Leaf herbivory and fluctuating asymmetry as indicators of mangrove stress

Fluctuating asymmetry (FA), a widely used measure of developmental instability in plants and animals, which describes random differences in size and/or shape between the two sides of a bilateral character. We used FA as a tool to detect stress in three mangrove species (Avicennia germinans, Laguncularia racemosa, Rhizophora mangle), growing in both disturbed and conserved habitats in the Atlantic coast of Mexico. In this region, disturbed habitats are the result of deforestation, livestock, tourism and agriculture activities. Twenty plants of each species were sampled in each of four sites (two disturbed and two conserved) and levels of FA, proportion of individuals with herbivory, proportion of leaves with damage, and leaf area removed by herbivores were evaluated. In disturbed habitats, regardless of plant species, more plants were attacked by insects, more leaves were damaged, and more leaf area was removed by herbivores, indicating higher overall damage to plants. We detected that FA levels varied significantly amongst mangrove species, they were higher in disturbed compared to conserved habitats, indicating the importance of FA as a monitoring tool of mangrove stress. A positive relationship between FA and herbivory levels also indicates that herbivores might be a source of stress.