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Data from: Seed predator effects on plants: moving beyond time-corrected proxies

Citation

Ortega, Yvette; Dylewski, Łukasz; Bogdziewicz, Michał; Pearson, Dean (2022), Data from: Seed predator effects on plants: moving beyond time-corrected proxies, Dryad, Dataset, https://doi.org/10.5061/dryad.hqbzkh1fp

Abstract

Small mammals impact plant recruitment globally via size-dependent seed predation, generating a unimodal pattern across ecosystems. Chen et al. (2021) critiqued our seed removal analysis, advocating corrections for exposure time. We show in our rebuttal that such manipulations are unwarranted and argue for increased emphasis on plant recruitment metrics. This archive holds the updated seed removal dataset used for our rebuttal.

Methods

To construct the original dataset analyzed in Dylewski et al. (2020), we conducted a global literature review to obtain data related to small mammal effects on plant species.  The subject of this archive is specifically the seed removal dataset based on studies wherein researchers offered seeds in the field to quantify seed removal rates by post-dispersal seed predators.  

To obtain studies that quantified small mammal seed removal rates, we first considered data from the global literature review conducted by Moles et al. (2003; Ecology, 84, 3148-3161).  We then supplemented these studies with more recent work (published from January 2002 through November 2019) by searching the Web of Science Core Collection for peer-reviewed studies using the search term combination: ("seed remov*" OR "seed predat*" OR "seed offer*") AND ("small mammal*" OR "rodent*" OR "granivor*").  We also screened studies found through this search for relevant citations.

From this literature pool, we filtered studies based on the following criteria.  All studies considered for our evaluation were conducted in natural systems, i.e. not urban or agricultural settings.  In this definition, we included European grasslands, which are often sustained by mowing, and North American old-field systems, which are seral stages of post-agricultural systems returning to their natural state.  We focused on studies examining primarily seeds, not fruits, though studies incorporating seeds removed from fruits were included.  Likewise, seeds attached to well-developed samara or samara-like dispersal structures (e.g., Acer, Fraxinus) were excluded, as these adaptations can affect total diaspore mass and shape in ways that alter seed handling and removal.  Seed offerings above the ground surface were excluded.  Because consumer origins could influence outcomes (Parker et al. 2006), we also excluded studies where small mammal seed predators could be identified as introduced (e.g., from some island systems), as these were too few to address consumer origins in analyses.  In all cases, only studies that reported results by individual plant species could be included.  Additionally, given that study-level variables such as study design, seed predator community, and environmental context (e.g., background resource levels, competition, etc.) could have large effects on measured responses, we only included studies that provided data for >1 plant species to control for such variation.  

Data from qualifying studies were extracted directly from the text or tables of publications, or from figures using Web Plot Digitizer Version 4.0 (https://automeris.io/WebPlotDigitizer/).  We obtained data on the proportion of seeds removed per plant species during seed removal trials.  In studies reporting multiple seed removal rates per species, we used the following rules to select one value (to overcome the complication of trying to account for non-independence among species x study replicates in models).  When seed removal studies presented data for multiple trials or time points per species, we used data from the last or longest reported time interval with one exception: if the removal rate approached 100% for multiple plant species (potentially truncating responses), we used the middle trial or median time point.  In studies presenting data for multiple sites or ecological contexts (e.g., variation by habitat, distance from habitat edge, or forest age), we randomly chose a single scenario.  

Geographic and habitat information was recorded for all studies.  The latter was used to define the following ecosystem types: grasslands (including European grasslands and old-field systems as defined above), temperate forest, tropical forest, and other (e.g., desert, shrublands, coastal dunes).  Plant species provenance (i.e., native or exotic) was taken directly from the study when possible (most cases), and otherwise from the Plants of the World online database (Royal Botanic Gardens Kew 2020).  Seed mass data for studies from Moles et al.’s (2003) global review were obtained from Appendix I in that publication.  For remaining studies, we gathered seed mass data directly from the source publication or a related publication when possible (85% of cases).  If authors did not include seed mass, we obtained this information from the following published databases, prioritized in the order listed: Seed Information Database (Royal Botanic Gardens Kew 2019), LEDA for Northwest European flora (Kleyer et al. 2008), and Botanical Information and Ecology Network Database (Maitner et al. 2018).  In cases where multiple seed masses were given per species in a database, we chose the record from the most proximate geographic region, when given, otherwise we chose the first record listed.  Seed mass (+1) was natural log-transformed for analysis. 

For our rebuttal to Chen et al. (2021), the original seed removal dataset from Dylewski et al. (2020) was updated as follows: 1) related data extracted by Chen et al. (2021) were incorporated, revised, and used to make new variables that accounted for seed exposure time, and 2) a few minor errors were fixed as described in Appendix S1 of our rebuttal.

Usage Notes

All variables included in the dataset are detailed on the README tab within the file.

Funding

Polish NSC Etiuda Fellowship, Award: 2018/28/T/NZ8/00264

Narodowa Agencja Wymiany Akademickiej, Award: POWR.03.03.00-IP.08-00-P13/18

Rocky Mountain Research Station, Award: PI S76yyyyyyalary

Polish NSC Etiuda Fellowship, Award: 2018/28/T/NZ8/00264