Class Note for ECOL 482 at UA
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Date Created: 02/06/15
Lect 19 Populations Chapter 23 Different Levels of Ecological Organization Individuals Populations Assembage Community Ecosystem Populations Populations all individuals of a particular species in a given area but need to recognize genetic structure a gene pool that has continuity through time because of reproductive activities of the individuals in the population Populations grow and shrink and that effects genes Four major factors effect populations Birth death immigration emigration Populations Four major factors effect populations Birth death immigration emigration Populations Life Tables birth and death rates age specific reproduction and survivorship used to calculate population change Death rates survivorship Lx Reproductive Output per female Mx Reproductive rate of population LxMx Net Reproductive Rate summation LxMx Migration immigration vs emigration 39ndet GROWTH et size age 0 Site 5 Survivorship curves 4 Sim a S uryival probabilities Ix plotted 3 1 against age x Called quotsurvivorship curvesquot Show 539 7 at what age death rates are quot Site 37 high and low Sin 50 OlEBdSGTBQ gl l39 Survivorship curve illustrated above can be combined with agespecific fertility to estimate population turnover using a life table approach 3 Site 7 Estimate corrected Age Age Gas b I g Ixbx Ixbxx emmbm emmbm 3723 3 3 1 3 713 3 3 3 3 33753 1 1 333 3 713 3 344 3 733 3 733 3 521 3 533 33733 2 1 434 3 457 3 337 3 333 1 333 3 333 3 315 337113 3 1 332 3 273 3 433 3 432 1 335 3 132 3 143 1237143 4 1 3 133 3 173 3 133 3 554 3 334 3 331 1537173 5 3 3 325 3 3 3 3 3 1337233 3 3 3 3 3 3 3 c 2 333 age classes 33 days 3 e e e ret 3 343 ind133233 days 2 2 333 4 313 z 1 351 1 333 Corr 3 323 rEuIer 3 373 ind13mm days Populations Recruitment addition to a population through reproduction eg larval fish settle ln fisheries recruitment refers to Stock potentially catchable individuals Colonization addition of established individuals nursery habitat to adult habitat Year class or cohort strength very important eg if have dense old fish but no young fish the population can collapse very quickly Populations Populations often size structured notjust age Indeterminate growth and overlapping generations create populations of very different size individuals Size can effect where individuals feed Ontogenetic niches and shifts many examples Populations Death eggs and larvae most dangerous time for a fish up to 999 many predators including own species Cannibalism very common in fish Populations Production How much biomass is a fish population producing How much is available to predators including humans without crashing population Can production be predicted from certain life history parameters Populations Production growth rate of individual over time x biomass of age class corrected for mortality Varies from 01 gm2yrfor sockeye salmon in Oregon Lake to 155 gm2yr for Desert Pupfish Most 1 to 10 Tropical and fertilized ponds greater Populations Annual turnover productionbiomass young sh have small biomass but fast growth rate turnover great index of how productive populations are Populations Genetic Structure of populations vs Physical Structure of population Gene flow exchange of genes across boundaries and between populations influences how we View a population Demes Distinct genetic groupings vs species such as eels distinct physical populations but reunite to spawn Panmictic Spawning entire species consists of one population eg all individuals have equal probability of reproducing vs genetically discrete stocks salmon will be physically together for most of life but will have genetically distinct stocks that separate and return to their natural streams Populations Genetic vs ecophenotypic differentiation Arctic char distinct genetic populations within a lake four distinct morphs that are genetically and ecologically distinct feeding inshore v offshore coloration etc Populations Genetic vs ecophenotypic differentiation differences are genetic not ecophenotypic like cichlid pharyngeal jaws can be Populations Understanding genetic makeup has become increasingly important as species decline and are overexploited Degree of genetic variation in population is key Herring Metapopulation Populations Genetic vs ecophenotypic differentiation differences are genetic not ecophenotypic like cichlid pharyngeal jaws can be Populations Understanding genetic makeup has become increasingly important as species decline and are overexploited Degree of genetic variation in population is key Herring Metapopulation Populations Guilds quot ecological rather than taxonomic similarities habitat preferences in streams feeding preferences Populations Fish often classified by habitat preferences Habitat Use and Choice Fish have specific habitat use many examples of convergence between systems and lakes etc can change with season ontogeny Deeper bigger Predation influence cannibalism can also influence cottids and bluegills 11 Populations Competition intra vs interspecific resource partioning in sympatric speCIes Predation Direct effects v indirect effects Density dependent Direct density dependence compensatory predation increases to compensate for increases in prey population size Inverse density dependence depensatory relatiye predation risk and impact decrease as prey numbers increase fixed number of predators become swamped salmon smolt spawning runs Predation effects major both population geneticstructure primarily in young exponentially declining mortality TROPHIC CASCADES amp TOPDOWN vs BOTI39OMUP predaceous fish TOP CARNIVORES quot39 03 F 13 CARNIVORES gt onoppme g Zooplanklori r herbivorous crustaceans HERBIVORES 4 CROPPING PRODUCERS cmle 3 E g CD fix RESOURCES LIGHTI NUTRIENTS l 13
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