ecology of phasmids - KLUEDO - Universität Kaiserslautern
ecology of phasmids - KLUEDO - Universität Kaiserslautern
ecology of phasmids - KLUEDO - Universität Kaiserslautern
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
Community structure & host range 16<br />
c = Number <strong>of</strong> plant families only accepted in feeding-trials but not recorded in line-transects<br />
Sørensen’s similarity coefficient is a qualitative measure usually used for matches in species<br />
composition between samples. As feeding-trials result in qualitative data (edible vs. inedible) this<br />
coefficient is also applicable to measure qualitative overlap between realized and absolute food niche.<br />
Sørensen’s similarity coefficient weighs matches more heavily than mismatches and thereby accounts<br />
for the fact that mismatches were over represented both 1) in line-transect data, as all recorded plant<br />
species were considered as potential host plants and 2) in feeding trials, as not all tested plant species<br />
that were edible occurred in line-transects.<br />
2.3 Results<br />
2.3.1 Phasmid diversity and density<br />
In 15 months <strong>of</strong> line-transect monitoring I recorded 307 specimens representing 11 phasmid species<br />
(Table 2-1). The species accumulation curve from line-transect records reached an asymptote after four<br />
months (Figure 2-1) suggesting that the phasmid fauna <strong>of</strong> forest edge and understory habitats was<br />
sampled adequately. This was supported by the fact that in field records other than along line-transects<br />
only one additional phasmid species was found (Pseudophasma menius; Table 2-1). One species<br />
(Otocrania sp.) has not been previously reported for Panamá (compare to Appendix 1).<br />
The local phasmid fauna was dominated by four common species comprising more than 89 % <strong>of</strong> the<br />
sampled specimens (Figure 2-2). Seven phasmid species were found in low numbers <strong>of</strong> 10 or less<br />
individuals. One <strong>of</strong> these species was represented by a singleton (Stratocles multilineatus).<br />
Line-transect data uncovered a clear spatial separation in the community structure. Diversity in phasmid<br />
species was higher in forest edges compared to the forest understory (Table 2-1). This higher diversity<br />
resulted from higher species richness and higher eveness along forest edges. The data indicate that<br />
<strong>phasmids</strong> were mainly restricted to forest edge habitats; ten out <strong>of</strong> eleven species and 93 % <strong>of</strong> the<br />
recorded individuals occurred here. In the forest understory <strong>phasmids</strong> were rare and singletons<br />
represented three out <strong>of</strong> four species. Only Metriophasma diocles was found regularly and comprised<br />
86 % <strong>of</strong> the recorded specimens in the understory. As this habitat was poor in species and in individuals,<br />
similarity <strong>of</strong> phasmid communities between forest understory and forest edge was low (demonstrated by<br />
Morisita’s similarity index Cλ = 0.25; Table 2-1). Phasmid density was 35 times higher in forest edge<br />
habitats than in the understory (Table 2-1). Analogous population density for M. diocles was lower in<br />
the understory than at forest edges. While absolute abundances doubled population density trebled from<br />
6.7 ind.*ha -1 in the understory to 21.6 ind.*ha -1 at forest edges after adjusting for size <strong>of</strong> the sampled<br />
area (with a respective total area searched <strong>of</strong> 0.096 and 0.048 ha).