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A large-scale analysis of bird diversity and evolution on mountains around the globe explores the relationships between elevation, species richness and the rate of formation of new species.
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(niobium nitride) is cubic (Fig.1). This means
that the crystallo graphic symmetry of their
devices is broken at the interface between the
cubic superconductor and the hexagonal semi-
conductor. Such broken symmetries can cause
unwanted effects at interfaces, and therefore
in devices.
This is where the orientation of the super-
conductor comes into play. Yan etal. grew
a layer of the cubic superconductor on a
substrate so that its lattice was oriented in a
way that makes it look hexagonal. To picture
this, imagine looking at a dice at an angle in
which the diagonally opposite corners are
aligned. What you see is a hexagon, even
though the dice is cubic.
The same is true of the cubic superconductor
on the substrate: a hexagonal arrangement of
atoms is exposed on the surface, and the hexa-
gonal semiconductor (aluminium nitride)
aligns with this when it forms on top of the
superconductor. As a result, the aluminium
nitride is not perturbed by broken crystallo-
graphic symmetry at the interface, and forms
an undistorted layer, as needed for the growth
of an HEMT structure. Indeed, the authors
observed the formation of certain quantum
oscillations in their device; the presence of
these oscillations is considered a benchmark
of high crystal quality.
Yan et al. went on to measure the current–
voltage profile of their superconductor–HEMT
structure. They observed that this profile of the
HEMT is modified by a superconductor-to-
metal transition in niobium nitride, and gen-
erates a negative differential resistance (NDR)
— a property that can be used to increase the
power of electrical signals. NDR devices have
been known since the end of the nineteenth
and include the Gunn diode
, which is
widely used to generate microwaves in sensors
and measuring instruments. Such devices are
of great value for electronic systems that use
high-frequency, high-power signals— exactly
what is needed in telecommunications net-
works. In Yan and colleagues’ device, NDR can
be switched on or off simply by making the
temperature lower or higher than the critical
temperature for superconductivity (the temper-
ature below which superconductivity occurs).
Combining materials that have different
electronic properties without breaking the
crystallographic symmetry at the interface is a
remarkable feat. However, t he mobility of elec-
trons in the device is currently rather low; much
higher mobilities can be achieved in devices
that use indium arsenide. Achieving mobili-
ties comparable to those of indium arsenide
will be extremely challenging. More over, the
separation between the superconductor and
the 2D electron gas — free electrons that are
confined to move in only two dimensions —
generated in the device will need to be reduced
to enable promising quantum effects.
A future goal could be to use the authors
system to generate and observe Majorana
— a type of quasiparticle that would
be useful for quantum computing — at the
superconductor–semiconductor interface11.
Charge carriers in electronic devices can be scat-
tered (for example, by crystal defects), and the
average time between scattering events needs to
be long to stabilize these quasiparticles. Yan et al.
calculate that the charge-carrier scattering time
in their devices is impressively long (66femto-
seconds; 1fs is 10
s), but the scattering times
will need to be at least 100times longer, simi-
lar to the scattering time in indium arsenide
to stabilize Majorana fermions. It remains to
be seen whether this can be achieved in the
authors’ device s.
Ultimately, Yan and colleagues’ work will
inspire and accelerate efforts to grow nitride
superconductors and nitride semiconductors
that enable the ultra-high operating efficiency,
structural perfection and opportunities for
manipulating electronic properties that have
already been achieved in interfaces involving
indium arsenide. Because, at the end of the day,
the interface is the device.
Yoshiharu Krockenb erger and Yoshitaka
Taniyasu are in the Materials Science
Laboratory, NTT Basic Research Laboratories,
Atsugi, Kanagawa 243-0198, Japan.
1. Yan, R. et al. Nature 555, 183–189 (2018).
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5. Senapati, K., Blamire, M. G. & Barber, Z. H. Nature
Mater. 10, 849–852 (2011).
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Mountains of diversity
A large-scale analysis of bird diversity and evolution on mountains around the
globe explores the relationships between elevation, species richness and the rate
of formation of new species. S L .246
ountain chains are global centres of
biological diversity — they harbour
one-third of all terrestrial species1.
