RIVER–WATERSHED EXCHANGE: EFFECTS OF RIVERINE SUBSIDIES ON RIPARIAN LIZARDS AND THEIR TERRESTRIAL PREY
RIVER–WATERSHED EXCHANGE: EFFECTS OF RIVERINE SUBSIDIES ON RIPARIAN LIZARDS AND THEIR TERRESTRIAL PREY
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河流与流域交换：河流补贴对河岸蜥蜴及其陆地猎物的影响
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
M. Power
中科院分区：
文献类型：
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作者：
J. Sabo;M. Power
来自外部栖息地的资源补贴可以提高当地消费者的表现或人口密度，从而改变其对原地猎物的影响。补贴的间接影响可能是正面的，也可能是负面的，具体取决于共同消费者的行为。在这里，我们记录了河流昆虫、河岸蜥蜴（Sceloporus occidentalis）和陆地无脊椎动物之间的密切联系。我们假设水生昆虫补贴河岸蜥蜴种群，导致这些蜥蜴在近河栖息地的增长率更高，并且由于蜥蜴的饮食转向水生昆虫，补贴对陆地资源产生短期积极影响。为了检验这些假设，我们使用 2 m 高的围栏或“补贴盾”来通过实验减少水生昆虫流入大型蜥蜴（91 m 2 ）围栏的数量。补贴盾使水生昆虫通量减少了 55-65%。初夏期间，在有补贴（无防护罩）的围栏中，蜥蜴的生长率高出 73，但在夏末，当水生昆虫的环境通量下降至初夏水平的 20% 时，蜥蜴的生长率没有显着差异。在流域内，蜥蜴的生长速度（质量）与水生昆虫的数量丰度呈正相关。因此，在我们的实验中，蜥蜴的增长率跟踪了河流昆虫补贴的季节性和空间可用性。补贴还对蜥蜴的地面栖息地、陆地猎物产生间接影响。白天陆生无脊椎动物在屏蔽环境中的数量下降明显高于无屏蔽环境，而且最常见的地面蜘蛛（Arctosa sp.（狼科））在实验结束时从屏蔽环境中完全消失。陆地无脊椎动物丰度的下降在无屏蔽围栏和蜥蜴围栏之间没有差异。这些数据表明，河流昆虫补贴了河岸的镰孔菌，并在短期内减少了它们对陆地节肢动物的捕食。
Resource subsidies from external habitats can enhance the performance or population density of local consumers, altering their effects on in situ prey. Indirect effects of subsidies may be either positive or negative depending on the behavior of the shared consumer. Here we document strong links between riverine insects, riparian lizards (Sce- loporus occidentalis), and terrestrial invertebrates. We hypothesized that aquatic insects subsidize riparian lizard populations leading to higher growth rates of these lizards in near- river habitats, and that subsidies exert short-term positive effects on terrestrial resources as a result of diet shifts by lizards to aquatic insects. To test these hypotheses, we used 2 m high fences, or 'subsidy shields,' to experimentally reduce aquatic insect flux to large (91 m 2 ) enclosures of lizards. Subsidy shields reduced aquatic insect flux by 55-65%. Growth rates of lizards were 73 higher in subsidized (no-shield) enclosures during the early summer but were not significantly different later in the summer, when ambient fluxes of aquatic insects dropped to 20% of their early season levels. Within the watershed, lizard growth rates (in mass) were positively correlated with the numerical abundance of aquatic insects. Thus, lizard growth rates tracked both seasonal and spatial availability of riverine insect subsidies during our experiment. Subsidies also had indirect effects on the ground- dwelling, terrestrial prey of lizards. Declines of diurnal terrestrial invertebrates were sig- nificantly higher in shield than no-shield enclosures, and the most common ground spider ( Arctosa sp. (Lycosidae)) disappeared completely from shield enclosures by the end of the experiment. Declines in terrestrial invertebrate abundance did not differ between no-shield enclosures and lizard exclosures. These data suggest that riverine insects subsidize riparian Sceloporus and, in the short term, reduce their predation on terrestrial arthropods.