How are evolution and ecology related? Ecology involves understanding of relationships of organisms with each other and with their environment Evolution involves changes in species in response to interactions with each other and with their environment…

Evolution: ‘unfolding’ – process by which species are altered Species change over generations New species appear Species become extinct

Contributions to Modern Evolutionary Thought “Malthusian catastrophe” Thomas Malthus – economist, social philosopher – populations of all organisms eventually out-grow available resources

Gregor Mendel (1822-1884): concepts and patterns of inheritance

Catastrophism Vs Uniformitarianism. Catastrophism- he Earth’s surface has been scarred by catastrophic natural disasters Charles Lyell: theory of uniformity – surface of earth has gradually changed, earth much older than previously recognized "The Present is the Key to the Past"

Fig. 2.3 Darwin’s Voyage Charles Darwin: synthesis of theory of evolution based on natural selection

Out of this study grew several related theories: one, evolution did occur; two, evolutionary change was gradual, requiring thousands to millions of years; three, the primary mechanism for evolution was a process called natural selection; and four, the millions of species alive today arose from a single original life form through a branching process called "speciation."

Forces driving evolution: over-reproduction genetic variability selective pressure environment –(food, temperature, etc.) disease predators survival and reproduction of organisms best suited to their environment

Review articles Scot Norris’ paper Evolution's "Driving Force" Shifts Based on Behavior, Study Says http://news.nationalgeographic.com/news/2006/11/061116-lizard-evolution.html Jonathan Losos' paper "Adaptation and speciation in Greater Antillean anoles" http://biosgi.wustl.edu/%7Elososlab/losos.2004.adaptivespeciationbook.pdf

Genetics and Evolution Trait: appearance/ability to carry out some process Phenotype: appearance of an organism due to a specific trait or combination of traits Gene: genetic information (region on a chromosome) which codes for a specific trait. Allele – variant form of a gene

Figure 2.7bc

Natural selection can favor, disfavor, or conserve the genetic make-up of a population: Stabilizing Selection Directional Selection Disruptive Selection

Stabilizing Selection- also known as ‘Purifying Selection’ Stabilizing selection acts to impede changes in a population by acting against extreme phenotypes and favoring average phenotypes.- prevents divergence from form and function but genetic diversity decreases

Directional Selection Directional selection leads to changes in phenotypes by favoring an extreme phenotype over other phenotypes in the population. Increase frequency independent of dominance

Disruptive Selection- also called ‘Diversifying selection’ Disruptive selection creates bimodal distributions by favoring two or more extreme phenotypes over the average phenotype in a population.- driving force of sympatric speciation- (Finch population Darwin)

‘Ecosystems’ ability to absorb shocks and disturbances Fig. 2.18 ‘Ecosystems’ ability to absorb shocks and disturbances

Species evolve to fill different niches What is a species? ‘A group of similar appearing organisms which share the same gene pool’ Species evolve to fill different niches Example: Finch evolution in Galapagos Islands Result: Radial Evolution Single ancestral form Many generations  unique species for different niches

Speciation of Finch on Galapagos Islands- C. Darwin Fig. 2.10 Speciation of Finch on Galapagos Islands- C. Darwin

How do new species arise? Sympatric speciation Allopatric speciation

Sympatric speciation: occurs as a species fills different niches within the same habitat or geographic area Spread of species into new areas Founding population in isolated location Geologic changes – gradual process

Allopatric speciation: spatial isolation – occurs due to geographic isolation Genetic changes (as ploidy levels in plants) Disruptive selection: divergent genotypes favored

Geographic Variation Within Species Cline: measurable, gradual change in a trait over geographic region Ecotype: Population adapted to particular local environment Geographic isolate: reproductively isolated populations subspecies

competative exclusive principle Gause’s Law- competative exclusive principle Georgii Frantsevitch Gause a theory which states that two species competing for the same resources cannot stably coexist, if the ecological factors are constant. Either of the two competitors will always have an advantage over the other that leads to either the extinction of the inferior competitor or its evolutionary shift towards a different ecological niche.

Geographic Isolation of Ensatina escholtzii populations in CA ‘ring species’ – geographically isolated populations surround uninhabitable area Adjacent populations can interbreed Reproductively incompatible at extremes (black) Figure 2.16

Local E.escholtzii

Changes within a species are due to changes in its gene pool – causes: Selective pressures Genetic drift and bottleneck effects Isolated populations Effect greater in small populations

Variation Within Populations Variation in Plant Populations Many plant species differ dramatically in form from one elevation to another. Clausen et.al. found evidence of adaptation by ecotypes to local environmental conditions in Potentilla glandulosa. Distinctive ecotypes- distinct entity of animal or plant or organism closely linked to its ecological surroundings

Variation in Plant Populations Molecular and Morphological Information Hansen et. al. used randomly amplified polymorphic DNA (RAPD) along with morphological data to support separation of three species of Potentilla.

Ecotypes – Potentilla glandulosa – sticky cinquefoil Alpine Midelevation lowland

How genetically different are ecotypes? Work with Potentilla nivea (a species complex) Morphological (appearance) observations suggest three species Molecular analysis via RAPID study supports morphological species distinction

Fig. 8.6

Summary: Organisms become ‘tailor made’ for their role niche within an environment by processes of evolution New species arise from preexisting species New species arise as organisms become reproductively isolated Reproductive isolation may often result in genetically different populations

Questions How do we know that a species is a species if we do not directly observe whether it can interbreed with other organisms?  If one population is the ancestor to another, how do we decide if they are more than one species?  Does extinction imply mistakes by an "intelligent designer"? How, in terms of Gause's law, does a catastrophic event influence subsequent evolutionary events. Which (and why) are more likely to become extinct, a highly specialized species extremely well adapted to a particular niche, or a less specialized generalist?