These places have long fascinated biologists2,
but are notoriously difficult to explore and
study. Our knowledge of the distribution
of species diversity on mountains is incom-
plete, as is our understanding of how species
richness (the total number of species) and the
rates of formation of new species (speciation)
vary in single mountain ranges. On page246,
Quintero and Jetz
tackle these issues by study-
ing the diversity and evolution of birds on the
46 major mountain ranges of the world.
Mountains can differ substantially in the
environment they provide, depending on
factors such as bedrock, ruggedness, climatic
conditions and the amount of energy available
in the region. Moreover, mountains are often
far apart, and organisms inhabiting such places
can persist in genetically isolated populations
owing to factors including terrain complexity
and the high variation of habitat types along
elevational gradients. Isolated populations
often adapt to the local environmental and
ecological conditions. When such populations
are no longer capable of reproducing with one
another, they form new species
. One example
of this is the hummingbird Aglaiocercus kingii,
which is found only in the Andes of South
America (Fig.1).
Quintero and Jetz used large-scale data
sets of current distributions of bird species,
mined from existing databases and publica-
tions, to characterize the relationship between
elevation above sea level and species richness.
The authors amalgamated data for 9,993 spe-
cies, representing essentially all the birds that
are currently known. Although the patterns
observed in different regions vary, the overall
trend for most regions is a hump-shaped curve
in which species richness is highest at middle
elevations, and decreases as elevation increases.
The result confirms findings from previous
studies of plants and birds5,6. This type of
pattern might be driven by the smaller area
available for speciation at higher elevations and
because the environmental conditions there
are more extreme than those on lowlands.
For example, large temperature fluctuations
between day and night, and an increased expo-
sure to radiation and wind at higher elevations
could limit the number of species that can cope
with such conditions.
The authors used some innovative
approaches for their data analysis. They aimed
8 MARCH 2018 | VOL 555 | NATURE | 173
to capture the 3D structure of biodiversity data
by combining elevation and species infor-
mation. They performed their analyses by
grouping the bird data into ‘sliced sections
corresponding to trapezoidal prisms that
encompass a particular elevation range. This
allowed them to assess mountain complexity in
a way that improves on conventional ecological
methods that often neglect elevation.
Some biodiversity analyses can be affected
by issues such as the mid-domain effect, in
which a species-richness peak occurs around
the centre of a region because of the spatial
overlap of species’ ranges7. The authors devel-
oped a subsampling approach that offers a way
to address this issue. They counted species, but
also factored in the total area that each species
occupies when determining species’ contri-
butions to species richness. This method also
uses a complex randomization procedure that
takes a modelling approach to estimate the
species’ metrics.
Their analysis using this subsampling
approach revealed the surprising result that
there is a linear decrease in species richness
as elevation increases. Nevertheless, one con-
cern is that the subsampled species-richness
estimates from this method may not be directly
comparable with estimates of species richness
calculated in the conventional way — as the
total number of species. In addition, the size of
each species’ range might be a factor linked to
its evolutionary history, and therefore relevant
for understanding the evolution of mountain
species. Additional research might be needed
to assess the applicability of this subsampled
diversity metric.
Another, perhaps even more interesting
finding made by Quintero and Jetz concerns
the process underlying the observed species
diversity patterns. The authors used previously
estimated8 information on the evolutionary
relationships between the bird species that
they studied to calculate the rate of speciation
along elevational gradients. They found that
this rate is inversely related to subsampled spe-
cies richness: that is, species are formed at the
highest rates where the species richness is low-
est, which corresponds to mountaintops. The
authors’ explanation for this is that environ-
mentally stable lowlands have high diversity,
whereas at higher elevations, diversity is
governed mainly by frequent immigrations
and rapid species replacement during periods
of climate change.
A major limitation for studies of biological
diversity on mountains is the scarcity of availa-
ble data. Quintero and Jetz’s study uses existing
diversity data that have a resolution of at least
110kilometres horizontally and 500metres
in elevation. This kind of scale can be rather
coarse for many mountains, given that envi-
ronmental and ecological conditions can vary
considerably over distances of just a few hun-
dred metres. Although birds are the best geo-
graphically documented group of organisms
on Earth, with more than 564million publicly
available records (see, it might
come as a surprise that their diversity in many
mountains remains poorly documented.
