DIVERSIFICATION OF THE AFRICAN GENUS PROTEA (PROTEACEAE) IN THE CAPE BIODIVERSITY HOTSPOT AND BEYOND: EQUAL RATES IN DIFFERENT BIOMES

The Cape region of South Africa is a hotspot of flowering plant biodiversity. However, the reasons why levels of diversity and endemism are so high remain obscure. Here, we reconstructed phylogenetic relationships among species in the genus Protea, which has its center of species richness and endemism in the Cape, but also extends through tropical Africa as far as Eritrea and Angola. Contrary to previous views, the Cape is identified as the ancestral area for the radiation of the extant lineages: most species in subtropical and tropical Africa are derived from a single invasion of that region. Moreover, diversification rates have been similar within and outside the Cape region. Migration out of the Cape has opened up vast areas, but those lineages have not diversified as extensively at fine spatial scales as lineages in the Cape. Therefore, higher net rates of diversification do not explain the high diversity and endemism of Protea in the Cape. Instead, understanding why the Cape is so diverse requires an explanation for how Cape species are able to diverge and persist at such small spatial scales.     

The use of mean pool abundances to interpret 15N tracer experiments

A pulse dilution ¹⁵N technique was used in the field to determine the effect of the ammonium to nitrate ratio in a fertilizer application on the uptake of ammonium and nitrate by ryegrass and on gross rates of mineralization and nitrification. Two experiments were performed, corresponding approximately to the first and second cuts of grass. Where no substantial recent immobilization of inorganic nitrogen had occurred, mineralization was insensitive to the form of nitrogen applied, ranging from 2.1–2.6 kg N ha^-1 d^-1. The immobilization of ammonium increased as the proportion of ammonium in the application increased. In the second experiment there was evidence that high rates of immobilization in the first experiment were associated with high rates of mineralization in the second. The implication was that some nitrogen immobilized in the first experiment was re-mineralized during the second. Whether this was nitrogen taken up, stored in roots and released following defoliation was not clear. Nitrification rates in this soil were low (0.1–0.63 kg N ha^-1 d^-1), and as a result, varying the ratio of ammonium to nitrate applied markedly altered the relative uptake of ammonium and nitrate. In the first experiment, where temperatures were low, preferential uptake of ammonium occurred, but where >90% of the uptake was as ammonium, a reduction in yield and nitrogen uptake was observed. In the second experiment, where temperatures and growth rates were higher, the proportion of ammonium to nitrate taken up had no effect on yield or nitrogen uptake.     

Calcium-ion binding by the potential calcium-ion-binding protein, p9Ka

p9Ka is a polypeptide of apparent molecular mass 9 kDa, present in cultured rat mammary myoepithelial-like cells, but virtually absent in their parental epithelial cells. mRNA for p9Ka is present in normal rodent tissues. The amino acid sequence of a protein of molecular mass 12 KDa, derived from the nucleotide sequence of the p9Ka gene, is related to that of S-100 protein, a calcium-ion-binding protein. p9Ka, isolated from cultured rat mammary myoepithelial-like cells is now shown to bind calcium ions in vitro suggesting that the derived amino acid sequence is correct, and that an apparent discrepancy between the molecular masses of the predicted and isolated p9Ka does not affect this activity.     

Life events and breast cancer prognosis.

OBJECTIVE--To determine whether psychosocial stress, in the form of adverse life events and social difficulties, depressive illness, or lack of confiding relationships, shortens the postoperative disease free interval in breast cancer patients. DESIGN--Prospective follow up of a cohort of newly diagnosed breast cancer patients for 42 months after primary surgical treatment, using a life events and social difficulties schedule (LEDS) and assessment of depressive symptomatology (DSM-III). SETTING--Patients recruited from breast clinics in Southampton and Portsmouth were interviewed in their homes. PATIENTS--204 women (83% of 246 consecutive cases) treated either by mastectomy or wide excision followed by radiotherapy interviewed four, 24, and 42 months after operation. MAIN OUTCOME MEASURES--Hazard ratios for relapse of breast cancer in relation to various measures of psychosocial stress. Relapse was defined as local recurrence or distant metastasis, or both, with histological or radiological confirmation and timed from the month when clinical symptoms began. RESULTS--After adjustment for age and axillary lymph node involvement, the hazard ratio associated with severe life events or social difficulties (excluding "own health" ones), or both, during the year before breast cancer surgery was 0.43 (95% confidence interval 0.20 to 0.93); for those during the follow up period it was 0.88 (0.48 to 1.64). For prolonged major depression before surgery and during the follow up period, hazard ratios were 1.26 (0.49 to 3.26) and 0.85 (0.41 to 1.79) respectively. For absence of a full confidant the figures were 0.93 (0.42 to 2.09) and 0.86 (0.38 to 1.93). CONCLUSION--These results give no support to the theory that psychosocial stress contributes to relapse of breast cancer.     

Short communication. Do dicotyledons generate greater maximum axial root growth pressures than monocotyledons?

Roots of dicotyledons (dicots) have often been observed to grow better in strong soil than monocotyledons (moncots), and it has been suggested that this could be due to the dicots generating greater root growth pressures. Experiments were therefore carried out to measure the maximum axial root growth pressure (max than monocots: the mean for dicots was 0.41 MPa; the mean for monocots was 0.44 MPa.     

