ecology of phasmids - KLUEDO - Universität Kaiserslautern
ecology of phasmids - KLUEDO - Universität Kaiserslautern
ecology of phasmids - KLUEDO - Universität Kaiserslautern
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Community structure & host range 12<br />
see Figure 1-2). Transects were monitored at night every two weeks. The vegetation was scanned with<br />
headlamps up to 2 m heights and in a one-sided width <strong>of</strong> about 2 m from the line center (to both sides in<br />
the understory and to one side at the forest edge). Phasmids were classified to morphotypes, and<br />
released again after body length was measured.<br />
2.2.2 No-choice feeding trials<br />
To estimate breadth and overlap <strong>of</strong> the realized niches <strong>of</strong> phasmid species I recorded all plants on which<br />
<strong>phasmids</strong> were found along line-transects. As observations <strong>of</strong> feeding in the field were rare, all plant<br />
records were treated as potential host plants. These plant species were then tested in subsequent nochoice<br />
feeding trials.<br />
To determine diet breadth (sensu absolute food niche) phasmid adults and nymphs were presented with<br />
leaves from alternative plant species in a no-choice design. Adult leaves were harvested in the forest,<br />
placed in a sealed plastic zip log bag and brought back to the laboratory. Within 2 hours <strong>of</strong> being<br />
collected leaves or leaf discs were presented to <strong>phasmids</strong>. Feeding trials were conducted in a screened<br />
room subject to ambient conditions. According to the size <strong>of</strong> the animals, plastic containers <strong>of</strong> different<br />
sizes were used as trial arenas. The lid <strong>of</strong> such arenas was screened to allow for ambient conditions.<br />
Each plant species was tested with a minimum <strong>of</strong> three M. diocles individuals. Adult <strong>phasmids</strong> and large<br />
nymphs (instars five and six) were presented with whole leaves. Leaves were <strong>of</strong>fered with water supply<br />
by sticking the petiole in a water-filled vial and fastening it with Cotton. Small nymphs (instars one to<br />
four) were <strong>of</strong>fered leaf discs (punch <strong>of</strong> 13 mm diameter) that were stuck into a piece <strong>of</strong> cardboard to<br />
assure free access for the nymph. A piece <strong>of</strong> humid paper towel helped minimizing desiccation. Feeding<br />
trials began in the late afternoon and lasted 24 hours. In cases where the leaf received only a few bites or<br />
was not eaten at all, it was considered inedible (see for comparison Barone 1998). As soon as one<br />
phasmid individual obviously had fed on a leaf, the according plant species was recorded as edible. In<br />
general, <strong>phasmids</strong> fed on leaves in a measurable way. If a leaf was left untouched while a nymph had<br />
moulted, the trial was discarded.<br />
Four different groups <strong>of</strong> plants were <strong>of</strong>fered to the four phasmid species maintained in the laboratory:<br />
(1) potential host plants, i.e. plant species where <strong>phasmids</strong> were found on in the field; (2) congeners and<br />
confamilials <strong>of</strong> the plant species that were proven edible; (3) a selection <strong>of</strong> 10 <strong>of</strong> the most abundant tree<br />
species on BCI (>1000 ind.*50 ha -1 ; Condit et al. 1998); (4) a random selection <strong>of</strong> plant species from<br />
forest understory and forest edge. For the latter, I asked field botanists on BCI to bring leaves <strong>of</strong> a<br />
random plant species back to the lab.<br />
2.2.3 Data analysis<br />
2.2.3.1 Estimating phasmid community parameters<br />
A list <strong>of</strong> phasmid species on BCI was achieved by means <strong>of</strong> all available field records (i.e. line-transect<br />
and collection records). Field records besides line-transect data have not been used for analysis <strong>of</strong>