Climate change is predicted to intensify the impacts of invasive species by enhancing their performance relative to their native counterparts. However, few studies have compared the performance of invasive predators and native prey, despite the fact that non-native predators are well known to disrupt native communities.
The ‘trophic sensitivity hypothesis’ suggests that predators are less tolerant of increasing environmental stress than their prey, whereas the ‘tolerant invaders hypothesis’ suggests that invaders are more tolerant than native species due to selection during the introduction process. It is therefore unclear how invasive predators will respond to increasing climate stressors.
We coupled physiological measurements (thermal tolerance, thermal optima, salinity tolerance, predation rate) with environmental time-series data to assess the effects of warming and extreme low salinity events on non-native predators (gastropods) and native prey (oysters) from a coastal ecosystem.
In general support of the trophic sensitivity hypothesis, we found that both non-native predators exhibited lower thermal optima relative to native prey, lower salinity tolerance and one predator was less tolerant of warming. However, because warming tolerance was extremely high (i.e. habitat temperature is 7·9–21 °C below thermal tolerance), near-term warming may first increase predator performance (consumption and growth rates), with negative effects on prey. Low salinity will likely produce heterogeneous effects on predator–prey interactions due to varying watershed sizes among estuaries that control the duration of low salinity events.
The trophic sensitivity hypothesis may be a useful framework for understanding community responses to extreme climate change, which portends a decoupling of predator–prey interactions. However, we conclude that this hypothesis must be evaluated in environmental context and that coupling physiological metrics with in situ environmental data offers the best predictive power of near-term climate change impacts on invaded communities. Within our study system, warming is likely to intensify the impacts of both invasive predators, which may greatly reduce the abundance of the native oyster, a species of conservation and restoration focus.
Thermal tolerance data
Thermal tolerance data from the heat bar experiment. Each row is an individual animal and each column describes the conditions and response for that animal. "tube" refers to the tube number for the heat bar. "row" refers to the row within the heat bar. "Species" refers to Oyster (Ostrea lurida), Atlantic drill (Urosalpinx cinerea), and Japanese drill (Ocenebra inornata). "temp" refers to the temperature during the last hour of exposure in degrees Celsius. "alive" refers to whether or not the animal was alive the following day after heat exposure (Y = yes, N = no). "survival" is a binary coding for the alive response (1 = yes, 0 = no). "size" is the shell height of the animal in millimeters."time" refers to the temporal block during which the experiment was conducted (1,2, or 3).
Cheng et al Thermal Tolerance Data.csv
Salinity Tolerance Data - Gastropods
Salinity tolerance data for oyster drills (gastropods). Each row is an individual animal and each column is a variable. "species" refers to Urosalpinx (Atlantic oyster drill) and Ocenebra (Japanese oyster drill). "salinity" is the exposure salinity in practical salinity units. "duration" is the length of exposure in days. "size" is the shell height in millimeters. "alive" is whether or not the animal survived the salinity exposure. "survival" is a numerical code for "alive" where 1 = alive and 0 = death.
Cheng et al Salinity Tolerance Data.csv
Salinity Tolerance Data - Oysters
Salinity tolerance data for Olympia oysters (Ostrea lurida). Each row is an individual animal and each column is a variable. "species" refers to oysters (invariant). "Salinity" is the exposure salinity in practical salinity units. "size" is the shell height in millimeters. "alive" is whether the animal survived the salinity exposure (yes or no). "Survival" is a numerical code for the "alive" variable (1 = alive, 0 = dead). "Duration" is the number of days that the animal was exposed to the target salinity.
Cheng et al Salinity Tolerance Data Oysters.csv
Thermal Growth High Ration Data - Oysters
Oyster growth data for thermal performance curve. Each row is an individual oyster and each column is a variable. "tile" refers to a numbered value assigned to each pvc square that oysters were settled upon. "tile.side" is the side upon which the oyster was located (a or b). "oyster.no" is a unique number assigned to every oyster. "tank" is the number assigned to each 38 liter tank during the experiment. "temp" is the temperature in degrees Celsius. "initial.area" is the shell area centimeters squared for that oyster at the beginning of the experiment. "area" is the final area in centimeters squared after the temperature exposure.
Cheng et al Oyster Growth High Ration.csv
Thermal Growth Low Ration Data - Oysters
Growth data for low ration oyster experiment. Each row is an individual animal and each column is a variable. "food.ration" is low (invariant). "tile" refers to the pvc plate that each oyster is assigned to. "initial.area" is the size in centimeters squared for the oyster at the beginning of the experiment. "final.area" is the oyster size in centimeters squared at the end of the experiment. "group" is a numerical code for the temperature treatment. "temp" is the temperature that the oysters were assigned to in degrees Celsius. "growth" is the difference between the final and initial size in centimeters squared. "cum.growth" is the cumulative growth for each tile in centimeters squared.
Cheng et al Oyster Growth Low Ration.csv
Thermal Growth High Ration Data - Gastropods
Thermal growth data for the gastropods under high ration availability. Each row is an individual animal and each column is a variable. "species" is either Atlantic drill (Urosalpinx cinerea) or Japanese drill (Ocenebra inornata). "snail.no" is a unique number given to every experimental snail. "teaball" is a number given to each housing. "temperature" is the water temperature that each snail was exposed to in degrees Celsius. "tank" is the tank number that each teaball was housed in. "alive" is a numerical code for whether or not the snail survived the experiment (1 = alive, 0 = dead). "initial.sh" is the shell height of each snail at the beginning of the experiment in millimeters. "final.sh" is the shell heigh of each snail at the end of the experiment in millimeters. "final.sh.width" is the shell width (at widest point) at the end of the experiment. "notes" are given for a subset of snails.
Cheng et al Gastropod Growth High Ration.csv
Environmental Data Tomales - Middle Bay
Physical environmental data from "Middle Bay" site within Tomales Bay, CA. Data was collected with a YSI 6920V2 sonde deployed at latitude 38.150328 degrees and longitude -122.905767 degrees. Data collection began on November 24, 2010 and ended on January 16, 2014. Each row is an observation and each column is a variable. "date" is the date in month/day/year format. "time" is the local time in hour:minute:second format. "DateTimeStamp" is a concatenated string of "date" and "time". "temp" is the water temperature in degrees Celsius. "spcond" is the specific conductivity in millisiemens per centimeter. "salinity" is the calculated salinity from specific conductivity in practical salinity units. "pH" is the water column pH in total scale. "do.sat" is the dissolved oxygen in percent saturation. "do.mgl" is the dissolved oxygen in milligrams per liter.
Cheng et al Environmental Data.csv
Environmental Data Tomales - Inner Bay
Environmental data from Tomales Bay, CA. Temperature data collected with an iButton data logger (DS-1922L). Logger was deployed at 0.0 meters above mean lower low water level at latitude 38.115117 degrees and longtitude -122.870695 degrees. "date.time" is the date and time in month/dat/year hour:minute format. "oday" is the ordinal day. "tide.time" is the time of sea level measurements. "aerial.exposure" is whether the sensor is estimated to be in air or water given the tide. "water.temp" is the temperature of the water in degrees Celsius. "air.temp" is the temperature of the air in degrees Celsius.
Cheng et al Environmental Data Inner Bay.csv