Pérez-Cembranos Ana, Pérez-Mellado Valentín
Department of Animal Biology, Universidad de Salamanca, Campus Miguel de Unamuno, 37071 Salamanca, Spain.
Animals (Basel). 2023 Mar 8;13(6):973. doi: 10.3390/ani13060973.
During the last 24 years, the mutualistic interaction between the dead horse arum, , and the Balearic lizard, , was studied on Aire Island (Balearic Islands, Spain). From a small population of a hundred plants, the dead horse arum expanded extraordinarily throughout the island, reaching the highest known densities of the species and occupying areas of the island where it was not previously present. The current abundance of plants is a direct effect of the frugivorous activity of the Balearic lizard, which is the main, if not the only, effective seed disperser of the plant on Aire Island. However, abiotic factors predominated over biotic factors in driving abundance of plants. Over the years, plant densities varied significantly depending on the aridity of the island, with higher densities recorded in drier years. Lizards' frugivorous activity and dispersal intensity was inversely correlated with annual rainfall. We found higher dispersal intensity in years with lower rainfall. We propose that the years of lower rainfall are those in which there is a lower prey availability. In such years, lizards compensate the shortage of other trophic resources with a more intense consumption of dead horse arum fruits. The mutualistic interaction is therefore asymmetric, since there is a greater influence of the frugivorous activity of the lizards on the plants than of the plants on lizards. It is, in short, a system chronically out of balance.
在过去的24年里，西班牙巴利阿里群岛的艾尔岛上对死马海芋与巴利阿里蜥蜴之间的互利共生关系进行了研究。死马海芋最初仅有一小群约100株植物，后来在全岛范围内异常扩张，达到了该物种已知的最高密度，并占据了岛上以前没有该植物的区域。目前植物的丰富度是巴利阿里蜥蜴食果活动的直接结果，巴利阿里蜥蜴是该植物在艾尔岛上主要的（即便不是唯一的）有效种子传播者。然而，在推动植物丰富度方面，非生物因素比生物因素更为重要。多年来，植物密度因岛屿的干旱程度而有显著差异，干旱年份记录的密度更高。蜥蜴的食果活动和传播强度与年降雨量呈负相关。我们发现在降雨量较低的年份传播强度更高。我们认为降雨量较低的年份是其他猎物可获得性较低的年份。在这些年份里，蜥蜴通过更大量地食用死马海芋果实来弥补其他营养资源的短缺。因此，这种互利共生关系是不对称的，因为蜥蜴的食果活动对植物的影响大于植物对蜥蜴的影响。简而言之，这是一个长期失衡的系统。
