DOI: 10.5061/dryad.905qfttx8
title: Rangewide responses to an extreme heat event in <em>Mimulus cardinalis</em>

description: Premise: Extreme events are an understudied aspect of ongoing
 anthropogenic climate change that could play a disproportionate role in
 the threat that rapid environmental shifts pose to natural populations.
 Methods: We exposed plants originating from seeds that were harvested
 before (ancestors) and after (descendants) multiple extreme heat events
 from six populations across the range of Mimulus cardinalis (Phyrmaceae)
 to a short‐term heat‐wave treatment in controlled growth chamber
 environments. We assessed physiological, performance, and functional
 responses (stomatal conductance, leaf temperature deficit, photosystem II
 efficiency, relative growth rate, specific leaf area, and leaf dry matter
 content) to the heat‐wave treatment, along with evolutionary responses
 (differences between ancestors and descendants) of M. cardinalis
 populations to the recent natural extreme heat event. Results: Plants in
 the heat‐wave treatment increased their overall performance, and the
 magnitude of increase was generally greatest among trailing‐edge
 populations. Despite limited overall trait differences between ancestors
 and descendants, there was some evidence of divergent evolutionary
 responses among regions to the natural extreme heat event. However, we did
 not find evidence of adaptive evolution that affected how M. cardinalis
 populations responded to the heat‐wave treatment. Conclusions: These
 results demonstrate that many M. cardinalis populations may reside in
 environments that are below their optimum average temperature, revealing
 potential resiliency to future warming. However, limited evolutionary
 responses in M. cardinalis to the recent extreme heat wave could still
 indicate potential for future vulnerability to extreme climate events of
 increased intensity, frequency, and duration.
description: Readme file associated with the paper Albano et al., American Journal of
 Botany (accepted October 20, 2025, to be published in February, 2026).
 Title: Range-wide responses to an extreme heat event in Mimulus cardinalis
 In this paper, we perform a resurrection experiment, exposing Mimulus
 cardinalis to a heat-wave treatment in growth chamber environments. M.
 cardinalis individuals were sourced from six populations across its range
 (two leading-edge, two range-center, two trailing-edge) and within each
 population, seeds were harvested in 2010 (ancestors) and 2017
 (descendants) which were time periods selected before and after a natural
 multi-year heat-wave event in western North America. This design allows
 for investigation of physiological, performance, and functional trait
 responses to the heat-wave treatment for each population, along with
 investigation of evolutionary responses to the natural heat-wave event
 that could affect how plants respond to the heat-wave treatment. This
 experiment addressed two main objectives: (1) quantify responses in plant
 physiological, performance, and functional traits to a heat-wave treatment
 and determine if those responses varied among populations from across the
 range of M. cardinalis, and (2) characterize differences in response to a
 heat-wave treatment between 2010 ancestors and 2017 descendants,
 indicative of an evolutionary response to the recent heat and drought
 event experienced by natural M. cardinalis populations. The script to
 analyze the data required to address these objectives can be found in
 Albano_et_al_2026_AJB_Script.R, while the data itself can be found in
 Albano_et_al_2026_AJB_Data.csv, which contains the following columns: *
 Cohort: The category of year at which an individual was harvested.
 Ancestor (2010) or Descendant (2017) * Region: The region from which an
 individual was harvested, essentially a combination of two populations
 from each region. N (leading-edge), C (range-center), or S (trailing-edge)
 * Heat: The heat-wave treatment performed on each individual. Control or
 Heat wave * Cross_ID: The cross identifier used to separate individuals
 based on their parentage through the creation of a refresher generation
 prior to the initiation of the experiment * Time1: A unitless scaled
 measure of time of day, constructed by combining individual hour, minute,
 and second variables. * Time2: The Time1 variable converted to a factor
 variable (necessary for autocorrelation models) * Date: The date on which
 physiological traits (gsw, Tdiff, and PhiPS2) were measured for each
 individual. Format: MM/DD/YYYY * Population: The population from which an
 individual was harvested. N1 (leading-edge population #1), N2
 (leading-edge 2), C1 (range-center 1), C2 (range-center 2), S1
 (trailing-edge 1), or S2 (trailing-edge 2) * gsw: Stomatal conductance (of
 water vapor) measurement from one leaf of each individual plant. Units:
 mmol m^-2 s^-1 * gsw_Pred: Predicted stomatal conductance (of water vapor)
 measurement from each control individual if it was to be exposed to the
 heat-wave treatment, based solely on the physical effects of temperature
 increase. Units: mmol m^-2 s^-1 * Tdiff: Leaf temperature at the moment
 gsw was assessed minus air temperature in the growth chamber. Units: °C *
 PhiPS2: Unitless photosystem II efficiency (ΦPSII) for each individual
 plant * leaf_RGR: The relative growth rate of each individual plant, based
 on the number of leaves present prior to and after the experiment. Units:
 leaves leaves^-1 day^-1 * SLA: The specific leaf area of one leaf on each
 individual plant. Units: cm^2 g^-1 * LDMC: The leaf dry matter content of
 one leaf on each individual plant. Units: mg g^-1 *NA values in the
 leaf_RGR, SLA, and LDMC columns represent individuals that were too small
 and/or unhealthy for this data to be collected. \**All heat-wave plants
 ("Heat wave" in the "Heat" column) are recorded as NA
 in the gsw_Pred column because the predicted stomatal conductance increase
 measurement only applies to "Control" plants