b Natural Resources and the Environment, CSIR, PO Box 395, Pretoria 0001, South Africa There is currently a major gap in our understanding of early- greening in savanna trees, particularly in southern Africa. We monitored the phenology of a stand of Burkea africana and the surrounding grasses in the Nylsvley Nature Reserve, South Africa at weekly intervals over the green-up periods (August–November) between 2012 and 2014. We compared the normalized difference vegetation index (NDVI) from the 250 m resolution MODIS satellite imagery to our detailed on-the-ground phenological data in an attempt to detect any possible early-greening signals in the NDVI data. We then assessed the NDVI values in other known B. africana woodlands across southern Africa to determine the prevalence of early-greening in this species over a latitudinal gradient. The sites selected were the Seringveld Conservancy (South Africa), Nylsvley Nature Reserve (South Africa), Kavango Region (Namibia), Pan- damatenga (Botswana), Hwange National Park (Zimbabwe), Lukulu (Zambia) and Mongu (Zambia). The start date of green-up was compared to the start date of seasonal rainfall using Tropical Rainfall Measuring Mission (TRMM) estimates that showed that more than 15 mm of rain had fallen. If the green-up started ahead of the start of rainfall, early-greening was recorded. We determined that 20% of the average maximum NDVI was sufficient to signal green-up of the trees. Lukulu had the earliest average green-up (3 Oct ± 5.34) followed by Mongu (5 Oct ± 2.69) suggesting that B. africana woodlands closer to the equator show the earliest green-up. However, Nylsvley had the next earliest green-up (11 Oct ± 5.07), with Pandamatenga (5 Nov ± 4.23) having the latest green-up. There appears to be a latitudinal and mean annual rainfall influence on the timing of green-up in B. africana woodlands throughout southern Africa with more arid sites greening up later. doi:10.1016/j.sajb.2015.03.136 Phylogeny and invasion process K. Yessoufou Department of Environmental Sciences, University of South Africa, Florida Campus, Florida 1710, South Africa Non-native species along the introduction–naturalization–inva- sion continuum are three ecologically distinct groups. There are several lines of evidence suggesting that they could also represent three evolutionarily distinct groups. Here, I explore this hypothesis using Australian Acacia species introduced across the globe. I retrieve from TreeBASE (ID 13659) the most comprehensive phylogeny recently assembled for 508 Australian Acacia species based on four plastid and two nuclear DNA regions. I also compile data on Australian Acacia species introduced, naturalized and invasive across the globe. I then assess, using several approaches, whether species at each stage of the continuum represent phylogenetically distinct groups.I found no evidence that species that are successful at each stage are more closely related than expected by chance. However, there was a trend towards a phylogenetic distinctiveness of groups, but there was no strong statistical evidence supporting this. Across introduction-naturalization-invasion continuum, species might rep- resent ecologically distinct groups but they are not phylogenetically so. This finding therefore suggests that contemporary (and perhaps context-specific) ecological factors explain better (than species evolutionary history) the progression of introduced species along the continuum. doi:10.1016/j.sajb.2015.03.137 Poster abstracts Divergence times estimates and historical biogeography of southern African Strychnos L. (Loganiaceae) A. Adebowale a , A. Nicholas b , J. Lamb b , Y. Naidoo b a School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, Johannesburg 2050, South Africa b School of Life Sciences, University of KwaZulu-Natal, New Biology Building, South Ring Road, Westville 3630, South Africa An understanding of the earth's geologic past can not only offer insights into the factors influencing the present spatial distribution of organisms, but also proffer plausible explanations for some of the adaptive features accumulated among a given group of closely related taxa over time. Here we investigate divergence times among southern African (SA) Strychnos using nucleotide sequence data from the internal transcribed spacer of the ribosomal DNA. We also infer ancestral range of 15 SA Strychnos based on their present day distribution. Bayesian estimates of divergence times implemented in BEAST indicate a middle Miocene origin for SA Strychnos at 12.72 Ma. This was followed by eight radiations in the late Miocene. Two radiations resulting in the evolution of arid-adaptedness occurred in the late Pliocene–early Pleistocene epoch. Biogeographic reconstructions with S-DIVA, Bayesian Binary MCMC and DEC suggest that within the context of our analysis, the most recent common ancestors of SA Strychnos occupied the deciduous woodlands of tropical Africa, and that dispersal is the major force behind the current distribution. The basal species in our reconstructed tree is consistent with the rain forest origin of Strychnos along the Guineo-Congolian/South American axis. We argue that global palaeo- climatic oscillations have played a significant role in the evolution of SA Strychnos and specifically that the evolution of arid-adaptation is recent, coinciding with periodic increase in aridity during the Pliocene– Pleistocene epoch. The peculiar distribution pattern observed in Strychnos gerrardii is postulated to be a consequence of vicariant events in the late Pleistocene; events rooted in the repeated cycles of range expansions and contractions of its ancestors, leading to its being left in its coastal refugia while retaining ancient signature attributes of arid adaptation. Our findings are invaluable for Strychnos conservationin the face of human mediated climate change. doi:10.1016/j.sajb.2015.03.138 Alexin™ treatment boosts defence responses in wheat against Russian wheat aphid (Diuraphis noxia) infestation J. Adendorff a,b , L. Mohase a , S.vdM. Louw b , A. Jankielsohn c a Department of Plant Sciences, University of the Free State, PO Box 339, Bloemfontein 9300, South Africa b Department of Zoology and Entomology, University of the Free State, PO Box 339, Bloemfontein 9300, South Africa c SGI-ARC Bethlehem, South Africa Alexin™ is a nutrient complex with salicylic acid derivatives that increases the inherent resistance of plants. It acts as a priming agent providing long-term protection against a broad range of pathogens and pests. The effect of Alexin™ treatment on the defence responses (β-1,3-glucanase and peroxidase activity) of wheat during Russian wheat aphid (RWA, Diuraphis noxia) infestation was investigated. Wheat cultivars susceptible (SST 387) or resistant (Elands, PAN 3379) to the South African RWA biotype 1 were treated with different Alexin™ concentrations (0.25%, 0.375%, 0.5%) before RWA infestation (20 aphids per plant). Apoplastic enzyme activities of β-1,3-glucanase and peroxidase were determined immediately after Abstracts 205