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

Statistical method for testing the neutral mutation hypothesis by DNA polymorphism.

The taxonomic challenge posed by cryptic species (two or more distinct species classified as a single species) has been recognized for nearly 300 years, but the advent of relatively inexpensive and rapid DNA sequencing has given biologists a new tool for detecting and differentiating morphologically similar species. Here, we synthesize the literature on cryptic and sibling species and discuss trends in their discovery. However, a lack of systematic studies leaves many questions open, such as whether cryptic species are more common in particular habitats, latitudes or taxonomic groups. The discovery of cryptic species is likely to be non-random with regard to taxon and biome and, hence, could have profound implications for evolutionary theory, biogeography and conservation planning.

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Cryptic species as a window on diversity and conservation

▪ Abstract Declines and losses of amphibian populations are a global problem with complex local causes. These may include ultraviolet radiation, predation, habitat modification, environmental acidity and toxicants, diseases, changes in climate or weather patterns, and interactions among these factors. Understanding the extent of the problem and its nature requires an understanding of how local factors affect the dynamics of local populations. Hypotheses about population behavior must be tested against appropriate null hypotheses. We generated null hypotheses for the behavior of amphibian populations using a model, and we used them to test hypotheses about the behavior of 85 time series taken from the literature. Our results suggest that most amphibian populations should decrease more often than they increase, due to highly variable recruitment and less variable adult mortality. During the period covered by our data (1951–1997), more amphibian populations decreased than our model predicted. However, there ...

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Global Amphibian Declines: A Problem in Applied Ecology

Systematic Revision of Symbiodiniaceae Highlights the Antiquity and Diversity of Coral Endosymbionts.

Aim
Glaciation and deglaciation and the accompanying lowering and rising of sea levels during the late Pleistocene are known to have greatly affected land mass configurations in Southeast Asia. The objective of this report is to provide a series of maps that estimate the areas of exposed land in the Indo-Australian region during periods of the Pleistocene when sea levels were below present day levels.

Location
The maps presented here cover tropical Southeast Asia and Austral-Asia. The east–west coverage extends 8000 km from Australia to Sri Lanka. The north–south coverage extends 5000 km from Taiwan to Australia.

Methods
Present-day bathymetric depth contours were used to estimate past shore lines and the locations of the major drowned river systems of the Sunda and Sahul shelves. The timing of sea level changes associated with glaciation over the past 250,000 years was taken from multiple sources that, in some cases, account for tectonic uplift and subsidence during the period in question.

Results
This report provides a series of maps that estimate the areas of exposed land in the Indo-Australian region during periods of 17,000, 150,000 and 250,000 years before present. The ancient shorelines are based on present day depth contours of 10, 20, 30, 40, 50, 75, 100 and 120 m. On the maps depicting shorelines at 75, 100 and 120 m below present levels the major Pleistocene river systems of the Sunda and Sahul shelves are depicted. Estimates of the number of major sea level fluctuation events and the duration of time that sea levels were at or below the illustrated level are provided.

Main conclusions
Previous reconstructions of sea-level change during the Pleistocene have emphasized the maximum lows. The perspective provided here emphasizes that sea levels were at their maximum lows for relatively short periods of time but were at or below intermediate levels (e.g. at or below 40 m below present-day levels) for more than half of each of the time periods considered.

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Maps of Pleistocene sea levels in Southeast Asia: shorelines, river systems and time durations

–Color maps are presented that depict Holocene sea level transgressions and probable submerged lakes on the Sunda Shelf in Southeast Asia. The present-day topography of the Sunda Shelf and the existence of present-day submerged depressions on the Sunda Shelf have been detected through spatial analysis of the Sunda Shelf using the Digital Elevation Model (DEM) developed from the ETOPO2 Global 2’ Elevation data. These depressions could be paleo-lakes that existed when the Sunda Shelf was exposed during the Last Glacial Maximum (LGM). These depressions were gradually submerged when the sea level began to rise from –116 m below present-day levels (BPL) during the terminal phase of the LGM, 21 thousand years before present (ka BP) to its maximum, +5m above present-day mean sea level (MSL), during the mid-Holocene (4.2 ka BP). The topography of these depressions is presented on maps and discussed. The results of this study identify several large submerged depressions that may contain sediment dated from the LGM to the mid-Holocene and we recommend that sediment layers be sampled to confirm or disprove the presence of these proposed fresh water paleo-lakes on the Sunda Shelf.

