Life histories, secondary production, and microdistribution of heptageniid mayflies (Ephemeroptera) in a tropical forest stream

摘要: The ecology of five species heptageniid mayflies was investigated in Tai Po Kau Forest Stream (TPKFS), New Territories, Hong Kong, over a two-year period (1977-79). Quantitative benthic samples were taken from different microhabitats the stream on 47 occasions and, combination with light-trap catches adult mayflies, used as basis for investigating life-history patterns and estimating secondary production. Electrogena sp. (49.8 individuals 0.5 m−2; 60% total densities) Cinygmina (15.7 m−2) most abundant heptageniids TPKFS, followed by Epeorus (9.1 m−2). Iron Paegniodes cupulatus, which present relatively low densities, made up < 10% abundance. In terms mean biomass (1977-79), equally important (10.3 vs. 10.5 mg ash-free dry weight (AFDW m−2), while ranked third (6.8 AFDW There was, however, considerable inter-year variation standing stocks: densities 1977-78 (respectively) eight nine times greater than 1978-79, P. cupulatus exhibited converse trend, more twice high three 1978-79. Heptageniid abundance TPKFS seemed to follow an annual pattern wet-season decrease dry-season increase, but this tendency apparent some (e.g. sp.) others sp.). life histories unclear. All showed rather stable larval size-frequency distributions throughout study period, indicative asynchronous growth continuous recruitment. Adult flight periods did not exhibit strong seasonality. Calculations production based upon conservative assumption that each univoltine, multivoltine may have been possible these tropical mayflies. Total 1977-79 212.0 m−2, slightly higher during 1978-79 (225.0 202.1 Inter-year variations reflected biomass: 7.9 2.7 4.6 greater. As consequence variations, species-specific decreased order > 1977-78, sequence For whole cupulatus. Production:biomass (P:B) ratios varied 4.8 (Cinygmina sp., 1977-78) 11.1 (Iron 1977-78), P:B (1977-79) Production calculations are highly sensitive assumptions about voltinism therefore be significant underestimates. Epeorus midstream numerous close banks. microdistribution less distinct, larvae favour microhabitats. Multivariate statistics revealed all (except influenced significantly sediment grain-size characteristics algae or detritus, proportion (4-14%) accounted low.