Lecture 8 THE EVOLUTION OF LIFE HISTORIES–II Flashcards
Trinidadian Guppies (Poeciliareticulata)
Live in streams in Caribbean island of Trinidad
*Eggs develop into live young within the female
*Female provides resources young
*Influence size of offspring at birth
*Size at birth influences odds of survival to adulthood
*Female guppy’s overall fitness is a function of:
*Number of offspring per litter
*Number of litters over her lifetime
*Face different levels of predation pressures
*Streams with high predation and streams with low predation
Trinidadian Guppies studies
Mark recapture studies on natural populations in pools in small streams
*High-predation environments increase mortality rates compared to guppies from low-predation environments
*High mortality associated with the following (they all have Genetic basis):
*Earlier maturity
*Increased investment of resources in reproduction
*More and smaller offspring
how can mortality rates be manipulated?
Mortality rates can be manipulated
*Transplanted guppies from:
*High-predation localities to sites from which they and the predators were previously excluded by natural waterfalls resulted in lowered mortality rates
*Low-predation localities to high-predation sites resulted in increased mortality rates
*The transplantation experiments show species evolve as predicted by theory
Bulb mite
pest species on variety of bulbs
*Life cycle includes a male dimorphism and facultative dispersal stage
Quality of food plays a key role in determining life history traits
*Interaction with male dimorphism
*Dictates dispersal
Expectations: Poorer environments can impact age and size of maturity
Describe bulb mite life cycle
look at lecture
Bulb mite (Rhizoglyphusrobinii) –male dimorphism
*When environmental conditions become more favourable most organisms mature earlier at a larger body size
*The male dimorphism allows for a unique opportunity to investigate how the interaction of the paternal phenotype (male dimorphism), maternal environment and offspring environment impact age and size at maturity
*Very few studies have assessed the intergenerational effects between age and size at maturity
Bulb mite (Rhizoglyphusrobinii) –dispersal
Dispersal can have a substantial impact on survival and reproduction
*Calls to integrate dispersal into life history theory as a principle trait impacting fitness (Bonte & Dahirel2017, Oikos)
*Without dispersal there is an increased risk of extinction in changing environments –whatever the survival rate and reproductive output
*Bulb mite provides the opportunity to determine potential trade-offs between investing in dispersal and other life history trait
Planaria
*From the phylum Platyhelminthes, common in freshwater streams and ponds
*An extensive body of literature on these animals dating back to the work by Pallas in 1774
*Have an immortal life history, they replace all body tissues and cell types
*Able to grow and shrink when nutrient conditions change
*They are able to regenerate
Can be sexual or asexualAsexual reproduction occurs via binary fission (force themselves to split in two)
can planaria die?
*The lack of ageing is an emergent property of both being:
*Highly regenerative
*The evolution of highly effective molecular mechanisms for ensuring genome stability in the stem cell population
*However!
*Does not mean planaria can’t die
*Can suffer hardships and die
Severity of extrinsic factors is not equivalent across species in a group with
*Immortal life history is context-dependent
What have we covered?
*The evolution of Life histories can be seen in a natural setting occuringon a short timescale
*Intergenerational effects and dispersal can have a significant impact on Life history traits such as age and size at maturity
*On the continuum of Life history variation, unique Life histories can evolve to maximises fitness
