DOI: 10.5061/dryad.qv9s4mwsd
title: Thermal history mediates the ecological role of body size in a freshwater fish

description: Intraspecific trait variation among populations may
 strongly alter community and ecosystem structure and function.
 Body size is a fundamental trait of all organisms, affecting both
 organismal physiology and ecological effects, which may differ across
 populations. For example, body size is predicted to decline with warming.
 As such, in this study, we aim to determine how population differences in
 thermal history mediate the ecological role of body size in a freshwater
 fish. We conducted a mesocosm experiment in which we manipulated fish
 (Gambusia affinis [Baird and Girard, 1853]) source populations (ambient
 source vs warm source) and body size while holding their biomass constant.
 We monitored community and ecosystem response variables including,
 macroinvertebrate abundance, zooplankton biomass, phytoplankton abundance,
 and greenhouse gas flux. Changes in fish body size influenced most
 ecological responses, but these effects often depended on the thermal
 history of the fish population. For many responses, the effects of reduced
 fish body size were offset by a history of exposure to warm temperatures,
 suggesting that environmental factors (including thermal acclimation) and
 adaptation may offset the community and ecosystem effects of decreased
 consumer body size. Our research suggests that ecological changes will
 depend on changes in body size and environmental factors, as well
 as on other trait changes associated with warming. Experiments
 and models addressing the ecological effects of body-size decline alone
 may overestimate the ecological changes expected under warming.
description: # Thermal history mediates the ecological role of body size in a
 freshwater fish Dataset DOI:
 [10.5061/dryad.qv9s4mwsd](10.5061/dryad.qv9s4mwsd) ## Description of the
 data and file structure Mescosm (experimental pond) data were collected
 over 6 time points (The first was before adding fish (T0) and then
 measurements were taken at 4 (T1), 8 (T2), 16 (T3), 24 (T4), and 32 (T5)
 days after adding fish. Experimental ponds contained small or large-sized
 fish from ambient or warm source populations. There are also control
 tanks. In total, there are 5 experimental treatments (Control, Small-warm,
 Small-cool, Large-ambient, Large-ambient). ### Files and variables ####
 File: Meso_body_size.csv **Description:** Treatment description and data
 from the variables measured throughout the mesocosm experiment. Units for
 variables measured are described below. Where data were not collected for
 a response variable in a given week or for a treatment, cells are filled
 with n/a. ##### Variables * Pop: Source population (warm or ambient) *
 Size: Body size (small or large) * Mesocosm: Mesocosm number * Row: Row in
 which the mesocosm was in * Treatment: Treatment description (Population,
 Size). PP refers to Waikato River Spring at Prawn Park  which is the
 ambient site and AA refers to Akatarewa Hot Spring the warm site. * Week:
 Sampling week * Day: Sampling day * Chla: chlorophyll-a abundance (µg/L) *
 Periphyton: Periphyton (mg/m2) * Bugs_pred: Macroinvertebrates predatory
 (count) * Bugs_nonpred: Macroinvertebrates nonpredatory (count) *
 N2O_am: Nitrous oxide, measured during the day (mg m2  min1) *
 CO2_am: Carbon dioxide, measured during the day (mg m2  min1) *
 CH4_am: Methane, measured during the day (mg m2  min1) * NH3_am: Ammonia,
 measured during the day (mg m2  min1) * N2O_pm: Nitrous oxide, measured at
 night (mg m2  min1) * CO2_pm: Carbon dioxide, measured at night (mg m2 
 min1) * CH4_pm: Methane, measured at night (mg m2  min1) *
 NH3_pm: Ammonia, measured at night (mg m2  min1) * ER: Ecosystem
 respiration (DO mg/L) * NPP: Net Primary Production (DO mg/L) * GPP: Gross
 Primary Producion (DO mg/L) * NH4: Ammonia (NH4+ µg/L) * pH: pH *
 SPC: Temperature compensated (25°C) specific conductivity (mS/m) *
 Zoop_bm: Zooplankton biomass (µg/L) * Fish_biomass_g: Fish biomass (g) ##
 Code/software Data are stored in a .csv file and may be opened by any
 software. Analysis for the manuscript was carried out in R (R statistical
 software version 3.3.3; R Project for Statistical Computing, Vienna,
 Austria).