DOI: 10.5061/dryad.9kd51c5hb
title: Positive genetic covariance and limited thermal tolerance constrain tropical insect responses to global warming

description: Tropical ectotherms are particularly vulnerable to global warming because
 their physiologies are assumed to be adapted to narrow temperature ranges.
 This study explores three mechanisms potentially constraining thermal
 adaptation to global warming in tropical insects: 1. tradeoffs in
 genotypic performance at different temperatures (the jack-of-all-trades
 hypothesis) 2. positive genetic covariance in performance, with some
 genotypes performing better than others at viable temperatures (the
 ‘winner and ‘loser genotypes hypothesis) or 3. limited genetic variation
 as the potential result of relaxed selection and the loss of genes
 associated with responses to extreme temperatures (the gene decay
 hypothesis). We estimated changes in growth and survival rates at multiple
 temperatures for three tropical rain forest insect herbivores
 (Cephaloleia rolled-leaf beetles, Chrysomelidae). We reared 2746
 individuals in a full-sibling experimental design, at temperatures known
 to be experienced by this genus of beetles in nature (i.e., 10-35°C).
 Significant genetic covariance was positive for 16 traits, supporting the
 ‘winner and ‘loser genotypes hypothesis. Only two traits displayed
 negative cross-temperature performance correlations. We detected a
 substantial contribution of genetic variance in traits associated with
 size and mass (0-44%), but low heritability in plastic traits such as
 development time (0-6%) or survival (0-4%). Lowland insect populations
 will most likely decline if current temperatures increase beyond 2°C. It
 is concerning that local adaption is already lagging behind current
 temperatures. The consequences of maintaining the current global warming
 trajectory would be devastating for tropical insects. However, if humans
 can limit or slow warming, many tropical ectotherms might persist in their
 current locations, and potentially adapt to warmer temperatures.
description: Description of methods used for collection/generation of
 data:<br> See manuscript for details: DOI:
 10.1111/jeb.13905  <br> Methods for processing
 the data: <br> -The data in columns 3-26
 (Consecutivo-Fecha_medicion) were recorded in lab notebooks and
 entered <br> into Excel spreadsheets, when columns 2 and 27 (sheet
 and Comentarios.revisar.datos.Abril.2017) were added.<br> -Data
 accuracy was checked again by Christina S. Baer and column 39 (Checked_CB)
 was added.<br> -The complete dataset for 12 Cephaloleia populations
 was combined and processed in R.<br> -hatch, pupate, and emerge were
 coded based on whether there was a value in Fecha_eclosion,<br>
 Fecha_pupado, or Fecha_nace_adulto, respectively.<br> -dev_time was
 calculated for individuals who reached adulthood by subtracting
 Fecha_eclosion fro<br> Fecha_nace_adulto.<br> -Asurv_time was
 calculated for individuals who reached adulthood by subtracting
 Fecha_nace_adulto<br> from Fecha_muerte_adulto.<br>
 -hatch_yrwk, death_yearwk, and emerge_yrwk were calculated to represent
 Fecha_eclosion, the death date (one of <br> Fecha_muerte_larva,
 Fecha_muerte_pupa, or Fecha_muerte_adulto), and Fecha_nace_adulto
 (if <br> applicable) as the year and calendar week number as defined
 by ISO 8601. The calendar weeks <br> begin on Monday. If the week
 containing January 1 has &gt;=4 days in the new year, it is week
 1<br> of the new year; otherwise it is the last week of the previous
 year.<br> -ldays was calculated by subtracting the start of the life
 stage (Fecha_eclosion) from the <br> either the transition date to
 the next life stage (Fecha_pupado) or the death date within the <br>
 stage (Fecha_muerte_larva)<br> -pdays was calculated by subtracting
 the start of the life stage (Fecha_pupado) from the either <br> the
 transition date to the next life stage (Fecha_nace_adulto) or the death
 date within the stage <br> (Fecha_muerte_pupa)<br> -adays was
 calculated by subtracting the start of the life stage (Fecha_nace_adulto)
 from the <br> death date within the stage
 (Fecha_muerte_adulto) -Data for eggs that did not hatch
 were removed from the raw dataset.<br> -A dataframe for each species
 was saved as a .csv spreadsheet