Reptile Populations Research Articles

Fire Studies in Mallee (Eucalyptus Spp.) Communities of Western New South Wales: Reptile and Beetle Populations in Sites of Differing Fire History.

Reptile and terrestrial beetle populations were sampled within adjoining mallee communities of similar botanical composition, but differing in fire history and vegetation structure. Studies were aimed at determining whether there were any major differences between faunal communities in sites with different fire histories. While the number of beetle species captured was significantly higher in the two most recently burnt sites, overall abundance of beetles did not differ significantly between various fire histories. Captures of Carenurn interiove were highest in a site burnt seven years prior to the study whereas captures of Tvichocarenum sp. were most common in the two most recently burnt areas. The number of reptile species captured did not differ significantly between sites but the relative abundance of nocturnal and diurnal reptiles was found to be significantly related to time since last fire. The number of geckos captured at the oldest fire site (burnt 18 years earlier) were significantly fewer than at the more recently burnt sites whereas captures of diurnal lizards did not differ. These patterns of reptile abundance are consistent with those found in other fire studies undertaken in similar habitats. This preliminary study confirms that both reptiles and beetles may be usefully incorporated in future management systems designed to monitor biological diversity in mallee ecosystems. Key words: fire, mallee, porcupine grass, nocturnal and diurnal reptiles and beetles

Vitellogenin induction by xenobiotic estrogens in the red-eared turtle and African clawed frog.

Many environmental pollutants have estrogenic activity in animals. Xenobiotic estrogens include many pesticides and industrial chemicals that biocumulate. The impact of these common pollutants on the reproductive success of wildlife may be considerable, particularly in threatened or endangered species. This research examined the use of plasma vitellogenin in males as a biomarker for estrogenic xenobiotics in reptiles and amphibians. Adult male turtles (Trachemys scripta) and frogs (Xenopus laevis) were given ip injections of estradiol-17 beta (E2), diethylstilbestrol (DES), or o,p'-DDT (1-chloro-2-[2,2,2-trichloro-1-(4-chlorophenyl)ethyl)benzene) daily for 7 days, and plasma was collected on day 14. The estrogenic activity of each compound was determined by measuring the induction of plasma vitellogenin. Vitellogenin was identified by precipitation, electrophoresis, Western blot, and enzyme-linked immunosorbant assay (ELISA). In both species, estradiol and DES treatments induced the most vitellogenin, whereas DDT treatments induced smaller amounts of vitellogenin in a dose-dependent fashion. These data indicate that induction of plasma vitellogenin in males may be a useful biomarker of xenobiotic estrogen activity in wild populations of reptiles and amphibians.

Immunology

<h3>Abstract</h3> Carotenoid-based polymorphisms are widespread in populations of birds, fish, and reptiles¹, but little is known of how they affect fitness and are maintained as species multiply². We report a combined field and molecular-genetic investigation of a nestling beak color polymorphism in Darwin’s finches. Beaks are pink or yellow, and yellow is recessive³. Here we show that the polymorphism arose in the Galápagos approximately half a million years ago through a regulatory mutation in the <i>BCO2</i> gene, and is shared by 14 descendant species. The frequency of the yellow genotype is associated with cactus flower abundance in cactus finches, and is altered by introgressive hybridization. The polymorphism is most likely a balanced polymorphism, maintained by ecological selection pressures associated with diet, and augmented by occasional interspecific introgression. Polymorphisms that are hidden as adults, as here, may contribute to evolutionary diversification in underappreciated ways in other systems.

THE EVOLUTION OF REPRODUCTIVE EFFORT IN SQUAMATE REPTILES: COSTS, TRADE-OFFS, AND ASSUMPTIONS RECONSIDERED.

