Insect herbivore communities tracked the conifer Agathis (Araucariaceae) from Paleogene Patagonia to modern Australasia and Southeast Asia

WILF, P. D.; DONOVAN MICHAEL; ARI IGLESIAS; LABANDEIRA CONRAD; CÚNEO, N. R.

Texas

Congreso; Botanical Society of America Annual Meeting; 2017

Botanical Society of America

During the warm early Paleogene, a vast trans-Antarctic rainforest stretched acrossGondwana. Recently, the first South American and earliest known members of thebroadleaved 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 suitablehabitat and extinction of Agathis in South America, but the genus persists today in lowlandto upper montane rainforests in Australasia and across Wallace?s Line in Southeast Asia. Weobserved 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 insectherbivore component communities tracked Agathis during its major range shifts, wecompared insect damage on fossil Agathis leaves from Patagonia to that on extant leavesfrom herbarium collections and field specimens. Similar external foliage feeding on fossiland extant Agathis includes slot feeding (DT8) and margin feeding (DT12). Endophyticfeeding on the fossils includes galls characterized by a thick margin surrounding epidermaltissue (DT115), resembling blister galls on extant Agathis. Fossil scale insect covers (DT86)preserved as amber casts 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. Parectopa (Gracillariidae) moth mines are common on extant Agathis australis leaves from New Zealand 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 longterm associations that originated in Gondwana and tracked the genus through major plate movements, environmental changes, and range shifts, persisting today in Australasia and Southeast Asia.