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- Sauquet, Herve, et al.
(author)
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Contrasted patterns of hyperdiversification in Mediterranean hotspots
- 2009
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In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 106:1, s. 221-225
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Journal article (peer-reviewed)abstract
- Dating the Tree of Life has now become central to relating patterns of biodiversity to key processes in Earth history such as plate tectonics and climate change. Regions with a Mediterranean climate have long been noted for their exceptional species richness and high endemism. How and when these biota assembled can only be answered with a good understanding of the sequence of divergence times for each of their components. A critical aspect of dating by using molecular sequence divergence is the incorporation of multiple suitable age constraints. Here, we show that only rigorous phylogenetic analysis of fossil taxa can lead to solid calibration and, in turn, stable age estimates, regardless of which of 3 relaxed clock-dating methods is used. We find that Proteaceae, a model plant group for the Mediterranean hotspots of the Southern Hemisphere with a very rich pollen fossil record, diversified under higher rates in the Cape Floristic Region and Southwest Australia than in any other area of their total distribution. Our results highlight key differences between Mediterranean hotspots and indicate that Southwest Australian biota are the most phylogenetically diverse but include numerous lineages with low diversification rates.
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- Sauquet, Herve, et al.
(author)
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Using fossils and molecular data to reveal the origins of the Cape proteas (subfamily Proteoideae)
- 2009
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In: Molecular Phylogenetics and Evolution. - : Elsevier BV. - 1055-7903 .- 1095-9513. ; 51:1, s. 31-43
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Journal article (peer-reviewed)abstract
- The angiosperm family Proteaceae is a distinct component of the Cape Floristic Region biodiversity hot-spot with 330 endemic species. Phylogenetic analyses of subfamily Proteoideae using sequence data from one nuclear and six plastid loci show that most of this diversity is contained in two distinct Cape floral clades. Molecular dating analyses, using Bayesian and penalized likelihood methods and four phylogenetically supported fossil age constraints. reveal contrasting histories for these two clades. The genus Protea belongs to a lineage that may have been in Africa since the Late Cretaceous but began to diversify in the Cape only 5-18 Myr ago. In contrast, the Leucadendrinae clade presumably arrived in the region no earlier than 46 Myr ago by long-distance dispersal from an Australian ancestor and the extant members of this clade began to diversify in the Cape 22-39 Myr ago. These results join a growing number of case studies that challenge the commonly accepted view that most of the Cape flora radiated synchronously in the Late Miocene and Early Pliocene when a Mediterranean climate settled in the region. (C) 2008 Elsevier Inc. All rights reserved.
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- Weston, P., et al.
(author)
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The value of both ST-segment and QRS complex changes during acute coronary occlusion for prediction of reperfusion-induced myocardial salvage in a canine model
- 2007
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In: J Electrocardiol. - 1532-8430. ; 40:1, s. 18-25
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Journal article (peer-reviewed)abstract
- BACKGROUND: Analysis of ST-segment elevation for assessment of patients with suspected acute coronary occlusion is in widespread use for diagnostic and prognostic purposes. In this study, changes in the QRS complex also were analyzed to determine if these changes that are seldom used clinically can provide additional prognostic information. An acute coronary occlusion canine model, in which direct measurements of myocardial salvage were made, was used to assess whether ST-segment and QRS complex changes during coronary occlusion yielded independent estimates of the amount of salvage provided by reperfusion with arterial blood. METHODS AND RESULTS: Continuous electrocardiographic recordings were obtained from 14 study dogs undergoing a 90-minute period of coronary artery occlusion in which the severity of the ischemia during the occlusion was estimated at 10 and 45 minutes by microsphere injections. After 3 hours of reperfusion, the myocardium at risk and postmortem infarct size was measured. Myocardial salvage correlated inversely with both ST-segment elevation (r = -0.85; P < .0001), and QRS complex prolongation (r = -0.72; P = .003). When dogs were paired so that they had equal amounts of ST elevation but differed with respect to the presence of QRS prolongation, less myocardial salvage was found in those with QRS prolongation. The independent value of QRS prolongation was supported further by the observation that presence of QRS prolongation resulted in a loss of the highly significant correlation between ST elevation and salvage (r = -0.60; P = .2). CONCLUSIONS: High magnitudes of ST elevation are correlated significantly with less myocardial salvage. Moreover, for a given magnitude of ST elevation, the presence of concurrent QRS prolongation is associated with even less myocardial salvage.
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