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Molecular Evolutionary Rates (molecular + evolutionary_rate)
Selected AbstractsBURNING PHYLOGENIES: FIRE, MOLECULAR EVOLUTIONARY RATES, AND DIVERSIFICATIONEVOLUTION, Issue 9 2007Miguel Verdú Mediterranean-type ecosystems are among the most remarkable plant biodiversity "hot spots" on the earth, and fire has traditionally been invoked as one of the evolutionary forces explaining this exceptional diversity. In these ecosystems, adult plants of some species are able to survive after fire (resprouters), whereas in other species fire kills the adults and populations are only maintained by an effective post-fire recruitment (seeders). Seeders tend to have shorter generation times than resprouters, particularly under short fire return intervals, thus potentially increasing their molecular evolutionary rates and, ultimately, their diversification. We explored whether seeder lineages actually have higher rates of molecular evolution and diversification than resprouters. Molecular evolutionary rates in different DNA regions were compared in 45 phylogenetically paired congeneric taxa from fire-prone Mediterranean-type ecosystems with contrasting seeder and resprouter life histories. Differential diversification was analyzed with both topological and chronological approaches in five genera (Banksia, Daviesia, Lachnaea, Leucadendron, and Thamnochortus) from two fire-prone regions (Australia and South Africa). We found that seeders had neither higher molecular rates nor higher diversification than resprouters. Such lack of differences in molecular rates between seeders and resprouters,which did not agree with theoretical predictions,may occur if (1) the timing of the switch from seeding to resprouting (or vice versa) occurs near the branch tip, so that most of the branch length evolves under the opposite life-history form; (2) resprouters suffer more somatic mutations and therefore counterbalancing the replication-induced mutations of seeders; and (3) the rate of mutations is not related to shorter generation times because plants do not undergo determinate germ-line replication. The absence of differential diversification is to be expected if seeders and resprouters do not differ from each other in their molecular evolutionary rate, which is the fuel for speciation. Although other factors such as the formation of isolated populations may trigger diversification, we can conclude that fire acting as a throttle for diversification is by no means the rule in fire-prone ecosystems [source] Molecular evidence for dispersal rather than vicariance as the origin of flightless insect species on the Chatham Islands, New ZealandJOURNAL OF BIOGEOGRAPHY, Issue 5 2000Steven A. Trewick Abstract Aim The aim was to use mitochondrial DNA sequence data to test between vicariance and oversea dispersal explanations for the origin of the Chatham Islands biota. Location New Zealand and the Chatham Islands, separated by c. 800 km in the south-west Pacific Ocean. Methods DNA sequences from the mitochondrial gene cytochrome oxidase I (COI) were obtained from four genera of relatively large and flightless insects (Coleoptera, Geodorcus, Mecodema; Orthoptera,Talitropsis; Blattoidea,Celatoblatta). These were used to test alternative hypotheses for the origin of the Chatham taxa. Results Phylogenetic analysis revealed the Chatham taxa in each genus to be monophyletic. Genetic distances exhibited by these genera, between taxa found on the Chatham Islands and mainland New Zealand were relatively low (11.2, 2.8, 3.0 and 4.9%, respectively). Main conclusions Even allowing for variation in molecular evolutionary rates, these genetic distances indicate phylogenetic separation of New Zealand and Chatham insect lineages in the Pliocene (2,6 Ma). Such dates are more than one order of magnitude too recent to be explained by vicariant (tectonic) processes. Oversea dispersal from New Zealand to the Chatham Islands is implicated and this conclusion is in keeping with the taxonomy of the endemic avifauna, flora and fossil molluscan fauna. [source] The influence of environmental factors, the pollen : ovule ratio and seed bank persistence on molecular evolutionary rates in plantsJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 1 2006C.-A. WHITTLE Abstract One of the main goals of molecular evolutionary biology is to determine the factors that influence the evolutionary rate of selectively neutral DNA, but much remains unknown, especially for plants. Key factors that could alter the mutation rate include environmental tolerances (because they reflect a plants vulnerability to changes in habitat), the pollen : ovule ratio (as it is associated with the number of mitotic divisions) and seed longevity (because this influences the number of generations per unit time in plants). This is the first study to demonstrate that seed bank persistence and drought tolerance are positively associated with molecular evolutionary rates in plants and that pollen : ovule ratio, shade tolerance and salinity tolerance have no detectable relationship. The implications of the findings to our understanding of the impact of environmental agents, the number of cell divisions and cell aging on neutral DNA sequence evolution are discussed. [source] | ||||||||||