Which of the following is the study of the geographic distribution of species on earth?

Biogeography is a biological as well as a geographical discipline. Biologists prefer a more historical view and underline the importance of the evolution of species and communities. Geographers accentuate more the ecological background of the distribution of plants and animals, including the manyfold influences of man, and they underline the importance of scales in time and space. Both try to understand the distribution of patterns of organisms and biocenosis. Usually, biogeography is subdivided into historical, ecological, and regional biogeography. More recently, environmental problems led to a great variety of topics—e.g., forest dieback, air and water pollution, desertification, degradation of rainforests—which are treated in applied biogeography.

I Introduction

Biogeography is the study of the patterns of geographic distribution of organisms and the factors that determine those patterns. This discipline plays a critical role in our understanding of marine mammal evolution and adaptation (Berta et al., 2006). Although marine mammals are very mobile, and there is an apparent lack of physical barriers in the world ocean, only Orcinus orca, Physeter macrocephalus, and perhaps some of the balaenopterids could arguably be considered to have cosmopolitan distributions. Other species have restricted distributions (e.g., coastal South America, Indo-West Pacific), reflecting their ecological requirements and their geographic centers of origin. Because related species tend to have similar ecological requirements and dispersal abilities, the distribution of higher taxa can also show distinct tendencies and restrictions, which reflect the cumulative distributions of their included species. For example, while delphinids, river dolphins, and sirenians have their highest diversity in tropical latitudes, most pinniped, ziphiid, and phocoenid species occur in temperate and polar regions. From a geographic perspective, specific regions can thus be characterized as centers of diversity for these higher taxa, and past global changes in the environment will have influenced their evolutionary history. For example, cooling of the world climates during the Tertiary may have contributed to the radiation of the cold-water adapted pinnipeds and mysticetes.

1 Introduction

Biogeography is “the study of the distribution of organisms over the earth and of the principles that govern these[sic] distribution’’ (King, Stansfield, & Mulligan, 2006).

The coconut has a pantropical distribution. It is basically a strand plant. It extends also to lowland subtropics in the areas that receive 1000–1500 mm of distributed precipitation annually. Interestingly, and broadly stated, the distribution range of the coconut matches that of the tribe Cocoseae, and subtribe Attaleinae to which it belongs (Fig. 6.1). The natural habitats of these three entities, however, differ according to their respective ecological preferences.

Presently, Almost the entire coconuts that we find throughout the world is cultivated. However, there are still some isolated pockets and several islands where it occurs in natural strands in the lowland coastlands and in much of the thousands of islands of the Indian and Pacific Oceans. This is evident from paleobotanical and paleopalynological evidences. For instance, naturally occurring forms of coconut were present as a component of the natural vegetation in the Cook Islands—and possibly even as far as the Society Islands—from the western Pacific Ocean, long before the present-day humans reached there (Bellwood, 2013; Kirch, 2000).

Dransfield et al. (2008; GP II) have given meta-accounts of the distribution and ecology of the family Arecaceae up to its tribes, genera, and species. Palms broadly occur throughout the tropics and subtropics of the world. Tropical rain forests and tropical islands of the Old World constitute their natural habitats. At the same time, some palms also occur in seasonal and semiarid and moderately cool habitats (e.g., cerrado of central Brazil), and rarely, in desert locations where groundwater is available, and at high latitudes; e.g., at 44° N in Mediterranean France, 44° S in the Chatham Islands, east of New Zealand (Dransfield et al., 2008). Some authors have observed that the family’s latitudinal extremes are largely limited by those of subfamily Coryphoideae and tribe Cocoseae.

The Arecaceae now include 183 genera and c. 2400 species (2588 species in 188 genera per Palmweb, accessed February 25, 2016). Malesia (Sumatra, Malay Peninsula, Philippines to New Guinea, and the Solomon Islands) has the largest concentration of palms (50 genera, c. 992 species). When tropical Asia is included within Malesia, the diversity expands to 57 genera and c. 1200 species (Dransfield et al., 2008). They attribute this to prolific speciation in island archipelagoes and the admixing of Northern and Southern Hemisphere floras in this region due their coming together at the eastern and western ends of Malesia during the latter half of the Tertiary (Tertiary, 66–5 Mya). A fair level of climatic stability during this period facilitated this process. In palm diversity, Malesia is followed by the Neotropics (65 genera, c. 130 species). Numerous tribes of the subfamily Arecoideae dominate here, including the tribe Cocoseae (Dransfield et al., 2008). Henderson, Galeano, and Bernal (1995) had pointed out that just three Arecoid genera, Chameodorea, Geonoma, and Bactris, account for one-third of the palm diversity in the Neotropics. The western Indian Ocean islands (including Madagascar) is another region rich in palm diversity (25 genera, 192 species) (Dransfield et al., 2008).

