Climate cooling promoted the expansion and radiation of a threatened group of South American orchids (Epidendroideae: Laeliinae)

The Brazilian Cerrado is the most species‐rich tropical savanna in the world. Within this biome, the Campos Rupestres (‘rocky savannas’) constitute a poorly studied and highly threatened ecosystem. To better understand how plants characteristic of this vegetation have evolved and come to occupy the now widely‐separated patches of rocky formations in eastern Brazil, we reconstruct the biogeographical history of the rare orchid genus Hoffmannseggella. We apply parsimony and Bayesian methods to infer the phylogenetic relationships among 40 out of the 41 described species. Absolute divergence times are calculated under penalized likelihood and compared with estimates from a Bayesian relaxed clock. Ancestral ranges are inferred for all nodes of the phylogeny using Fitch optimization and statistical dispersal vicariance analysis. In all analyses, phylogenetic uncertainty is taken into account by the independent analysis of a large tree sample. The results obtained indicate that Hoffmannseggella underwent rapid radiation around the Middle/Late Miocene (approximately 11–14 Mya). The region corresponding today to southern Minas Gerais acted as a main source area for several independent range expansions north‐ and eastwards via episodic corridors. These results provide independent evidence that climate cooling following the Middle Miocene Climatic Optimum (approximately 15 Mya) led to important vegetational shifts in eastern Brazil, causing an increase in the dominance of open versus closed habitats. Polyploidy following secondary contact of previously isolated populations may have been responsible for the formation of many species, as demonstrated by the high ploidy levels reported in the genus. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 597–607.     

Studies on Differentiation without Cleavage in Chaetopterus: Effects of Inhibition of DNA Synthesis with Aphidicolin

The effects of aphidicolin – a powerful inhibitor of DNA polymerase α and of DNA replication – on normal development and on differentiation without cleavage of Chaetopterus eggs have been studied with cytological, cytochemical, and biochemical methods. The experiments show that the initial period of pseudocleavage can take place in the absence of nuclear DNA synthesis, but further development (segregation, hatching, ciliation) requires DNA synthesis. However ciliated unicellular larvae can be obtained under conditions where the DNA content of the embryos in only 40% of the controls. In fertilized eggs, aphidicolin immediately stops cleavage. The significance of these results is discussed.     

Three‐dimensional flight tracking shows how a visual target alters tsetse fly responses to human breath in a wind tunnel

Tsetse flies Glossina spp. (Diptera; Glossinidae) are blood‐feeding vectors of disease that are attracted to vertebrate hosts by odours and visual cues. Studies on how tsetse flies approach visual devices are of fundamental interest because they can help in the development of more efficient control tools. The responses of a forest tsetse fly species Glossina brevipalpis (Newstead) to human breath are tested in a wind tunnel in the presence or absence of a blue sphere as a visual target. The flight responses are video recorded with two motion‐sensitive cameras and characterized in three dimensions. Although flies make meandering upwind flights predominantly in the horizontal plane in the plume of breath alone, upwind flights are highly directed at the visual target presented in the plume of breath. Flies responding to the visual target fly from take‐off within stricter flight limits at lower ground speeds and with a significantly lower variance in flight trajectories in the horizontal plane. Once at the target, flies fly in loops principally in the horizontal plane within 40 cm of the blue sphere before descending in spirals beneath it. Successful field traps designed for G. brevipalpis take into account the strong horizontal component in local search behaviour by this species at objects. The results suggest that trapping devices should also take into account the propensity of G. brevipalpis to descend to the lower parts of visual targets.     

Owl melanin‐based plumage redness is more frequent near than away from the equator: implications on the effect of climate change on biodiversity

Climate change acts as a major new selective agent on many organisms, particularly at high latitudes where climate change is more pronounced than at lower latitudes. Studies are required to predict which species are at a high risk of extinction and whether certain phenotypes may be more affected by climate change than others. The identification of susceptible phenotypes is important for evaluating the potential negative effect of climate change on biodiversity at the inter‐ and intraspecific levels. Melanin‐based coloration is an interesting and easily accessible candidate trait because, within certain species, reddish pheomelanin‐based coloration is associated with adaptations to warm climates. However, it is unclear whether the same holds among species. We tested one prediction of this hypothesis in four owl genera (wood, scops, screech, and pygmy owls), namely that darker reddish species are more prevalent near the equator than polewards. Our comparative analysis is consistent with this prediction for the northern hemisphere, suggesting that pale reddish species may be adapted to cold climates and dark reddish species to warmer climates. Thus, climate change may have a larger negative impact on pale pheomelanic owls and favour dark pheomelanic species. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 573–582.     

Long‐term breeding demography and density dependence in an increasing population of Golden Eagles Aquila chrysaetos

Few studies have quantified the dynamics of recovering populations of large raptors using long‐term, spatially explicit studies. Using data collected over 37 years in the western Italian Alps, we assessed the trends in distribution, abundance, fecundity and breeding population structure of Golden Eagles Aquila chrysaetos. Using the spatial distribution of territory centroids in 2007, we found that the spatial distribution of eagle territories was over‐dispersed up to 3 km. Although population size and total productivity increased from 1972 to 2008, the proportion of pairs that laid eggs showed a strong decline, falling to no more than 50% after 2003. On average, 15% of successful nests produced two fledglings, and productivity also declined over time. No significant relationship between population growth rate and total population size was detected, but the percentage of pairs that bred and breeding success showed evidence of density dependence, as they declined significantly with increasing density. Our results suggest that density dependence, operating across heterogeneous habitats, is currently regulating this population, while the carrying capacity may still be increasing. This may explain the apparent paradox of reduced breeding effort despite increasing total productivity.