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Agricultural landscape simplification affects wild plant fitness indirectly through herbivore-mediated changes in floral display

Cite this dataset

Schroeder, Hayley (2024). Agricultural landscape simplification affects wild plant fitness indirectly through herbivore-mediated changes in floral display [Dataset]. Dryad. https://doi.org/10.5061/dryad.905qfttt6

Abstract

As natural landscapes are modified and converted into simplified agricultural landscapes, the community composition and interactions of organisms persisting in these modified landscapes are altered. While many studies examine the consequences of these changing interactions for crops, few have evaluated the effects on wild plants. Here, we examine how pollinator and herbivore interactions affect fitness for wild resident and phytometer plants at sites along a landscape gradient ranging from natural to highly simplified. We tested the direct and indirect effects of landscape composition on plant traits and fitness mediated by insect interactions. For phytometer plants exposed to herbivores, we found that greater landscape complexity corresponded with elevated herbivore damage, which reduced total flower production but increased individual flower size. Though larger flowers increased pollination, the reduction in flowers ultimately reduced plant fitness. Herbivory was also higher in complex landscapes for resident plants, but overall damage was low and therefore did not have a cascading effect on floral display and fitness. This work highlights that landscape composition directly affects patterns of herbivory with cascading effects on pollination and wild plant fitness. Further, the absence of fitness consequences for resident plants suggests that they may be adapted to their local insect community. 

README: Agricultural landscape simplification affects wild plant fitness indirectly through herbivore-mediated changes in floral display

https://doi.org/10.5061/dryad.905qfttt6

Files

Phytometer_Plants: This data file has a single line for each phytometer plant in the experiment. See data included in this file below.

Resident_Plants: This data file has a single line for each resident plant in the experiment. See data included in this file below.

Landscape: This data file includes all the landscape data used to evaluate landscape composition at each site across three scales. Landscape data was gathered from the USDA Cropland Data Layer and summarized into the categories agriculture, natural (non-forested), and pasture. See the full distribution of landscape categories below.

Collected_Pollinators: This data file includes all the insects collected by sweep netting a B. vuglaris patch neighboring the focal resident patch. Each insect was identified to the highest level possible given available expertise and were cataloged and deposited into the Cornell Insect Collection.

Data_for_Grouped_Analysis: This data is a summarized file including both resident and phytometer plants to do general comparisons of damage, visitation, flower size, and seed set.

Tabular Data Descriptions

Phytometer_Plants and Resident_Plants

Plant_ID: Unique number assigned to each plant.

Site: Code for each for the sites

Damage_Whole_Plant: Percentage leaf tissue removed by herbivores, visually estimated

Herbivore_Exclusion: Plants with mesh bags to exclude herbivores (Y) or without mesh bags(N)

Focal_Density: The density of B. vulagaris plants at each site (plants/m^2)

Observation_Time: Total time each plant was visually observed for pollinator visits in minutes

Honey_Bee through Other_Fly: Total number of visits that a plant received from insects classified in each of these morpho species. NA’s indicate a plant did not have accessible blooms at the time visitation data was collected.

Lasio_by_Time: Total number of Lasioglossum visits divided by the total time a plant was observed (visits/min). NA’s indicate a plant did not have accessible blooms at the time visitation data was collected

All_Bees_by_Time: Total number of bee visits divided by the totala time a plant was observed (visits/min). NA’s indicate a plant did not have accessible blooms at the time visitation data was collected

Bagged_Y_N: This indicates wether or not a pollinator exclusion bag was placed on a plant. Pollinator exclusion bags were placed depending on the availability of blooms at the time each site was visited.

Petal.L: Length of the longest petal of a flower collected from each plant, pasted to a sheet of paper and measured using a microscope (mm). NA’s indicate a plant did not have accessible blooms at the time flowers were collected.

Petal.W: Width of the longest petal of a flower collected from each plant, pasted to a sheet of paper and measured using a microscope (mm). NA’s indicate a plant did not have accessible blooms at the time flowers were collected.

Stigma: Length of stigma in mm. NA’s indicate a plant did not have accessible blooms at the time flowers were collected.

Stamen: length of longest stamen (anther and filament) in mm. NA’s indicate a plant did not have accessible blooms at the time flowers were collected.

UB_Fertile: Total seed pods not in a pollinator exclusion bag that were fertile (had at least one seed forming inside). NA’s indicate missing data.

