Plant invasion reduces density-dependent pollination but not florivory

Abstract Understanding the impact of plant invasion on multitrophic community dynamics and coexistence requires widespread and frequent monitoring. Deep learning can be used to automate the measurement of indicators of ecological interactions and ecosystem functioning. In this study, we used a consumer grade drone paired with deep learning to assess floral density in meadows invaded by the dog-strangling vine Vincetoxicum rossicum (Kleopow) Barbar. (Gentianales: Apocynaceae) in the Rouge National Urban Park in the Greater Toronto Area, Ontario, Canada. Alongside these measurements, observations of pollination and herbivory was completed on Symphyotrichum novae-angliae (L.) G.L.Nesom (Asterales: Asteraceae), a self-incompatible, pollinator-dependent native plant that experiences herbivory by a widespread specialist weevil, Anthonomus rufipes LeConte (Coleoptera: Curculionidae). Our results suggest that as invasion progresses, pollination services are reduced due to the decrease in floral density which suppresses pollinator abundance and activity. Conversely, while herbivory had a strong effect on plant reproduction, it was density-independent and thus unaffected by direct effects of invasion, but rather indirect through reduced host abundance. By pairing deep learning with drone technology, we detected patterns consistent with a reduction of pollinator habitat quality along the invasion gradient. Furthermore, we find that invasion appears to suppress plant reproduction by means of separate processes that are either independent of or dependent on pollination. Overall, the results suggest that invasion reduces pollinator habitat quality while simultaneously resulting in ecological conditions consistent with the reproductive impairment of late season flowering resident plant species.
Description of the data and file structureThis repo contains three CSV files.
'site_floral.csv' is data on late-summer floral resource availability at nine sites in the Rouge National Urban Park, Toronto, Canada during the summer of 2021.'pollination_service.csv' is data on pollination services (i.e., pollinator visitor rate, plant reproductive output) of 30 Symphyotrichum novae-angliae plants measured in Rouge National Urban Park during the late-summer and early-fall of 2021.'comm_data_matrix.csv' is the community data matrix tabulated insects collected on monitored Symphyotrichum novae-angliae plants measured in Rouge National Urban Park during the late-summer and early-fall of 2021.Files and variables File: site_floral.csvDescription & variables: Site level data used to test hypothesis A  
site_id: Unique code assigned to each sites (unitless)relative.cover_SOSP: Drone-based measure of relative percentage floral cover of Solidago species      for each site (%) relative.cover_SYER: Drone-based measure of relative percentage floral cover of Symphyotrichum      ericoides and Symphyotrichum lanceolatum for each site (%)relative.cover_SYNO: Drone-based measure of relative percentage floral cover of Symphyotrichum      novae-angliae for each site (%)File: pollination_service.csv Description & variables: data on pollination services provided to individual monitored plants that was used to test hypothesis B 
site_id: Unique alphanumeric code assigned to each site (unitless)plant_id: Unique alphanumeric code assigned to each measured plant (unitless)period: Sample period. 0 = late-summer, 1=early-fallcover_VIRO: Average relative percentage vegetative cover of Vincetoxicium rosscium across  25 1-m2 quadrats for each site (%)relative.cover_SYNO: Drone-based measure of relative percentage floral cover of Symphyotrichum novae-angliae for each site (%)visitor_abun: Total number of insect pollinators observed during 15-minute timed observation      period to plant (unitless)flower_n: Total number of floral heads counted on plant prior to timed observation period      (unitless)Nh_prop: The proportion of seeds with herbivory damage across fruits collected from plant (unitless)Nv: Total number of viable seeds across fruits collected from plant (unitless)M: Total mass of seeds across fruits collected from plant (mg)N_fruit: Number of fruits collected from plant (unitless) File: comm_data_matrix.csv Description & variables: community data matrix of insect pollinators collected during timed observation periods
site_id: Unique alphanumeric code assigned to each site (unitless)plant_id: Unique alphanumeric code assigned to each measured plant (unitless)period: Sample period. 0 = late-summer, 1=early-fallColumns 4 to 19: Each column is the abundance of individuals of a given taxon identified to genus or species (unitless)