Tag: biogeography

Forgotten but not gone

Forgotten Grasslands of the South. Natural History and Conservation by Reed F. Noss. Island Press 2013

Walden Warming by Richard Primack. University of Chicago Press 2014

Reading Noss’s work, I recall Faulkner’s words, “The past isn’t gone. It isn’t even past.” Forgotten, neglected, tragically diminished, but not gone. Noss describes his travels to visit what was once a vast archipelago of grass-dominated ecological communities, ranging from endless longleaf pine savannas (see my post on Looking for Longleaf) to tiny rock outcrop barrens. This island landscape stretched across the southeastern United States from Texas to Virginia. In fact, though Noss does not discuss them, these communities are found up into the mid-Atlantic and New England. Today, the remaining islands, in a sea of agriculture, industrial forestry and urbanization  only hint at what has vanished beneath the waves of “progress.” But remarkably, there is enough to form the core of a restored landscape, something that will be a major challenge for 21st century ecologists.

Many types of habitats fit under the term “grassland.” Woodlands have trees, but their crowns cover less than three-fourths of the ground, allowing herbaceous plants, especially grasses, to thrive. Savannas have scattered trees, with less than about fifty percent cover. Meadows, glades, barrens and balds have only isolated patches of trees. Noss also describes plant and animal species endemic to the southeastern grasslands. An endemic is a kind of organism found in a particular type of community or a local area, and nowhere else. Many of these are critically imperiled, occurring today at only one or two places. The book is illustrated with his photos of the communities and the rare plants.

Noss has really interesting things to say about the factors that have maintained open, grass-dominated habitats over ecological and evolutionary time. The main ecological question is: what is preventing tall woody plants from taking over? The climate is warm enough, and rainfall is adequate for trees. It could be lack of a deep, firm soil that roots can penetrate to support tall stems. It could be that the soil stays wet or dry too much of the year. It could be constant disturbance by flood, wind, fire or herbivores. It could be lack of sufficient nutrients to support trees and shrubs. At any particular site, it’s most likely a combination of two or more of these factors.

The evolutionary question is: how have the species that comprise these ecological communities arisen and survived in a dynamic landscape? The answers are tentative and complicated, especially those related to changing climate. The distinctiveness and diversity of the endemic species, especially their adaptations to fire, imply a long evolutionary history. Some of the endemic plant species, such as those in certain rock outcrop barrens, may have evolved recently, while others, like the ones in the longleaf pine savannas, have been around for a very long time. This field of research is called phylogeography because it looks both at phylogenetic (evolutionary) relations among different populations and species and at the geographic patterns of climate (and so, the species’ habitats) now and in the past.

Many authors have stated the grasslands originated only as a result of disturbance by humans, who do not seem to have reached America before 30,000 years ago at the very earliest. If the grasslands originated before the Pleistocene ice ages, how did they survive the periods of peak glaciation and cold? Noss cites pollen data to show that most of the southeast had a cool temperate climate during the ice ages, but evidence from geomorphology suggests that there were periods of boreal conditions with deep seasonal frost or even permafrost. Aeolian landforms, created by strong winds coming off the glaciers, include dune fields, sand sheets and the famous Carolina bays. These indicate that there were periods where there was little vegetation to stabilize the surface. One possibility is that the pollen record is incomplete, because the intervals without vegetation produce essentially no pollen. Another is that, if the Gulf Stream stopped during the coldest intervals, the Gulf of Mexico would have been a tremendous heat reservoir, keeping the coastal areas warm, while inland sites were cold. On maps of the ice age drop in sea level, the additional dry land, just on the west side of peninsular Florida, looks nearly as large as North Carolina. Thus, a lot of grassland species might have retreated there.

Noss’s book and a recent article (Noss, R. F., Platt, W. J., Sorrie, B. A., Weakley, A. S., Means, D. B., Costanza, J. and Peet, R. K. 2015. How global biodiversity hotspots may go unrecognized: lessons from the North American Coastal Plain. Diversity and Distributions 21: 236–244), which includes the coastal plain up to Cape Cod, call the region a biodiversity hotspot. This is based on the great numbers of plant, vertebrate and insect species in the region and the number of those species that are endemic to it.

