EVOLUTION ON A VOLCANIC CONVEYOR BELT - USING PHYLOGEOGRAPHIC RECONSTRUCTIONS AND K-AR-BASED AGES OF THE HAWAIIAN-ISLANDS TO ESTIMATE MOLECULAR EVOLUTIONARY RATES
Rc. Fleischer et al., EVOLUTION ON A VOLCANIC CONVEYOR BELT - USING PHYLOGEOGRAPHIC RECONSTRUCTIONS AND K-AR-BASED AGES OF THE HAWAIIAN-ISLANDS TO ESTIMATE MOLECULAR EVOLUTIONARY RATES, Molecular ecology, 7(4), 1998, pp. 533-545
The Hawaiian Islands form as the Pacific Plate moves over a 'hot spot'
in the earth's mantle where magma extrudes through the crust to build
huge shield volcanos. The islands subside and erode as the plate carr
ies them to the north-west, eventually to become coral atolls and seam
ounts. Thus islands are ordered linearly by age, with the oldest islan
ds in the north-west (e.g. Kauai at 5.1 Ma) and the youngest in the so
uth-east (e.g. Hawaii at 0.43 Ma). K-Ar estimates of the date of an is
land's formation provide a maximum age for the taxa inhabiting the isl
and. These ages can be used to calibrate rates of molecular change und
er the following assumptions: (i) K-Ar dates are accurate; (ii) tree t
opologies show that derivation of taxa parallels the timing of island
formation; (iii) populations do not colonize long after island emergen
ce; (iv) the coalescent point for sister taxa does not greatly predate
the formation of the colonized younger island; (v) saturation effects
and (vi) among-lineage rate variation are minimal or correctable; and
(vii) unbiased standard errors of distances and regressions can be es
timated from multiple pairwise comparisons. We use the approach to obt
ain overall corrected rate calibrations for: (i) part of the mitochond
rial cytochrome b gene in Hawaiian drepanidines (0.016 sequence diverg
ence/Myr); (ii) the Yp1 gene in Hawaiian Drosophila (0.019/Myr Kambyse
llis et al. 1995); and (iii) parts of the mitochondrial 12S and 16S rR
NA and tRNA(val) in Laupala crickets (0.024-0.102/Myr, Shaw 1996). We
discuss the reliability of the estimates given the assumptions (i-vii)
above and contrast the results with previous calibrations of Adh in H
awaiian Drosophila and chloroplast DNA in lobeliods.