Female-specific ornamentation predicts offspring quality in striped plateau lizards, Sceloporus virgatus

Stacey Weiss, Department of Biology, University of Puget Sound, 1500 North Warner Street #1088, Tacoma, WA 98416-1088, USA
Eileen A. Kennedy, Department of Biology, University of Puget Sound, 1500 North Warner Street #1088, Tacoma, WA 98416-1088, USA
James A. Bernhard, Department of Mathematics and Computer Science, University of Puget Sound, 1500 North Warner Street #1043, Tacoma, WA 98416-1043, USA

Abstract

When females vary in reproductive quality, they may be selected to honestly signal that quality and males may be selected to express mate choice based on this variation. In the striped plateau lizard, females with larger and more saturated orange throat patches are of higher phenotypic quality, and males preferentially associate with brighter females. Here, we assess whether this female ornament conveys fitness benefits by relating female ornamentation to offspring quality. We housed groups of male and female Sceloporus virgatus in outdoor enclosures, tracked the seasonal color development of females to determine peak ornament expression, measured offspring body condition from hatching to day 180, and measured offspring sprint speed at day 180. Although we did not eliminate the possibility of assortative mating within enclosures, we controlled for these potential effects by exposing females to small groups of similarly sized males and by including maternal body size, maternal body condition, and egg mass as covariates in our statistical models. Offspring body condition was reliably predicted by female ornament size but not by ornament color intensity or saturation. Similarly, offspring sprint speed was predicted only by ornament size and not by color intensity or saturation. Females with large ornaments tended to produce offspring with higher body condition and faster offspring than did females with small ornaments. These results are consistent with the hypothesis that males may gain fitness benefits from preferentially allocating their reproductive effort toward females with larger orange patches by producing higher quality offspring. Possible mechanisms underlying such female-ornament–offspring-quality relationships are discussed.