Section II Evolution and Behavioral Ecology Ayo Japalurahotmail

Section II Evolution and Behavioral Ecology 鄭先祐 生態主張者 Ayo Japalura@hotmail. com 生態學 2003 Chap. 2 Genetics and Ecology

Section Two Evolution and Behavioral Ecology • Chap. 2 Genetics and Ecology (遺傳與生態) • Chap. 3 Extinction (滅絕) • Chap. 4 Group selection and individual selection • Chap. 5 Life History Strategies (生活史的策略) 生態學 2003 Chap. 2 Genetics and Ecology 2

Road Map Chap. 2 Genetics and Ecology 1. Species occurrence due to evolutionary past. 2. Mutations and chromosomal rearrangements result in a wide variety of species on earth. 3. Genetic variability can be measured by allozymes or DNA sequencing. 4. Mechanisms for reductions in genetic variability in populations. 生態學 2003 Chap. 2 Genetics and Ecology 3

2. 1 Evolutionary History • Importance of evolutionary ecology to the discipline. • Example: Control of penguins in the Southern Hemisphere vs. their absence in Northern Hemisphere. (企鵝只發現於南半球) – Penguins evolved in the Southern Hemisphere. – Unable to migrate to Northern Hemisphere 生態學 2003 Chap. 2 Genetics and Ecology 4

Evolutionary history • South America, Africa, and Australia – Similar climates (Tropical to temperate) – Characterized by different inhabitants. • South America: Ex. Sloths, anteaters, armadillos, and monkeys with prehensile tails. • Africa: Ex. Antelopes, zebras, giraffes, lions, baboons, okapi, and aardvark. 生態學 2003 Chap. 2 Genetics and Ecology 5

Characterized by different inhabitants • Australia: Ex. No native placental mammals except bats, variety of marsupials, egg-laying montremes, duckbilled platypus, and the echidna. • Best explanation of differences: Evolution. 生態學 2003 Chap. 2 Genetics and Ecology 6

2. 2 Genetic Mutation • Increase in number of species is primarily due to mutation. • Two types of mutation – Gene or point mutation – Chromosome mutation 生態學 2003 Chap. 2 Genetics and Ecology 7

Point mutation • Results from a misprint in DNA copying – Example (Figure 2. 1) • Most changes are caused by frameshift mutations – An addition or deletion in the amino-acid sequence usually leads to drastic and often fatal mutations 生態學 2003 Chap. 2 Genetics and Ecology 8

Direction of transcription DNA AGA TGA RNA UCU ACU GCC AAA CGU Thr Lys Protein Ser CGG Ala TTT GCA Arg Frameshift: Insert T Transition A-G DNA GGA TGA CGG TTT GCA DNA AGT ATG ACG RNA CCU GCC AAA CGU RNA UCA UAC UGC CAA ACG Protein Ser Tyr Protein Pro ACU Thr Ala Lys Arg Cys GTT TGC Glu Thr A. . ? Fig. 2. 1 Types of point mutation. 生態學 2003 Chap. 2 Genetics and Ecology 9

Chromosome mutation • Four types: deletion, duplications, inversions, and translocation (Figure 2. 2) • Deletion – Simple loss of part of a chromosome – Most common source of new genes – Often lethal 生態學 2003 Chap. 2 Genetics and Ecology 10

• Duplication – Arises from chromosomes not being perfectly aligned during crossing over. – Results in one chromosome being deficient and the other one with duplication of genes. – May have advantages due to increased enzyme production. • Inversion – Occurs when a chromosome breaks in two places. When the segment between the two breaks refuses, it does so in reverse order. – Occurs during prophase. 生態學 2003 Chap. 2 Genetics and Ecology 11

Original Breakage A B C D E FG H Altered A BC D E F G H Deletion A B C D E F H Eliminated A B C D E F Duplication From another chromosome F Inversion A B C D E F G G H G E A B G F E DC H D G A B GH C H A B C D E FGH A B C D E T U V O P Q R S TUV O P Q R S F G H Translocation Fig. 2. 2 Chromosome breakage and reunion. 生態學 2003 Chap. 2 Genetics and Ecology 12

