Hestmark Geir
Division of Botany and Plant Physiology, Department of Biology University of Oslo, P.O. Box 1066, N-0316 Oslo, Norway Fax: 47-22 85 46 64, , , , , , NO.
Oecologia. 1997 Aug;111(4):523-528. doi: 10.1007/s004420050266.
The lichens Lasallia pustulata and Umbilicaria spodochroa grow in dense monospecific or mixed populations on the coastal cliffs of southern Scandinavia. Attached to the substrate by only a thin central holdfast, their shield-shaped thalli compete for light and space for growth by overlapping each other. Matched pair experiments in the laboratory and field observations of interacting pairs show that different behavioural responses to precipitation tend to result in the margins of U. spodochroa overlapping those of L. pustulata within a few minutes. The behaviour is apparently caused by different capacities for water absorption in the upper and lower cortices of the species. An initial period of repeated encounter caused by thallus expansion and contraction during precipitation will be followed by a period in which U. spodochroa grows to overlap L. pustulata more and more. When the overlapping lichens are wet, flexible and photosynthetically active, the thallus above rests directly on the upper surface of the one below. Very little light is transmitted through thalli of U. spodochroa, and the shaded parts of L. pustulata are retarded in their growth and die off.
地衣Lasallia pustulata和Umbilicaria spodochroa在斯堪的纳维亚半岛南部的沿海悬崖上以密集的单种或混合种群生长。它们仅通过一个薄的中央固着器附着在基质上，盾形的叶状体通过相互重叠来竞争光照和生长空间。实验室中的配对实验和对相互作用对的实地观察表明，对降水的不同行为反应往往会导致在几分钟内U. spodochroa的边缘与L. pustulata的边缘重叠。这种行为显然是由该物种上下皮层不同的吸水能力引起的。降水期间叶状体膨胀和收缩导致的反复接触的初始阶段之后，将是U. spodochroa生长并越来越多地与L. pustulata重叠的阶段。当重叠的地衣湿润、柔韧且具有光合作用活性时，上面的叶状体直接靠在下面的叶状体上表面。很少有光线透过U. spodochroa的叶状体，L. pustulata的阴影部分生长受到抑制并死亡。