UB_Aborted: Total seed pods not in a pollinator exclusion bag that did not successfully set seed (no seeds formed). NA’s indicate missing data.

UB_Prop_Fertile: Proportion of all unbagged seed pods that successfully set seed. (UB_Fertile/(UB_Fertile + UB_Aborted))

Non_Reproductive_Mass: Mass of rosette leaves collected when plants were harvested and dried in a drying oven at 50 degrees C. NA’s represent missing data. This variable is only available for Phytometer plants because the Resident plants did not have any leaves present when the plant were harvested.

B_Fertile: Total seed pods in pollinator exclusion bags that successfully set seed (had at least one seed forming inside). NA’s represent plants that did not have pollinator exclusion bags.

B_Aborted: Total seeds in pollinator exclusion bags that did not successfully set seed (no seeds formed). NA’s represent plants that did not have pollinator exclusion bags.

B_Prop_Fertile: Proportion of all bagged seed pods that successfully set seed.

PC1: PC1 values from a principal component analysis summarizing pasture, natural, and agricultural land cover at three scales (500, 1000, and 1500m) for each site. Higher values indicate a greater proportion of agriculture in the surrounding landscape and lower values indicate a greater proportion of open (non-forested) natural area and pasture.

Pollinator_Contribution: The difference between the proportion fertile of the un-bagged portion of the plant and the bagged portion. NA’s indicate plants that did not have both bagged and unbagged portions.

Total_Unbagged_Flowers: Total flowers not in pollinator exclusion bags (the sum of total fertile and total aborted unbagged pods)

Total_Flowers: Total flowers produced by the plant (bagged and unbagged). Calculated by adding together all fertile and aborted seed pods on both bagged and unbagged portions.

Log_Damage: Log of the Whole_Plant_Damage variable, created to improve model fit.

Bagged_Flowers: Total flowers in pollinator exclusion bags (aborted plus fertile pods).

Estimated_Bagged_Fertile: Based on the proportion fertile for the unbagged portion of the plant, we calculated how many of the available flowers would have set seed if they had been accessible to pollinators. (calculated by multiplying Bagged_Flowers variable by UB_Prop_Fertile)

Total_Seed_Set: Estimated total fertile seed pods produced by a plant including both the actual fertile pods counted on the unbagged portion of the plant and the estimated fertile pods for the bagged portion. This raw value was normalized using the scale function in R to produce the values in this column.

All_Bees: Sum value of all bee visits a plant received

All_Visitors: Sum count of all insect visitors observed

Fly_Visits: Sum count of all flies observed visiting each plant

Lasio_Visits: Sum count of all Lasioglossum visits to each plant. Lasioglossum were singled out because they were the most frequent visitor to B. vulgaris.

Total_Flowers_Normalized: Total_Flowers variable (see above), normalized to improve model fit using the scale() function in R

Petal_L_Normalized: Petal.L variable (see above), normalized to improve model fit using the scale() function in R.

Plant_Biomass_Normalized: Non_Reproductive_Mass variable (see above), normalized to improve model fit using the scale() function in R. This variable is only available for Phytometer plants because there were no leaves on Resident plants when harvested.

All_Visitors_by_Time: The sum of all observed visitors divided by the total observation time.

All_Hoverfly: The sum of all observed hover fly visits.

All_Hoverfly_by_Time: The sum of all observed hover fly visits divided by the total observation time.

Landscape (CDL_2020_Barbarea_Final)

AG_500: This variable includes the following CDL classifications within a 500m radius of each experimental site; Corn, Sorghum, Soybeans, Sweet corn, Barley, Spring wheat, Winter wheat, Rye, Oats, Alfalfa, Buckwheat, Dry beans, Other Crops, Miscellaneous vegetables and fruits, Onion, Peas, Pears, Fallow/Idle Cropland, Triticale, Squash, Pumpkins, Cabbage, Double Crop Oats/corn, Peaches, Apples, Grapes, Christmas Trees, Clover Wildflowers.

PAST_500: This variable includes the following CDL classifications within a 500m radius of each experimental site; Other Hay Non-alfalfa, Grassland Pasture.

NAT_OPEN_500: This variable includes the following CDL classifications within a 500m radius of each experimental site; Clover Wildflowers, Shrubland, Herbaceous Wetlands, Developed Open Space

NAT_FOR_500: This variable includes the following CDL classifications within a 500m radius of each experimental site;Deciduous Forest, Evergreen Forest, Mixed Forest, Woody Wetlands.