We evaluated Shine and Schwarzkopf's (SS) model of the evolution of reproductive effort (RE) in squamate reptiles. They suggested that fecundity trade-offs were unimportant in the evolution of RE in most squamate reptiles and that only survival trade-offs needed to be considered. However, we show that by assuming no variation in offspring size exists, and that adult mortality is episodic, the results of the SS model are not general. By extension, we argue that conclusions drawn about factors important in the evolution of RE in squamate reptiles are premature. Using a modified version of the SS model, we demonstrate that variation in the form of trade-offs relating offspring size and survival substantially affect relationships among clutch size, relative clutch mass, and lifetime reproductive success. We also demonstrate that the way in which adult mortality is simulated drastically affects conclusions about the potential fecundity trade-offs experienced by populations of squamate reptiles. Finally, we suggest that a complete understanding of the evolution of RE will come from theory that incorporates trade-offs between offspring size and quality, as well as other system-specific constraints on the allocation of energy to growth, maintenance, storage, and reproduction.

Changes in the vegetation and reptile populations on Round Island, Mauritius, following eradication of rabbits

Changes in the vegetation and reptile populations on Round Island, Mauritius are described using the results of expeditions in 1982 (when rabbits Oryctolagus cuniculus were abundant) and 1989 (three years after their eradication). Changes in vegetation cover and composition are described, all directly or indirectly attributable to the eradication of rabbits. These changes include marked increases in the regeneration of three tree species (all endemic, or largely restricted, to Round Island) and plant species formerly grazed by rabbits. The increasing impact of plant species accidentally introduced to the island is documented. Recent increases in the populations of several endemic reptile species (five of which are threatened) are also described; these can be attributed to increases in habitat and food availability following the eradication of rabbits. In the light of these observations, projected changes are discussed and recommendations made for management.

Ageing in Reptiles

Like in fishes, the reptiles appear to show three types of senescence. The African skink, Mabuya buettneri, shows rapid senescence similar to death at mating observed in Salmon and marsupial mouse. Most of the lizards and snakes undergo gradual senescence comparable to the pattern exhibited by a majority of vertebrates. On the other hand, turtles, tortoises and crocodiles continue to grow throughout life and are thus credited with slow or negligible senescence. Evidences and mechanisms of rapid or negligible senescence in reptiles are still fragmentary and unclear. Findings in a few species of lizards (Calotes versicolor) and snakes (Natrix natrix) showing gradual senescence support the concept of commonalities in ageing phenomena in vertebrates. An age-related increase in the stability of collagen and accumulation of altered enzyme molecules, a decrease in metabolism and response to stress-enhanced anti-oxidative defence mechanisms and the nature of responses to hormones, restricted diet and lower environmental temperature corroborate the concept. On the other hand neither the increase in mortality rate and accumulation of lipofuscin nor the reproductive senility have been shown conclusively in ageing reptile populations. It is likely that there are multiple mechanisms of senescence in reptiles. Further studies on selected species from among the 6,000 living species are necessary to unravel the phenomena.

Reptile fauna of the Katse Dam catchment area and a biogeographical assessment of species composition in the Lesotho Highlands

A survey of the reptile fauna of the Katse Dam catchment area in the Lesotho Highlands was conducted to assess the possible impact of the dam, once it is full, on reptile populations in the area. With only seven lizard and five snake species recorded to date, species richness in the catchment area is much lower than expected. It is inferred that species richness in the western and central districts of the Lesotho Highlands in general, is low, emphasising the role of the Drakensberg-Maluti mountain complex as a barrier to species dispersal. The reptile fauna of the western/central highland areas is primarily composed of widespread generalist species. The eastern highland areas, on the other hand, have a substantial endemic component. indicating the greater potential of these areas as a conservatory of geographical isolates. The direct impact of the Katse Dam on the local reptile fauna is expected to be minimal. Snake numbers are low in the catchment area and this may be the result of human impact. Reproductive cycles of the lizard species in the catchment area do not differ from the cycles of the same species at lower altitudes elsewhere.

Experimental transmission ofCowdria ruminantium (Rickettsiales) by the American reptile tickAmblyomma dissimile Koch, 1844

A Senegalese isolate of the rickettsia Cowdria ruminantium was transmitted transstadially by nymphs of the American reptile tick Amblyomma dissimile. Only eight nymphs, fed as larvae on a Saanen goat reacting to heartwater, were required to transmit fatal heartwater to another susceptible goat. Since A. dissimile usually feeds on snakes, iguanas and lizards in central America, the tick is not considered to play a significant role in the transmission of heartwater between ruminants. However, the tick could play a role in maintaining a rickettsial reservoir in reptile populations, since it has been shown that an African reptile can be a subclinical carrier of C. ruminantium, infective to vector ticks.

