Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

The Theory of Island Biogeography

Ecological extinction caused by overfishing precedes all other pervasive human disturbance to coastal ecosystems, including pollution, degradation of water quality, and anthropogenic climate change. Historical abundances of large consumer species were fantastically large in comparison with recent observations. Paleoecological, archaeological, and historical data show that time lags of decades to centuries occurred between the onset of overfishing and consequent changes in ecological communities, because unfished species of similar trophic level assumed the ecological roles of overfished species until they too were overfished or died of epidemic diseases related to overcrowding. Retrospective data not only help to clarify underlying causes and rates of ecological change, but they also demonstrate achievable goals for restoration and management of coastal ecosystems that could not even be contemplated based on the limited perspective of recent observations alone.

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Historical overfishing and the recent collapse of coastal ecosystems.

The principles of classification and a classification of mammals. Bulletin of the AMNH ; v. 85

Degradation of coral reef ecosystems began centuries ago, but there is no global summary of the magnitude of change. We compiled records, extending back thousands of years, of the status and trends of seven major guilds of carnivores, herbivores, and architectural species from 14 regions. Large animals declined before small animals and architectural species, and Atlantic reefs declined before reefs in the Red Sea and Australia, but the trajectories of decline were markedly similar worldwide. All reefs were substantially degraded long before outbreaks of coral disease and bleaching. Regardless of these new threats, reefs will not survive without immediate protection from human exploitation over large spatial scales.

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Global Trajectories of the Long-Term Decline of Coral Reef Ecosystems

Can sexual dimorphism evolve because of ecological differences between the sexes? Although several examples of this phenomenon are well known from studies on birds, the idea has often been dismissed as lacking general applicability. This dismissal does not stem from contradictory data so much as from the difficulties inherent in testing the hypothesis, and its apparent lack of parsimony, in comparison to the alternative explanation of sexual selection. The only unequivocal evidence for the evolution of sexual dimorphism through intersexual niche partitioning would be disproportionate dimorphism in trophic structures (e.g., mouthparts). This criterion offers a minimum estimate of the importance of ecological causes for dimorphism, because it may fail to identify most cases. A review of published literature reveals examples of sexually dimorphic trophic structures in most animal phyla. Many of these examples seem to be attributable to sexual selection, but others reflect adaptations for niche divergence between the sexes. For example, dwarf non-feeding males without functional mouthparts have evolved independently in many taxa. In other cases, males and females differ in trophic structures apparently because of differences in diets. Such divergence may often reflect specific nutritional requirements for reproduction in females, or extreme (sexually selected?) differences between males and females in habitats or body sizes. Ecological competition between the sexes may be responsible for intersexual niche divergence in some cases, but the independent evolution of foraging specializations by each sex may be of more general importance. If ecological causation for dimorphism can be demonstrated in so many cases, despite the inadequacies of the available criteria, the degree of sexual size dimorphism in many other animal species may well also have been influenced by ecological factors. Hence, it may be premature to dismiss this hypothesis, despite the difficulty of testing it.

Ecological Causes for the Evolution of Sexual Dimorphism: A Review of the Evidence

Quantitative analysis of samples of the stomach contents of 95 north Queensland dugongs, Dugong dugon, (63 from the Townsville area, 30 from the Mornington Island area and 2 from the Torres Strait area) and one dugong from south Queensland indicates that the diet of most consisted almost entirely of seagrasses of all available genera. Halodule was found in 95% of stomachs, followed by Halophila (89%). Cymodocea (61%) and Thalassia (39%). Seagrass rhizomes were present in all stomachs examined including that of a newborn calf. The generic composition of the stomach contents probably reflects that of the seagrass beds in the areas where the dugongs were captured and is not necessarily indicative of discrimination in selecting food. Non-epiphytic algae occurred in 51% of the stomachs, usually in small amounts. When seagrasses were abundant, dugongs appeared to eat algae often but only in very small amounts (<2% of food volume). Dugongs do not appear to be well adapted to utilize algae as food and probably usually consume them incidentally with seagrasses. Many of the dugongs which drowned in the shark nets near Townsville in the year after a cyclone had severely damaged the seagrass beds in the area, had eaten more of the seagrasses Cymodocea and Thalassia, less of the seagrasses Halodule and Halophila, and more algae than animals which died in other years.

