Verwandschaftsverhältnisse zwischen Varanoiden und Schlangen

[Terciopelo]

Hallo,
ich suche Puplikationen über die Verwandtschaft zwischen Schlangen und Varanen. Mich würde interessieren, ob man Varane und Schlangen als Monophylum ansehen kann, oder ob es Beweise gegen diese Hypothese gibt.
Vielen Dank für die Antworten!
Andy

[Wulf Schleip]

Re: Verwandschaftsverhältnisse zwischen Varanoiden und Schlangen

Hallo,

beschaff Dir mal den Artikel:

Nicolas Vidal and S. Blair Hedges, 2004, Molecular evidence for a terrestrial origin of snakes, Biology Letters, Royal Society, United Kingdom, pp. 226-229

Abstract:
Biologists have debated the origin of snakes since the nineteenth century. One hypothesis suggests that snakes are most closely related to terrestrial lizards, and reduced their limbs on land. An alternative hypothesis proposes that snakes are most closely related to Cretaceous marine lizards, such as mosasaurs, and reduced their limbs in water. A presumed close relationship between living monitor lizards, believed to be close relatives of the extinct mosasaurs, and snakes has bolstered the marine origin hypothesis. Here, we show that DNA sequence evidence does not support a close relationship between snakes and monitor lizards, and thus supports a terrestrial origin of snakes.

http://www.journals.royalsoc.ac.uk/app/home/issue.asp?wasp=87eluvrymmdqhd6vkyvm&referrer=parent&backto=j ournal,4,7;linkingpublicationresults,1:110824,1

und hier noch ein netter Artikel:
Coates,M. and Ruta,M ,2000, Nice snake, shame about the legs, Tree 15 (2)
http://pondside.uchicago.edu/ceb/CoatesRuta2000Snakes.pdf

Grüsse,
Wulf

[WW**]

Re: Verwandschaftsverhältnisse zwischen Varanoiden und Schlangen

Und hier gleich noch einer:

Molecular phylogenetics of Squamata: The position of snakes, Amphisbaenians, and Dibamids, and the root of the Squamate tree
Townsend TM, Larson A, Louis E, Macey JR
SYSTEMATIC BIOLOGY
53 (5): 735-757 OCT 2004

Abstract:
Squamate reptiles (snakes, lizards, and amphisbaenians) serve as model systems for evolutionary studies of a variety of morphological and behavioral traits, and phylogeny is crucial to many generalizations derived from such studies. Specifically, the traditional dichotomy between Iguania ( anoles, iguanas, chameleons, etc.) and Scleroglossa ( skinks, geckos, snakes, etc.) has been correlated with major evolutionary shifts within Squamata. We present a molecular phylogenetic study of 69 squamate species using approximately 4600 ( 2876 parsimony-informative) base pairs ( bp) of DNA sequence data from the nuclear genes RAG-1 (-2750 bp) and c-mos (-360 bp) and the mitochondrial ND2 region (-1500 bp), sampling all major clades and most major subclades. Under our hypothesis, species previously placed in Iguania, Anguimorpha, and almost all recognized squamate families form strongly supported monophyletic groups. However, species previously placed in Scleroglossa, Varanoidea, and several other higher taxa do not form monophyletic groups. Iguania, the traditional sister group of Scleroglossa, is actually highly nested within Scleroglossa. This unconventional rooting does not seem to be due to long-branch attraction, base composition biases among taxa, or convergence caused by similar selective forces acting on nonsister taxa. Studies of functional tongue morphology and feeding mode have contrasted the similar states found in Sphenodon ( the nearest outgroup to squamates) and Iguania with those of Scleroglossa, but our findings suggest that similar states in Sphenodon and Iguania result from homoplasy. Snakes, amphisbaenians, and dibamid lizards, limbless forms whose phylogenetic positions historically have been impossible to place with confidence, are not grouped together and appear to have evolved this condition independently. Amphisbaenians are the sister group of lacertids, and dibamid lizards diverged early in squamate evolutionary history. Snakes are grouped with iguanians, lacertiforms, and anguimorphs, but are not nested within anguimorphs.

[Wulf Schleip]

Re: Verwandschaftsverhältnisse zwischen Varanoiden und Schlangen

Hallo,

den von WW** genannten Artikel findest Du weitestgehend hier:
http://www.rednova.com/news/display/?id=107752

Grüsse,
Wulf

[M.Dobiey]

Re: Verwandschaftsverhältnisse zwischen Varanoiden und Schlangen

Hallo,

Das ist eine Frage, die alles andere als geklärt ist. IEs gibt eine ganze Menge von Indizien die dafür sprechen. Viele davon lassen sich aber auch anders deuten. Andere Indizien sprechen auch gegen eine Verwandtschaft der Schlangen mit den Varanoiden. Da gibt sehr sehr viel Literatur zu.
Ich kann dir mal einige Sachen zuschicken, wenn du mir deine Adresse gibst. Alerdings sind die meisten davon verdammt schwierig zu lesen, da das morphologische Vokabular schon sehr heftig ist...

Grüße,

Maik