Individual variation: Personality 1 Flashcards
Concept that natural selection drives adaptation to optimality has been introduced previously
An example of this is : crabs selecting mussels
Tests of the model: –Elner & Hughes (1978)
*mussel size discrimination by predatory crabs
*crabs preferred intermediate-sized mussels, as predicted
*choices as predicted in environments of low and intermediate productivity
*however chose large mussels in high productivity environments, counter to predictions
-> Encounter rates violated assumptions
Optimality: Can natural selection optimise?
Depends on gene expression & on the mechanism of genetic change in populations
Particular importance:
–The rate at which selection can alter the genetic structure
–The amount of additive genetic variance present at the start of selection
–Gene flow (i.e. from immigration)
–Random effects (e.g. genetic drift)
^hindering optimum adaptation
But, natural variation will still be found around an optimum
–Heterogeneity & changing conditions mean that often populations are not perched at ‘adaptive peaks’
So there is natural variation around the optimum – is it adaptive or random? Interpreting graphs
when plotted with x=niche axis and y= resource abundance
there are two possible outcomes:
A) all take a similar size of food (generalist)
seen as a large bell curve
B) different individuals utilise different sizes of food in a narrower range (specialist)
seen as multiple curves with overlapping peaks and troughs
^ in crab example: This could occur due to different ages of crabs or size variation in adults
How could environmental change affect the crabs in A and B?
In A generalists may be able to adapt
In B some of the species population may be lost whilst others can take advantage of the change
Individual variation: relevance
A lot of interindividual variation is observed
*Most empirical and theoretical studies treat conspecific individuals as ecologically equivalent.
*Extensive evidence of inter-individual variation
as simple models assume all individuals are the same this impacts the accuracy of studies e.g. studies of foraging behaviour in seals
Individual variation relevance:
Ecological relevance: Management and conservation
*Urban invaders were not ‘tolerant/tame’ species, but tolerant individuals of spp with variable response to humans. (think foxes and pidgeons)
*Tolerance is elated to relative brain size and learning/behavioural flexibility
It is the behaviour of individuals, NOT the average species response that is critical.
Relevant in the context of rapid environmental change today
Individual variation &/or plasticity -> ability of populations to respond adaptively to environmental variation
Sources of individual variation
*Individuals of same spp. or population often differ in how they behave: e.g. aggressiveness
*Sex, age, size, status, condition -> differences.
But also, differences among individuals of same sex, age & size etc
But is this personality – what defines personality?
What does variety in personality bring to a species – humans are known to have diverse personalities and are a very successful species.
how can we quantify individual variation
Brown Anoles study in the Bahamas – on islands with predators cautious individuals survived better than risk takers – thus natural selection selects for behaviour as well as morphology (O. Lapiedra)
(see notes for graph)
Each line represents an individual, overall change in behaviour is observed however each individual adapts with different intensity.
consistent individual differences = CIDs were observed
consistent inter-individual differences (CIDs)
Consistent inter- individual differences (CIDs) that remain consistent over time and/or across contexts or situations within contexts
What is personality?
- individual behavioural differences over time & or across contexts, or situations within contexts.
- Personality: Variation among individuals in the intercept Of their behavioural reaction norm (Dingemanse et al. 2010).
- Beyond ‘simple’ sex, age & size differences.
— Personality
— Behavioural type
— Temperament
— Coping style
— Behavioural syndrome
‘Behavioural syndromes’
When individual differences in behaviour are consistent across contexts, situations or time (Sih et al. 2004a,b)
Formal definition: “A correlation between rank-order differences between individuals through time and/or across situations (contexts)”
»property of a population (Bell 2007)
Behavioural type
An individuals particular configuration of behaviours that the individual expresses.
»property of an individual.
in a graph comparing behaviours x and Y (see notes.) Each point is a different individual in the population, comparing the performance of behaviour X and Y showing correlation between behavioural traits
(Bell,2007)
A behavioural syndrome: sticklebacks
three-spined sticklebacks (Gasterosteus aculeatus)
Behaviour in response to predators
(Huntingford, 1976)
Behaviour in response to predator (e.g. Pike):
Found that bolder individuals were more active in unfamiliar environments and also more aggressive to conspecifics.
How can we show personality in non-human animals?
Standardised tests, controlled environments
Standardised tests, controlled environments:
–e.g. minimise effect of time of day, other conspecifics, etc
Requirements to demonstrate CIDs:
–behavioural variation.
–measure individuals more than once.
–set of standardized challenges,
–determine if individual differences are consistent across challenges.
-then you would plot the type of graphs shown in this lecture
How can we show personality in non-human animals?
Types of behavioural measures (‘assays’)
–Activity
–Sociality
–’aggressiveness‘
–shy-bold axis – how willing individuals are to take risks in a familiar environment
–neophobia – how individuals react to novel stimuli e.g. approach a new object or hide from it
–proactive-reactive axis – behavioural flexibility proactive-fixed reactive- more plastic
–exploratory behaviour : careful, attentive (‘slow’) or
cursory, superficial (‘fast’) (often quick to attack others, readily form routines).
How can we show personality in non-human animals?
Lab studies
classic laboratory studies (remember the fighting fish practical)
e.g. open field tests
lab rats – how much time spent in each cell of an open floor area
A risk taker will explore the central area more than a cautious individual
e.g. maze tests: remember woodlouse study
