chapter 5 life history strategies © 2002 by prentice hall, inc. upper saddle river, nj 07458...
Post on 22-Dec-2015
223 views
TRANSCRIPT
Chapter 5Life History Strategies
© 2002 by Prentice Hall, Inc.
Upper Saddle River, NJ 07458
生活史策略
#2Chapt. 05
Outline• Reproductive strategies
– Species that reproduce throughout their lifetimes (iteroparous 反覆生殖 )
– Species that reproduce just once (semelparous 單次生殖 )
#3Chapt. 05
Outline• Age structure
– Growing populations– Declining populations
• Classification of mating systems
#4Chapt. 05
Outline• Continuum of life history
strategies– r-selected– K-selected– Carrying capacity 承載量
#5Chapt. 05
Life history strategiesFundamental aspects:
1. Size體型:2. Metamorphosis變態;3. Diapause滯育;4. Senescence衰老;5. Reproductive patterns繁殖模式;
#6Chapt. 05
Life history strategiesFundamental aspects:
1. Size體型: The mass and dimensions typical of adult individuals of a species.
2. Metamorphosis變態;3. Diapause滯育;4. Senescence衰老;5. Reproductive patterns繁殖模式;
#7Chapt. 05
The effects of body size.
體型體表面積附肢
比例
食物、代謝、運動能力
#8Chapt. 05
Life history strategiesFundamental aspects:1. Size體型:2. Metamorphosis變態; The presence of a major developmental change in shape of form from the juvenile to the adult.
3. Diapause滯育;4. Senescence衰老;5. Reproductive patterns繁殖模式;
#9Chapt. 05
Life history strategiesFundamental aspects:1. Size體型:2. Metamorphosis變態;3. Diapause滯育; The present of a resting stage in the life history.4. Senescence衰老;5. Reproductive patterns繁殖模式;
#10Chapt. 05
Life history strategiesFundamental aspects:1. Size體型:2. Metamorphosis變態;3. Diapause滯育;4. Senescence衰老; The process and timing of aging, degeneration, and death.5. Reproductive patterns繁殖模式;
#11Chapt. 05
Senescence衰老
#12Chapt. 05
Life history strategiesFundamental aspects:1. Size體型:2. Metamorphosis變態;3. Diapause滯育;4. Senescence衰老;5. Reproductive patterns繁殖模式; The magnitude and timing of reproductive events (clutch size, age at reproductive maturity, size of young, number of reproductive events in a life time, amount of parental investment and care, and the like).
#13Chapt. 05
Reproductive power is limited by two processes:
1. The acquisition of energy, which increases with mass raised to the 0.75power.
2. The rate of conversion of energy to offspring, which changes as a function of mass to the –0.25 power.
#14Chapt. 05
Reproductive Strategies• Semelparity
– Organisms that produce all of their offspring in a single reproductive event.
– May live several years before reproducing or lifespan is one year (ex. Annual plants)
#15Chapt. 05
Reproductive Strategies• Semelparity (cont.).
– Ex. Figure 5.1.
#16Chapt. 05
Reproductive Strategies• Iteroparity
– Organisms that reproduce in successive years or breeding seasons
– Variation in the number of clutches and number of offspring per clutch.
#17Chapt. 05
Reproductive Strategies• Iteroparity (cont.).
– Some species have distinct breeding seasons•Ex. Temperate birds and temperate
forest trees•Lead to distinct generations
#18Chapt. 05
Reproductive Strategies• Iteroparity (cont.).
– Some species reproduce repeatedly and at any time during the year (continuous iteroparity)•Ex. Some tropical species, many
parasites, and humans
#19Chapt. 05
Reproductive Strategies• Environmental Uncertainty
– Favors iteroparity– Survival of juveniles is poor and
unpredictable– Selection favors
•Repeated reproduction•Long reproductive life
#20Chapt. 05
Reproductive Strategies• Environmental Uncertainty
•Spread the risk over a longer period (“bet hedging”)
• Environmental Stable– Favors semelparity
#21Chapt. 05
Reproductive Strategies• Environmental Stable (cont).
– More energy can be devoted to seed production rather than maintenance
– Annuals rely on seed storage during environmentally unstable years
#22Chapt. 05
洄游性鮭魚的產卵策略
陸封型鮭魚的產卵策略又如何?