II Ecology and History Determine Distribution

Beyond descriptive aspects of biogeography, there are distinct factors that determine a given species’ distribution. In some cases, distribution is limited because a species may not be adapted for living in certain environments. For example, tropical delphinids may not range into higher latitudes due to limitations on their abilities to thermoregulate in colder water or find food in different habitats. But competition may also be a factor. Throughout most of its range, the West Indian manatee (Trichechus manatus) occurs in both coastal and riverine habitats. However, it does not range into the Amazon River, where the exclusively freshwater Amazon manatee (T. inunguis) occurs, although it occupies the coastal areas on either side of the river mouth. Here, the two species are parapatric, and competitive exclusion is likely at work (Marsh et al., 2011).

The dispersal abilities of organisms may partly explain why species occur in some areas and not in others. For example, the lack of otariids in the North Atlantic is probably not due to the lack of suitable habitat, but rather lies in the inability of North Pacific or South Atlantic species to get there. Of course, one could also tie this into their ecological requirements, in that dispersal to the North Atlantic would be more likely if North Pacific species ranged far enough north for animals to disperse via the Arctic Ocean across northern North America or Eurasia. For some species that have widely separated allopatric populations (e.g., Commerson’s dolphin, Cephalorhynchus commersonii), dispersal from one region to the other is a likely explanation for their distribution. In other cases, vicariance events can explain allopatric distributions (Nelson and Rosen, 1981; Wiley, 1998). For example, the two subspecies of Indian River dolphin (Platanista gangetica) occur in different river systems, the Indus and Ganges–Brahmaputra River systems. But these rivers used to be connected, and therefore the geographic separation of the populations is from a rather recent vicariance event.

Large-scale changes in the environment can have dramatic influences on species distributions. In times of global cooling, cold boundary currents in the ocean basins extended farther toward the equator. This, in turn, enabled temperate species to disperse across the equator to similar habitats in a different hemisphere, giving rise to antitropical species, such as dusky dolphins (Lagenorhynchus obscurus) in the Southern Hemisphere and the closely related Pacific white-sided dolphin (L. obliquidens) in the North Pacific (Harlin-Cognato, 2010). Among the antitropical species and species pairs, some tendencies in their distributions are apparent. Although the long-finned pilot whale (Globicephala melas), has only been recorded live from the North Atlantic and the Southern Hemisphere, more than 1000-year-old skulls of this species have been unearthed in Japan, and it was probably hunted to extinction (Whaling, Japanese, this volume). For the rest of the seven or so recognized antitropical species and species pairs, all except the bottlenose whale Hyperoodon (which also occurs in the North Atlantic) have their northern members limited to the North Pacific. Perhaps the oceanographic and climatic conditions that allow transequatorial dispersal for temperate species occur more frequently or become more developed in the Pacific basin than in the Atlantic. The right whales (Balaena spp.) present a slightly different scenario, but one that is consistent with this pattern. Now recognized as three distinct species, molecular analyses indicate that the species in the North Pacific (B. japonica) and Southern Ocean (B. australis) are more closely related to each other than either is to the North Atlantic species (B. glacialis), suggesting a more recent transequatorial dispersal in the Pacific basin, possibly due to collective behavior during the right ecological conditions (Berdahl et al., 2016). The above comparisons do not include the latitudinal migrant species, such as many of the species of balaenopterids. For these, their seasonal occurrence at low latitudes greatly facilitates transequatorial dispersal and would not likely require any significant change in oceanographic or climatic conditions.

Latitudinal migrants do, however, present questions regarding the selective advantage to conducting such extensive movements—sometimes covering thousands of miles (e.g., gray whales, Eschrichtius robustus and humpback whales, Megaptera novaeangliae). Their occurrence at high latitudes can be explained by the greater abundance of food, but the selective advantage to their seasonal movements to less productive wintering areas is not as apparent. The fact that they occur in high latitudes in the winter season with some regularity means that escape from winter cold may not be a major factor for adults. Calving in warmer climates does make sense, and mating during the same season could lead to wholesale movements of a population. An alternative explanation is that they leave high latitudes in the winter to escape from killer whales, which occur in much higher densities in these areas (Corkeron and Connor, 1999).

