Instructor’s Manual
to accompany
Animal Behavior, Tenth Edition
John Alcock
Discussion Questions
Chapter 3: The Evolution of Social Behavior
Figure 3.3 shows a phylogeny (see page 31) of many bee species in the genus Lasioglossum,
with the social system of the species superimposed on the evolutionary tree. What is the
minimum number of times that eusociality (i.e., colonial species with obligately sterile
workers) has evolved in this group? How many times has eusociality been lost, either
completely or partially? (Partial loss of eusociality has occurred in those species that are
labeled “polymorphic,” which means that in these cases some populations form colonies
with sterile workers and others do not.) How might this phylogeny be used to criticize the
common value judgment that complex social systems are generally superior, and more
recently evolved, than simpler ones?
Answer: Eusociality at a minimum has evolved once in the group; the trait has been lost six
times, with species coming from eusocial lineages subsequently becoming solitary or parasitic.
The rate at which eusocial species lose their complex social structure supports the view that
highly social behavior is neither inherently superior to “simple,” less-social behavioral
organizations, nor is it necessarily more recently evolved than these simpler systems.
3.2 Given the differences in reproductive success for the three categories of male lazuli
buntings, how can we account for the evolutionary persistence of males with dull and,
especially, intermediate plumage?
Answer: An explanation for the persistence of males with less-favored plumage involves the
likelihood that these males are essentially forced by competition from brighter, more powerful
males and by female choice to make the best of a bad job. The disadvantaged males can employ
one of the several options available to all males, no matter what their appearance. If there are no
hereditary differences with respect to behavioral choices between males in the different plumage
categories, then selection cannot eliminate less-than-bright plumage from the population.
Instead, selection for flexible responses to other males of superior competitive ability can result
in males able to select the option that has the greatest fitness payoff for the specific conditions
they encounter, given their particular social status.
3.3 Lions live in prides composed of a variable number of females and males. Each pride
defends its own territory. If lion social groups form because of the benefits of communal
defense of a territory, what prediction follows about the interactions between prides of
different sizes? What additional predictions can you make about the size of prides and (1)
the quality of the defended habitat, (2) the survival of female pride members, and (3) the
This study source was downloaded by 100000857952895 from CourseHero.com on 01-19-2023 23:16:47 GMT -06:00
https://www.coursehero.com/file/13639025/Alcock10e-Ch03-Discussion-Questions/
to accompany
Animal Behavior, Tenth Edition
John Alcock
Discussion Questions
Chapter 3: The Evolution of Social Behavior
Figure 3.3 shows a phylogeny (see page 31) of many bee species in the genus Lasioglossum,
with the social system of the species superimposed on the evolutionary tree. What is the
minimum number of times that eusociality (i.e., colonial species with obligately sterile
workers) has evolved in this group? How many times has eusociality been lost, either
completely or partially? (Partial loss of eusociality has occurred in those species that are
labeled “polymorphic,” which means that in these cases some populations form colonies
with sterile workers and others do not.) How might this phylogeny be used to criticize the
common value judgment that complex social systems are generally superior, and more
recently evolved, than simpler ones?
Answer: Eusociality at a minimum has evolved once in the group; the trait has been lost six
times, with species coming from eusocial lineages subsequently becoming solitary or parasitic.
The rate at which eusocial species lose their complex social structure supports the view that
highly social behavior is neither inherently superior to “simple,” less-social behavioral
organizations, nor is it necessarily more recently evolved than these simpler systems.
3.2 Given the differences in reproductive success for the three categories of male lazuli
buntings, how can we account for the evolutionary persistence of males with dull and,
especially, intermediate plumage?
Answer: An explanation for the persistence of males with less-favored plumage involves the
likelihood that these males are essentially forced by competition from brighter, more powerful
males and by female choice to make the best of a bad job. The disadvantaged males can employ
one of the several options available to all males, no matter what their appearance. If there are no
hereditary differences with respect to behavioral choices between males in the different plumage
categories, then selection cannot eliminate less-than-bright plumage from the population.
Instead, selection for flexible responses to other males of superior competitive ability can result
in males able to select the option that has the greatest fitness payoff for the specific conditions
they encounter, given their particular social status.
3.3 Lions live in prides composed of a variable number of females and males. Each pride
defends its own territory. If lion social groups form because of the benefits of communal
defense of a territory, what prediction follows about the interactions between prides of
different sizes? What additional predictions can you make about the size of prides and (1)
the quality of the defended habitat, (2) the survival of female pride members, and (3) the
This study source was downloaded by 100000857952895 from CourseHero.com on 01-19-2023 23:16:47 GMT -06:00
https://www.coursehero.com/file/13639025/Alcock10e-Ch03-Discussion-Questions/