Unfortunately, the geological data of most
relevance to biologists are lacking. Quintero
and Jetz therefore had to simplify geological
complexity in their analyses by using aver-
aged values for key variables, such as the age
of mountains. These factors, together with
ecological interactions between species, might
influence the speciation process
, and can vary
in a single mountain range.
Speciation rates are also difficult to estimate,
especially over long timescales and for groups,
such as birds, that lack a rich fossil record.
One potential drawback of the new study is
that many relationships between species, and
their estimated time of origin, have been cal-
culated on the basis of limited genetic informa-
tion and with methods that do not take into
account the difficulties that sometimes arise
during the generation of phylogenetic trees. In
some cases, proposed relationships might rely
only on comparisons of bird shape and form
(morphology) rather than on genetic data.
There is still a long way to go before the
phylogeny of birds is fully understood
. Large-
scale initiatives are under way to sequence
the genomes of all bird species as a way to
determine more-reliable estimates of the rela-
tionships between birds and to improve under-
standing of their evolutionary history11.
Quintero and Jetzs results reveal general and
unexpected relationships between elevation,
species richness and diversification. Addi-
tional data collection in the field by scientists
and birdwatchers will be essential and, along
with data integration and analysis of the sort
spearheaded by Quintero and Jetz, should pro-
vide additional insights. It will be particularly
interesting to see whether the trends reported
by Quintero and Jetz hold true for the rest of
the world’s species, the diversity and distribu-
tion of which are poorly known even at the
global level12 — let alone along elevational
gradients on mountains.
Alexander Zizka and Alexandre Antonelli
are at the Gothenburg Global Biodiversity
Centre, SE-405 30 Gothenburg, Sweden,
and in the Department of Biological and
Environmental Sciences, University of
Gothenburg. A.A. is also at the Gothenburg
Botanical Garden and in the Department
of Organismic and Evolutionary Biology,
Harvard University, Cambridge,
1. Spehn, E. M., Rudmann-Maurer, K. & Körner, C.
Plant Ecol. Divers. 4, 301–302 (2011).
2. von Humboldt, A. & Bonpland, A. Essai sur la
Géographie des Plantes (Schoell, Cotta, 1807).
3. Quintero, I. & Jetz, W. Nature 555, 246–250 (2018).
4. Hoorn, C., Mosbrugger, V., Mulch, A. & Antonelli, A.
Nature Geosci. 6, 154 (2013).
5. Kessler, M., Herzog, S. K., Fjeldså, J. & Bach, K.
Divers. Distrib. 7, 61–77 (2001).
6. McCain, C. M. Glob. Ecol. Biogeogr. 18, 346–360
7. Colwell, R. K. & Lees, D. C. Trends Ecol. Evol. 15,
70–76 (2000).
8. Jetz, W., Thomas, G. H., Joy, J. B., Hartmann, K. &
Mooers, A. O. Nature 491, 444–448 (2012).
9. Condamine, F. L., Antonelli, A., Lagomarsino,L.P.,
Hoorn, C. & Liow, L. in Mountains, Climate,
and Biodiversity (eds Hoorn, C., Perrigo, A. &
Antonelli,A.) (Wiley, in the press).
10. Ricklefs, R. E. & Pagel, M. Nature 491, 336–337
11. Zhang, G., Jarvis, E. D. & Gilbert, M. T. P. Science
346, 1308–1309 (2014).
12. Mora, C., Tittensor, D. P., Adl, S., Simpson, A.G.B. &
Worm, B. PLoS Biol. 9, e1001127 (2011).
This article was published online on 21 February 2018.
Figure 1 | The hummingbird Aglaiocercus kingii in Ecuador. This species is confined to the Andes
mountains of South America. Quintero and Jetz3 have developed an approach for studying bird
distributions on mountains around the world that might help to address how and when biological
diversity evolved along elevational gradients.
