Biology Reference
In-Depth Information
pollinator guilds, we then introduced syrphids, which started to pollinate im-
mediately. Mean visitation time was not significantly different between insects in
the cages and in nature. This was true both for bumble bees (mean visitation time
in cages: 3.25 ± 0.92 s, mean visitation time in nature: 2.91 ± 1.33 s, t = 1.51, df
= 96, p = 0.133) and for syrphids (mean visitation time in cages: 40.21 ± 8.89 s,
mean visitation time in nature: 35.38 ± 14.75 s, t = 0.77, df = 12, p = 0.45).
Measurement of Reproductive Success
One month after the first pollination treatments, we counted the total number of
fruits on each plant, except for M. guttatus and M. officinalis in which fruits can-
not be counted without collecting them. We randomly took five fruits per plant
of each species to estimate the number of seeds per fruit.
Measurement of Recruitment Richness and Density
Recruitment richness and density were estimated during the second (April 2004)
and third (April 2005) year of the experiment by counting the number of seed-
lings of each species in four 1,600-cm
2
quadrats in each plot.
Statistical Analysis
Statistical analyses were performed using SAS 8.2 software.
For the analysis of plant reproductive success, we log-transformed the data to
ensure normality. We standardized the data by species using the formula:
x -
µ
/
σ
(where
µ
= the mean and
σ
= the standard deviation of number of fruits or num-
ber of seeds per fruit for a given plant species) in order to make the data compara-
ble among the various species and functional groups. We used a mixed analysis of
variance (ANOVA) model (SAS proc mixed), in which the fixed effects were plant
treatment, pollination treatment, and their interaction term. To investigate the
effects of the various plant and pollination treatments, we subdivided a priori each
main effect into two components using orthogonal contrasts. The first contrast
tested the effect of the identity of the plant or pollinator functional group, i.e.
one group versus the other. The second tested the effect of the functional diversity
of the plant or pollination treatment, i.e. single-guild versus mixed-guild plant
or pollination treatments. Similarly, we subdivided the interaction into three or-
thogonal contrasts testing the effects of pollinator functional group identity on
each plant guild, and the effect of the functional diversity of both plant and pol-
lination treatments. See Table 1 for the construction of the contrasts.
