Female Reproductive Investment in the Mesquite Lizard (Sceloporus grammicus) Species Complex (Squamata: Phrynosomatidae)

• Published in: The Southwestern naturalist 2013-09, Vol.58 (3), p.335-343
• Main Authors: Bastiaans, Elizabeth, de la Cruz, Fausto Méndez, Hernández, Karla Rodríguez, Aguirre, Cynthia Flores, Sinervo, Barry
• Format: Article
• Language: English
• Subjects: Animal behavior; Average linear density; body size; chaparral; climate change; Ecological genetics; Ecological life histories; ecosystems; energy; environmental factors; Evolution; Feature s; Female animals; Females; forests; habitats; Lacertilia; life history; Litter size; Lizards; Mating behavior; neonates; phenotypic correlation; Population; Population size; pregnancy; progeny; Prosopis; Reproduction; resource allocation; Sceloporus; Sceloporus grammicus; Sea level; Squamata; Studies
• ISSN: 0038-4909; 1943-6262
• DOI: 10.1894/0038-4909-58.3.335

Life-history theory is based on the idea that trade-offs exist in allocation of resources. The same energy cannot simultaneously fuel growth and reproduction or simultaneously increase size and number of offspring. Many genetic, physiological, and environmental variables influence how trade-offs manifest and whether they are detectable through phenotypic correlations. In most squamates, the absence of parental care enables estimation of reproductive investment using mass of offspring. This, as well as their diverse ecologies, makes squamates an attractive system for empirical tests of life history theory. Approximately 20% of squamates are viviparous, and long gestation periods limit most to one litter per year. Carrying offspring until an advanced developmental stage may increase the burden of the litter, and female abdominal volume may constrain litter size. These factors should intensify selection on female tactics of life history and enhance detectability of trade-offs. We compare life history of females in two species within the Sceloporus grammicus species complex, viviparous Mexican lizards from varied habitats. Each inhabits one of the primary ecosystems used by this taxon (chaparral and forest). Litter sizes were lower in the chaparral population, when adjusted for body size of the mother. A trade-off of size versus number of offspring was detected in the forest population but not in the chaparral population. The chaparral population varied more in average neonate mass between years, which may relate to local extinctions, likely linked to climate change, in Mexican montane lizards. Regardless of whether these differences represent adaptation or plasticity, our findings emphasize the importance of environmental influence on trade-offs in life history. La hipótesis de que existen compromisos en la asignación de recursos es la base de muchas teorías de historia de vida. La misma energía no puede apoyar simultáneamente el crecimiento somático y la reproducción, ni simultáneamente aumentar el número de crías y el tamaño de éstas. Muchas variables genéticas, fisiológicas y ambientales influyen en cómo se manifiestan los compromisos y si ésos son detectados por correlaciones fenotípicas. En la mayoría de las lagartijas, la ausencia del cuidado parental significa que la inversión reproductiva se puede estimar por la masa de los neonatos. Esto, junto con sus diversas ecologías, las hacen ideales para pruebas empíricas de la teoría de historia de vida. Apro