Species diversity is unequally distributed across the globe,with the greatest concentration occurring in the tropics. Even within the tropics, there are significant differences in the numbers of taxa found in each continental region. Manilkara is a pantropical genus of trees in the Sapotaceae comprising c.78 species. Its distribution allows for biogeographic investigation and testing of whether rates of diversification differ amongst tropical regions. The age and geographical origin of Manilkara are inferred to determine whether Gondwanan break-up, boreotropical migration or long distance dispersal have shaped its current disjunct distribution. Diversification rates through time are also analyzed to determine whether the timing and tempo of speciation on each continent coincides with geoclimatic events. Bayesian analyses of nuclear (ITS) and plastid (rpl32-trnL,rps16-trnK,and trnS-trnFM) sequences were used to reconstruct a species level phylogeny of Manilkara and related genera in the tribe Mimusopeae. Analyses of the nuclear data using a fossil-calibrated relaxed molecular clock indicate that Manilkara evolved 32–29 million years ago (Mya) in Africa. Lineages within the genus dispersed to the Neotropics 26–18 Mya and to Asia 28–15 Mya. Higher speciation rates are found in the Neotropical Manilkara clade than in either African or Asian clades. Dating of regional diversification correlates with known palaeoclimatic events. In South America, the divergence between Atlantic coastal forest and Amazonian clades coincides with the formation of drier Cerrado and Caatinga habitats between them. In Africa diversification coincides with Tertiary cycles of aridification an duplif tof the east African plateaux. In South east Asia dispersal may have been limited by the relatively recent emergence of land in New Guinea and islands further east c.10 Mya.

Aim. The Cape region is known for its exceptional species richness, although much remains unknown regarding the appearance of the modern Cape flora. One explanation is that floral diversification was influenced by the establishment of winter rainfall/summer arid conditions hypothesized to have occurred towards the end of the Miocene. We studied the evolution and diversification of the plant genus Metalasia (Asteraceae–Gnaphalieae), with the aim of testing whether radiation patterns may have been influenced by the climatic changes.

Location. South Africa, with emphasis on the south-west.

Methods. The radiation of Metalasia was investigated using two approaches: a species diffusion approach, which estimated the ancestral areas by means of a relaxed random walk while sampling from extant distributions; and a discrete approach, in which distributions were defined according to the phytogeographical centres of the Cape region. Secondarily derived clock rates from an earlier Gnaphalieae study were used for calibration purposes.

Results. Our analyses date Metalasia to approximately 6.9 Ma, after the Miocene–Pliocene boundary and the establishment of the winter rainfall/summer arid conditions. Metalasia consists of two sister clades: Clade A and Clade B. Clade B, which is endemic to the winter rainfall area, is estimated to have diversified c. 6.4 Ma, whereas Clade A, with a main distribution in the all-year rainfall area, is considerably younger, with a crown group age estimated to 3.3 Ma. Diversification rates suggest an early rapid speciation, with rates decreasing through time both for Metalasia and for clades A and B separately. Ancestral area estimations show a possible scenario for the radiation of Metalasia to its current diversity and distribution, with no conflict between results inferred from diffusion or discrete methods.

Main conclusions. The diversification of Metalasia is estimated to have begun after the establishment of the winter rainfall/summer arid conditions, consistent with its radiation having been influenced by changes in the climatic regime.

The Lucilia group sensu Anderberg and Freire comprises nine South American genera: Belloa, Berroa, Chevreulia, Cuatrecasasiella, Facelis, Gamochaetopsis, Jalcophila, Lucilia and Luciliocline. The aims of this contribution were, using DNA sequences from plastid (rpl32-trnL, trnL-F) and nuclear (ITS and ETS) markers, together with morphological characters, to test the monophyly of the Lucilia group and provide new insight into generic circumscriptions. Our studies, including a broad taxon sampling of Gnaphalieae species, suggest that the Lucilia group is paraphyletic, since Antennaria, Chionolaena, Gamochaeta, Loricaria, Micropsis, Mniodes and Stuckertiella are all nested within the Lucilia group. Morphology and molecular analyses combined showed that the traditional generic circumscription of most of the genera (e.g., Berroa, Chevreulia, Chionolaena, Cuatrecasasiella, Facelis, Jalcophila and Micropsis) correlates with the inferred phylogenetic relationships. Conversely, Lucilia and Luciliocline are non-monophyletic. Lucilia is nested in a clade with Berroa, Facelis and Micropsis. Luciliocline is strongly embedded within the clade Belloa pp + Mniodes. Our results are consistent with Dillon’s study that considered Belloa as a montotypic genus (B. chilensis). Luciliocline and the remaining species of Belloa are accommodated in the genus Mniodes, and the necessary combinations are proposed for the expanded Mniodes. All the analyses showed that the monotypic genera Stuckertiella and Gamochaetopsis are in a well-supported clade nested within Gamochaeta, which implies that taxonomic changes are required also for these genera. Internal relationships in the group and the key morphological characters used in the taxonomy of the group, as well as incongruences found between morphological and molecular analyses, are discussed.