The article calls for the North American Coastal Plain to be listed as a global biodiversity hotspot. A colleague who studies southern grasshoppers told me that the group behind the effort to achieve listing had several more papers in the pipeline that they expected would be needed to convince the Critical Ecosystem Partnership Fund to add the NACP as hotspot number 36 They succeeded on the first try, just after the article was published (http://www.cepf.net/news/top_stories/Pages/Announcing-the-Worlds-36th-Biodiversity-Hotspot.aspx) Hooray!

Now the hard work begins: convincing people, especially government officials and private conservation groups, to take action. Here in New Jersey, most conservationists still see the coastal plain as a forest region. Natural enough, since fire suppression for the last eighty years has effectively converted what were once woodlands and savannas into dense forests of pine and oak trees and huckleberry shrubs. “Forest,” has such cultural significance in American environmentalism that it is very difficult to convince anyone that this is not what Nature intends. Add modifiers like “old growth,” “pristine,” “climax,” and you have idols that it is very hard to get environmentalists to stop worshipping.

Most people I know in the Mid-Atlantic region tend to blame “development” for loss of natural habitats. To an extent, this is true for the grasslands of the South, especially the loss in recent times of the smaller glades and barrens, but other factors are historically more important. Noss mentioned drainage and conversion to farmland, but this applies mainly to the wetter, richer grasslands. Dense tree plantations have replaced pine savannas. Another factor is loss of large herbivores, beginning with the extinction of much of North America’s megafauna – mammoths, ground sloths, etc. – around 15,000 years ago. To some degree, cattle, hogs and sheep may have supplied their place in the early post-1492 times of open ranges and even today, but livestock can do more harm than good to natural habitats, and they will never be allowed to recreate the vast network of “buffalo traces,” leading to salt licks and waterholes. These trails provided habitat and dispersal routes for grassland plants, as roadsides do today, if we don’t mow them in the growing season or allow exotic invasives to take over.

By far the clearest factor reducing grasslands is fire suppression. Since the advent of motorized firefighting in the mid-twentieth century, the number of fires has changed little, but the area burned annually has greatly decreased (https://www.jstor.org/stable/2484334?seq=1#page_scan_tab_contents). This means that fire return intervals have generally become too long to prevent establishment of closed forest canopies. This is fine if you want to grow trees for wood or fiber but terrible for the plants and animals of woodlands, savannas and grasslands.

I have tried for years to convince my friends in the New Jersey Pine Barrens that the greatly increased plant canopy cover since fire suppression began to be effective has caused much of the reported drying out of the landscape. They prefer to blame the loss of wetlands and headwater streams on wells drilled by farmers, developers and casinos sucking water out of the ground. Trees and shrubs are taking just as much water through their roots and evaporating it through leaves, 300-500 pounds of water for every pound of sugar they make in photosynthesis. Some of my conservationist friends and colleagues oppose even moderate thinning of trees in the Pine Barrens. They talk about endangered species’ need for undisturbed habitat, not recognizing that on the coastal plain, far more species are threatened by the loss of open land with herbaceous vegetation – grasslands, woodlands, savannas and meadows. A very experienced botanist I know, however, has become convinced, after seeing species like pine barrens gentian and turkey beard springing up in the wake of forest thinning and reintroduction of fire on managed lands. Too bad the New Jersey Forest Service officials still thinks Smoky the Bear has the last word. They are courting disaster as fuel loads continue to build up in the pines, but they won’t believe that a fire could occur that they could not control. This is incredibly short sighted.

I also wish our environmental community would back off its opposition to natural gas pipelines, which actually create open habitats, and devote more of their resources to stopping the motorized mayhem that’s destroying the last of our native savannas and sand ridge communities all across southern New Jersey. In the Pinelands National Reserve, motorized recreation is not a permitted land use, but pressure from the motorheads has prevented meaningful regulation or enforcement.

Besides these immediate threats, I wonder whether the coastal plain biodiversity hotspot can survive climate change. As shown by Richard Primack in his excellent book, Walden Warming (Chicago 2014) there are already substantial changes in the flora and fauna of New England since Thoreau kept a naturalist’s journal in the 1850’s. Surely, though we lack clear evidence, such changes are occurring in the North American Coastal Plain. For plant populations to persist, they must either acclimate (adjust their flowering and fruiting physiology) adapt locally (through natural selection of individuals that best match the warmer climate) or disperse their seeds northwards. Primack points out that the barriers created by towns, farms and highways make it difficult for native plants to disperse to suitable new habitat.

