No abstract

In species where males have several ornaments for mate attraction, each ornament may coevolve with a different female preference. Alternatively, multiple ornaments may be sexually selected for because they stimulate the same, single, female preference. In the latter case, measures of preferences for different ornaments are essentially measures of the same phenotypic character and, thus, will be strongly pleiotropic, whereas no such expectation exists for multiple preferences. We selected directly up and down on two visual ornaments, orange and black coloration, in male guppies (Poecilia reticulata) in order to impose indirect selection on the female preference or preferences for these ornaments. Preferences for the two colors responded in a pattern similar to the response of the ornaments themselves. That female preferences for orange and for black in this guppy population are able to respond to selection more or less independently, suggests that they are probably two different characters in an evolutionary sense. Each of these preferences appears to be genetically correlated with the respective ornament.

No abstract

Acoustic signals are commonly utilized for communication over long distances by a variety of animal taxa, from butterflies (Yack et al., 2000) to elephants (McComb et al., 2003). However, one of the major predicaments plaguing long-range signallers is that sounds become progressively more degraded the further they propagate. The transmission of acoustic signals through any given environment results in modification of the signal amplitude and fidelity over distance. Loss of amplitude, resulting from spherical spreading and also from absorption and scattering of sound waves (excess attenuation), diminishes the range at which receivers can detect a signal, while loss of fidelity, incorporating frequency-dependent attenuation, irregular amplitude fluctuations and reverberations, reduces the ability of receivers to accurately recognize a signal in the event it is detected. A combination of changes in both amplitude and fidelity contributes to overall patterns of signal degradation.The rate of acoustic signal degradation, and subsequently the range at which sounds can be used effectively for communication purposes, is dependent upon numerous factors. These include spectral and temporal properties of the signal itself (Wiley and Richards, 1978), behavioural modifications of the animal during signalling, such as calling from preferential heights and locations (Bennet-Clark, 1987;Keuper et al., 1986), and external properties of the local environment, incorporating vegetation type (Lang, 2000), meteorological conditions (Garstang et al., 1995), and acoustic interference from other organisms (Wollerman, 1999).The acoustic adaptation hypothesis emanated largely from the work of Morton (1975) and Hansen (1979) and was conceived as a means of means of investigating the relationship between animal vocalizations and ecological factors. This hypothesis was based on the observation that environmental factors may heavily influence the evolution of long-range acoustic signals by imposing selection pressures that act to modify the sound properties of signals in order to maximize their broadcast range and the number of potential receivers (Endler, 1992;Forrest, 1994;Morton, 1975). This could lead to a matching between signal and environment, such that signals transmit optimally in native habitats and, conversely, perform poorly when broadcast through non-native habitats.Studies concerning the propagation of long-range acoustic signals in relation to the environment in which they are transmitted have yielded mixed results. The acoustic adaptation hypothesis for enhanced transmission efficiency in native habitats has garnered support primarily from studies on avian and primate taxa. Birds inhabiting different It has been hypothesized that the physical properties of the environment exert selection pressure on long-range acoustic communication signals to match the local habitat by promoting signal characteristics that minimize excess attenuation and distortion. We tested this in a unique family of bladder grasshoppers notable for produci...

Females of the Lake Malawi cichlid Pseudotropheus lombardoi preferred males with one eggspot, the natural number, on their anal fin compared to males with two eggspots which had been artificially manipulated in number. Furthermore by manipulating the size of the eggspot, it was found that females preferred males with one large eggspot to males with one small eggspot. These results indicate that female preferences are responsible for the single eggspot in P. lombardoi and that this may be linked to species recognition as females of closely related species appear to exhibit different preferences for male eggspots. 2002 The Fisheries Society of the British Isles