174 | NATURE | VOL 555 | 8 MARCH 2018
... Los factores que generan esta concentración se deben a la presencia de cinturones termales (Körner et al. 2011), heterogeneidad topográfica (Ricklefs 1977, Richerson & Lum 1980, Burnett et al. 1998, Nichols et al. 1998, Badgley et al. 2017, heterogeneidad climática (Suárez-Mota et al. 2017), microclimas (Kutzbach et al. 1993, Raupach & Finnigan 1997, Lembrechts et al. 2019, diferencias en radiación solar (Bennie et al. 2008), geodiversidad (During & Willems 1984, Brooks 1987, Gray 2004, Hjort et al. 2015, Moreno et al. 2020 Santen & Linder 2020) y diferencias en elevación y pendiente (Zhirnova et al. 2020). También la geología, la heterogeneidad del relieve y la mezcla de tipos de suelo han sido correlacionados con la diversidad (Hoorn et al. 2013, Antonelli 2015, Payne et al. 2017, Zizka & Antonelli et al. 2018, Körner & Spehn 2019, Rahbek et al. 2019, Silveira et al. 2019, Perrigo et al. 2020. Por ejemplo, ciertos procesos como la disolución de la roca sedimentaria por acción del intemperismo, han generado paisajes kársticos y sustratos compuestos con un alto contenido de carbonatos de calcio como calizas, lutitas, areniscas y yesos, entre otros, que hacen heterogéneos los hábitats (Mason 1946, Clements et al. 2006, Li et al. 2013, Feng et al. 2020, factor importante para muchas especies microendémicas de plantas (Meyer et al. 1992, Sosa & De-Nova 2012, Salinas-Rodríguez et al. 2017. ...
... Por ejemplo, ciertos procesos como la disolución de la roca sedimentaria por acción del intemperismo, han generado paisajes kársticos y sustratos compuestos con un alto contenido de carbonatos de calcio como calizas, lutitas, areniscas y yesos, entre otros, que hacen heterogéneos los hábitats (Mason 1946, Clements et al. 2006, Li et al. 2013, Feng et al. 2020, factor importante para muchas especies microendémicas de plantas (Meyer et al. 1992, Sosa & De-Nova 2012, Salinas-Rodríguez et al. 2017. En este contexto, las montañas, su posición, su extensión y su historia geológica (Hoorn et al. 2013, Antonelli 2015, Zizka & Antonelli et al. 2018, Hobohm et al. 2019, Rahbek et al. 2019, Silveira et al. 2019, Perrigo et al. 2020 han tenido un impacto directo en la evolución y distribución de la biota mexicana y la diversidad de plantas vasculares podría correlacionarse también a rasgos fisiográficos (Harrison et al. 2004, Kruckeberg 2004, Clements et al. 2006, Salinas-Rodríguez et al. 2017, Rahbek et al. 2019. ...
... Heterogeneidad fisiográfica. Diversos autores señalan que la heterogeneidad topográfica favorece la biodiversidad en las montañas del mundo (Ricklefs 1977, Richerson & Lum 1980, Burnett et al. 1998, Nichols et al. 1998, Badgley et al. 2017, ya que funciona como generadora de nuevos hábitats (Hoorn et al. 2013, Antonelli 2015, Zizka & Antonelli et al. 2018, Rahbek et al. 2019, Perrigo et al. 2020) y puede propiciar la diversificación de las especies. La SMOr comprende paisajes kársticos que generan mircro hábitats (Clements et al. 2006, Li et al. 2013, Feng et al. 2020, que ha propiciado la evolución de géneros de hábitos rupícolas, como: Agave, Brahea, Dasylirion, Dioon, Echeveria, Eucnide, Eutetras, Hechtia, Mammillaria, Nolina, Pinguicula, Sedum, Tillandsia, Verbesina y Villadia, en donde además se han generado múltiples mezclas edáficas que favorecen la diversificación (Figura 5) (During & Willems 1984, Brooks 1987, Van Santen & Linder 2020, Moreno et al. 2020. ...