A look at the map of the coastal plain shows another problem: the northward narrowing of the geologic region, until it peters out at Cape Cod and in the sandy outwash plans of southern New England. Even if species can shift northwards, they will find themselves funneled into increasingly tight confines, reduced even more by sea level rise. Europe’s flora is impoverished compared to its temperate counterparts in North America and Asia, because southward dispersal during the height of the last ice ages ran into the barrier of the Alps. The coastal plain’s denizens may be similarly crushed against the rock ribs of New England.

Noss’s points out that many people feel that preserving nature for its own sake is as important as preserving it for its benefits to us. He recasts Jack Kennedy’s famous dictum as, “ask not just what nature can do for us, but also what we can do for nature.” He estimates that temperate grasslands have the lowest ratio of lands preserved to lands destroyed of any major ecological system on earth. In the North American Coastal Plain this ratio may be even lower, although perhaps with more prospect for restoration than in some areas, because so much has been lost to fire suppression, which is fixable.

Noss is a strong proponent of saving all that we can in whatever ways are effective. He is against any form of ” triage,” writing off of species and communities that we decide in advance can’t be saved. He also criticizes the Nature Conservancy for overemphasizing what they call “working landscapes,” and neglecting the smaller, uneconomical bits, those tiny glades, barrens and rock outcrops that house such amazing numbers of endemic taxa. Noss argues we need to practice preservation on many scales, beginning with a ban on development of any new natural lands. We should be redeveloping abandoned or underutilized sites, close to existing development. I agree, but we need to find some way to effectively transfer development rights, or landowners will block any such policy. He also argues that we need to change the policies and practices of our state and federal agencies and private conservation groups to better manage lands already protected. Too many of the best areas are either over-utilized or neglected.

Both these books are excellent reads, especially the authors’ descriptions of work in the field with their colleagues and collaborators. One gets a sense that there are a lot of very dedicated ecologists working to preserve biodiversity in our changing landscape and changing climate. One of the encouraging developments I have noticed is the great increase in contributions from what are now called, “citizen scientists.” People, who might once have pursued their love of plants, birds or butterflies in isolation, now contribute to both current data collection and preservation of valuable old data (Thoreau’s Journals are a prime example) through projects like iDigBio. More could be done, especially if there were a way to report and then evaluate outliers: unusual sightings, anomalous individuals and things in the wrong place at the wrong time. Where economic interests are involved, we do usually follow up, as with introduced pests, but otherwise many valuable observations in our rapidly changing environment may be written off as misidentifications or just lost. I would like to see more naturalist’s, especially our large crop of butterfly watchers learn when and how to collect proper specimens to verify their unexpected sightings. Scientific collecting is almost never a threat to populations of insects, and a specimen allows positive identification and preservation of a record in a way photographs can’t.

I would strongly recommend these two books to anyone concerned about the future of biodiversity along our Atlantic coast.

Naturalists Abroad: Three on the Amazon

Hemming, John. 2015. Naturalists in Paradise: Wallace, Bates and Spruce in the Amazon. Thames & Hudson. [I read the Kindle edition]

There was not a lot paradisiacal about the Amazon basin when three young, lower middle class Englishmen arrived there in the late 1840’s. It was a backwater of the Empire of Brazil, still recovering from a bloody civil war and not yet experiencing the rubber boom. Travel was difficult, often impossible, and living conditions ranged from merely hot and humid to nearly intolerable. No motorboats, no canned food, no bug repellents. Yet the three naturalists, the first from Great Britain to travel extensively and for many years in the Amazon region, could live cheaply and enjoyed the help of both Brazilian and foreign residents. They lived by the sale of the specimens they collected, something not commonly done today, at least by academic scientists, but then it was quite respectable. This was possible, in Henry Walter Bates and Alfred Russel Wallace’s case, because they had a reliable and energetic agent in London, Samuel Stevens, who marketed the exotic animals and plants they supplied to an eager and growing circle of collectors. Thomas Spruce enjoyed the support of George Bentham and William Hooker, director of Kew Gardens. They also accumulated personal collections of great value and volumes of notes, drawings, sketches, and accounts of the rivers, forests and the native peoples, of whose languages and cultures they learned much, to their great advantage, and ours. They relied on the skill of native boatmen and hunters, and procuring their services was a constant preoccupation for all three.

