AULA 3: HISTÓRIAS DE VIDA
¡
Quais são as duas estratégias de vida dos
organismos investigados no estudo de
Monteiro et al. 2007?
¡
O QUE SÃO INDIVÍDUOS?
¡
ORGANISMOS UNITÁRIOS E MODULARES
¡
CONTANDO INDIVÍDUOS
¡
LIMITES POPULACIONAIS
¡
CICLOS DE VIDA
¡
ALOCAÇÃO DE RECURSOS E HISTÓRIAS DE VIDA
¡
ESTRATÉGIA r/K
¡
EVOLUÇÃO DE HISTÓRIAS DE VIDA
¡
”Take-home messages”
¡
Grupo de organismos da mesma espécie que
ocupam o mesmo espaço em um dado tempo.
TAMANHO POPULACIONAL
TAMANHO
POPULACIONAL
NATALIDADE
EMIGRAÇÃO
MORTALIDADE
IMIGRAÇÃO
TAMANHO POPULACIONAL
TAMANHO
POPULACIONAL
NATALIDADE
EMIGRAÇÃO
MORTALIDADE
IMIGRAÇÃO
TAMANHO POPULACIONAL
TAMANHO
POPULACIONAL
NATALIDADE
EMIGRAÇÃO
MORTALIDADE
IMIGRAÇÃO
QUANTOS INDIVÍDUOS?
¡
ORGANISMOS UNITÁRIOS
QUANTOS INDIVÍDUOS?
¡
ORGANISMOS UNITÁRIOS
Forma determinada
Tempo de vida determinado
¡
ORGANISMOS MODULARES
Forma imprevisível
ORGANISMOS UNITÁRIOS
¡
Mudanças de fase previsíveis
¡
Permanece na mesma forma ao longo da vida
¡
Zigoto – nascimento – infância – adulto –
ORGANISMOS MODULARES
¡
São desenvolvidos módulos – unidades de
construção ao longo do crescimento
ORGANISMOS MODULARES
¡
São desenvolvidos módulos – unidades de
construção ao longo do crescimento
ORGANISMOS MODULARES
¡
Altamente dependentes da interação com o
meio para o seu crescimento:
¡
Condições!!
¡
Temperatura, pluviosidade, hidrodinamismo,
salinidade, etc.
COMO QUANTIFICAR OS INDIVÍDUOS?
¡
GENET vs. RAMET
¡
Indivíduo genético vs. Clone
Genet, ou indivíduo genético, é
resultante da reprodução e do
desenvolvimento do zigoto. O clone
é resultante do crescimento de
módulos no mesmo indivíduo.
QUANTIFICAÇÃO depende do
objetivo da PESQUISA
COMO CRESCEM OS ORGANISMOS
MODULARES?
COMO CRESCEM OS ORGANISMOS
MODULARES?
¡
Vertical ou lateral
SENESCÊNCIA EM ORGANISMOS
MODULARES
Morte anual de folhas: exemplo
extremo de senescência em plantas
caducifólias.
••
LIFE, DEATH AND LIFE HISTORIES 93
the Great Barrier Reef in Figure 4.2. Annual mortality declined sharply with increasing colony size (and hence, broadly, age) until, amongst the largest, oldest colonies, mortality was virtually zero, with no evidence of any increase in mortality at extreme old age (Hughes & Connell, 1987).
At the modular level, things are quite different. The annual death of the leaves on a deciduous tree is the most dramatic
example of senescence – but roots, buds, flowers and the modules of modular animals all pass through phases of youth, middle age, senescence and death. The growth of the individual genet is the combined result of these processes. Figure 4.3 shows that the age structure of shoots of the sedge Carex arenaria is changed dramatically by the application of NPK fertilizer, even when the total number of shoots present is scarcely affected by the treat-ment. The fertilized plots became dominated by young shoots, as the older shoots that were common on control plots were forced into early death.
4.2.5 Integration
For many rhizomatous and stoloniferous species, this changing age structure is in turn associated with a changing level to which the connections between individual ramets remain intact. A young ramet may benefit from the nutrients flowing from an older ramet to which it is attached and from which it grew, but the pros and cons of attachment will have changed markedly by the time the daughter is fully established in its own right and the parent has entered a postreproductive phase of senescence (a comment equally applicable to unitary organisms with parental care) (Caraco & Kelly, 1991).
