Charles Darwin, Conservation, & Evolution

Environment 121Conservation of Biodiversity

Professor Victoria Sork2 April 2009

Outline of Lecture

1. Charles Darwin as conservation biologist: biography

2. Darwin’s theory of evolution by natural selection

3. Other evolutionary forces important to conservation biology– Genetic drift– Gene flow

4. Speciation

Charles Darwin biography

Family life• Bon Feb 12, 1809• Fifth of six children in Shrewsbury,

England• Father, Robert Darwin, physician• Grandfather, Erasmus Darwin,

famous poet• Mother, Susannah Wedgwood, died

when he was 9 years old• 1839, married his Emma Wedgwood• Their family: ten children, seven of

whom reach adulthood.

Darwin: Edinbergh years, 1825-1927

• Attended Edinburgh to become physician• Became interested in marine invertebrates under

Robert Grant• First time Darwin’s name in print (Darwin was 18 yrs

old):

RECORD: Grant, R. E. 1827. Notice regarding the ova of the Pontobdella muricata, Lam. Edinburgh Journal of Science 7 (1): 160-161.

…”We find these ova generally in groups of thirty or

forty adhering to solid bodies in deep water where the Pontobdella resides. The merit of having first ascertained them to belong to that animal is due to my zealous young friend Mr Charles Darwin of Shrewsbury, who kindly presented me with specimens of the ova exhibiting the animal in different stages of maturity.”

Darwin: 1827-1831, Cambridge year

• Switched to Christ’s College, Cambridge• Decided he did not want to become a

physician• Father suggested he become a clergyman• Attractive to Darwin because he could

become an amateur naturalist• At Cambridge, he studied for BA as

preparation to enter Theological school• Not a great student, but amazing

naturalist• Began collecting beetles• Studied under a Professor of Botany who

later got him onto the Beagle• Before graduating, he studied geology

Darwin’s voyage on the Beagle: 1831-1836

Major stops on Voyage1832:

– tropical shore at St Jago, Cape Verde Islands– east coast of South America. – Tierra del Fuego.

1833 Beagle visits Falkland Islands. 1834

– Tierra del Fuego and another visit to the Falkland Islands. April to May – Darwin and FitzRoy make an inland expedition along the River Santa Cruz. – Surveys of the west coast of South America.

1835– Valdivia, Concepcion, Copiapo, Iquique,Callao, Lima – Tahiti– New Zealand.

1836– Sydney Hobart, Cocos Islands and Keeling Islands followed by Mauritius. – Cape of Good – Crosses Atlantic ocean calling at St Helena and Ascension Island– Brazil, Azores – 2 October, Beagle drops anchor at Falmouth, England

Influences on Darwin

• astronomer Sir John Herschel• traveller Alexander von Humboldt • Geologist Charles Lyell. Principles of

Geology (1830-3)• Grandfather Erasmus Darwin,

evolutionary speculations• French zoologist Jean-Baptiste Lamarck.• 1838 Darwin read Thomas Malthus's Essay

on the Principle of Population (1798). Malthus argued that human population growth, unless somehow checked, would necessarily outstrip food production.

Selected Books of Charles Darwin (out of 25)• 1839: Thhree volume narrative of the Beagle voyage "Journal of Researches into the Natural

History and Geology of the Countries Visited During the Voyage of H.M.S. Beagle”. Co-authored by Capt. Philip King, Capt. Robert FitzRoy, and Charles Darwin

• 1839: "Journal of Researches into the Natural History and Geology of the Countries Visited During the Voyage of H.M.S. Beagle.”

