Right plant, right place, right pollinator? Evaluation of resource values, and pollinator visitation on native and nonnative plants under different water availability conditions

Background/Question/Methods

Pollinators are the subject of international interest as various studies document their declines and the multiple threats that they face, such as habitat fragmentation, loss of nesting sites, and climate change. Pollinator gardens are one conservation strategy to enhance pollinator diversity and abundance. However, not all gardens and garden plants have the same value for pollinators; native plants may best support native pollinators, but they do not represent all of the available floral resources within a complex landscape in which a great number of flowers are non-native. Non-native plants can have various benefits to pollinators depending on the floral rewards that they provide. Environmental conditions, such as water availability, can alter floral rewards and the relative value of native and non-native plants. Thus, to assess floral traits, floral rewards, and pollinator preferences between native and non-native plants under varying water irrigation, we measured nectar and pollen quantity, plant size, flower density, flower size, and pollinator visitation across 20 different plant species under two irrigation treatments in North and Central Florida. The 20 plant species studied represent congeneric pairs of native and nonnative species that were expected to show variability in floral traits, rewards, phenology, and pollinator attraction.

Results/Conclusions

Overall, native plants to Florida were bigger than non-native plants. However, plant growth did not differ between the two irrigation treatments. Native plants displayed fewer flowers than non-native plants under both irrigation treatments but offered more nectar regardless of water treatment. All the plant species were visited by pollinators and other insects. We counted over 7,000 pollinator visits from April to July 2021. Most of them were solitary bees (76.6%). Bumblebees were the second-most frequent pollinator group visiting the flowers (18.23%). Wasps (9.86%), honeybees (6.8%), butterflies and moths (6.41%), and flies (5.25%) visited in lower frequency. Pollinators more frequently visited native plants and plants under full irrigation treatment. Additionally, pollinator visitation was positively correlated with flower density per plot regardless of water treatment.