Fitzpatrick Ginny, Lanan Michele C, Bronstein Judith L
Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, 85721, USA,
Oecologia. 2014 Sep;176(1):129-38. doi: 10.1007/s00442-014-3005-8. Epub 2014 Jul 11.
Mutualism is an often complex interaction among multiple species, each of which may respond differently to abiotic conditions. The effects of temperature on the formation, dissolution, and success of these and other species interactions remain poorly understood. We studied the thermal ecology of the mutualism between the cactus Ferocactus wislizeni and its ant defenders (Forelius pruinosus, Crematogaster opuntiae, Solenopsis aurea, and Solenopsis xyloni) in the Sonoran Desert, USA. The ants are attracted to extrafloral nectar produced by the plants and, in exchange, protect the plants from herbivores; there is a hierarchy of mutualist effectiveness based on aggression toward herbivores. We determined the relationship between temperature and ant activity on plants, the thermal tolerance of each ant species, and ant activity in relation to the thermal environment of plants. Temperature played a role in determining which species interact as mutualists. Three of the four ant species abandoned the plants during the hottest part of the day (up to 40 °C), returning when surface temperature began to decrease in the afternoon. The least effective ant mutualist, F. pruinosus, had a significantly higher critical thermal maximum than the other three species, was active across the entire range of plant surface temperatures observed (13.8-57.0 °C), and visited plants that reached the highest temperatures. F. pruinosus occupied some plants full-time and invaded plants occupied by more dominant species when those species were thermally excluded. Combining data on thermal tolerance and mutualist effectiveness provides a potentially powerful tool for predicting the effects of temperature on mutualisms and mutualistic species.
互利共生是多种物种之间一种通常较为复杂的相互作用，其中每个物种对非生物条件的反应可能不同。温度对这些以及其他物种相互作用的形成、瓦解和成功所产生的影响，目前仍知之甚少。我们研究了美国索诺兰沙漠中仙人掌费氏强刺球果仙人掌（Ferocactus wislizeni）与其蚂蚁防御者（粉状前结蚁（Forelius pruinosus）、仙人掌 Crematogaster 蚁（Crematogaster opuntiae）、金黄收获蚁（Solenopsis aurea）和木蚁（Solenopsis xyloni））之间互利共生的热生态学。这些蚂蚁被植物产生的花外蜜所吸引，作为交换，它们保护植物免受食草动物侵害；基于对食草动物的攻击性，存在一个互利共生有效性的等级体系。我们确定了温度与植物上蚂蚁活动之间的关系、每种蚂蚁物种的热耐受性，以及与植物热环境相关的蚂蚁活动。温度在决定哪些物种作为互利共生者相互作用方面发挥了作用。四种蚂蚁中有三种在一天中最热的时候（高达40摄氏度）离开了植物，在下午表面温度开始下降时返回。最无效的互利共生蚂蚁，粉状前结蚁，其临界热最大值明显高于其他三个物种，在观察到的植物表面温度的整个范围内（13.8 - 57.0摄氏度）都有活动，并且会拜访温度最高的植物。粉状前结蚁会全天占据一些植物，当更具优势的物种因温度原因被排除时，它会侵入被这些物种占据的植物。结合热耐受性和互利共生有效性的数据，为预测温度对互利共生关系和互利共生物种的影响提供了一个潜在的有力工具。
