栖息地质量对两种网蛱蝶集合种群结构和分布的影响

在河北省赤城县研究了栖息地质量对大网蛱蝶Melitaea phoebe和金堇蛱蝶Euphydryas aurinia两种网蛱蝶集合种群结构和分布的影响。这两种网蛱蝶在约10 km_²的区域内共存，成虫期的蜜源植物几乎相同，大网蛱蝶的发生峰期比金堇蛱蝶晚约一个月，两者只有不到一周左右的时间重叠。大网蛱蝶和金堇蛱蝶幼虫的寄主植物分别是: 祁州漏芦（菊科）和华北蓝盆花（川续断科）。蜜源植物的丰度与两种网蛱蝶的局域种群大小呈正相关；祁州漏芦的密度对大网蛱蝶的局域种群大小影响很大，金堇蛱蝶的局域种群大小则与其寄主植物华北蓝盆花的高度正相关；斑块内平均植被高度与两种网蛱蝶的局域种群大小均呈正相关，植物多样性、植物均匀性和植被盖度均与金堇蛱蝶的局域种群大小负相关，与大网蛱蝶的关系不大。同时分析了其他因子如斑块的坡向、坡度等的影响。主要结论是：1）幼虫寄主植物的不同和成蝶飞行峰期的分离允许两种网蛱蝶在这样一个小的斑块区域内共存；2）蜜源是重要的限制因子，并且受气候随机性的影响很大，蜜源的波动可以很好地解释网蛱蝶集合种群在年度间的动态变化；3）大网蛱蝶和金堇蛱蝶的飞行、食物搜寻能力的不同以及各自寄主植物的生物学特性、空间分布的不同决定了它们具有不同的集合种群结构： 金堇蛱蝶是经典的集合种群，大网蛱蝶是源-汇集合种群；4）斑块质量和昆虫行为共同决定了两种网蛱蝶的集合种群结构和分布。

Impact of habitat quality on metapopulation structure and distribution of two melitaeine butterfly species

We studied the impact of habitat quality factors on the metapopulation structure and distribution, and thus the persistence of two species of melitaeine butterflies, Melitaea phoebe and Euphydryas aurinia, on a metapopulation scale in Chicheng County, Hebei Province, China. These two species coexist in a network of discrete habitat patches within a range of 10 km², larvae feeding on their specific host plants Stemmacantha uniflora (Compositae) and Scabiosa tschiliensis (Dipsacaceae) respectively. However, their nectar resources are almost the same during the adult flight period. The main flight period for E. aurinia is about one month earlier than M. phoebe, with an overlap of only about seven days. The host plants of these two melitaeine butterflies also have a great impact on their occurrence, but act in different ways. Density of the host plant has a great effect on the occurrence of M. phoebe, whereas the height of the host plant is important for E. aurinia. The abundance and distribution of nectar resources are positively correlated to the abundance and distribution of the two butterfly species. The vegetation diversity, evenness, and cover correlate negatively with the occurrence of E. aurinia, but not related to M. phoebe, while the vegetation height has a positive effect on the two butterfly species. We have also considered and discussed the impact of slope aspect, gradient, and irradiation of the habitat patches. Therefore, when discussing the factors affecting metapopulation structure and dynamics, we should pay attention not only to the patch size and Isolation but also the quality differences among patches. Four major points can be well concluded: 1) The specificity of larval host plants and the time segregation of adult feeding permit the co-existence of the two species in this small and patchy system. 2) The nectar resource is a major limiting factor and prone to being affected by weather stochasticity. The fluctuations in nectar resources can explain the dynamic rises and falls of these butterfly metapopulations from 1998 to 2000. 3) The differences between flight and food searching ability of the two butterfly species, as well as the differences between the features and spatial distribution of the two host plants species determined the different metapopulation structures of the two butterfly species. These results supported one of our former conjectures that E. aurinia is a classical metapopulation, and M. Phoebe is a source-sink metapopulation. 4) It is the spatial pattern and quality of the habitat patches (as determined by other factors, e.g., topographic features) interacting with the insects' behavior (e.g., plant preference and flight behavior) that determined the metapopulation structure and distribution of these two butterfly species.