Charles Darwin and Natural Selection In 1840, age 31 Born 12 Feb 1809 Naturalist on the 2nd Voyage of the HMS Beagle – 1831-1836 Wrote The Voyage of the Beagle, The Origin of Species, ..

Voyage of the HMS Beagle 1831-1836 Salvador Rio de Janeiro

Darwin in the Neotropical Forests Rio de Janeiro – April 1832 “It was impossible to wish for any thing more delightful than thus to spend some weeks in so magnificent a country. “In England any person fond of natural history enjoys in his walks a great advantage, by always having something to attract his attention; “but in these fertile climates, teeming with life, the attractions are so numerous, that he is scarcely able to walk at all."

Voyage of the HMS Beagle Galápagos Is.

Galápagos Islands

Galápagos Islands Great Isolation ~1000 km 1045 km ~600 miles

“Darwin’s Mockingbirds” Images http://people.rit.edu/rhrsbi/GalapagosPages/mockingbird.html http://www.greglasley.net/charlesmock.html -- The Charles Mockingbird (Nesomimus trifasciatus) is one of the rarest birds in the world. Only 40 to 60 individuals are thought to survive on tiny Champion Island in the Galapagos. More: http://en.wikipedia.org/wiki/Floreana_Mockingbird Total of 5 species

Darwin’s Finches Total of 13-14 species

Darwin’s Finches Character displacement within species – space for time Genovesa Espanola

Evolutionary Change Evolution is the observation of change in heritable traits with time Changes can occur through selective (deterministic) or random (stochastic) processes. Selection – natural selection, artificial selection Stochastic – genetic drift, founder effect, Stochastic – genetic drift, founder effect,

Natural Selection Resources are limited Potential reproduction exponential Actual population growth limited by resources So, Individuals must compete Variability among individuals in inheritable traits with respect to resource utilization Competition results in some traits being passed to successive generations at a higher frequency

Natural Selection Competition results in some traits being passed to successive generations at a higher frequency Differential survival only important if it results in differential reproduction Differential survival is of individuals Natural selection acts on individuals but results in change frequency of traits in populations.

Peter & Rosemary Grant’s Finches Character displacement within species – in time Daphne Major

The Grants’ Finches POPULATION SIZE SEED ABUNDANCE Character displacement within species – in time POPULATION SIZE Medium Ground Finch large, tough seeds SEED ABUNDANCE http://www.pbs.org/wgbh/evolution/library/01/6/l_016_01.html : Finch Beak Data Sheet: Few people have the tenacity of ecologists Peter and Rosemary Grant, willing to spend part of each year since 1973 in a tent on a tiny, barren volcanic island in the Galapagos. Even fewer would have the patience to catch, weigh, measure, and identify hundreds of small birds and record their diets of seeds. But for the Grants, the rewards have been great: They have done nothing less than witness Darwin's theory of evolution unfold before their eyes. That would have stunned Darwin, who thought natural selection operated over vast periods of time and couldn't be observed. In their natural laboratory, the 100-acre island called Daphne Major, the Grants and their assistants watched the struggle for survival among individuals in two species of small birds called Darwin's finches. The struggle is mainly about food -- different types of seeds -- and the availability of that food is dramatically influenced by year-to-year weather changes. The Grants wanted to find out whether they could see the force of natural selection at work, judging by which birds survived the changing environment. For the finches, body size and the size and shape of their beaks are traits that vary in adapting to environmental niches or changes in those niches. Body and beak variation occurs randomly. The birds with the best-suited bodies and beaks for the particular environment survive and pass along the successful adaptation from one generation to another through natural selection. Natural selection at its most powerful winnowed certain finches harshly during a severe drought in 1977. That year, the vegetation withered. Seeds of all kinds were scarce. The small, soft ones were quickly exhausted by the birds, leaving mainly large, tough seeds that the finches normally ignore. Under these drastically changing conditions, the struggle to survive favored the larger birds with deep, strong beaks for opening the hard seeds. Smaller finches with less-powerful beaks perished. So the birds that were the winners in the game of natural selection lived to reproduce. The big-beaked finches just happened to be the ones favored by the particular set of conditions Nature imposed that year. Now the next step: evolution. The Grants found that the offspring of the birds that survived the 1977 drought tended to be larger, with bigger beaks. So the adaptation to a changed environment led to a larger-beaked finch population in the following generation. Adaptation can go either way, of course. As the Grants later found, unusually rainy weather in 1984-85 resulted in more small, soft seeds on the menu and fewer of the large, tough ones. Sure enough, the birds best adapted to eat those seeds because of their smaller beaks were the ones that survived and produced the most offspring. Evolution had cycled back the other direction. http://www.pbs.org/wgbh/evolution/library/01/6/l_016_01.html

