Biogeographical gradients in galling species richness
Biogeographical gradients in galling species richness
复制标题
毛虫物种丰富度的生物地理梯度
作者：
G. Wilson Fernandes;Peter W. Price
摘要在巴西和美国，引用了五个假设来解释不同结构复杂性的植物(即草本、灌木和乔木)上每个位置的刺痛物种数量的差异。这些假说是：1)海拔/纬度梯度假说；2)恶劣环境假说；3)植物物种丰富度假说；4)寄主植物面积假说；5)植物结构复杂性假说。海拔和恶劣环境假说被两个地区的样本数据关联和支持，随着海拔/纬度的下降和地点变得更热和更干燥，胆汁物种数量增加。通过研究亚利桑那州同一海拔的河岸地点和干旱山坡地点，这两个假设被分开了。在干旱地区，寄生物种的频率高于河岸地区，这支持了恶劣环境假说。在测试的五个假说中，只有恶劣环境假说预测到，叮咬昆虫的物种数量应该随着环境变量(如湿度和温度)的变化而变化。与其他植物类型相比，温带灌木支持更多的刺激性物种，无论是在干燥还是在中生地点。热带和温带地区物种丰富度之间的总体差异在统计学上并不显著。自由食性昆虫食草动物物种表现出与Gallers相反的物种丰富度格局，更多地分布在河岸地带。本研究证实了胆汁形成习性是对恶劣或应激环境的适应这一假设，并首次描述了使昆虫物种丰富的大范围地理格局。
SummaryFive hypotheses were invoked to account for variation in galling species number per location on plants of different structural complexity, namely herbs, shrubs, and trees, both in Brazil and USA. The hypotheses were: 1) the altitudinal/latitudinal gradient hypothesis; 2) the harsh environment hypothesis; 3) the plant species richness hypothesis; 4) the host plant area hypothesis; 5) the plant structural complexity hypothesis. The altitudinal and the harsh environment hypotheses were correlated and supported with sample data in both localities, with increasing gall species number as altitude/latitude declined and as sites became hotter and drier. The two hypotheses were separated by studying riparian sites and dry hillside sites at the same elevation in Arizona. Galling species frequency was higher in dry sites than in riparian sites, supporting the harsh environment hypothesis. Of the five hypotheses tested only the harsh environment hypothesis predicted that galling insect species number should vary in response to environmental variables such as moisture and temperature. Temperate shrubs supported more galling species than did other plant types, both in dry and mesic sites. The overall difference between galling species richness for tropical and temperate latitudes was not statistically significant. Free-feeding insect herbivore species exhibited the opposite pattern of species richness to gallers, being more speciose in riparian sites. The present study corroborates the hypothesis that the gall forming habit is an adaptation to harsh or stressful environments, and we describe for the first time broad scale geographical patterns in galling insect species richness.