They generally worked alone, each going his own way and following different styles of exploration. Bates was mainly an entomologist and the most sedentary, working intensively in one area for months at a time. Wallace and Spruce ranged more widely, Wallace after birds and all other animals, as well as plants. He also accumulated extensive geological and ethnographic information. Spruce hunted new species of plants, including his favorites, mosses and liverworts. Wallace was accompanied at times by his brother, but Bates and Spruce were out of contact with their own countrymen for long periods.

The adventures described in this account are exciting, inspiring, and frequently hair-raising. The rivers and their falls and rapids were the greatest danger to the explorers and their precious collections, but the everyday toll of hunger and sickness on the men and of wet, mold and insects on their specimens probably did the most damage. Wallace’s brother died of yellow fever before he could return to England. All three had malaria, sometimes very severe, and in 1858 Spruce suffered an unexplained illness that left him crippled for life.

Catastrophe dogged Wallace: heading home in 1852, a shipboard fire destroyed almost all his personal specimens and records, except for the few he managed to grab as he abandoned ship. Still he went on to a successful voyage to the Malay Archipelago (modern Indonesia) during which he worked out the theory of natural selection, which he and Darwin jointly announced in 1858. In the second half of the 1850s, Spruce pushed far into the Andes, where he learned much about the hallucinogenic plants used by the natives, a topic later investigated by Richard Schultes and Wade Davis. He also made vital collections of Chinchona, the source of the antimalarial quinine, contributing to the establishment of plantations in India and the East Indies. He did this despite the hardships of the country, a civil war and his own prostration by that mysterious illness.

Hemming’s account is consistently lively and an excellent companion to reading the naturalists’ own work, like Bates’s wonderful Naturalist on the River Amazons. It has the advantage of weaving their travels together and providing the background of Brazilian history and the development of natural science in Great Britain. Hemming is an anthropologist, historian and geographer, whose own extensive travels in the region add much to the story.

The work accomplished by these three men in their time in the field was phenomenal: thousands of new species of animals and plants along with detailed descriptions of a country largely unknown to the learned world. They are deservedly members of the pantheon of the greatest naturalists in history.

Fearful scimitars

Sabertooth by Mauricio Anton (2013) Bloomington. Indiana University Press. 243 pp.

This is the natural history of an ecological niche: an ambush predator that captures prey by a throw and pin, with powerful forelimbs and a long, strong back, followed by a bite to the neck, using greatly elongated canine teeth, made possible by jaw adaptations that permit a huge gape and a long, strong neck. The bite results in bleed out and death of the victim. It is argued that this leads to quicker and safer kills than the suffocation method employed by modern big cats on large prey. The author does a remarkable job of tracing the paleontology of successive groups of species that have occupied this role since the Permian, although there seem to have been no dinosaurs that did so.

The illustrations of fossils, reconstructed animals and landscapes are beautifully done, in loving detail. The painstaking anatomical analyses to show how these killing machines worked are clear and persuasive, at least to a non-expert. There are interesting accounts of the constantly changing nomenclature of the fossils.

It would be useful to see similar accounts of modern large cats, hyaenids and other carnivores to get a sense of how the sabertooths fit into the big picture of carnivore evolution and why it is they went extinct instead of the others.

The extinction happened several times, as the successive groups of sabretooths disappeared, and they were not quickly replaced. Sometimes millions of years seem to have elapsed before a new lineage appeared to fill the niche. Indeed, sometimes there were no large felids of any kind for extended periods, if we can trust the fossil record. At other times, a new group may have out-competed the current occupants of the sabertooth niche. One might say that there is room at the top of the food web, but it is a precarious position that isn’t always filled.

Perhaps the most recent occupants of the niche went extinct with the megafauna of the old and new worlds, but could they have been done in by more efficient pantherids? Was their technique only suitable for very specific types of prey that got replaced by more wary and evasive herbivores or did vegetation change doom their hunting methods? Did their very specialized anatomy and techniques simply run out of room for improvement against ever more challenging prey? Anton thinks that their very specialized niche may have left them relatively more vulnerable to shifts in prey abundance. This would be a major factor in the late Pleistocene, along with competition from lions and humans, among others. As the least flexible group, they may have been the first to go.

