Tropical Forest Community Ecology

110 Jess K. Zimmermanetal.

of individuals 1–4 cm dbh for 108 tree and shrub
species, with respect to low (i.e., gaps) versus high
canopy areas, and concluded that few species
were either ga por understory s pecialists – most
species (∼80%) did equally well in ga pand non-
ga pareas. Similarly, Hubbellet al. (1999) found
that tree and shrub species diversity of gaps ver-
sus non-gaps was not different in the BCI FDP
but they failed to account for differences in tree
stem density that was higher in gaps and exam-
ined only tree species diversity (Chazdonet al.
1999, Tilman 1999). After accounting for den-
sity via rarefaction of both pioneer trees and
lianas, Schnitzer and Carson (2001) did find that
gaps in the BCI FDP had higher species richness.
Pioneer and liana species (with lianas predomi-
nating) account for more than 30% of all woody
species on BCI. For trees and shrubs, Wright
et al. (2003) have taken something of a mid-
dle ground showing that, on the BCI plot, there
is a continuum of response, and emphasizing
that there are species that are either extremely

shade tolerant or light demanding (Agyemanet al.

1999).

Ga ps pecialization has often been thought of

as representing a fundamental life-history axis,

where there are trade-offs in life-history charac-

teristics and demographic patterns among species.

Large FDPs allow us to ask (Swaine and Whitmore

1988, Alvarez-Buylla et al. 1992, Agyeman

et al. 1999, Kyerehet al. 1999): (1) are there

trade-offs in life-history characteristics related

to growth and mortality patterns, and (2) are

life histories discontinuous (e.g., “pioneer” ver-

sus “non-pioneer” [otherwise known as “shade-

intolerant” versus “shade-tolerant” or “mature”]

species forming bimodal groups) or are they

continuous (i.e., unimodal or having uniform

variation over each life-history characteristic)?

Hubbell and Foster (1992) demonstrated a neg-

ative relationshi pbetween mortality of s pecies

in the shade and their rate of growth in gaps

(Hubbell and Foster 1992; Figure 7.4a), sug-

gesting a life-history trade-off, but the pattern

100

(a) (b)

95

90

85

80

75

70

60

50

40

30

20

10

0

0102030

Adult susceptibility to hurricanes (%)

SAPLAU ZANMAR

CROPOE

CORSULDRYGLA

MATDOM

INGVER CALBRA

BYRSPI

HOMRAC TRIPALLAEPRO

COCDIVGUTCAR

TETBAL

ANDINE

GUEVALSYZJAMOCOLEU

EUGSTA DENARB

ROYBORCASSYL

OCOSIN

CYRRAC

ALCFO

MYRSPL

CHIDOMMICTET

ORMKRU

0 102030 40 50 60

Median annual growth in gaps (%)

Annual survival in understory shade (%)

Sapling mortality (%)

40 50

Figure 7.4 Evidence from FDPs for trade-offs in demographic characteristics among tropical forest trees and the
presence of distinct species groups (e.g., “pioneers”). (a) The BCI FDP, showing variation among species in
mortality in the shade and growth in gaps (Hubbell and Foster 1992). (b) The Luquillo FDP (Uriarteet al. 2004a),
where hurricane susceptibility was measured as the proportion of stems greater than 10 cm dbh damaged in
Hurricane Hugo in 1989 (see Uriarteet al. 2004a for species names) and compared with post-hurricane mortality.
The groupings shown are arbitrary and were chosen to include rare species in the analyses of neighborhood
competition.