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Antecedentes: La Sierra Madre Oriental es una Provincia Fisiográfica ubicada en el noreste de México con características geológicas, climáticas y edáficas distintivas. La flora de esta región aún no ha sido inventariada en conjunto. Preguntas: ¿Cuál es la diversidad florística de la Provincia Fisiográfica de la Sierra Madre Oriental? ¿Cuál es la afinidad geográfica de sus géneros? Sitio y años de estudio: Provincia Fisiográfica de la Sierra Madre Oriental. El trabajo se desarrolló desde agosto del 2012 a diciembre del 2020. Métodos: Se hizo una búsqueda exhaustiva de información en diversas fuentes como herbarios, bases de datos, trabajos florísticos y monografías. Para cada especie, se registró la vegetación, afinidad geográfica del género y endemismo. Resultados: Se registran 6,981 especies de las cuales 1,542 son endémicas. Las familias más ricas en especies son Asteraceae (1,000 especies), Fabaceae (495), Cactaceae (365) y Poaceae (328). Los bosques templados registran el mayor número de especies (2,906). Querétaro fue el estado con más especies (2,803), seguido de Coahuila (2,710) y Nuevo León (2,406). La Sierra Madre Oriental comprende una mayor cantidad de especies con géneros de afinidad geográfica boreal (2,742), seguidas por especies de afinidad tropical (2,020), especies endémicas de México (1,227), cosmopolitas (803) y de los desiertos del mundo (189). Conclusiones: La Sierra Madre Oriental alberga más de la cuarta parte de la flora vascular y un 13 % de las plantas endémicas del país. Es un área que reúne géneros de diferentes afinidades geográficas en su mayoría boreales, seguidos de tropicales y endémicos.
... The same is true for elevation [46,47]. Area size and isolation have been shown to impact diversification in isolated ecosystems, such as islands and mountain tops [23,48,49]. We here consider the continental area as a measure for habitable space. ...
... This high and geologically rapid turnover is reflected in the increased species turnover (i.e. a high ratio of extinction to speciation rate). Topographic isolation has also been shown as an important driver of diversification in other isolated ecosystems, such as mountains and islands [23,48,49]. ...
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Unravelling the drivers of species diversification through geological time is of crucial importance for our understanding of long-term evolutionary processes. Numerous studies have proposed different sets of biotic and abiotic controls of speciation and extinction rates, but typically they were inferred for a single, long geological time frame. However, whether the impact of biotic and abiotic controls on diversification changes over time is poorly understood. Here, we use a large fossil dataset, a multivariate birth-death model and a comprehensive set of biotic and abiotic predictors, including a new index to quantify tectonic complexity, to estimate the drivers of diversification for European freshwater gastropods over the past 100 Myr. The effects of these factors on origination and extinction are estimated across the entire time frame as well as within sequential time windows of 20 Myr each. Our results find support for temporal heterogeneity in the factors associated with changes in diversification rates. While the factors impacting speciation and extinction rates vary considerably over time, diversity-dependence and topography are consistently important. Our study highlights that a high level of heterogeneity in diversification rates is best captured by incorporating time-varying effects of biotic and abiotic factors.
... Gaps in biodiversity knowledge are one of the biggest problems for conservation (e.g., Almeida & Mamede 2014;Giaretta et al. 2015). Therefore, it is essential to carry out floristic studies in areas that have been little studied and present environmental heterogeneity, aiming to direct the conservation efforts (Kessler 2001), besides the great relevance of understanding the origin, maintenance, distribution patterns, and processes to which biodiversity is subject (Werneck et al. 2011;Santos et al. 2014;Zizka & Antonelli 2018). ...
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Cloud forests usually occur at high-altitude sites of the Atlantic Forest in eastern Brazil, albeit scattered and fragmented along the mountain tops. In this habitat, the vegetation occurs at low-temperature conditions and is usually provided by additional water sources that arise due to the horizontal precipitation of the frequent fogs. Together with the more considerable air movement and higher luminosity, these factors are conditioning for singular floras at high elevations, mainly the vascular epiphytes, which are macro and microclimate dependent. In the mountains range at the center of the Espírito Santo state, Southeastern Brazil, some mountain tops such as Pedra Azul (PA) hold these environmental features. Here, we aimed to present the first checklist of vascular epiphytes in the Pedra Azul State Park and surroundings based on fieldwork and herbarium specimens. The checklist comprises 152 species, 65 genera, and 17 families, the main families being Orchidaceae, Bromeliaceae, and Polypodiaceae, with the main genera represented by Vriesea, Acianthera, and Peperomia. The holoepiphytes were the main category among the epiphytes, although an unusually high number of facultative epiphytes were recorded. Asplenium theciferum and Octomeria cucullata are recorded in Espírito Santo for the first time, and we confirmed the occurrence of Rhipsalis cereuscula in the state. Overall, the richness recorded in PA is amongst the highest of the Atlantic Forest cloud forests. Six species are threatened at the national level and 32 at the state level. These results support the importance of the protected area for conserving the flora; however, several species - including threatened - were only recorded in the surroundings, demonstrating that the buffer zone of the Pedra Azul State Park must be included in the management plans.
