PREMISE The functional significance of leaf margins has long been debated. In this study, we explore influences of climate, leaf lobing, woodiness, and shared evolutionary history on two leaf margin traits within the genus Pelargonium. METHODS Leaves from 454 populations of Pelargonium (161 species) were collected in the Greater Cape Floristic Region and scored for tooth presence/absence and degree of lobing. Tooth density (number of teeth per interior perimeter distance) was calculated for a subset of these. We compared five hypotheses to explain tooth presence and density using mixed effect models. RESULTS Tooth presence/absence was best predicted by the interaction of leaf lobing and mean annual temperature (MAT), but often in patterns opposite those previously reported: species were more likely to be toothed with warmer temperatures, particularly for unlobed and highly lobed leaves. In contrast, tooth density was best predicted by the interaction of MAT and the season of most rain; density declines with temperature as consistent with expectations, but only in winter-rain dominated areas. Woody and nonwoody species within Pelargonium have similar associations between tooth presence/absence and MAT, contrary to the expectation that patterns within nonwoody species would be insignificant. CONCLUSIONS We conclude Pelargonium leaf margins show predictable responses to climate, but these responses are complex and can contradict those found for global patterns across plant communities.

中文翻译：

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来自大开普省植物区系的落叶谱系的叶缘以意想不到的方向追踪气候

前提 叶缘的功能意义长期以来一直存在争议。在这项研究中，我们探索了气候、叶裂、木质和共同进化历史对天竺葵属内两个叶缘性状的影响。方法 在大开普省植物区收集了 454 个天竺葵种群（161 种）的叶子，并对牙齿的存在/缺失和裂叶程度进行评分。计算其中的一个子集的牙齿密度（每内周距离的牙齿数量）。我们比较了五种假设，以使用混合效应模型来解释牙齿的存在和密度。结果 通过叶裂和年平均温度 (MAT) 的相互作用可以最好地预测牙齿的存在/缺失，但通常与之前报道的模式相反：物种更有可能在温度升高时长牙，特别是对于不裂和高度裂的叶子。相比之下，通过 MAT 和降雨最多的季节的相互作用可以最好地预测牙齿密度；密度随温度下降与预期一致，但仅在冬季降雨为主的地区。天竺葵中的木质和非木质物种在牙齿存在/缺失和 MAT 之间具有相似的关联，这与非木质物种中的模式无关紧要的预期相反。结论 我们得出结论，天竺葵叶缘对气候的反应是可预测的，但这些反应是复杂的，并且可能与在植物群落的全球模式中发现的反应相矛盾。密度随温度下降与预期一致，但仅在冬季降雨为主的地区。天竺葵中的木质和非木质物种在牙齿存在/缺失和 MAT 之间具有相似的关联，这与非木质物种中的模式无关紧要的预期相反。结论 我们得出结论，天竺葵叶缘对气候的反应是可预测的，但这些反应是复杂的，并且可能与在植物群落的全球模式中发现的反应相矛盾。密度随温度下降与预期一致，但仅在冬季降雨为主的地区。天竺葵中的木质和非木质物种在牙齿存在/缺失和 MAT 之间具有相似的关联，这与非木质物种中的模式无关紧要的预期相反。结论 我们得出结论，天竺葵叶缘对气候的反应是可预测的，但这些反应是复杂的，并且可能与在植物群落的全球模式中发现的反应相矛盾。