The Comparative Method Flashcards
Describe John Crook’s 1964 initial observations
- Southern masked weavers and Village weavers founded polygamous societies that nested in colonies
- Red-headed weaver existed in monogamous, highly dispersed territories with cryptic nests
Describe John Crook’s 1954 subsequent observations with regards to mating system
- more likely to be monogamous if the food source was found in insects
- more likely to be polygamous if the source was seeds
- 22:1 monogamous to polygamous societies feeding on insects
- 2:26 feeding on seeds
Describe John Crook’s 1954 subsequent observations with regards to social system
- insects led to more solitary social systems
-seeds led to more grouped and colonial ones (21:2) solitary to grouped/colonial with insects as a food source; 0:33 for seeds)
Describe John Crook’s 1964 conclusions
- if a bird species ate insects, it was more likely to be monogamous and solitary
- if it fed on seeds, it was more likely to be polygamous and grouped or colonial
Describe John Crook’s 1964 explanation for his conclusions
- since insects are a sparse but evenly distributed food source, breeding was more efficient in separate places with solitary monogamous pairs
- since seeds were rare temporally but hugely abundant, group foraging, and a colonial social system was more efficient
- colonial lifestyle was more likely to induce male competition, and therefore sexual polygamy would be introduced into the system
Describe the faults with John Crook’s 1964 experimental method
- lack of an a priori alternative or competing hypothesis
- no ecological quantification of his variables by testing his data alongside another
Describe primate classification
- in terms of their sexual dimorphism
- calculated as male weight divided by female weight
What is the sexual dimorphism ratio of the Indri
1.0
What is the sexual dimorphism ratio of the Macaques
1.5
What is the sexual dimorphism ratio of the Papio Baboon
2.0
Describe Clutton-Brock and Harvey’s 1977 experiment
- two alternative hypotheses to explain the variation in sexual dimorphism observed between primate species
i) caused by niche differentiation in order to reduce competition
ii) selected for sexually - quantify ecological variables against the sex ratio in a breeding group, measured as the number of females per male
What was the problem with Clutton-Brock and Harvey’s 1977 experiment?
statistical analytical assumption of species independence
Describe Grassland Weaver populations
87.5% of the organisms are found in the Euplectes genus
Describe non-independent species
- closely related species would exhibit commonly descended traits and features and corresponding lifestyles
- enhanced similarity relative to independently evolved organisms
Why can’t non-independent datapoints be used in statistical analysis
- pseudoreplication
- significance boundaries more easy to reach, fallibly
What is pseudoreplication
experiments in which replicate number, and therefore sample size is inflated
Describe the comparative method
- takes independent contrasts between sister taxa
- uses this difference between species as the datapoint
- accounts for the lack of independence among sister taxa by comparing between them
- beneficial in its removal of unknown variation
What does the comparative method necessitate?
- artificial reconstruction of ancestors in order for accurate comparison
- a perfect pylogeny is beneficial
Comparative method NB
Calculation of the independent contrast must be performed in the same direction across the study, to make sure opposite results are not obtained.
Describe the reproductive behaviours of parasitic fig wasps
- highly specific: each fig species has its own partner wasp
- pollen-laden female wasp enters an unripened fig
- pollinates the flowers
- lays her eggs
- is trapped and dies.
- flowers upon which her larvae have been deposited form galls
- flowers which have not produce seeds
- galls produce both male and female wasps
- after a month of development, the wingless males fertilise the females and ultimately never leave the fig
- the females leave the galls, sometimes collecting pollen from the mature male flowers within the fig and exiting via a tunnel
- begin search for new fruits in which to lay their own eggs
Describe male parasitic fig wasp morphology
- tiny antenna and eyes
- tradeoff
- more energy is inputted into their cleft chin mating organ
Describe what happens if parasitic female fig wasps enter a fig without having first collected pollen
- fig will not grow seeds
- may be aborted by the tree
- any offspring lain in the fig will die when it drops
Describe comparative analysis of conflict of pollinating and non-pollinating wasps
- characteristics are grouped phylogenetically
- pollinators do not fight
- non-pollinators fight to varying degrees
- violence is high when female density development in the fig is low
Explain the utilisation of game theory in comparative analysis of conflict in pollinating and non-pollinating wasps
- female resource is limited
- greater benefit to fighting, rather than fleeing for alternative female acquisition
Describe some species of non-pollinating wasps
- males are winged and highly armoured
- adapted to fighting behaviours
- frequently undergo morbidity through decapitation in combat
Describe the advantages of the comparative method
- illustrates broad and general trends and relationships across species
- amenability of their hypotheses
the experimental studies still provide advantages in terms of their ability to detail individual behaviour, and their testability over their observationality.
