Ian R. Swingland

Genetic divergence and units for conservation in the Komodo dragon Varanus komodoensis

In the past decade much attention has focused on the role that genetics can play in the formation of management strategies in conservation. Here, we describe genetic diversity in the worlds largest lizard, the Komodo dragon (Varanus komodoensis), examining the evolutionary relationships and population genetic history of the four islands in south–east Indonesia, which form the vast majority of its range. We identify distinct genetic groups for conservation. The population on the island of Komodo shows by far the largest values of genetic divergence and is proposed that it should be a separate conservation management unit. Other populations, surviving either on small islands with substantially reduced genetic variability, or in isolated patches, are identified as particularly vulnerable to stochastic threats and habitat loss. Our results provide an example of how data defining intraspecific levels of genetic divergence can provide information to help management plans, ensure the maintenance of genetic variability across populations and identify evolutionary potential within endangered species.

Living in a patchy environment

Introduction: Patchy environment - an overview 1. Starvation and predation in a patchy environment 2. The response of plants to patchy environments 3. Dynamic stability of a single-species population in a divided and ephemeral environment 4. Variance and patchiness in rates of population change - a planthoppers case history 5. Coexistence in a patchy environment 6. Population dynamics and community structure of parasitic helminths 7. Dung and carrion insects 8. Patchiness and community structure 9. Extinction of finite metapopulations in correlated environments 10. Conservation in a variable environment - the optimal size of reserves 11. Does interdemic group selection occur in commensal house mice (Mus domesticus)? 12. Sex determination and sex ratios in patchy environments

Sex ratio under conditional sex expression

We present a model to show that, when sex depends on environment rather than genotype, the sex expressed under relatively unfavorable conditions will be more abundant. This result refers to numbers of males and females in the population. By contrast, no clear prediction can be made about the allocation of resources to the two sexes. The model is constructed to highlight the logical relationship between the distribution of resources to the two sexes and the relative numbers of males and females. The predicted bias in numbers toward the sex developing under unfavorable conditions depends on the assumption that fitness either increases or decreases steadily according to the quantitative variable on which sex expression depends.

Environmental sex determination in reptiles

In recent years, representatives of more than 40 families of reptiles have been studied to understand how environmental parameters affect sex determination. In this review, we summarise the distribution and taxonomic pattern of sex determining mechanisms, outline the main hypotheses of the adaptive significance of temperature sex determination (TSD), and of skewed population sex ratios. We also examine the competing hypotheses of the physiological and molecular mechanisms involved in TSD.

The ecology of the Mediterranean tortoise Testudo hermanni in Northern Greece (the effects of a catastrophe on population structure and density)

Abstract Two large, dense and viable populations of Testudo hermanni inhabiting adjacent sites in northern Greece were studied over three years. One site experienced severe habitat destruction by fire during the course of the study, and the other may either have been seriously disturbed in a single event several years previously, or is suffering from a continual low level of disturbance. In the stable situation average population density was estimated as 45 tortoises ha −1 and in parts may have reached 100 ha−1 The adult sex ratio was biased 2:1 in favour of males, due to higher female mortality. Most animals were sedentary, but there were some seasonal movements between vegetation types for feeding. The immediate effect of the fire was an estimated 40% population reduction, with juveniles being most severely affected. Subsequently the growth rate of immature animals rose sharply. This study demonstrates the relative resistance of tortoise populations to a sudden and temporary catastrophe, and their high potential for recovery if left undisturbed.

Manipulation of vegetation communities on the Abu Dhabi rangelands. I. The effects of irrigation and release from longterm grazing

The effect on vegetation communities of release from grazing by camels and goats has been investigated in the Baynunah region of Abu Dhabi emirate, in The United Arab Emirates, by the study of an exclosure established 11 years previously. Also the effect of sprinkle irrigation (in the absence of grazing) on the rangeland vegetation was investigated. Perennial species richness was significantly lower outside the exclosure compared with inside on both sand and gravel substrata. Annual species richness however was not significantly different. Perrenial percentage covers were lower outside the exclosure compared with inside, especially on sand substrata. The perennial grass Stipagrostis plumosa (L) showed the greatest difference in percentage cover in this respect. The species richness of annuals and perennials was not significantly different between irrigated and non-irrigated areas within the exclosure. The perennial percentage cover was much greater on sprinkle irrigated sand and gravel substrata. The perennial which benefited the most was Zygophyllum hamiense, Scweinf. Annual percentage cover was lower in irrigated quadrats. Suggestions are made about the effect of intensive grazing on the vegetation communities at Baynunah and on the effectiveness of irrigation as a tool for increasing the quality of the rangeland for livestock and wildlife.