Fig. 7. 15 生態學 2003 Chap. 2 Genetics and Ecology 13

Fig. 7. 15 生態學 2003 Chap. 2 Genetics and Ecology 14

Fig. 7. 15 生態學 2003 Chap. 2 Genetics and Ecology 15

2. 3 Measuring Genetic Variability • Genetic diversity is essential to the breeding success of most populations. • Two individuals with the same form of enzyme are genetically identical at that locus. • Variations in gene loci are found through searching for variations in the enzymes (allozymes). • Gel electrophoresis: Technique for determining differences in allozymes. • Example of Gel electrophoresis: Figure 2. 3. 生態學 2003 Chap. 2 Genetics and Ecology 16

Fig. 2. 3 Researcher examines an agarose gel on which samples are separated according to migration rates during the application of an electric current. 生態學 2003 Chap. 2 Genetics and Ecology 17

Gene Sequencing • Another method for assessing variations is the sequence of DNA. • Made possible through the polymerase chain reaction (PCR) technique. • Made possible through the polymerase (cont. ). – Makes millions of copies of a particular region of DNA, thereby amplifying even minute amounts of DNA. 生態學 2003 Chap. 2 Genetics and Ecology 18

DNA amplified • DNA可以經由 polymerase chain reaction (PCR) 被 amplified (increased)。 • 將片斷的DNA與nucleotides 和DNA polymerase混合。DNA polymerase可以促 使DNA複製。 • DNA將會持續複製到nucleotides耗盡。速 度相當快。於幾個小時內，就可以有1, 000 億個copies(DNA)。 (Fig. 8. 3) 教科書：Wallace, R. A. (1997) Biology: the world of life. Addison Wesley Longman, Inc. 生態學 2003 Chap. 2 Genetics and Ecology 19

Fig. 8. 3 DNA片斷 複製增加的方法。經過25個周期，就可 以有1, 000個copies。 教科書：Wallace, R. A. (1997) Biology: the world of life. Addison Wesley Longman, Inc. 生態學 2003 Chap. 2 Genetics and Ecology 20

Mutation • Accelerated through human-made radiation, UV light, or other mutagens. • Rate of occurrence: one per gene locus in every 100, 000 sex cells. Only one out of 1, 000 mutations may be beneficial. • Estimated that only 500 mutations would be expected to transform one species into another. • Rate of mutation is not the chief factor limiting the supply of variability. • Variability is mainly limited by gene recombination and the structural patterns of chromosomes. 生態學 2003 Chap. 2 Genetics and Ecology 21

2. 4 Genetic Diversity and Population Size • Function of population size • Four factors: – inbreeding, – genetic drift, – Neighborhoods, – Effective population size 生態學 2003 Chap. 2 Genetics and Ecology 22

• Mating among close relatives. • Reduced survivorship (Figure 2. 4). • Various types of inbreeding (Figure 2. 5) • inbreeding on juvenile mortality (fig. 2. 6) • inbreeding on small populations (Figure 2. 7). • Greater Prairie Chicken (Figures 2. 8 and 2. 9). Inbreeding Depression 生態學 2003 Chap. 2 Genetics and Ecology 23

Percent 60 50 Non-productive matings 40 Mortality from birth to four weeks 30 20 10 0 1 2 3 4 5 6 Years Fig. 2. 4 inbreeding in rats. 生態學 2003 Chap. 2 Genetics and Ecology 24

Fraction of initial genetic variation 1. 0 • A: exclusive self-fertilization 0. 8 C 0. 6 • B: sibling mating • C: double-first-cousin mating B 0. 4 A 0. 2 0 5 10 15 20 Generations Fig. 2. 5 The decrease in genetic variation is faster 生態學 2003 Chap. 2 Genetics and Ecology 25

% Juvenile mortality- outbred 70 Primates 60 Small Animals 50 40 Saddle back tamarin Ungulates Macaque Chimpanzee Lemur 30 Giraffe 20 10 0 Rat 20 40 Eld’s deer Indian elephant Spider monkey Oryx Mandrill Mouse 100 80 60 % Juvenile mortality-inbred Fig. 2. 6 The effects of inbreeding on juvenile 生態學 2003 Chap. 2 Genetics and Ecology 26

1. 0 N=1000 Fraction of initial genetic variation 0. 9 0. 8 N=300 0. 7 0. 6 N=100 0. 5 N=20 0. 4 0. 3 0. 2 0. 1 0 100 200 300 400 Fig. 2. 7 finite population 生態學 2003 size Chap. 2 Genetics and. Generations Ecology 500 27

hatched 100 75 Eggs hatched (%) 150 Prairie chicken cocks 100 50 50 25 10 Number of prairie chicken cocks Eggs 200 Fig. 2. 9 decrease in hatching of prairie chicken eggs. 0 1973 1980 Year 生態學 2003 Chap. 2 Genetics and Ecology 1990 28

