Factors affecting clutch size in the teiid lizards Cnemidophorus tigris gracilis and C. t. septentrionalis

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Samples covered latitudinal and elevational gradients of 8.3° and 1669m, and were used to examine the relationship of clutch size with body size of reproductive females and elevation, latitude, and mean annual precipitation of collecting sites from SW Arizona to NW Colorado. Body size and elevation had significant linear relationships with clutch size. Reproductive females of C.t.septentrionalis have larger bodies and produce larger clutches, on average, than reproductive females of C.t.gracilis. The difference in clutch size remained significant when body size was held constant in an analysis of covariance, but became nonsignificant with elevation as the covariate. In general, C.t.gracilis occupies lower elevational habitats, while the range of C.t.septentrionalis includes higher elevations. C.t.septentrionalis has apparently retained potential to produce multiple clutches. Production of one relatively large clutch per season in C.t.septentrionalis rather than several smaller clutches (sensu C.t.gracilis) represents a phenotypically plastic response to elevation (climatic regimen) rather than being genetically fixed. -from Authors

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