The Grants’ Finches Character displacement within species – in time 1976 1978 http://www.pbs.org/wgbh/evolution/library/01/6/l_016_01.html : Finch Beak Data Sheet: Few people have the tenacity of ecologists Peter and Rosemary Grant, willing to spend part of each year since 1973 in a tent on a tiny, barren volcanic island in the Galapagos. Even fewer would have the patience to catch, weigh, measure, and identify hundreds of small birds and record their diets of seeds. But for the Grants, the rewards have been great: They have done nothing less than witness Darwin's theory of evolution unfold before their eyes. That would have stunned Darwin, who thought natural selection operated over vast periods of time and couldn't be observed. In their natural laboratory, the 100-acre island called Daphne Major, the Grants and their assistants watched the struggle for survival among individuals in two species of small birds called Darwin's finches. The struggle is mainly about food -- different types of seeds -- and the availability of that food is dramatically influenced by year-to-year weather changes. The Grants wanted to find out whether they could see the force of natural selection at work, judging by which birds survived the changing environment. For the finches, body size and the size and shape of their beaks are traits that vary in adapting to environmental niches or changes in those niches. Body and beak variation occurs randomly. The birds with the best-suited bodies and beaks for the particular environment survive and pass along the successful adaptation from one generation to another through natural selection. Natural selection at its most powerful winnowed certain finches harshly during a severe drought in 1977. That year, the vegetation withered. Seeds of all kinds were scarce. The small, soft ones were quickly exhausted by the birds, leaving mainly large, tough seeds that the finches normally ignore. Under these drastically changing conditions, the struggle to survive favored the larger birds with deep, strong beaks for opening the hard seeds. Smaller finches with less-powerful beaks perished. So the birds that were the winners in the game of natural selection lived to reproduce. The big-beaked finches just happened to be the ones favored by the particular set of conditions Nature imposed that year. Now the next step: evolution. The Grants found that the offspring of the birds that survived the 1977 drought tended to be larger, with bigger beaks. So the adaptation to a changed environment led to a larger-beaked finch population in the following generation. Adaptation can go either way, of course. As the Grants later found, unusually rainy weather in 1984-85 resulted in more small, soft seeds on the menu and fewer of the large, tough ones. Sure enough, the birds best adapted to eat those seeds because of their smaller beaks were the ones that survived and produced the most offspring. Evolution had cycled back the other direction. http://www.pbs.org/wgbh/evolution/library/01/6/l_016_01.html

The Grants’ Finches Character displacement within species – in time Relationship between beak depth of offspring and their parents in the medium ground finch (Geospiza fortis) population on Daphne Major The line reflects trait inheritance Not necessarily monotonic 1978 1976 http://www.pbs.org/wgbh/evolution/library/01/6/l_016_01.html http://www.pbs.org/wgbh/evolution/library/01/6/l_016_01.html

Evolutionary Change Evolution is the observation of change in heritable traits with time Natural selection is a deterministic process through which heritable traits change with time. Observed in – Character displacement within species – space for time 1976 1978 Stochastic – genetic drift, founder effect, – in time

Wallace’s Line The coming together of 2 long separated biota Wallace’s Line, running through the middle of Indonesia, distinguishes faunal affinities of Indo-Malaysia vs. of Australasia – even though Indonesia is a string of closely spaced islands. Why might this have come about? See WallaceLine wikip706.pdf (and E4 WallaceLine.ppt with figs) – In this region, the Australian plate is gradually catching up with the Asian plate. The result is current close geography of 2 faunas that have been long isolated for some groups. This is to say that Wallace’s Line is a bit fuzzy, applying to birds, with other “Line’s” apparent (mammals, freshwater fish) – the broad transitional region is consequently recognized as a separate zoogeographical region, Wallacea.

Wallace’s Line This isolation has been maintained by a deep channels between Bali & Lombok, Borneo & Sulawesi that precluded the formation of land bridges at lower sea levels, limiting migration. The islands are a mix of pieces breaking off of the larger masses (Sulawesi from Borneo 50Mya) or forming in place (volcanic island arc along the subducting Indian plate) – their recent formation of the smaller islands being one possible factor in being lower in Asian faunal elements. “Sulawesi (Celebes) … In the west it is divided from Borneo and thus from the Asian mainland by the narrow but deep Makassar Strait. Even during the ice age with its low sea level Sulawesi was never actually connected to Borneo. Of the known Sulawesi fauna 62% of mammal, 27% of the bird 62% of reptile and 76% of amphibian species are endemic! For example there are marsupials (related to Australian kangaroos and possums) on the eastern islands, but they are not seen in Borneo which lies west of Sulawesi. These animals reached Sulawesi by hopping across landbridges during the ice age coming from Australia.” – See p. 9 of WallaceLine wikip706.pdf

Wallace’s Line Illustr of spp separation Wallace’s Line, running through the middle of Indonesia, distinguishes faunal affinities of Indo-Malaysia vs. of Australasia – even though Indonesia is a string of closely spaced islands. Why might this have come about? See WallaceLine wikip706.pdf (and E4 WallaceLine.ppt with figs) – In this region, the Australian plate is gradually catching up with the Asian plate. The result is current close geography of 2 faunas that have been long isolated for some groups. This is to say that Wallace’s Line is a bit fuzzy, applying to birds, with other “Line’s” apparent (mammals, freshwater fish) – the broad transitional region is consequently recognized as a separate zoogeographical region, Wallacea. Illustr of spp separation

Wallace’s Line This isolation has been maintained by a deep channels between Bali & Lombok, Borneo & Sulawesi that precluded the formation of land bridges at lower sea levels, limiting migration. The islands are a mix of pieces breaking off of the larger masses (Sulawesi from Borneo 50Mya) or forming in place (volcanic island arc along the subducting Indian plate) – their recent formation of the smaller islands being one possible factor in being lower in Asian faunal elements. “Sulawesi (Celebes) … In the west it is divided from Borneo and thus from the Asian mainland by the narrow but deep Makassar Strait. Even during the ice age with its low sea level Sulawesi was never actually connected to Borneo. Of the known Sulawesi fauna 62% of mammal, 27% of the bird 62% of reptile and 76% of amphibian species are endemic! For example there are marsupials (related to Australian kangaroos and possums) on the eastern islands, but they are not seen in Borneo which lies west of Sulawesi. These animals reached Sulawesi by hopping across landbridges during the ice age coming from Australia.” – See p. 9 of WallaceLine wikip706.pdf