Sapotaceae belongs to the heterogeneous order Ericales and exhibits extensive diversity in floral morphology. Although pentamery is widespread and probably the ancestral condition, some clades are extremely variable in merism, with fluctuations between tetramery to hexamery and octomery, affecting different floral organs to different degrees. We assessed the different states of merism in Sapotaceae to determine the evolution of this character among different clades. The floral morphology and development of nine species from eight genera were investigated using scanning electron microscopy (SEM). Furthermore, floral characters related to merism were mapped onto a phylogenetic tree to analyse the distribution and evolutionary significance of merism in the family. Developmental evidence shows that changes in merism are linked to a concerted multiplication of organs among whorls and an increase in whorls through the displacement of organs. Although pentamery is reconstructed as the ancestral condition, a reduction to tetramery or an increase to a higher merism (mainly hexamery or octomery) has evolved at least five times in the family. Fluctuations in merism between different whorls are not random but occur in a coordinated pattern, presenting strong synapomorphies for selected clades. Octomery has evolved at least twice, in Isonandreae from tetramery and in Sapoteae-Mimusopinae from pentamery. Hexamery has evolved at least three times, independently in Northia, the Palaquium clade of Isonandreae and derived from octomery in Sapoteae-Mimusopinae. Three possibilities of merism increase have been identified in Sapotaceae: (1) a concerted increase affecting all organs more or less equally (Palaquium clade of Isonandreae, Sapoteae); (2) a coordinated increase in petals, stamens and mostly carpels without effect on sepals (Labourdonnaisia, Payena–Madhuca clade of Isonandreae); (3) an increase in carpels independently of other organs (Burckella, Letestua, Labramia, etc.). A major shift affecting all Sapotaceae, except Isonandreae, is the sterilization or loss of the antesepalous stamen whorl. The presence of two fertile stamen whorls in Isonandreae indicates a possible reversal or a retained plesiomorphy. In a number of genera, stamens are secondarily increased independently of changes in merism. Descriptions of flowers listing only organ numbers are thus misleading in the inference of evolutionary relationships, as they do not differentiate between changes in merism affecting the number of perianth whorls and other changes affecting the androecium, such as sterilization, loss or occasional doubling of antepetalous stamens.

Lactuca indica and Lactuca canadensis have been recorded for the first time in the Americas and in South America, respectively. Lactuca indica is native to Eastern Asia, and L. canadensis to North America. In Brazil, L. indica is used as a substitute for lettuce in some communities. The leaf shape in the Brazilian plants of the two species is less variable than in Asiatic or North American populations. This could possibly be a result of a single introduction to Brazil of each species. Both species are weeds, occurring in disturbed habitats in south and south-eastern Brazil. The two species are described, illustrated and their affinities are discussed. An identification key is provided to the six species of Lactuca (all introduced) in South America.

Phylogenetic relationships in the tribe Inuleae (Asteraceae, sunflower family) are elucidated based on a concatenated set of nuclear (ETS, ITS), and chloroplast data (ndhF, trnL-F, trnH-psbA), analysed by Bayesian and parsimony methods. Extensive sampling of representatives from both subtribes Inuleae-Inulinae and Inuleae-Plucheinae establish their reciprocal monophyly, and result in the first-ever resolved molecular phylogeny of the Inuleae-Plucheinae with new insights into the relationships and morphological character distributions between genera and among species. Of the 31 accepted genera in the Inuleae-Plucheinae, only Pseudoblepharispermum is not represented in this study, 12 monotypic genera are placed in the phylogeny, 13 genera are shown to be monophyletic, and only 5 of the remaining 18 genera are revealed to be polyphyletic. The implications for the nomenclature status of the monotypic and polyphyletic genera are discussed, together with a descriptive review of morphological characters traditionally used to circumscribe the genera in this subtribe.