Beyond consideration of the underlying mechanisms of a single species’ distribution, it is possible to make inferences about the origins of entire ecological communities. One approach is known as vicariance biogeography (Nelson and Rosen, 1981; Wiley, 1988). Vicariance biogeographers look for congruence between the phylogenetic relationships among species and their geographical distributions. Species distributions can be superimposed on phylogenetic trees to create what are called area cladograms (Fig. 1). If the area cladograms of several unrelated but geographically similar higher taxa are congruent, it is good evidence that a specific sequence of vicariance events operated on all of those taxa as speciation mechanisms. Furthermore, it may allow the researcher to make inferences about the centers of origin for the higher taxa being considered (see also Myers and Giller, 1988).

If possible, one should try to incorporate the fossil and geologic record when inferring historical mechanisms in biogeography, especially among distantly related taxa (Thewissen, 2014). A case in point can be seen in the river dolphins. Among the river dolphins, Inia and Pontoporia appear to be closest relatives among the extant species, the former occupying several South American rivers that flow into the Atlantic, and the latter occurring along the Atlantic coast of South America. However, the closest relative of this pair is probably Lipotes, which was found in the Yangtze River in China until its recent probable extinction (Turvey et al., 2007). It is likely that geologic change in river flows (to the Pacific Ocean) and nearshore habitats in especially South America contributed to these relationships.

In a recent context, human activities have played and are playing a role in altering species distributions, most often in the form of range reduction. For example, hunting may have played some role in the extirpation of gray whales (Eschrichtius robustus) from the North Atlantic. More indirect, but just as dramatic, will be the shifts or reductions in species’ distributions due to climate change, especially in high latitudes.

C Island biogeography

Ecologists have been intrigued at least since the time of Hooker (1847, 1853, 1860) by the presence of related organisms on widely separated oceanic islands. Darwin (1859) and Wallace (1911) later interpreted this phenomenon as evidence of natural selection and speciation of isolated populations following separation or colonization from distant population sources. Simberloff (1969), Simberloff and Wilson (1969), and Wilson and Simberloff (1969) found that many arthropod species were capable of rapid colonization of experimentally defaunated islands. Although the theory of island biogeography originally was developed to explain the patterns of equilibrium species richness among oceanic islands (MacArthur and Wilson, 1967), the same factors and processes that govern colonization of oceanic islands explain rates of species colonization and metapopulation dynamics (see Section II.B) among isolated landscape patches, especially in montane landscapes (Cronin, 2003; Hanski and Simberloff, 1997; Leisnham and Jamieson, 2002; Simberloff, 1974; Soulé and Simberloff, 1986). Critics of this approach have argued that oceanic islands clearly are surrounded by habitat unsuitable for terrestrial species, whereas terrestrial patches may be surrounded by relatively more suitable patches. Some terrestrial habitat patches may be more similar to oceanic islands than others, for example, alpine tundra on mountaintops may represent substantially isolated habitats (Leisnham and Jamieson, 2002) as do isolated wetlands in a terrestrial matrix (Batzer and Wissinger, 1996), whereas disturbed patches in grassland may be less distinct (but see Cronin, 2003). A second issue concerns the extent to which the isolated populations constitute distinct species or metapopulations of a single species (Hanski and Simberloff, 1997). The resolution of this issue depends on the degree of heterogeneity and isolation among landscape patches and genetic drift among isolated populations over time.

2.3 Island Biogeography

Ecologists have been intrigued at least since the time of Hooker (1847, 1853, 1860)Hooker, 1847Hooker, 1853Hooker, 1860 by the presence of related organisms on widely separated oceanic islands. Darwin (1859) and A. Wallace (1911) later interpreted this phenomenon as evidence of natural selection and speciation of isolated populations following separation or colonization from distant population sources. Simberloff (1969), Simberloff and Wilson (1969), and E. Wilson and Simberloff (1969) found that many arthropod species were capable of rapid colonization of experimentally defaunated islands. Although the theory of island biogeography originally was developed to explain patterns of equilibrium species richness among oceanic islands (MacArthur and Wilson, 1967), the same factors and processes that govern colonization of oceanic islands explain rates of species colonization and metapopulation dynamics (see Section 3.2) among isolated landscape patches (Cronin, 2003; Hanski and Simberloff, 1997; Leisnham and Jamieson, 2002; Simberloff, 1974; Soulé and Simberloff, 1986). Critics of this approach have argued that oceanic islands clearly are surrounded by habitat unsuitable for terrestrial species, whereas terrestrial patches may be surrounded by relatively more suitable patches. Some terrestrial habitat patches may be more similar to oceanic islands than others, for example, alpine tundra on mountaintops may represent substantially isolated habitats (Leisnham and Jamieson, 2002), as do isolated wetlands in a terrestrial matrix (Batzer and Wissinger, 1996), whereas disturbed patches in grassland may be less distinct (but see Cronin, 2003). A second issue concerns the extent to which the isolated populations constitute distinct species or metapopulations of a single species (Hanski and Simberloff, 1997). The resolution of this issue depends on the degree of heterogeneity and isolation among landscape patches and genetic drift among isolated populations over time.

