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Wattles and Wombats: Molecular rate variation and Biodiversity Xavier Goldie The University of Auckland The Australian National University
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Outline: Biodiversity and Evolution Evolutionary Speed in Australian Plants Evolutionary Speed Hypothesis Productivity and the Water-Energy Balance Outcomes Molecular rates in Mammals Diversification and molecular rates: crash course Outcomes
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Biodiversity and Evolution What drives diversification? SPECIATION - EXTINCTION Why are species unevenly distributed - Spatially? Phylogenetically? Temporally?
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Rodents Lagomorphs Primates + Cetartiodactyla + Carnivora + Chiroptera Shrews and stuff Xenarthra Afrotheria Metatheria
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Evolutionary Speed in Australian Plants Climate and Biodiversity
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Rohde’s Evolutionary Speed Hypothesis (ESH) Bromham and Cardillo 2003
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Rohde’s ESH deals specifically with the relationship between global temperature and biodiversity However… Terrestrial biodiversity is linked most tightly to the interaction of temperature and the physical state of water “Water-Energy Balance” (Hawkins et al 2003) “Productivity” (Gillman and Wright, 2006)
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Is Rohde’s ESH applicable to gradients of water availability?
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Species RichnessRainfallProductivity
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Amyema congener Amyema maidenii “Wet” “Dry”
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30 Phylogenetically Independent contrasts Branch length Trait P.A. Branch length Trait
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Significantly more (23 of 30) comparisons resulted in longer “Wet” branch lengths (Sign Test: P = 0.005) The rate of nucleotide substitution in “Wet” zone taxa was on average more than twice that of closely related “Dry” zone congeners (Wilcoxon Signed Rank Test: W = 93, P = 0.003). Goldie et al., 2010
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Results are consistent with the evolutionary speed hypothesis Optimised water-energy balance may act to increase micro-evolutionary rates in mesic areas Arid conditions may lead to slower tempo of micro-evolution
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Bromham and Cardillo 2003 Rohde’s Evolutionary Speed Hypothesis
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Molecular Rates Speciation Rates Wright et al 2006 Lanfear et al In Prep Webster et al 2003 Pagel et al 2006
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Molecular Rates in Mammals
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What is the relationship between the rate of molecular evolution, and diversification, in mammals?
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Whole Mitochondrial Genomes and Nuclear Genes Estimated Synonymous, Non-Synonymous and total substitution rates (MG94_REV_3x4 in HyPHY) Mitochondrial Sister-clades at roughly ordinal, familial and generic level Nuclear Sister-Clades in Mammalia, Eutheria, Metatheria, Euarchontoglires and Laurasiatheria Sign-Tests and Parametric Regression Included Body Size in Multiple Regression
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N e and/or Selection Mutation Clade A Clade B Clade A Clade B dN dS -- dN/dS -- Brlen
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No consistent relationship between molecular rates and clade size - mitochondrial or nuclear Body Size Effect detected in nuclear genes, but not in mitochondrial Saturated Synonymous Rates in mitochondrial genes “RY” Coded four-fold degenerate sites - record only synonymous Transversions (T or C ↔ G or A) No relationship (Goldie et al, In Prep)
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Eutheria ML Brlen versus Clade Size P = 0.00545 But not repeated in dN or dS
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Welch et al 2007 P = 0.1260 Mitochondrial dS
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BUT WHAT DOES IT ALL MEAN?
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Lack of apparent relationship between mammalian molecular rates and diversification rates? Molecular rates are not central to the diversification process in mammals Different process operating between plants and mammals - has been suggested But why birds, and not mammals?
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Gillman et al 2009 Higher rates of molecular evolution in tropical mammals versus temperate PICs Interpreted as support for Evolutionary Speed Hypothesis driving Latitudinal Species Gradients Bassariscus astustusBassariscus sumichrasti
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Rohde’s ESH Bromham and Cardillo, 2003
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Acknowledgements: Shane Wright Len Gillman Lindell Bromham Rob Lanfear Nga Pae O Te Maramatanga Maori Centre of Research Excellence The Australian National University
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Questions?
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