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 72<br />
only function against M. diocles in some Piper host species and even only in particular individuals (as<br />
represented by intraspecific absence <strong>of</strong> tannin in some leaves) if they had higher tannin contents as<br />
found here. Coley (1986) suggested that such intraspecific tannin variation could be governed<br />
genetically as she found between-plant differences in Cecropia tannin content persisted through time.<br />
Undoubtedly, tannin can deter herbivores: low tannin Cecropia plants suffered five times higher<br />
herbivory by caterpillars than plants with high tannin contents (Coley 1986). This difference in<br />
herbivory was based on substantial differences in tannin concentrations among <strong>of</strong> Cecropia individuals<br />
(13 to 58 mg*g -1 dw, Coley 1986). High tannin concentrations involve high costs as they have large<br />
initial construction costs and cannot be reclaimed upon leaf senescence (McKey 1979, Coley et al.<br />
1985, Coley 1988).<br />
Considering that tannins had to be accumulated in much higher concentrations compared to other<br />
phenolic compounds to deter M. diocles nymphs, evolution in Piper biochemistry may have favored<br />
qualitative defenses, particularly as many Piper species are gap adapted (Croat 1978). Coley et al.<br />
(1985) suggested that gap adapted plant species (pioneers, high light) should invest carbon in growth<br />
and less in carbon-based defense such as tannins. The rare presence <strong>of</strong> tannins in Pipers as demonstrated<br />
here and earlier (Baldwin & Schultz 1988) gives support to this view.<br />
However, as all phenolic compounds are based on carbon, the resource availability theory <strong>of</strong> Coley et<br />
al. (1985) also predicts low levels <strong>of</strong> total phenols in pioneer species. Baldwin & Schultz (1988) showed<br />
that independent from habitat Piper species shared low levels <strong>of</strong> total phenols while Miconia forest<br />
species (persistent, low light) had almost 17 times more phenols than Miconia gap species. In this study,<br />
the prediction <strong>of</strong> similarly low phenol contents among Piper species cannot be supported as total<br />
phenols varied significantly among species (independent from habitat as P. marginatum, P. culebranum;<br />
P. dilatatum, P. hispidum, P. peltatum and P. reticulatum represent pioneer species).<br />
Nevertheless, there is more support for a qualitative defensive pathway in Pipers. The genus Piper is<br />
enormously rich in secondary compounds (reviewed in Sengupta & Ray 1987; Parmar et al. 1997; Dyer<br />
et al. in press). So far in 112 out <strong>of</strong> more than 1000 species that have been investigated 661 different<br />
compounds have been found (Dyer et al. in press). Several studies have presented effects <strong>of</strong> all classes<br />
<strong>of</strong> Piper compounds against herbivores with Amides being particular strong (Bernard et al. 1995;<br />
Parmar et al. 1997 and references therein; Siddiqui et al. 2000; Dyer et al. 2003). For example, Dyer et<br />
al. (2003) showed that three Amides <strong>of</strong> Piper cenocladum all negatively influenced larval performance<br />
<strong>of</strong> lepidopterans with stronger synergistic effects <strong>of</strong> a mixture <strong>of</strong> the Amides. Given the large variety in<br />
secondary compounds in Piper, the presented preference-performance pattern <strong>of</strong> M. diocles may have<br />
resulted from interspecific qualitative differences in phenolic composition, with plant species that were<br />
disliked by adults or where nymphs suffered reduced performance containing particularly toxic<br />
compounds. This suggestion is supported by the fact that secondary compounds in Piper differ<br />
qualitatively among species (Parmar et al. 1997). Many species contain exclusive compounds and have<br />
evolved high varieties in particular compound classes (Dyer et al. 2003). To exemplify, from Piper