Animal-Plant Interactions Drive Gas Exchange Patterns in Acacias & Offspring in Semi-Arid Savanna скачать в хорошем качестве

Animal-Plant Interactions Drive Gas Exchange Patterns in Acacias & Offspring in Semi-Arid Savanna

Presented by Patrick Milligan, PhD | University of Nevada - Reno In East African “black cotton” savannas, whistling-thorn acacias (Acacia drepanolobium) contend with ungulate mega-herbivores, trunk-boring insect parasites, and intense dry periods. Whistling-thorn acacias form large and dense monocultures despite these exogenous factors, and their dominance of the overstory in black cotton savannas has often been attributed to their tightly co-evolved mutualism with ant defenders in the genera Crematogaster and Tetraponera. The four ant species that can occupy a host tree 1) aggressively exclude other ant colonies from the host tree and 2) impose highly contrasting costs on the host tree in the form of differential nectar consumption, floral castration, and trunk excavation. In this semi-arid savanna, light competition between acacias is virtually nonexistent, but transpiration represents a significant risk for this C3-photosynthesizer. Dr. Milligan predicts that host plants carefully attenuate their photosynthesis to meet the metabolic demands of their occupant while also limiting their exposure to future water stress. In this webinar, Dr. Milligan recounts a field experiment in Kenyan black cotton savannas (conducted from 2021-2023) that described acacia adjustments in photosynthetic parameters in response to interactions with both large ungulate herbivores and highly contrasting ant symbionts. He will then move on to the results of a greenhouse experiment in Reno, in which they reared saplings from seeds collected in this Kenyan field experiment, and showed that DNA methylation patterns in seed material likely influenced saplings to be “primed” with physiological fine-tuning similar to patterns found in the mother tree population. Finally, Dr. Milligan is excited to present confirmatory results from two groups of University of Florida study abroad students who in their final projects in our field courses, used PP Systems field equipment to investigate how acacia photosynthetic rates predict ant aggression against simulated herbivory, thus describing a likely feedback system between ant mutualistic fidelity and plant mutualistic investment.