Negative density-regulated contest performance promotes conflict resolution in a tree lizard

This project includes the raw data of the research article 'Negative density-regulated contest performance promotes conflict resolution in a tree lizard' by Hsu et al.

Data are in the file negative-density-regulated-contest-performance.ods (a OpenDocument spreadsheet). Download and open it by using spreadsheet software (e.g. Microsoft Office Excel, Libreoffice Calc)

Sheet covariates by population

Column
Description

Site
Lizard population

log.female.over.male.ratio
Natural logarithm of sex ratio (famel over male)

n.injured
Number of injured males

n.not.injured
Number of not injured males

injury.ave
Injury ratio

selectDiff
Standardized selection differential of male snout-vent length

Comp.1
1st principle component of habitat composition

Comp.2
2nd principle component of habitat composition

Comp.3
3rd principle component of habitat composition

Comp.4
4th principle component of habitat composition

invSimpsonTrapAbundance
Food items (inverse Simpson index) in item abundance from pitfall trap

invSimpsonTrapWeight
Food items (inverse Simpson index) in item dry mass from pitfall trap

totalTrapWeight
Total dry mass of food in pitfall trap (g)

invSimpsonStomachAbundance
Dietary breadth (inverse Simpson index) in abundance from stomach items

invSimpsonStomachWeight
Dietary breadth (inverse Simpson index) in dry mass from stomach items

totalStomachWeight
Total dry mass of items in stomach (g)

Sheet covariates by population and sex

Column
Description

Site
Lizard population

Sex
Sex

density
Number of lizard in 1250 m^2

Sheet stage fight

Column
Description

Site
Lizard population

resident (SVL)
Snout-vent length of resident lizard

intruder (SVL)
Snout-vent length of intruder lizard

max.aggresive
Resident highest agressive behavior

is.R.win
Resident as winner

rScore
Rank level of resident highest agressive behavior

Sheet bite force

Column
Description

Site
Lizard population

Sex
Sex

Body weight
Lizard body weight (g)

Head length
Lizard head length (mm)

Head width
Lizard head width (mm)

Head height
Lizard head height (mm)

SVL
Lizard snout-vent length (mm)

Bite Force
Lizard bite force (N)

Abstract

Territoriality is a behavioral adaptation resulting from intraspecific competition and reflects the strategy of how individuals share limited resources in the environment. As a consequence, territorial contests and levels of aggressiveness are strongly influenced by population density.

The positive relationship between population density and the intensity of intraspecific competition may appear straightforward. However, empirical evidence regarding this association remains inconclusive. This ambiguity may be attributed to studies that have predominantly focused on specific fight-associated traits while overlooking the comprehensive assessment of multiple phenotypic characteristics.

To examine the effects of population density and other ecological factors on the variation in fight behavior as well as fight-associated morphology and performance. We conducted population surveys and behavioral experiments using the Swinhoe’s tree lizard across eight populations.

Our findings revealed that males from higher-density populations tended to engage in less intense fights and exhibited a weaker resident advantage in fights, which coincided with our findings on lower rates of injuries, weaker bite forces, and smaller body sizes (and vice versa). Male-specific plasticity in fight behavior, morphology, and performance along a density gradient suggests different evolutionary equilibria in territoriality influenced by local costs and benefits.

Our study supports the significant role of negative density dependence as a fundamental regulator of eco-evolutionary dynamics. The observed phenotypic plasticity emphasizes the importance of ecological and social factors in shaping ontogenetic growth and life-history strategies. Our findings provide a basis for future investigations into pace-of-life syndromes and shed light on how phenotypic adaptation may shape population structure.