Ecology of the dragonflies at the westernmost spot of Africa, the island of Santo Antão, Cape Verde (Odonata)

Abstract

From 12 to 25 August 2009, the odonate fauna of Santo Antão, Cape Verde was surveyed by recording adults and collecting larvae and exuviae at 26 localities, mostly situated in the northwest of the island. Based on the results of this survey and literature data on the Cape Verdes it appears that the resident odonate fauna consists of only five species, namely Anax imperator, Crocothemis erythraea, Orthetrum trin- acria, Trithemis annulata and Zygonyx torridus. Three additional species, Anax ephippiger and Pantala flavescens, which were recorded as single adults in this study, and Sympetrum fonscolombii, which was previously recorded in another study, represent seasonal invaders that do not establish permanent populations on the island. Surprisingly, there is no zygopteran species recorded from the island, although a few occur on the neighbouring islands. The breeding habitats of the resident odonates on the island comprise short perennial stream sections in large wadi beds (‘ribeiras’) that are intensely used for agriculture, as well as artificial irrigation tanks. The odonate assemblage is very uniform, although Z. torridus prefers micro-habitats with flowing water and O. trinacria is found only in micro-habitats with fine sediments. In the absence of fish, crabs and large water beetles, the larva of A. imperator appears to be the top predator in freshwater habitats.

Keywords: Odonata, dragonfly, biodiversity, biogeography, Cape Verde Islands, Africa, residents, migrants

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