Animal Behaviour. Mark Elgar. Eusociality II

Transcription

1 Animal Behaviour Mark Elgar Eusociality II

2 Outline Evolution of sociality in insects How much care to give Conflicts of interest re-visited

3 Social doesn t always mean complex These social insects have relatively simple social organisations

4 Altruistic behaviour Altruistic behaviour = helping others at the expense of personal reproduction Selection will not favour this behaviour Taking the altruism out of altruistic behaviour: Kin selection Individual and/or mutual benefits

5 Hamilton s rule Altruistic behaviour will be selected for if: br - c > 0 where b = beneficiary c = cost to donor r = coefficient of relatedness (degree to which actor and beneficiary share genes)

6 Hamilton s rule Altruistic behaviour will be selected for if: br - c > 0 r = 1 for individuals that are genetically identical (clones) r = 0 for individuals that share no genes

7 Altruism in clonal organisms Aphids reproduce asexually Coefficient of relatedness (r) between soldiers and reproductive = 1 Sterile soldier that helps clone-mates reproduce at the Aphids soldier aphid expense of its own reproduction will suffer no evolutionary cost

8 Altruism in clonal organisms 0.20 Horns were larger at higher temperature, Length of horns (mm) typical of when butterfly larvae are active ºC 20ºC

9 Sociality more common in Hymenoptera Hymenopterans are haplodiploid = females are diploid, while males Mother% Father% are haploid (essentially, Chromosomes% unfertilised eggs. Fer2liza2on% Consequently, females are more closely related to their sisters than Unfer2lized% egg% their daughters Sons% Daughters%

10 Sociality more common in Hymenoptera Ants Relatedness among individuals of the hymenoptera Mother Father Sister Brother Son Daughter Female Bees Male Wasps

11 Hamilton s rule doesn t explain everything Some bees are solitary Termites are diploid

12 Benefits of cooperative nesting Solitary queen OR two sisters share a nest α female lays eggs, β passes on genes indirectly Solitary queens Joint nesters Polistes metricus Alpha Beta Relative nesting success Average relatedness to offspring Relative gene contribution

13 Benefits of cooperative nesting Number of cells 150 single multiple removal Number of failed colonies Size at removal Size at end 0 Single Multiple Polistes dominulus Nest with multiple foundresses were larger and less likely to fail

14 Helpers insure against adult mortality Experiment Comparison between the number of surviving brood of experimental colonies with control colonies that were the same size either: i) before the removal (both size = n) or Liostenogaster sp. ii) after removal (n - r, where r = number of brood after removal).

15 Helpers insure against adult mortality The number of surviving brood Un-manipulated (control) Experimental colonies colonies (size = n-r) Large colony Pre-removal (size=n) Same Post-removal (size=n-r) Greater Liostenogaster sp. Small colony Less Same

16 How much care to give? Predictions High-ranking individuals should work less hard than low-ranking individuals Individuals of a given rank should work less hard in larger groups Liostenogaster sp.

17 How much care to give? Higher ranking individuals did 1.0 less work Workers whose rank was experimentally raised, subsequently worked less hard, across all group sizes Helping effort Rank

18 Answer: Worked less hard than lower-ranked workers. Higher-ranked workers worked less hard than lower-ranked workers. In addition, experimentally reducing the total numbers of workers caused each individual worker to spend more time foraging.

19 Preferred sex ratios of queens & alates 3" How much of a workers effort should be invested in male and female alates? Mother Father Sister Brother Son Daughter Female Male Stable"female:male"sex"ra8o" 2" 1" Workers" Queen" 0" 1" 5" 9" 13" 17" Number"of"queen"ma8ngs"

20 Preferred sex ratios & mating frequency Primary & secondary sex ratios in Formica exsecta Category Singly mated Multiply mated p Proportion of female eggs ± ± 0.3 > ± ± 0.3 >0.5 Proportion of female pupae ± ± 0.2 < ± ± 0.3 <0.001

21 Preferred sex ratios & mating frequency We won! Hooray!

22 Summary There are many reasons for individuals to cooperate, leading to complex eusocial colonies Where there is cooperation, there is also conflict