#23Chapt. 05
Age Structure• Semelparous organisms
– Often produce groups of same-aged young – cohorts
– Cohorts grow at similar rates
• Iteroparous organisms– Many young at different ages
#24Chapt. 05
Age Structure• Increasing populations – large
number of young• Decreasing populations – few
young– Loss of age classes
• Influence on population
#25Chapt. 05
Age Structure– Loss of age classes (cont.).
• Ex. Overexploited fish populations – older age classes
– Reproductive age classes removed– Reproductive failure– Results in population collapse
• Ex. Younger age classes, deer removing young trees
– Figure 5.2
#26Chapt. 05
20
40
60
20
40
60
(a) Age distribution in an undisturbed forest
(b) Age distribution skewed toward adults where overgrazing has reduced the abundanceof young trees
10 20 30 40 50 60 70
Age (years)
Perc
ent
of
trees
#27Chapt. 05
Mating Systems• Sex ratio
– Applied ecology•Hunters prefer deer populations
dominated by males•Effects of too many males on population
growth– Analysis of the ratio
#28Chapt. 05
Mating Systems•Why is the sex ratio usually 1:1?
– Aren’t males superfluous?– Answer: Selfish genes!
» Populations – predominately female
» Populations – predominately male
» Over time, sex ratio would be kept at 1:1
• Selection would favor sons
• Selection would favor daughters
#29Chapt. 05
Mating Systems– Exception to 1:1
•One male dominates in breeding•Occurs in species with
– Low powers of dispersal– Inbreeding is frequent
#30Chapt. 05
Mating Systems•Ex. The parasitic Hymenoptera
– Females mate once and store sperm– Females control sex ratio
» Use sperm to create females» Without sperm to create males
– Process termed haplodiploid
•Ex. The mite Acarophenox (Figure 5.3)
#31Chapt. 05
Mating Systems• Mating systems in animals
– Monogamy•Exclusive mating•Common among birds (~90%) of
species
#32Chapt. 05
Mating Systems– Polygamy
• Individuals mate with multiple partners•Polygyny
– One male mates with multiple females– Females mate with one male
#33Chapt. 05
Mating Systems•Polyandry
– One female mates with multiple males– Males mate with one female
– Polygyny•Females must care for the young•Mammals tend to be polygynous
– Ex. Figure 5.4
#34Chapt. 05
Mating Systems– Polygyny (cont.).
• Influenced by spatial and temporal distribution of females
– Monogamous relationships result from all females becoming sexually receptive at the same time
– Female receptiveness spread over weeks or months – polygyny can result
#35Chapt. 05
Mating Systems•Resource-based polygyny
– Critical resource is patchily distributed or in short supply
– Male can dominate resource and breed with more than one visiting female
– Disadvantages for the female» Must share resources» More females means less success» Figure 5.5
#36Chapt. 05
Number of females per group
1 2 3 4 5 6
1
2
3
4
5
Num
ber
of
yearl
ings
per
male
( )
Num
ber
of
yearl
ings
per
fem
ale
( )
0.5
0.75
1.0
1.25
#37Chapt. 05
Mating Systems•Non-resource based polygyny
– Harem-based» Common in groups or herds» Protection from predators» Harem master does not remain for long
– Communal courting areas – leks» Figure 5.6
#38Chapt. 05
Mating Systems– Polyandry
•Practiced by a few species of birds•Ex. Spotted sandpiper in the Arctic
tundra– Reproductive success not limited by food– Limited by the number of males needed to
incubate eggs.
