Animal behaviour-brood parasities

7/29/2019 Animal behaviour-brood parasities

1/18

Parasitism

Evolutionary equilibrium or

contuining arms race?


2/18

Tight coevolution and diffuse

coevolution


3/18

Comparison certain ecological characteristics that vary

along a parasitepredator spectrum


4/18

Brood parasitism

the surreptitious addition of eggs to another females nest, whether of the

same (intraspecific) or different (interspecific) species There are several species of fish, insect and birds that are

obligate interspecific brood parasites.

These birds lay their eggs in the nests of other birds andprovide no parental care.

Brood parasitism is an antagonistic evolutionary interaction

between species

Brood parasitism


5/18

Atemeles sp.

Atemeles beetles are one of the many insects

that are parasites in ant nests. The ants respond to

the beetles as if to other ants, feeding them.


6/18

Atemeles sp.

(a) Offering food by a Formica worker-

ant to a beetle-larva

(Atemeles pubicollis) that parasitically

lives in the ant nest.(b)Atemeles-larva with position of the

cutaneus glands (k) producing baits for

the host ants.

After Hlldobler, from Hadorn andWehner, 1977)


7/18

Atemeles sp.

Atemeles emigrate from the ant nest (Formica) where theyhave been raised during the summer, to the nests ofanother ant genus (Myrmica). After wintering there, theyreturn to their original nest to breed in the springtime.

There is of course a reason for these moves:

In the Formica nests, the immature stages disappear duringthe winter, and consequently social food flow is reduced.

In contrast, the Myrmica colony maintains brood

throughout the winter and high-grade food sources areavailable for theAtemeles.


8/18

Cuculus canorus

Common Cuckoos are unrivaled

at laying eggs that resemble

their hosts.

Eurasian cuckoo chicks

maneuver under host eggs and

chicks and dump them over the

edge of the nest. Their backs

have a neatly designeddepression that just fits their

potential competitor.


9/18

(1)Eggs matched for size

(2) thicker egg shells

(3) Egg color and pattern

(Cuckoos and in the more

host specific cowbirds),Nestling mimicry is absent in

Host-intolerant spp (Cuckoos)

Host adaptations and

mimicry


10/18

Young cuckoo mimicry


11/18

Cryptic egg coloration


12/18

Whereas the Brown-headed Cowbird,

a recently encounter parasite species

for many hosts, does not use cryptic

egg coloration

Parasitized Red-eyed Vireo nestParasitized Wood Thrush nest


13/18

Brood parasites exploit the host parents'

tendency to feed the largest young in a

brood and the one that can reach highest

most.

By laying in the nests of smaller birds,

cuckoos give their young an advantage in

the competition for food. So do

cowbirds whose eggs hatch after a

shorter incubation period which allowsthem to hatch before the hosts young.

Effect of brood parasites


14/18

Contuining arms race

Why tolerate parasites eggs?

Accepting a parasites egg is even more likely to be adaptive

when the host is too small to remove the parasitic egg.

Such hosts must either accept the egg or abandon the nest,which is an expensive option, especially if nest sites are scarce

(e.g. as in cavity nesters).

Some birds do recognize parasitic eggs and remove them from

the nest. However, there is a risk that the host will discard one

or more of its own eggs in error.

Reed Warblers have been shown to make this mistake.


15/18


16/18

Evolutionary equilibrium

Hosts can be acceptors or rejecters actually acontinuum, and a function of time of sympatry

Egg removal e.g., catbird

Egg smashing e.g., orioles

Nest abandonment many passerines in NA

Build a second nest on top the original Yellowwarbler


17/18

Conclusion

As selection operates on both hosts and parasites

the differing selection pressures have resulted in

an arms race between hosts and parasites.

Brood parasites have a significant effect on the

reproductive success of the hosts. So, with many

other species the arms-race between parasites

and hosts is ongoing.

Bener ga sih? Tolong dikoreksi ya


18/18

Thank you

Coevolutionary arms race

it takes all the running you can do, just to

keep in the same place. -The Red Queen

(from Alice in Wonderland)

Documents

Animal behaviour-brood parasities