The changing benefits and costs of integration have been studied experimentally in the pasture grass Holcus lanatus, by comparing the growth of: (i) ramets that were left with a phy-siological connection to their parent plant, and in the same pot, so that parent and daughter might compete (unsevered,
•• 0–10 69 57 38 10–50 79 30 39 >50 82 3 8 Annual mortality (%) 0 20 40 60 Colony area (cm2) 10 30 50 Acropora Porites Pocillopora
Figure 4.2 The mortality rate declines steadily with colony
size (and hence, broadly, age) in three coral taxa from the reef crest at Heron Island, Great Barrier Reef (sample sizes are given above each bar). (After Hughes & Connell, 1987; Hughes et al., 1992.) >9 8–8.9 7–7.9 6–6.9 5–5.9 4–4.9
Cohort age (months)
Control January 1976 3–3.9 2–2.9 1–1.9 0–0.9 Fertilized >9 8–8.9 7–7.9 6–6.9 5–5.9 4–4.9 Control Mature phase July 1976 3–3.9 2–2.9 1–1.9 0–0.9 Fertilized
Figure 4.3 The age structure of shoots in clones of the sand sedge Carex arenaria growing on sand dunes in North Wales, UK. Clones
are composed of shoots of different ages. The effect of applying fertilizer is to change this age structure. The clones become dominated by young shoots and the older shoots die. (After Noble et al., 1979.)
SENESCÊNCIA EM ORGANISMOS
MODULARES
Morte anual de folhas: exemplo
extremo de senescência em plantas
caducifólias.
••
LIFE, DEATH AND LIFE HISTORIES 93
the Great Barrier Reef in Figure 4.2. Annual mortality declined sharply with increasing colony size (and hence, broadly, age) until, amongst the largest, oldest colonies, mortality was virtually zero, with no evidence of any increase in mortality at extreme old age (Hughes & Connell, 1987).
At the modular level, things are quite different. The annual death of the leaves on a deciduous tree is the most dramatic
example of senescence – but roots, buds, flowers and the modules of modular animals all pass through phases of youth, middle age, senescence and death. The growth of the individual genet is the combined result of these processes. Figure 4.3 shows that the age structure of shoots of the sedge Carex arenaria is changed dramatically by the application of NPK fertilizer, even when the total number of shoots present is scarcely affected by the treat-ment. The fertilized plots became dominated by young shoots, as the older shoots that were common on control plots were forced into early death.
4.2.5 Integration
For many rhizomatous and stoloniferous species, this changing age structure is in turn associated with a changing level to which the connections between individual ramets remain intact. A young ramet may benefit from the nutrients flowing from an older ramet to which it is attached and from which it grew, but the pros and cons of attachment will have changed markedly by the time the daughter is fully established in its own right and the parent has entered a postreproductive phase of senescence (a comment equally applicable to unitary organisms with parental care) (Caraco & Kelly, 1991).
The changing benefits and costs of integration have been studied experimentally in the pasture grass Holcus lanatus, by comparing the growth of: (i) ramets that were left with a phy-siological connection to their parent plant, and in the same pot, so that parent and daughter might compete (unsevered,
•• 0–10 69 57 38 10–50 79 30 39 >50 82 3 8 Annual mortality (%) 0 20 40 60 Colony area (cm2) 10 30 50 Acropora Porites Pocillopora
Figure 4.2 The mortality rate declines steadily with colony
size (and hence, broadly, age) in three coral taxa from the reef crest at Heron Island, Great Barrier Reef (sample sizes are given above each bar). (After Hughes & Connell, 1987; Hughes et al., 1992.) >9 8–8.9 7–7.9 6–6.9 5–5.9 4–4.9
Cohort age (months)
Control January 1976 3–3.9 2–2.9 1–1.9 0–0.9 Fertilized >9 8–8.9 7–7.9 6–6.9 5–5.9 4–4.9 Control Mature phase July 1976 3–3.9 2–2.9 1–1.9 0–0.9 Fertilized
Figure 4.3 The age structure of shoots in clones of the sand sedge Carex arenaria growing on sand dunes in North Wales, UK. Clones
are composed of shoots of different ages. The effect of applying fertilizer is to change this age structure. The clones become dominated by young shoots and the older shoots die. (After Noble et al., 1979.)
