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Stefano_A
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Iscritto il: mar gen 16, 2007 1:08 pm

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Messaggioda Stefano_A » mer mar 25, 2009 11:26 am

In riferimento alla seguente notizia:

LE JOURNAL DE MONTRÉAL (Quebec) 17 Gennaio 09 Destini avversi per le iguane e le
tartarughe delle Isole Galapagos
Quito (AFP): Le isole Galapagos festeggiano in questi ultimi giorni la scoperta di una specie unica
di iguana, nonostante vi sia sempre il rischio di estinzione per alcune specie di tartarughe giganti,
simbolo dell'arcipelago. Una squadra di scienziati italo-ecuadoriani ha rivelato all'inizio del mese
la scoperta di una specie unica al mondo di "iguana rugiada", differente di tutte quelle che si
conoscevano. È di un rosa intenso e la sua lunga coda è screziata di nero. Gli scienziati
inizialmente pensarono ad una semplice depigmentazione della pelle di questi rettili (che possono
misurare fino a 1,80 mt di lunghezza) prima di comprendere che invece si tratti di una vera e
propria popolazione distinta dalle altre.
Gli scienziati hanno anche constatato che non è presente nessun giovane esemplare di iguana
rugiada e questo fa temere che la specie possa non sopravvivere dato che se ne conoscono
solamente 36 esemplari. La preoccupazione è tanta anche per il solo esemplare di tartaruga gigante
Geochelone Abigdoni, George il solitario. George che ha ben 105 anni convive con due femmine di
una specie simile dal 1993 e di tutte le uova deposte da queste femmine nessuna era fecondata.

ci tenevo a precisare che, anziché trattarsi di "iguana rugiada", la nuova specie ancora in attesa di una definizione tassonomica ufficiale, e di relativo nome scientifico latino, viene al momento indicata come "iguana rosada", proprio in relazione all'insolita colorazione rosa.

Per chi volesse saperne di più:
An overlooked pink species of land iguana in the Galápagos
Gabriele Gentilea,1, Anna Fabiania, Cruz Marquezb, Howard L. Snellc, Heidi M. Snellc, Washington Tapiad,
and Valerio Sbordonia
aDipartimento di Biologia, Universita` Tor Vergata, 00133 Rome, Italy; bCharles Darwin Foundation, Puerto Ayora, Gala´pagos Islands, Ecuador; cDepartment
of Biology and Museum of Southwestern Biology, University of New Mexico, Albuquerque, NM 87131; and dGalápagos National Park Service, Puerto Ayora,
Gala´pagos Islands, Ecuador
Edited by Francisco J. Ayala, University of California, Irvine, CA, and approved November 11, 2008 (received for review July 2, 2008)

ABSTRACT
Despite the attention given to them, the Galápagos have not yet finished offering evolutionary novelties. When Darwin visited the Galápagos, he observed both marine (Amblyrhynchus) and land (Conolophus) iguanas but did not encounter a rare pink blackstriped land iguana (herein referred to as ‘‘rosada,’’ meaning ‘‘pink’’ in Spanish), which, surprisingly, remained unseen until 1986. Here, we show that substantial genetic isolation exists between the rosada and syntopic yellow forms and that the rosada is basal to extant taxonomically recognized Galápagos land iguanas. The rosada, whose present distribution is a conundrum, is a relict lineage whose origin dates back to a period when at least some of the present-day islands had not yet formed. So far, this species is the only evidence of ancient diversification along the Galápagos land iguana lineage and documents one of the oldest events of divergence ever recorded in the Galápagos. Conservation efforts are needed to prevent this form, identified by us as a good species, from extinction.

ALCUNE CONCLUSIONI SALIENTI
The most surprising result was the deep divergence of the rosada lineage at the basis of the Conolophus clade. This species alters the current thinking about the timing of diversification of land iguanas, which was previously supposed to have occurred in the Pleistocene Epoch (6). Although with a large SD, our estimate sets the origin of this relict lineage back to a period when at least some of the present-day islands had not yet formed. In fact, the oldest extant islands in the archipelago, San Cristo´bal and Espan˜ola, are at least 2.35 and 3.3 million years old, respectively, if not older (7). Thus, given its present distribution, the rosada form clearly represents a conundrum because it occurs only on Volcan Wolf, which is considered younger than Volcan Sierra Negra (0.53 million years, the oldest volcano of Isabela) ( and almost as old as Volcan Cerro Azul (0.35 million years) (9). The ML average genetic distance between C. subcristatus and C. pallidus is much lower than between the rosada form and each of the 2 named species, supporting the distinctiveness of the taxon. Our preliminary data on the morphology of the rosada and yellow forms also indicate differentiation: in addition to their color pattern and independent of their gender, all rosada
individuals investigated are distinguished from the other 2 species by flat dorsal head scales and the prominent adipose nuchal crest with small conic scales. The rosada also shows strong differences in the pattern of the ‘‘head-bob’’ (nodding), a behavior important in territoriality (10) and courtship (11). The microsatellite data also indicated strong differentiation between the rosada and yellow forms, with mutation and genetic drift (in particular for the rosada form) being important determinants.
(…)
The mtDNA haplotype of the rosada is highly differentiated from those of marine iguanas and the rest of land iguanas. The results of theRDP3 analyses allow us to reject the hypothesis that such differentiation might have occurred by mtDNA recombination after hybridization between land and marine forms. The hypothesis of the origin of the rosada by recent hybridization alone between the 2 forms is not supported either. In fact, a rosada-like haplotype is not found in our sample of yellow iguanas, or in marine iguanas. This is indicated by a phylogenetic analysis that we performed by combining original haplotypes from the present study with those found by Rassmann et al. (6) in their sample of 150 marine iguanas from 21 locations on 14 islands [see supporting information (SI)].
(…)
These findings call for a conservation program aimed at evaluating the risk of extinction of this newly recognized species, which, based on currently available data, would be assignable to the ‘‘critically endangered’’ category by meeting criteria B and C of the International Union for Conservation of Nature (IUCN) Red List (14).

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Agostino
Messaggi: 5288
Iscritto il: sab mag 21, 2005 9:06 am
Località: Emilia Romagna
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Messaggioda Agostino » mer mar 25, 2009 12:52 pm

Ricordiamo ai soci che noi traduciamo degli articoli di giornali che ci provengono dal mondo, ben vengano poi delle precisazioni o correzioni .


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