Molecular phylogenetic relationships within and among diploid races of Glycine tomentella (Leguminosae)

DNA-sequence variation at the single-copy nuclear locus histone H3-D was surveyed in 35 accessions of diploid Glycine tomentella Hayata (2n=38, 40) and samples of the closely related new species Glycine aphyonota B. Pfeil and Glycine pullenii B. Pfeil, Tindale & Craven. The objective was a thorough analysis of the infraspecific variation in this complex species as a prelude to the analysis of the evolutionary origin of its tetraploid races. The shortest trees found by a heuristic search employing parsimony all grouped the accessions into five well-supported clades that related closely to infraspecific taxa previously recognised from cytogenetic, isozyme and ITS-sequence studies. The most-differentiated race (isozyme label D4) is related to the so-called A-genome species G. clandestina Wendl., G. canescens F.J. Herm., G. latrobeana (Meissn.) Benth. and G. argyrea Tind. This race is restricted to the central uplands of Queensland. The two common races from Queensland are the aneuploid (2n=38) race and the euploid form from north-east coastal regions (D3). Remarkably, an isolated population of this race was found in the northern wetter fringes of the Kimberley District, Western Australia. The remaining two races (D5A and D5B) are centred on the monsoonal tropics of Kimberley and Top End, Northern Territory. These two groups have distinctive isozyme and morphological features that support the recognition of such divergence, at least at subspecific level.