23 PDF Citations Slide 1 _MG_2581 peacock spider Maratus volans by Jurgen Otto ( Reproduced with permission from Jurgen Otto. Slide 3 Slide 7 a) Polistes major (Paper Wasp) ( by Bob Peterson (CC BY-SA 2.0) b) Paper Wasp Polistes dominula (m) ( by Harald Hoyer (CC BY-SA 2.0) c) Happy biodiversity day ( by Derek Visser (CC BY-SA 2.0) d) Eastern Carpenter Bee (Xylocopa virginica) ( by Bob Peterson (CC BY-SA 2.0) Aphids by Mark Elgar (C) Mark Elgar Slide 8 Graph by Mark Elgar based on data from (Hattori, M., Osamu, K. & Itino, T) Soldiers with large weapons in predator-abundant midsummer: phenotypic plasticity in a eusocial aphid. Evolutionary Ecology. 27:5 (2013) pp Springer. Slide 9 Sociality more common in Hymenoptera diagram by Mark Elgar (C) The University of Melbourne Slide 10 a) Army ants ( by Geoff Gallice (CC BY 2.0) b) Bumble Bee on lavender by Milly Formby (C) Milly Formby c) Community < by Ian Sane (CC BY 2.0) d) Table by Mark Elgar (C) University of Melbourne Slide 11 a) Athidium February ( By Alvesgaspar (Own work) (CC-BY-SA-3.0), via Wikimedia Commons b) "Angkor Termites ( )" ( by Thomas Brown (Uploaded by mgiganteus ) (CC-BY-2.0), via Wikimedia Commons

24 Slide 12 a) "ximg_7604" by David Hill (BY CC 2.0) b) Metricus Paper Wasp (Polistes metricus) at trailhead by Jason Sturner (CC BY 2.0) c) Table by Mark Elgar derived from data in (Metcalf, R. A & Whitt, G. S.) Intra-Nest Relatedness in the Social Wasp Polistes metricus. Behavioral Ecology and Sociobiology. Vol. 2 (1977) pp Springer-Verlag Slide 13 a) Polistes dominulus-nest-14 ( b y Eugene Zelenko (Own work) (CC-BY-SA-3.0), via Wikimedia Commons b) Graphs by Mark Elgar based on data from (Tibbetts, E. A & Reeve, H. K.) Benefits of foundress associations in the paper wasp Polistes dominulus: increased productivity and survival, but no assurance of fitness returns. Behaviral Ecology. 14:4 (2003) pp International Society for Behavioral Ecology. Slide 14 Liostenogaster vechti ( By Turillazzi Stefano (Own work) (CC-BY-SA-3.0), via Wikimedia Commons Slide 15 a) Table by Mark Elgar based on concepts expressed in (Field, J., Shreeves, G., Sumner, S. & Casiraghi, M.) Insurance-based advantage to helpers in a tropical hover wasp. Nature. Vol. 404 (2000) pp Macmillan Magazines Ltd. b) Liostenogaster vechti ( By Turillazzi Stefano (Own work) (CC-BY-SA-3.0), via Wikimedia Commons Slide 16 Liostenogaster vechti ( By Turillazzi Stefano (Own work) (CC-BY-SA-3.0), via Wikimedia Commons Slide 17 Graph by Mark Elgar based on data from (Field, J., Cronin, A. & Bridge, C.) Future fitness and helping in social queues. Nature. Vol. 441 (2006) pp Nature Publishing Group. Slide 19 a) Table and graph by Mark Elgar based on data from (Trivers, R. L. & Hare, H.) Haplodiploidy and the Evolution of the Social Insects. Science. 191:4224 (1976) pp American Association for the Advancement of Science. b) Ants by Milly Formby (C) University of Melbourne

25 Slide 20 a) "food-exchange by southern wood ants" by gbohne (CC BY-SA 2.0) b) Table by Mark Elgar based on data from (SundstrÖm, L., Chapuisat, M. & Keller, L.) Conditional Manipulation of Sex Ratios by Ant Workers: A Test of Kin Selection Theory. Science. 274:5289 (1996) pp American Association for the Advancement of Science. Slide 21 a) Ants by Milly Formby (C) University of Melbourne b) "XboxBalloons" ( by Open Clipart Gallery; Blackwatch21; Pbroks13 (File:Balloons-aj.svg; en:file:xboxballoons.gif) [Public domain], via Wikimedia Commons