... Gen3sis could be a valuable tool for exploring iconic biodiversity patterns whose underlying mechanisms remain largely under investigation [167]. For example, although we know that mountains are hotspots of biodiversity [56,168], a causal link between mountain dynamics and biodiversity remains poorly understood [169]. Coupling gen3sis with orogenic and erosion models could shed new light on the role of mountain building and associated surface processes in the formation of biodiversity. ...
Full-text available
Understanding the origins of biodiversity has been an aspiration since the days of early naturalists. The immense complexity of ecological, evolutionary, and spatial processes, however, has made this goal elusive to this day. Computer models serve progress in many scientific fields, but in the fields of macroecology and macroevolution, eco-evolutionary models are comparatively less developed. We present a general, spatially explicit, eco-evolutionary engine with a modular implementation that enables the modeling of multiple macroecological and macroevolutionary processes and feedbacks across representative spatiotemporally dynamic landscapes. Modeled processes can include species’ abiotic tolerances, biotic interactions, dispersal, speciation, and evolution of ecological traits. Commonly observed biodiversity patterns, such as α, β, and γ diversity, species ranges, ecological traits, and phylogenies, emerge as simulations proceed. As an illustration, we examine alternative hypotheses expected to have shaped the latitudinal diversity gradient (LDG) during the Earth’s Cenozoic era. Our exploratory simulations simultaneously produce multiple realistic biodiversity patterns, such as the LDG, current species richness, and range size frequencies, as well as phylogenetic metrics. The model engine is open source and available as an R package, enabling future exploration of various landscapes and biological processes, while outputs can be linked with a variety of empirical biodiversity patterns. This work represents a key toward a numeric, interdisciplinary, and mechanistic understanding of the physical and biological processes that shape Earth’s biodiversity.
... Según estos investigadores, en las regiones montañosas se incluyen no solo picos/cumbres y laderas, también valles y estribaciones adyacentes, por lo que su diversidad y los procesos que en ellas ocurren, afectan a enclaves colindantes. Los altos niveles de riqueza y endemismos de especies en la mayoría de estas formaciones reflejan una especiación mejorada, convivencia y persistencia de linajes con distintas trayectorias evolutivas (ANTONELLI, 2015;ZIZKA & ANTONELLI, 2018;PRINGLE, 2019;RAHBEK et al., 2019b). ...
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Mountain regions, especially in tropical areas, are unusually biodiverse with an impact on the surroundings places. They host hotspots of extraordinary and puzzling species richness, especially endemisms, that in recent times have been altered by the global changes that our planet is undergoing and that some scientists have called the Anthropocene period. In relation to Humboldt’s contributions regarding these regions and tropical forests, and even in the difficulty inherent in the management of historical data and comparison with current information, with changes in the distribution of species (displacements towards the highest areas – summits – of some of them), expansion of cultivation areas at height, notable decrease in glaciers, reduction of water levels or new data on species richness/ distribution (in relation to threatening warming), his work presents an overwhelming news and a sobering alert – perhaps – belatedly heard regarding the future that awaits us.
