Female mate choice in treefrogs : static and dynamic acoustic criteria

Abstract

Patterns of variation in the acoustic properties of advertisement calls of several species of treefrogs (family Hylidae) are related to patterns of female preferences for these same properties. Proper- ties were unequivocally classified as static or dynamic based on within-male variability during bouts of calling. Static properties are highly stereotyped within males and between males in natural populations. Dynamic properties often change by as much as 100% during single bouts of calling; dynamic properties are usually much more variable among males in natural populations than are static properties. An analysis of the calling performance of individual males over the course of a breeding season indicated that at least one dynamic property, pulse number (or call duration) in Hyla versicolor, was sufficiently repeatable to differentiate between males. Playback experiments that employed synthetic calls showed that: (1) females exhibit patterns of preferences that should result in selection that is stabilizing or weakly directional on static properties, and highly directional on dynamic properties; and (2) the overall attractiveness of a signal is affected by variation in both static and dynamic properties. Similar results were found in laboratory and field studies of other taxa, primarily anurans and insects. Patterns of variability in call properties of males and in female preferences are discussed in terms of proximate mechanisms and theoretical models of the evolution of female choice. My