Fundamentals of Biogeography

Richard John Huggett

• Publisher: Routledge
• Year: 2004
• ISBN:
  9781134349685
• Edition: 2
• Topic: Biological Sciences
• Subtopic: Environmental Science
• Index: Biological Sciences

Fundamentals of Biogeography presents an accessible, engaging and comprehensive introduction to biogeography, explaining the ecology, geography, history and conservation of animals and plants. Starting with an outline of how species arise, disperse, diversify and become extinct, the book examines: how environmental factors (climate, substrate, topography, and disturbance) influence animals and plants; investigates how populations grow, interact and survive; how communities form and change; and explores the connections between biogeography and conservation.The second edition has been extensively revised and expanded throughout to cover new topics and revisit themes from the first edition in more depth. Illustrated throughout with informative diagrams and attractive photos and including guides to further reading, chapter summaries and an extensive glossary of key terms, Fundamentals of Biogeography clearly explains key concepts in the history, geography and ecology of life systems. In doing so, it tackles some of the most topical and controversial environmental and ethical concerns including species over-exploitation, the impacts of global warming, habitat fragmentation, biodiversity loss and ecosystem restoration.

PART I

INTRODUCING BIOGEOGRAPHY

1

WHAT IS BIOGEOGRAPHY?

Biogeographers study the geography, ecology, and evolution of living things. This chapter covers:

• ecology – environmental constraints on living

• history and geography – time and space constraints on living

Biogeographers address a misleadingly simple question: why do organisms live where they do? Why does the speckled rangeland grasshopper live only in short-grass prairie and forest or brush-land clearings containing small patches of bare ground? Why does the ring ouzel live in Norway, Sweden, the British Isles, and mountainous parts of central Europe, Turkey, and southwest Asia, but not in the intervening regions? Why do tapirs live only in South America and southeast Asia? Why do the nestor parrots – the kea and the kaka – live only in New Zealand?

Two groups of reasons are given in answer to such questions as these – ecological reasons and historical-cum-geographical reasons.

ECOLOGY

Ecological explanations for the distribution of organisms involve several interrelated ideas. First is the idea of populations, which is the subject of analytical biogeography. Each species has a characteristic life history, reproduction rate, behaviour, means of dispersion, and so on. These traits affect a population’s response to the environment in which it lives. The second idea concerns this biological response to the environment and is the subject of ecological biogeography. A population responds to its physical surroundings (abiotic environment) and its living surroundings (biotic environment). Factors in the abiotic environment include such physical factors as temperature, light, soil, geology, topography, fire, water, and air currents; and such chemical factors as oxygen levels, salt concentrations, the presence of toxins, and acidity. Factors in the biotic environment include competing species, parasites, diseases, predators, and humans. In short, each species can tolerate a range of environmental factors. It can only live where these factors lie within its tolerance limits.

The speckled rangeland grasshopper

This insect (Arphia conspersa) ranges from Alaska and northern Canada to northern Mexico, and from California to the Great Plains. It lives at less than 1,000 m elevation in the northern part of its range and up to 4,000 m in the southern part. Within this extensive latitudinal and altitudinal range, its distribution pattern is very patchy, owing to its decided preference for very specific habitats (e.g. Schennum and Willey 1979). It requires short-grass prairie, or forest and brush-land openings, peppered with small pockets of bare ground. Narrow-leaved grasses provide the grasshopper’s food source. It needs the bare patches to perform its courtship rituals. Dense forest, tall grass meadows, or dry scrubland fail to meet these ecological and behavioural needs. Roadside meadows and old logged areas are suitable and subject to slow colonization. Moderately grazed pastures are also suitable and support large populations.

Even within suitable habitat, the grasshopper’s low vagility (the ease with which it can spread) limits its distribution. This poor ability to spread is the result of complex social behaviour, rather than an inability to fly well. Females are rather sedentary, at least in mountain areas, while males make mainly short, spontaneous flights within a limited area. The two sexes together form tightly knit population clusters within areas of suitable habitat. Visual and acoustic communication displays hold the cluster together.

Ring ouzel

A mix of ecology and history may explain the biogeography of most species. The ring ouzel or ‘mountain blackbird’, which goes by the undignified scientific name of Turdus torquatus (Box 1.1), lives in the cool temperate climatic zone, and in the alpine equivalent to the cool temperate zone on mountains (Figure 1.1). It likes cold climates. During the last ice age, the heart of its range was probably the Alps and Balkans. From here, it spread outwards into much of Europe, which was then colder than now. With climatic warming during the last 10,000 years, the ring ouzel has left much of its former range, surviving only in places that are still relatively cold because of their high latitude or altitude. Even though it likes cold conditions, most ring ouzels migrate to less severe climates during winter. The north European populations move to the Mediterranean while the alpine populations move to lower altitudes.

Figure 1.1 The breeding distribution of the ring ouzel (T. torquatus).

Sources: Map adapted from Cramp (1988); picture from Saunders (1889)

BOX 1.1 WHAT’S IN A NAME? CLASSIFYING ORGANISMS

Everyone knows that living things come in a glorious diversity of shapes and sizes. It is apparent even to a casual observer that organisms appear to fall into groups according to the similarities between them. No one is likely to mistake a bird for a beetle, or a daisy for a hippopotamus. Zoologists and botanists classify organisms according to the similarities and differences between them. Currently, five great kingdoms are recognized – prokaryotae (monera), protoctista, plantae, fungi, and animalia. These chief subdivisions of the kingdoms are phyla. Each phylum represents a basic body plan that is quite distinct from other body plans. This is why it is fairly easy, with a little practice, to identify the phylum to which an unidentified organism belongs. Amazingly, new phyla are still being discovered (e.g. Funch and Kristensen 1995).

