Study On Insect-damaged Fossil Leaves From The Late Miocene Of Lincang,yunnan Province,China

Yunnan Province is located in the southwestern China,with low latitudes,warm climate and abundant rainfall.Most of the regions are subtropical climate,only a minor part has a tropical climate.Lincang City is located in the border of Yunnan Province.The Bangmai basin,from where the fossils were collected,with well-developed and exposed strata,has quite rich fossil records.It is an important area for studying the Cenozoic plants.Lincang persisted a monsoon climate during the late Miocene and existed a complex forest system with extremely abundant plant species.The discovery of many plant fossils in the Miocene of Yunnan proved that the southwestern part of China is a refuge for the survival of many ancient plant groups and the origin of the current species.In this paper,after calculating and describing the insect feeding fossils which collected from Lincang,Yunnan Province,six main insect feeding patterns were identified,including hole feeding,surface feeding,galling,skeletonization,marginal feeding,and leaf mining.These main insect feeding patterns were subdivided into 36 types of damage.After the morphological identification of these insect-damaged leaf fossils,a total of 13 families were identified.Based on the feeding patterns on the fossils of plant leaves,we speculated on the group of insects that cause damage to those leaves.It is believed that six insect orders might had been existed since the late Miocene in the Bangmai Basin.The fossils which have complete sizes and the damage traces were selected and measured.Through the analysis of leaf area,petiole width,insect feeding frequency and insect feeding rate,we got the conclusion that the leaves of the late Miocene in Lincang,Yunnan Province were growing in a resource-rich environment.And the leaves had short life span and rapid growth rate,with small leaf mass per area,and adopted a “high nutrition escape” defense strategy.After calculating and describing the fossils which collected from the Bangmai formation in Yunnan,we analyzed and compared our data to those of the fossils found in other areas of the Cenozoic.It is suggested that the high proportion of herbivory(21%)and the low richness of galling functional feeding type(20%)verified that the climate in Lincang was humid and subtropical in the late Miocene.