Chapter 6Chapter 6Intraspecific variationIntraspecific variation

鄭先祐鄭先祐生態主張者：生態主張者： Ayo Ayo 工作室工作室

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Intraspecific variationIntraspecific variation

Genetic mechanisms that affect variationGenetic mechanisms that affect variation Measuring genetic variation within and Measuring genetic variation within and

among populationsamong populations The interaction of genetic and ecological The interaction of genetic and ecological

process.process. Environmental applicationEnvironmental application

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Intraspecific variationIntraspecific variation

Until recently, direct measurement of the amount of Until recently, direct measurement of the amount of genetic variation in natural populations was difficult.genetic variation in natural populations was difficult.

In the past 20 years, however, the revolution in In the past 20 years, however, the revolution in molecular biology that has transformed much of molecular biology that has transformed much of biology has also had an impact on the study of biology has also had an impact on the study of ecology and evolution.ecology and evolution.

By applying molecular technique, we can now study By applying molecular technique, we can now study the interactions between ecological processes and the interactions between ecological processes and their genetic and evolutionary bases.their genetic and evolutionary bases.

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Genetic mechanisms that affect Genetic mechanisms that affect variationvariation

Ultimately, genetic difference is derived from Ultimately, genetic difference is derived from mutation of the DNA.mutation of the DNA.

A second mechanism that maintains A second mechanism that maintains variations is the phenomenon of heterozygote variations is the phenomenon of heterozygote advantage, or heterosis.advantage, or heterosis.

If the heterozygote has higher fitness than If the heterozygote has higher fitness than either homozygote, the heterozygote class either homozygote, the heterozygote class protects deleterious recessives from protects deleterious recessives from elimination by selection. elimination by selection. 範例：範例： sickle-cell sickle-cell

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Decreasing the genetic variationDecreasing the genetic variation

Genetic drift has the effect of decreasing the Genetic drift has the effect of decreasing the total amount of genetic variation in a total amount of genetic variation in a population.population.

Inbreeding also affects variation. The major Inbreeding also affects variation. The major genetic effect of inbreeding is an increase in genetic effect of inbreeding is an increase in homozygosity.homozygosity.

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Inbreeding Inbreeding 的影響的影響 (p2 + 2pg + q2) =1.0(p2 + 2pg + q2) =1.0 (p2 + Fpq) + 2pq(1 - F) + (q2 + Fpg) =1.0(p2 + Fpq) + 2pq(1 - F) + (q2 + Fpg) =1.0

– Where F is the inbreeding coefficient.Where F is the inbreeding coefficient. 基因組成 基因組成 p p 和 和 q q 所佔的比率不變。所佔的比率不變。 ((p2 + Fpq) + (1/2) (2pq)(1-F) = p(p + q) = pp2 + Fpq) + (1/2) (2pq)(1-F) = p(p + q) = p Homozygosity increases and heterozygosity Homozygosity increases and heterozygosity

decreases, alleles are exposed more directly decreases, alleles are exposed more directly to selection, and this can lead to a decrease in to selection, and this can lead to a decrease in genotypic variation. (Fig. 6.2)genotypic variation. (Fig. 6.2)

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Measuring genetic variation Measuring genetic variation within and among populationswithin and among populations

Morphological Morphological variationvariation

2001生態學 10地理變異的範例一地理變異的範例一

農耕地

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This significant increase in growth This significant increase in growth rate in the ab suggests that growth rate in the ab suggests that growth

rate it plastic.rate it plastic.

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地理變異的地理變異的範例二範例二

位於高山的，比較低矮。

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Plants from the high-altitude population(timberline) remain Plants from the high-altitude population(timberline) remain short in stature regardless of where they were grown.short in stature regardless of where they were grown.

On the other hand, the lower-elevation populations exhibit On the other hand, the lower-elevation populations exhibit some plasticity in growth, they are dwarfed at high elevation.some plasticity in growth, they are dwarfed at high elevation.