Does it mean there’s an unoccupied niche now, or are those habitats and resources simply gone?

What other convergences in form and behavior has natural selection produced across time and biogeographic realms? We all know at least a few ecological equivalents, like pangolins and armadillos, or moles, marsupial moles and mole crickets. There’s an interesting one involving modern beetles’ and early rodents’ mandibles, but it isn’t clear what the functional significance is (John Acorn in American Entomologist, Summer 2014, p 128). Thanks to Mauricio Anton for presenting this story so beautifully.

Image: Smilodon fatalis – National Park Service

Ecosystem lost and found?

Looking for Longleaf. The Fall and Rise of an American Forest by Lawrence S. Earley (2004) Chapel Hill. University of North Carolina Press. 322pp.

When I was a teenager, my grandfather recalled for me how the longleaf pine forests in eastern North Carolina looked when he was young, some seventy to eighty years before. It was like being in a cathedral, he said, with the trunks of the trees like columns and the forest floor clear as far as you could see. This book gives an introduction to the character and extent of the longleaf pine ecosystem, once dominant over a vast region of the Atlantic and Gulf Coastal Plain, introducing the plant, Pinus palustris, the diversity of associated plants (sometimes hundreds of species in a square kilometer and as many as 40-60 in a square meter) and several of the more distinctive animals, like gopher tortoise and red-cockaded woodpecker.

Earley explains the critical role of fire and soil in establishing the diversity of types within the overall longleaf ecosystem.

The middle part of the book is a historical account of the European encounter with the forest, its exploitation by the naval stores industry and its eventual destruction by that industry and the railroad based loggers. Some of these descriptions fit closely with what I heard from my grandfather and from a friend in North Carolina (whom Earley interviewed for the section on turpentining). He talks about rafting logs down the coastal rivers (as my grandfather, born in 1869, did as a boy) and shipping naval stores (my grandfather also described how the cooper made the barrels for turpentine). He explains that what preserved so much of the forest were the limitation of cutting timber to areas close to usable streams, that is until the railroads came. My father (born 1913) recalled how the railroad was brought in to log some of the most remore and inaccessible places when he was growing up. Some time around 1970, before the railroad was finally abandoned, I saw carloads of longleaf pine stumps waiting to be hauled off to extract the valuable resins or to make fatwood kindling, sold by L.L. Bean, among others. Earley also mentions the continued interest in salvaging sunken logs and getting lumber from old buildings.

The final chapters are on the development of forest management ideas, from failed attempts at replanting to replacement by loblolly and slash pine and the gradual development of methods to regenerate longleaf, first as even aged stands but now moving towards uneven age management and overall ecosystem restoration. Red-cockaded woodpecker played a key role in several changes in policy, driven by court decisions under the Endangered Species Act. Many of the agencies involved, like the US forest Service have serious problems dealing with the steady increase in scientific and ecological understanding of the forests. Institutional change is difficult, especially when institutional memory is impaired by frequent reassignment of key people and political pressures. The US Forest Service has had an especially hard time admitting it has been wrong about fire suppression and even-aged management.

He talks about the role of national and state forests and of large and small private landholders (currently there is increasing longleaf acgeage on federal and maybe state land and on large private conservation holdings, but continued losses on timber company lands and small private holdings) and what the trends may mean for the future of the ecosystem and many of its species. New incentives under the Conservation Reserve Program may be changing the minds of some private owners. It is possible to derive a pretty steady income from restored longleaf, partly through sale of raked needles in the 10th to 15th years after replanting. Poles are much in demand, using middle aged trees. The author seems most impressed by adaptive management approaches using small group-selection cuts and frequent growing season fire. Several interesting examples are described in the next to last chapter on restoration. Some of these areas sound like they would be worth seeing, and there are some groups that can help with restoration, a topic that is on my mind lately, as I and my brothers and sisters still hold a small remnant of thousands of acres of longleaf land owned by my great-great grandfather in the early 1800s. We will soon be clearing the stand of loblolly pine, planted decades ago, to make way for longleaf again.

