PLANT-ANIMAL INTERACTIONS FROM THE MIOCENE: EVIDENCE FROM A PERMINERALIZED FLORA

Plant-animal interactions in the Tertiary have been well documented from leaf compression floras, however very few studies are known for permineralized plants. The middle Miocene Yakima Canyon "bog" flora of central Washington State is rich in anatomically preserved plant remains. The well preserved white oak acorns, Quercus hiholensis (Fagaceae), and remains of Taxodium, the bald cypress, demonstrate evidence of plant-insect-(fungal) interactions. In addition, several specimens of lepidopteran frass have been found in the matrix. Together these elements document a suite of herbivore-plant and parasitic relationships in this anatomically preserved flora. The acorns contain three types of evidence: burrows, galls and fungal hyphae. The burrows range in length from 1.23-3.25 mm and 0.60-2.17 mm in width. Currently, we are unable to document whether two organisms are responsible for these patterns. The well preserved galls ranging from 1.23-3.20 mm in diameter are clearly assignable to cynipid gall wasps like those associated with modern-day oaks. Also present with these galls are fungal hyphae located at the interface between the gall wall and surrounding plant tissues. The Yakima acorns examined in this study may document the first host-gall-fungal association in the fossil record and suggest that hyperparasitism may have been established by the Miocene. Galls with morphology consistent with those present on extant bald cypresses have also been discovered in association with abundant Taxodium remains. Other evidence of plant-insect relationships includes diagnostic six-sided lepidopteran frass containing fragments of conifer foliage.