Editing Ecology (section)

=== Biogeography ===
{{Main|Biogeography}}

Biogeography (an amalgamation of ''biology'' and ''geography'') is the comparative study of the geographic distribution of organisms and the corresponding evolution of their traits in space and time.<ref name="Parenti90"/> The ''[[Journal of Biogeography]]'' was established in 1974.<ref name="JBiog">{{cite web | title = Journal of Biogeography – Overview | publisher = Wiley | url = http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1365-2699/homepage/ProductInformation.html | access-date = 16 March 2018 | url-status=live | archive-url = https://archive.today/20130209095040/http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1365-2699/homepage/ProductInformation.html | archive-date = 9 February 2013| doi = 10.1111/(ISSN)1365-2699}}</ref> Biogeography and ecology share many of their disciplinary roots. For example, [[Island biogeography|the theory of island biogeography]], published by the Robert MacArthur and [[Edward O. Wilson]] in 1967<ref name="MacArthur67" /> is considered one of the fundamentals of ecological theory.<ref name="Wiens04"/>

Biogeography has a long history in the natural sciences concerning the spatial distribution of plants and animals. Ecology and evolution provide the explanatory context for biogeographical studies.<ref name="Parenti90" /> Biogeographical patterns result from ecological processes that influence range distributions, such as [[Animal migration|migration]] and [[Biological dispersal|dispersal]].<ref name="Wiens04" /> and from historical processes that split populations or species into different areas. The biogeographic processes that result in the natural splitting of species explain much of the modern distribution of the Earth's biota. The splitting of lineages in a species is called [[Allopatric speciation|vicariance biogeography]] and it is a sub-discipline of biogeography.<ref name="Morrone95"/> There are also practical applications in the field of biogeography concerning ecological systems and processes. For example, the range and distribution of biodiversity and invasive species responding to climate change is a serious concern and active area of research in the context of [[global warming]].<ref name="Svennin08" /><ref name="Landhäusser09"/>

==== r/K selection theory ====
{{Main|r/K selection theory}}

A population ecology concept is r/K selection theory,{{Cref2|D}} one of the first predictive models in ecology used to explain [[Life history theory|life-history evolution]]. The premise behind the r/K selection model is that natural selection pressures change according to [[population densities|population density]]. For example, when an island is first colonized, density of individuals is low. The initial increase in population size is not limited by competition, leaving an abundance of available [[Resource (biology)|resources]] for rapid population growth. These early phases of [[population growth]] experience ''density-independent'' forces of natural selection, which is called ''r''-selection. As the population becomes more crowded, it approaches the island's carrying capacity, thus forcing individuals to compete more heavily for fewer available resources. Under crowded conditions, the population experiences density-dependent forces of natural selection, called ''K''-selection.<ref name="Reznick02"/>

In the ''r/K''-selection model, the first variable ''r'' is the intrinsic rate of natural increase in population size and the second variable ''K'' is the carrying capacity of a population.<ref name="Begon05" /> Different species evolve different life-history strategies spanning a continuum between these two selective forces. An ''r''-selected species is one that has high birth rates, low levels of parental investment, and high rates of mortality before individuals reach maturity. Evolution favours high rates of [[fecundity]] in ''r''-selected species. Many kinds of insects and [[invasive species]] exhibit ''r''-selected [[Phenotypic trait|characteristics]]. In contrast, a ''K''-selected species has low rates of fecundity, high levels of parental investment in the young, and low rates of mortality as individuals mature. Humans and elephants are examples of species exhibiting ''K''-selected characteristics, including longevity and efficiency in the conversion of more resources into fewer offspring.<ref name="MacArthur67"/><ref name="Pianka72"/>