SLIDE 4 Lots of evidence for JC
Seedling survival is reduced... ! Near conspecific adults ! In crowds of conspecific seedlings ! ...Often because of host-specific insects or pathogens
80
* .
:. .
60
..
.
.
. . .
+
* * ....
c
. .
. . . .
5
20
Tree I
. .
h
. ..
m
c
201 :
.
* :
Tree 3 Distance south of parent tree (m)
FIG.
- 3. Percentage of seedlings of Platypodium elegans on Barro Colorado Island, Panama,
dying from damping-off during the first 3 months as a function of distance along transects south
- f four parent trees. The lines show the percentage damping-off predicted by the regression if
seedling density and light environment at each distance were at the average value for the transect. Points are the observed levels of damping-off, corrected for variation due to seedling density and light environment, i.e.
"~(corr)
= yi(obs)
+ bz('denslty
+ b3('Â¥Lsa -x~(sa.p))>
where 6, and b3 are the partial regression coefficients for X , + X , respectively, from the multiple regression presented in Table 2).
Tree I
I
Tree 2 Distance south of parent t r e e ( rn
FIG.
- 4. Percentage of seedlings of Platypodium elegans on Barro Colorado Island, Panama,
dying from damping-off during the first 3 months at selected distances from Trees 1 and 2. An equal number of seedlings were observed at each distance interval. Shaded bars represent gaps. The initial mean density of seedlings (m-l) occurs above each bar.
Seedling escape from fungalpathogens
28r
Tree I
LTree
3l
A 0
1
4 Tree 4 7
Distance south of parent tree (m)
FIG.
- 1. Seedling density in relation to distance south of four parent trees of Pla[vpodium elegans
- n Barro Colorado Island, Panama.
TABLE
- 1. Differences among the four trees of Platjyodium elegans on Barro
Colorado Island, Panama, in distance and density of seedlings south of the parent, and incidence of death of seedlings by damping-off during first 3 months after germination.
Tree 1 2
3
4 Number of seedlings observed 1884 926 298 115 Median distance of seedlings 22 I3 16 12 from parent (m) Seedling density at median 25.0 12.0 2.7 1.5 distance (m ') Seedlings dying (%I) 85.2 80.0 83.9 46.1 Seedlings dying due to 81.2 63.0 54.0 34.8 damping-off (96) Proportion of seedling deaths due 95.2 78.7 64.4 75.5 to damping-off ('XI)
first 3 months was higher within 20 m of the pankt than at any greater distance (Fig. 2). For seedlings of Trees 1 and 2, mortality was higher at intermediate than at far distances (Fig. 2). For Tree 1, seedling mortality was lowest in the large gap at 35-55 m; for Tree 2, mortality at far distances was slightly lower than in the small gap at 5-10 m (Fig. 2). The four trees differed in the proportion of seedlings surviving the first 3 months (Table 1); mortality increased with seedling density.
Mortalify factop
Causes of seedling mortality were determined only in the first 3 months when damping-off was the predominant cause. It accounted for 64% (Tree 3) to 95% (Tree 1) of seedling deaths (Table 1). The remaining mortality was unevenly divided among six other factors: (i) the fall of branches and leaves onto the seedling; (ii) poor root establishment;
Augspurger, 1983, J. Ecology
