Stahl L. 2023
Deliry C. 2026 – Stahl L. 2023. - In : Odonates du Monde (Histoires Naturelles) [2004-2026] – Version 18126 du 26.08.2023. – odonates.net
[A contrôler !] |
Stahl L. 2023 - How does temperature and resource level affect competition in two species of dragonfly larvae ? - Thèse indépendante, Master de Biologie, Suède, sous la coord. de F.Johansson.
Abstract
In the wakes of climate change, the phenology of many species is shifting. This can have many implications for inter-specific competition. In this thesis I studied how temperature affected the larval competition between two species of Odonata, dragonfly: Lestes sponsa and Sympetrum vulgatum. In addition, I studied how this competition was affected by food resource availability. To do this I performed a laboratory experiment on larvae at two different temperatures (21°C and 24°C) and two different resource densities (low and high). I estimated egg hatching rate, growth rate and survival. Larval competition (growth rate and survival) was studied in sympatry in small containers mimicking a natural environment at a density of 5 individuals of each species during a 10-week period. The results showed that eggs of both species hatched at a slightly higher rate at 24°C, and that Sympetrum vulgatum started hatching about one day in advance of Lestes sponsa. In general, growth rate was higher: (1) at 24°C compared to 21°C, (2) at high compared to low resource densities, and (3) in Lestes sponsa compared to Sympetrum vulgatum. Interestingly, at 24oC the higher growth rate of Lestes sponsa was accentuated at the high resource level compared to the low resource level. Hence resource levels affected competition differently depending on temperature. There was a negative relationship between growth rate and survival suggesting that the higher growth rate of larva was to some degree driven by interspecific predation and/or cannibalism. The results from this thesis suggest that resource levels interact with temperature and cause difference in strength of competition between species. Such effects should be considered in theory predicting changes in species distribution in the light of climate change.
