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Wattles and Wombats:
Molecular rate variation and Biodiversity
Xavier Goldie
The University of AucklandThe Australian National University
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
Biodiversity and Evolution
• What drives diversification?
SPECIATION - EXTINCTION
• Why are species unevenly distributed -
• Spatially?
• Phylogenetically?
• Temporally?
Rodents
Lagomorphs
Primates +
Cetartiodactyla +
Carnivora +
Chiroptera
Shrews and stuff
Xenarthra
Afrotheria
Metatheria
Evolutionary Speed in Australian Plants
Climate and Biodiversity
Rohde’s Evolutionary Speed Hypothesis (ESH)
Bromham and Cardillo 2003
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)
Is Rohde’s ESH applicable to gradients of water availability?
Species RichnessRainfallProductivity
Amyema congener
Amyema maidenii
“Wet”
“Dry”
30 Phylogenetically Independent contrasts
Branch length Trait
P.A.
Branch length Trait
Branch length Trait
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
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
Bromham and Cardillo 2003
Rohde’s Evolutionary Speed Hypothesis
Molecular Rates
Speciation Rates
Wright et al 2006Lanfear et al In Prep
Webster et al 2003Pagel et al 2006
Molecular Rates in Mammals
What is the relationship between the rate of molecular evolution,
and diversification,in mammals?
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
Ne and/or Selection
Mutation
Clade A Clade B Clade A Clade B
dN
dS - -
dN/dS - -
Brlen
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)
Eutheria
ML Brlen versus Clade Size
P = 0.00545
But not repeated in dN or dS
Welch et al 2007
P = 0.1260
Mitochondrial dS
BUT WHAT DOES IT ALL MEAN?
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?
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 astustus Bassariscus sumichrasti
Rohde’s ESH
Bromham and Cardillo, 2003
Acknowledgements:
Shane Wright
Len Gillman
Lindell Bromham
Rob Lanfear
Nga Pae O Te Maramatanga Maori Centre of Research Excellence
The Australian National University
Questions?