Fluctuating asymmetry as an indicator of stress: paradigm or conservation tool?

lndividual and population levels of fluctuating asymmetry (FA) often correl ate positively with estimates of environmental and genetic stress. These re lationships have promoted the widely-held belief that organisms with enhanc ed FA levels may act as sensitive biomonitors in natural populations under threat. However, a number of recent papers have challenged this concept by revealing major inconsistencies in the reported asymmetry-stress associatio n. By reviewing published results from our study of patterns of bilateral t rait asymmetry in seven Kenyan bird species, we test three hypotheses criti cal to the use of FA as stress monitor. Given the highly congruent findings across species and traits, we conclude that population FA-if accurately me asured and analysed-can function as a valuable tool in conservation. We fur ther discuss three potential causes for some of the inconsistencies reporte d in the literature.