260 A. Elizabeth Arnold
ratio of six species of fungi per vascular plant
species in Great Britain. However, by sampling
only endophytic and saprophytic fungi, Fröhlich
and Hyde (1999) suggested that a ratio of 1:33,
rather than 1:6, is more appropriate for tropi-
cal plants. This conclusion is supported by the
richness of endophyte communities in individual
tropical leaves. Gamboaet al.(2002) recovered
11.7±3.4 morphospecies of endophytes per leaf
in a survey of five tropical plant species. Lodge
et al.(1996) recovered 17 species from a leaf blade
ofManilkara bidentatain Puerto Rico, and Gilbert
et al.(2002a) recovered up to 13.1±3.4 mor-
phospecies per leaf in the mangroveRhizophorain
Panama. At BCI, Arnoldet al.(2003) isolated up to
13 morphospecies from 32 mm^2 of leaf tissue
fromTheobroma cacao(i.e., 16 leaf fragments, each
2mm^2 ), consistent with findings at the same site
forHeisteria concinnaandOuratea lucens(11–14
morphospecies per 48 mm^2 of leaf tissue; Arnold
et al.2000).
To date, no study has exhaustively sampled
the foliar endophyte community associated with
a single tropical plant or plant species. How-
ever, it appears that individual plants can har-
bor a tremendous richness of species. Arnold
et al.(2003) found 47.5±4.9 morphospecies
of endophytes associated with only nine leaves
from individualTheobroma cacaotrees in Panama
(i.e., 288 mm^2 of leaf tissue). Interestingly, total
richness per tree did not differ significantly among
individuals in agroecosystems, primary forest, or
secondary forest, although species turnover was
high among the endophyte species recovered in
each site. Although leaves on the same tree will
have a subset of endophytes in common, each leaf
will harbor distinctive endophyte communities,
leadin gto hi gh rates of species turnover amon g
leaves. In a study ofLaetia thamniain Panama,
leaf fragments of a consistent size were used to
sample increasin gleaf area on a sin gle individ-
ual. The number of morphospecies accumulated
as a function of cumulative leaf area with a coef-
ficient of 0.504, which is consistent with samples
amon gbiolo gical provinces at a landscape scale
(Figure 15.3; Rosenzweig 1995).
These and similar studies (e.g., Gamboa and
Bayman 2001, Cannon and Simmons 2002,
Suryanarayananet al.2002, Arnoldet al.2003)
are providin gbaseline data for understandin g
the diversity of tropical endophyte communities.
However, three major challenges still need to be0510No. of species1520024
Cumulative leaf area (cm^2 )68y = 6.535x0.504^ r^2 = 0.838Figure 15.3 Species–area relationship of
endophytic fungi in spatially nested samples
of leaves of a tropical treelet (Laetia thamnia)
at BCI. Richness was assessed as a function of
leaf area (determined as the number of
2mm^2 leaf segments sampled per leaf) for
leaves on one tropical tree. As samplin garea
increased, the number of species recovered
increased as a curvilinear function, with a
coefficient (0.504) consistent with the
species-area relationships for inter-provincial
samples at macroscopic scales (as per
Rosenzwei g1995).