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The biological study of the geographic distribution of animals, especially the causes and effects of such distribution.
zoogeographer zo'o·ge·og'ra·pher n.The subdivision of the science of biogeography that is concerned with the detailed description of the distribution of animals and how their past distribution has produced present-day patterns. Scientists in this field attempt to formulate theories that explain the present distributions as elucidated by geography, physiography, climate, ecological correlates (especially vegetation), geological history, the canons of evolutionary theory, and an understanding of the evolutionary relationships of the particular animals under study.
The field of zoogeography is based upon five observations and two conclusions. The observations are as follows. (1) Each species and higher group of animals has a discrete nonrandom distribution in space and time (for example, the gorilla occurs only in two forest areas in Africa). (2) Different geographical regions have an assemblage of distinctive animals that coexist (for example, the fauna of Africa south of the Sahara with its monkeys, pigs, and antelopes is totally different from the fauna of Australia with its platypuses, kangaroos, and wombats). (3) These differences (and similarities) cannot be explained by the amount of distance between the regions or by the area of the region alone [for example, the fauna of Europe and eastern Asia is strikingly similar although separated by 6900 mi (11,500 km) of land, while the faunas of Borneo and New Guinea are extremely different although separated by a tenth of that distance across land and water]. (4) Faunas strikingly different from those found today previously occurred in all geographical regions (for example, dinosaurs existed over much of the world in the Cretaceous). (5) Faunas resembling those found today or their antecedents previously occurred, sometimes at sites far distant from their current range (for example, the subtropical-warm temperate fauna of Eocene Wyoming, including many fresh-water fishes, salamander, and turtle groups, is now restricted to the southeastern United States).
The conclusions are as follows. (1) There are recognizible recurrent patterns of animal distribution. (2) These patterns represent faunas composed of species and higher groups that have evolved through time in association with one another.
Two rather different approaches have dominated the study of zoogeography since the beginning of the nineteenth century: ecological and historical. Ecological zoogeography attempts to explain current distribution patterns principally in terms of the ecological requirements of animals, with particular emphasis on environmental parameters, physiological tolerances, ecological roles, and adaptations. The space and time scales in this approach are narrow, and emphasis is upon the statics and dynamics of current or very recent events. Historical zoogeography recognizes that each major geographical area has a different assemblage of species, that certain systematic groups of organisms tend to cluster geographically, and that the interaction of geography, climate, and evolutionary processes over a long time span is responsible for the patterns or general tracks. Emphasis in this approach is upon the statics and dynamics of major geographical and geological events ranging across vast areas and substantial time intervals of up to millions of years. The approach is based on concordant evolutionary association of diverse groups through time. See also Ecology.
Defining the location and numbers of animal populations, and their variability with time.
Zoogeography is the branch of the science of biogeography that is concerned with the geographic distribution of animal species and their attributes. That makes Zoogeography the study of patterns of biodiversity regarding time and space.
Zoogeography is the study of the patterns of the past, present, and future distribution of animals (and their attributes) in nature and the processes that regulate these distributions, and it’s the scientific analysis of the patterns of biodiversity regarding time and space. Zoogeography integrates information on the historical and current ecology, genetics, and physiology of organisms and their interaction with environmental processes (continental drift, climate) in regulating geographic distributions of animals. Scientists use descriptive and analytical approaches useful in hypothesis testing in zoogeography and which illustrates the applied aspects of zoogeography (e.g. refuge design in conservation).
Zoogeography is often divided into two main branches: Ecological Zoogeography and Historical Zoogeography. The former investigates the role of current day biotic and abiotic interactions in influencing animal distributions; the latter are concerned with historical reconstruction of the origin, dispersal, and extinction of taxa.
It’s part of a more general science known as biogeography. Phytogeographers are concerned with patterns and process in plant distribution. Most of the major questions and kinds of approaches taken to answer such questions are held in common between phyto- and zoogeographers.
Green sea turtles (Chelonia mydas) on Ascension Island – dispersal or vicariance?
Green turtles live in tropical oceans worldwide. Ascension Island's rookery is located on the mid-Atlantic ridge between Brazil and Liberia near west Africa. Their feeding grounds are around the coastal areas of South America, and their females lay eggs on South American beaches.
With a distance of around 2000km (1242mi) from the main body of the range, how did the turtles establish a colony on Ascension Island that is so isolated?
Dispersal hypothesis: these animals make very long distance migrations of up to 5,000 km (3,106mi) between feeding and nesting areas and dispersed from South America to Ascension Island.
Vicariance hypothesis: aka the "Carr-Coleman" hypothesis after two long term investigators of turtle biology. Hypothesis suggests that ancestors of Ascension Island turtles nested on beaches of islands adjacent to S.A. coast throughout the late Cretaceous (135-65 mya).
Over the last 70 my, these islands have been displaced by "sea-floor spreading" (2 cm/year). This, coupled with the natal homing ability of turtles, resulted in the present colony on Ascension Island.
Q: How can zoogeographic investigation provide a test to distinguish these hypothesis? Dispersal and vicariance hypotheses are part of an age-old divide in zoogeographic inference (more on that later!). What predictions do the two hypotheses make that can be used to distinguish between them by collecting data?
A: One approach was taken by Bowen et al. (1992) who used molecular assays (mitochondrial DNA) to address this problem. They reasoned that the "vicariant hypothesis" implies that the Ascension and S.A. rookeries have been largely isolated over 70 million years and that such long term isolation should result in major genetic differences between the rookeries.
By contrast, the dispersal hypothesis predicts very recent contact between the S.A. and Ascension Island rookeries (perhaps even to the present day) and hence little long term evolutionary isolation and consequently there should be little genetic divergence between the rookeries.
What was the result? In a nutshell, sequence divergence estimates between Ascension Island and S.A. rookeries were VERY low (about 0.2% sequence divergence). Most "haplotypes" were identical (i.e. shared) between the two rookery areas which suggested that the rookeries had only been isolated for only a very short time (less than 1 million years) and that this isolation was incomplete (there was current dispersal between Brazil and Ascension Island rookeries).
The shallow genetic divergence (contrasted with a major split at about 0.7% divergence between Atlantic and Pacific groups of C. mydas) was inconsistent with long term isolation predicted by the vicariance hypothesis. These results, coupled with ecological knowledge of the dispersal capabilities of green turtles strongly suggest that the dispersal hypothesis for the origin of the Ascension Island rookery is correct.
1. Brown, J.H. & Lomolino, M.V. 1998. Biogeography. 2nd edition. Chapter 1.
2. Avise, J.C. 1994. Molecular markers, natural history and evolution. Chapman and Hall. Pp. 224-226.
3. Bowen, B.W. et al. 1992. Global population structure and natural history of the green turtle (Chelonia mydas) in terms of matriarchial phylogeny. Evolution 46: 865-881.
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