Selection on weapon allometry in the wild

Area of Science:

• Evolutionary biology
• Ecology
• Animal behavior

Background:

• Allometry, the scaling of traits with body size, explains significant morphological variation.
• Factors driving allometric patterns, especially in closely related species, are not fully understood.
• Directional selection on allometry, specifically its slope, is rarely observed in natural populations.

Purpose of the Study:

• Investigate selection on weapon allometry (weapon size vs. body size) in Pachylis neocalifornicus.
• Determine how sexual selection influences the evolution of weapon scaling relationships.
• Test for direct observation of selection on allometric slopes in a wild population.

Main Methods:

• Field study of a wild population of giant mesquite bugs (Pachylis neocalifornicus).
• Analysis of the relationship between male weapon size (enlarged femurs) and body size.
• Observation of mating success in relation to weapon size and body size allometry.

Main Results:

• Large males with proportionally large weapons achieved mating success.
• Small males with proportionally small weapons also achieved mating success.
• These combined mating patterns suggest an increase in the allometric slope of sexually selected weapons.

Conclusions:

• Sexual selection can directly influence the evolution of allometric slopes.
• The observed mating patterns provide evidence for a straightforward mechanism driving allometric evolution.
• This study highlights the role of selection in shaping scaling relationships in natural populations.