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-Pleistocene 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 relationships 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.