The role of introduced species in shaping the distribution and abundance of island reptiles

Species interactions, as revealed by historical introductions of predators and competitors, affect population densities and sometimes result in extinctions of island reptiles. Mongoose introductions to Pacific islands have diminished the abundance of diurnal lizards and in some cases have led to extinctions. Through these population level effects, biogeographic patterns are produced, such as the reciprocal co-occurrence pattern seen with the tuatara and its predator, the Polynesian rat, and with the tropical gecko competitorsHemidactylus frenatus andLepidodactylus lugubris in urban habitats in the Pacific. Although competition has led to changes in abundance and has caused habitat displacement and reduced colonization success, extinctions of established reptile populations usually occur only as a result of predation.

Elevational Patterns of Species Richness, Evenness, and Abundance of the Costa Rican Leaf-Litter Herpetofauna

The abundance, species richness, and evenness of the Costa Rican leaf-litter herpetofauna was estimated during the late wet season of 1985 by quantitative sampling of replicate plots at ten sites encompassing an elevation range of 3 to 1670 m. Species richness was positively correlated with leaf-litter depth, and negatively correlated with elevation. Herpetofaunal density also tended to increase with litter depth and decline with elevation. A strong positive correlation existed between species richness and herpetofaunal density. Evenness was highly variable and independent of both leaf-litter depth and elevation. Analysis of a subset of the data, representing an elevational transect from Tortuguero to the Braulio Carrillo National Park Extension, yielded similar results. Tropical leaf-litter reptiles and amphibians appear to be both more diverse and more abundant at lower elevations. Sites with deep leaf litter generally sustain dense and diverse reptile and amphibian populations. Local herpetofaunas typically consist of a few very common species along with a large number of comparatively rare species. REPTILES AND AMPHIBIANS are a major constituent of the fauna inhabiting tropical forest litter. Studies of tropical leaf-litter herpetofaunas have emphasized patterns of abundance and distribution among geographic regions (Lloyd et al. 1968; Heyer & Berven 1973; Scott 1976, 1982; Inger 1980a, b; Heatwole 1982), vegetational zones (Brown & Alcala 1961, Heatwole & Sexton 1966, Heyer 1967), and elevational gradients (Brown & Alcala 1961, Scott 1976) as well as seasonal changes (Lieberman 1982, 1986). It has become generally accepted that leaf-litter reptiles and amphibians are more abundant in the New World Tropics than in Southeast Asia (Scott 1976, Inger 1980b, Duellman & Trueb 1986) although the exact reason remains a subject of debate (May 1980). Similarly, the general consensus is that the abundance of tropical leaf-litter herpetofaunas increases with increasing elevation, while species richness and equitability both decline (Brown & Alcala 1961, Scott 1976, Heatwole 1982, Duellman & Trueb 1986). Scott (1976) attributed this pattern to greater overall forest productivity at intermediate elevations, coupled with increased densities of the most common species at higher elevations. Before attempting to determine the mechanisms responsible for observed patterns of tropical leaf-litter herpetofaunal abundance and diversity, we must document the phenomenon conclusively. Previous quantitative studies have sampled few sites, have been unable to provide replicated samples (Brown & Alcala 1961), or may have confounded site and year effects by sampling different sites in different years (Scott 1976). We surveyed the Costa Rican leaf-litter herpetofauna by quantitatively sampling replicate plots at ten sites, ranging from 3 to 1670 m in elevation, during the late wet season of July-September 1985. Our sampling strategy permitted statistical analyses to determine the relationship between litter depth and elevation, and leaf-litter herpetofaunal richness, evenness and abundance. The results of our study contradict several of the generally accepted patterns of tropical leaf-litter herpetofaunal abundance and diversity.

