INSECT DAMAGE ON THE INDO-PAKISTAN COLLISION FRONT (GHAZIJ FM., BALOCHISTAN, PAKISTAN): FIRST TROPICAL INSECT DAMAGE FOR THE EARLY EOCENE CLIMATIC OPTIMUM

Insect damage on leaves is abundant in the fossil record, presenting a rich data source for understanding responses to climatic and environmental shifts and tracking evolutionary associations through time. For example, insect damage studies during the Early Eocene Climatic Optimum (EECO)—the warmest period of the Cenozoic and a time of global radiation for extant insect clades—show increased damage diversity with warming, indicating higher insect diversity. However, testing these hypotheses often requires whole-flora insect-damage studies without collection bias, which are rare in Cenozoic Asia. Here, we preliminarily describe the insect damage present on the first plant macrofossils from the early Eocene (ca. 54–50 Ma) Ghazij Formation in Balochistan, Pakistan, a valuable paleobotanical record of the northwestern margin of the Indo-Pakistan Tectonic Plate (see Spagnuolo et al. abstract for more information on the flora). The sites, now inaccessible due to geopolitical conflict, preserve Indo-Pakistan biota during the onset of the EECO and India-Asia collision activity—a hypothesized contributor to Southeast Asia’s biodiversity. In 2000, ca. 382 plant macrofossils of ca. 25 species were collected from 13 sites in the middle and upper Ghazij Fm. (5–10° N paleolatitude), which are correlated with the only magnetostratigraphy from this time interval in Indo-Pakistan. From preliminary data, approximately 74% of the scored Ghazij leaf specimens have insect damage, with more than 30 damage types (DTs) reported. Preliminary data suggest a diverse array of generalist and host-specific DTs. A few DTs of note are the removal of a major vein (DT68, found mostly on Fabaceae morphotype GH05); deep/expanding marginal excision (DT15); several piercing and sucking traces, galls, and mines. Colonial scale-insect covers, likely representing a new DT, are found on palm-leaf morphotype GH11, along with galls (DT83). Little change in DT frequency is observed among Ghazij Fm. sampling localities. These preliminary data represent the oldest complete damage assemblage from a Cenozoic Asian flora, the only Paleogene quantitatively analyzed insect damage for the Indo-Pakistan subcontinent, and the only tropical insect-damage report from the early Eocene—the warmest part of the planet at the warmest time in the Cenozoic.