Molecular phylogeny of Acacia Mill. (Mimosoideae: Leguminosae): Evidence for major clades and informal classification

Abstract

Sequences of nuclear ribosomal DNA internal (ITS) and external (ETS) transcribed spacers were used to generate a phylogeny of Acacia Mill. s.str. (synonyms: Acacia subg. Phyllodineae (DC.) Seringe; Racosperma Mart.). This study included 109 exemplar taxa from all seven sections recognised in previous classifications, and represents the largest sampling of diversity for molecular phylogenetics of Acacia s.str. undertaken so far. Four main clades were identified from the combined dataset of ITS and ETS using parsimony and Bayesian analyses. Two of these clades consist mostly of uninerved phyllodinous taxa assigned to sect. Phyllodineae. One clade includes taxa related to A. victoriae and A. pyrifolia, and the second comprises taxa in the A. murrayana species group. These taxa occur predominantly in semi‐arid and arid regions. Relationships also resolve the previously identified Pulchelloidea clade, which includes members of sects. Pulchellae, Alatae, Phyllodineae and Lycopodiifoliae. A large clade with limited phylogenetic resolution was also identified (the "p.u.b. clade"). This is an assemblage of plurinerved and uninerved phyllodinous taxa and also bi‐pinnate taxa from sect. Botrycephalae. Clades are discussed with reference to morphological characters, and while some morphological states are correlated with clades, including seedling ontogeny, inflorescence and phyllode nerves, clear synapomorphies remain to be identified. Traditional classifications of Acacia s.str. are artificial and a preliminary informal classification based on phylogenetic relationships within Acacia s.str. is proposed.

Application of Molecular Markers for Identification of Potential Salt Tolerant Plant Species for use in Agroforestry and Saline Land Reclamation

“…The complete ITS region was amplified by PCR using primers S3 and 26SE with the appropriate cycling conditions [8]. Similarly, the external transcribed spacer (ETS) region was amplified using primers 18S-IGS and AcR2 (see Table 2) [7]. The reaction mix contained 5 μL of 10x reaction buffer, 2 μL of 2mM dNTPs, 25 pmol of forward primer, 25 pmol of reverse primer, 10-50 ng of template (genomic) DNA and 1.0 unit of Taq DNA polymerase and the mixture made up to a final volume of 50 μL with water.…”

“…This study uses these two nuclear ribosomal DNA markers, the internal transcribed spacer (ITS) and the external transcribed spacer (ETS), to identify related species as well as to resolve their phylogenetic relationships. In order to identify possible candidates that can be potentially salt tolerant, the closest relatives of the four target salt tolerant species-Acacia pendula, A. salicina, A. stenophylla and A. victoriae, based on morphology and classification in the Flora of Australia [5], [6], [7] were chosen. Paraserianthes lophantha was used as the out group Ascertaining their relationships based on genetic markers in addition to the classification given in Flora of Australia, could help in narrowing the identification process of salt tolerant species.…”

Speciation in gall-inducing thrips on Acacia in arid and non-arid areas of Australia

“…1). There is uncertainty as to whether the Juliflorae, Plurinerves, and Phyllodineae sections form natural monophyletic divisions (Murphy et al, 2010). At the level of total gall-thrips host-range, host species relationships are unresolved, but the earlier nomenclature provides some guidance.…”

“…Plurinerves hosts show strong geographical affiliation with vegetation types that evolved away from the arid interior. Acacia species richness tends to be concentrated in non-arid areas of the monsoonal tropics, and sclerophyll of temperate biomes (Crisp et al, 2004;Murphy et al, 2010). Thus, abiotic processes underlie host plant diversification.…”

“…Few other plant clades dominate the Australian continent as do Acacia Mill. (Murphy et al, 2010). In particular, The Great Dividing Range in eastern Australia and south-west Western Australia are areas of high species diversity.…”