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Moreover, beside the introgression of transgenes affecting the population dynamics of
receiving p lants, it a lso c ould imp act th e ta rget o r n on-target pr edator popul ations. F or
example, a negative correlation was found between moth densities of Helicoverpa armigera
and the planting years of Bt-cotton in both high and low Bt density areas, which indicates the
reduction of moth population density of H. armigera with the introduction of Bt cotton (Gao
et al. 2010). The variation of targeted insects will in turn affect the d ynamics of transgenic
and non -transgenic p lants b ecause i nsect p ressure af fects t he p lant r elative f itness an d
competitive capability (Ramachandran et al. 2000; Moon et al. 2007). T hus, the interaction
between transgenic and non-transgenic plants an d enemy-insects is also an important factor
that affects the consequences of introgressions from transgenic crops to wild relatives.
1.5.3 An applied example focusing on the insect- resistant and susceptible plants in plant
biology and ecology
Herbivory could lead to some phenotypic effects (e. g. chemical and morphological defense),
because pl ants r esponse t o he rbivory after da maging t hrough pr oducing c hemicals, l ike
glucosinolates ( Agrawal e t a l. 1999) , or c hanges i n s econdary c hemistry ( Baldwin 1994,
Karban a nd B aldwin 19 97), r esult i n t he va riation of m orphologic c haracteristics, s uch a s
trichome density and number (Baur et al. 1991; Agrawal 1999), leaf toughness (Kudo 1996),
flower attributes ( such as p etal le ngth and w idth) ( Cresswell et a l. 20 01). F or e xample,
damaged w ild r adish pr oduced 55% hi gher c oncentrations of g lucosinolates c ompared t o
controls w ith t he he rbivore, Pieris r apae (Agrawal e t a l. 2002) , a nd i ncreased de nsity and
total num ber of s etose t richomes on ne wly formed l eaves of pr eviously da maged pl ants
(Agrawal 1999). Cresswell et al. (2001) found that the petal length and width and long stamen
length was s horter in d efoliated B. napus than t hose i n controls. In a ddition, Lehtilä a nd
Strauss (1997) showed that leaf damage could reduce the attractiveness to pollinators because
of t he r eduction i n t he num ber a nd s ize of f lowers of w ild r adish dur ing t he f irst w eek
observation. Based on this, under herbivory, insect-susceptible wild plants might perform this
response, whereas insect-resistant transgenic plants would not be induced to response. Hence,
this might lead to a divergence in morphological traits of hybrids compared to their parents in
the presence of herbivory.
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