Abstract

Vicariance biogeography emerged in the late 1970s from distinct traditions in historical biogeography: the phylogenetic systematics and the panbiogeography. Vicariance biogeography, in the strict sense, is the study of repeated patterns of disjunct distributions within many members of a biota that may be explained by vicariance (or splitting of areas). Since its origin to the 1990s, it became the most important method or discipline within historical biogeography, involving the study of life and Earth history using cladistic methods (cladistic biogeography). In fact, nowadays both names (vicariance and cladistic biogeography) are frequently treated as synonyms. Vicariance biogeography became a very important method to classify areas of endemism on a global, regional, and local scale in terms of their historical relationships. Since the late 1990s this method or discipline has been in disuse because of many inherent problems when there is not congruence between geography and the phylogenetic tree of the species (ie, sympatric speciation, species extinction or dispersal). The development of molecular phylogenetics and its approaches to infer ancestral areas and times of diversification has displaced the use of cladistics biogeography and/or vicariance biogeography.

Abstract

Microbial biogeography is a rapidly developing subfield of biogeography that aims to describe the distribution of microorganisms across space and time. Recent advances in molecular genetic methodologies have enabled the extension of biogeography to microbes, revealing that the ecological and evolutionary processes shaping microbial geographic distributions are in some ways similar to those of larger animals and plants. However, contemporary environmental factors tend to be primarily responsible for driving biogeographic variation in microbial communities, with the relative importance of dispersal remaining a matter of debate. Here we review the evidence and underlying mechanisms for microbial biogeography as well as discuss the current limitations and potential applications of this emerging field.

Island Biogeography

Biogeography is a scientific approach to understanding the distribution and abundance of living things, the biota, on our planet. Island biogeographers are primarily interested in isolated areas and the study of fragmented life zones and their relation to the biota. But what living things or biota are included? Nearly all groups are studied: plants, birds, insects, other animals, humans, fungi, fishes, disease organisms, and so on. From this list it is clear that biogeography is not a single discipline. Instead, it is a unifying principle for scientists of different disciplines. The unifying principle is their interest in the distribution and abundance of the organisms with which they have a greater familiarity. Thus, botanists, ornithologists, entomologists, mamologists, mycologists, and anthropologists can all come together and be unified by their interest of biogeography.

Species Richness and Diversity

Biogeography fundamentally relies on the categorization and ordering of biodiversity into units that can be measured, compared, and contrasted. Biologists categorize and order the natural world to make meaning of biogeography. The concept of a species is the oldest, most popular, and most debated biological unit to describe biodiversity and biogeography. Since Aristotle through to the Middle Ages, the Enlightenment, and up to the present, the concept of a species has undergone countless transformations (Wilkins, 2009). In fact, an exact universal working definition is likely to never exist because of the growing number of organisms and populations that continue to defy all proposed taxonomic, reproductive, or genetic definitions. The “species problem“ is still stimulating to some, but ultimately trivial – with most fields of biology tailoring definitions for purposes of human understanding on a taxon-by-taxon case and using species or other taxonomic units when it makes sense (Ehrlich, 1997; Kelt and Brown, 2000). Unfortunately, this has been largely miscommunicated, leading to the misconception that biodiversity and species diversity are equivalents. This mishap has been described as “biology's biggest blunder” and has stunted clear understanding of the state of biodiversity and biogeography (Woodwell, 2010).

Despite the artificial difficulties with the species concept, quantifying biogeography using species as units is always the first tool ecologists turn to because of its efficiency – counting species is far faster and easier than identifying and tallying populations or piecing together interaction webs. The species concept is a particularly useful unit for countryside biogeographers who are largely interested in comparing biodiversity's responses to human influences. The first measure is usually species richness, or the number of different species in a given area, which is later followed by an index of species diversity, which incorporates species and their abundances within an area. Species richness and diversity are deployed first in countryside biogeography, but, ideally, countryside biogeography also measures biodiversity using ecosystem components that determine function.