Robert F. Inger

Bio: Robert F. Inger is an academic researcher. The author has contributed to research in topics: Agama agama. The author has an hindex of 1, co-authored 1 publications receiving 119 citations.

The Life of the Rainbow Lizard

Abstract: The life of the rainbow lizard , The life of the rainbow lizard , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

The physiological ecology of reptilian eggs and embryos. and the evolution of viviparity within the class reptilia

Abstract: SUMMARY 1. Eggs of Crocodilia and Chelonia, like those of birds, have a pair of egg membranes separating a thick layer of albumen from the calcareous shell. In contrast, eggs of oviparous Lepidosauria have only a single shell membrane, upon which relatively small amounts of calcium carbonate are deposited; and the volume of albumen in eggs is extraordinarily small at the time of oviposition. 2. With the possible exception of certain geckos and some chelonians, eggs of oviparous reptiles seem always to absorb water from the substrate during the course of normal incubation. In so far as the rate of water absorption exceeds the rate of water loss by transpiration from exposed surfaces, the eggs swell during incubation. The term ‘cleidoic’ cannot be used to describe eggs of this type. 3. Embryos of lizards and snakes influence the water potential of extra-embryonic fluids contained within their eggs, thereby maintaining or increasing the gradient in water potential that drives water absorption. 4. Embryos of Crocodilia and Chelonia obtain a substantial portion of the calcium used in ossification of skeletal elements from the inner surfaces of the eggshell. In contrast, embryonic lizards and snakes draw upon extensive reserves of calcium present in the yolk, and obtain little (if any) calcium from the eggshell. 5. All reptilian embryos seem to produce substantial quantities of urea as a detoxification product of protein catabolism. Contrary to expectation, uricotelism may not be common among reptilian embryos, even in those few instances where development takes place within a hard, calcareous egg. 6. In eggs of Crocodilia and Chelonia, respiratory gases seem to pass by diffusion through pores in the calcareous eggshell and through spaces between the fibres of the pair of egg membranes. No pores have been observed in the shell of lepidosaurian eggs, and so gases presumably diffuse between the fibres of the single (multilayered) shell membrane. 7. Metabolism of reptilian embryos is temperature-dependent, as is true for most ectothermic organisms. For each species, there appears to be a particular temperature at which embryonic development proceeds optimally, and departures from this optimum elicit increases in developmental anomalies and/or embryonic mortality. 8. Viviparity has evolved on numerous occasions among species of the Squamata, but seemingly never among Crocodilia or Chelonia. Since the evolution of viviparity entails a progressive reduction in the eggshell, only those organisms whose embryos do not depend upon the eggshell as a source of calcium may have the evolutionary potential to become viviparous. 9. Evolutionary transitions from oviparity to viviparity could have been driven by selection related to (i) thermal benefits to embryos consequent upon retention of eggs within the body of a parent capable of behavioural thermoregulation; (ii) protection of the eggs from nest predators and/or soil microbes; and (iii) more effective exploitation of a seasonal food resource by early emerging young.

Evolutionary strategies in lizard reproduction.

Abstract: Several investigators have dealt in a theoretical way with the evolution of reproductive rates and attendant life history phenomena (Cole, 1954; Lack, 1954, 1966, 1968; Murphy, 1968; Svardson, 1949; Williams, 1966a, 1966b). Tinkle (1969a) has applied evolutionary principles in an attempt to construct a general theory of the evolution of single-broodedness and iteroparity, of viviparity, and of clutch size and clutch number in lizards. Most of the data presented by him were qualitative. In this paper we pose a series of questions concerning reproductive strategies which have evolved among one group of vertebrates (the lizards), and provide quantitative data to answer them. We further present comparable data from birds, the vertebrate group most thoroughly studied in this respect. Finally, we suggest the weaknesses in studies of reptilian reproduction in the hope of stimulating future workers to collect data that are essential to answer these specific questions.

The Ecological Significance of Sexual Dimorphism in Size in the Lizard Anolis conspersus.

Abstract: Adult males of Anolis conspersus capture prey of significantly larger size and occupy perches of significantly greater diameter and height than do adult females; similarly, these three dimensions of the niche are significantly larger for adult females than for juveniles. Adult males on the average eat a smaller number of prey, and the range in size of prey is larger. The relationship between the average length of the prey and that of the predator is linear when the predator size is above 36 millimeters, but becomes asymptotic when it is below that value. Subadult males as long as adult females eat significantly larger food than do the latter, but only in the larger lizards is this correlated with a relatively larger head. Anolis conspersus selects prey from a wide range of taxa and shows no obvious intraspecific specialization not connected to differences in microhabitat and prey size. The efficiency of this system for solitary species is pointed out.

The Concept of Reproductive Effort and Its Relation to the Evolution of Life Histories of Lizards

Abstract: Most aspects of the life histories of individual organisms are explicable in terms of natural selection, a fact often neglected in life history studies, with the result that such studies rarely contain the type of information necessary to test evolutionary hypotheses concerning life history phenomena. Williams (1966a, 1966b) has directed attention to life history phenomena that generally should be explicable from evolutionary considerations. He has made the prediction that a higher per season reproductive effort should characterize small, short-lived rather than larger, long-lived species. He has, as a corollary, cited differences in behavior that might be expected between species with differing demographic properties. Tinkle (1969) presented data on the lizard Uta stansburiana which accord with Williams's hypothesis. One purpose of the present paper is to compare reproductive effort of many species, using criteria suggested by Williams (1966a, 1966b) to determine how well lizard species accord with Williams's hypotheses. A second purpose is to formulate a general theory for the evolution of life history types in lizards.

Brain evolution relating to family, play, and the separation call.

Abstract: • Mammals stem from the mammal-like reptiles (therapsids) that were widely prevalent in Pangaea 250 million years ago. In the evolutionary transition from reptiles to mammals, three key developments were (1) nursing, in conjunction with maternal care; (2) audiovocal communication for maintaining maternaloffspring contact; and (3) play. The separation call perhaps ranks as the earliest and most basic mammalian vocalization, while play may have functioned originally to promote harmony in the nest. How did such family related behavior develop? In its evolution, the forebrain of advanced mammals has expanded as a triune structure that anatomically and chemically reflects ancestral commonalities with reptiles, early mammals, and late mammals. Recent findings suggest that the development of the behavioral triad in question may have depended on the evolution of the thalamocingulate division of the limbic system, a derivative from early mammals. The thalamocingulate division (which has no distinctive counterpart in the reptilian brain) is, in turn, geared in with the prefrontal neocortex that, in human beings, may be inferred to play a key role in familial acculturation.