Fagundes Marcílio, Fernandes G Wilson
Laboratório de Biologia da Conservação DBG/ CCBS, Universidade Estadual de Montes Claros, Montes Claros, MG, Brazil 39401-089.
Rev Biol Trop. 2011 Sep;59(3):1419-32.
The spatial heterogeneity hypothesis has been invoked to explain the increase in species diversity from the poles to the tropics: the tropics may be more diverse because they contain more habitats and micro-habitats. In this paper, the spatial heterogeneity hypothesis prediction was tested by evaluating the variation in richness of two guilds of insect herbivores (gall-formers and free-feeders) associated with Baccharis dracunculifolia (Asteraceae) along a latitudinal variation in Brazil. The seventeen populations of B. dracunculifolia selected for insect herbivores sampling were within structurally similar habitats, along the N-S distributional limit of the host plant, near the Brazilian sea coast. Thirty shrubs were surveyed in each host plant population. A total of 8 201 galls and 864 free-feeding insect herbivores belonging to 28 families and 88 species were sampled. The majority of the insects found on B. dracunculifolia were restricted to a specific site rather than having a geographic distribution mirroring that of the host plant. Species richness of free-feeding insects was not affected by latitudinal variation corroborating the spatial heterogeneity hypothesis. Species richness of gall-forming insects was positively correlated with latitude, probably because galling insect associated with Baccharris genus radiated in Southern Brazil. Other diversity indices and evenness estimated for both gall-forming and free feeding insect herbivores, did not change with latitude, suggesting a general structure for different assemblages of herbivores associated with the host plant B. dracunculifolia. Thus it is probable that, insect fauna sample in each site resulted of large scale events, as speciation, migration and coevolution, while at local level, the population of these insects is regulated by ecological forces which operate in the system.
热带地区可能具有更高的多样性，因为它们包含更多的栖息地和微栖息地。在本文中，通过评估与巴西龙蒿（菊科）相关的两个食草昆虫类群（形成虫瘿者和自由取食者）的丰富度沿巴西纬度变化的情况，对空间异质性假说的预测进行了检验。为进行食草昆虫采样而选择的17个巴西龙蒿种群位于结构相似的栖息地内，沿着寄主植物的南北分布界限，靠近巴西海岸。在每个寄主植物种群中调查了30株灌木。总共采集到了8201个虫瘿和864只自由取食的食草昆虫，它们分属于28个科和88个物种。在巴西龙蒿上发现的大多数昆虫都局限于特定地点，而不是具有与寄主植物相同的地理分布。自由取食昆虫的物种丰富度不受纬度变化的影响，这证实了空间异质性假说。形成虫瘿昆虫的物种丰富度与纬度呈正相关，可能是因为与巴西龙蒿属相关的形成虫瘿昆虫在巴西南部辐射演化。对形成虫瘿和自由取食的食草昆虫估计的其他多样性指数和均匀度并未随纬度变化，这表明与寄主植物巴西龙蒿相关的不同食草动物组合具有一般结构。因此，每个地点的昆虫区系样本可能是由大规模事件导致的，如物种形成、迁移和共同进化，而在局部层面，这些昆虫的种群受到系统中起作用的生态力量的调节。
