Growing numbers of alien plant species threaten natural ecosystems worldwide. Mexico, as a megadiverse country, has lower numbers of alien species than other regions in America. However, there is a lack of information on the factors that determine the diversity patterns of alien species and their relative importance in the vegetation. The diversity of alien roadside herbs was analysed along an elevational gradient in western Mexico, including their relationship with environmental factors. Three hundred and seventeen herbaceous species were found in 37 sampling sites; 10% were aliens. The proportion of alien species in the ruderal herbaceous communities was lower than the average for this vegetation type in the country. Absolute species richness of natives was significantly and positively correlated with elevation. Absolute species richness of aliens was not significantly correlated with elevation, still; higher values were found at lower elevations. Generalised linear models for relative species richness and relative abundance of aliens with elevation had positive estimates near 0, which, though statistically significant, indicated a weak relationship. Other environmental co-factors, such as the distance to roads and highways, climatic variables, and disturbance indicators, were included in a random forest model. No clear correlation patterns were found. This seemingly random distribution of alien herbaceous plants in the region might be caused by the relatively recent introduction of most of the species. They have not yet had time to expand their distribution to their potential maximum. The early stage of the naturalisation process allows us to minimise the further spread of some species with targeted management and prevent them from becoming invasive.

中文翻译：

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墨西哥西部沿海拔梯度的外来路边草药多样性

越来越多的外来植物物种威胁着全世界的自然生态系统。墨西哥作为一个多元化的国家，外来物种的数量低于美国其他地区。然而，缺乏关于决定外来物种多样性模式及其在植被中相对重要性的因素的信息。沿墨西哥西部的海拔梯度分析了外来路边草药的多样性，包括它们与环境因素的关系。37个采样点共发现草本植物317种；10% 是外星人。原始草本群落中外来物种的比例低于国内该植被类型的平均水平。当地人的绝对物种丰富度与海拔高度显着正相关。外星人的绝对物种丰富度与海拔没有显着相关性，仍然; 在较低的高度发现较高的值。相对物种丰富度和外星人相对丰度的广义线性模型具有接近 0 的正估计值，尽管具有统计显着性，但表明相关性较弱。其他环境辅助因素，例如到道路和高速公路的距离、气候变量和干扰指标，都包含在随机森林模型中。没有发现明确的相关模式。该地区外来草本植物的这种看似随机的分布可能是由于大多数物种的引入相对较新造成的。他们还没有时间将他们的分布扩大到他们的潜在最大值。