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Ant Behavioral Responses to Aphids Colonizing <i> Ligusticum porteri </i>

Authors: Kennamer, C.
Year: 2022
Publisher: UNKNOWN

Abstract

Ant-aphid mutualisms are keystone interactions that, if altered, have the potential to cause cascading, multitrophic effects on local arthropod and plant communities. In our study system, the flowering stalks of Ligusticum. porteri (Apiaceae) are colonized by the aphid Aphis asclepiadis, which relies on a protection mutualism with ants. We examined the mediating role of phenology in the host plant L. porteri on mutualistic ant behavior in the subalpine zone of the Rocky Mountains in Colorado, USA. To accomplish this, we utilized three tiers of observational data to infer the role of host plant phenology on ant abundance and behavior. First, we compiled six years of census data taken over June through August from 2017-2022 to determine ant abundance during pre-flowering, flowering, and post-flowering phenological stages. In 2022, we recorded focused observations of tending behavior in ants, adding to the census data collected in previous years. Lastly, we used an ethogram to examine effect of advanced, post-flowering phenology in aphid-colonized host plants on a range of 26 different ant behaviors divided among 6 behavioral categories. Ant abundance increased during the flowering stages of L. porteri. Additionally, ant tending behavior also increased during the flowering stages. Finally, during the post flowering stages (fruit initiation and maturation), ants spent the highest proportion of their time on communication, exploration, and grooming behaviors. Increased time spent during these stages on non-tending behaviors such as grooming suggests that ants may budget less time for aphid tending as host plant phenology advances, reducing protective benefits conferred by ants during this time. Taken together, these results suggest that, in years where early season snowmelt leads to advanced phenology of L. porteri, early season aphid colonies arriving in June will encounter host plant conditions that are less conducive to attracting the ants needed to protect them.

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