Maps of Holocene sea level transgression and submerged lakes on the Sunda Shelf

Amphibians tend to exhibit conservative morphological evolution, and the application of molecular and bioacoustic tools in systematic studies have been effective at revealing morphologically ‘cryptic’ species within taxa that were previously considered to be a single species. We report molecular genetic findings on two forest-dwelling ranid frogs from localities across Southeast Asia, and show that sympatric evolutionary lineages of morphologically cryptic frogs are a common pattern. These findings imply that species diversity of Southeast Asian frogs remains significantly underestimated, and taken in concert with other molecular investigations, suggest there may not be any geographically widespread, forest-dwelling frog species in the region. Accurate assessments of diversity and distributions are needed to mitigate extinctions of evolutionary lineages in these threatened vertebrates.

High level of cryptic species diversity revealed by sympatric lineages of Southeast Asian forest frogs

Aim

We seek to relate the present distributions of frogs and snakes of Sundaland and the known geological history of the region.



Location

From the Isthmus of Kra to Java and Sulawesi.



Methods

We relate the known ecological requirements of frogs and snakes to their geographical distributions and information on geological history.



Results

Microhabitat requirements for larvae of various groups of frogs are strong predictors of the breadth of their geographical distributions. At the species level, the frog faunas of the Malay Peninsula and Sumatra are the most similar. The Sulawesi frog fauna, mainly derived from Sundaland lineages, shows almost no similarity to the other frog faunas at the species level. The ecological zones occupied by snake species show association with the breadth of their geographical distributions There are only minor differences among similarity ratios for the Malay Peninsula–Sumatran, Malay Peninsula–Borneo, and the Borneo–Sumatra pairs. The Sulawesi snake fauna has distinctly lower similarity with the faunas of the other areas. The similarity ratios between faunas are larger for snakes than for frogs. This difference between the two groups reflects the difference between them in ability to cross salt water barriers, frogs being extremely vulnerable to saline water. Also snakes may establish founder populations more easily as a single gravid female or one carrying stored sperm may introduce a clutch into previously unoccupied territory.



Conclusions

A few species of frogs and snakes probably reached their present, almost ubiquitous distributions in Sundaland within the last few millenia or even more recently. Other widely distributed species may have been able to disperse among land masses within Sundaland until 10,000–17,000 yr BP; the frogs of this category are common in environments that almost certainly characterized the exposed area of the South China Sea. The distributions of other frogs common to the Malay Peninsula, Sumatra and Borneo probably antedate the Pleistocene, as their larval development requires hilly topography which was not generally available on the Pleistocene-exposed bed of the South China Sea. Many of the endemic species of frogs and snakes probably owe their origins to events of the Miocene or earlier. Several genera of frogs and one genus of snakes have undergone extensive speciation and display considerable sympatry and elevational stratification of species, suggesting their present distributions are the result of events as old as the Eocene. We have cast these conclusions in the form of hypotheses that can be tested mainly by the use of molecular genetics, but in some cases, by additional field sampling.

Harold K. Voris

Papers

Maps of Pleistocene sea levels in Southeast Asia: shorelines, river systems and time durations

Maps of Holocene sea level transgression and submerged lakes on the Sunda Shelf

High level of cryptic species diversity revealed by sympatric lineages of Southeast Asian forest frogs

The biogeographical relations of the frogs and snakes of Sundaland

Formation and fate of sedimentary depocentres on Southeast Asia's Sunda Shelf over the past sea-level cycle and biogeographic implications