Figure 2. Vital and population
growth rate relationships with PC1 for each focal species. Low values of
PC1 represent closed canopy, high litter, high soil fertility plots. PC1
is standardised to a mean of 0 and standard deviation of 1. Black lines
and light grey fields represent linear regressions from models with 95%
confidence intervals holding continuous explanatory variables at their
means, under the ambient watering treatment. Points for emergence and
survival represent emergence fractions and survival of individuals. To
facilitate plotting, we have added one to seed production values and
show them on a log scale. Significant interactions between PC1 and
neighbour abundance or presence (for population growth) are plotted with
points and regressions representing the presence (red) or absence (blue)
of neighbours, holding abundance at their respective means for survival
and seed production. Asterisks indicate significance of the main effect
of PC1 where models did not include interactions of other factors with
PC1: * p < 0.05.
Soil pH and the watering treatment had few main effects on species’
vital and population growth rates. Soil pH (PC2) had a negative or
convex relationship with emergence for 3/9 species, was positively
related to survival for 1/8 species, negatively related to seed
production for 1/8 species, and positively related to population growth
rate for 1/8 species (Table S2, p <0.05). Interestingly,
survival responses to PC1 depended on the watering treatment for half of
the species but without a clear pattern in directions of responses among
species (Table S2 and Figure S4). This interaction was more prevalent
for survival than seed production (1/8 species) or population growth
rate (2/8 species, Table S2 and Figure S4). There was consistently no
evidence that the watering treatment influenced species’ responses to
neighbour abundance or presence, except for T. cyanopetala which
had lower population growth rate in the dry compared to ambient watering
treatment but only where neighbours were present, not absent (Table S2).
Survival, seed production, and population growth rate responses to
biotic factors were similar among species. We found no clear main
effects of neighbour abundance on survival or seed production for any
species, except for P. debilis where seed production decreased as
the number of neighbours increased (Fig. 3, Table S2). Mean population
growth rates were lower in the presence than absence of neighbours for
all species, although the main effect of neighbours on population growth
rate (where there were no interactions with other factors) was only
significant for 2/8 species, including P. debilis (Fig. 3, Table
S2, p <0.05). The presence of the invasive parasiticC. campestris, did not affect survival, and only influenced seed
production, negatively, for 1/8 species (Table S2).