Syrphid community in organic olive groves: can morphospecies be used as surrogates for species?

Syrphids are known as biological control agents of hemipteran pests and, in the olive grove, several species have been identified as predators of Euphyllura olivina (Costa). The objectives of this work were: (1) to study the syrphid community in organic olive groves and (2) to test the potential for the use of syrphid morphospecies as a surrogate for species. The field work was conducted in two organic olive groves located near Mirandela (Northeast of Portugal). The sampling period occurred in two seasons, from the middle of August to the end of October 2009 and from the beginning of April to the end of July 2010. Syrphids adults were separated in morphospecies by a parataxonomist in accordance with their morphological differences. Then, the species were identified by a taxonomist. The number of individuals collected was 64 in 2009 and 27 in 2010, for a total of 91. The morphological identification showed the presence of 12 morphospecies that corresponded to six species: Episyrphus balteatus (De Geer) the most abundant with 51.7% of relative abundance, followed by Sphaerophoria scripta (L.) with 23.1% and Eupeodes corolla (Fabricius) with 18.6%. The proportion of correctly assigned morphospecies to taxonomic species was 3.3%. However, during the identification, a 93.4% splitting and a 3.3% lumping error occurred. This study showed that species identification was relatively difficult when based only on parataxonomic traits, requiring a careful examination of characteristics such as the size of the eyes and their hair, the form of the antennae, the humeral plate and the squama, as well as the femur color and the size of the bands on the abdomen.