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Interaction of genetic and Interaction of genetic and phenotypic responsephenotypic response

範例：範例： Intertidal snail, Intertidal snail, LittoriaLittoria obtusataobtusata. . – 生活於浪大的地區，和浪小的地區。生活於浪大的地區，和浪小的地區。– 是否會被浪捲下去，取決於是否會被浪捲下去，取決於 shell size and shell size and

shapeshape ，，以及以及 the strength of the footthe strength of the foot 。。– 於浪大的地區生活的於浪大的地區生活的 snail snail ，，都有較大的都有較大的

footfoot 。。 Trussell (1997) Trussell (1997) 將生活在不同浪大小地區的將生活在不同浪大小地區的

snail snail 交換。交換。 (( 野外，且於實驗室內模擬野外，且於實驗室內模擬 )) 。。– 浪小地區生活的浪小地區生活的 snailsnail 轉換至浪大地區，其轉換至浪大地區，其 foot foot

會轉變大。但是相反的轉換，卻不會縮小。會轉變大。但是相反的轉換，卻不會縮小。

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有變異，未必然就有基因上的意義有變異，未必然就有基因上的意義 有型態特徵的變異，未必然就有基因上的基礎。有型態特徵的變異，未必然就有基因上的基礎。 譬如：譬如： seed size is clearly an important component seed size is clearly an important component

of the reproductive strategy, we cannot necessarily of the reproductive strategy, we cannot necessarily assume that seed size is under simple genetic control assume that seed size is under simple genetic control such that it can be modified by natural selection. such that it can be modified by natural selection. (Wolfe, 1995)(Wolfe, 1995)

In the biennial plant in which seed size varies by at In the biennial plant in which seed size varies by at least a factor of 2, Wolfe found that there is no least a factor of 2, Wolfe found that there is no variation on which natural selection can act to variation on which natural selection can act to modify seed size. The seed size is affected by the modify seed size. The seed size is affected by the light regime.light regime.

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Chromosomal Chromosomal variationvariation

There is There is considerable considerable geographic geographic variation in variation in distribution of the distribution of the chromosome types chromosome types of of 果蠅 果蠅 D. D. psydoobscurapsydoobscura..

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The white-footed The white-footed mouse can be mouse can be

divided into two divided into two chromosomal chromosomal

races, races, distinguishable on distinguishable on

the basis of G-the basis of G-banded banded

karyotypes. It do karyotypes. It do not show clines in not show clines in

chromosome chromosome types.types.

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AllozymesAllozymes

Protein electrophoresis has been used extensively to measure genetic variation.

One advantage is that a large number of loci can be sampled

Furthermore, we are measuring variation at the level of the cell’s proteins – one step closer to the DNA.

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Fig. 6.8 Frequencies of polymorphisms for different taxonomic Fig. 6.8 Frequencies of polymorphisms for different taxonomic groups.groups.

硬骨魚類

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Fig. 6.8 Frequencies of polymorphisms for different taxonomic Fig. 6.8 Frequencies of polymorphisms for different taxonomic groups. Bars represent the number of species in the group with that groups. Bars represent the number of species in the group with that

level of polymorphism for electrophoretic alleles.level of polymorphism for electrophoretic alleles.

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Fig. 6.8 Frequencies of polymorphisms for different taxonomic Fig. 6.8 Frequencies of polymorphisms for different taxonomic groups. Bars represent the number of species in the group with that groups. Bars represent the number of species in the group with that

level of polymorphism for electrophoretic alleles.level of polymorphism for electrophoretic alleles.

2001生態學 23Fig. 6.9 percent heterozygosity per individual (H)Fig. 6.9 percent heterozygosity per individual (H)

2001生態學 24Fig. 6.9 percent heterozygosity per individual (H)Fig. 6.9 percent heterozygosity per individual (H)

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Fig. 6.9 Frequencies of heterozygosity values for different Fig. 6.9 Frequencies of heterozygosity values for different taxonomic groups. Bar represent the number of species in taxonomic groups. Bar represent the number of species in

the group with that proportion of heterozygous alleles.the group with that proportion of heterozygous alleles.

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• Genetic similarity Genetic similarity

IINN = = (p (pixix p piyiy) / ) / ( (ppixix22)()(ppiyiy

22))

• genetic distance genetic distance

Dn = - ln IDn = - ln INN

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FFItIt = F = FSTST + (1-F + (1-FSTST) F) FISIS

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FFST ST ( variance among groups)( variance among groups)

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DNA fingerprintingDNA fingerprinting

DNA fingerprinting has recently emerged as an DNA fingerprinting has recently emerged as an additional technique of genetic analysis that holds additional technique of genetic analysis that holds great promise for ecological genetics.great promise for ecological genetics.

