ecology of phasmids - KLUEDO - Universität Kaiserslautern
ecology of phasmids - KLUEDO - Universität Kaiserslautern
ecology of phasmids - KLUEDO - Universität Kaiserslautern
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
Adult female feeding preference & nymph performance 55<br />
For reasons <strong>of</strong> sample size resulting from partially high nymph mortality (in D. longispatha and<br />
P. grande no nymphs had survived beyond week three) relative growth rates <strong>of</strong> nymphs were calculated<br />
after approximately 14 days. For the same reasons weight measures spread from day eight to day 17<br />
with 73 % <strong>of</strong> values referring to days 11 to 16. To account for temporal differences growth was<br />
calculated on a daily base as growth rate [mg*d -1 ]. Initial weight <strong>of</strong> nymphs was significantly different<br />
among groups (i.e., nymphs fed on different plant species) (ANOVA, F = 31.9, df = 12, P < 0.01).<br />
Calculation <strong>of</strong> relative growth rates (RGR) accounted for initial weight <strong>of</strong> nymphs and incorporated<br />
possible covariate effects:<br />
Equation 4-2<br />
final weight - initial weight 1<br />
RGR =<br />
×<br />
days<br />
initial weight<br />
The relative growth rate expresses the weight gain relative to the initial weight at the start <strong>of</strong> an<br />
experiment per unit time (relative weight gain per day).<br />
Plant species-specific relative growth rates <strong>of</strong> nymphs were then compared in Analysis <strong>of</strong> variance<br />
(ANOVA).<br />
The relationships between each leaf trait and survival and growth <strong>of</strong> nymphs were analyzed in<br />
parametric Product Moment Correlation Analysis. D. longispatha was not included in correlation<br />
analysis, because representative measurements <strong>of</strong> leaf traits could not be taken before the end <strong>of</strong> the<br />
study period.<br />
4.4 Results<br />
4.4.1 Interspecific differences in physical and chemical leaf properties<br />
All measured leaf characters showed significant interspecific differences indicating that host plant<br />
species <strong>of</strong> M. diocles varied in nutritional quality. Mean values are listed in Table 4-1 including the<br />
short names for plant species that are used in the Figures.<br />
M. diocles food plants showed expressed heterogeneity in leaf toughness (Figure 4-2). Relative leaf<br />
toughness varied significantly among host plant species with leaves <strong>of</strong> Philodendron sp. possessing a<br />
fivefold higher relative toughness (505.47 ± 41.68) than Piper marginatum (102.40 ± 14.82). Although<br />
P. marginatum had lowest leaf toughness there was no significant difference to P. arboreum and<br />
P. hispidum. All tested Piper species showed significantly lower relative toughness in leaf tissue than<br />
the tested Araceae <strong>of</strong> the genus Philodendron. However, variation in toughness among Piper congeners<br />
was considerably high: P. cordulatum and P. grande (296.37 ± 29.98 and 323.36 ± 31.38) had threefold<br />
tougher leaves than P. marginatum. The pattern <strong>of</strong> interspecific differences in relative leaf toughness<br />
seemed to be expressed stronger than patterns assessed from other leaf characters (see below). No more<br />
than three plant species had similar toughness values.