Vol 25, no 3, October - The Linnean Society of London

38
THE LINNEAN 2009 VOLUME 25(3)
In order to set Darwin’s lichens in their correct historical and geographical
perspective, a few basic questions should be considered. (1): What was known of
lichens worldwide and who were the leading lichenologists in the early 1830s when
Darwin was contemplating his forthcoming long voyage on the Beagle from 1832-
1836? (Barlow 1945; Keynes 1988, 2002; Browne 1995); (2): What was known of the
lichens of South America at the time of Darwin’s visit? (3): How much might Darwin
have known about lichens at the time of the voyage?
(1) As a student at Cambridge (1828-1831), Darwin was greatly influenced by the
Professor of Botany, John Stevens Henslow, who was both his mentor and friend
(Barlow 1967; Browne 1995; Walters & Stow 2001). Lichenology in Britain was then
at a low ebb (Hawksworth & Seaward 1977; Laundon & Waterfield 2007). Three
decades earlier, the Swedish lichenologist, Erik Acharius (1757-1819), Linnaeus’s
last student (Kärnefelt & Frödén 2007), had set systematic lichenology on a bright
new path when he segregated Linnaeus’s collective genus Lichen into smaller
independent genera, consolidating his new arrangement in three important foundational
books, the Methodus (Acharius 1803), Lichenographia Universalis (Acharius 1810)
and the Synopsis methodica lichenum (Acharius 1810). His ideas were quickly taken
up in Britain by Dawson Turner and William Borrer, and then W.J. Hooker (Hooker
1829-1866; Turner & Borrer 1839; Hawksworth & Seaward 1977; Galloway 1981a,
1988; Seaward 2002; Laundon & Waterfield 2007), but much less enthusiastically by
James Edward Smith, who, while admiring Acharius’s knowledge and industry, would
not subscribe to the new segregate genera. On receiving a copy of Acharius’s Methodus
he wrote to Acharius in 1804 explaining his conservative position “… do not blame
me if my opinion on speculative points differs sometimes from yours. Neither dare I
change names so freely as you have done. I must keep in view those Laws of Linnaeus
which are sanctioned by experience and founded in justice…It is easy enough to use
new words. Genius appears best in using old ones properly…I regret that there should
be a word in your excellent book that I cannot zealously defend as a friend ought: but
I know we cannot all think alike in philosophy any more than in religion…” (Galloway
1988: 165).
Acharius’s world view of lichens in 1814 amounted to 906 species in 43 genera
(Acharius 1814; Kärnefelt & Frödén 2007) and by the early 1830s, the number of
species was slowly starting to grow, when the impetus for lichen taxonomy passed
from Sweden to France and Germany, with the work of such lichenologists as Fée
(1824-1837), Eschweiler (1824), Wallroth (1824) and Delise (1825a, 1825b) creating
new names and opening up new vistas. But lichenology remained poised, waiting for
a catalyst to open the still-closed book of Southern Hemisphere lichenology. As we
shall see, Darwin was to be very much part of that necessary catalyst.
(2) When the Beagle sailed from Plymouth on 27 December 1831 bound initially
for southern South America via the Cape Verde Islands and Brazil, what in fact was
known of the lichens of South America? Not a lot. From Commerson’s collections
made from the Straits of Magellan in 1767, Jacquin (1781) described Lichen aurantiacoater
[= Usnea aurantiaco-atra (Walker 1985: 62)] and L. antarcticum [= Nephroma
antarcticum (White & James 1988)]. Cook’s three voyages yielded several collections
from Banks & Solander, the Forsters & Sparrman and Anderson, but only one species