This technique is based on the present in DNA of so-This technique is based on the present in DNA of so-called minisatellites, hypervariable regions that are called minisatellites, hypervariable regions that are composed of short segments containing multiple composed of short segments containing multiple copies of a short sequence.copies of a short sequence.

It is thought that minisatellites are noncoding It is thought that minisatellites are noncoding regions.regions.

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Fig. 6.12 The process of DNA fingerprintingFig. 6.12 The process of DNA fingerprinting (a) DNA is isolated from cells and cleaved at specific sites (a) DNA is isolated from cells and cleaved at specific sites with an endonuclease.with an endonuclease.(b) The sample containing DNA fragments from each (b) The sample containing DNA fragments from each individual is placed in an elctrophoresis gel.individual is placed in an elctrophoresis gel.

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© © The DNA fragments are then denatured into single-The DNA fragments are then denatured into single-stranded segments and transferred to a nylon or nitrocellulose stranded segments and transferred to a nylon or nitrocellulose membrane by a Southern transfer.membrane by a Southern transfer.(e) A piece of X-ray film is placed over the membrane and (e) A piece of X-ray film is placed over the membrane and exposed.exposed.

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Michondrial DNAMichondrial DNA

Population biologists have also made use of Population biologists have also made use of unique properties of mitochondrial DNA to unique properties of mitochondrial DNA to measure genetic variation in natural measure genetic variation in natural populations.populations.

Mitochondria contain a small set of genes that Mitochondria contain a small set of genes that are separate from the nuclear genes and thus are separate from the nuclear genes and thus do not undergo segregation at meiosis.do not undergo segregation at meiosis.

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The interaction of genetic and The interaction of genetic and ecological processesecological processes

Three fundamental interactions that affect Three fundamental interactions that affect variationvariation ：：

Selection Selection DispersalDispersal Population sizePopulation size

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A classic exampleA classic exampleland snail, land snail, Cepaea nemaralisCepaea nemaralis

The Intraspecific The Intraspecific variation of the land variation of the land snail is a product of snail is a product of selection for color selection for color matching to avoid matching to avoid predation.predation.

Colors of the shells Colors of the shells show great variety, show great variety, ranging from brown to ranging from brown to yellow to pink, and the yellow to pink, and the degree of banding also degree of banding also varies greatly.varies greatly.

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A strong A strong association between association between

particular shell particular shell patterns and certain patterns and certain

habitat types.habitat types.

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EcotypesEcotypes

Geographic variants that result from Geographic variants that result from adaptation to local conditions are called adaptation to local conditions are called ecotypes.ecotypes.

範例： 範例： tickle grass tickle grass (Agrostis(Agrostis scabrascabra) grow at ) grow at several sites near Sudbury, Ontrario, that are several sites near Sudbury, Ontrario, that are contaminated by heavy metals.contaminated by heavy metals.

Plants from contaminated sites show higher Plants from contaminated sites show higher tolerance of heavy metals. (Fig. 6.15)tolerance of heavy metals. (Fig. 6.15)

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Seed germination Seed germination and root growth in and root growth in

the presence of the presence of heavy metals was heavy metals was

higher in plants from higher in plants from contaminated sites contaminated sites than in plants from than in plants from

uncontaminated sitesuncontaminated sites

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範例：範例： The wild oat, The wild oat, AvenaAvena barbatabarbata

Two electrophoretic genotypes associated Two electrophoretic genotypes associated with extreme mesic or xeric sites.with extreme mesic or xeric sites.

Each genotype is based on the allozymes Each genotype is based on the allozymes present at five loci.present at five loci.

The mesic and xeric ecotypes can occur on a The mesic and xeric ecotypes can occur on a much smaller geographic scale (Table 6.6).much smaller geographic scale (Table 6.6).

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The wild oat, The wild oat, AvenaAvena barbatabarbata

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DispersalDispersal 範例：範例： monarch butterfly (nonmigratory and monarch butterfly (nonmigratory and

migratory populations)migratory populations) FFST ST ( variance among groups)( variance among groups)

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範例：範例： Pocket gopher Pocket gopher (Thomomys bottae(Thomomys bottae))

The mean values The mean values of Fof FSTST are are

significant and are significant and are considerable considerable larger than those larger than those for migratory for migratory butterflies.butterflies.