Habitats of the lizards Lacerta agilis and Lacerta vivipara on forest ride verges in Britain

The ecology of the two lizard species Lacerta agilis and Lacerta vivipara were studied within coniferous plantations. These two species use three areas: unplanted areas such as fire breaks or areas where crops have failed; compartments where planting has occurred but tree canopy formation later makes the habitat unsuitable; and ride verges. The study was designed to compare the two lizard species in terms of their use of ride verges. The distribution of the two species along the verges was determined in part by the characteristics of ground flora, the surrounding tree canopy and by the slope and aspect. It was found that the two species were associated with different kinds of vegetation. Although the vegetation of the rides is similar to that of open heathland, the ride habitat may have limited use because the plantation trees restrict the duration of sunshine received at the surface. Both species were found to be limited in their distribution along ride verges relative to a sunshine index. Data from this research could usefully be used in the conservation of small reptile populations within coniferous plantations.

Reptile and frog utilisation of rehabilitated bauxite minesites and dieback-affected sites in Western Australia's Jarrah Eucalyptus marginata forest

Alcoa of Australia Limited rehabilitate bauxite mined areas in the southwest of Western Australia. One of the aims of the revegetation programme is to promote the return of fauna species which inhabit areas prior to mining. This paper discusses the extent to which reptile and frog species utilise revegetated bauxite minesites. It was shown that 4–6 year old revegetated sites support similar numbers of reptile species as unmined sites, although densities are comparable to values recorded in poorer quality forest. Species utilisation of revegetated sites depended largely on the particular species microhabitat preferences. Comparison of community composition in various sites demonstrated high degrees of similarity between some rehabilitated sites and high quality forest sites. The effects of jarrah dieback disease on reptile and frog populations was also assessed. From the results, it is possible to assess the likely combined impact of dieback and mining on the longer term conservation of jarrah forest reptile and frog species.

Fish, Amphibian, and Reptile Inventory for the Bighorn Canyon National Recreation Area

This study was designed to inventory fish, amphibian, and reptile populations inhabiting the Bighorn Canyon National Recreation Area using standard sampling techniques and field observations in order to determine species composition, distribution, relative abundance, and habitat associations.

ON THE MEASUREMENT OF NATURAL AND SEXUAL SELECTION: APPLICATIONS.

In this paper, we use measures of selection developed by quantitative geneticists and some new results (Arnold and Wade, 1984) to analyze multiple episodes of selection in natural populations of amphibians, reptiles, and insects. These examples show how different methods of data collection influence the potential for relating field observations to formal evolutionary theory. We adhere to the Darwinian tradition of distinguishing between natural and sexual selection (Darwin, 1859, 1871; Ghiselin, 1974). We view sexual selection as selection arising from variance in mating success and natural selection as arising from variance in other components of fitness. The justification for this formal distinction is developed by Wade (1979), Lande (1980), Wade and Arnold (1980), Arnold and Houck (1982) and Arnold (1 983 a). (We define mating success as the number of mates that bear progeny given survival of the mating organsim to sexual maturity. We do not equate mating success with mere copulatory success.) The utility of the distinction between sexual and natural selection is that the two forms of selection may often act in opposite directions on particular characters (Darwin, 1859, 1871). While we find the distinction between these two forms of selection useful, the difference is not crucial to our analysis. The essential point is that the recognition of selection episodes permits analysis of selection that may change in magnitude and direction during the life cycle. Defining Fitness Components. -The key first step in the analysis of data is to define multiplicative components of fitness so that selection can be partitioned into parts corresponding to these components or episodes of selection. Using an animal example, if the number of offspring zygotes is taken as total fitness, we can define the following components of fitness: viability (survivorship to sexual maturity), mating success (the number of mates) and fertility per mate (the average number of zygotes produced per mate). These components of fitness are defined so that their product gives total fitness. As a second example, consider the components of fitness in a plant in which yield (seeds/plant) is taken as the measure of total fitness (Primack and Antonovics, 1981). We might define the following components of fitness: number of stems per plant, average number of inflorescences per stem, average number of seed capsules per inflorescence, and average number of seeds per capsule. Again, these four fitness components are defined so that their product gives total fitness. We will need to measure each component of fitness and each character on each individual in order to partition selection into parts corresponding to the separate episodes of selection or to the separate components of fitness. Thus in the animal example, we need to measure the viability, mating success and fertility of each individual. With this accomplished we can estimate the separate forces of viability, sexual and fertility selection on each phenotypic character. In addition we can calculate the opportunities of selection corresponding to these three episodes and covariances between the different kinds of selection. In the plant example, we might begin with the intuition that larger plants have a greater yield. Using our methodology we can reword and extend this intuition. We can not only test the proposition of

