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The role of ecological gradients and host-parasitoid interaction in tropical insect communities
FINNIE, Sam Cameron
The thesis explores the various biotic and abiotic factors that drive change in insect communities with particular emphasis on host-parasitoid interactions. These factors range from ecological gradients to defensive traits and host specialisation. The aim of the first chapter was to determine how the assemblage of an ecologically and anthropocentrically significant group of insects changed in response to altitude. This study highlighted the elevational limit of fruit flies and discovered that a new and promising attractant lure used in agriculture was particularly useful at higher altitudes, potentially opening new avenues for pest management in mountainous regions. The aim of the second chapter was to ascertain the physiological and phylogenetic traits of galling insects that alter the diversity and host specificity of their parasitioids. This research not only uncovered a remarkably specialist community of gall parasitoids, and found significant physiological drivers of parasitoid assemblage, it also broached the possibility of a latitudinal gradient in gall parasitoid host specificity, that warrants further exploration due to its potential implications for biodiversity patterns. The final chapter, aimed to uncover patterns in the vertical stratification of a caterpillar-parasitoid community, and whether any potential patterns and interactions are driven by the defensive traits of the caterpillar hosts. This study provided further evidence that the defensive traits of caterpillars influence their vulnerability to parasitism, and discovered distinct patterns in the vertical stratification of caterpillar communities. Overall, this holistic research expands upon the existing literature on tropical insect ecology and advances our understanding on the complex interactions between insects and their environment.
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Struktura společenstev hálky tvořících členovců na vrbách
KADLEC, Jan
V této bakalářské práci jsem zkoumal vliv ekologických faktorů na diverzitu a abundanci hálek na vrbách. Zaměřil jsem se na vliv fylogeneze hostitelských rostlin, ochranné vlastnosti hostitelských rostlin a vlivem interakcí mezi guildami herbivorních členovců. Zjistil jsem, že abundance hálek je ovlivněna hlavně obsahem živin v hostitelské rostlině, zatímco některé z ochranných mechanizmů hostitelské rostliny mělo jen marginálně signifikantní vliv. Vliv fylogeneze hostitelských rostlin se zřejmě liší mezi jednotlivými taxony hálky tvořících členovců a několik druhů hálky tvořících členovců na vrbách bylo polyfágních a prokázalo jen omezenou reakci na fylogenezi vrb. V souhrnu je reakce hálky tvořících členovců na charakteristické vlastnosti vrb velice odlišná oproti reakci méně cpecializovaných guild herbivorních členovců
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Specificity of insect-plant associations and their role in the formation of plant defenses and speciation
VOLF, Martin
The aim of this dissertation is to investigate what role insect-plant interactions play in the formation of host-plant defenses and in the diversification of both groups. We show that various groups of herbivore respond differently to host-plant defenses. Therefore plant defenses diversify into suites of complementary traits, as individual traits fail to provide protection against specialized herbivores. Further, we identify what levels of host-phylogeny shape the food-web structure of insect herbivores. We show that specialized herbivores are affected mainly by the terminal parts of the host-phylogeny. In contrast, more polyphagous guilds are affected mainly by the mid-levels of the host phylogeny because the effects of terminal or deeper phylogeny seem to be surpassed by other factors in more generalist insect species. In the last chapter, we show how specialized insect-plant interactions generated by tight insect-plant coevolution can influence the speciation in plants over environmental gradients.
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Insect herbivores drive the loss of unique chemical defense in willows
VOLF, Martin
The thesis examines the effects of chemical and mechanical defensive traits on insects in a local community of 11 Salicaceae species growing in sympatry. The results repeated loss of willow specialized chemical defense. This could be due to its low protective value and high energy costs. Our study thus shows that the balance between costs and benefits of defensive traits is not necessarily in favor of specialized defenses and illustrates a process, which may lead to the reduction in a defensive trait.
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