sr, and Pb isotopic compositions we infer that cumulate rocks, basalts, and diabases from coastal Ecuador have a different source than the basalts from the Dominican Republic. The latter suite includes the 86 Ma basalts of the Duarte Complex which are light rare earth element (REE) -enriched and display (relative to normal mid-ocean ridge basalts, NMORB) moderate enrichments in large ion lithophile elements, together with high Nb, Ta, Pb, and low Th contents. Moreover, they exhibit a rather restricted range of Nd and Pb isotopic ratios consistent with their derivation from an ocean island-type mantle source, the composition of which includes the HIMU (high U-238/Pb-204) component characteristic of the Galapagos hotspot. In contrast, the 123 Ma Ecuadorian oceanic rocks have flat REE patterns and (relative to NMORB) are depleted in Zr, Hf, Th, and U. Moreover, they show a wide range of Nd and Pb isotopic ratios intermediate between those of ocean island basalts and NMORB. It is unlikely, on geochemical grounds, that the plume source of the Ecuadorian fragments was similar to that of the Galapagos. In addition, because of the NNE motion of the Farallon plate during the Early Cretaceous, the Ecuadorian oceanic plateau fragments could not have been derived from the Galapagos hotspot but were likely formed at a ridge-centered or near-ridge hotspot somewhere in the SE Pacific.

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Da una opinión valorativa, en base a fundamentos o criterios económicos, la importancia del Guanay, conocido en la ciencia como Phalacrocorax bouganvillei, en la producción del guano de isla y en el desarrollo económico del país, dándole el título de la ave más valiosa en el mundo.

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A population of leaping grey mullet (Liza saliens (Risso, 1810) was studied in order to measure seasonal and annual growth rates. The annual growth rates were similar to those reported for other populations from the central Western Mediterranean and intermediate between those living in northern and southern areas. As usual, the growth rate of adult males was slower than that of females. Males reached adulthood in their third summer. Females of the same age showed a moderate gonadal development, but did not ripen until the next summer. Mullets of all ages gained weight only when the water temperature was higher than 20°C. However adults and immature fish showed reduced growth in mid-summer, when that of the juveniles peaked. This difference is not a consequence of the reproductive cost, because the growth rate of immatures was greatly reduced although they did not spawn.

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A delta(34)S value of +6.3 +/- 1.5% was estimated for the rhyodacitic degassing magma present underneath the hydrothermal system of Nisyros, based on the S isotope ratios of H2S in fumarolic vapors. This value was estimated by modeling the irreversible water-rock mass transfers occurring during the generation of the hydrothermal liquid which separates these fumarolic vapors. The S isotope ratio of the rhyodacitic degassing magma of Nisyros is consistent with fractional crystallization of a parent basaltic magma with an initial delta(34)S value of +4% (+/-at least 1.5%). This positive value could be explained by mantle contamination due to by either transference of fluids derived from subducted materials or involvement of altered oceanic crust, whereas contribution of biogenic sulfides from sediments seems to be negligible or nil. This conclusion agrees with the lack of N-2 and CO2 from thermal decomposition of organic matter contained in subducted sediments, which is a characteristic of the whole Aegean arc system. Since hydrothermal S at Milos and Santorini has isotope ratios similar to those determined at Nisyros, it seems likely that common controlling processes are active throughout the Aegean island arc. (C) 2002 Elsevier, Science B.V. All rights reserved.

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The Fuerteventura Jurassic sedimentary succession consists of oceanic and elastic deposits, the latter derived from the southwestern Moroccan continental margin. Normal mid-oceanic-ridge basalt (N-MORB) flows and breccias are found at the base of the sequence and witness sea-floor spreading events in the central Atlantic. These basalts were extruded in a postrift environment (post-late Pliensbachian), We propose a Toarcian age for the Atlantic oceanic floor in this region, on the basis of the presence higher up in the sequence of the Bositra buchi filament microfacies (Aalenian-Bajocian) and of elastic deposits reflecting tectono-eustatic events (e.g,, late Toarcian to mid-Callovian erosion of the rift shoulder). The S-l sea-floor oceanic magnetic anomaly west of Fuerteventura is therefore at least Toarcian in age. The remaining sequence records Atlantic-Tethyan basinal facies (e.g., Callovian-Oxfordian red clays, Aptian-Albian black shales) alternating with elastic deposits (e.g., Kimmeridgian-Berriasian periplatform calciturbidites and a Lower Cretaceous deep-sea fan system). The Fuerteventura N-MORB outcrops represent the only Early Jurassic oceanic basement described so far in the central Atlantic. They are covered by a 1600 m, nearly continuous sedimentary sequence which extends to Upper Cretaceous facies.

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Fossil charophytes were recorded in two different stratigraphic units from the non-marine Palaeogene of the Balearic Islands. In the Peguera Limestone Fm. of Mallorca the charophyte flora is characterised by two assemblages. The first contains Raskyella peckii subsp. meridionale, Harrisichara caeciliana and Maedleriella mangenoti, from the Bartonian and Lutetian; whilst the second is characterised by Harrisichara vasiformistuberculata and Nitellopsis (Tectochara) aemula, Middle Priabonian in age. The Cala Blanca Detrital Fm. has yielded Lychnothamnus stockmansii and Sphaerochara inconspicua in Menorca whilst in Mallorca it contains Lychnothamnus praelangeri, L. langeri and Sphaerochara hirmeri. This flora is Late Priabonian and Oligocene in age. These results suggest that the beginning of Paleogene non-marine deposition was diachronic in Mallorca. In terms of biogeography, the Eocene charophytes of Mallorca show affinity with North-African floras. The presence of the Eocene African subspecies Raskyella peckii meridionale in Mallorca enables the biogeographic boundary between this form and the European subspecies R. peckii peckii to be drawn at about 32º N latitude in the Iberian Plate.

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The morphological characterisation of the western submarine island flanks of El Hierro and La Palma differentiates four type-zones that may give new insights into the evolution of oceanic island slopes. The different type-zones result from the interplay between constructive volcanic processes, hemipelagic settling and volcano collapses. The latter results in massive debris avalanche deposits, which form large volcaniclastic aprons. In most cases, the headwall scarps are clearly exposed on the emerged part of the islands. The events that occurred in the youngest and westernmost islands of El Hierro and La Palma have vertical runouts exceeding 6,000 m and volumes that can reach several hundred km3. The landslide frequency for the entire Canaries is one major event per 90 ka. Triggering mechanisms are closely related to magmatic processes. The increase in the shear stress is directly linked with the forceful intrusion of magma along ridge-rift systems, while in the western Canary Islands it seems that the main process reducing shear resistance may be related to the rise in pore pressure due to hydrothermal circulation.