Population Genetic Structure of Aldabra Giant Tortoises

Evolution of population structure on islands is the result of physical processes linked to volcanism, orogenic events, changes in sea level, as well as habitat variation. We assessed patterns of genetic structure in the giant tortoise of the Aldabra atoll, where previous ecological studies suggested population subdivisions as a result of landscape discontinuity due to unsuitable habitat and island separation. Analysis of mitochondrial DNA (mtDNA) control region sequences and allelic variation at 8 microsatellite loci were conducted on tortoises sampled in 3 locations on the 2 major islands of Aldabra. We found no variation in mtDNA sequences. This pattern corroborated earlier work supporting the occurrence of a founding event during the last interglacial period and a further reduction in genetic variability during historical time. On the other hand, significant population structure recorded at nuclear loci suggested allopatric divergence possibly due to geographical barriers among islands and ecological partitions hindering tortoise movements within islands. This is the first attempt to study the population genetics of Aldabra tortoises, which are now at carrying capacity in an isolated terrestrial ecosystem where ecological factors appear to have a strong influence on population dynamics.

Integrated protected area management

List of contributors. Preface. Acknowledgements. List of abbreviations. 1. Protected areas in context M. Holdgate, A. Philips. 2. Designation of and management planning for protected areas C. Newbold. 3. Conservation through development: the protected landscape approach P.A. Ogden. 4. Links between population and environment research programme: possible lessons for integrated protected area management C. Dennis. 5. Identifying priorities for management of large mammals in Mkomazi Game Reserve, Tanzania K.S. Eltringham. 6. Valuation and management of protected areas in Venezuela D.R. Waugh, E. Yerena. 7. Commercialization, structure and sustainability of biodiversity conservation I.R. Swingland. 8. Aquatic biodiversity conservation in wetland and marine protected areas M. Wlakey. 9. Modelling for sustainable forest use K.T. Parker, C.J. Jepma. 10. Conflict analysis and resolution J.N.R. Jeffers. 11. From English moors and meadows to the Amazon rainforest: land use, biodiversity management and forgotten law S.R. Harrop. 12. Aid for environment: the greening of development priorities S. Russell. 13. Training: its importance and responsiveness to changing needs D.R. Waugh. 14. Conclusions and prognosis I.R. Swingland, M. Walkey. Index.

Tropical forests and biodiversity conservation: a new ecological imperative

Biodiversity, or biological diversity, is the number, variety and variability of living organisms. It is used today both as a loose description to embrace the richness and variation of the living world and politically within the context of economics and development for the purposes of national and international conventions and agreements. It has three related components at different levels of organization: genes, species and ecosystems. Genetic diversity is the basis of biodiversity and, although the possible combinations of gene sequences will probably exceed the total number of atoms in the universe, only a small fraction (<1%) of genetic material in higher organisms is outwardly expressed in the form and function of the organism (Thomas, 1992). Species diversity is commonly considered the measure of biodiversity: 1.7 million species have been described although estimates for the total number of extant species range from 5–40 million (even 100 million), mainly consisting of insects and microorganisms. However such estimates, and the numbers of species already identified, depend on how they were described as distinct by taxonomists and systematists — ecologically, morphologically, physiologically, genetically, mathematically? The need for commonly agreed names which define a distinct species is vital to conservation but much confusion and dissent can arise (see also Rojas, 1992).

Manipulation of vegetation communities on the Abu Dhabi rangelands. II. The effects of topsoiling and drip irrigation

The effect of topsoiling on the vegetation communities of Abu Dhabi coastal desart rangelands with sand taken from an inland area of rangeland supporting a different vegetation community, was investigated. The study was carried out on ghanada Island, an inshore desert island which had been extensively topsoiled in the previous 5 years. Parts of the island also had been drip irrigated. Perennial vegetation communities on Ghanada were markedly different on topsoiled areas compared to non-topsoiled areas. However not all the species common in the topsoil source area were subsequently found to be common on the topsoiled areas. Zygophyllum hamiense, thought to be a colonizer of disturbed soil in the source areas, was common on the topsoiled areas. Annual plant species richness was greater on topsoiled areas compared to untreated native soil indicating (i) that the source areas had a greater annual species richness than Ghanada, and (ii) annual species propagules successfully survived the processes of topsoiling. Annual and perennial species richness was not significantly different between irrigated and non-irrigated areas. The perennial percentage cover was greatest on drip irrigated areas and the perennial which benefited the most was Heliotropium kotschyi, probably due to its rhizomous growth habit.