Metabolic rate associates with, but does not generate covariation between, behaviours in western stutter-trilling crickets,Gryllus integer.
The causes and consequences of among-individual variation and covariation in behaviours are of substantial interest to behavioural ecology, but the proximate mechanisms underpinning this (co)variation are still unclear. Previous research suggests metabolic rate as a potential proximate mechanism to explain behavioural covariation. We measured the resting metabolic rate (RMR), boldness and exploration in western stutter-trilling crickets,Gryllus integer, selected differentially for short and fast development over two generations. After applying mixed-effects models to reveal the sign of the covariation, we applied structural equation models to an individual-level covariance matrix to examine whether the RMR generates covariation between the measured behaviours. All traits showed among-individual variation and covariation: RMR and boldness were positively correlated, RMR and exploration were negatively correlated, and boldness and exploration were negatively correlated. However, the RMR was not a causal factor generating covariation between boldness and exploration. Instead, the covariation between all three traits was explained by another, unmeasured mechanism. The selection lines differed from each other in all measured traits and significantly affected the covariance matrix structure between the traits, suggesting that there is a genetic component in the trait integration. Our results emphasize that interpretations made solely from the correlation matrix might be misleading.
Institute of Ecology and Earth Sciences, University of Tartu, Tartu 51014, Estonia indrikis.krams@ut.ee.|Department of Psychology, University of Tennessee, Knoxville, TN 37996-0900, USA.
Indrikis A
http://orcid.org/0000-0001-7150-4108
IA
Krams
Behavioural Ecology, Department of Biology II, Ludwig-Maximilians University of Munich, Germany.
Petri T
http://orcid.org/0000-0001-8915-6295
PT
Niemelä
Department of Biotechnology, Institute of Life Sciences and Technology, Daugavpils University, Daugavpils LV5401, Latvia.|Centre for Ecology and Environmental Research, Vilnius University, Vilnius LT10257, Lithuania.
Giedrius
G
Trakimas
Department of Biotechnology, Institute of Life Sciences and Technology, Daugavpils University, Daugavpils LV5401, Latvia.
Ronalds
R
Krams
Department of Psychology, University of Tennessee, Knoxville, TN 37996-0900, USA.|Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN 37996-0900, USA.
Gordon M
GM
Burghardt
Department of Plant Protection, Institute of Agricultural and Environmental Sciences, Estonian University of Life Science, Tartu 51014, Estonia.
Tatjana
T
Krama
Department of Plant Protection, Institute of Agricultural and Environmental Sciences, Estonian University of Life Science, Tartu 51014, Estonia.
Aare
A
Kuusik
Department of Plant Protection, Institute of Agricultural and Environmental Sciences, Estonian University of Life Science, Tartu 51014, Estonia.
Marika
M
Mänd
Department of Biology & Turku Brain and Mind Centre, University of Turku, Turku, Finland.
Markus J
MJ
Rantala
Institute of Ecology and Earth Sciences, University of Tartu, Tartu 51014, Estonia.
Raivo
R
Mänd
Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu 80101, Finland.
Jukka
http://orcid.org/0000-0001-6303-6797
J
Kekäläinen
Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu 80101, Finland.
Ilkka
I
Sirkka
English, Drama and Writing Studies, and School of Psychology, University of Auckland, Auckland 1010, New Zealand.
Severi
S
Luoto
Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu 80101, Finland.
Raine
R
Kortet
D000818:Animals; D001481:Basal Metabolism; D001522:Behavior, Animal; D006135:Gryllidae / Q000378:metabolism*; D010641:Phenotype
animal personality; behavioural syndrome; behavioural variation; boldness; exploration; resting metabolic rate