Ecology of Tigriagrion Aurantinigrum calvert in response to variations in environmental conditions (Zygoptera: Coenagrionidae)

Abstract

The daily activity patterns, behaviour and population dynamics in Zygoptera are thought to be affected by the physical conditions of the environment. How and why the sp. reacts to those conditions is determined mainly by its bionomic characteristics. Here, an auto-ecological study is performed of T. aurantinigrum, in an attempt to clarify its responses to physical conditions. It is suggested that T. aurantinigrum could fit, with a few assumptions, in the “female-control” classification of odon. mating system. Some interactions were observed between individuals, but it is assumed that these play a role in sex recognition, rather than in territorial contests. The results indicate that this sp. is affected by the following physical conditions: the monthly rain fall, which has a positive effect on the abundance (with the possible exception of the heavy rain months); the water flow velocity, which seems to define a limit of its occurrence; and the daily variation in temperature,which seems to induce the sp. to restrict its activity to the hottest period of the day, as expected from a “thermal conformer”. T. aurantinigrum appears to be affected by small scale variations of environmental variables, as observed by the differences of its abundance at the 3 different sites of this study. Under conditions of the current “forest-to-pasture” conversion that is common in the Brazilian Atlantic Forest region, the sp. is expected to increase its abundance and to broaden its geographicalrange, although water body alterations could limit this process.