CONTANDO INDIVÍDUOS
•
Censos, transectos,
armadilhas, quadrats,
redes;
•
Abundância
•
Densidade
•
Biomassa
CICLOS DE VIDA
¡
Que forças atuam sobre cada fase do ciclo de
vida de organismos?
¡
Conhecer o CICLO DE VIDA!
nascimento – período pré-reprodutivo – período
reprodutivo – período pós-reprodutivo – morte
CICLOS DE VIDA
¡
Espécies SEMÉLPARAS E ITERÓPARAS
SEMÉLPARAS
Indivíduos apresentam um
único evento reprodutivo,
investindo pouco em eventos
futuros
ITERÓPARAS
Indivíduos apresentam vários
eventos reprodutivos, alguns
sazonais, outros não.
CICLOS DE VIDA
•• •• 96 CHAPTER 4 Year 1 Juvenile phase Time Year 1 Juvenile phase Time (b) (c)Year 1 Year 2 Year 3 Year 4 Year 5 Juvenile
phase Reproductive phase
(d)
Year 1 Year 2 Year 3 Juvenile phase Reproductive output Reproductive phase (e) Time
Year 1 Year 2 Year 3 Year ndeath
Juvenile phase
(f)
onset of reproduction
birth end of
reproduction to senescencedeath due Time
Juvenile phase dominated
by growth Reproductivephase Postreproductivephase
Reproductive output
(a)
Figure 4.6 (a) An outline life history
for a unitary organism. Time passes along the horizontal axis, which is divided into different phases. Reproductive output is plotted on the vertical axis. The figures below (b–f ) are variations on this basic theme. (b) A semelparous annual species. (c) An iteroparous annual species. (d) A long-lived iteroparous species with seasonal breeding (that may indeed live much longer than suggested in the figure). (e) A long-lived species with continuous breeding (that may again live much longer than suggested in the figure). (f ) A semelparous species living longer than a year. The pre-reproductive phase may be a little over 1 year (a biennial species, breeding in its second year) or longer, often much longer, than this (as shown).
EIPC04 10/24/05 1:49 PM Page 96
Um padrão da história de vida
para um organismo unitário.
Semélpara anual
CICLOS DE VIDA
•• •• 96 CHAPTER 4 Year 1 Juvenile phase Time Year 1 Juvenile phase Time (b) (c)Year 1 Year 2 Year 3 Year 4 Year 5 Juvenile
phase Reproductive phase
(d)
Year 1 Year 2 Year 3 Juvenile phase Reproductive output Reproductive phase (e) Time
Year 1 Year 2 Year 3 Year ndeath
Juvenile phase
(f)
onset of reproduction
birth end of
reproduction to senescencedeath due Time
Juvenile phase dominated
by growth Reproductivephase Postreproductivephase
Reproductive output
(a)
Figure 4.6 (a) An outline life history
for a unitary organism. Time passes along the horizontal axis, which is divided into different phases. Reproductive output is plotted on the vertical axis. The figures below (b–f ) are variations on this basic theme. (b) A semelparous annual species. (c) An iteroparous annual species. (d) A long-lived iteroparous species with seasonal breeding (that may indeed live much longer than suggested in the figure). (e) A long-lived species with continuous breeding (that may again live much longer than suggested in the figure). (f ) A semelparous species living longer than a year. The pre-reproductive phase may be a little over 1 year (a biennial species, breeding in its second year) or longer, often much longer, than this (as shown).
EIPC04 10/24/05 1:49 PM Page 96
Iterópora de vida longa com
reprodução sazonal
Semélpara que vive mais de um
ano
Vida longa com reprodução
contínua
HISTÓRIAS DE VIDA
Os atributos do calendário de vida de um
indivíduo – idade da maturidade, número
de descendentes, expectativa de vida –
compõem a história de vida do indivíduo.
HISTÓRIAS DE VIDA
Influenciadas por:
•
Fatores ambientais
•
Estrutura do corpo (tamanho)
•
Estilo de vida (desenvolvimento e hábitat)
•
Respostas individuais às condições e
HISTÓRIAS DE VIDA
Influenciadas por:
•
Fatores ambientais
•
Estrutura do corpo (
tamanho
)
•
Estilo de vida (
desenvolvimento
e hábitat)
•
Respostas individuais às condições e
recursos
Como alocar meus recursos???
