(French West Indies)boj_1 - CNCFlora

218 M. J. M. CHRISTENHUSZ
Number of species
80
70
60
50
40
30
20
10
0
Fern diversity per altitude in Guadeloupe
0–200 200–400 400–600 600–800
Altitudinal range (m)
ferns that can be found there. He divided Guadeloupe
into six bioclimatic zones (Figs 4, 5): swamps, xerophile
forests, mesophile forests, rainforests, montane
forests and montane savannas.
Mangrove swamps are found along the coast, especially
between the islands of Basse Terre and Grand
Terre and along the west coast of Grand Terre. Freshwater
swamps are often found near lakes inland.
Generally, mangrove swamps are not rich in ferns,
but those around Les Abymes house a variety of
species. Most common are Acrostichum aureum L.
and A. danaefolium Langsd. & Fisch., which tolerate
inundation by saltwater. Inland ferns such as Thelypteris
hydrophila (Fée) Proctor can be commonly found
in freshwater swamps at mid elevations. Dacryodes
Vahl (Burseraceae) dominated swamp forests (found
around Étang Madère and Étang Zombis, Fig. 5A) are
often rich in epiphytic ferns.
Xerophile forest (dry forest, Fig. 5B) is characterized
by trees that have developed adaptations to
periods of drought. It mostly consists of scrub with
spiny branches and succulent leaves, such as Euphorbia
articulata Aubl., Guaiacum officinale L., Capparis
flexuosa (L.) L. and Pithecellobium unguis-cati (L.)
Benth. Locally, cacti and agaves (especially Furcraea
foetida (L.) Haw.) are abundant. This area is not
naturally rich in ferns, but comprises a large part of
the general biodiversity of the Caribbean. The rapid
800–1000 1000–1200 1200–1400
Number of
species
Figure 3. Graph of species diversity per elevational range, based on collections and observations by the author in 2003
and 2005.
expansion of human inhabitation and the accompanying
infrastructure places this type of vegetation
under great threat. In sheltered places, such as
shaded ravines, one can find fern species such as
Adiantopsis radiata (L.) Fée, Adiantum tenerum Sw.,
Doryopteris pedata (L.) Fée, Hemionitis palmata L.,
Pteris vittata L. and Tectaria heracleifolia (Willd.)
Underw.
Mesophile forest is semi-deciduous (Fig. 5C) and
can often be found on karst limestone where rainwater
drains away quickly. On the steep ravines and
sink holes one can find a variety of ferns that often
show adaptations to drought. Typical species of mesophile
forests are Adiantum fragile Sw., Asplenium
dentatum L. subsp. barbadense (Jenm.) Christenh.,
Cyclopeltis semicordata (Sw.) J.Sm. and Cyclosorus
guadalupensis (Wikstr.) Ching. This vegetation type
is rare on Guadeloupe and is found in the southwestern
part of Basse Terre, especially in the Monts
Caraïbes, on Les Saintes and in the Grands-Fonds on
Grand Terre.
Hygrophile forests or rainforests can be classified
into lowland and mid-elevation rainforests. In Guadeloupe,
the lowland rainforests are sparse and fragmented
because of agricultural activities on its rich
volcanic soils. Lowland rainforest is best preserved in
the vicinity of waterfalls and gorges, along creeks and
on hilltops. In many places the forest is dominated by
© 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 161, 213–277