Comparative Study of the Nymphal Biology of Two Coexisting Species of Mayflies (Insecta: Ephemeroptera) in a Mediterranean Stream in Southern Europe

We study the life history, nymphal feeding and secondary production of two leptophlebiid mayfly species (Habrophlebia eldae and Paraleptophlebia submarginata). They cohabit in a Mediterranean stream and present a very high niche overlap in terms of trophic resources. The life cycle was estimated using size‐frequency analysis of samples taken throughout a year. Both species have a similar but displaced period of the nymphal development. Secondary production was calculated by means of the size‐frequency method. Annual secondary production of P. submarginata is much higher than that of H. eldae (1.95 g DW m–2 year–1 vs. 0.17 g DW m–2 year–1), and presents a quite similar annual P/B ratio, but slightly higher in P. submarginata (6.97 in P. submarginata and 9.21 in H. eldae). The study of the gut contents revealed that they are mainly detritivores but, when larger they feed also on CPOM from leaves fallen in the stream. They present an almost total niche overlap in terms of food acquisition. However the previously mentioned shift in trophic resources utilization with size makes it possible that, because no similar size classes of each species are present at the same time, niche segregation exists between the two species. Though further studies are needed to confirm it, this could be the consequence of previous episodes of competition between them. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)