Knoch Tom R, Faeth Stanley H, Arnott Diane L
Department of Zoology, Arizona State University, 85287-1501, Tempe, AZ, USA.
Oecologia. 1993 Oct;95(4):470-473. doi: 10.1007/BF00317429.
Endophytic fungi are thought to interact mutualistically with host plants by producing alkaloid metabolites that deter herbivory. Since such fungi are transmitted via seed in some grasses, the presence of endophytes may also protect plants from seed predators. We conducted seed choice experiments for two dominant seed harvesting ants, Pogonomyrmex rugosus in the Sonoran desert and Pogonomyrmex occidentalis at a higher elevation, riparian zone in Arizona, USA. Non-infected fescue (Festuca arundinacea) seeds and seeds infected with the endophytic fungus, Acremonium coenophialum, were presented to ant colonies in three different populations. Infected seeds were harvested less frequently than non-infected seed for the two populations of Pogonomyrmex rugosus but not for the population of Pogonomyrmex occidentalis. We also a conducted seed dispersal experiment for one population of Pogonomyrmex rugosus. Of the seeds that were harvested, most of the colonies discarded more infected seeds into refuse piles than expected by chance. Seeds discarded into refuse piles have greater germination success than surrounding areas. The most important interaction of endophytes and grasses may be deterrence of seed predation and enhancing the probability of germinating in favorable sites, since these processes directly increase plant fitness.
内生真菌被认为通过产生阻止食草行为的生物碱代谢物与宿主植物进行互利共生。由于这类真菌在一些禾本科植物中通过种子传播，内生真菌的存在也可能保护植物免受种子捕食者的侵害。我们针对两种主要的种子采集蚂蚁进行了种子选择实验，一种是索诺兰沙漠中的粗纹收获蚁（Pogonomyrmex rugosus），另一种是美国亚利桑那州海拔较高的河岸带的西方收获蚁（Pogonomyrmex occidentalis）。将未感染内生真菌的羊茅（Festuca arundinacea）种子和感染内生真菌Acremonium coenophialum的种子分别提供给三个不同种群的蚁群。对于粗纹收获蚁的两个种群，感染种子的收获频率低于未感染种子，但西方收获蚁种群并非如此。我们还对粗纹收获蚁的一个种群进行了种子传播实验。在收获的种子中，大多数蚁群丢弃到垃圾堆中的感染种子比随机预期的要多。丢弃到垃圾堆中的种子比周围区域的种子具有更高的发芽成功率。内生真菌与禾本科植物最重要的相互作用可能是阻止种子被捕食，并提高在适宜地点发芽的概率，因为这些过程直接提高了植物的适合度。
