Reproductive Burden, Locomotor Performance, and the Cost of Reproduction in Free Ranging Lizards

Abstract

A reduction in the locomotor capacity of gravid females is considered to be a cost of reproduction if it leads to an increased risk of mortality. In this study, we measured the change in endurance between gravid and postgravid female side-blotched lizards (Uta stansburiana) as a test of the cost of reproduction. We also altered reproductive investment in some females by direct ovarian manipulation (yolkectomy), which decreased reproductive burden by 30%. Regardless of experimental treatment, all females had lower endurance when gravid. Endurance was 28% lower in gravid females from the yolkectomy treatment and 31% lower in the unmanipulated females relative to postoviposition females. The experimental reduction in clutch mass resulted in a 21% increase in endurance of gravid yolkectomy females relative to control females. Postovipositional endurance was significantly higher in the yolkectomized females than unmanipulated females, which suggests that the cost of reproduction carries over to postoviposition performance. Unmanipulated females exhibited a significant negative association between endurance and size-specific burden. Endurance was not correlated with clutch size or size-specific burden in the yolkectomy females. Survivorship to the second clutch was higher in the yolkectomy females. The results from a logistic regression showed the probability of survival to the second clutch was significantly and positively associated with endurance after controlling for the effects of treatment. Our analyses demonstrated that the decrement in performance associated with current reproductive investment represents a cost of reproduction expressed as diminished locomotor performance and lowered survivorship to the next clutch.

Maturational costs of reproduction due to clutch size and ontogenetic conflict as revealed in the invisible fraction

“…Natural history observations suggest that changes in pattern of selection across 1991-1993 were driven by a fivefold increase in predatory coachwhip snakes, Masticophis flagellum (Sinervo & DeNardo 1996). Large clutches in lizards increase pre-laying reproductive burden of the clutch mass in females, decrease sprint speed in lizards, which we have linked directly to the increases in mortality risk (Miles et al 2000). It would not be surprising that such effects may operate on survival during maturation.…”

Phylogenetic Comparative Analysis of Life-History Variation Among Populations of the Lizard Sceloporus Undulatus:an Example and Prognosis

“…For example, in the case of intraindividual trade-offs, it is commonly expected that allocating energy to offspring in a single reproductive episode will lead to a negative relationship between the number and size of offspring (e.g., Sinervo 1999;Ernsting and Isaaks 2000;Jordan and Snell 2002), which can be detected through experimental manipulation of offspring size or number (e.g., Sinervo 1999;Oksanen et al 2001;Williams 2001). Similarly, the allocation of energy to reproduction may result in a decrease in energy available for maintenance, activity, and growth, which could lead to reduced survival to the next reproductive episode (reviewed by Reznick 1985;Schwarzkopf 1993;Landwer 1994;Miles et al 2000). Consequently, a negative relationship between the magnitude of reproduction (as estimated by clutch size, clutch frequency, or reproductive effort) and survivorship is expected.…”

Impaired escape flight ability in butterflies due to low flight muscle ratio prior to hibernation

“…For example, weight gain due to lipid accumulation or pregnancy may decrease escape speeds, increasing the risk of being caught by predators. Reduced escape ability due to pregnancy has been shown in a variety of animal groups such as reptiles (Seigel et al, 1987;Miles et al, 2000), birds (Lee et al, 1996;Kullberg et al, 2002a), fish (James and Johnston, 1998) and scorpions (Shaffer and Formanowicz, 1996). Further, migratory birds loaded with fuel (Kullberg et al, 1996;Kullberg et al, 2000), birds that increase body mass during incubation (Kullberg et al, 2002b) and moulting birds with reduced wing areas (Swaddle and Witter, 1997;Swaddle et al, 1999) show similar limitations in escape performance.…”