ecology of phasmids - KLUEDO - Universität Kaiserslautern
ecology of phasmids - KLUEDO - Universität Kaiserslautern
ecology of phasmids - KLUEDO - Universität Kaiserslautern
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Adult female feeding preference & nymph performance 67<br />
To account for taxonomically related biochemical leaf properties correlation analysis was repeated<br />
among Piper congeners under exclusion <strong>of</strong> the two species <strong>of</strong> the Araceae. Within Piper host plants<br />
performance <strong>of</strong> nymphs did not relate to phenol content, but exclusion <strong>of</strong> Araceae host plants led to<br />
marked increases in correlation coefficients (Product Moment Correlation, df = 8: survival to phenol<br />
content r = 0.58, relative growth rate to phenol content r = 0.61, both P > 0.05). In contrast to the<br />
expectation <strong>of</strong> a defensive function <strong>of</strong> phenolic compounds correlation coefficients demonstrated a<br />
positive trend in the relationship <strong>of</strong> performance and phenol contents.<br />
Particular biochemical properties <strong>of</strong> Araceae leaves could also have influenced performance <strong>of</strong> nymphs,<br />
thereby covering relationships between physical leaf traits and nymph performance considering Piper<br />
congeners. Exclusion <strong>of</strong> Araceae from correlation analysis did not reveal any significant relationship<br />
between any <strong>of</strong> these leaf traits and nymph performance (Product Moment Correlation, df = 8, relative<br />
growth rate to: leaf toughness r = -0.40, water content r = 0.30, specific leaf weight r = 0.31; survival to:<br />
leaf toughness r = -0.41, water content r = -0.03, specific leaf weight r = -0.04; all P > 0.05). The<br />
exclusion <strong>of</strong> Araceae host plants had no effect on the resulting correlation coefficients except for the<br />
relation <strong>of</strong> survival and leaf toughness that decreased from r = -0.03 (cf. Figure 4-11) to r = -0.41.<br />
Performance <strong>of</strong> nymphs seemed not to relate to female adult preference, indicating that prior feeding<br />
experience did not affect preference <strong>of</strong> females. In correlation analysis on MAI <strong>of</strong> females to survival<br />
and relative growth rates <strong>of</strong> nymphs no significant relation was detected (Product Moment Correlation,<br />
df = 9, MAI to: survival r = 0.50, relative growth rate r = 0.25, all P > 0.05). However, low mortality <strong>of</strong><br />
nymphs on Phil. inaequilaterum corresponded with significant preference <strong>of</strong> adult females (compare to<br />
Figure 4-6), but growth <strong>of</strong> nymphs was intermediate on this food source. Opposed to that, 69 % <strong>of</strong><br />
nymphs had died on P. reticulatum, a highly preferred food <strong>of</strong> adult females.<br />
4.4.4 Preference <strong>of</strong> M. diocles nymphs under varying total phenol and<br />
tannin contents<br />
The results <strong>of</strong> an infiltration experiment indicated that increased total phenolic contents as well as<br />
increased tannin levels in leaves might act against herbivory by phasmid nymphs. Both the increase <strong>of</strong><br />
total phenol contents with phenol extract and tannin solution resulted in significantly reduced feeding<br />
preference (i.e., water infiltrated control discs were preferred; Figure 4-12 & Figure 4-13). Yet, tannins<br />
may play a minor role in defense against M. diocles herbivory compared to other phenolic compounds.<br />
Increased contents <strong>of</strong> total phenols (by infiltration <strong>of</strong> phenol extract) pro<strong>of</strong>ed to be more effective than<br />
an increase <strong>of</strong> phenols by tannin solution alone. A rise <strong>of</strong> 0.5 % <strong>of</strong> total phenols by leaf phenol solution<br />
showed a significant effect in preference shift (Figure 4-12) whereas infiltration <strong>of</strong> 1.2% tannin was not<br />
different from the control (Figure 4-13). An increase <strong>of</strong> tannin concentrations up to 11.7 % above<br />
natural total phenol contents resulted in total rejection <strong>of</strong> tannin infiltrated leaf disks. Natural phenolic<br />
content in P. hispidum leaves from greenhouse plants was 2.86 ± 0.1 % TAE (similar to natural phenol<br />
content from field samples with 2.45 ± 0.6 % TAE).