DOI: 10.5061/dryad.1h2h6
title: Data from: Isotopic niche variation from the Holocene to today reveals minimal partitioning and individualistic dynamics among four sympatric desert mice

description: 1.Species interact with each other and their environment over a range of
 temporal scales, yet our understanding of resource partitioning and the
 mechanisms of species coexistence is largely restricted to modern
 time-scales of years to decades. Furthermore, the relative magnitudes of
 inter- versus intraspecific variation in resource use are rarely
 considered, despite the potential for the latter to influence a species’
 ability to cope with changing environmental conditions. 2.Modern desert
 rodent communities are thought to be strongly structured by competitive
 interactions, with niche partitioning of food resources hypothesized to
 explain the coexistence of multiple sympatric granivores. Yet the
 stability of niche dynamics over extended temporal scales within desert
 rodent communities is unknown. 3.I examined the isotopic niche dynamics of
 four common sympatric desert mice (three granivores: Chaetodipus formosus,
 Perognathus longimembris, and Reithrodontomys megalotis, and one omnivore:
 Peromyscus maniculatus) in the Smoke Creek Desert of northwestern Nevada
 using 13C and 15N isotopes obtained from “Modern” (2008-2013 CE),
 “Historical” (1989-2005 CE), and Holocene fossil specimens spanning the
 last ca. 7,500 years. 4.I found significant variation in niche position,
 niche breadth, and interspecific niche overlap of these species through
 time. The niche breadth dynamics of the cricetids (P. maniculatus and R.
 megalotis) were positively correlated with one another, while the niche
 breadth dynamics of the heteromyid C. formosus were negatively correlated
 with those of all other species. Body size, dietary functional group,
 paleoenvironmental trends, and time-averaging provided little explanatory
 power. Importantly, Modern and Historical patterns of resource use and
 partitioning differed from Holocene baselines in terms of decreased niche
 overlap and in the absolute and relative position of each species’ niche
 in at least one isotopic axis. 5.These observations suggest that each
 species’ resource use changed individualistically over the Holocene, hence
 niche dynamics are poorly explained by the hypothesis of temporally-stable
 species interactions at millennial time-scales. Furthermore, changes to
 the resource base over the last century (likely due to the spread of
 invasive cheatgrass) may be increasing resource partitioning in the
 Modern, pushing species past their baseline ranges of resource use
 variation.
description: Stable isotope values
 through time for four Great Basin desert miceStable isotope data from
 mouse bone collagen, arrayed by stratum at Two Ledges Chamber, NV. Stratum
 age represents years BP unless otherwise noted. AMS 14C dates from bone
 collagen were calibrated using OxCal 4.1 and the IntCal 09 calibration
 curve. Age estimates represent the highest probability peak obtained from
 the Bayesian posterior probability distribution associated with date
 calibration. Age type refers to the following: (a) known collection year,
 (b) known by AMS 14C dates, (c) inferred from a combination of AMS 14C
 dates and spline function estimate, (d) undated stratum age inferred from
 a spline function. δ13C_2013 indicates carbon data Seuss-corrected to 2013
 CE.Table.xlsx