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Ecologically specialized plants are expected to be at greater risk of extinction than generalists due to climate change. Such risk is greatest in biodiversity hotspots such as the Greater Cape Floristic Region (GCFR), which accommodates both ecological specialists and generalists. Thesium L., a genus with the highest number of species in Santalaceae and the most diverse in Africa, offers an appropriate system for evaluating both the correlates of range extent and specialization and the relative extinction risks associated with both. We hypothesized that range size, ecological specialization, and consequent climatically modulated extinction risks are all phylogenetically structured, such that climate change will precipitate a disproportionate loss of phylogenetic diversity in the GCFR Thesium. Past and future species distribution ranges were predicted using MaxEnt models based on present‐day occurrences and environmental conditions. Of the 101 Thesium species modeled, 70% have had large range sizes during the Last Glacial Maximum (LGM), 50% currently have a large range size, and future conditions are predicted to allow 40% to obtain large range sizes. Between the LGM and the present, 17% of species are thought to have undergone a contraction of available range space in the present time whereas 37% are expected to expand their ranges into the future, while 51% of species will experience range contractions. Of the 65 species currently ranked as Least Concern in the South African Red List, 24% will likely shift into higher extinction risk categories. Interestingly, 8.5% of ecological specialists, although having experienced a range reduction from the LGM to the present, are predicted to persist in the face of future climate change. However, the range extent, ecological specialization, and extinction risk are phylogenetically random and therefore should have a negligible impact on the phylogenetic diversity of the GCFR Thesium. [ABSTRACT FROM AUTHOR]

• Rooibos plants had 50% less biomass when grown at low moisture. • Plants avoided drought stress through the production of long roots. • Rooibos exhibited non-stomatal limitations to photosynthesis during drought. • Longer roots and high root/shoot ratios allowed for higher RWC well into drought. • Production of polyphenols allowed the plants a degree of protection. In recent decades climate change has impacted ecosystems negatively globally with Mediterranean systems being particularly vulnerable. Changes in rainfall pattern and amounts have led to increases in flooding and droughts in certain areas of the world. Many important agricultural crops such as Aspalathus linearis (Burm.f.) R. Dahlgren, rooibos tea, rely on the Mediterranean-type seasonality in the Western Cape, South Africa. Aspalathus linearis plants, which occur naturally in the Cedarberg, grow in hot and dry summer conditions and have a root that penetrates the soil down to 2 m, yet no work has looked at the root response to drought under low rainfall environments. The objective of this study was to determine the physiological and morphological response of A. linearis plants grown at two different water regimes to drought. A potted glasshouse experiment was carried out where drought stress (withdrawing watering) was imposed on well-watered and low moisture supplied plants. The low moisture droughted plants exhibited drought tolerant mechanisms which included higher root/shoot ratios as well as thinner roots, both of which are effective for water and nutrient uptake. Overall, plants in the 30% FC treatment recorded lower P max , g s and E after three days in the drought conditions while 70% FC plants were only affected after five days. Furthermore, plants grown under low moisture conditions produced 50% lower biomass compared to plants grown under adequate moisture conditions. This implies that low rainfall and the occurrences of dry spells and drought, associated with climate change are likely to reduce the production of A. linearis in the Cederberg area. [ABSTRACT FROM AUTHOR]

