DOI: 10.5281/zenodo.18807894
title: Herbivory Weakens the Stability of a Floral Polymorphism

description: Herbivory Weakens the Stability of a Floral Polymorphism

Mia Gaughan1-2,7-8, Vincent S. Pan2-4,7-8, Sylvie Martin-Eberhardt2-3,5, William C. Wetzel6, Kadeem J. Gilbert2-5.

1:Department of Biology, Washington University in St. Louis, St. Louis, MO, USA

2: W. K. Kellogg Biological Station, Michigan State University, Hickory Corners, MI, USA

3: Department of Integrative Biology, Michigan State University, East Lansing, MI, USA

4: Ecology, Evolution, and Behavior Program, Michigan State University, Easting Lansing, MI, USA

5: Department of Plant Biology, Michigan State University, East Lansing, MI, USA

6: Land Resources and Environmental Sciences, Montana State University, Bozeman, Montana, USA





7: Corresponding authors: vsbpan [at] gmail [dot] com, gmia [at] wustl [dot] edu

8: Co-first authors

 



Dataset DOI: 10.5281/zenodo.18807895

 

General descriptions

480 Hesperis matronalis were subjected to an induction (clipping) treatment across 40 sites. We measured a bunch of fitness surrogates to look at whether herbivory affects frequency dependent selection. We performed a choice/no-choice assay to confirm what was going on with the herbivores. See the associated manuscript for more details on the methods.





 

Manuscript abstract

Herbivores have profound impacts on the maintenance of plant diversity. While simple optimal foraging models predict that herbivores should selectively attack common plant phenotypes, models that allow for differential plant resource acquisition can predict a preference towards rarer phenotypes, leading to the destabilization of intraspecific polymorphism. We show that herbivores may play such a destabilizing role in the dimorphic Hesperis matronalis system by weakening negative frequency-dependence. Across 40 patches of varying morph ratios, locally rarer H. matronalis morphs grew larger in the early season but received disproportionately more herbivory in the mid- and late season, leading to lower female fitness and survival. We rescued the advantage of being rare by experimentally reducing later herbivory through a plant immunity induction treatment. Feeding assays with a mustard-feeding caterpillar Trichopulsia ni confirmed that herbivores had higher survival on locally rare morphs and preferred to feed on rarer morphs. Our results are consistent with the hypothesis that herbivores may have evolved to use rarity as a cue to track resources, potentially weakening the advantage of being rare, a critical component of stable coexistence. We argue that this phenomenon of insect herbivores weakening the maintenance of plant diversity is extremely common in stable polymorphic systems.



 

Data descriptions

We use 'NA' to denote missing values in general.

base_map.jpg

This is a screen shot of google maps displaying the sites studied.

DRFDS_manuscript_cleaned_field_data_03_06_2025.csv

This is the field data + no-choice experiment. Each row is a plant or caterpillar that ate the specific plant.





This is the field data + no-choice experiment. Each row is a plant or caterpillar that ate the specific plant.




siteID: The unique identifier of the 40 sites




plantID: Unique plant identifier




trt: the clipping treatment of the plant (c = control, a = aggregated clipping, d = dispersed clipping)




leaf_number_pre: number of leaves counted before the leaves were clipped




largest_leaf_len_pre: largest leaf length in cm two days after the leaves were clipped




height: the height of the plant in cm roughly a month later clipping when the plant is flowering




herb_intensity: herbivory severity at the time of flower survey (n = no damage, l = low damage, m = medium damage, h = high damage)




flower_count: the number of flowers counted




date_flower_survey: moth-day-year of flower survey




date_trt: the date of clipping treatment (month-day-year)




lat: the latitude in degree decimals of the plant




lon: the longitude in degree decimals of the plant




notes: general notes




date_pollen_processed: the date pollen is scored




pollen_alive: the number of pollen grains counted that were stained red with tetrazolium (0.5% TTC for >24h)




pollen_dead: the number of pollen grains counted that did not stain with TTC




anther_prop_red: the proportion surface area of anther stained red in the TTC staining solution




anther_prop_red_logit: logit transformed anther_prop_red.




num_stalks: the number of stalks (either flowering or not flowering) of the same plant




leaf_feeding_start: the year-month-day H:M:S of when the no-choice leaf feeding assay with T. ni started




leaf_feeding_end: the year-month-day H:M:S of when the no-choice leaf feeding assay with T. ni ended




cat_wt: the milligram of the T. ni caterpillar post weight (after leaf feeding trial)




cat_dead: is the caterpillar dead after the no-choice feeding trial (1 = yes, 0 = no)




herbivory_assay_notes: notes specific to the no-choice herbivory assay




seed_collection_date: year-month-day of when the seeds were collected.




late_herb_prop: Proportion of herbivory on the plant in the late season survey




late_herb_survey_date: year-month-day of when late season herbivory was surveyed




late_herb_sruvey_notes: Notes specific to late season herbivory survey




silique_count: Number of siliques counted




silique_weight: the weight in grams of the siliques collected.




PC1: the first principal component of the RGB values of the scanned flower color




hex: the hex code of the scanned flower color




red: the red intensity (0-1) of the flower color




green: the green intensity (0-1) of the flower color




blue: the blue intensity (0-1) of the flower color




clipped: which clipping treatment did the plant get? (clipped: clipped; control: not clipped)




site_PC: The average PC1 value of all plants measured at a site




flower_color: a rough classification of flower color as either purple or white.




alive_next_year: whether the plant survived until next year (1: yes, 0: no)




next_year_survey_date: year-month-day of when the plant survival was surveyed




next_year_notes: notes specific to survival survey



DRFDS_manuscript_cleaned_choice_experiment_10_22_2023.csv

This is the choice experiment. Each row is a caterpillar.





containerID: The experimental arena ID




cat_sourceID: colony ID of where the caterpillar comes from




cat_pre_wt: Caterpillar pre-weight in milligrams




leaf_trt: Whether the leaf disk comes from a purple (p) or white (w) morph. Each leaf disk is ordered in a clockwise fashion, separated by a dash.




percent_herb: Percent herbivory on each leaf disk in the same order is leaf_trt




cat_post_wt: Caterpillar post weight in milligrams




date_experiment_setup: year-month-day of when of the experiment was setup




date_experiment_takedown: year-month-day of when the experiment ended




notes: general notes




dead: Did the caterpillar die by the end of the experiment? (1: yes, 0: no)



Code





DRFDS_analysis.html





The knitted output of the manuscript analyses






DRFDS_analysis.Rmd





The code for manuscript analyses






DRFDS_analysis_utils.R





Some functions used in DRFDS_analysis.Rmd for analysis.





Dependencies

A list of code dependencies, including their version numbers, can be found in the file dependencies.txt

Usage

Do whatever you want with the data. For questions, email Vincent Pan (vsbpan [at] gmail [dot] com).