Round Island in 1982

When a scientific expedition visited Round Island in 1975 it found that introduced rabbits and goats had destroyed most of the vegetation, threatening the survival of the reptiles that depended upon it and causing soil erosion. (See Oryx, 14, page 51.) Eradication of the goats and rabbits was recommended. Seven years later the 1982 Round Island Expedition was launched to monitor the reptile, palm and alien mammal populations. ffPS contributed £100 which was raised through a special appeal. The authors, who participated in both surveys, report on the striking changes that have occurred in just seven years and discuss the future prospects for the island's wildlife, especially for the endemic reptiles.

Recently extinct reptile populations from Mauritius and Réunion, Indian Ocean

Previously unreported material of recently extinct reptiles from Mauritius and Reunion is discussed. It confirms the original presence on Mauritius of three species now largely or entirely confined to nearby Round Island: the gecko Cyrtodactylus serpensinsula, the skink, Leiolopisma telfairii and the boa, Casarea dussumieri. Leiolopisma telfairii is also recorded from Reunion for the first time. Leiolopisma telfairii and the extinct giant Dido–saurus mauritianus are shown to be very similar to each other and quite probably derivatives of a single invading species. D. mauritianus is consequently transferred to Leiolopisma. Apparently pathological tooth structure in this form is also reported.

Populations of Amphibians and Reptiles in the Submontane and Montane Forests of Cuernos de Negros, Philippine Islands

Populations of Amphibians and Reptiles in the Submontane and Montane Forests of Cuernos de Negros, Philippine Islands

Factors Influencing Size and Composition of Populations of Rana clamitans

Recent strides in genetics and evolution have indicated that the development of genetic variation within a population is closely related to the structure of that population. Such factors as size of breeding populations, periodic fluctuations in the size of the population, sex ratio, size of activity range, and differential survival of progeny, determine to a great extent the relative importance of the roles played by mutation, natural selection and random fluctuations of gene frequency in determining the genetic composition of a species (Wright, 1940; Dobzhansky, 1941). Accordingly it is desirable to secure information on the population structure of several kinds of organisms. With the development of statistical methods in recent years much impetus has been given to the study of populations. As a result, many studies have been made of natural populations of animals. These chiefly include animals of direct economic importance, such as plankton and fishes, insects, birds, and mammals. Nevertheless there is still a great lack of adequate comparative data for the above mentioned groups. Some work has been done with populations of reptiles but relatively little study has been made of amphibian populations. This has suggested the present study of the population structure of the green frog, Rana clamitan.s. A description of study areas and general methods is contained in earlier publications (Martof 1953 a, b, 1956). Acknowledgment.-I wish to express my sincere gratitude to Dr. Frederick H. Test for directing this study and to Dr. Cecil C. Craig for his many and valuable suggestikns concerning the statistical treatment of data.

Notes on Amphibian and Reptile Populations in a Louisiana Pineland Area

Notes on Amphibian and Reptile Populations in a Louisiana Pineland Area

Observations on Louisiana Captive Snakes

and New Orleans has a large reptile population embracing a wide variety of species. A casual study of the snakes of the region was started about ten years ago and from this has developed a sizable backyard collection comprising about 150 specimens each summer, most of which are released or given away as cold weather approaches. Certain miscellaneous observations accumulated during the past several years seem worthy of record. Twenty-one species of snakes have been captured within a radius of 10 miles of Gramercy. Those which are extremely common are: Farancia abacura reinwardtii Natrix erythrogaster transversa Heterodon contortrix Natrix r. rhombifera Lampropeltis getulus holbrookii Natrix sipedon confluens Natrix cyclopion cyclopion Thamnophis sirtalis sirtalis