What is Evolution Speciation What is Evolution Evolution is separated into What is Evolution Take a closer look at this process Generation 2013 anagenesis evolution within a species lineage Darwin s modification cladogenesis evolution to form new species lineages or speciation Darwin s descent Generation 2012 in outcrossing diploid organisms each offspring of the next generation receives a copy of genetic material from two parents in 2012 who in turn had received their copies of genes from two parents of the preceding generation in 2011 What is Evolution What is Evolution As you go back in time to earlier generations the genetic connections appear as a network within the population of interbreeding individuals back in time back in time even furtherback in time the genetic connections appear as a braided rope within a species discernible populations of interbreeding individuals are recognized within a species anagenesis can occur within a species lineage through time 1 Population back in time What is Evolution as you go back even further in time in this tree or phylogeny the formation of species and the extinction of species fossils are seen cladogenesis or speciation occurs when there is complete genetic isolation between groups of once connected populations What is Evolution Systematics often divided into two areas phylogenetics or pattern and biosystematics or process tree reticulation What is Evolution What is Evolution Systematics often divided into two areas phylogenetics or pattern and biosystematics or process Systematics often divided into two areas phylogenetics or pattern and biosystematics or process Is this a simple dichotomy of shifting from a reticulating process at or below species level to a tree pattern above species Is this a simple dichotomy of shifting from a reticulating process at or below species level to a tree pattern above species NO tree reticulation reticulation Genetic Variation within Species Trees show reticulation above species tree Genes show tree patterns in species Genetic Variation within Species Evolution requires source of genetic variation and a driving force Evolution requires source of genetic variation and a driving force Genetic variation within species is the rule human selection or natural selection or random events involved Variation seen in flowers pollinators light regimes moisture regimes chromosome number Capsicum pepper Claytonia spring beauty Claytonia spring beauty Genetic Variation within Species Modern genetic tools indicate substantial genetic variation within and among populations of species raw material for natural selection or random events to act upon Genetic Variation within Species Evolution requires source of genetic variation and a driving force Natural selection mechanism by which populations become modified in response to the environment Adaptation adjustment of the population to the environment Monotropa hypopithys pinesap Genetic Variation within Species Claytonia spring beauty Genetic Variation within Species used a reciprocal transplant design by setting up common garden sites across an elevation gradient from coastal California through the Coast Range and up and over the Sierra Nevada three American botanists documented this linkage with their studies on a variety of plant species in California during 1940 1950s their work on the Achillea millefolium yarrow and Potentilla glandulosa sticky cinquefoil complexes are the best known Clausen Hiesey Keck Common garden at Stanford Potentilla Achillea Common garden at Mather Genetic Variation within Species Genetic Variation within Species Achillea lanulosa exhibits clinal phenotypic variation in natural populations across the elevational gradient in the Sierra Nevada populations exhibit marked lowering of fitness and adaptation when placed at other sites clinal genotypic variation or the formation of ecotypes Achillea lanulosa Genetic Variation within Species Genetic Variation within Species Evolution requires source of genetic variation and a driving force Evolution requires source of genetic variation and a driving force Random Events gene frequencies may fluctuate despite natural selection owing to random sampling of genes genetic drift founder events Random Events gene frequencies may fluctuate despite natural selection owing to random sampling of genes genetic drift founder events 2012 or Area A 2013 or dispersal to Area B effect is greatest in small isolated populations on islands e g cloud forest peaks in central Panama Genetic Variation within Species Speciation Evolution requires source of genetic variation and a driving force Cladogenesis formation of new species Random Events gene frequencies may fluctuate despite natural selection owing to random sampling of genes genetic drift founder events anagenesis evolution within a species lineage Darwin s modification widespread lower elevation Lisianthius skinneri and isolated cloud forest taxa How to Define Species Cladogenesis formation of new species How do you define species Ernst Mayr difficult due to continuum of evolutionary processes and products cladogenesis evolution to form new species lineages or speciation Darwin s descent How to Define Species common occurrence of hybrids even between genera has made the BSC less attractive to botanists emphasis on reproductive isolating mechanisms Platanus x hybrida sycamore How to Define Species phylogenetic species concepts based on genealogical separations reproductive isolation of groups of populations others morphological species ecological species all concepts have pros and cons no universal concept Reproductive Isolation Many kinds of isolating mechanisms Ecological or habitat isolation species adapted to harsh heavy metal serpentine soils in California ecological separated from crossing with those that do not Ceanothus on Catalina Island Reproductive Isolation Seasonal or temporal isolation different times of reproduction Reproductive Isolation Seasonal or temporal isolation different times of reproduction co occurrence of many congeners in tropical forests possible with asynchronous flowering Reproductive Isolation Mechanical isolation variation in floral form prevents interspecies pollen movement pollen placement or floral form in pseudocopulatory orchids Reproductive Isolation Mechanical isolation variation in floral form prevents interspecies pollen movement Mimulus cardinalis few genes generated the floral differences that maintain reproductive