Many terrestrial species occupied southern refugia during glaciations and recolonized northern areas during interglacials. Ice-free refugia persisted within the Arctic proper; species occupying these refugia diverged in isolation, promoting Arctic diversification.
The most significant Arctic refugium was Beringia and adjacent parts of Siberia. Pleistocene glaciations also resulted in a series of extinction and immigration events in the Arctic Ocean. During interglacials, marine species immigrated mainly though the Arctic gateways from the Pacific and Atlantic Oceans, a process that continues today. Throughout the Pleistocene, Arctic species responded to climatic cycles by shifting their distributions, becoming extirpated or extinct, persisting in glacial refugia, and evolving in situ.
Although the last 10, years have been characterized by climatic stability, the Earth has now entered a period of rapid anthropogenic climate change that is amplified in the Arctic.
Generalism and high vagility typical of many Arctic species impart resilience in the face of climate change. However, additional anthropogenic stressors including human habitation, overharvest, industrial and agricultural activities, contaminants, altered food webs and the introduction of invasive species pose new challenges.
The consequences of current warming for Arctic biodiversity are therefore not readily predicted from past periods of climate change. In general, species richness is lower in the Arctic than in more southerly regions Fig. The strength and slope of latitudinal biodiversity gradients differ between regions and are more pronounced in terrestrial and marine systems than in freshwater environments, and, in general, most pronounced in organisms with greater body mass and those occupying higher trophic levels Hillebrand With the recent development of global distributional and phylogenetic datasets, however, it has become apparent that the pattern is much more complex than previously assumed Jetz et al.
A number of hypotheses have been advanced to explain the latitudinal trend of biodiversity, although no consensus exists for a mechanistic explanation Currie et al. Hypotheses may be grouped into those based on ecological mechanisms of species co-occurrence, evolutionary mechanisms governing rates of diversification, and earth history Mittlebach et al.
Until recently, ecological hypotheses have dominated the discussion, but with the development of large DNA-based phylogenies there is now more focus on understanding the underlying historical processes. The hypotheses proposed to date are not necessarily mutually exclusive, and observed patterns are likely the result of complex interactions between various biotic and abiotic factors.
The importance of niches for the maintenance of species diversity. Nature , — McKane, R. Resource-based niches provide a basis for plant species diversity and dominance in arctic tundra.
Nature , 68—71 Millennium Ecosystem Assessment Packer, A. Soil pathogens and spatial patterns of seedling mortality in a temperature tree. The Hardy-Weinberg Principle. Evolution Introduction. Life History Evolution. Mutations Are the Raw Materials of Evolution. Speciation: The Origin of New Species. Avian Egg Coloration and Visual Ecology. The Ecology of Avian Brood Parasitism. The Maintenance of Species Diversity. Neutral Theory of Species Diversity. Population Genomics.
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Evidence for Meat-Eating by Early Humans. Resource Partitioning and Why It Matters. The Evolution of Aging. Citation: Levine, J. Nature Education Knowledge 3 10 Earth is home to an astonishing diversity of species that provide food, medicine and other infrastructure necessary for the existence of humankind. Given intense competition between species for limited resources, how is this diversity maintained? Ecologists have shown that differences in how species interact with their environment counter the inevitable loss of biodiversity that occurs when better competitors overrun their inferior counterparts.
Aa Aa Aa. Figure 1: The diversity of species. A Tropical rainforests can contain 1, tree species in the area of fifteen city blocks. Figure 2: Competitive exclusion and coexistence. A Differences between species in their competitive ability drive the superior to dominance and the inferior to exclusion. Figure 3: Niche differences ecologists have used innovative field observations and manipulations to quantify niche differences between species.
A Ecologists studying arctic tundra have used chemical tracers to show that different plant species consume different forms of nitrogen glycine versus ammonium versus nitrate McKane et al. References and Recommended Reading Adler, P.
Gause, G. The struggle for existence. Article History Close. Share Cancel. Revoke Cancel. Scientists have known for more than a century that species diversity increases towards the equator. Think tropical rainforests -- which house two thirds of the world's species -- teeming with buzzing insects, screeching birds and howling monkeys, versus the frigid tundra, where life is largely limited to scattered trees and only a few dozen kinds of mammals, such as caribou and foxes.
Numerous hypotheses have been proposed to explain this pattern. One idea is that tropical regions harbor greater biodiversity because they are especially fertile grounds for the formation of new species -- i. The team was surprised to find that while the number of bird and mammal species increases closer to the equator, the number of genetically distinct groups within each species -- known as subspecies -- is greater in the harsher environments typical of higher latitudes.
Animals in these environments are more likely to freeze during cold winters or die during usually hot summers. The results are consistent with a study by researchers at the University of British Columbia suggesting that -- contrary to conventional wisdom -- species arise faster in temperate zones than in the tropics.
Comparing biodiversity in the temperate zones with that in the tropics is like comparing the coins in your pocket with the coins in your piggy bank, he added. Food-crop diversity and pollinating insects and bats allow agriculture to support our populations; when disease strikes a food crop, only diversity can save the system from collapse. Plant and animal diversity provide building blocks for medicine, both current and potential; almost half of the pharmaceuticals used in the United States today are manufactured using natural compounds, many of which cannot be synthesized.
They also provide critical industrial products used to build our homes and businesses, from wood and rubber to the fuels that underpin our economies — even coal and oil are the products of ancient plant matter and preserved zooplankton remains. Biodiversity plays a central mythic and symbolic role in our language, religion, literature, art, and music, making it a key component of human culture with benefits to society that have not been quantified but are clearly vast.
From our earliest prehistory, people have never lived in a world with low biodiversity. We've always been dependent on a varied and rich natural environment for both our physical survival and our psychological and spiritual health.
As extinctions multiply, and cannot be undone, we tread further and further into unexplored terrain — a journey from which there is no return. Get the latest on our work for biodiversity and learn how to help in our free weekly e-newsletter. Tax ID: Join now. Your support is key in our work protecting species and their habitat.
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