On the reality and recognisability of asexual organisms: morphological analysis of the masticatory apparatus of bdelloid rotifers

Species concepts and definitions have been a long-standing debate in evolutionary biology since before Darwin, and almost all proposed solutions are based upon grouping and clustering, with species conceived as somehow biological distinct entities, originated and maintained mainly by reproductive isolation. Lacking reproductive exchange, asexual organisms such as bdelloid rotifers, the best-supported clade of so-called 'ancient asexuals', pose an interesting challenge to debates over the reality of species. However, few data are available on bdelloid rotifers. The only evidence has been that bdelloid species have been more consistently recognised than in their sister sexual group, the monogonont rotifers, across successive taxonomic treatments, but this is confounded by the much lesser degree of taxonomic interest in bdelloids. We applied geometric morphometrics analyses on shape and size of hard masticatory pieces, named trophi, of 1420 bdelloids, belonging to 48 populations of eight traditional species, to test the hypothesis of recognisability of bdelloids. Our morphological analysis confirms that traditional bdelloid species are separated distinct entities, possessing trophi morphologies divided by gaps between taxa, similar to patterns of morphological features in sexually reproducing organisms. In common with most microscopic understudied organisms, bdelloid rotifers harbour much previously undescribed diversity: we found significant differences in trophi morphology within traditional species, revealing the existence of cryptic taxa, similar to those also found in facultatively sexual monogonont rotifers. We confirm that recognisability in bdelloids is not qualitatively different from other small understudied animals such as monogononts, and that sexual versus asexual reproduction does not lead to differences in morphological diversity patterns, as previously suggested based on interpretation of taxonomic revisions.     

New species of haematozoa from the avian families Campephagidae and Apodidae

Leucocytozoon coracinae sp. nov. is described from the avian family Campephagidae and Hepatozoon apodis sp. nov. from the Apodidae. The distribution of these parasites within their respective families is discussed.     

Biodiversity inhibits species' evolutionary responses to changing environments

Despite growing interplay between ecological and evolutionary studies, the question of how biodiversity influences evolutionary dynamics within species remains understudied. Here, using a classical model of phenotypic evolution in species occupying a patchy environment, but introducing global change affecting patch conditions, we show that biodiversity can inhibit species' evolution during global change. The presence of several species increases the chance that one or more species are pre-adapted to new conditions, which restricts the ecological opportunity for evolutionary responses in all the species. Consequently, environmental change tends to select for changes in species abundances rather than for changing phenotypes within each species. The buffering effects of species diversity that we describe might be one important but neglected explanation for widely observed niche conservatism in natural systems. Furthermore, the results show that attempts to understand biotic responses to environmental change need to consider both ecological and evolutionary processes in a realistically diverse setting.     

Diversification in sexual and asexual organisms

Abstract Sexual reproduction has long been proposed as a major factor explaining the existence of species and species diversity. Yet, the importance of sex for diversification remains obscure because of a lack of critical theory, difficulties of applying universal concepts of species and speciation, and above all the scarcity of empirical tests. Here, we use genealogical theory to compare the relative tendency of strictly sexual and asexual organisms to diversify into discrete genotypic and morphological clusters. We conclude that asexuals are expected to display discrete clusters similar to those found in sexual organisms. Whether sexuals or asexuals display stronger clustering depends on a number of factors, but in at least some scenarios asexuals should display a stronger pattern. Confounding factors aside, the only explanation we identify for stronger patterns of diversification in sexuals than asexuals is if the faster rates of adaptive change conferred by sexual reproduction promote greater clustering. Quantitative comparisons of diversification in related sexual and asexual taxa are needed to resolve this issue. The answer should shed light not only on the importance of the different stages leading to diversification, but also on the adaptive consequences of sex, still largely unexplored from a macroevolutionary perspective.     

Radiation in the Cape flora and the phylogeny of peacock irises Moraea (Iridaceae) based on four plastid DNA regions

Phylogenetic analyses of four plastid DNA regions, the rbcL exon, trnL intron, trnL-trnF intergenic spacer, and rps16 intron from each of 73 species in the African genus Moraea (Iridaceae: Irideae) including accessions of all major species clusters in the genus, show Moraea to be paraphyletic when Barnardiella, Galaxia, Hexaglottis, Homeria (all southern African), and Gynandriris (Eurasian as well) were recognized as separate genera. There are several small, isolated species clusters at the basal nodes of the tree that are all restricted to the winter-rainfall zone of southern Africa (the Greater Cape floral kingdom) and a few, highly derived, large species groups that have radiated extensively within the winter-rainfall zone. Mapping of floral traits shows that an Iris-type flower is ancestral in Moraea. Floral changes are associated with shifts in pollination systems, either from passive pollen deposition on long-tongued bees foraging for nectar to active pollen collection by female bees foraging for pollen, fly, or hopliine scarab beetle pollination. Dating the nodes of the phylogenetic tree using non-parametric rate smoothing with a calibration point derived from broad dating of the angiosperms indicates that the divergence between Moraea and its sister genus Ferraria occurred about 25 mya in the early Miocene. The early radiation of Moraea took place against a background of aridification and the spread of open habitats, such as desert, shrubland, and fynbos.