We find that high levels of biodiversity in the Eastern Arc Mountains are the result of pre-Quaternary speciation processes and environmental stability. Sel viisil saab kindlaks määrata värvikoordinaadid hoone interjööri erinevatele aspektidele.
PLoS One. Published online Nov Copyright © Dimitrov et al This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited. This article has been cited by other articles in PMC.
Abstract We combine information about the evolutionary history and distributional patterns of the genus Saintpaulia H. We find that high levels of biodiversity in the Eastern Arc Mountains are the result of pre-Quaternary speciation processes and environmental stability.
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Our results support the hypothesis that climatically stable mountaintops may have acted as climatic refugia for lowland lineages during the Pleistocene by preventing extinctions. In addition, we found evidence for the existence of lowland micro-refugia during the Pleistocene, which may explain the high species diversity of East African coastal forests. We discuss the conservation implications of the results in the context of future climate change. Introduction The processes that have led to the accumulation of species in hotspots of biological diversity continue to be elusive .
For tropical mountains, two different scenarios have been proposed: Pleistocene glacial refugia  —  and the long-term stability .
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The refugia model suggests that differences in species diversity between refugia are the result of allopatric speciation and a reduced level of extinctions due to reduced climatic fluctuations within refugia. New species resulting from this process should also have allopatric distributions, which in the context of tropical mountains implies that different species should be present on different mountain blocks.
Stability, in contrast, reduces extinction rates within an area and permits survival of relictual lineages; thus species richness is not a result of extinctions outside of stable areas. Meanwhile, stability does not preclude sympatric speciation of radiating groups within these areas.
We explore these hypotheses using the biodiversity hotspot in the Eastern Arc Mountains of Tanzania and Kenya and focus on the genus Saintpaulia H. The discovery of extensive numbers of endemics with regional distribution seems to support the long-term stability model.
Furthermore, data from sediment cores from the Uluguru Mountains provides evidence that highland forest composition has remained stable for at least the last years which might suggest similarly stable conditions across the earlier glacial-interglacial cycles during the Pleistocene. Commercial Black Mountain System results are in concordance with previous findings from sedimentary cores from the larger East African region see also .
Emerging evidence that local climatic conditions in the eastern Arc have been stable during periods of past global climatic changes provides a possible explanation for the extremely rich biota and numerous endemic species found in the region e. Much of the tree species diversity in East African forests has been linked to vicariance due to the pan-African tropical forest fragmentation initiated during the Oligocene-Early Miocene . A similar pattern has been reported for amphibians  and in both cases lack of diversification during Pleistocene climate oscillations Commercial Black Mountain System been attributed to the stable conditions on mountain tops.
Likewise, much of the bird diversity in the Eastern Arc stems from speciation events predating the Pleistocene and is consistent with repeated vicariance and dispersal events Valikute raamatud Trading Reddit expanding and contracting forests, which supports a model of long-term stability in the face of climatic fluctuations .
In some cases differentiation among populations was attributed to fluctuations in forest extent during the Pleistocene, and — in concordance with the stability hypothesis — new lineages formed on the periphery of stable areas. A better understanding of the biogeographic histories of Eastern Arc lineages is essential to explain how present diversity has been formed and maintained in this biodiversity hotspot over the recent geological time frame, and in the context of past climatic fluctuations.
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The Eastern Arc endemic plant genus Saintpaulia provides an ideal model to study the effects of ecosystem dynamics at high and low altitude on the diversity and distribution of tropical forest species in the Eastern Arc.
A highland ancestry has been proposed for this genus  ; however, due to the lack of a calibrated phylogeny, the Commercial Black Mountain System of divergences among lineages could not be assessed.
Burtt  —  recognized a total of 20 species of Saintpaulia as well as four varieties, but species delimitations have been questioned in two molecular studies . A recent revision of the genus reduced the number of species to six all endemic to the Eastern Arc Mountains and coastal forests of Tanzania and Kenya.
Two new species from the Uluguru Mountains, Tanzania, were recently described  elevating the number of species to eight. Most species of Saintpaulia are restricted to montane forests on a single mountain block, although S. Burtt occurs on two and S. Only Saintpaulia ionantha H. Saintpaulia has already attracted attention due to its high degree of endemism and commercial importance several thousand cultivars originating from a few specimens of wild S.
Here we use historical biogeographical data for Saintpaulia in conjunction with distributional and environmental data to further our understanding Magento 2 kohandatud aktsia varud the role of past environmental variations on current diversity patterns in the region and the possible impacts of future changes of climate and habitats.
Here we adhere to the Saintpaulia classification proposed by Darbyshire  including the species from Haston et al. In particular cases where species determinations are uncertain we also refer to the original label information.
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We attempted to maximize the representation of Saintpaulia lineages using sequences from specimens of this genus present in public data repositories e. Data were available for five of the currently recognized species with the exceptions of S. Burtt, a very rare species with a very limited distribution in the highlands of the Uluguru Mountains, and the two species described by Haston et al.
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As outgroup we used Streptocarpus caulescens Vatke. The genus Streptocarpus Lindl. Gesneriaceae has been hypothesized as the closest relative to Saintpaulia  Commercial Black Mountain System has been used to root the Saintpaulia phylogeny in previous studies e.
There are few published molecular datasets of Saintpaulia and they rely on different genetic markers.
Möller and Cronk  used ITS sequences to study the relationships and biogeography of 17 Saintpaulia species of the 20 species recognized at that time cultivated in the research collection at the Royal Botanic Garden, Edinburg. Lindqvist and Albert  used 5S non-transcribed spacer 5S-NTS of all but one of the species then included in the genus.
More recently Caro et al.
Few additional data are available e. Among these datasets, the study of Lindqvist and Albert  includes the largest number of Saintpaulia lineages.
In addition, the recent taxonomic changes and the use of different voucher specimens in the various studies make it impossible to combine these datasets. For these reasons we have selected the Lindqvist and Albert  data for our analyses, with the addition of sequences of 5S-NTS from the Möller et al. Additional ITS data from Möller et al. Accession numbers for all sequences used in the present analyses that are not available through the aforementioned link are presented in Table 1.
Table 1 Accession numbers of Saintpaulia sequences used in the analyses and specimen vouchers accession numbers and depositories. GenBank accession.