Effect of cultivating croplands and grazing in arid grassland habitats on the conservation of melitaeine butterflies in a mountainous area in Northern China

In the study area (Yanjiaping Village, Hebei Province, China), grazing extensity varies at different loca-tions, small and discontinuous croplands are imbedded in some arid grassland, which are habitats for the melitaeine butterflies, Euphydryas aurinia and Melitaea phoebe. These two species of butterflies coexist in this area, in which grazing and cultivation are the main disturbances. Grazing and cultivation have a reciprocal effect on E. aurinia, rather than M. phoebe. We observed that E. aurinia preferred to occupy patches with moderate grazing and imbedded with small and discontinuous croplands, where E. aurinia also has high population density. The percentage of E. aurinia larval groups in the ribbings was significantly higher than that of M. phoebe, whereas larvae of both species tended to increase in recent years. Our data also showed that the population density and the patch occupancy rate of both E. aurinia and M. phoebe were the highest under moderate grazing. It indicates that cultivation of small and dis-continuous croplands within the patch has a significant effect on the population density of both spe-cies of melitaeine butterflies. Thus, to artificially create or maintain semi-natural habitats, comple-mented by moderate grazing, might be an ecological strategy to conserve melitaeine butterflies effec-tively. Considering the distinct impacts of cultivation and grazing on the population distribution and dynamics of the two different species, human disturbance in the mountainous area might be strategi-cally involved in proposing conservation plans for the target species in the future.

Difference in metapopulation structure and dynamics of two species of coexistent melitaeine butterflies

According to investigation on two species of melitaeine butterflies in Yanjiaping Village, Chicheng County, Hebei Province, China, between 1998—2002, to-gether with the use of 1︰10000 contour map of the local area, some conclusions are shown by the SPSS and GIS analysis of data obained from GPS: (1) The two species of melitaeine butterflies have different metapopulation struc-tures. M. phoebe is a source-sink metapopulation, while E. aurinia is a classical metapopulation, supporting the analytic result from our former genetic research. (2) The two species of melitaeine butterflies exhibit different trends of popula-tion dynamics. M. phoebe source-sink metapopulation is very unsteady, and is always small, thus has a tendency to go ex-tinct gradually. But E. aurinia classical metapopulation is stable, and has maintained a larger population size. There-fore, it stands a better chance of long-term survival. (3) The two species of melitaeine butterflies are significantly related in both patch occupancy and local population size. (4) The effect of isolation is significant on the metapopulations of these two species of melitaeine butterflies, consistent with the classical theories, whereas the effect of patch area is not sig-nificant on the metapopulations of these two species of meli-taeine butterflies, which is inconsistent with the classical theories. Therefore, other factors, such as habitat quality, should be considered for their influences on metapopula-tions.