Darwin's Rhea (Rhea darwinii); Darwin's
Finches (Geospiza)
The
ornithologist John Gould identified Darwin's southerly South
American "ostrich" as a new species of rhea, and named it
after its discoverer. Its range is adjacent to that of the more
northerly common rhea. In March 1837, Darwin wrote in his
notebook: "The same relation that common ostrich
bears to Petisse, extinct guanaco to recent: in former case
position, in latter time."
That is, geographical relationships mirror analogous
relationships in time: there is evidence of transmutation
of species. Darwin's biographer Janet Browne (1995)
says "This
moment more than any other in Darwin's life deserves to be
called a turning point."
Darwin's
Finches (Geospiza) are similar to those on the South
American mainland, but show extensive variation in the forms of
their beaks even between adjacent islands. These specimens were
collected by Darwin himself and are kept in the British Museum.
Note the two specimens tagged in red:
this is a taxonomic convention to indicate type specimens
from which new species were first described.
