نتایج جستجو برای: speciation
تعداد نتایج: 14852 فیلتر نتایج به سال:
Comparative phylogeography of oceanic archipelagos: Hotspots for inferences of evolutionary process.
Remote island archipelagos offer superb opportunities to study the evolution of community assembly because of their relatively young and simple communities where speciation contributes to the origin and evolution of community structure. There is great potential for common phylogeographic patterns among remote archipelagos that originate through hotspot volcanism, particularly when the islands f...
In this article, we explore the large-scale structure of the tree of life by using a simple model with a constant number of species and rates of speciation that equal the rates of extinction. In addition, we discuss the consequences of horizontal gene transfer for the concept of a most recent common ancestor of all living organisms (cenancestor). A simple null hypothesis based on coalescence th...
the mobility and bioavailability of trace elements in the agricultural soils are extremely important in assessing the risk of toxicity to the growing plants. a five step sequential extraction procedure (sep) has been employed to study the speciation of as, sb, cr, cu, cd, pb, zn, ni, fe and mn in 18 soil samples neighboring an industrial complex in isfahan, central iran. enrichment factor (ef) ...
landfill leachates and leachate sediments were investigated in order to survey the discharge of uranium (u) from municipal solid waste (msw) landfills and municipal solid waste incinerator (mswi) bottom ash landfills. concentrations of u in the leachates were as high as or higher than concentrations of cd, a metal more often discussed when considering the environmental effects of landfill leach...
Assessing the extent to which population subdivision during cladogenesis is necessary for long-term phenotypic evolution is of fundamental importance in a broad range of biological disciplines. Differentiating cladogenesis from anagenesis, defined as evolution within a species, has generally been hampered by dating precision, insufficient fossil data, and difficulties in establishing a direct l...
In contrast with speciation in terrestrial organisms, marine plankton frequently display gradual morphological change without lineage division (e.g., phyletic gradualism or gradual evolution), which has raised the possibility that a different mode of evolution dominates within pelagic environments. Here, we reexamine a classic case of putative gradual evolution within the Globorotalia plesiotum...
The latitudinal diversity gradient has been hypothesized to reflect past evolutionary dynamics driven by climatic niche conservation during cladogenesis, i.e. the tropical conservatism hypothesis. Here we show that the species diversity of treefrogs (Hylidae) across the western hemisphere is actually independent of evolutionary niche dynamics. We evaluated three key predictions of the tropical ...
Late Pliocene and Pleistocene climatic instability has been invoked to explain the buildup of Neotropical biodiversity, although other theories date Neotropical diversification to earlier periods. If these climatic fluctuations drove Neotropical diversification, then a large proportion of species should date to this period and faunas should exhibit accelerated rates of speciation. However, the ...
A characteristic signature of adaptive radiation is a slowing of the rate of speciation toward the present. On the basis of molecular phylogenies, studies of single clades have frequently found evidence for a slowdown in diversification rate and have interpreted this as evidence for density dependent speciation. However, we demonstrated via simulation that large clades are expected to show stro...
Three properties of bifurcating branching diagrams that are used for representing a specific number of taxa are (1) the number of possible arrangements, (2) the number of possible topologies, and (3) the probabilities of formation according to particular models of cladogenesis. Of these, the probabilities have received the least attention in the literature. Indeed, many biologists would be asto...
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