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範例：範例： white-white-footed mousefooted mouse

Ravines (Ravines ( 深谷深谷 ) ) and and power line rights-of-way power line rights-of-way dissecting forest habitat dissecting forest habitat act as barriers to dispersal act as barriers to dispersal in the white-footed in the white-footed mouse, a forest-dwelling mouse, a forest-dwelling mammal.mammal.

(Table 6.8)(Table 6.8)

2001生態學 44FFST ST ( variance among groups)( variance among groups)

2001生態學 45FFST ST ( variance among groups)( variance among groups)

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範例：範例： A perennial plant, the A perennial plant, the blazing starblazing star (Liatris cylindracea(Liatris cylindracea))

Exhibits genetic subdivision on an extremely fine Exhibits genetic subdivision on an extremely fine spatial scale.spatial scale.

The entire population occupied only 600 square The entire population occupied only 600 square meters.meters.

It was quite dense– as many as 175 plants per square It was quite dense– as many as 175 plants per square meter.meter.

The study population was divided into a series of 66 The study population was divided into a series of 66 quadrates, each 3 meters square. quadrates, each 3 meters square.

Plants were sampled from these quadrates, and 27 Plants were sampled from these quadrates, and 27 allozymes were analyzed for each plant.allozymes were analyzed for each plant.

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The variance among subpopulations The variance among subpopulations was significant. The values of FST, was significant. The values of FST,

measured on a scale of only 600 measured on a scale of only 600 square meters,were greater than square meters,were greater than those of the monarch butterfly those of the monarch butterfly

measured across all of eastern North measured across all of eastern North American.American.

Why?

Two factors result in extremely small dispersal distances: pollinator behavior and seed dispersal distances.

blazing starblazing star

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blazing starblazing star

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範例：範例： seed dispersal seed dispersal mechanism of three species of mechanism of three species of

forest herbsforest herbs Sanicular seeds Sanicular seeds

attach easily and attach easily and tighly to tighly to mammalian furmammalian fur

Cryptotaenia seeds Cryptotaenia seeds fall relatively near fall relatively near the parent plantthe parent plant

Osmorhiza seeds Osmorhiza seeds are intermediate.are intermediate.

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種子可散播最種子可散播最遠的，其遠的，其genetic distance genetic distance 最低。最低。

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範例：範例： the mangrove the mangrove (Avicennia marina)(Avicennia marina)

The potential for long-The potential for long-distance seed dispersal.distance seed dispersal.

This plant produces This plant produces seeds that germinate on seeds that germinate on the tree and fall into the the tree and fall into the water where tides and water where tides and currents disperse the currents disperse the seeds, potentially for seeds, potentially for great distances.great distances.

紅樹林

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Genetic structuring in Genetic structuring in the Indo-West Pacific the Indo-West Pacific

is characterized by is characterized by sharp discontinuities in sharp discontinuities in

allele frequencies.allele frequencies.

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紅樹林的紅樹林的基因循流基因循流

途徑途徑

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範例：範例： sugar maples sugar maples (Acer saccharum(Acer saccharum))

The genetic structure of populations in The genetic structure of populations in patches of forest differs from the pattern in patches of forest differs from the pattern in populations in large tracts of forest.populations in large tracts of forest.

結果與原本的預期，結果與原本的預期， Patch populations Patch populations showed more genotypic variation than did showed more genotypic variation than did large tracts of forest.large tracts of forest. ，，相反。相反。

研究者的解釋：研究者的解釋： the patches of forest are the patches of forest are subject to increased immigrant pollen and subject to increased immigrant pollen and hence gene flow.hence gene flow.

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於密度較低的樹林地，其於密度較低的樹林地，其接觸外來花粉的機會較大。接觸外來花粉的機會較大。

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Population sizePopulation size 範例：範例： California vole, a four-year cycle.California vole, a four-year cycle.

During the peak of the population cycle, when dispersal and extensive gene flow have homogenized the population, FST is low.

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Small populations and extinctionSmall populations and extinction

The small populations may be subject to loss The small populations may be subject to loss of genetic variation by drift or inbreeding.of genetic variation by drift or inbreeding.

Isolated populations may not have sufficient Isolated populations may not have sufficient gene glow to maintain genetic variation.gene glow to maintain genetic variation.

