The global increase in species richness toward the tropics across continents and taxonomic groups, referred to as the latitudinal diversity gradient, stimulated the formulation of many hypotheses to explain the underlying mechanisms of this pattern. We evaluate several of these hypotheses to explain spatial diversity patterns in a butterfly family, the Nymphalidae, by assessing the contributions of speciation, extinction, and dispersal, and also the extent to which these processes differ among regions at the same latitude. We generate a time-calibrated phylogeny containing 2,866 nymphalid species (~45% of extant diversity). Neither speciation nor extinction rate variations consistently explain the latitudinal diversity gradient among regions because temporal diversification dynamics differ greatly across longitude. The Neotropical diversity results from low extinction rates, not high speciation rates, and biotic interchanges with other regions are rare. Southeast Asia is also characterized by a low speciation rate but, unlike the Neotropics, is the main source of dispersal events through time. Our results suggest that global climate change throughout the Cenozoic, combined with tropical niche conservatism, played a major role in generating the modern latitudinal diversity gradient of nymphalid butterflies.

BackgroundButterflies of the subtribe Mycalesina (Nymphalidae: Satyrinae) are important model organisms in ecology and evolution. This group has radiated spectacularly in the Old World tropics and presents an exciting opportunity to better understand processes of invertebrate rapid radiations. However, the generic-level taxonomy of the subtribe has been in a constant state of flux, and relationships among genera are unknown. There are six currently recognized genera in the group. Mycalesis, Lohora and Nirvanopsis are found in the Oriental region, the first of which is the most speciose genus among mycalesines, and extends into the Australasian region. Hallelesis and Bicyclus are found in mainland Africa, while Heteropsis is primarily Madagascan, with a few species in Africa. We infer the phylogeny of the group with data from three genes (total of 3139 bp) and use these data to reconstruct events in the biogeographic history of the group.ResultsThe results indicate that the group Mycalesina radiated rapidly around the Oligocene-Miocene boundary. Basal relationships are unresolved, but we recover six well-supported clades. Some species of Mycalesis are nested within a primarily Madagascan clade of Heteropsis, while Nirvanopsis is nested within Lohora. The phylogeny suggests that the group had its origin either in Asia or Africa, and diversified through dispersals between the two regions, during the late Oligocene and early Miocene. The current dataset tentatively suggests that the Madagascan fauna comprises two independent radiations. The Australasian radiation shares a common ancestor derived from Asia. We discuss factors that are likely to have played a key role in the diversification of the group.ConclusionsWe propose a significantly revised classification scheme for Mycalesina. We conclude that the group originated and radiated from an ancestor that was found either in Asia or Africa, with dispersals between the two regions and to Australasia. Our phylogeny paves the way for further comparative studies on this group that will help us understand the processes underlying diversification in rapid radiations of invertebrates.

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Black Economic Empowerment has been one of the South African government's primary mechanisms for addressing the economic imbalances of the apartheid era. Voluntary sector "charters", and more recently legislation, have required largely white owned business enterprises to become more inclusive across key areas of economic empowerment, including the provision of minimum levels of ownership for black shareholders. This research employs event study methodology to examine the long-term impact on the share prices of listed companies after announcements are made relating to black empowerment deals which impact equity ownership. The research examines 118 announcements and finds a positive cumulative abnormal return of around 10% after the first year. The positive result is confined to smaller companies, with market capitalisation of less than R3,5bn, whilst large companies experience a marginally negative cumulative abnormal return. The results also show that those companies which made BEE announcements prior to May 2005 ('first-movers') did somewhat worse than those who followed. Finally, the results were found to be consistent for companies making further BEE related announcements, although the cumulative abnormal returns were lower at around 6%.

Aim Our objective was to reconstruct a species‐level phylogeny of the genus Delias, to elucidate their finer‐scale biogeography and to test boundaries between closely related taxa. Location Indo‐Australian region, with a focus on Wallacea. Methods Sequence data from 131 taxa, representing all recognized species groups and more than half of the known species of Delias, were used in the analysis. Phylogenetic analyses based on molecular characters of the mitochondrial gene cytochrome c oxidase subunit I (COI) and nuclear genes wingless and elongation factor 1α (EF‐1α) were carried out using maximum parsimony and Bayesian inference. Biogeographical reconstructions were undertaken using the parsimony‐based method dispersal–vicariance analysis and the dispersal–extinction–cladogenesis model as implemented in rasp and Lagrange, respectively. Results The phylogenetic hypothesis resolved 14 distinct clades, here designated the nysa, isse, pasithoe, belladonna, ladas, geraldina, aroae, eichhorni, sagessa, aganippe, hyparete, belisama, albertisi and nigrina species groups. Delias blanca Felder and Delias chrysomelaena Snellen van Vollenhoven were transferred to the pasithoe and isse species groups, respectively. We demonstrate that the barcode region of COI is useful for the delineation of closely related, more recently diverged, Delias species. Species diversification in Delias, for the most part, is shown to pre‐date the Pleistocene, even in montane mainland New Guinea where numerous phenotypically similar sister species co‐occur. Main conclusions Sibling Delias species found in sympatry are largely restricted to those clades confined to mainland New Guinea, where most species occur in high‐elevation habitats. Conversely, clades with large geographical ranges are composed of essentially allopatric taxa. Although an Australian Plate origin is plausible for the genus, Delias is likely to have colonized islands peripheral to Australia during the early stages of its evolution (i.e. during the Miocene), as evidenced by the presence of older lineages in Wallacea and also in islands of the south‐western Pacific.