Organisms are classified hierarchically. Individuals are grouped into species, species into genera, genera into families, and so forth. Each species, genus, family, and higher-order formal group of organisms is called a taxon (plural taxa). Each level in the hierarchy is a taxonomic category. The following list shows the classification of the ring ouzel:

Kingdom:	Animalia (animals)
Phylum:	Chordata (chordates)
Subphylum:	Vertebrata (vertebrates)
Class:	Aves (birds)
Subclass:	Neornithes (‘new birds’)
Superorder:	Carinatae (typical flying birds)
Order:	Passeriformes (perching birds)
Suborder:	Oscines (song birds)
Family:	Muscicapidae (thrush family)
Subfamily:	Turdinae (thrushes, robins, and chats)
Genus:	Turdus
Species: Turdus torquatus	Turdus torquatus

Animal family names always end in -idae, and subfamilies in -inae. Dropping the initial capital letter and using -ids as an ending, as in felids for members of the cat family, gives them less formal names. Plant family names end in -aceae or -ae. The genus (plural genera) is the first term of a binomial: genus plus species, as in Turdus torquatus. It is always capitalized and in italics. The species is the second term of a binomial. It is not capitalized in animal species, and is not normally capitalized in plant species, but is always italicized in both cases. The specific name signifies either the person who first described it, as in Muntiacus reevesi, Reeve’s muntjac deer, or else some distinguishing feature of the species, as in Calluna vulgaris, the common (= vulgar) heather. If subspecies are recognized, they are denoted by the third term of a trinomial. For example, the common jay in western Europe is Garrulus glandarius glandarius, which would usually be shortened to Garrulus g. glandarius. The Japanese subspecies is Garrulus glandarius japonicus. In formal scientific writing, the author or authority of the name is indicated. So, the badger’s full scientific name is Meles meles L., the L. indicating that Carolus Linnaeus (1707–78) first described the species. The brown hare’s formal name is Lepus europaeus Pallas, which shows that Peter Simon Pallas first described it (in 1778). In this book, the authorities will be omitted because they confer a stuffy feel. After its first appearance in each chapter, the species name is abbreviated by reducing the generic term to a single capital letter. Thus, Meles meles becomes M. meles.

HISTORY

Historical-cum-geographical explanations for the distribution of organisms involve two basic ideas, both of which are the subject of historical biogeography. The first idea concerns centres-of-origin and dispersal from one place to another. It argues that species originate in a particular place and then spread to other parts of the globe, if they should be able and willing to do so. The second idea considers the importance of geological and climatic changes splitting a single population into two or more isolated groups. This idea is known as vicariance biogeography. The following case studies illustrate these two basic biogeographical processes.

Tapirs

The tapirs are close relatives of the horses and rhinoceroses. They form a family – the Tapiridae. There are four living species, one of which dwells in southeast Asia and three in central and South America (Plate 1.1). Their present distribution is thus broken and poses a problem for biogeographers. How do such closely related species come to live in geographically distant parts of the world? Finds of fossil tapirs help to answer this puzzle. Members of the tapir family were once far more widely distributed than at present (Figure 1.2). They lived in North America and Eurasia. The oldest fossils come from Europe. A logical conclusion is that the tapirs evolved in Europe, which was their centre-of-origin, and then dispersed east and west. The tapirs that went northeast reached North America and South America. The tapirs that chose a southeasterly dispersal route moved into southeast Asia. Subsequently, probably owing to climatic change, the tapirs in North America and the Eurasian homeland went extinct. The survivors at the tropical edges of the distribution spawned the present species. This explanation is plausible, but it is not watertight – it is always possible that somebody will dig up even older tapir remains from somewhere else. The incompleteness of the fossil record dogs historical biogeographers and dictates that they can never be fully confident about any hypothesis.

Plate 1.1 Central American or Baird’s tapir (Tapirus bairdi), Belize.

Photograph by Pat Morris.

Figure 1.2 Tapirs: their origin, spread, and present distribution.

Source: Adapted from Rodríguez de la Fuente (1975)

Nestor parrots

The nestor parrots (Nestorinae) are endemic to New Zealand. There are two species – the kaka (Nestor meridionalis) and the kea (N. notabilis) (Plate 1.2). They are closely related and are probably descended from a ‘proto-kaka’ that reached New Zealand during the Tertiary period (see Appendix). Then, New Zealand was a single, forest-covered island. The proto-kaka became adapted to forest life. Late in the Tertiary period, the northern and southern parts of New Zealand split. North Island remained forested and the proto-kakas there continued to survive as forest parrots, feeding exclusively on vegetable matter and nesting in tree hollows. They eventually evolved into the modern kakas.

Plate 1.2 Nestor parrots. (a) Kaka (N. meridionalis). (b) Kea (N. notabilis).

Photographs by Pat Morris.

South Island gradually lost its forests because mountains grew and climate changed. The proto-kakas living on South Island adjusted to these changes by becoming ‘mountain parrots’, depending on alpine shrubs, insects, and even carrion for food. They forsook trees as breeding sites and turned to rock fissures. The changes in the South Island proto-kakas were so far-reaching that they became a new species – the kea. After the Ice Age, climatic amelioration promoted some reforestation of South Island. The kak...