DOI: 10.5061/dryad.dbrv15fdg
title: Dominant deer mice show the importance of abundance in competition

description: Detecting competitive interactions is important for predicting species
 responses to environmental change, but it remains challenging, especially
 over large scales. Based on classical coexistence theory, competition
 should be most important between species with similar ecological traits
 (i.e., diet, habitat). However, species with life-history traits that
 allow them to be very prolific can have competitive effects even with
 subtle ecological overlap. Such species may be able to achieve such high
 abundances that they dominate all other competitors (i.e., “dominant
 entities”). We tested for competition and the importance of dominant
 entities in small mammal communities (n = 68 species) at 44 sites in 18
 regions across the United States using the US National Ecological
 Observatory Network (NEON). We based inference on changes in abundance
 over time while also accounting for weather and habitat factors using a
 dynamic generalized joint attribute modeling framework. We compared
 relative interaction strengths inferred from our model to predictions
 expected under coexistence theory based on ecological and life history
 traits. We used three different cutoff levels to classify a species (or
 set of species) as dominant entities: &gt;= 45 % of the total
 interaction strength, &gt; 50 % of the total abundance at a site and a
 relatively large number of strong interactions (&gt; 10 % of total
 interaction strength at the site). Predictions of competition based on
 coexistence theory were not well supported by model results (mean = 0.25,
 SE = 0.03). Our model indicated more sites with dominant entities than
 predicted by coexistence theory. In particular, our model identified three
 generalist Peromyscus species as the dominant entities at more sites (53.1
 % vs. 0 %), associated with higher mean interaction strength at a site
 (58.0 % [SE = 7.5 %] vs 13.8 % [SE = 1.4 %]) and a higher proportion of
 strong interactions with other species at a site (46.2 % [SE = 4.4 %] vs.
 26.7 % [SE = 1.7 %]). Model results more closely matched large-scale
 observed abundance patterns than did theory-based predictions, suggesting
 that accounting for dominant entities is important for characterizing
 competitive interactions. Our study shows the potential of using changes
 in abundance over time to make inference on community change while
 accounting for competitive interactions, where reliance on
 presence/absence and/or ecological traits alone could miss important
 dynamics.
description: # Dryad dataset Dataset DOI:
 [10.5061/dryad.dbrv15fdg](10.5061/dryad.dbrv15fdg) ## Description of the
 data and file structure Ecological traits included in our analysis from
 the COMBINE mammal trait database (Soria et al. 2021) and were:
 fossoriality, arboreality, diet (i.e., the proportion of the diet made up
 of invertebrates, vertebrates, fruit, nectar, seeds and plants,
 respectively [note: per = percentage]), diet breadth (i.e., the number of
 different diet categories that constitute ≥ 20 % of a species’ diet; Soria
 et al. 2021), habitat breadth (i.e., the number of distinct level 1 IUCN
 habitats suitable for the species; Soria et al. 2021), trophic level and
 activity cycle (Soria et al. 2021). For life history traits, we used the
 mean adult mass (g), mean litter size, and number of litters per year for
 each species, the age at first reproduction, and maximum longevity from
 the COMBINE mammal trait database (Soria et al. 2021). We used mean
 survival estimates from (Cayuela et al. 2024) for species for which
 estimates were available. For species lacking annual survival estimates,
 we averaged mean survival estimates over other members of the genus where
 available. Where genus-level estimates were unavailable, we used estimates
 from the literature. For yes/no variables, 1 = yes, 2 = no. ### Files and
 variables File = Trait_data.xlsx Tab1 = Life history traits Tab2
 =Ecological traits ## Access information Other publicly accessible
 locations of the data: * N/A Data was derived from the following sources:
 * Soria, C. D., M. Pacifici, M. Di Marco, S. M. Stephen, and C. Rondinini.
 2021. COMBINE: a coalesced mammal database of intrinsic and extrinsic
 traits. *Ecology* 102:e03344. * Cayuela, H. et al. 2024. Global patterns
 and drivers of amphibian survival. Nature. *In Review*.