The loss of variation has three main The loss of variation has three main detrimental effects:detrimental effects:– 1. 1. 對環境變動的適應潛能下降對環境變動的適應潛能下降– 2. 2. Inbreeding depression.Inbreeding depression.– 3. Fixation of new deleterious mutations.3. Fixation of new deleterious mutations.

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範例：受到人為影響的生物範例：受到人為影響的生物marsh gentian (marsh gentian ( 植物植物 ))

In the Netherlands, this species was once common, but In the Netherlands, this species was once common, but pollution of the soil and habitat loss have resulted in pollution of the soil and habitat loss have resulted in significant population declines.significant population declines.

Raijman and colleagues (1994) examined allozymes from Raijman and colleagues (1994) examined allozymes from populations ranging from 1 to more than 50,000 populations ranging from 1 to more than 50,000 individuals, they discovered that most of the populations individuals, they discovered that most of the populations did not contain any rare alleles, a result that suggests an did not contain any rare alleles, a result that suggests an overall loss of variation.overall loss of variation.

The number of polymorphic loci and the average number The number of polymorphic loci and the average number of alleles per locus were positively correlated with of alleles per locus were positively correlated with population size, confirming the loss of variation in small population size, confirming the loss of variation in small populations.populations.

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Fig. 6.24 genetic variation and population size in Fig. 6.24 genetic variation and population size in GentianaGentiana. . (a) proportion of polymorphic loci (a) proportion of polymorphic loci

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Fig. 6.24 genetic variation and population size in Fig. 6.24 genetic variation and population size in GentianaGentiana. . (b) mean number of alleles per locus (b) mean number of alleles per locus

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範例：範例： The northern elephant sealThe northern elephant seal( bottleneck effect )( bottleneck effect )

One of the most extreme examples of the One of the most extreme examples of the effects of very small population size on effects of very small population size on genetic variation.genetic variation.

This species was hunted nearly to extinction This species was hunted nearly to extinction in the 19th century – the population was in the 19th century – the population was reduced to only about 20 individuals.reduced to only about 20 individuals.

Although the species had recovered to more Although the species had recovered to more than 30,000 individuals by the middle of 20th than 30,000 individuals by the middle of 20th century, there was no genetic variation at any century, there was no genetic variation at any of 24-electrophoretic loci analyzed. of 24-electrophoretic loci analyzed.

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範例：範例： the gray wolf the gray wolf ( Canis lupus( Canis lupus)) and the coyote and the coyote ( C. latrans( C. latrans))

Restriction analysis of mtDNA indicates that eh Restriction analysis of mtDNA indicates that eh continent-wide coyote population is composed of a continent-wide coyote population is composed of a larger number of genotypes (32) than is the wolf larger number of genotypes (32) than is the wolf population (18).population (18).

Coyote populations are not highly genetically Coyote populations are not highly genetically differentiated; their Fdifferentiated; their FST ST values were not significantly values were not significantly different from zero.different from zero.

FFSTST values for the wolf, however, were large (0.76) values for the wolf, however, were large (0.76) and highly significant, which indicates that the and highly significant, which indicates that the North American population is highly subdivided into North American population is highly subdivided into significantly different subpopulations.significantly different subpopulations.

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範例：範例： The wild turkey The wild turkey ( Meleagris gallopavo )( Meleagris gallopavo )

The wild turkey populations were drastically reduced The wild turkey populations were drastically reduced by the clearing of forest land in the eastern US in the by the clearing of forest land in the eastern US in the 1919thth and 20 and 20thth centuries. centuries.

By the 1940s, the eastern populations had been By the 1940s, the eastern populations had been extirpated from more than 80% of their original range.extirpated from more than 80% of their original range.

The remaining populations inhabit a highly fragmented The remaining populations inhabit a highly fragmented forest landscape.forest landscape.

An electrophoretic survey of turkeys revealed An electrophoretic survey of turkeys revealed extremely high Fextremely high FSTST values. values.

The mean FThe mean FSTST value of 0.102 is one of the highest value of 0.102 is one of the highest reported for any avian populations.reported for any avian populations.

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範例：範例： heath hens (prairie heath hens (prairie chicken)chicken)

( ( Tympanuchus cupido Tympanuchus cupido )) Bouzat et al. (1998) extracted and analyzed Bouzat et al. (1998) extracted and analyzed

DNA from the feather roots of museum DNA from the feather roots of museum specimens of this species collected before the specimens of this species collected before the population reduction.population reduction.

