Habitat Selection And Dispersal

Front 1

Habitat

Back 1

home range
some are extremely selective, others are extremely generalized
different kinds of habitat use reflect built-in habitat preferences

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habitat selectin hypothesis(2)

Back 2

1. many habitat preferences innate
2. habitat preferences increase fintess

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examples of strong and innate habitat(plant species)

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-in insects and other invertebrates
-in may cases, order of host plant that is attractive
-use Y-maze selection device to test this

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Harris and Wecker
habitat selection in deermouse Peromyscus maniculatus-bairdi

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-inhabit grasslands and avoids woods
-P bairdi can live perfectly well in the woods
-they prefer grasslands if captured as adults and when captive-reared, even if reared in the woods
-this trend decreased over 12-20 laboratory generations
-no indication that there was a fintess coet to mice living in "incorrect" habitat

Front 5

Examples of innate habitat preferences in birds

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-hooded warbler males prefer tall, dense forests and females prefer forest edges or low-growth areas
-Eugene Morton: hand-reared hooded warblers and showed a preference for vertical striped artificial habitat, while females preferred oblique lines.
-Naive young coal tits innately prefer the foliage of pine trees (normal habitat) while bule tits prefer oak trees (prefeered habitat)
-Linda Partidge: tested hypothesis coal and blue tit habitat preferences increases fitness? Tested with artifical feeding habitats; better foraging success found in "preferred" foliage types

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How do animals select habitats?

ex of colony site selection in social insects

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-Bumblebee females look solitarily.
-ant and termite reproductives usually fly off and search for proper soil type, tree species etc

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Honeybees use highly social choice mechanism

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-sarming behavior in spring
-old queen and group od worker bees fly some distance from the old hive and settle temporarily
-scouts look for hive sites(burrows, tree holes, buildings, caves etc) and announce them using the same dance used to indicate food sources
-dances recruit other bees to explore sites
-eventually one site is preffered by all the bess and they move to it in mass
-Honybees select dispersal distance, site volume and location. These prefereces differ in bees from different environment
-Bavarian honeybee vs italian bees
-bavarian- long dispersal distnace preferred, large site volume preffered, ground or cliff hole as location.
-italian:short dispersal distance, small site volume prefeered, tree hole as location

Front 8

Whitham's work on poplar aphids, Pemphigus

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-fitness effects of hiabitat choice
-effects of leaf size and number of galls(broods of offspring+mother) on each leaf
-Relationship btw leaf size and reproductive success linear
-aphids select large leaves preferentially
-all of the large leaves are colonized, some of mid sized leaves and practivally none of the small leaves
-they multiply colonize some leaves, mostly on large leaves
-a female looking for a home might have a choice btw settling on an occupied leaf(sharing its resources with original owner) or settling on an unoccupied leaf- females make the correct choice in terms of reproductive success
-a female will have appromx equal reproductive success if she is the second female on a medium or large leaf, or the only female on a small leaf.
-still best to be the first female on medium or larger leaves because they get the best sites on the leaf(base). newcomers get suboptimal sites(farther out on the central rib)

Front 9

Ideal free distribution

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individuals can move whereever they want without interference.
-They should distribute themselves so that everyone has equal fitness(individuals in poor habitats are "free" to move to good habitats)

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"Despotic" distribution

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-individuals are NOT free to move about, due to aggression
-some individuals have higher fitness than others
-successful competition can defend resources and make them unavailable to weaker competitors

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Dispersal

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-moving from one home site to another
-NOT nomadism or migration(not a repeated movement)
-in most organisms it is the young animals that disperse
-One sex usually moves farther than the other
-in mammales, typically young males who move the farthest
-in birds, typically the females who move

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How far do animals disperse?

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usually not far
just a few home range diameters

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Why disperse?

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-Need to consider BOTH the dispersers and those who do not disperse
-it may be advantageous for parents to force their young to disperse to increase the parent's reproductive success
-other model:dispersal will benefit the dispersing individuals by reducing competition and inbreeding avoidance

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example of disperse by competition

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-dispersers move to an area where competition will be lower than "at home"
-deer mice(peter waser)-move out from natal home site until they come to an unoccupied site(proportions of short-distance and long-distance dispersal match those predicted by the competition model)

Front 15

example of disperse by avoidance of inbreeding

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Ground squirrels(holekamp and Sherman)-by moving away from natal burrow, young males reduce the chances of mating with close relatives and suffering reduced RS from inbreeding depression

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T/F
In most species, dispersal probably evolved under selection from multiple factors

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T

Front 17

Adults dispersion

examples

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-occasionally disperse or move from a "poor"home to a better one

ex.Adelie perguin adults are very nest-site specific if they are successufl. Unsuccessful breeders are more likely to move
ex. Red-winged blackbird males are highly site-specific year to year. Those that move tend to increase their reproductive success by doing so
Ex.Goldeneye ducks nest in tree cavities. Females that fail one year are much more likely to move than females that are successful