Herbivores and Host-Plant Interactions

1. Herbivores and Host-Plant Interactions

2. Herbivory • Herbivory is a form of predation in which an organism consumes principally autotrophs such as plants. • Herbivory is restricted to animals eating plants. • Organisms that feed on autotrophs are Primary consumers.

3. Herbivores • Most of the animal species are herbivores. • The diet of any one animal will change. throughout its life as what is available for it to eat and its own nutritional requirements. • Most species feed on a variety of other species. ( exceptions in special animals like Koalas and giant Panda). • Most herbivores feed on leaves, shoots, seeds and fruits ( some also eat flowers). • Cellulose is largely indigestible to vertebrates. • Internal Flora Giant Panda feeds exclusively on bamboo Koala feed on only a few species of eucalyptus

4. Plant defense against Herbivory • Trait that increases plant fitness when faced with herbivory. • Two categories : Tolerance and Resistance. • Resistance :Constitutive or induced defenses. • Physical defenses (e.g. Thorns on roses, spines on a cactus). • Chemical defenses are secondary metabolites – Carbon-based defenses and Nitrogen-based defenses. • Some plants can attract natural enemies to herbivores – indirect defense ( e.g. ants reduce herbivory). Roses with Thorns – Physical defenses Poison Ivy – Chemical defenses

5. Herbivore offense • Herbivores need to overcome these defenses and obtain food. • Insect herbivores have evolved a wide range of tools to facilitate feeding (e.g. incisors – soft leaves , mandibles – mature leaves and grass). • Mammals have developed teeth structures. • A herbivores diet shapes its feeding adaptations. • Three primary strategies : Choice, Herbivore modification and plant modification. • Herbivores can use the plant chemical defenses for their own benefit. Monarch butterflies Caterpillar

6. Co evolution • Adaptation Dance: Plant defense and herbivore offense. • ‘’Coevolutionary Arms Race’’. • Adaptation in herbivores and their host plants has been the driving force behind speciation. • In cases where this relationship demonstrates “specificity” (the evolution of each trait is due to the other), and “reciprocity” (both traits must evolve), the species are thought to have coevolved. • Most of the interactions is negative but some is actually beneficial – mutualisms. • Historically, insects have been the most significant herbivores, and the evolution of land plants is closely associated with the evolution of insects. • Direct impact of these interactions on agriculture, including human and livestock food sources, as well as in the search for plants of medical importance.

7. Appendices • Figure 1 (http://upload.wikimedia.org/wikipedia/commons/thumb/9/9c/Deer.jpg/250px-Deer.jpg) • Figure 2 (http://bogglesworldesl.com/flashcardsESL/herbivores.jpg HERBIVORES 4) • Figure 3 (http://www.biojobblog.com/giant-panda-china-big(1).jpg) • Figure 4 (http://www.harunyahya.com/articles/images_articles/koala2.jpg) • Figure 5 (http://www.mooseyscountrygarden.com/rose-picture-gallery/rose-thorn.jpg) • Figure 6 (http://upload.wikimedia.org/wikipedia/commons/7/71/Toxicodendron_radicans.jpg) • Figure 7 (http://en.wikipedia.org/wiki/Image:Monarch_Butterfly_Danaus_plexippus_on_Echinacea_purpurea_2800px.jpg) • Figure 8 (http://bugguide.net/images/cache/PHYH9HFHGH9ZQL8ZRLPZIHDHZL8ZQLVZ5LUZ4LWZUHCHMHTHMHEZ4HVH8HAHIHOH4HGZ7HEZ8LHR7LBZGLFH.jpg)