Refocusing the study of human-plant relations to the genus scale: Indigenous selection pressures in Xanthosoma

Domestication and conservation research often relies on single-species frameworks, which can obscure how Indigenous management practices applied to multiple related taxa may interact to shape shared gene pools. Studies of crops such as manioc/cassava (Manihot esculenta), yam (Dioscorea spp.), sorghum (Sorghum spp.), and Amazonian treegourd (Crescentia spp.) demonstrate that domestication frequently involves interactions among multiple cultivated and wild or semi-managed relatives. However, little is known about how these dynamics operate within the genus Xanthosoma, particularly in the Ecuadorian upper Amazon, a key center of diversity and domestication history for the genus. This gap limits understanding of how Indigenous management practices may influence the maintenance, erosion, or redirection of genetic diversity, with implications for crop improvement, resilience under changing environmental conditions, and the identification of underutilized plant resources.

We combined ethnobotanical fieldwork in the Runa community of Mondayacu-including structured and unstructured interviews, participant observation, and genus-focused walks-with a national-level syntheses of herbarium records and ethnobotanical literature to contextualize Xanthosoma diversity and use across Ecuador. Interview responses were topically coded and summarized as aggregated frequencies, with patterns visualized using bar graphs. Descriptive statistics summarized reported management, while qualitative quotations and participant observation grounded interpretation.

Participants reported no current cultivation of Xanthosoma sagittifolium, despite its historical importance in Mondayacu and broader global use. In contrast, participants described a spectrum of management practices for lalu (Xanthosoma purpureomaculatum), ranging from eradication to selective retention for medicinal, zootechnical, and ritual uses. Lalu was the most commonly observed Xanthosoma species during fieldwork and was perceived as highly persistent, rapidly regrowing and spreading across forests and semi-managed areas. Decisions to remove or retain plants were trait- and context-dependent, with individuals exhibiting desirable characteristics (e.g., large, deep green leaves, minimal pest damage) preferentially spared or relocated near houses or gardens. National-level herbarium and ethnobotanical synthesis documented broader Xanthosoma species diversity, multifunctional uses, and possible selection pressures across Ecuadorian Amazonian Indigenous groups.

Building on evidence from other crop systems, our findings suggest that domestication dynamics in Xanthosoma are not fully captured by a single-species framework. In a key center of Xanthosoma diversity and domestication history, differential management of multiple related species may contribute to shaping patterns of persistence and diversity within the genus. While this study does not directly measure genetic change, it identifies ethnobotanical processes that may influence the distribution and maintenance of diversity across related taxa, including those in secondary and less-studied gene pools. Approaches that account for genus-level diversity and Indigenous management practices may therefore improve understanding of domestication processes and support conservation of genetic diversity, crop improvement, and the identification of underutilized plant resources. These findings also contribute to decolonizing domestication research by highlighting how Indigenous knowledge systems and management practices shape the structure and future of crop diversity.