Most of what is known about the ways in which strongly interacting species affect ecological communities stems from changes to community structure revealed in contemporary research. However, trophic downgrading has limited the temporal extent to which inferences can be drawn. The aim of my Dissertation was to expand on the strongly interacting species concept by examining species interactions at a historical scale, in a textbook example of a strongly interacting and keystone predator. The sea otter, Enhydra lutris, was driven to near-extinction but is recovering in parts of its range, providing a mosaic of areas with and without sea otters. This mosaic allowed for a series of natural experiments, which I conducted using behavioural observations, genetic tools, and archaeological methods, to examine sea otter effects spanning contemporary (last ~40 yrs.), and late-Holocene (~3500-150 yrs. ago) timeframes, and on an evolutionary scale that inferred middle-Pleistocene interactions. In Chapter 2, my coauthors and I found that sea otter use of clam-based niches increased as occupancy-time increased, and that bachelor groups of male otters primarily inhabited these niches, findings that informed and inspired subsequent questions. In Chapter 3, we found that where sea otters were established for 20-30 years, the disturbance to eelgrass (Zostera marina), caused by sea otters digging for clams and other infaunal prey, was correlated with ~25% greater eelgrass allelic richness than where otters were present <10 yrs, or absent. We posit that sea otter digging has long-influenced the genetic diversity and resilience of eelgrass – perhaps since the middle Pleistocene. In Chapter 4, we asked how two strongly interacting species – people and sea otters – co-existed for millennia where they both consumed clams. We used assemblages of live and otter-cracked butter clams (Saxidomus gigantea), to confirm the ecological effects that sea otters exert today. We measured clams from archaeological assemblages in areas densely populated with clam gardens – terraced beaches that enhance clam habitat and productivity – and found that sea otters reduced the sizes of ancient clams, acting as ecologically effective predators in the mid-to-late Holocene. However, clam harvests were stable for thousands of years, with or without otters. We suggest that clam gardening supported coexistence of people and otters in the past, and could function the same way today. Collectively, we found that a few, perhaps long-forgotten, interactions increased the breadth of the strongly interacting species concept. In Chapter 5, I suggest that such rediscoveries could occur in other systems. Many large vertebrates have suffered population declines, but the most insidious losses accompanying these, are the losses of ecological interactions that become unknowable, and thus cannot be intentionally restored. By searching out ancient interactions, long-forgotten relationships have the potential to be recovered, and to inform our understanding of contemporary systems. / Graduate / 2022-09-10

This thesis focuses on the traditional cultivation of an edible root species by Kwaxsistalla, Clan Chief Adam Dick, of the Qawadiliqalla Clan, of the Dzawada ēnuxw, a subgroup of Kwakwaka’wakw, occupying the Kingcome Inlet area on the Central Coast of British Columbia. Kwaxsistalla is a traditionally trained Clan Chief and potlatch speaker with recognized authority to share his detailed knowledge and experiences of his clan’s food production system. This research is centered on his Clan’s tekkillakw (estuarine salt marsh root garden) root gardens of the Kingcome River estuary, and the long-standing practices associated with the large-scale production of tleksem Pacific silverweed [Argentina egedii (Wormsk.) Rydb.; syn. Potentilla pacifica (L.) Howell.], is one of the four cultivated root species. Kwaxsistalla has shared his hands-on knowledge of how root garden cultivation fits into his family’s seasonal patterns of food production as well as detailed accounts of how to construct and use tools for cultivating, weeding, harvesting, and cooking estuarine roots. He has also provided information that has been instrumental in developing a model of aboriginal management of estuarine root gardens (Deur 2005). This thesis builds on Deur’s model by attempting to experimentally replicate tekkillakw management in order to better understand the management effect on the abundance, size, and flavour of Argentina egedii roots. Over the course of the 2008 growing season I randomly subjected 60 ¼ square meter patches of Kwaxsistalla’s fallow tekkillakw to either a “till” or “till + weed” treatment and allocated 30 similar patches as a control. I applied a roto-tilling treatment just prior to the growing season, a weeding treatment mid-summer, and harvested the roots near the end of the growing season. While the short duration of my study and use of a roto-tiller limit the inferential power of my results, I found that tilling and weeding significantly increased the abundance or A. egedii but significantly decreased the root size. Throughout the same 2008 field season I also collected root specimens for analysis of their bitter and sweet constituents and found (bitter) tannins concentrations to be highest in the late summer and lowest in the spring and fall. / Graduate