Rapid recovery of plant-insect associations in Patagonia after the Cretaceous-Paleogene mass extinction

DONOVAN MICHAEL; ARI IGLESIAS; WILF PETER; LABANDEIRA CONRAD

Edmonton

Congreso; Botanical Society of America Annual Meeting; 2015

Study of the end-Cretaceous mass extinction has been heavily regionally biased towards thewestern USA. Recently, a growing body of evidence, especially from Patagonia, Argentina,suggests that extinction and recovery dynamics may have been very different in Gondwana.Low pollen extinction across the Cretaceous?Paleogene (K-Pg) boundary, the survival ofmany vertebrate and typically mid-Mesozoic gymnosperm lineages into the Paleocene, andthe discovery of diverse early Paleocene macrofloras have led to the hypothesis thatPatagonia provided a refugium for biodiversity during the global catastrophe. Plants andassociated insect herbivores provide the foundation for most terrestrial food webs. To testwhether Patagonia provided a refuge for associational diversity, we compared insectdamage on latest Cretaceous and early Paleocene fossil floras from coastal deposits inChubut Province, Patagonia to previously studied insect damage from the western USA,which decreased significantly at the K-Pg boundary. We compared ca. 850 leaf fossils fromthe latest Maastrichtian (67?66 Ma) Lefipán Formation in northwestern Chubut to ca. 2750fossil leaves from three Danian time intervals, including localities that correlate topaleomagnetic chrons C29n and C28n in the Salamanca Formation and C27n in the overlying Peñas Coloradas Formation. We found that insect damage types (DTs) on both theCretaceous and Paleocene floras (50 Cretaceous and 61 Paleocene DTs) are more diversethan in the western USA (49 Cretaceous and 44 early Paleocene DTs from much largersample sizes). Also, comparisons of sampling-standardized DT diversity in Patagoniarevealed a lower K-Pg decrease than what has previously been observed in North Americaduring the same interval. In addition, damage diversity, including overall and specialized DT diversity, increased through the three early Paleocene time intervals. We also analyzed the morphology of Patagonian leaf mines to determine if any leaf miners crossed the K-Pgboundary. Our preliminary results do not suggest any clear boundary-crossing leaf mines,even on surviving plant species, similar to the pattern observed in the western USA. Instead,there are many new leaf mine associations that first appear at the early Paleocenelocalities, providing further evidence for a faster recovery of insect herbivore diversity inPatagonia compared to the western USA. These results, combined with earlier work, support an emerging hypothesis that southern latitudes suffered significant extinctions, butrecovered much more quickly from the global environmental disaster after theend-Cretaceous impact.