Community Ecology I PDF

Community Ecology I New tiny (and loud) frog discovered! Paedophryne amauensis, from Papua New Guinea Need to know: be able to define community ecology, and understand what an ecological community is. be able to describe and identify different types of species interactions be able to...

Community Ecology I New tiny (and loud) frog discovered! Paedophryne amauensis, from Papua New Guinea Need to know: be able to define community ecology, and understand what an ecological community is. be able to describe and identify different types of species interactions be able to define competition and competitive exclusion be able to describe the niche concept, and understand the difference between fundamental and realized niches. be able to describe several mechanisms by which species are able to coexist. Understand the concept of species diversity, and how it differs from species richness and evenness. What is a biological community? What is a biological community? A group of populations of different species living close enough to interact Plants, animals, and microbes are linked by interactions (e.g. predation, competition, mutualism) Often defined spatially, and by the dominant life form  Communities Savanna community Rocky intertidal Longleaf pine community What is Community Ecology? Study of the distribution and abundance of populations of coexisting species, and their interactions.  Types of Interactions + - 0 + Predation mutualism Parasitism Commensalism Herbivory - Predation Parasitism Herbivory Competition Amensalism NOTE: THE +, - 0 SIGNS REFER TO EFFECTS OF ONE SPECIES ON PER CAPITA GROWTH OF THE OTHER SPECIES  I Learning Catalytics Therefore I Am  A B A B ! What type of interaction between species A and B is represented by the graph above? A. Mutualism B. Predation C. Commensalism D. Competition Interactions between species that have a positive effect on one species and NO effect on the other species are referred to as: a. symbiosis b. predation c. commensalism d. competition  Competition (-/-) any use or defense of a limiting resource by an individual that decreases the resource availability to others interspecific competition – between species intraspecific competition -- within a species  Limiting Resources food water nutrients space any factor used by an organism which affects population growth rates  Learning Catalytics In a population with logistic growth, dN/dt declines over time due to: a. Predation b. Interspecific competition c. Intraspecific competition d. Mutualism Species often use resources differently Example: Carribean anole species canopy height Leading to question: can two species that use resources in exactly the same way coexist? GF Gause 1930s  Gause’s principle: Competitive Exclusion Principle - Two species cannot coexist indefinitely on the same limiting resource (Gause 1934) Basically, two species cannot occupy the same NICHE What’s a niche? The requirements of a species with respect to ALL resources and physical conditions What’s a niche? The requirements of a species with respect to ALL resources and physical conditions 3 axes of a particular bird species’ niche:  The Niche Concept Fundamental vs. realized niche With Balanus removed… Realized niche: niche in the Fundamental niche: niche in the presence of biotic interactions absence of biotic interactions  In nature…. coexistence of species is the norm Species tend to “partition” resources to minimize competition  Resource partitioning A second bird species might use the same resources, but forage in a higher-light environment Competition can shape the evolution of traits (e.g., beak size) This is called “character displacement”  Besides resource partitioning, how else might species coexist? Stronger competitor Weaker competitor high abundance > lower abundance Predator-mediated species coexistence Stronger competitor > Weaker competitor Another way coexistence can be facilitated… Green and brown anoles occupy the same trees and eat the same insects… But differ in average perch height…  Species coexistence insects in diet brown green anoles anoles canopy height Intraspecific competition ? Interspecific competition  Species coexistence insects in diet brown green anoles anoles canopy height Intraspecific competition > Interspecific competition Enough about competition and predation! What about mutualism? +/+ Mutualisms are “biological markets”! Nutrition - corals mycorrhizae Protection - clownfish, anenome ant-plant Transport - pollination seed dispersers And finally… What do we mean by “species diversity”? Species diversity species richness is the total number of species species evenness relates to the relative abundance of each species higher diversity = more species with more equal abundance See you Friday!