Unit 3 Species compete for limited resources interspecific competition Limiting resources Aquatic space light nutrients etc Terrestrial space light nutrients water pollinators seed dispersers etc Types of competition Intraspecific competition Between members of a single species Survival of the fittest Interspecific competition Between members of different species For niches and species coexistence we will be focusing on interspecific Competition is strongest between species that use resources similarly No two species can utilize the same resource in the same way at the same time One will succeed and the other will not Competitive exclusion principle Interspecific competition If two species coexist in a stable environment then they do so as a result of niche differentiation If there is no such differentiation then one competing species will eliminate the other Individuals of one species suffer a reduction in fecundity survivorship or growth as a result of resource exploitation or interference by individuals of another species Two types Exploitaion Interference Individuals of one species inhibit individuals of another species indirectly through the consumption of a shared resource Individuals of one species inhibit individuals of another species directly by preventing their consumption of a shared resource The weaker competitor will cede the overlapping resource niche space If there is a remaining resource for the weaker competitor then both survive Competition for a resource Option one one winner competitive exclusion Niche The environmental conditions necessary for the survival and reproduction of a species It is how it makes its living Includes both physical environment and interactions it has with other species Describes how a species responds to the distribution of resources and competitors and how it in turn alters those same factors limiting access to resources by other organisms The type and number of variables comprising the dimensions of an environmental niche vary from one species to another Each species carves out an area in the niche space where it can outcompete species with similar requirements Competitors use resources differently leading to coexistence Nice size The size of a niche can vary Specialists narrow niches specialized requirements Generalists wide niches In a biodiverse ecosystem are there more generalists or specialist Which is better able to deal with ecosystem variability corals specialist Generalist Fundamental niche Realized niche The entire set of conditions under which an organism population or species can survive and reproduce The niche potentially occupied by a species The set of conditions actually used by a given organism population or specie after interactions with other species predation and especially competition have been taken into account The niche actually occupied by a species When resource uses overlap niche partitioning Three plant species black blue red in an ecosystem compete for a niche One blue outcompetes the growth rate They partition the resource and evolve to specialize in different conditions They continue to utilize the same resource but divide it in different ways Resource partitioning is considered one of the main processes dividing diversification in ecological communities because it allows coexistence among closely related and ecologically equivalent species Why are there many species of winter annuals in the Sonoran desert Annuals live their whole lifecycle from seed to seed in one year Trade off between rapid growth and drought tolerance Fast growers water users Slow growers water conservers Species can coexist by using resources differently Mesquite tree and saguaro cactus The tree uses long roots to go down to the lower water table while the cactus uses roots that grow outwards to collect rainfall from a larger area Temporal niche partitinoing Same resources but at different times day vs night Spring ephemerals bloom at different times thus partitioning the pollinator niche and optimizing pollinator visitation for each plant species Spatial niche partitioning Closely related bird species occupy different foraging locations on a singular tree Several anole lizards in the Caribbean islands share common diets mainly insects They partition their food niche by occupying different physical locations Some lice on the ground while others are arboreal A functional niche refers to a species position in food webs and trophic Functional niche partitioning cascades Ecological time scales Evolutionary time scales Combines the ecological requirement of the species Refer to changes over the course of a single generation or a few generations Action over many generations Natural selection can lead to major changes in the adaptive fit of a species to its biotic and abiotic environment The outcome of interspecific competition on an evolutionary time scale is called character displacement When two species occur in sympatry natural selection should favor the evolution of mechanisms that reduce competition This often takes the form of character displacement Increased differences between species in regions when they co occur Given some degree of overlap in resource use species should be under selection to evolve niche dimensions with less overlap Ecological release when a species expands its niche under conditions where the other species is absent Neutral theory species are so similar that neither outcompetes the other Lecture 2 ITN discussion why are seals and otters afraid of cats Toxoplasma gondii Not bacteria not virus protist eukaryote Nucleus mitochondria organelles Biologically more closely related to us than bacteria virus Viruses are relatively easy to develop vaccines against because they re relatively simple Antiviral treatments are less simple For when someone is already infected Ex neuraminidase inhibitors for flu Bacteria are treated with things like these called antibiotics Penicillin naturally produced compound that interferes with production of peptidoglycan walls which are found in bacteria but not humans Toxoplasma gondii continued Complexity hard to make vaccines Unlike covid which has one spike protein not case with eukaryotic pathogens have more complexity with antigen presentation Eukaryotic hard to treat whats infected Malaria is very closely related to this The tissues cyst forming coccidium toxoplasma gondii is one of the more polyxenous can infect wide variety parasites known to date Has facultatively