Cultivated exotic plants are often introduced for their aesthetic value and today comprise a substantial fraction of the flora of urban domestic gardens. Yet, their relative contribution to the functional diversity of domestic gardens and how it changes across different climate zones is insufficiently understood. Here, we investigated whether the effects of cultivated exotics on functional diversity of three plant traits related to plant aesthetics (that is, plant showiness, plant height, and leaf area) varied in suburban domestic gardens in three regions (Minnesota, USA; Alt Empordà, Spain; and central South Africa) that differ in aridity. For each garden, we calculated the mean and variance of each plant trait considering all co-occurring species and also splitting them into co-occurring cultivated exotics and natives. Our results revealed that mean plant showiness increased linearly with the proportion of cultivated exotics both across and within studied regions. Moreover, co-occurring cultivated exotics were, on average, showier than natives in all regions, but differences in their trait variances were context-dependent. The interaction between cultivated exotics and aridity explained variation in mean plant height and leaf area better than either predictor alone, with the effect of cultivated exotics being stronger in more arid regions. Accordingly, co-occurring cultivated exotics were taller and had larger leaves than natives in warmer and drier regions, while the opposite was true in cooler and wetter regions. Our study highlights the need to consider the combined effects of exotic species and climate in future studies of urban ecology.

人们通常以其美学价值引入栽培的外来植物，如今它们已构成城市家庭花园植物区系的很大一部分。然而，人们对它们对家庭花园功能多样性及其在不同气候区域的变化方式的相对贡献还知之甚少。在这里，我们调查了在三个地区（美国明尼苏达州；美国东部）的郊区家庭花园中，栽培的外来植物对与植物美学相关的三种植物性状（即植物的花样，植物高度和叶面积）的功能多样性的影响是否不同。 ，西班牙和南非中部）。对于每个花园，我们都考虑了所有同时存在的物种，并计算了每种植物性状的均值和方差，并将它们分为共同出现的栽培外来物种和本地物种。我们的研究结果表明，在整个研究区域内和研究区域内，平均植物显示度均随栽培的外来植物的比例线性增加。此外，在所有区域中，共同出现的栽培外来物种平均而言比当地人更具光泽，但是其性状差异的差异取决于上下文。栽培的外来植物与干旱之间的相互作用解释了平均植物高度和叶面积的变化要好于任何一个预测指标，而在更干旱的地区栽培的外来植物的影响更强。因此，与之相比，在温暖和干燥的地区，共同种植的外来植物比本地人更高，叶子更大，而在凉爽和潮湿的地区则相反。我们的研究强调在未来的城市生态学研究中需要考虑外来物种和气候的综合影响。