Systematics of the genusSalweenia(Leguminosae) from Southwest China with discovery of a second species

Abstract

Salweenia (Leguminosae) has long been defined as a monotypic genus. In this study we carried out comprehensive studies on populations of S. wardii Baker f. across its distribution range. The results showed that this species diverged into two distinct groups: plants from the Yalong Jiang valley have linear leaflets 0.07-0.14 cm wide and relatively flattened legumes, as well as a 2A karyotype asymmetry, whereas plants from the Nu Jiang and Lancang Jiang drainages have lanceolate leaflets 0.20-0.34 cm wide, undulant legumes, and a 1A karyotype asymmetry. Furthermore, molecular phylogenetic analysis of four chloroplast DNA markers (trnL-F, rpl32-trnL, psbA-trnH, trnS-G) recovered two reciprocally monophyletic clades among accessions of plants from these two areas respectively. We therefore recognize individuals of S. wardii in the Yalong Jiang valley as a separate species, S. bouffordiana sp.nov. Salweenia thus contains two allopatrically distributed species and the genus is no longer monotypic. The origin of the disjunction between the two species is briefly discussed and it is hypothesized to have come about through vicariance, resulting of several historic river separations, reversal and capture events estimated to have taken place during the Pleistocene.

Phylogeography of Buddleja crispa (Buddlejaceae) and its correlation with drainage system evolution in southwestern China

“…This is indicative of genetic links between presently disjunct clades (e.g., in the upper-middle Yarlung Tsangpo and CYP, as well as the upper Dadu and CYP) of Buddleja crispa populations, and the isolation of some populations in continuous parts of the species' present geographical range (upper Jinshajiang and Lower Jinshajiang and its tributaries). These fi ndings support the hypothesis that habitat fragmentation caused by hydrological changes disrupted gene fl ow between populations in the hot/warm-dry valleys of adjacent rivers ( Clark et al, 2004 ;Yue et al, 2011 ;. The three nested clades show a similar pattern of north to south disjunctions, with the occupied area refl ecting the contours of the paleo-drainage systems.…”

“…[Fabaceae] ( Yue et al, 2011 ) and Rhododendron ripense Makino [Ericaceae] ( Kondo et al, 2009 ).The cited studies discuss in detail the relationships among disjunct populations in the Jinshajiang, Lancangjiang, Nujiang, Honghev, and Nanpanjiang river systems, but not the effects of (or associations with) the Yarlung Tsangpo capture events discussed by Clark et al (2004) .…”

Phylogeography of Cyananthus delavayi (Campanulaceae) in Hengduan Mountains inferred from variation in nuclear and chloroplast DNA sequences

“…In addition, topographic changes (e.g. development of the rivers and uplift of the mountains) in this region may have also caused the intraspecific and interspecific divergences through allopatric differentiation (Zhang et al, 2011b; Zhang & Sun, 2011; Yue et al, 2011). However, it remains unknown whether allopatric divergences appeared as a general evolutionary result for most species occurring there.…”

Phylogeography of Rosa soulieana (Rosaceae) in the Hengduan Mountains: refugia and ‘melting’ pots in the Quaternary climate oscillations

“…Third, high intra-specific and interspecific diversity can be a result of topographic changes due to river recaptures, e.g., Terminalia franchetii , Salweenia spp. (Yue et al 2011), Buddleja crispa .…”