Insects parents and offsprings interact with each other, offspring influence the total parental invesment through signalling. singalling models are honest signalling and scramble competition model. Sibling rivalry for limited resources

1. Presentation on
Parent- Offspring Conflicts and
Sibling Rivalry
Presented by
K. V. NAGARJUNA REDDY
Ph.D Scholar
Dept of Entomology
IGKV, Raipur

2. INTRODUCTION
• Early life - mothers invest heavily on offsprings - maximize their fitness.
• Traditionally - assumption - harmonious cooperation with mother- maternal
and offspring genes will benefit.
• Above assumption conflicts – prediction - two parties compete - over how
much of a finite pool of maternal resources.
We agree with youWe don’t agree with you

3. Most common form of post hatching parental care
- protection against predators
- parental food provisioning

4. • POC theory- offspring protection - parental investment - offspring
influence - the protective tendency of the mother.
• Chemical signalling- most important mode of communication-
contexts of sexual selection, social recognition and regulation.
• Chemical cues - caregiver food provisioning in burrower bugs, S.
cinctus bumblebees, Bombus terrestris and honeybee, Apis
mellifera

5. Parent-offspring conflicts
• Parental care - benefit - outweigh the cost of care - parents forego the
opportunity to produce additional offspring.
• Females caring for offspring delay and/or reduce their future reproductive
output relative to noncaring females
• Offspring interact behaviorally - influence the duration and amount of
costly care.
Why parents are not willing to
provide complete care to offsprings ???

6. • Parents - 50% related to each of their offspring
• Offspring- 100% related to itself
50% related to its full-siblings
25% related to its half-siblings
You all are equal to me !!!
I am more important to
myself than my sibling !!He is just 50% related to me !

7. W. D. Hamilton, 1964
According to me, each offspring values
its own inclusive fitness more highly
than that of its full or half siblings, and
is predicted to maximize its fitness by
seeking more than its fair share of
maternal resources.
• Mother - related equally - will maximize inclusive fitness - invest equally in
each offspring.
• Potential for reciprocal parent-offspring interactions - opportunity for parent-
offspring conflict - evolution of offspring begging signals

8. • Solicitation (begging)
• Parents - prefer to allocate resources evenly - offspring obtain more
food from the parents.
• Conflict - allocation of resources - attempts by offspring - bias
provisioning- towards itself through solicitation
• Contrast - need for protection - the need for food - typical
proximate context - parent offspring conflict has been studied

9. Best studied examples for insect begging behaviour
Larvae of Nicrophorus vespilloidesLarvae of VespidaeLarvae of Formica sanguinea and Solenopsis invicta

10. • Signals - ‘any act or structure that alters the behavior of other organisms,
which evolved owing to that effect, and which is effective because the
receiver’s response has also evolved.
• In these models- two major scenarios for conflict resolution.
• Scramble models - sibling rivalry drives the evolution of competitive
begging (Parker and Macnair 1979)
• Honest-signalling models - parents actively select for offspring begging
signals that ‘honestly’ reflect their true need

11. • Offspring - beg to signal their needs to the parents. Offspring adjust begging
behaviour - number of competitors in the brood .
• Chemical communication - Earwig mothers and their offspring - Females
allocate food to individual offsprings - direct regurgitation by mouth-to-
mouth contact.
Scramble competition model

12. • Offspring - secrete a blend of hydrocarbons – cuticle - vary with nutritional
condition - mothers adjust food provisioning.
• Individual offspring - directly influence - begging and competing with siblings.
• Mothers forage - regurgitate more - exposed to chemical cues from highly fed
nymphs - compared to low fed nymphs.
• Positive maternal response - chemical cues from well-fed offspring - supports
prediction - signal of quality rather than a signal of need.

13. • High juvenile mortality - parents feed offspring- higher reproductive
value – to maximize their fitness return on parental investment (Haig
1990).
• Kölliker (2007) - high juvenile mortality in earwig.
• Maternal investment - allocated to nymphs of low condition - with low
likelihood to survive - maladaptive for mothers.
• Maternal investment - costly - selection on mothers - to maximize return
on investment -favouring offspring of good quality.
Why did earwig mothers fed healthy
offsprings more than the weaker ones ?

