Developmental time and thorax length differences between the catiphilc species Drosophila buzzatii and D. koepferae reared in different natural hosts

FANARA JUAN JOSÉ; MENSCH JULIÁN; FOLGUERA GUILLERMO; HASSON ESTEBAN

EVOLUTIONARY ECOLOGY

Kluwer Academic Publishers

Año: 2004 vol. 18 p. 203 - 214

0269-7653

Drosophila buzzatii and Drosophila koepferae are two cactophilic sibling species whoseranges partially overlap in Northwestern and Western Argentina. Both species can utilize thedecaying tissues of both Opuntia and columnar cacti as breeding sites. Though D. buzzatii andD. koepferae are not differentially attracted to Opuntia and columnar hosts, the composition of the communities of flies emerging from natural substrates of both cacti differed significantly in anatural population. The objective of this paper is to analyze whether intra and/or interspecificcompetition affects development time and thorax length in D. buzzatii and D. koepferae when both species are reared in single and mixed species culture and fed with semi-natural media prepared with fermenting materials of Opuntia sulphurea (tuna) and Trichocereus terschekii (cardón). Our results showed that both traits differ significantly between flies raised in different hosts and that differences between D. koepferae and D. buzzatii species for both thorax length and development time depend on the type of culture (mixed vs. single species). In addition, the host by type of culture interaction was significant. We also observed thorax length differences between Drosophila species and type of culture. Our present data suggest that the effect of intra and interspecific competition varied between the two traits investigated and between species. However, competition alone cannot explain the differential pattern of resource utilization shown by D. buzzatii and D. koepferae in the natural population studied.