Analysis of Stomach Contents of Dugongs From Queensland.

Study of the gonads of 108 dugongs from north Queensland indicates that neither females nor males are continuously in breeding condition. The gonadal activity of males in a population is not synchronized. Ovaries tend to be active in the latter half of the year. There is no evidence for females coming into oestrus soon after giving birth but conception can occur during lactation. In the Townsville-Cairns area, dugongs calve from August-September through December. Neonates are between 1.0 and 1.3 m long and weigh 20-35 kg. Dugongs of both sexes less than 2.2 m long are likely to be immature, those over 2.5 m long are probably mature, and the status of animals between 2.2 and 2.5 m long is uncertain. The pre-reproductive period seems to be very variable but is a minimum of 9-10 years for both sexes. The gestation period is about 1 year and lactation can last at least 1.5 years. The usual litter size is one. The secondary and tertiary sex ratios are 1:1. Estimates of the calving interval based on pregnancy rates, the rate of accumulation of placental scars, and calf counts from aerial surveys and photographs, range from 3 to 7 years for various populations. A simple population model has been used to calculate the relationship between calving interval and adult mortality rate for stationary populations with different pre-reproductive periods and juvenile mortality rates. Even the most optimistic schedule of reproduction and juvenile mortality demands an adult survivorship of about 90% per year for population maintenance.

Breeding Cycle, Life History and Population Dynamics of the Dugong, Dugon dugon (Sirenia: Dugongidae

Using atomic absorption spectroscopy, exceptionally high concentrations of iron (778 to 82,363 μg g+1 dry weight) and zinc (219 to 4,183 μg g+1 dry weight) were detected in the livers of Dugong dugon (Muller) from north Queensland compared with reported values for other marine mammals from other areas of the world Levels of copper (91 to 608 μg g+1 dry weight), cadmium (<01 to 59 μg g+1 dry weight), cobalt (05 to 72 μg g+1 dry weight) and silver (02 to 39 μg g+1 dry weight) in the liver, and cadmium (02 to 209 μg g+1 dry weight) in the kidney were also relatively high in several samples, whilst concentrations of nickel, lead and chromium were consistently below the limits of detection in all tissues Manganese concentrations, in all tissues examined, were generally comparable with those reported from other marine mammals Tissue concentrations of a number of metals varied with the age of the dugong Levels of iron, zinc, cadmium and cobalt in the liver zinc and cadmium in the kidney, and iron in the muscle were significantly positively correlated with age Copper and manganese in both liver and kidney were negatively correlated with age Large deposits of the iron-rich pigment, haemosiderin, the quantity of which also tended to increase with age, was a conspicuous feature of the livers of all the post-natal dugongs examined histologically It seems unlikely that the unusual metal status of the dugong reflects anthropogenic activities, since many individuals were collected in remote areas far from major sites of urbanization and industrialization Seagrasses, the major food of dugongs, were collected from various north Queensland dugong habitat-areas and analysed Very high concentrations of iron but low levels of copper were detected The significance of such dietary imbalances and their possible influence on the metal status of the dugong were therefore considered

GE Heinsohn

Papers

Analysis of Stomach Contents of Dugongs From Queensland.

Breeding Cycle, Life History and Population Dynamics of the Dugong, Dugon dugon (Sirenia: Dugongidae

The unusual metal status of the dugong Dugon dugon

Effects of a tropical cyclone on littoral and sub-littoral biotic communities and on a population of Dugongs (Dugong dugon (Müller))

Variation in responses of arboreal marsupials to fragmentation of tropical rainforest in north eastern Australia