14. • Eusocial insects - chemical stimuli - brood.
• Bumble-bees (Bombus terrestris) - workers fed significantly more - larvae
sprayed with extracts - food-deprived larvae (den Boer and Duchateau 2006).
• Honeybees (Apis mellifera) - hexane extracts of brood - affect foraging
activity of workers (Pankiw et al. 1998; Pankiw 2007).
• Bee foragers - brood pheromone - estimate the level of need of the brood -
lasting consequences for their physiology (Le Conte et al. 1995, 2001).

15. Honest signalling models assume that
1. Parents - greater fitness benefits - provisioning offspring in poor condition -
good condition offspring.
2. Solicitation signals - allow parents – distribution of resources - parental
fitness benefits – maximized.
3. Begging signal - costly to maintain - honest signal
Honest signaling model

16. • Hemipteran species - nymphs specialized dorso-abdominal glands -
chemical cues - in danger.
• Chemical cues - defensive response from the
mother.
• Subsocial thornbug treehopper (Umbonia
crassicornis) - offspring - substrate-borne
vibrational signal addition to chemical signals -
trigger maternal defensive behaviours.
• Activity of several offspring - required to trigger
the defensive response.

17. • Protection - shared maternal investment - not only the signalling
individual - other siblings - benefit from the maternal protection.
• Competition between siblings - to signal more than others - not
expected to evolve - will benefit everyone.
• Begging for protection - honest signal
Will the offspring signaling with more intensity
get more protection ??

18. • The evolution of - honest Vs manipulative signal - core of parent-
offspring conflict theory.
• Begging signals- priming effect on maternal physiology -
interests of offspring - at the expense of future broods.
• Evolutionary interests of mothers - transient (i.e. releaser-type)
effects on their behaviour - respond flexibly -variation in offspring
conditions.

19. SIBLING RIVALRY

20. • Sibling rivalry - type of competition - among siblings.
• Offspring trait - increases individual offspring's fitness - expense of the
fitness - lead to sibling rivalry.
• Species with parental care - intense sibling competition - through sublethal
scramble competition (begging) - lethal aggressive brood reduction
(siblicide).
• Key ecological factor - limitation of resources critical for offspring
development - food (Mock and Parker, 1997; Roulin and Dreiss, 2012).

21. Resource limitation - consequence of parental overproduction of offspring -
may be adaptive if it allows the parent to
1. Take advantage of favourable but unpredictable ecological conditions.
2. Offspring that enhance the fitness of core offspring (e.g. by assisting in
thermoregulation or serving as food).
3. Compensation of core offspring death.

22. • Parental overproduction - sibling competition promoted – demand exceeds
supply
• brood size and resource availability - affect outcome of sibling competition-
Effect independently.
• Complex scenarios occur

23. Strange life cycle of Copidosoma floridonum
Adult wasp parasitizing moth’s egg Eggs develop into caterpillars
and parasitoids develop within
the caterpillar
Upto quarter of parasitoid larvae
develop into soldiers (A) and rest of
the larvae into reproductive (B)

24. Final stage of infestationInitial stage of infestation

25. You have mentioned that the soldiers will
attack the larvae of other wasps. Other wasps
larvae cannot be considered as siblings. Then
how can it be an example of sibling rivalry
???

26. Nicrophorus vespilloides
Sibling rivalry in burying beetles
Crater on the carcass
Nesting site

27. Grubs begging their parents

28. What will happen if parents abandoned these
grubs??
Will there be sibling rivalry ??
Will all the larvae die ??
Will only 1 larva survive ??

29. CONCLUSION
• Insect species - post hatching parental care - protection and/or food - to
the whole brood and/or to individual offspring.
• Potential to study - differential effects of parent-offspring interactions -
evolution of begging signals - maintenance of maternal care.
• An in-depth study of chemical mother-offspring interactions -
identification of solicitation pheromones - promising way to find systems
- predictions could be tested.

30. • Focus on chemical communication - offer a new perspective of research -
test proximate mechanisms of maternal care regulation and the evolutionary
function of offspring begging signals
• Research in chemical signalling and hormonal regulation of offspring
begging and maternal provisioning - substantiate the currently scarce, but
promising, data on parental -offspring conflicts in social insects.