Fluctuating asymmetry as a useful biomarker of environmental stress: a case of study with <I>Avicennia schaueriana</I> Stapf & Leechm. ex Moldenke (Acanthaceae)

Abstract

In bilaterally symmetrical organisms, fluctuating asymmetry (FA) provides a measure of environmentally induced departures from an ideal developmental program. FA should increase with increasing stress, and it should be exhibited at lower levels than those that could impact life history features. From the conservation point of view, it would be valuable to be one step ahead and detect the detrimental effect even earlier. We used the FA of stomata and salt-glands from leaves of Avicennia schaueriana species of two protected and two urbanized mangroves in Santa Catarina (Southern Brazil). We assess whether FA is sensitive enough to reflect the stresses in individuals exposed to varying environmental conditions. In order to do these measurements (counts), the leaves of Avicennia schauerianawere copied on acetate casts. Under the microscope, the leaf casts proved to be very clear, hence FA counts on the leaf casts were carried out perfectly. The highest FA values in both stomata and salt-glands were found in the central and landward sites of both urbanized mangroves. However, although the urbanized mangroves exhibited some high FA values, and the protected ones have some low ones, this was not always the case. Individual cases are discussed. Nevertheless, the results suggest that FA of stomata and salt-glands of Avicennia schaueriana leaves could be used as biomarker of environmental stress.