Molekulare Phylogenie und Biogeographie der Chamäleons
Zusammenfassung der Projektergebnisse
This research project aimed at resolving the phylogenetic relationships and biogeographic origins of chameleons, a group of almost 200 species of lizards characterized by various unique and spectacular morphological features. To obtain this goal we assembled a DNA sequence dataset of ca. 5,000 bp from three mitochondrial and three nuclear genes for a taxon sampling of 174 chameleon species (>90% coverage at species level), and of ca. 14,000 bp from three mitochondrial and ten nuclear genes for a representative sampling of 25 species covering all genera and major clades of chameleons. The obtained phylogenetic tree allows for a number of phylogenetic and biogeographic conclusions: (1) We obtained conclusive evidence for a sister-group relationship of the Seychelles chameleon Archaius tigris with the African genus Rieppeleon, suggesting that its ancestors colonized Madagascar by overseas rafting directly from Africa rather than from Madagascar as previously thought. (2) We inferred a monophyletic group of all largesized Malagasy chameleons (genera Calumma and Furcifer) which has not previously been detected. (3) We confirm small-sized Malagasy ground chameleons (Brookesia) as most basal chameleon genus. (4) Ancestral area reconstructions unanimously suggest an origin of chameleons in Africa and thus contradict the currently assumed out-of- Madagascar scenario. (5) The ancestral habitat of chameleons was closed-canopy forest and only secondarily have they adapted to open habitat and thin perches in the Miocene and Pliocene. As side projects spinning off this major research we discovered numerous new species, mainly from Madagascar. Among these were a number of miniaturized species of Brookesia which rank among the smallest amniotes of the world. These tiny species have persisted for millions of years in very small ranges and habitat fragments and thus can be informative to understand the sensitivity and resilience of such organisms to future climate change.
Projektbezogene Publikationen (Auswahl)
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(2010): A Tarzan yell for conservation: a new chameleon, Calumma tarzan sp. n., proposed as flagship species for the creation of new nature reserves in Madagascar. – Salamandra 46: 1667-179.
Gehring, P.-S., M. Pabijan, F. M. Ratsoavina, J. Köhler, M. Vences & F. Glaw
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(2011): Eastward from Africa: palaeocurrent-mediated chameleon dispersal to the Seychelles islands. – Biology Letters 7: 225-228
Townsend, T. M., K. A. Tolley, F. Glaw, W. Böhme & M. Vences
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(2012) Rivaling the world’s smallest reptiles: Discovery of miniaturized and microendemic new species of leaf chameleons (Brookesia) from northern Madagascar – PLoS One 7: e31314
Glaw, F., J. Köhler, T. M. Townsend & M. Vences
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(2012): Hiding deep in the trees: discovery of divergent mitochondrial lineages in Malagasy chameleons of the Calumma nasutum group. – Ecology and Evolution, 2: 1468-1479
Gehring, P.-S., K. A. Tolley, F. S. Eckhardt, T. M. Townsend, T. Ziegler, F. Ratsoavina, F. Glaw & M. Vences