• A. linearis plants lower their leaf temperatures through transpirational cooling • Low chlorophyll and high phenol could be acclimatized adaptive changes to heat • Soil quality and increasing temperatures negatively affect biomass of A. linearis • Younger plants invested more resources to ensure their protection and survival Mediterranean systems, such as in South Africa, are particularly vulnerable to the predicted increases in mean surface temperatures which will likely affect the growth and physiology of many plants and subsequently affect agricultural productivity. Aspalathus linearis (Burm.f.) R. Dahlgren (rooibos) is an important commercial, endemic crop that is produced in the Cederberg region, South Africa. This region experiences a Mediterranean-type ecosystem that is characterised by hot, dry summers (November – February) and cool, wet winters (May – August). This study assessed the effects of temperature on the growth and stress tolerant traits of A. linearis over two years. Crop biomass and selected physiological traits were determined in the field, along a temperature gradient, at four farm sites in the Cederberg during the summer and winter 2017 and summer 2018. Aspalathus linearis plants showed evidence of transpirational leaf cooling during summer and this, combined with lower chlorophyll and high phenolic content, could be considered acclimatized adaptive changes allowing the plants to mitigate the heating effects of elevated temperatures. Although changes in soil nutrients and increasing temperatures had a negative impact on crop biomass, the phenolic content, a measure of tea quality, did not vary with sites. This suggests that a shift in rooibos farming to cooler and wetter areas further south, for better growth and higher yields, would not compromise the quality of rooibos tea. [ABSTRACT FROM AUTHOR]

Psoraleeae consist of c. 228 species in ten genera, distributed worldwide but mostly in the temperate biome. Here, we reconstruct the phylogenetic history of Psoraleeae using eight molecular markers (rpl32-trnL , trnQ-rps16 , trnS-trnG , matK , rbcLa , rpoB-trnC , trnL-trnF and ITS) to test the monophyly and previous hypotheses on generic relationships and to reconstruct the biogeographical history (distribution pattern, potential ancestral area and biome). The monophyly of Psoraleeae is supported. The African Otholobium and Psoralea form a strongly supported clade that is sister to the rest of Psoraleeae. However, Otholobium is not monophyletic; the American taxa of the genus are resolved as closer to Bituminaria , whereas Psoralea is a clade derived from within African Otholobium. South African Otholobium is subsumed into Psoralea , the latter having priority, with a synopsis of species level nomenclature provided here. An expanded sampling of Cullen reveals three clades comprising Mediterranean (Cullen americanum), African (Cullen obtusifolium and Cullen biflorum) and Eurasian (Cullen corylifolium and Cullen drupaceum) taxa, whereas Australian Cullen are a derived clade (BS = 95%, PP = 1.00). Biogeographic reconstructions show that Psoraleeae probably originated in the Mediterranean south biome of Africa in the Late Miocene, c. 8.2 Mya, and then dispersed into the succulent biome of the Americas, Mediterranean north biome, temperate grasslands of Africa and Australia to the temperate forest of Eurasia. Climate changes in the Late Miocene, changes induced by ocean currents during the Quaternary and environmental heterogeneity are proposed as the major drivers of speciation in Psoraleeae. [ABSTRACT FROM AUTHOR]

Background: The best documented survival responses of organisms to past climate change on short (glacialinterglacial) timescales are distributional shifts. Despite ample evidence on such timescales for local adaptations of populations at specific sites, the long-term impacts of such changes on evolutionary significant units in response to past climatic change have been little documented. Here we use phylogenies to reconstruct changes in distribution and flowering ecology of the Cape flora - South Africa's biodiversity hotspot - through a period of past (Neogene and Quaternary) changes in the seasonality of rainfall over a timescale of several million years. Results: Forty-three distributional and phenological shifts consistent with past climatic change occur across the flora, and a comparable number of clades underwent adaptive changes in their flowering phenology (9 clades; half of the clades investigated) as underwent distributional shifts (12 clades; two thirds of the clades investigated). Of extant Cape angiosperm species, 14-41% have been contributed by lineages that show distributional shifts consistent with past climate change, yet a similar proportion (14-55%) arose from lineages that shifted flowering phenology. Conclusions: Adaptive changes in ecology at the scale we uncover in the Cape and consistent with past climatic change have not been documented for other floras. Shifts in climate tolerance appear to have been more important in this flora than is currently appreciated, and lineages that underwent such shifts went on to contribute a high proportion of the flora's extant species diversity. That shifts in phenology, on an evolutionary timescale and on such a scale, have not yet been detected for other floras is likely a result of the method used; shifts in flowering phenology cannot be detected in the fossil record. [ABSTRACT FROM AUTHOR]