DEV_500: This variable includes the following CDL classifications within a 500m radius of each experimental site; Developed Low Intensity, Developed Medium Intensity, Developed High Intensity.

NAT_500: This variable includes the following CDL classifications within a 500m radius of each experimental site; Clover Wildflowers, Shrubland, Herbaceous Wetlands, Developed Open Space, Deciduous Forest, Evergreen Forest, Mixed Forest, Woody Wetlands.

NAT_PAST_500: This variable includes the following CDL classifications within a 500m radius of each experimental site; Clover Wildflowers, Shrubland, Herbaceous Wetlands, Developed Open Space, Other Hay Non-alfalfa, Grassland Pasture.

AG_PAST_500: This variable includes the following CDL classifications within a 500m radius of each experimental site; Corn, Sorghum, Soybeans, Sweet corn, Barley, Spring wheat, Winter wheat, Rye, Oats, Alfalfa, Buckwheat, Dry beans, Other Crops, Miscellaneous vegetables and fruits, Onion, Peas, Pears, Fallow/Idle Cropland, Triticale, Squash, Pumpkins, Cabbage, Double Crop Oats/corn, Peaches, Apples, Grapes, Christmas Trees, Clover Wildflowers, Other Hay Non-alfalfa, Grassland Pasture.

AG_1000 through AG_PAST_1500: Each of these variables includes the same CDL classifications as at the 500m scale, just expanded to a 1000 and then 1500m radius.

Collected_Pollinators

X: Unique code for each collected insect

CUIC_Code: Unique identifier cataloging each insect within the Cornell Insect Collection. NA’s indicate damaged insects that could not be identified.

Country: Country where insects were collected.

State.Province.Territory: State where insect was collected.

County: County where insect was collected.

Site: Unique identifier for experimental site.

Day: Day of the month the insect was collected.

Month: Month of the year the insect was collected.

Year: Year the insect was collected.

Count: Count column to aid in summarizing data.

General_ID: Broad classification of insect based on common names.

Family: Taxonomic Family

Genus: Taxonomic Genus

Specific_Epithet: Taxanomic Specific Epithet

Species: Species identification

Sex: male or female

Method: How insects were collected (target sweep indicates insects that were collected via sweep netting a neighboring B. vulgaris patch). Numbers indicate which individual plant an insect was collected from.

Observation_Time: This variable indicates how long the collection period was in which an insect was collected in minutes.

Damaged: Here insects labeled “Y” were too damaged to be identified.

Notes: Details about the individual insect, particularly damage

PC1: PC1 values from a principal component analysis summarizing pasture, natural, and agricultural land cover at three scales (500, 1000, and 1500m) for each site. Higher values indicate a greater proportion of agriculture in the surrounding landscape and lower values indicate a greater proportion of open (non-forested) natural area and pasture.

Data_for_Grouped_Analysis

Plant_ID: Unique number assigned to each plant.

Site: Code for each for the experimental sites.

Estimated_Damage: Percentage leaf tissue removed by herbivores, visually estimated for the whole plant.

All_Bees_by_Time: Total number of bee visits divided by the totala time a plant was observed (visits/min). NA’s indicate a plant did not have accessible blooms at the time visitation data was collected.

Petal_Length: Length of the longest petal of a flower collected from each plant, pasted to a sheet of paper and measured using a microscope (mm). NA’s indicate a plant did not have accessible blooms at the time flowers were collected.

Treatment: This variable indicates if a plant was a phytometer or resident plant and, within phytometer plants, whether it had herbivore exclusion or not.

Total_Seed_Set: Estimated total fertile seed pods produced by a plant including both the actual fertile pods counted on the unbagged portion of the plant and the estimated fertile pods for the bagged portion.

Methods

This study was conducted in upstate NY, USA. Experimental sites were in field margins of farms that were selected along a gradient ranging from landscapes dominated by natural land cover to landscapes dominated by agriculture. Phenotypic data, pollinator visitation, herbivore damage, and plant fitness was measured on Barbarea vulgaris plants existing naturally at each site (resident plants) and on sentinel plants grown from a single parent plant (phytometer plants). Phytometer plants provide a useful tool for evaluating changing interactions for wild plants by minimizing the contribution of adaptive trait variation which, in resident populations, may be compensating for landscape mediated changes in insect interactions. To analyze the data collected we examined how insect interactions and plant traits varied along the landscape gradient and how these variables interacted using structural equation models. 

Funding

National Science Foundation