RECURSOS E HISTÓRIAS DE VIDA
RECURSOS E HISTÓRIAS DE VIDA
ESTRATÉGIAS R E K
¡
Busca por padrões nas histórias de vida
¡
Proposto por MacArthur & Wilson (1967),
elaborado por Pianka (1970)
¡
r: taxa intrínsica de crescimento natural
¡
K: tamanho (capacidade de suporte) de uma
população, limitada pela competição
Atributo de história de
vida
r-estrategistas
K-estrategistas
Hábitat
Ambiente instável
Ambiente estável
Regulação populacional
densidade independente
densidade dependentes
Flutuações populacionais
Constantes
Estável próxima a K
Prole
Grande, tamanhos
pequenos
Poucos, tamanhos grandes
Sobrevivência da prole
Baixa
Alta
Competitividade
Baixa
Alta
Cuidado parental
Raro
Comum
Maturação sexual
Cedo
Tardia
Eventos reprodutivos
Poucos
Muitos
ESTRATÉGIAS R E K
Ostras são um exemplo de r-estrategistas. Elas produzem 500 milhões de ovos por ano e
não tem cuidado parental. Os grandes primatas são um exemplo de k-estrategistas: um
K-estrategistas
¡
Indivíduos são favorecidos pela sua
capacidade de contribuir para a população,
a qual é mantida próxima a capacidade
suporte
¡
Vive em hábitats constantes
¡
População adensada, competição elevada
entre adultos e jovens
¡
Tamanho grande, reprodução tardia, prole
maior, alocação reprodutiva baixa,
iteroparidade, vida mais curta
K-estrategistas
R-estrategistas
¡
Hábitat imprevisível no tempo
¡
População experimenta períodos favoráveis
(crescimento rápido)
¡
Taxas variáveis de mortalidade de jovens e
adultos
¡
Tamanho corporal menor, maturidade
precoce, maior alocação reprodutiva,
descendentes de tamanho menor e em
maior número
R-estrategistas
R-estrategistas
RECURSOS E HISTÓRIAS DE VIDA
LIFE, DEATH AND LIFE HISTORIES
125
ability of a single genotype to express itself in different ways in different environments is known as phenotypic plasticity.
One of the most important questions we need to ask about phenotypic plasticity is the extent to which it represents a response by which an organism allocates resources differently in different environments such that it maximizes its fitness in each. The alternative would be that the response represented a degree of inevitable or uncontrolled damage or stunting by the environment (Lessells, 1991). Note, especially, that if phenotypic plasticity is governed by natural selection, then it is just as valid to seek patterns linking different environments and the different responses to them by a single individual, as it is to seek patterns
linking the habitats and the life histories of genetically different individuals.
In some cases at least, the appropriateness of a plastic response seems clear. For example, kestrels (predatory birds) in the Netherlands vary in the quality of their territory, the size of their clutch and the date on which they lay it (Daan et al., 1990). The differences appear not to be genetically determined but to be an example of phenotypic plasticity. Is each combination of clutch size and laying date optimal in its own territory?
The optimal combination is, as usual, the one with the highest total reproductive value – the value of the present clutch plus the parent’s RRV. The value of the present clutch clearly
•• •• Seed weight (g) 100 10–1 10–2 10–3 10–4 10–5 10–6
Open habit, short grass Woodland margins Woodland ground flora Woodland shrubs Woodland trees
Age of first reproduction (years)
Lifespan (years) 100 50 10 5 5 10 50 100 500 1000 (c) Herbs Shrubs Trees (angiosperms) Trees (conifers) Semelparous Iteroparity Semelparity
Perennials, including trees
Wild annuals
Grain crops
0 10 20 30 40
Net reproductive allocation (%)
(b) (a)
Figure 4.30 Broadly speaking, plants
show some conformity with the r/K scheme. For example, trees in relatively
K-selecting woodland habitats: (a) have
a relatively high probability of being iteroparous and a relatively small
reproductive allocation; (b) have relatively large seeds; and (c) are relatively long lived with relatively delayed reproduction. (After Harper, 1977; following Salisbury, 1942; Ogden, 1968; Harper & White, 1974.) EIPC04 10/24/05 1:49 PM Page 125
