Geographic origin and migration phenology of European red admirals (Vanessa atalanta) as revealed by stable isotopes.

BACKGROUND: Long-distance migration has evolved multiple times in different animal taxa. For insect migrants, the complete annual migration cycle covering several thousand kilometres, may be performed by several generations, each migrating part of the distance and reproducing. Different life-cycle stages and preferred orientation may thus, be found along the migration route. For migrating red admirals (Vanessa atalanta) it has been questioned if they reproduce in the most northern part of the range. Here we present migration phenology data from a two-year time series of migrating red admirals captured at Rybachy, Kaliningrad, in the northern part of Europe investigating time for migration, life-history stage (migration, reproduction) as well as site of origin in individual butterflies. METHODS: Red admirals were captured daily at a coastal site during spring, summer and autumn in 2004 and 2005. For the sampled individuals, reproductive status and fuel content were estimated by visual inspection, and hydrogen isotopes (δ 2H) were analysed in wing samples. δ 2H values was compared with samples from two nearby reference sites in Estonia and Poland. RESULTS: Analysis of hydrogen isotopes (δ 2H) in red admiral wings showed that the spring cohort were of a southerly origin, while those caught in August or later in the autumn were from the local region or areas further to the north. All females caught during spring had developing eggs in their abdomen, but no eggs were found in late summer/autumn. There was a male-biased sex ratio during autumn and a difference in lipid content between years. When comparing the isotopic data with inland nearby locations, it was clear that the range of δ 2H values (- 181 to - 78) was wider at Rybachy as compared to the two reference sites in Estonia and Poland (- 174 to - 100). CONCLUSIONS: During spring, migratory female red admirals arrived from the south and were ready to reproduce, while the autumn passage mainly engaged local and more northern individuals carrying large fuel deposits in preparation for long-distance migration. The phenology data suggest that individuals select to migrate in favourable weather conditions and that numbers may differ between years. Future studies should focus on individual sampling at a wide range of sites to reveal differential migration strategies and timing of migration between sexes and populations of migrating butterflies

Relatedness and population differentiation in a colonial butterfly, Eucheira socialis (Lepidoptera: Pieridae)

Eucheira socialis (Westwood) occurs above 1,800 m in mountains throughout Mexico and has a remarkable suite of autapomorphies, including communal larval nests and a mean primary sex ratio of 70% males. We gathered allozyme data for 31 loci freom individuals within nests within populations and used hierarchical F statistics to assess population structure and relatedness at these levels. Allozyme variation was far lower than reported in most Lepidoptera, and was absent freom the populations sampled freom southern Mexico. Among 5 sample sites distributed throughout Mexico, differentiation was high (FST = 0.54), which is consistent with a history of interrupted gene flow. At lower hierarchical levels in the variable populations, we found significant excess heterozygotes within nests (FIN = 0.15) and evidence for structuring within subpopulations (FIS = 0.015, significantly greater than FIN) Average relatedness among nestmates was r(NS) = 0.28, which is significantly less than r = 0.5. This is probably caused largely by interchange among nests on multinest trees