Geographic variation of life‐history traits in the sand lizard,Lacerta agilis: testing Darwin's fecundity‐advantage hypothesis

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Abstract
The fecundity‐advantage hypothesis (FAH) explains larger female size relative to male size as a correlated response to fecundity selection. We exploredFAHby investigating geographic variation in female reproductive output and its relation to sexual size dimorphism (SSD) inLacerta agilis, an oviparous lizard occupying a major part of temperate Eurasia. We analysed how sex‐specific body size andSSDare associated with two putative indicators of fecundity selection intensity (clutch size and the slope of the clutch size–female size relationship) and with two climatic variables throughout the species range and across two widespread evolutionary lineages. Variationwithinthe lineages provides no support forFAH. In contrast, the divergencebetweenthe lineages is in line withFAH: the lineage with consistently female‐biasedSSD(L. a. agilis) exhibits higher clutch size and steeper fecundity slope than the lineage with an inconsistent and variableSSD(L. a. exigua).L. a. agilisshows lower offspring size (egg mass, hatchling mass) and higher clutch mass relative to female mass thanL. a. exigua, that is both possible ways to enhance offspring number are exerted. As theSSDdifference is due tomalesize (smaller males inL. a. agilis), fecundity selection favouring larger females, together with viability selection for smaller size in both sexes, would explain the female‐biasedSSDand reproductive characteristics ofL. a. agilis. The pattern of intraspecific life‐history divergence inL. agilisis strikingly similar to that between oviparous and viviparous populations of a related speciesZootoca vivipara. Evolutionary implications of this parallelism are discussed.
Funding Information
  • Deutsche Forschungsgemeinschaft (RO 4168/1-1)

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