•Ex. American jacana (Figure 5.7)
#39Chapt. 05
Life History Strategies
• Success of populations– Reproductive strategies– Survival strategies– Habitat usage– Competition with other organisms
#40Chapt. 05
Life History Strategies
– K-Selected•Populations increase slowly toward the
carrying capacity • (K) of the environment•Low reproductive allocations• Iteroparous•High competitive abilities
#41Chapt. 05
Life History Strategies
•Ex. Mature forest– Non-disturbed habitat– Grow slowly– Reach reproductive age late– Devote large amounts of energy to growth
and maintenance
#42Chapt. 05
Life History Strategies
•Ex. Mature forest (cont.).– Grow to large sizes and shade-out r-selected
species– Long-lived and produce seeds repeatedly
every year while mature– Seeds are bigger than r-selected species –
provide food reserves to help them get started
#43Chapt. 05
Life History Strategies
• Alternatives to the r and K continuum– Ruderals, competitors, and stress
tolerators (Grime 1977 and 1979)•Ruderals (botanical term for weed)
– Adapted to cope with habitat disturbances
#44Chapt. 05
Life History Strategies
•Competitors – Adapted to live in highly competitive but
benign environments (e.g., tropics)
•Stress tolerators– Adapted to cope with severe environmental
conditions (e.g., salt marsh plants)
#45Chapt. 05
Life History Strategies
•Stress, disturbance and competition triangle
– Figure 5.9
#46Chapt. 05
CHARACTERISTIC COMPETITORS RUDERALS STRESSTOLERATORS
Life form
Leaf size
Life span
Seed production
Growth rate
Palatability
Vegetative spread
Leaf litter production
Large herbs,shrubs or trees
•Large
•Long
•Small
•Rapid
•Various
•Yes
•High
Small herbs
•Large
•Short
•Large
•Rapid
•High
•No
•Low
Lichens, herbs,shrubs
•Small
•Long
•Small
•Slow
•Low
•Yes
•LowCompetitors
Hig
h Low
Com
petit
ion
Disturbance
HighLo
w
StressLowHigh
RuderalsStress tolerators
Intermediate Life histories
Trees Perennialherbs
Bryophytes
AnnualplantsLichens
#47Chapt. 05
Life History Strategies
•Demographic interpretation (Silverton et al. 1992, 1993)
– Growth-survival and fecundity triangle– Figure 5.10
#48Chapt. 05
G
Gro
wth
Survival
Fecundity
1.0 0.8 0.6 0.4 0.2 0.0
Semelparous herbs
Iteroparous herbs in open habitats
Iteroparous herbs in forests
Woody trees
0.0
0.2
0.4
0.6
0.8
1.0
0.0
0.2
0.4
0.6
0.8
1.0
SF
#49Chapt. 05
Applied Ecology
• Life history and the risk of extinction
• K-selected species– All attributes set them at risk to
extinction– Tend to be bigger – need bigger
habitat
#50Chapt. 05
Applied Ecology
• K-selected species (cont.). – Fewer offspring – populations can not
recover as fast from disturbance– Breed later in life – generation time is
long
#51Chapt. 05
Applied Ecology
• K-selected species (cont.). – Population size is small – high risk of
inbreeding– Examples
•Florida panthers•Giant sequoia tree
#52Chapt. 05
Applied Ecology
– Examples (cont.).•Large terrestrial mammals (elephants,
rhinoceros, and grizzlies)•Large marine mammals (blue and sperm
whales)
#53Chapt. 05
Summary
• Life history concerns lifetime patterns in reproduction and growth patterns– Semelparous– Iteroparous
#54Chapt. 05
Summary
• Reproductive strategy strongly affects age structure– Low ratio of young to adults –
population in decline– High ratio of young to adults –
population growing
#55Chapt. 05
Summary
• Sex ratio– 1:1 ratio expected in most
populations– Polygynous
•Males mate with more than one female
#56Chapt. 05
Summary
• Sex ratio– Polyandrous
•Females mate with more than one male•Monogamous
– Each individual has one mate
#57Chapt. 05
Summary– Polygamy is often based on limited
resources
• Categorizing life history strategies– r-K continuum
• r-selected– Poor competitors
#58Chapt. 05
Summary• r-selected (cont.).
– High per capita population growth rate– Disperse well– Colonize new habitats
•K-Selected– Good competitors– Usually exist in mature habitats, close to the
carrying capacity
– Alternative life history strategies
#59Chapt. 05
Summary
– Alternative life history strategies•Ruderals, competitors, and stress
tolerators classification•Growth-longevity-fecundity triangle
#60Chapt. 05
Discussion Question #1
• What particular life history strategies are possessed by successful exotic invaders like kudzu in the southeast or zebra mussels in the Great Lakes? Can knowing their life histories help us in the war against exotics?
#61Chapt. 05
Discussion Question #2
• How could you test the idea that there is a trade-off between life history strategies? What would happen if you plant salt marsh plants like Spartina grass or mangroves in a terrestrial habitat vs. a freshwater habitat?
#62Chapt. 05
Discussion Question #3
• In some species, males are much bigger than females, a property called sexual dimorphism. Speculate about the types of animals in which sexual dimorphism would and would not occur.