Life history evolution of the lizard Sceloporus scalaris: comparisons of lowland and montane populations

dc.contributor.authorMathies, Thomas C.en
dc.contributor.departmentBiologyen
dc.date.accessioned2014-03-14T21:40:41Zen
dc.date.adate2009-07-21en
dc.date.available2014-03-14T21:40:41Zen
dc.date.issued1994en
dc.date.rdate2009-07-21en
dc.date.sdate2009-07-21en
dc.description.abstractWithin the Sceloporus scalaris species group, some species are oviparous while others are viviparous, suggesting the origin of viviparity is relatively recent. This interpopulation comparison focused on Sceloporus scalaris in Arizona because low elevation (1500 m) and high elevation (2500-2900 m) populations exhibit short and long periods of egg retention, respectively, and increased periods of egg retention are presumably an intermediate step in the evolution of viviparity. Low elevation populations had life histories typical of lowland Sceloporus: eggs are laid at embryonic stages 32-33, clutch sizes are relatively large, hatchlings are relatively small, and more than one clutch is produced per season. In contrast, montane populations retain eggs to embryonic stages 36-38, clutch sizes are relatively small, hatchlings are relatively large, and only one clutch is produced per season. In accord with their lengthy retention, eggshells of montane populations were thinner than those of lowland populations. The assumption that prolonged egg retention is mechanistically associated with relatively thin eggshells was tested by comparing the development of embryos in eggs retained in utero with that of control embryos in eggs incubated in Simulated nests where water and gases were presumably not limited. For the low elevation population, growth rates of embryos retained in utero as long as stage 39 were identical to those of control eggs at the same stages. However, water uptake by retained eggs was confined to the embryo whereas water uptake of control eggs was associated with both the embryo and extraembryonic tissues. These results suggest that the length of egg retention by S. scalaris is not constrained by eggshell thickness, and that the capacity to regulate the water balance of eggs may be an important component of the evolution of viviparity.en
dc.description.degreeMaster of Scienceen
dc.format.extentv, 80 leavesen
dc.format.mediumBTDen
dc.format.mimetypeapplication/pdfen
dc.identifier.otheretd-07212009-040400en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-07212009-040400/en
dc.identifier.urihttp://hdl.handle.net/10919/43789en
dc.language.isoenen
dc.publisherVirginia Techen
dc.relation.haspartLD5655.V855_1994.M347.pdfen
dc.relation.isformatofOCLC# 30932955en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subject.lccLD5655.V855 1994.M347en
dc.subject.lcshBunch grass lizard -- Evolutionen
dc.subject.lcshBunch grass lizard -- Reproductionen
dc.subject.lcshViviparityen
dc.titleLife history evolution of the lizard Sceloporus scalaris: comparisons of lowland and montane populationsen
dc.typeThesisen
dc.type.dcmitypeTexten
thesis.degree.disciplineBiologyen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen
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