Reconstructing the biogeographic history of groups present in continuous arid landscapes is challenging dueto the difficulties in defining discrete areas for analyses, and even more so when species largely overlap both in terms ofgeography and habitat preference. In this study, we use a novel approach to estimate ancestral areas for the small plantgenus Centipeda. We apply continuous diffusion of geography by a relaxed random walk where each species is sampledfrom its extant distribution on an empirical distribution of time-calibrated species-trees. Using a distribution of previouslypublished substitution rates of the internal transcribed spacer (ITS) for Asteraceae, we show how the evolution of Centipedacorrelates with the temporal increase of aridity in the arid zone since the Pliocene. Geographic estimates of ancestral speciesshow a consistent pattern of speciation of early lineages in the Lake Eyre region, with a division in more northerly andsoutherly groups since ∼840 ka. Summarizing the geographic slices of species-trees at the time of the latest speciation event(∼20 ka), indicates no presence of the genus in Australia west of the combined desert belt of the Nullabor Plain, the GreatVictoria Desert, the Gibson Desert, and the Great Sandy Desert, or beyond the main continental shelf of Australia. Theresult indicates all western occurrences of the genus to be a result of recent dispersal rather than ancient vicariance. Thisstudy contributes to our understanding of the spatiotemporal processes shaping the flora of the arid zone, and offers asignificant improvement in inference of ancestral areas for any organismal group distributed where it remains difficult todescribe geography in terms of discrete areas.

We investigated the historical biogeography of the Inuleae–Plucheinae (Asteraceae), a group of arid-adapted plants with partly unresolved generic circumscriptions, in order to understand its origin and spatiotemporal evolutionary history in relation to the Cenozoic climate shifts. Location Global, with highest species diversity in the Southern Hemisphere. The spatiotemporal biogeography of the Plucheinae was estimated by both a discrete method using a set of general distribution areas, and a relaxed random walk based on extant species distributions. The topology was time calibrated using a combination of secondary node ages and secondary derived rates for included loci. Our results indicate the median age of the Plucheinae to be approximately 15.4 Ma. The biogeographical analyses infer an ancestral origin in southern Africa, with the relaxed random walk analysis narrowing the uncertainty down to an area reaching from coastal Namibia to the western Kalahari. Africa was colonized in a (south)western–(north)eastern direction following the spread of arid habitats. Ancestral representatives of the Plucheinae colonized South America on at least three separate occasions (13.0–4.0, 4.3–3.1 and 4.1–3.7 Ma), with one subsequent spread to North America. Australia was colonized three times between 3.6 and 0.4 Ma. Madagascar and the Mascarenes were colonized at least seven times. The origin of the Plucheinae is estimated to the Namib region, with early speciations and radiations concurring with the timing of aridification of southern Africa, following the increase in strength of the Antarctic Circumpolar Current and subsequent formation of the Benguela Upwelling at c. 11.8 Ma. The current biogeographical distribution of the Plucheinae is best explained by several Neogene long-distance dispersal events from tropical Africa.

Gamochaeta (tribe Gnaphalieae, Asteraceae) is composed of ca. 60 species primarily distributed in tropical and subtropical America. Within the tribe Gnaphalieae, the genus is characterized by capitula arranged in spikes or head-like clusters, few hermaphroditic central florets, truncate style branches with apical sweeping trichomes, pappus bristles connate at the base into a ring falling as a unit, and achenes with globose twin trichomes. Previous molecular phylogenetic studies have suggested the paraphyly of the genus, but have not provided a basis for redefining generic limits due to incomplete taxon sampling. To address this problem, DNA sequences from the plastid (trnL-F) and nuclear (ETS and ITS) genomes were analyzed from a broad taxon sample representing the full range of morphological variation known in the genus. Our results affirm that Gamochaeta is paraphyletic as presently circumscribed. Two clades can be recognized: one clade that includes the majority of the species currently assigned to Gamochaeta and a second clade that includes Gamochaetopsis, Stuckertiella and seven species of Gamochaeta. We present here a new circumscription of Gamochaeta, including two new combinations, Gamochaeta alpina and Gamochaeta peregrina, and the resurrection of Gamochaeta capitata. Our results also show Omalotheca supina, O. norvegica and O. sylvatica, which were placed by some authors in Gamochaeta or in Gnaphalium, form a monophyletic group distantly related to both genera.