Chapter 14: Exploitative Interactions

exploitative

one organism increases its fitness at the expense of another organism

exploitative interactions

herbivory, parasitism, predation, pathogens

herbivory

caddisfly larvae graze on bacteria and algae, found that bacteria and algal developed higher populations when caddisfly larvae was no longer affecting them

predation

influence of birds/bats on tropical forest arthropods, when birds and bats are excluded, arthropods increased by 150% and 65%

pathogens

chytrid fungus decimates amphibian populations, can persist in environment without host, at least 501 amphibian spp. in decline, compromises osmoregulation and respiration

sunspot hypothesis

populations are driven by variation in solar intensity: disproven

overpopulation hypothesis

hares and their population density, regulate their population size

3 components:

disease and parasitism

physiological stress

starvation when density is low -> pop grows

predator hypothesis

numerical response: change in predator density due to change in prey density

functional response: change in predator feeding rate due to change in prey

snowshoe hare pop. cycles results from interactions between three trophic levels

the hares, food supply, predators

refuge

protection of exploited populations from predators and parasites

types of refuge

physical refuge, flight, spatial, numbers/grouping

physical refuge

large size

spatial refuge

burrows, trees, env.