Supplementary material from "Changes in pattern of plant-insect interactions on the Persian ironwood (Parrotia persica, Hamamelidaceae) over the last 3 million years"

The Hyrcanian forest is composed of many Arcto-Tertiary plant species that since the beginning of the Quaternary glaciations have decreased their distribution until they became endemic to the coasts of the Caspian Sea in the northern part of Iran. Today, the Hyrcanian forest is considered as the closest similar remnant of the Plio-Pleisto- cene European paleoforests. One of the most emblematic plant species is the Persian Ironwood (Parrotia persica C. A. Mey). This study presents the first comparison of plant-insect interaction patterns between modern samples from the current Persian Ironwood populations of the endemic species to the Hyrcanian forest and the fossil counterpart from Willershausen (Germany) and Bernasso (France). We wanted to know if the ecological rela- tionships of P. persica with its environment were similar or changed during the last few millions of years, through the analysis of their plant-insect interaction. Fifteen sites were selected in the Hyrcanian forest along temperature and precipitation gradients. A total of 2160 leaves were collected, measured, and examined through some leaf characteristics and their plant-insect interactions. 84% of the leaves were damaged and a total of 3507 damage occurrences were found. A significant lower proportion of specialized damages were found on the leaves from P. persica in the Hyrcanian forest compared to what we observed among the samples from the two fossil outcrops, which could suggest a “non-optimal” environment for P. persica today in its current endemic distribution.

赫卡尼亚森林（Hyrcanian Forest）由诸多北极第三纪植物区系物种组成，自第四纪冰期伊始，这些物种的分布范围持续收缩，最终仅特有分布于伊朗北部里海沿岸区域。如今，赫卡尼亚森林被视作与上新世-更新世欧洲古森林最为相似的现存遗迹。其中最具标志性的植物物种之一为波斯铁木（Parrotia persica C. A. Mey）。本研究首次对比了赫卡尼亚森林内该特有物种——波斯铁木的现存种群现代样本，与产自德国维勒豪森（Willershausen）及法国贝纳索（Bernasso）的对应化石标本之间的植物-昆虫相互作用模式。本研究旨在通过分析其植物-昆虫相互作用，探究波斯铁木在过去数百万年间与环境的生态关系是否发生改变，抑或维持原有相似性。研究团队沿温度与降水梯度，在赫卡尼亚森林内选取了15个样地，共收集、测量并检视了2160片叶片，通过叶片特征及其植物-昆虫互作情况开展分析。结果显示，84%的叶片存在受损痕迹，共计记录到3507处受损事件。相较于两处化石露头的样本，赫卡尼亚森林内波斯铁木叶片的特化受损比例显著更低，这一结果或表明，当前波斯铁木的现有特有分布区内，其生存环境并非"non-optimal"。