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Unformatted text preview: ES 100 Lecture 4 ES 100 Lecture 4
I. Accidents of history II. Populations Section rooms have been changed: Section rooms have been changed:
ENV S 100 0106 W 4pm in Phelps 1444 ENV S 100 0105 W 5pm in Phelps 1440 ENV S 100 0102 R 8am in Phelps 1508 ENV S 100 0103 R 1pm in Girvetz 2124 ENV S 100 0104 F 11am in Phelps 1444 ENV S 100 0101 F 12pm in Phelps 3523 ECTION IS MANDATORY. 20% OF YOUR GRADE DEPENDS ON YOUR PARTICIPATION. My office hrs have been changed My office hrs have been changed TO: WED. 10:1511:30 (no longer on Monday) Gauchospace up and running Gauchospace up and running https://gauchospace.ucsb.edu/ Weekly assignments posted there by TAs. TAs will let you know if you will submit written work on line thru gauchospace. Lecture ppts are posted in clustered files. Recap…. Recap…. Key concepts: Lecture 3 What are key elements of ‘ecotype’ concept? How do you tell if two populations represent ‘ecotypes’? How do you tell if two populations represent different species? Elements necessary for speciation. Today: Today: Accidents of history Adaptations Distributions Population biology What is a population ? Estimating population growth Counting individuals Aging individuals Birth / death schedules I. Accidents of history cautionary talespart 1. Explanations for current morphologies or physiologies OR for patterns of species distributions must include an understanding of history. Section exercise: Section exercise: Traits….why are they there ? Is there an adaptive explanation ? Evolutionary ecology Evolutionary ecology How does an organism’s physiology, morphology or behavior allow it to persist in a particular environment? (How is a particular trait beneficial to fitness [adaptive]?)
MAYBE EVERYTHING IS NOT ADAPTIVE !!! Who would disperse these fruits ? Who would disperse these fruits ?
Large hard fruits Accumulate under trees in tropics Evolved in response to now extinct elephant-like animals animals Current form =leftover adapation from past
Neotropical anachronisms: The fruit the gomphotheres ate. D. Jansen & P. Martin. Chorisia speciosa, native to Brazil and Argentina
Why have these heavy spines ?
Adaptation to extinct large animals ? No pressure yet to lose the trait where it is not needed ? Trait loss may take many thousands of yrs. Santa Lucia fir (Abies bracteata) Occurs only in small part of Occurs California (NOWHERE ELSE) California What is strange shape an adaptation to ? Hypothesis: Shedding of SNOW ? Did it evolve in a more Did snowy environment ? What explains its restricted distribution ? maybe needs cooler microsites? cannot tolerate fire Maybe it evolved under very different climate & fire conditions to what we see today ? Today it just lives in refugia from fire where it what isn’t too hot ? Don’t assume that all traits are ‘adaptations’ to something in current environment!
TO BE AN ADAPATION….. TO BE AN ADAPATION….. Trait must be heritable Must confer a fitness advantage Selective environment must be clear Trait should have appeared historically when selective force became common Traits may become ‘maladaptions’ Traits may become ‘maladaptions’ once selective force is gone Cautionary tales Cautionary tales PART 2. Geographic distributions of species Biogeography…. Biogeography…. Study of geographic distribution of species To understand distribution should know: Physiological limits of species Biotic interactions that limit distribution Dispersal potential of species Historical factors that could influence current patterns Distribution of flightless birds cannot be Distribution of flightless birds cannot be explained without history
-Widely distributed (across oceans!) -Related to one another BUT FLIGHTLESS -So they could not have dispersed to different continents
Could ask…what is it that Selects for flightlessness? (Townsend et al) Continental drift essential to understand pattern Townsend et al. Africa & So. Am. pull apart Tasman sea opens between Australia and NZ Maybe it evolved under very different climate & fire conditions to what we see today ? Today it just lives in refugia from fire where it what iisn’t too hot ? sn’t Many populations have disappeared in last 100 years. Maybe it Many is on its way out. Accidents of history take home Accidents of history take home questions… Why might it be hard to explain the existence of particular traits ? How does geological history influence current distributions of traits and species? II. Population biology II. Population biology What is a population? Counting individuals Estimating population growth Population Population A group of individuals of one species in one place
Anything tricky here ?? Population A group of individuals of one species in one place HOW BIG IS THE PLACE? WHERE ARE ITS BOUNDARIES ? Not a trivial issue Coast live oak: Boundaries? Coast live oak: Boundaries? Use drainage divisions ? Ceanothus (typical chaparral shrub) Boundaries of population ?? Island subspecies is entire Island one population ? or mulitple populations ? Mainland…are there any clear population boundaries in SB County? Or whole state ? ESTIMATING POPULATION ESTIMATING POPULATION SIZE
After defining boundary—want to know if population is growing or shrinking ? Or stable? Challenge 2: Counting individuals Challenge 2: Counting individuals Sessile solitary (unitary) individuals: count the number within a bounded area Mobile organisms: pop. estimation techniques Sessile colonial organisms: First must define an individual then count. Challenge 2: Counting individuals Mobile organisms: pop. estimation techniques Mobile species: Mobile species: Mark/recapture studies (see book) Point counts (birds) Live trap in grids (small mammals) Remote identification of individuals with repeat observations If you can do them, they are useful Must be able to capture the organism, mark it, recapture it Point Counts Point Counts Establish grid of points across area Spend set amount of time at each point Record all birds HEARD at each point Maybe put motion sensitive cameras at strategic locations throughout reserve ? Have you sampled enough locations ? Can you tell individuals apart so you know how many different individuals you are seeing? How many mountain lions are at How many mountain lions are at Sedgwick Reserve ? Sedgwick Reserve: Oak / grazing experiment lower Cucu Mesa water trough Challenge 2: Counting individuals Sessile colonial organisms: First must define an individual then count. Colonial, clonal = modular Colonial, clonal = modular organisms What is an individual ? What is meaningful unit to measure ? Ramet = one module of a modular organisms that could live on its own. Genet = a unique genetic individual (=one clone) Genet = genetic individual. COULD BE ENORMOUS FOR CLONAL INDIVIDUAL.
Example: Armillaria ostoyae Clonal fungus, single individual in Oregon covers 2,200 acres DON’T COUNT INDIVIDUALS!! Useful measure = biomass or frequency over landscape Might want to know extent of individual genotypes “LARGEST organism in world” Ramet: an independent member of a clone Ramet: an independent member of a clone or a module of a clone that could live independently RAMETS One genet with multiple ramets
How fast are ramets produced ? How fast will space become occupied by this species ? Ramets can be hard to distinguish Basic module = polyp Groups of polyps = branches. Branches can break off and survive. For clonal species, to estimate For clonal species, to estimate population size May want to count both ramets and genets —depends on question. Realistically may only be able to count ramets without intensive genetic analyses MAYBE just want to count COVER or colonies in a given area. Estimating population growth, or Estimating population viability Are populations stable ? Are populations heading towards extinction ? Are they increasing ? How do they respond to perturbations ? ...
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- Fall '08