wattles and wombats: molecular rate variation and biodiversity xavier goldie the university of...

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?