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 52<br />
4.2.4 Long term feeding trials with M. diocles nymphs<br />
To document growth and mortality <strong>of</strong> M. diocles nymphs I conducted long term feeding trials on single<br />
host plant species. At least 30 nymphs were raised on each <strong>of</strong> 13 food plant species. All performance<br />
trials lasted 6 weeks (performance sensu survival and growth).<br />
The selection <strong>of</strong> food plant species resulted from diet assessment from field records and no-choice<br />
feeding trials <strong>of</strong> M. diocles (see Chapter 2). Because Piper spp. were the main potential food sources in<br />
the field I tested 10 Piper species to evaluate interspecific differences in diet suitability <strong>of</strong> congeners. I<br />
included three species <strong>of</strong> Araceae: two Philodendron species were also recorded as potential food in the<br />
field whereas no M. diocles individual was found on Dieffenbacchia longispatha (but D. longispatha<br />
was accepted in no-choice feeding trials). Due to partial lack <strong>of</strong> nymphs and to restrictions in labor<br />
potential I could not include all Piper species tested in adult female preference tests.<br />
Newly hatched nymphs were weighed and then separately kept in plastic food containers (10cm wide,<br />
5cm deep, 5cm high). Adult leaves were harvested in the forest, placed in a sealed plastic zip log bag<br />
and brought back to the laboratory. Within 2 hours <strong>of</strong> being collected leaf discs (punch <strong>of</strong> 13 mm<br />
diameter) were cut and presented to nymphs. Leaf discs were stuck into a piece <strong>of</strong> cardboard to assure<br />
free access for the nymph. A piece <strong>of</strong> humid paper towel helped minimizing desiccation. If multiple<br />
nymphs hatched on the same day they were allocated to different food plant species. Nymphs then were<br />
provided with new food daily and controlled for survival. To document growth, nymphs were weighed<br />
in weekly periods.<br />
4.2.5 Dual-choice feeding trials with M. diocles nymphs<br />
This experiment was conducted at the Technical University <strong>of</strong> <strong>Kaiserslautern</strong>, Germany.<br />
P. hispidum plants were grown in greenhouses from cuttings I imported from Panamá. M. diocles<br />
nymphs had hatched from eggs I previously had collected from a lab population at Barro Colorado<br />
Island, Panamá.<br />
As defensive or deterring effects <strong>of</strong> phenolic or tannic compounds may be dose-dependent (Feeny 1970;<br />
Rhoades 1977; Coley 1986), I designed a test series <strong>of</strong> dual-choice feeding trials where nymphs were<br />
<strong>of</strong>fered leaf discs with artificially increased natural phenol and tannin contents by use <strong>of</strong> a method<br />
described by Beyschlag & Pfanz (1990) and modified by Herz (unpublished). Beyschlag & Pfanz<br />
(1990) used pressure infiltraton <strong>of</strong> water into a leaf via the stomatal pores to determine stomatal<br />
aperture. Herz (unpublished) used this method to infiltrate sugar solutions in leaves and <strong>of</strong>fered these to<br />
leaf cutting ants. I modified the method as I used leaf discs (15 mm punch) <strong>of</strong> Piper hispidum and<br />
infiltrated aqueous solutions <strong>of</strong> tannic acid and <strong>of</strong> total phenol extract from P. hispidum leaves.<br />
Phenolic compounds were extracted with 70 % aqueous aceton from P. hispidum leaves following the<br />
same procedure as described by Waterman & Mole (1994). Aceton and water <strong>of</strong> the phenolic solution<br />
evaporated within 48 hours under room temperature and the remaining phenolic aliquot was resolved in