Programa de Pós-Graduação em Biodiversidade Animal, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Faixa de Camobi km 9, 97105-900, Santa Maria, RS, Brazil.
J Insect Sci. 2012;12:121. doi: 10.1673/031.012.12101.
The richness and composition of a mountain-river chironomid larvae assemblage in the Jacuí River basin, Brazil were studied, and compared with other riverine non-biting midge larvae assemblages previously studied in the country. Additionally, the influence of some regional-scale environmental characteristics on the spatial distribution of these assemblages was tested. The specimens were collected at 12 sites in the middle course of the Jacuí River basin (in the state of Rio Grande do Sul) between April 2000 and May 2002. Around 100 taxa were recorded. The dominant taxa belonged to the genera Rheotanytarsus, Cricotopus, Polypedilum, and Pseudochironomus. Twenty-two rare taxa were found, representing 22% of the total of taxa inventoried. Fourteen genera (Aedokritus, Axarus, Endotribelos, Kiefferulus, Manoa, Oukuriella, Phaenopsectra, Stenochironomus, Xenochironomus, Xestochironomus, Cardiocladius, Metriocnemus, Paracladius, and Rheocricotopus) represent new occurrences in Rio Grande do Sul. The similarity analysis of the chironomid larvae assemblages inventoried in 32 regions of Brazil indicated five groups with similarity higher than 50%. The groups, when the effects of spatial autocorrelation were removed, displayed a weak positive correlation between the assemblage composition and the aquatic system or hydraulic conditions and the hydrographic basin, and a weak negative correlation in relation to the biome. The altitude showed no correlation with the composition of the assemblage. The relatively high richness of the region surveyed in relation to other Brazilian regions corroborates some tendencies already noted in other parts of the world, such as: i) lotic systems may constitute an exception to the rule that diversity is greater in tropical regions, ii) regions of transitional relief may contain the greatest richness of Chironomidae, and iii) in rivers, the group might have its spatial distribution influenced to a greater extent by local environmental characteristics than by regional ones.
本研究调查了巴西雅库伊河流域山区摇蚊幼虫组合的丰富度和组成，并与该国以前研究过的其他河流无刺摇蚊幼虫组合进行了比较。此外，还测试了一些区域尺度环境特征对这些组合空间分布的影响。标本于 2000 年 4 月至 2002 年 5 月在雅库伊河流域中游的 12 个地点采集。共记录了约 100 个分类单元。优势分类单元属于 Rheotanytarsus、Cricotopus、Polypedilum 和 Pseudochironomus 属。发现了 22 个稀有分类单元，占总分类单元的 22%。14 个属（Aedokritus、Axarus、Endotribelos、Kiefferulus、Manoa、Oukuriella、Phaenopsectra、stenochironomus、Xenochironomus、Xestochironomus、Cardiocladius、Metriocnemus、Paracladius 和 Rheocricotopus）在南里奥格兰德州是新记录。对巴西 32 个地区采集的摇蚊幼虫组合进行相似性分析表明，有 5 个组的相似性高于 50%。在去除空间自相关效应后，这些组与水系统或水力条件和水文盆地之间呈弱正相关，与生物群落之间呈弱负相关。海拔与组合组成之间没有相关性。与巴西其他地区相比，调查区域的相对丰富度证实了世界其他地区已经注意到的一些趋势，例如：i）流水系统可能是多样性在热带地区更高的规律的例外，ii）过渡地形地区可能包含最多的摇蚊科物种，iii）在河流中，该群体的空间分布可能更多地受到局部环境特征的影响，而不是受到区域环境特征的影响。
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