and physical acoustics can provide crucial insights into the evolution of
acoustic communication.
Second, why adopt an evolutionary perspective? Researchers interested
in the mechanisms underlying vocal production and/or auditory perception
might argue that the ultimate evolutionary forces structuring a communication system offer little insight into the proximate morphological and
neuronal mechanisms that underlie acoustic behavior. One reason that an
evolutionary viewpoint is valuable is that many aspects of animal morphology and behavior may appear nonoptimal from an engineering perspective but can be understood as an optimal solution to a problem, given
a certain phylogenetic starting point and well-defined developmental, physical, or mechanistic constraints. No animal has wheels, despite the fact that
wheels would be adaptive for large grassland herbivores. The absence of
wheels results from developmental and physiological constraints operating
over evolutionary time. More prosaically, small body size will forever
prevent many species from exploiting infrasonic communication, which
might otherwise be optimal in terms of attracting mates but not predators.
An evolutionary perspective also encourages an exploration of interspecific
similarities and differences, providing a comparative framework to address
many mechanistically based questions that have already been answered by
experiments of nature. Could an animal with a larynx half the size of its
body still breathe and eat? The fruit bat Hypsignathus monstrosus shows us
that the answer is yes (see Section 2.2.2). What is the relationship between
perceptual and production systems in the evolution of acoustic communication? Ryan’s (Ryan 1985, 1988; and Ryan and Kime, Chapter 5) and
Gerhardt’s (1982, 1991) elegant comparative work on anuran bioacoustics
has increased our understanding of the coevolution of production and perception mechanisms in frogs as well as anuran evolution more generally.
Finally, certain adaptive problems are so persistent and pervasive that they
have spawned numerous, independently evolved solutions, and we need
to identify these powerful evolutionary forces if we are to understand
the broad patterns of diversity seen in animal behavior and morphology.
Tracheal elongation in birds, which has independently evolved at least eight
times, provides a possible example that will be discussed below.
1.1. Evolutionary Constraints
The notion of restrictions or constraints on evolution has been with us since
Darwin (1859, Chapter 13). Although most researchers agree on their
importance, detailed analysis and quantification of the role of evolutionary
constraints has proved an elusive goal (see Maynard Smith et al. 1985;
Carroll 1997), and many different classifications of constraints have been
proposed. In this chapter, we will distinguish functional constraints from
phylogenetic constraints. Functional constraints result from physical,
anatomical, and physiological factors that limit the range of possible forms
68
W.T. Fitch and M.D. Hauser
acoustic communication.
Second, why adopt an evolutionary perspective? Researchers interested
in the mechanisms underlying vocal production and/or auditory perception
might argue that the ultimate evolutionary forces structuring a communication system offer little insight into the proximate morphological and
neuronal mechanisms that underlie acoustic behavior. One reason that an
evolutionary viewpoint is valuable is that many aspects of animal morphology and behavior may appear nonoptimal from an engineering perspective but can be understood as an optimal solution to a problem, given
a certain phylogenetic starting point and well-defined developmental, physical, or mechanistic constraints. No animal has wheels, despite the fact that
wheels would be adaptive for large grassland herbivores. The absence of
wheels results from developmental and physiological constraints operating
over evolutionary time. More prosaically, small body size will forever
prevent many species from exploiting infrasonic communication, which
might otherwise be optimal in terms of attracting mates but not predators.
An evolutionary perspective also encourages an exploration of interspecific
similarities and differences, providing a comparative framework to address
many mechanistically based questions that have already been answered by
experiments of nature. Could an animal with a larynx half the size of its
body still breathe and eat? The fruit bat Hypsignathus monstrosus shows us
that the answer is yes (see Section 2.2.2). What is the relationship between
perceptual and production systems in the evolution of acoustic communication? Ryan’s (Ryan 1985, 1988; and Ryan and Kime, Chapter 5) and
Gerhardt’s (1982, 1991) elegant comparative work on anuran bioacoustics
has increased our understanding of the coevolution of production and perception mechanisms in frogs as well as anuran evolution more generally.
Finally, certain adaptive problems are so persistent and pervasive that they
have spawned numerous, independently evolved solutions, and we need
to identify these powerful evolutionary forces if we are to understand
the broad patterns of diversity seen in animal behavior and morphology.
Tracheal elongation in birds, which has independently evolved at least eight
times, provides a possible example that will be discussed below.
1.1. Evolutionary Constraints
The notion of restrictions or constraints on evolution has been with us since
Darwin (1859, Chapter 13). Although most researchers agree on their
importance, detailed analysis and quantification of the role of evolutionary
constraints has proved an elusive goal (see Maynard Smith et al. 1985;
Carroll 1997), and many different classifications of constraints have been
proposed. In this chapter, we will distinguish functional constraints from
phylogenetic constraints. Functional constraints result from physical,
anatomical, and physiological factors that limit the range of possible forms
68
W.T. Fitch and M.D. Hauser