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Intersexual Selection (intersexual + selection)

Distribution by Scientific Domains
Life Sciences100%

Selected Abstracts

Intra- and Intersexual Selection for Multiple Traits in the Peacock (Pavo cristatus)

ETHOLOGY, Issue 9 2005
Adeline Loyau
Animal communication involves a multitude of signals ranging from morphological to behavioural traits. In spite of the diversity of traits used in animal signalling, most studies of sexual selection have focused on single male traits. Moreover, the two forces of sexual selection (male,male competition and female preference) may target different traits and favour the diversification of male signalling. Still, little is known on the combined effects of intra- and intersexual selection on the evolution of multiple signals. The peacock is often cited as one of the best examples of the strength of sexual selection in producing exaggerated traits. Here, we investigated traits under intra- and intersexual selection in a population of free-ranging common peafowl. Peacocks with longer trains and tarsi were more likely to establish a display territory in a central position within the lek and had a higher number of intrusions and agonistic interactions. These traits appeared therefore to be under intrasexual selection. Female selection was assessed as the number of copulations. Mating success was positively correlated with behavioural traits (display activity) and with train ornamentation (number and density of ocelli) suggesting that females use multiple cues during mate selection. Therefore, intra- and intersexual selection seem to operate on different sets of traits. Overall, our results stress the role of multiple receivers on the evolution of multiple signals. [source]

Anti-Predator Signals as Advertisements: Evidence in White-Throated Magpie-Jays

ETHOLOGY, Issue 6 2009
Jesse M. S. Ellis
Calls and displays elicited by predators usually function as alarms or to inform predators of their detection. However, predator encounters may afford some individuals the opportunity to demonstrate quality or signal their availability. Here, I report on a class of vocal signals produced in predator-elicited displays that share many characteristics with sexually selected song. White-throated magpie-jays (Calocitta formosa) display at low-threat predators while producing ,loud display calls' (LDCs). I use this term because the calls occur primarily in two display contexts (see below) though occasionally in other contexts as well. Such calls and displays are primarily produced by males, and also occur in one other context, at dawn. Playback experiments showed that despite being elicited by predators, males were more likely than females to respond to LDCs, and more likely to respond when their mate was fertile. Over 134 different call types were produced in over 200 displays by 34 males; the largest minimum repertoire size was 67. Presentations of taxidermic raptor mounts elicited some LDCs, but fewer calls and lower diversity than at dawn or in predator approach displays. The male bias and high diversity suggest that LDCs are an outcome of intersexual selection, while their elicitation by predators suggests an alarm function. I propose that male magpie-jays use predator encounters as opportunities to advertise their presence and availability as mates; they use LDCs as songs. Such a communication system seems to have been favored by the unusual social system of magpie-jays, in which female groups defend territories and males have little opportunity to defend resources for mate attraction, forcing them to advertise when females are paying the most attention, during predator encounters. [source]

Intra- and Intersexual Selection for Multiple Traits in the Peacock (Pavo cristatus)

ETHOLOGY, Issue 9 2005
Adeline Loyau
Animal communication involves a multitude of signals ranging from morphological to behavioural traits. In spite of the diversity of traits used in animal signalling, most studies of sexual selection have focused on single male traits. Moreover, the two forces of sexual selection (male,male competition and female preference) may target different traits and favour the diversification of male signalling. Still, little is known on the combined effects of intra- and intersexual selection on the evolution of multiple signals. The peacock is often cited as one of the best examples of the strength of sexual selection in producing exaggerated traits. Here, we investigated traits under intra- and intersexual selection in a population of free-ranging common peafowl. Peacocks with longer trains and tarsi were more likely to establish a display territory in a central position within the lek and had a higher number of intrusions and agonistic interactions. These traits appeared therefore to be under intrasexual selection. Female selection was assessed as the number of copulations. Mating success was positively correlated with behavioural traits (display activity) and with train ornamentation (number and density of ocelli) suggesting that females use multiple cues during mate selection. Therefore, intra- and intersexual selection seem to operate on different sets of traits. Overall, our results stress the role of multiple receivers on the evolution of multiple signals. [source]

Genetic divergence does not predict change in ornament expression among populations of stalk-eyed flies

MOLECULAR ECOLOGY, Issue 12 2005
JOHN G. SWALLOW
Abstract Stalk-eyed flies (Diptera: Diopsidae) possess eyes at the ends of elongated peduncles, and exhibit dramatic variation in eye span, relative to body length, among species. In some sexually dimorphic species, evidence indicates that eye span is under both intra- and intersexual selection. Theory predicts that isolated populations should evolve differences in sexually selected traits due to drift. To determine if eye span changes as a function of divergence time, 1370 flies from 10 populations of the sexually dimorphic species, Cyrtodiopsis dalmanni and Cyrtodiopsis whitei, and one population of the sexually monomorphic congener, Cyrtodiopsis quinqueguttata, were collected from Southeast Asia and measured. Genetic differentiation was used to assess divergence time by comparing mitochondrial (cytochrome oxidase II and 16S ribosomal RNA gene fragments) and nuclear (wingless gene fragment) DNA sequences for c. five individuals per population. Phylogenetic analyses indicate that most populations cluster as monophyletic units with up to 9% nucleotide substitutions between populations within a species. Analyses of molecular variance suggest a high degree of genetic structure within and among the populations; > 97% of the genetic variance occurs between populations and species while < 3% is distributed within populations, indicating that most populations have been isolated for thousands of years. Nevertheless, significant change in the allometric slope of male eye span on body length was detected for only one population of either dimorphic species. These results are not consistent with genetic drift. Rather, relative eye span appears to be under net stabilizing selection in most populations of stalk-eyed flies. Given that one population exhibited dramatic evolutionary change, selection, rather than genetic variation, appears to constrain eye span evolution. [source]