Presented By: Ecology and Evolutionary Biology
EEB Tuesday Seminar Series - Speakers: Abbey Soule & Allie Fletcher
Speaker 1: Abbey Soule from Weber lab
Title: Scaredy cat(erpillars): Bottom-up vs. top-down drivers of defense sequestration in Estigmene acrea
Description: Sequestration of plant chemicals is well-established as a defense mechanism used by herbivorous insects against their predators, yet the drivers of variation in sequestered defenses remain poorly understood. Using the salt marsh caterpillar, Estigmene acrea, which sequesters pyrrolizidine alkaloids (PAs) from host plants for defense against predators, we performed two experiments to assess the influence of (1) chemical diversity in caterpillar diet and (2) diversity of predator non-consumptive effects (NCEs) on sequestered defenses in adult moths. In this presentation, I will discuss the differences in sequestered defenses resulting from our experiments, analyzed using targeted ultra high performance liquid chromatography-mass spectrometry (UPLC-MS) and downstream calculation of PA abundance using methods I have developed in my dissertation work. We found that dietary chemical diversity did not impact PA sequestration, but that predator NCE diversity significantly increased sequestered PA abundance through a selective effect imposed by particularly 'scary' predators. Together, our combination of experimental treatments alongside analytical chemistry allowed us to investigate top-down and bottom-up trophic forces on sequestration patterns that have not previously been explored.
Speaker 2: Allie Fletcher from Weber lab
Title: Hear Today, Gone Tomorrow: Ear Mites in Noctuoid Moths
Description: Moths and butterflies serve as hosts for a variety of parasites, noteworthy among which are the Dicrocheles ear mites of noctuoid moths which complete their life cycle within the moths' thoracic ears. Throughout the mid-20th century, Asher Treat’s work provided unprecedented insight into these mites' natural history and their prevalence in moths in Western Massachusetts. Building on this foundation, we examined a broader geographic and taxonomic scope in order to approach questions about the co-evolution of these mites and their hosts, including defensive adaptations in the moths. Using five large entomological collections, we examined over 17,700 moth specimens for ear mites and nearly doubled the known list of recorded host species: we add 76 new host species records of the single-ear mites D. phalaenodectes, D. eothenes, D. hippeoides, and D. pelates, of which 40 represent the Leucaniini and 30 in the most frequently infested genus Leucania; and 32 new hosts of the double-ear mite D. scedastes (10 Leucaniini, 4 Leucania). Further, in several hundred Leucania linita, we quantified wing and body wear and tested its relationship with mite presence. Mite infestation was strongly associated with specimen condition: the most worn individuals were more than four times as likely to harbor mites as pristine individuals.
Title: Scaredy cat(erpillars): Bottom-up vs. top-down drivers of defense sequestration in Estigmene acrea
Description: Sequestration of plant chemicals is well-established as a defense mechanism used by herbivorous insects against their predators, yet the drivers of variation in sequestered defenses remain poorly understood. Using the salt marsh caterpillar, Estigmene acrea, which sequesters pyrrolizidine alkaloids (PAs) from host plants for defense against predators, we performed two experiments to assess the influence of (1) chemical diversity in caterpillar diet and (2) diversity of predator non-consumptive effects (NCEs) on sequestered defenses in adult moths. In this presentation, I will discuss the differences in sequestered defenses resulting from our experiments, analyzed using targeted ultra high performance liquid chromatography-mass spectrometry (UPLC-MS) and downstream calculation of PA abundance using methods I have developed in my dissertation work. We found that dietary chemical diversity did not impact PA sequestration, but that predator NCE diversity significantly increased sequestered PA abundance through a selective effect imposed by particularly 'scary' predators. Together, our combination of experimental treatments alongside analytical chemistry allowed us to investigate top-down and bottom-up trophic forces on sequestration patterns that have not previously been explored.
Speaker 2: Allie Fletcher from Weber lab
Title: Hear Today, Gone Tomorrow: Ear Mites in Noctuoid Moths
Description: Moths and butterflies serve as hosts for a variety of parasites, noteworthy among which are the Dicrocheles ear mites of noctuoid moths which complete their life cycle within the moths' thoracic ears. Throughout the mid-20th century, Asher Treat’s work provided unprecedented insight into these mites' natural history and their prevalence in moths in Western Massachusetts. Building on this foundation, we examined a broader geographic and taxonomic scope in order to approach questions about the co-evolution of these mites and their hosts, including defensive adaptations in the moths. Using five large entomological collections, we examined over 17,700 moth specimens for ear mites and nearly doubled the known list of recorded host species: we add 76 new host species records of the single-ear mites D. phalaenodectes, D. eothenes, D. hippeoides, and D. pelates, of which 40 represent the Leucaniini and 30 in the most frequently infested genus Leucania; and 32 new hosts of the double-ear mite D. scedastes (10 Leucaniini, 4 Leucania). Further, in several hundred Leucania linita, we quantified wing and body wear and tested its relationship with mite presence. Mite infestation was strongly associated with specimen condition: the most worn individuals were more than four times as likely to harbor mites as pristine individuals.
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