Summary: The arid mountain Gebel Elba is situated in the south‐east corner of Egypt, nearly 15 km west of the Red Sea coast. Although this mountain is surrounded by a hyper arid desert, orographic precipitation on its northern slopes provides a climatic condition that is favourable for richer growth of Afrotropical species than any similar region in Egypt. Meanwhile, a phytosociological classification of the vegetation was lacking and information on environmental drivers were mostly unknown. Additionally, plant diversity patterns for this arid mountain had not been completely evaluated. Thus, the presented thesis aims to provide scientific data to increase the knowledge on diversity patterns and vegetation distribution in an arid mountain ecosystem (Gebel Elba). The thesis combines ecological classification and ordination analyses with ecological modelling based on different environmental parameters. This thesis presented an extensive and quantitative account of the vegetation composition and plant diversity of wadi systems on north-western slopes of Gebel Elba for the first time. The established vegetation-plot database covers the open desert and mountainous area. It contains standardised vegetation plots along elevational gradients of four wadies, i.e., Yamib, Marafai, Acow and Kansisrob. In Chapter Two, an uncommon elevation-richness pattern was described for wadi systems of Gebel Elba. The thesis also provided the first phytosociological classification of the vegetation in Gebel Elba (Chapter Three). The vegetation classification in this study contains detailed species lists. Thus, a coherent base for future work on the Afrotropical vegetation of Gebel Elba had been established and made available. Furthermore, ground truth data combined with remotely sensed information were used to produce the first model-based plant diversity maps for the arid mountain Gebel Elba (Chapter Four). The thesis focused on the Afrotropical vegetation of Egypt and filled a knowledge gap on woodlands distribution and diversity patterns in Gebel Elba region. The presented thesis indicated the high importance to conserve mountainous wadi systems of Gebel Elba especially at higher elevations. URL:
Using Lauraceae as a study case, we aimed in this article to: (i) delimit areas of endemism in the Espinhaço Range, Brazil; (ii) compare these areas of endemism with those previously delimited, as well as with the centres of endemism; (iii) evaluate the association between areas of endemism and vegetation types; and (iv) classify the areas of endemism according to the International Code of Area Nomenclature (ICAN). Based on a recent survey of 99 species from the Espinhaço Range, our dataset consisted of 34 endemic species belonging to nine genera. Following previous studies, we performed parsimony analysis of endemicity (PAE) using a grid square size of 0.5º × 0.5º. We delimited four areas of endemism of Lauraceae: (i) Antônio dos Santos, (ii) Conceição do Mato Dentro, (iii) Itambé do Mato Dentro, and (iv) Rio de Contas; and confirmed six previously delimited areas of endemism: (i) Southern MG, (ii) Southern Mountains Complex, (iii) Conceição do Mato Dentro, (iv) Diamantina Plateau, (v) Serra do Cabral, and (vi) Chapada Diamantina. The areas of endemism Conceição do Mato Dentro, Serra do Cabral, Diamantina, and Serra do Cipó were classified as subdistricts in the Diamantina Plateau district of the Southern Espinhaço province. We summarized and mapped all areas of endemism corresponding to the provinces, districts, and subdistricts that cover the Espinhaço Range. Areas of endemism and centres of endemism are contrasted. Finally, we highlight that the biogeographic studies along this mountain range should embrace higher taxa with representative species in different types of vegetation in order to enrich the majority of the endemism studies mainly concentrated on the campo rupestre. Unusual distribution patterns, diversity of vegetation types, and the presence of restricted species and monophyletic groups open up opportunities to carry out integrative studies concerning the biogeographic regionalization of the ER at multiple spatio-temporal scales.
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Mapping diversity patterns is important to clarify its causes and is essential information for conservation policies. We map the distribution of vascular epiphytes from the Southern block of the Brazilian Atlantic Forest (SBAF) to understand the main factors responsible for the richness and species turnover, as well as to generate information for the conservation of this functional group. We gathered a data set of vascular epiphytes, mapping the richness and weighted endemism using cells of 0.5° × 0.5°, and performed two Generalized Dissimilarity Models (GDM) using a filter of 18 and 54 species in cells of 5 km × 5 km to evaluate the species turnover and correlation with the climatic and topographic factors. We found four sites presenting both a high richness and endemism. A gradient of richness and species turnover between the coastal and inland regions was confirmed, as well as between the lowlands and the mountainous regions. The main predictors obtained from GDM were geographic distance, cloud cover, and temperature seasonality. The topographic heterogeneity and the resulting climate changes are responsible to enhance the richness and species turnover of vascular epiphytes in the SBAF. It is important to conserve the coastal areas and the mountainous gradients due to the high richness and strong species turnover, but also the inland areas since their composition is quite distinct from previous environments.