Greater prairie chicken • 1933, population size is 25, 000 • 1962, population size is 2, 000 • 1990, population size is 76 • Less than 50 in 1994 • Prairie chicken habitat was restored in 1970 s and hunting had been banned since the 1940 s. 生態學 2003 Chap. 2 Genetics and Ecology 29

Inbreeding and extinction • Glanville fritillary butterfly (Figure 2. 10) • Exists in numerous small, isolated local populations in meadows where the caterpillars feed on one or two host plants. • Seven of the 42 populations studied became extinct between 1995 and 1996; all seven had a lower population size and genetic variation than the survivors. 生態學 2003 Chap. 2 Genetics and Ecology 30

Genetic Drift • Probability of the failure to mate – Loss of possible rare gene – Loss of genetic information for subsequent generations resulting in a loss of genetic diversity. – Small populations more susceptible to drift. – The rate of loss of original diversity over time is approximately equal to 1/2 N per generation. – Example: N = 500 , then 1/2 N = 0. 001 or 0. 1% genetic diversity lost per generation. – N = 50, then 1/2 N = 0. 01 or 1% genetic diversity lost per generation. 生態學 2003 Chap. 2 Genetics and Ecology 31

Probability of the failure to mate • Over 20 generations, the population of 500 will still retain 98% of the original variation, but the population of 50 will only retain 81. 79%. • 50/500 Rule: Need 50 individuals to prevent excess inbreeding and 500 is the critical size to prevent genetic drift. 生態學 2003 Chap. 2 Genetics and Ecology 32

Genetic drift • Effects of immigration on genetic drift (Figures 2. 11 and 2. 12). • Even the relatively low rate of one immigrant every generation would be sufficient to counter genetic drift in a population of 120 individuals. (Fig. 2. 11) 生態學 2003 Chap. 2 Genetics and Ecology 33

Number of immigrants per generation Percentage of initial genetic variation remaining 100 5 2 1 90 80 0. 5 70 0. 1 60 50 None 10 20 30 40 50 60 70 80 90 100 Generation Fig. 2. 11 The effect of immigration on genetic variation in 25 simulated population of 120 individuals each. Even the low rate of one immigrant per 生態學 2003 Chap. 2 Genetics and Ecology 34

Percentage of populations persisting 100 N = 101 or more 80 N = 51 -100 N =16 -30 60 N = 31 -50 40 N = 15 or less 20 0 10 Fig. 2. 12 20 30 40 50 Time (years) 生態學 2003 Chap. 2 Genetics and Ecology 35

Neighborhoods and Effective Population Size • Effective population size is determined on mating range. • Individuals may only mate within their neighborhood. • Example: Deer mice. 70% of the males and 85% of the females breed within 150 m of their birthplaces. 生態學 2003 Chap. 2 Genetics and Ecology 36

Harem Effects • Even within a neighborhood, some individuals may not reproduce. • In a harem structure, only a few dominant males breed. 生態學 2003 Chap. 2 Genetics and Ecology 37

Effective Population Size • NE = (4 Nm Nf) / (Nm + Nf). • Where: – NE = Effective Population Size; – Nm = Number of Breeding Males; – Nf = Number of Breeding Females. 生態學 2003 Chap. 2 Genetics and Ecology 38

Effective Population Size • A population of 500 with a 50: 50 sex ratio and all individuals breeding. – NE = (4 x 250) / (250+250) = 500 • If 250 females bred with 10 males. – NE = (4 x 10 x 250) / (10 +250) = 38. 5 – Only 7 percent of the actual population size. 生態學 2003 Chap. 2 Genetics and Ecology 39

Applied Ecology Can Cloning help save endangered species? • Dolly, the cloned sheep – Ian Williams 1997 (Photo 1). 1. Need knowledge of reproductive cycle. 2. Need for surrogate females. 3. Expense associated with cloning. 4. Can not address genetic diversity. 生態學 2003 Chap. 2 Genetics and Ecology 40

v 問題與討論！ Japalura@hotmail. com Ayo 台南站： http: //mail. nutn. edu. tw/~hycheng/ 生態學 2003 Chap. 2 Genetics and Ecology 41