Geography Reference
In-Depth Information
References
Carracedo, J. C. and S. Day. 2002.
Canary Islands
. Harpenden, Hertfordshire: Terra.
Clement, M., D. Posada, and K. A. Crandall. 2000. TCS: A computer program to es-
timate gene genealogies.
Molecular Ecology
9:1557-1659.
Emerson, B. C., S. Forgie, S. Goodacre, and P. Oromí. 2006. Testing phylogeographic
predictions on an active volcanic island:
Brachyderes rugatus
(Coleoptera:
Curculionidae) on La Palma (Canary Islands).
Molecular Ecology
15:449-458.
Posada, D., K. A. Crandall, and A. R. Templeton. 2000. GeoDis: A program for the
cladistic nested analysis of the geographical distribution of genetic haplotypes.
Molecular Ecology
9:487-488.
Cladograms based on molecular data may be used as raw data in cladistic
biogeography and intraspecific phylogeography. In addition, the assumption
that the rate of molecular evolution is approximately constant over time
for proteins in all lineages allows one to infer a clock-like accumulation of
molecular changes (Bromham and Woolfit 2004; Zuckerland and Pauling
1962). The “ticks” of the molecular clock, which correspond to mutations, do
not occur at regular intervals but rather at random points in time (Gillespie
1991). This time is measured in arbitrary units and then calibrated in millions
of years by reference to the fossil record or geological data (Benton and
Donoghue 2007; Magallón 2004; Sanderson 1998), giving minimum estim-
ates of the age of a clade, which in turn may help elucidate the relative min-
imum ages of the cenocron to which it belongs. Additionally, knowledge of
relative minimum ages of divergence may indicate whether a specific dis-
persal or vicariance event hypothesis better explains the patterns observed.
If clock calibrations provide estimates smaller than those proposed by vicari-
ance events, dispersal may be a better explanation.
The calibration of a molecular clock requires that we find two extant spe-
cies for which the date of speciation can be determined from the fossil re-
cord, to establish the time since the speciation event. Then we compare the
DNA sequences of the same gene of both species and count the number
of nucleotide substitutions. If all the substitutions are assumed to have aris-
en after the speciation event, the rate of DNA evolution for the gene under
study is obtained by dividing the number of DNA differences between both
species by the time since speciation. Assuming a constant mutation rate,