These researchers used a relative new These researchers used a relative new technique of genetic analysis, microsatellite technique of genetic analysis, microsatellite DNA, to measure genetic variation.DNA, to measure genetic variation.

This technique is similar to DNA This technique is similar to DNA fingerprinting using minisatellite DNA.fingerprinting using minisatellite DNA.

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粗體字，代表於 粗體字，代表於 museum specimensmuseum specimens 有有，，但於但於 Illinois Illinois populations populations 沒有的 沒有的 alleleallele 。 。 斜體字，代表只有斜體字，代表只有 museum museum

specimens specimens 才有的特殊 才有的特殊 alleleallele 。。The museum specimens contained nine alleles not currently The museum specimens contained nine alleles not currently

present in the Illinois populations.present in the Illinois populations.

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範例：範例： the cheetah the cheetah ((Acinonyx jubatusAcinonyx jubatus))

O’Brien and colleagues (1983) surveyed 47 allozyme O’Brien and colleagues (1983) surveyed 47 allozyme systems in samples from populations form South systems in samples from populations form South Africa, they found that the 55 cheetahs in their Africa, they found that the 55 cheetahs in their samples were monomorphic for all 47 allozymes.samples were monomorphic for all 47 allozymes.

Such extreme genetic uniformity has been found to Such extreme genetic uniformity has been found to include the major histocompatibility complex (MHC).include the major histocompatibility complex (MHC).

This situation makes the cheetah extremely This situation makes the cheetah extremely vulnerable to disease or to a change in the vulnerable to disease or to a change in the environment that would require selection to operate.environment that would require selection to operate.

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Environmental applicationEnvironmental application

Subspecies, races, and the Subspecies, races, and the endangered species Act.endangered species Act.

In 1973 the US congress passed a piece of landmark In 1973 the US congress passed a piece of landmark conservation legislation, the endangered species Act.conservation legislation, the endangered species Act.

This legislation mandated that the Fish and Wildlife This legislation mandated that the Fish and Wildlife Service determine which species in the US are at Service determine which species in the US are at risk of extinction.risk of extinction.

When a species is determined to be endangered, the When a species is determined to be endangered, the government is required not only to protect the government is required not only to protect the remaining individuals but also to develop and remaining individuals but also to develop and implement a recovery plan designed to move the implement a recovery plan designed to move the species from the brink of extinction.species from the brink of extinction.

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保護的範圍包含亞種，甚至是族群保護的範圍包含亞種，甚至是族群 In addition, the Endangered Species Act In addition, the Endangered Species Act

recognizes the importance of protecting recognizes the importance of protecting distinct subspecies, and even populations, in distinct subspecies, and even populations, in order to maintain the naturally occurring order to maintain the naturally occurring genetic diversity so important to species genetic diversity so important to species survival.survival.

This requirement has led to some practical This requirement has led to some practical problems in the implementation of the act.problems in the implementation of the act.

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範例：範例： a unique subspecies of the mountain a unique subspecies of the mountain lion lion (Filis concolor coryi)(Filis concolor coryi)

Once occupied Once occupied much of the much of the southeastern southeastern US.US.

Today this subspecies, is critically endangered. Today this subspecies, is critically endangered. Less than 40 individuals remain in the swamps of southern Florida.Less than 40 individuals remain in the swamps of southern Florida. Recent genetic analysis has revealed that the subspecies is Recent genetic analysis has revealed that the subspecies is

contaminated with genes from a South American subspecies, a few contaminated with genes from a South American subspecies, a few individuals of which were released in the late 1950s or 1960s.individuals of which were released in the late 1950s or 1960s.

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範例：範例： the gray wolf the gray wolf (Canis lupus)(Canis lupus)

Recent genetic analyses of this species have Recent genetic analyses of this species have shown that it is contaminated by genes from shown that it is contaminated by genes from coytes (coytes ( Canis latrans Canis latrans).).

These closely related species have very These closely related species have very different ecological niches, but matings different ecological niches, but matings between them can produce viable, fertile between them can produce viable, fertile hybrids.hybrids.

因為環境的開發，因為環境的開發， gray wolf gray wolf 和 和 coytescoytes 混混交持續增加。 → 是否要從保育類排除？交持續增加。 → 是否要從保育類排除？

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