Determining the plant-pollinator network in a culturally significant food and medicine garden in the Great Lakes region

Determining the plant-pollinator network in a culturally significant food and medicine garden in the Great Lakes region

ABSTRACT

Understanding the interactions between plants and pollinators within a system can provide information about pollination requirements and the degree to which species contribute to floral reproductive success. Past research has focused largely on interactions within monocultured agricultural systems and only somewhat on wild pollination networks. This study focuses on the culturally significant Three Sisters Garden, which has been grown and tended by many Indigenous peoples for generations in the Great Lakes Region. Here, the plant-pollinator network of the traditional Three Sisters Garden with the inclusion of some additional culturally significant plants was mapped. Important visitors in this system included the common eastern bumble bee, Bombus impatiens Cresson, and the hoary squash bee, Xenoglossa pruinosa, as determined by their abundances and pollinator service index values. Understanding the key pollinators in the Three Sisters Garden links biological diversity to cultural diversity through the pollination of culturally significant plants. Further, this information could be of use in supporting Indigenous food sovereignty by providing knowledge about which wild pollinators could be supported to increase fruit and seed set within the Three Sisters Garden. Our findings can also lead to more effective conservation of important wild pollinator species.

INTRODUCTION

Pollination is a mutualistic interaction between two levels of the food web-plants and their pollinators. Network theory has been used in the evaluation of mutualistic interactions, and the interactions are cumulatively referred to as a plant-pollinator network. While plant-pollinator network characteristics such as asymmetry and nestedness make them theoretically robust, there is potential for anthropogenically driven environmental disturbance to eventually collapse plant-pollinator networks.

Plant-pollinator networks are negatively impacted by various factors including habitat fragmentation and land use changes, conventional agricultural practices, non-native species introductions, and increasingly, climate change. Documenting these mutualisms and modeling how they respond to change are integral to the conservation and restoration of ecological networks. Studying plant-pollinator networks helps to fill in baseline information about the ecological role of wild bees and to understand the stability and/or resiliency of the network to environmental change. The loss of even a single species can have significant effects on reproductive success of the plants within a system. Declines of pollinators within a network can contribute to negative feedback of less floral reproduction, which then in turn contributes to fewer resources for pollinators. Wild pollinators provide significant levels of pollination services to crops, yet the details such as the level of pollinator abundance or diversity required to provide adequate pollination of these relationships remain relatively unknown. Pollination deficits are a threat to global food security.

There have been efforts recently to increase food production without increasing the level of environmental harm from agriculture. Intercropping is a practice that may increase yield and promote sustainable land and resource use. Intercropping has also been suggested as a method of reducing agricultural causes of pollinator decline. The Three Sisters method of cultivation is a polyculture practice intercropping involving the growth of multiple crops simultaneously.

Archaeobotanical remnants in the forests and prairies of Canada show evidence of corn domestication as early as five hundred A.D. and common bean and squash cultivation in the Woodland period. The Three Sisters were grown for five hundred years pre-contact by the Seneca people in western New York and were referred to as "Diohe'ko", which translates to "these sustain us". The Haudenosaunee people, people of the long house, of the Eastern United States and Canada have traditionally planted the Three Sisters Garden. Broadly, it has been reported that the Three Sisters were grown by all tribes who practiced agriculture in northeastern North America. This study aims to better understand the pollinator community and plant-pollinator network in a Three Sisters Garden, known as a TSG. The Three Sisters Garden is composed of corn, Zea mays L., common bean, Phaseolus vulgaris L., and squash, Cucurbita L. sp.

Cucurbita plants, pumpkins, squash, gourds, are monoecious and rely on insect pollination; each plant has both pistillate, female, and staminate, male, flowers

Flowers open at dawn and close by noon each day, and pollination must occur within this window. Xenoglossa pruinosa is an oligolectic bee species, foraging only on the flowers of Cucurbita crops and wild Cucurbita species where they are present. The hoary squash bee's natural geographic range has increased over the past one thousand years following the spread of squash planting for agricultural purposes. Domesticated squash has been receiving pollination by wild pollinators prior to the introduction of the western honey bee, Apis mellifera. Phaseolus vulgaris is self-compatible, i.e., able to self-pollinate as the flower opens and provides little, if any, nectar. It is also noted, however, that the reproductive success of the plant (seed yield) can be increased by visits from larger bees. Phaseolus coccineus has been found to set few pods without the presence of insect visitors. Zea mays is wind pollinated and therefore does not rely on insects for pollination; however, insects may visit the flowers.

In some cases, sunflowers would be grown along one side of the Three Sisters Garden; it has been reported that this was done to attract pollinators to the garden. Other plants, including Hopi tobacco, purple coneflower, common milkweed, wild bergamot, Oswego tea/bee balm, and American vervain, are also planted in some food and medicine gardens.

The Three Sisters Garden is a growing method with long biological and cultural roots, and medicine plants are important to many Indigenous cultures. A better understanding of the pollinator community and plant-pollinator network in the Three Sisters Garden will provide information about the wildlife that provides ecological services to this kind of garden and thus the pollinators that are connected to Indigenous food and medicine sovereignty. Intercropping also offers a sustainable agricultural practice that may be useful, specifically in urban agriculture.

The objective of this study is to map the plant-pollinator network in the culturally significant Three Sisters garden and determine if and how the pollinator community in the garden differs from the local wild pollinator community based on pan-trap sampling in adjacent, natural sites and in the context of other regional studies. These baseline conditions will be useful for predicting how the Three Sisters Garden system may be impacted by environmental change into the future.