Climatic variability promotes asymmetric competition and exclusion in ectotherms

Shih-fan Chan

Climate change is known to modify both climatic mean and variability. Environmental
variability  has  long  been  considered  an  important  regulator  of  species  interactions,
particularly  interspecific  competition.  However,  although  increasing  studies  have
focused  on  the  biological  impacts  of  changing  climatic  mean  and  variability,  their
interacting  effects  on  species  interaction,  and  hence  species’  distribution,  were  less
explored.  Here,  we  investigate  how  changing  thermal  variation  and  mean  influence
the  competition  and  coexistence  between  burying  beetles,  Nicrophorus  nepalensis,
and  blowflies  along  a  large  elevational  gradient  in  central  Tai wan.   Our  field  study
shows that  habitat alteration increased daily temperature range (DTR)—a short‐term
thermal  variation—and  the  effect  was  more  pronounced  in  higher  elevation.  This
higher  DTR  negatively  impacted  the  breeding  success  of  N.  nepalensis  through
altering  the  competitive  interaction  between  N.  nepalensis  and  blowflies,  which,  in
turn, promoted the competitive exclusion of N. nepalensis. We further integrated the
thermal  performance  curve  and  Lotka‐Volterra  model  to  explore  the  general
relationship  between  climatic  mean  and  variability  on  the  competitive  relationship
between  species.  Results  from  the  model  showed  that  temperature  variability  can
cause both  coexistence and competitive exclusion depending on its interacting effect
with mean temperature. Our lab experiment on the competitive interaction between
N. nepalensis and blowflies further supported these model predictions. Together, our
study  provides  a  general  theoretical  framework  predicting  how  competitive
interaction  changes  with  temperature  mean  and  variability,  which  could  be
particularly  useful  for  predicting  the  changes  of  biotic  interactions  under  climate
change.

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