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May 19, 2022

5:00pm 1100 TLSB

EcoEvoPub Seminar Series
UCLA, Dept of EEB

" Graduate Student Presentations "

Stephanie Chancellor

Researcher, Grether/ShierLab

Department of Ecology and Evolutionary Biology, UCLA


Octopus tetricus uses stereotypical displays in encounters that affect access to habitat patches or dens


At a unique site in Jervis Bay, Australia a unique site allows us to observe octopus social behavior previously unrecorded. By using GoPro video footage, we were able to re-identify some individuals on the site from past injuries or scars. This allowed us to follow individual octopus movement between patches. Here, I describe these interactions where one octopus already on the site attempts to prevent another octopus from obtaining a den. These interactions were categorized as on-site male-female, onsite male-male, entering male-female, entering male-male. We recorded whether the approaching octopus obtained a den at the end of the interaction, and the coloration and posture of each individual. I found that in onsite male-female interactions the female almost always remained in their den. Both individuals displayed the dark coloration. Males displayed the stand tall posture and females displayed the low posture. In entering male-female contests, females usually obtained a den when approaching the site. In these interactions females displayed the low posture and diematic coloration, whereas the male usually displayed the stand tall posture and dark coloration. For both, male-male entering and onsite interactions behaved similarly. Approaching males were usually prevented from gaining access to a den on the site by the onsite male. On-site males typically displayed the stand-tall posture and dark coloration, whereas the approaching male displayed the low posture and diematic coloration. I also documented mating behavior and found that individuals who prevailed in preventing others from gaining access to a den did not necessarily have more success when attempting to mate. These results demonstrate that octopuses at this site are engaged in complex social interactions.


Samantha Catella

Postdoc, Kraft Lab

Department of Ecology and Evolutionary Biology, UCLA


At the intersection of disease and community ecology: investigating how generalist pathogens and mutualists affect host competition


Difficulties quantifying pathogen load and mutualist abundance limit our ability to connect disease dynamics to host community ecology. For example, specific predictions about how differential pathogen load is hypothesized to drive host competitive outcomes are rarely tested. Additionally, although infection is known to affect mutualists, the magnitude of pathogen effects on mutualist abundance across host competitive contexts is rarely measured. We tested for both mechanisms in a plant–rhizobia–nematode system. We paired the legume Medicago lupulina with intraspecific and interspecific plant competitors, with and without a generalist
nematode parasite Meloidogyne sp. Relative change in plant biomass was used to determine how nematode inoculation affected plant competitive outcomes. We counted nematode galls to test for direct effects of parasitism on plant competition and rhizobia nodules to test for indirect effects of nematode presence on rhizobium abundance. Parasites were destabilizing despite similar nematode load across competition treatments. During interspecific compared with intraspecific competition, nematode inoculation decreased nodulation on M. lupulina, increased nodulation on Trifolium repens and had no effect on nodulation on Chamaecrista
fasciculata. We found no support for hypothesized direct effects of nematode load on competitive outcomes and strong but idiosyncratic indirect effects of nematode inoculation on rhizobium abundance.

Host: EEB Graduate Students