1. Ants Complex Adaptive Systems, CS 591 Ants Complex Adaptive Systems, CS 591 April 16, 2008 Prof. Melanie Moses

2. Basic Ant Biology All ants are eusocial –The colony is the unit of selection Queen(s): reproducers, not masterminds Reproductives: winged male and female alates Workers: female, short lived compared to queens –Genetic sex determination Haplodiploidy Sociobiology –Division of labor: All males are reproductive female caste determined by environment & larval feeding Allows learning, farming, herding, fishing(?!)… Communication primarily through pheromones Self organization (dumb ants, smart colonies)

3. Weaver Ants

4. Ant Diversity “Lean against a tree almost anywhere, and the first creature that crawls on you will probably be an ant.” Holldobler and Wilson, Journey to the Ants (1995) In the world: 10 16 ants; 10,000 spp. Colony size: ~10 to 10 million workers per colony Diversity decreases with latitude A nts live everywhere –Soils –Leaf litter –Tree canopy –In or under logs, rocks,sidewalk cracks, your house Ants eat everything –Seeds –Nectar (honey pots) –Leaves/fungus –Other insects (esp. termites) –Each other

5. The New World Atta Leaf cutters

6. Mutualisms

7. Army Ants Photos by Steven Holt http://www.stockpix.com/stock/animals/invertebrates/arthropods/insects/ants/

8. Army Ants Photos by Alex Wild SWRS, Portal, AZ www.myrmecos.net

9. Worker castes “Human societies send their young men to war, and colonies send their old ladies.” Holldobler and Wilson, The Ants (1990) Old workers take on dangerous tasks Many spp have morphological differences in castes Trend toward increasing caste differentiation in large colonies –Foragers –Nurses –Soldiers, –Scouts & patrollers –Nest maintenance workers –Repletes

10. Myrmecocystus

11. Ant Colony Lifecycle Queens and males fly from nests to mate Male dies Queen mates 1+ times, drops wings, digs nest 1 st season: queen may forage or rely on stored fat After 1 st workers emerge: queen remains in nest First workers forage to feed themselves and the queen Very high mortality of juvenile colonies

12. Ant Mating

13. Ant Movement Migration by founding queens Colony movements –Relocations –Polydomous colonies –Army ants/bivouacs Worker movements –Patrollers –Nest maintenance, midden work –Foragers Foraging with pheromones: –information exchange, “stigmergy”, positive feedbacks & the social optimum

14. Desert Seed Harvesters

15. Pogonomyrmex spp. Monogynous, monodomous, monomorphic Stationary colonies Sterile workers Similar –behavior –diet (seeds, termites) –ant size (13-23 mg) Foraging period set by temperature & humidity Colony lifespan: up to 20 years Guilds of spp. associated w/ climate & elevation (Johnson 2000)

16. 2003 Portal, AZ 2003 & 2004 Sevilleta LTER P. desertorum 40-100 foragers/colony P. maricopa 150-250 foragers/colony P. rugosus 1500-2500 foragers/colony Colony size

18. Foraging in Ant Colonies Workers organize to increase the survival and reproduction of the colony without central control Colony metabolism is determined by foraging success: foragers collect all of the food that the colony consumes Colony population size ranges from 10 to 10 million There are costs and benefits to increased size How does colony size influence acquisition of energy and information? How do foraging networks scale with the size of the colony? How does network scaling affect colony behavior? Model and field study of Pogonomyrmex (seed harvesting ants)

19. Big colonies need big territories Longer foraging trips require more energy & reduce energy intake rates