Neotropical travellers

Essay on the Geography of Plants, by Alexander von Humboldt, and Aimee Bonpland. 2009 (1807). Edited by Stephen Jackson. Translated by Sylvie Romanowski. University of Chicago Press. Chicago. 274 pp with tableau in pocket
This book is pure descriptive natural history, with almost no speculation or discussion of causes. It is divided into Humboldt’s Essay of some 30 or 40 pages and the longer Tableau Physique prepared by Humboldt and Bonpland. Some of Von Humboldt’s fascinations, like barometric pressure, which he includes along with temperature, humidity and “electrical tension” as factors influencing plant distribution, seem peculiar to me, but I have to remember that he was much more limited in what he could measure than we are today. Another peculiarity is his notion of “social” plants, by which he seems to mean those that form dense monocultures as opposed to mixed stands. He says these live “in organized society, like ants and bees…” His examples include mangroves, Cladonia lichens and pines, but also Vaccinium. He notes that such plants are more common in the temperate regions than in the tropics. Mexico is an exception, harboring many temperate species, like pine, oak and sweet gum, which he attributes in part to the vast geographical expanse of the northern part of America, narrowing southwards. Somehow this causes Mexico to be colder than similar latitudes elsewhere. Then there is his idea of “subterranean vegetation,” which seems to mean fungi in caves and mines. He treats these “cryptograms,” alongside lichens and mosses. How aware was he of the fundamental distinction between autotrophs and heterotrophs? Photosynthesis was barely beginning to be understood in his time.
He also lacked a clear notion of geologic time, referring only to remote ages, but with no sense of the scope and significance of the fossil record. Only the epoch of human spread across the earth is accessible to his reflections on the distribution of plants. When compared to Graham’s Natural History of the New World, he has far less to go on, and barely any sense of the potential of fossils to shed light on modern plant communities and their distributions. Yet Graham clearly is following in the footsteps of von Humboldt and Bonpland.
One advance he makes is to point out the importance of physiognomy alongside taxonomy in describing communities of plants (another of his ideas) what we today commonly call life forms or growth forms.
The main thing, though, is the Tableau Physique, the profile of the Andes, using the volcano Chimborazo thought, at the time, to be the highest peak in the world. The detailed data packed into a single illustration is startling and quite beautiful. The other wonderful part is his concluding reflections in the essay on the value of natural history writing and artwork in elevating and liberating our understanding, even if we cannot experience these amazing places directly.

New world history

A Natural History of the New World. Ecology and Evolution of Plants in the Americas, by Alan Graham. 2011. Chicago. University of Chicago Press. 387 pp.
This is an ecological and evolutionary story acted on the stage of two continents from the close of the Mesozoic to the recent. South America starts out isolated or nearly so, while North America begins joined to Eurasia across the proto-Atlantic. It ends with two continents joined by a narrow isthmus and a sporadic connection to Siberia across the Bering Sea. During this time as the Americas override the Pacific plates, a series of great mountain ranges form along the western edges of both continents, altering the directions of rivers and radically altering the climate of the continental interiors. Late in the period, the shift towards glacial climates turns what were temperate climates under a polar insolation regime into boreal forest and tundra, with deciduous forests to the south and new dry ecosystems in the arid west.
It is a dramatic story, with a shifting cast of characters, most impressively the higher angiosperms and the radiating mammals responding to each other as well as struggling among themselves to dominate under the shifting conditions. The rise of groups like the grasses and the ungulates with their associated carnivores are among the most visible and dramatic developments, if not quantitatively as significant as the insects and fungi, which changed much less over the same time. This is a vexed question; megafauna and keystone species enthusiasts on the side of top-down regulation and ecosystem engineering, those of us who look at energy flux and nutrient cycles as keys to ecological processes and who see microbes as the dominant force, alongside plants, on the bottom-up side. Probably both views are right some of the time. No doubt, though, that climate and geology – lithosphere, atmosphere, hydrosphere – are the ultimate regulators, although the biosphere’s impact on carbon cycling is also significant.
This is a very detailed book, giving an account of dozens of types of communities both in the past and the present vegetation of the Americas. It also describes the phases of development step by step, tracking the geologic changes and the shifting vegetation as revealed by pollen and macro fossils. The author is a noted paleobotanist at the Missouri Botanic Garden. There are good photos, maps and graphs of changing temperatures over the epoch. Truly a history of nature.
Graham also has excellent chapters on the techniques of paleoclimate reconstruction and the collection and interpretation of fossils. The text is also a wonderful travelogue, full of historical and prehistorical anecdotes, and covering the modern biogeography of the new world as well as the story of how it came to be as it is.