Chap.02 The Evolution of Behavior

鄭先祐 (Ayo) 教授國立台南大學 環境與生態學院

生態科學與技術學系 環境生態研究所 + 生態旅遊研究所

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The Evolution of Behavior

Artificial selectionNatural selectionBehavioral geneticsThe modern theoretical framework

for animal behavior Sociobiology and selfish genes Antipredator behavior in guppies

AdaptationGenetic techniquesphylogeny

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Both natural and artificial selection have produced many morphological varieties of the pigeon.

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Pigeon breeders have selected for behavioral varieties of pigeons, including (A) tumbler ( 輾轉的 ) pigeons, and (B) homing pigeons.

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If hunting in larger groups (up to some maximum group size) provides more food per dog than hunting in smaller groups (or alone), natural selection can favor group hunting.

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When population size equals 100, the number of wild dogs that hunt in groups will increase in frequency, and they will eventually make up 100 percent of the population. No mutation and no migration.

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Heritability ( 遺傳度 )

Selection differential, S Generation 1 天擇下，可繁殖後代的平均值 (X1)

扣除 目前世代的平均值 (X0) 。 譬如， X0 =60 秒 X1=90 秒 S=90-60=30

Response, R Generation 2 的平均值 (X2) 扣除 Generation 1 的

平均值 (X0) 。 譬如， X2=70 秒 R=70-60=10

Heritability, h2 h2 = R/S = 10/30 = 0.33

形態和行為 h2 = Low 0.0-0.1 ， moderate 0.1-0.4

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Behavioral genetics

1. Using Mendel’s laws of genetics to predict the distribution of behavioral phenotypes

2. Mapping genes for behavioral traits3. Using other measures of heritability

to determine what percentage of the variation in a behavioral trait is genetic and what percentage is environmental.

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Some of differences in the mating behavior of (A) satellite males and (B) independent males are controlled by a single gene with two alleles labeled S and s. The S allele is dominant and codes for satellite male behavior, while the s allele is recessive. The ss is for independent males.

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Polygenic traits

Quantitative trait loci (QTLs)Fear/fearlessness in mice (Flint, et al.,

1995)測試 mice 於 open-field behavior (fear)選擇 the more fearfull mice, 分析其 DNA相關 fear 的基因存在於， six different

chromosomes (1,4,12,15,17 和 18) 。倘若是走迷宮的 fear ，則存在於

chromosomes (1,12, 和 15) 。

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Dissecting behavioral variation

• Parent-offspring regression

• Breeding colony size in parents and offspring (Fig.2.11)

• Cross-fostering experiment

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The modern theoretical framework for animal behavior

Antipredator behavior in guppies (A) an upstream,

low-predation stream, and

(B) a downstream, high-predation stream.

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Male

Female

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(A)A pike cichlid, Crenicichia alta. These predators are common in downstream sites native to guppies.

(B) A killifish, Rivulus hartii. These small, fairly innocuous predators can eat only tiny guppies and are found in upstream sites.

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(A)Group size where there is low-predation pressure leads to a preference for small groups.

(B)Group size where there is medium to high predation pressure.

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(C) Groups size where there is very-high predation pressure leads to a preference for larger group sizes.

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Over the courses of several years, transplanted populations converge on the characteristics of the fish in the populations into which they were transplanted.

Here, some guppies from high-predation sites are transplanted to low-predation sites, and vice versa.

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Adaptation

In more than 100 different species of birds, females engage in brood parasitism.

While waterfowl make up only about 2 percent of bird species, they account for more than 25 percent of the cases of parasitic egg dumping.

Semel and Sherman found that a remarkable 95% of active nests were parasitized, despite many empty nest boxes that could be used to raise young. Wood ducks that nest in man-made boxes in

Missouri Many heavily parasitized nests were simply

abandoned by the wood ducks, and no eggs in such nests hatched.

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(A)A male and female wood duck at a man-made nesting box.

(B) many different wood ducks lay their eggs in the same nest.

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Five hypotheses

1. Dump eggs to reduce the risk of predation on all their eggs at once, thereby engaging in what is called “bet hedging”.

2. Be forced to parasitize the nests of others for lack of suitable, hidden nests.

3. Parasitze when their own nest is destroyed4. Gain some benefit by placing eggs in the nests

of genetic relatives.5. Enhance their reproductive success in general

by simply laying eggs in any available nest they come across.

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Maladaptations

When nest boxes were not present and good territories were dispersed throughout the environment, there was likely a very high premium placed on finding good cavities in which to nest.

Thus, females may have egg dumped in such cavities, and they may have benefited from such parasitism.

But when nest boxes were present and clumped, such egg dumping was no longer adaptive. (Fig. 2.21)

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Kinship and naked mole rat behaviorGenetic techniques to test hypotheses in animal behavior

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35( 結盟 )

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Phylogeny and the study of animal behavior

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Phylogenetic trees

Phylogenetic trees Homology( 同源 ) vs. homoplasy ( 同功 ) Convergent evolution （趨同演化） Polarity 　（極向）

Parsimony analysis（吝嗇分析）

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Phylogeny and parental care

Ray-finned fish ( 硬骨魚類 ) There are of families, mad up of over

20,000 species. High variety of parental care

To build a phylogenetic tree of 224 families of ray-finned fish and examined the evidence for parental care. (Mank et al, 2005)

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Phylogeny and parental care

1. Fish paternal care evolved on 21 independent occasions.

2. Maternal care and biparental care also evolved independently numerous times.

3. Maternal care tended to evolve after species had moved from external to internal fertilization.

4. Paternal care was often found alongside intense male coloration and nest construction (external fertilization)

5. Male coloration was also associated with systems in which females fertilized eggs internally.

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Phylogeny, mating systems, and male aggression

Male fighting one another for access to females, since the payoff for such aggression.

If sexually receptive females are not present, the costs of males fighting one another may outweigh the benefits.

Wasps of the genus Nosonia lay their eggs inside a host species, and their larvae feed on the host as they develop.

Three species of Nasonia, N. vitripennis., N. giraulti and N. libgucirnus.

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Ayo NUTN website:http://myweb.nutn.edu.tw/~hycheng/

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