INSECT HERBIVORE COMMUNITIES TRACKED THE CONIFER AGATHIS (ARAUCARIACEAE) FROM PALEOGENE PATAGONIA TO MODERN AUSTRALASIA AND SOUTHEAST ASIA

During the warm early Paleogene, a vast trans-Antarctic rainforest stretched across Gondwana. Recently, the first South American and earliest known members of the broadleaved conifer genus Agathis (Araucariaceae) were recognized in early Paleocene (Palacio de los Loros), early and middle Eocene (Laguna del Hunco and Río Pichileufú, respectively), and possibly terminal Cretaceous (Lefipán Fm.) floras in central Patagonia, Argentina. The breakup of Gondwana and major climate change led to the loss of suitable habitat and extinction of Agathis in South America, but the genus persists today in lowland to upper montane rainforests in Australasia and across Wallace’s Line in SE Asia. We observed that South American fossil Agathis are associated with diverse insect damage types (DTs) that resemble those found on extant Agathis species. To test whether the insect herbivore component communities tracked Agathis during its major range shifts, we compared insect damage on fossil Agathis leaves from Patagonia to that on extant leaves from herbarium collections and field specimens. Similar external foliage feeding on fossil and extant Agathis includes slot feeding (DT8) and margin feeding (DT12). Endophytic feeding on the fossils includes blister galls (DT115), characterized by a thick margin surrounding epidermal tissue with a central exit hole, resembling galls made by scale-insect nymphs on extant Agathis. Fossil scale insect amber casts (DT86) resemble diaspidid scales associated with living Agathis. Elongate blotch mines (DT88) are found on fossil and extant species, including in the Cretaceous, possibly representing the only known Cretaceous-Paleogene boundary crossing leaf-mine association. Fossil columnar galls (DT116) may be an example of an extinct association, as we did not find an extant analogue. Parectopa (Gracillariidae) moth mines are common on extant Agathis australis leaves but not found on the fossils. Overall, we found a similar suite of damage on extant Agathis throughout its modern range and on the Patagonian fossils. Therefore, Agathis and its component communities appear to include the legacy of long-term associations that originated in Gondwana and tracked the genus through major plate movements, environmental changes, and range shifts, persisting today in Australasia and SE Asia.