• 1842-1846: Three books on Geological Observations of South America • 1859: "The Origin of Species by Means of Natural Selection: Or, the Preservation of Favored Races

in the Struggle for Life”• 1862 "On the Various Contrivances by which British and Foreign Orchids and fertilized by Insects• 1864: "The Movement and Habits of Climbing Plants”• 1868: "The Variations of Animals and Plants under Domestication• 1871: "The Descent of Man and Selection in Relation to Sex”• 1872 "The Expression of the Emotions in Man and Animals” • 1875: "Insectivorous Plants”. • 1877: "The Different Forms of Flowers on Plants of the Same Species" was published by John

Murray publishers of London. • 1879: "The Movement and Habits of Climbing Plants• 1881: "The Formation of Vegetable Mould, through the Actions of Worms, with Observations on

Their Habits”

Darwin’s Essay of 1944, predating his 1859 bookPART IChapter I: on the variation of organic beings under domestication; and on the principles of selection.Chapter II: on the variation of organic beings in a wild state; on the natural means of selection; and on

the comparison of domestic races and true species.Chapter III: on the variation of instincts and other mental attributes under domestication and in a state

of nature; on the difficulties in this subject; and on analogous difficulties with respect to corporeal structures.

PartII. On the evidence favourable and opposed to the view that species are naturally formed races, descended from common stocks.

Chapter IV: on the number of intermediate forms required on the theory of common descent; and on their absence in a fossil state

Chapter V: gradual appearance and disappearance of species. Chapter VI: on the geographical distribution of organic beings in past and present times.Chapter VII: on the nature of the affinities and classification of organic beings.Chapter VIII: unity of type in the great classes; and morphological structures.Chapter IX: abortive or rudimentary organs.Chapter X: recapitulation and conclusion.Recapitulation—Why do we wish to reject the Theory of Common Descent?—Conclusion ........ 239-255

Darwin’s Theory of Evolution by Natural Selection

“As many more individuals of each species are born than can possibly survive; and as, consequently, there is a frequently recurring struggle for existence, it follows that any being, if it vary however slightly in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of surviving, and thus be naturally selected. From the strong principle of inheritance, any selected variety will tend to propagate its new and modified form.”

Origin of Species (1859)

Other Darwin images…

Down House where Darwin worked and lived with family.Celebration of Darwin’s Statue at Museum of Natural History

Darwin at 65

Theory of Evolution by Natural Selection

TheoryDifferential survival and reproduction of individuals with genotypes that are adapted to a specific environment.

Requisite – Phenotypic Variation– Genetic variation: stuff of evolution

Outcome– Phenotypes adapted to environment– Change in fitness of populations

Kettlewell’s peppered moth experiments

Change in Frequency of peppered moths in Industrial England

• Mark-and-recapture experiments• Showed that dark moth frequency

increased in polluted woods. Rapid evolutionary change

Recapture success

light moth dark moth

non-industrial woods

14.6 % 4.7 %

industrial woods 13 % 27.5 %

Darwin’s contribution to biodiversity

1. Darwin’s observations on species diversity are early version of biodiversity studies

2. His notes indicate that he believed species evolved from other species

3. Interestingly, natural selection explains microevolution better than macroevolution

4. Speciation, often follows reproductive isolation: – e.g. Darwin’s finches on Galapagos islands– Selection and reproductive isolation leads

to news species

Evolution since Darwin: Genetic drift

• Important evolutionary force• Sampling error• Important in small populations• Founder effects are example of genetic drift• Results in loss of genetic variation• Results in loss of adaptive variation• Darwin didn't know about genetic drift,

which is why modern evolutionary biologists are no longer "Darwinists"

Evolution since Darwin: Gene flow

• Movement of gene affects the distribution of genotypes• Plants: pollen or seeds• Animals: dispersal of young or movement of adults

• Occurs at varying spatial and temporal scales– Within local population—affects who mates with whom– Among populations, also called migration

• homogenizes populations• Can reduce impact of natural selection and local adaptation

– Long term gene movement:• Historical migration (e.g. humans)• phylogeography

Spring ‘07

Quercus lobata (Née)Continuous populations in oak savanna genotype seeds and adults paternity analysis

SDD - measured

Example: Local gene movement via pollen movement

Example of migration among populations

Study of Lizards on Caribbean Islands

Found that ocean currents influenced pattern of migration

Post-Pleistocene migration of oaks in Europe

Distribution of choloroplast haplotypes

R1 R2

R3

Recolonization routes