DOI: 10.5061/dryad.7sqv9s4q8
title: Data from: Predators drive community reorganization during experimental range shifts

description: 1. Increased global temperatures caused by climate change are causing
 species to shift their ranges and colonize new sites, creating novel
 assemblages that have historically not interacted. Species interactions
 play a central role in the response of ecosystems to climate change, but
 the role of trophic interactions in facilitating or preventing range
 expansions are largely unknown. 2. The goal of our study was to understand
 how predators influence the ability of range-shifting prey to successfully
 establish in newly available habitat following climate warming. We
 hypothesized that fish predation facilitates the establishment of
 colonizing zooplankton populations, because fish preferentially consume
 larger species that would otherwise competitively exclude smaller bodied
 colonists. 3. We conducted a mesocosm experiment with zooplankton
 communities and their fish predators from lakes of the Sierra Nevada
 Mountains in California, USA. We tested the effect of fish predation on
 the establishment and persistence of a zooplankton community when
 introduced in the presence of higher- and lower-elevation communities at
 two experimental temperatures in field mesocosms. 4. We found that
 predators reduce the abundance of larger bodied residents from the alpine
 and facilitate the establishment of new lower-elevation species. In
 addition, fish predation and warming independently reduced the average
 body size of zooplankton by up to 30%. This reduction in body size offset
 the direct effect of warming induced increases in population growth rates,
 leading to no net change in zooplankton biomass or trophic cascade
 strength. 5. We found support for a shift to smaller species with climate
 change through two mechanisms: 1) the direct effects of warming on
 developmental rates and, 2) size-selective predation that altered the
 identity of species’ that could colonize new higher elevation habitat. Our
 results suggest that predators can amplify the rate of range shifts by
 consuming larger bodied residents and facilitating the establishment of
 new species. However, the effects of climate warming were dampened by
 reducing the average body size of community members, leading to no net
 change in ecosystem function, despite higher growth rates. This work
 suggests that trophic interactions play a role in the reorganization of
 regional communities under climate warming.
description: The methods for this experiment are described in the full text
 and supplement of the paper "Predators drive community reorganization
 during experimental range shifts". In short, we collected aquatic
 copepods and cladocerans from three lakes in the Sierra Nevada mountains
 of California in 2016.  At that time we also characterized a subset of
 physical and chemical characteristics of those three focal
 lakes. We used those zooplankton communities in an
 experiment where we added lower elevation communities to higher elevation
 communities in the presence and absence of fish predation. We collected
 zooplankton at the beginning and end of the experiment, preserved them in
 ethanol, then identified and measured individuals using a microscope.
 We also measured chlorophyll a, following the protocol described in the
 main text of the paper.  Details regarding how to
 interpret and use the raw data generated in this experiment are described
 in the "Usage Notes" ReadMe files. 
  
description: The units and description of variables are in the first sheet of
 the excel file, "Metadata". There are 4 data sheets
 total.