Biomedical subjects

A Qvarnström

Publications and source records attributed to A Qvarnström.

7 recordsLinked to original sources

PubMed2006

Song similarity predicts hybridization in flycatchers.

Given that population divergence in sexual signals is an important prerequisite for reproductive isolation, a key prediction is that cases of signal convergence should lead to hybridization. However, empirical studies that quantitatively demonstrate links between phenotypic characters of individuals and their likelihood to hybridize are rare. Here we show that song convergence between sympatric pied (Ficedula hypoleuca) and collared flycatchers (F. albicollis) influence social and sexual interactions between the two species. In sympatry, the majority of male pied flycatchers (65%) include various parts of collared flycatcher song in their song repertoire (but not vice versa). Playback experiments on male interactions demonstrate that male collared flycatchers respond similarly to this 'mixed' song as to conspecific song. Long-term data on pairing patterns show that males singing a converged song attract females of the other species: female collared flycatchers only pair with male pied flycatchers if the males sing the mixed song type. From the perspective of a male pied flycatcher, singing a mixed song type is associated with 30% likelihood of hybridization. This result, combined with our estimates of the frequency of mixed singers, accurately predicts the observed occurrence of hybridization among male pied flycatchers in our study populations (20.45% of 484 pairs; predicted 19.5%). Our results support the suggestion that song functions as the most important prezygotic isolation mechanism in many birds.

Animal Communication↗

PubMed2004

Flycatcher song in allopatry and sympatry--convergence, divergence and reinforcement.

The theory of reinforcement predicts that natural selection against the production of unfit hybrids favours traits that increase assortative mating. Whether culturally inherited traits, such as bird song, can increase assortative mating by reinforcement is largely unknown. We compared songs of pied (Ficedula hypoleuca) and collared flycatchers (F. albicollis) from two hybrid zones of different ages with songs from allopatric populations. Previously, a character divergence in male plumage traits has been shown to reinforce premating isolation in sympatric flycatchers. In contrast, we find that the song of the pied flycatcher has converged towards that of the collared flycatcher (mixed singing). However, a corresponding divergence in the collared flycatcher shows that the species differences in song characters are maintained in sympatry. Genetic analyses suggest that mixed song is not caused by introgression from the collared flycatcher, but rather due to heterospecific copying. Circumstantial evidence suggests that mixed song may increase the rate of maladaptive hybridization. In the oldest hybrid zone where reinforcement on plumage traits is most pronounced, the frequency of mixed singing and hybridization is also lowest. Thus, we suggest that reinforcement has reduced the frequency of mixed singing in the pied flycatcher and caused a divergence in the song of the collared flycatcher. Whether a culturally inherited trait promotes or opposes speciation in sympatry may depend on its plasticity. The degree of plasticity may be genetically determined and accordingly under selection by reinforcement.

Animals↗

PubMed2001

Maternal effects, paternal effects and sexual selection.

Maternal and paternal effects can lead to complicated evolutionary dynamics, including evolution in the opposite direction to selection. Recent studies demonstrate that parental effects on sexually selected traits, as well as preferences for those traits, might be large. Although these findings are likely to have consequences for both the evolutionary dynamics and equilibria of sexual selection, theory is lacking. Because parents are expected to maximize their own fitness, rather than that of a specific offspring, the magnitude (and even direction) of parental effects are context dependent. By extension, this dynamic nature of parental effects might help to explain the maintenance of variation in many sexually selected traits.

Journal Article↗

PubMed2001

Context-dependent genetic benefits from mate choice.

Adaptive mate preferences are generally assumed to be static and open-ended, favouring the most extreme expression of display traits. In contrast to this view, three new studies show that genetic benefits from mate choice can be context-dependent. Thus, there might be short-term fluctuations in selection on mate preferences. The crucial question then is, are plastic mate preferences an optimal evolutionary outcome?

Journal Article↗

PubMed2000

Male-male competition and parental care in collared flycatchers (Ficedula albicollis): an experiment controlling for differences in territory quality.

Females are known to benefit from mate choice in several different ways but the relationship between these benefits has received little attention. The quality of resources provided by males, such as nest sites, and paternal care are often assumed to covary positively However, because the location of the nest affects the cost of parental care, these two benefits from mate choice can easily be confounded. To investigate the provisioning ability of successful competitors while controlling for differences in territory quality we removed early-settled pairs of collared flycatchers (Ficedula albicollis) and allowed replacement by later-arriving males or floaters (i.e.'poor competitors'). A control group of early-settled males (i.e. 'good competitors') had their females removed. Females paired to good competitors enjoyed a significantly higher reproductive success and tended to receive more parental assistance from their mates compared with females mated to poor competitors. Thus, some males seem able not only to compete successfully over resources but also to feed their offspring at a relatively higher rate. An alternative explanation, that poor competitors invested less in offspring quality in response to a lower share of paternity, could be rejected. The rate of extra-pair paternity did not differ between the two treatment groups. Our results suggest that male- male competition can sometimes facilitate female choice of superior care-givers. Thus, a female's benefit from choosing a competitive male may not be restricted to the quality of the resource he defends but can also include superior paternal care.

Animals↗

PubMed2000

Adaptive plasticity in mate preference linked to differences in reproductive effort.

There is abundant evidence for the existence of marked mate preferences in natural populations, but the occurrence of within-population variation in mate preferences has received little attention and is often regarded as nonadaptive deviation from the optimal norm. Here we show experimentally that the preference of female collared flycatchers Ficedula albicollis for male forehead patch size, a sexually selected trait, varies with the time of breeding, an environmental factor with strong effects on reproductive success. Contrary to expectations based on time-constrained choice models, only late-breeding females prefer males with a large patch size. The variation in mate preference matches a seasonal change in female reproductive success: long-term data reveal a positive relationship between female reproductive success and male patch size exclusively in late breeders. In addition, female reproductive effort, as assessed by clutch size, appears to be adjusted relative to both timing of breeding and male phenotype. We conclude that not only can mate preferences display adaptive plasticity within populations, but this plasticity can also be linked to differences in reproductive investment.

Adaptation, Physiological↗

PubMed1994

Infectious diseases, reproductive effort and the cost of reproduction in birds.

Reproductive effort can have profound effects on subsequent performance. Field experiments on the collared flycatcher (Ficedula albicollis) have demonstrated a number of trade-offs between life-history traits at different ages. The mechanism by which reproductive effort is mediated into future reproductive performance remains obscure. Anti-parasite adaptation such as cell-mediated immunity may probably also be costly. Hence the possibility exists of a trade-off between reproductive effort and the ability to resist parasitic infection. Serological tests on unmanipulated collared flycatchers show that pre-breeding nutritional status correlates positively with reproductive success and negatively with susceptibility to parasitism (viruses, bacteria and protozoan parasites). Both immune response and several indicators of infectious disease correlate negatively with reproductive success. Similar relations are found between secondary sexual characters and infection parameters. For brood-size-manipulated birds there was a significant interaction between experimentally increased reproductive effort and parasitic infection rate with regard to both current and future fecundity. It seems possible that the interaction between parasitic infection, nutrition and reproductive effort can be an important mechanism in the ultimate shaping of life-history variation in avian populations.

Animals↗