Late Pleistocene galls from the La Brea Tar Pits and their implications for cynipine wasp and native plant distribution in southern California

Abstract

Thirteen intact cynipine galls (Cynipidae) are identified from the significant late Pleistocene locality of Rancho La Brea, mostly within the range of approximately 30,000 to 48,000 14C yr BP. Late Cenozoic cynipids have a poor fossil record; it is thus of great interest that the provisional dates for this fossil gall collection establish that these insects and their hosts were an important part of the late Pleistocene ecosystem in and around Rancho La Brea. Cynipine host specificity both verifies, as well as augments, the proportionally low record of plants recovered at Rancho La Brea in comparison to records of mammals, birds, and other fauna. Because galler and hosts represent extant species, their climate and habitat restrictions offer a good basis for making paleoecological inferences. In particular, they imply that many of the diverse habitats found in California today, or, at least plant associations with similar environmental restrictions, some presently a distance from the Rancho La Brea Tar Pits, existed in the vicinity of this locality during the late Pleistocene. This material also includes previously undescribed species, several of which are morphologically similar to extant comparative material that exhibits a “jumping” behavior, previously believed to be unique to Neuroterus saltatorius Edwards.