Genetic differentiation in the genus Lithops L. (Ruschioideae, Aizoaceae) reveals a high level of convergent evolution and reflects geographic distribution

Southern Africa is one of the hot spots for plant biodiversity, with ca. 80% of species endemic to this area. Rapid and recent radiations in Southern African plant genera were triggered by fine-scale differences in climate, topography and geology. The genus Lithops (Ruschioideae, Aizoaceae) contains...

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Bibliographic Details
Published in:Plant biology (Stuttgart, Germany) Germany), 2011-03, Vol.13 (2), p.368-380
Main Authors: Kellner, A., Ritz, C. M., Schlittenhardt, P., Hellwig, F. H.
Format: Article
Language:English
Subjects:
AFLP
Africa, Southern
Aizoaceae
Aizoaceae - genetics
Algorithms
Amplified Fragment Length Polymorphism Analysis
Bayes Theorem
Biodiversity
Cell Nucleus - genetics
chloroplast DNA
Cluster Analysis
DNA, Chloroplast - genetics
DNA, Plant - genetics
DNA, Ribosomal Spacer - genetics
Evolution, Molecular
Gene Frequency
Models, Genetic
nuclear ribosomal ITS
Phylogeny
Sequence Analysis, DNA
Southern Africa
speciation
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Summary:Southern Africa is one of the hot spots for plant biodiversity, with ca. 80% of species endemic to this area. Rapid and recent radiations in Southern African plant genera were triggered by fine-scale differences in climate, topography and geology. The genus Lithops (Ruschioideae, Aizoaceae) contains 37 species and is widely distributed in Southern Africa. Species delimitation within the genus is challenging because the limited number of morphological characters in these reduced succulents varies intensely between populations, presumably as adaptations to local geological environments. We analysed phylogenetic relationships within Lithops using non-coding chloroplast DNA (trnS-trnG intergenic spacer), nuclear ribosomal internal transcribed spacer (nrITS) sequences and AFLP data. Genetic variability of the sequence data was very low, but AFLP data detected nine clades within Lithops that do not fit current morphology-based taxonomy. Two of these clades are separated by their distribution on the northern and eastern border of the distribution area, and four clades are found in the Gariep Centre in the estuary of the Orange River. Morphological similarities, especially colour of leaves, evolved repeatedly within the clades, thus we hypothesise that closely related species became adapted to different soil types in a mosaic-like geological environment. One-third of the species are found in the Gariep Centre, characterised by extremely diverse edaphic habitats.
ISSN:1435-8603
1438-8677
DOI:10.1111/j.1438-8677.2010.00354.x