Fluctuating asymmetry increases with habitat disturbance in seven bird species of a fragmented afrotropical forest

We studied fluctuating asymmetry (FA) in the tarsus length of seven forest-restricted bird species, two of which are globally critically endangered, in three indigenous forest remnants of a recently fragmented, afrotropical biodiversity hot spot. Based on mixed regression analysis and an extension of Levene's test, individuals from the most degraded fragment showed four- to sevenfold higher asymmetry levels compared to those from the least degraded one, with intermediate levels in the moderately disturbed fragment. When comparing contemporary FA levels with measurements of museum specimens collected 50 years ago, we found highly significant increases in asymmetry in the most degraded fragment but no differences in the least degraded one. These strikingly parallel spatial and temporal patterns across species confirm that repeated measurements of FA can provide a sensitive early warning system for monitoring stress effects in highly threatened ecosystems.

[1]  L. Harris,et al.  Forest Fragmentation and the Conservation of Biological Diversity , 1992 .

[2]  C. Strobeck,et al.  Fluctuating Asymmetry: Measurement, Analysis, Patterns , 1986 .

[3]  S. Dongen.  Accuracy and power in the statistical analysis of fluctuating asymmetry: effects of between-individual heterogeneity in developmental instability , 1999 .

[4]  H. Ellegren,et al.  Fitness loss and germline mutations in barn swallows breeding in Chernobyl , 1997, Nature.

[5]  N. Lehman,et al.  Mitochondrial DNA Variability of the Gray Wolf: Genetic Consequences of Population Decline and Habitat Fragmentation , 1992 .

[6]  I. Hanski,et al.  Inbreeding and extinction in a butterfly metapopulation , 1998, Nature.

[7]  Geoffrey M. Clarke,et al.  Relationships Between Developmental Stability and Fitness: Application for Conservation Biology , 1995 .

[8]  T. Brooks,et al.  The conservation status of the forest birds of the Taita Hills, Kenya , 1998, Bird Conservation International.

[9]  Martin Kent,et al.  Vegetation Description and Analysis , 1993 .

[10]  A. Stattersfield,et al.  Endemic Bird Areas of the World: Priorities for Biodiversity Conservation , 1998 .

[11]  C. Mann.  AN AVIFAUNAL STUDY IN KAKAMEGA FOREST, KENYA, WITH PARTICULAR REFERENCE TO SPECIES DIVERSITY, WEIGHT AND MOULT , 1985 .

[12]  Stefan Van Dongen,et al.  How repeatable is the estimation of developmental stability by fluctuating asymmetry? , 1998, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[13]  H. Beentje,et al.  Kenya trees, shrubs, and lianas , 1994 .

[14]  R D Holt,et al.  Diverse and Contrasting Effects of Habitat Fragmentation , 1992, Science.

[15]  W. Newmark.  Tropical forest fragmentation and the local extinction of understory birds in the eastern Usambara Mountains, Tanzania , 1991 .

[16]  C M Gichuki,et al.  Long life-span and sedentariness of birds in North Nandi Forest, Kenya , 1990 .

[17]  R. Thornhill,et al.  Fluctuating asymmetry and sexual selection. , 1994, Trends in ecology & evolution.

[18]  D. H. Johnson,et al.  The use of multivariate statistics in studies of wildlife habitat , 1981 .

[19]  S. Van Dongen,et al.  The statistical analysis of fluctuating asymmetry: REML estimation of a mixed regression model , 1999 .

[20]  M. Whitlock,et al.  Fluctuating asymmetry does not increase with moderate inbreeding in Drosophila melanogaster , 1994, Heredity.

[21]  F. Allendorf,et al.  Fluctuating asymmetry as an indicator of stress: Implications for conservation biology. , 1989, Trends in ecology & evolution.

[22]  Luc Lens,et al.  Evidence for organism-wide asymmetry in five bird species of a fragmented afrotropical forest , 1999, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[23]  Alison J. Stattersfield,et al.  Birds to watch 2 : the world list of threatened birds , 1996 .

[24]  T. Brooks,et al.  Avian Biogeography of the Taita Hills, Kenya , 1998 .

[25]  Michael Whitlock,et al.  The heritability of fluctuating asymmetry and the genetic control of developmental stability , 1996, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[26]  A. Møller,et al.  Asymmetry, Developmental Stability, and Evolution , 1998 .

[27]  J. T. Curtis,et al.  The Use of Distance Measures in Phytosociological Sampling , 1956 .

[28]  P. Parsons,et al.  Fluctuating asymmetry: a biological monitor of environmental and genomic stress , 1992, Heredity.