Mountain ranges are important centers of biodiversity around the world. This high diversity is the result of the presence of different soil types and underlying bedrock, a variety of micro-climatic regimes, high topographic heterogeneity, a heterogeneous and complex vegetation cline, and a dynamic geo-climatic history. Neotropical research on mountains has focused on the Andes, while other mountain ranges are lacking in biodiversity and biogeographic studies. However, the non-Andean mountains comprise important elements of the South American relief, are home to a substantial proportion of Neotropical species, and exhibit a complex and reticulate history of diversification of their biota. Here, we provide a brief review of the biological and biogeographical importance of the major non-Andean South American mountain ranges, discussing their role for diversification and maintenance of Neotropical biodiversity. We focus on six regions: the Serra do Mar Range, the Mantiqueira Mountains, the Espinhaço Mountains, the Northeastern Highlands, the Central Brazilian Highlands, and the Pantepui region. We summarize the main geophysical and biotic characteristics of each mountain range, as well as key results from phylogenetic studies, the fossil record, and studies tackling biogeographical patterns of diversity, richness, and endemism. Moreover, mountain biodiversity studies can incorporate not only environmental data, but also information on more recent man-made landscape shifts. Here, we provide an example of how human population density interacts with climate and species traits to explain richness patterns in one group of montane organisms particularly vulnerable to environmental changes: anuran amphibians. Our results and the evidence published to date indicate that the Neogene and Quaternary were pivotal periods of Neotropical diversification for many terrestrial taxa, promoting endemism in non-Andean mountains. In general, all non-Andean mountain ranges have high levels of species richness and endemism as compared to their surrounding lowlands. Biotic interchange among them, the Andes, and their surrounding biotas has been intensive over tens of millions of years, greatly contributing to the outstanding levels of Neotropical biodiversity observed today. Despite their vast and understudied biodiversity, mountain ecosystems are fragile, facing severe challenges in the face of climate change, habitat loss, and extinctions. Efforts to better understand and protect South American mountain ecosystems are urgently needed.
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Mountains are arguably Earth's most striking features. They play a major role in determining global and regional climates, are the source of most rivers, act as cradles, barriers and bridges for species, and are crucial for the survival and sustainability of many human societies. The complexity of mountains is tightly associated with high biodiversity, but the processes underlying this association are poorly known. Solving this puzzle requires researchers to generate more primary data, and better integrate available geological and climatic data into biological models of diversity and evolution. In this perspective , we highlight emerging insights, which stress the importance of mountain building through time as a generator and reservoir of biodiversity. We also discuss recently proposed parallels between surface uplift, habitat formation and species diversification. We exemplify these links and discuss other factors, such as Quaternary climatic variations, which may have obscured some mountain-building evidence due to erosion and other processes. Biological evolution is complex and the build-up of mountains is certainly not the only explanation , but biological and geological processes are probably more intertwined than many of us realize. The overall conclusion is that geology sets the stage for speciation, where ecological interactions, adaptive and non-adaptive radiations and stochastic processes act together to increase biodiversity. Further integration of these fields may yield novel and robust insights.
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Mountain ranges harbour exceptionally high biodiversity, which is now under threat from rapid environmental change. However, despite decades of effort, the limited availability of data and analytical tools has prevented a robust and truly global characterization of elevational biodiversity gradients and their evolutionary origins1,2. This has hampered a general understanding of the processes involved in the assembly and maintenance of montane communities2,3,4. Here we show that a worldwide mid-elevation peak in bird richness is driven by wide-ranging species and disappears when we use a subsampling procedure that ensures even species representation in space and facilitates evolutionary interpretation. Instead, richness corrected for range size declines linearly with increasing elevation. We find that the more depauperate assemblages at higher elevations are characterized by higher rates of diversification across all mountain regions, rejecting the idea that lower recent diversification rates are the general cause of less diverse biota. Across all elevations, assemblages on mountains with high rates of past temperature change exhibit more rapid diversification, highlighting the importance of climatic fluctuations in driving the evolutionary dynamics of mountain biodiversity. While different geomorphological and climatic attributes of mountain regions have been pivotal in determining the remarkable richness gradients observed today, our results underscore the role of ongoing and often very recent diversification processes in maintaining the unique and highly adapted biodiversity of higher elevations.
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Although covering a relatively small fraction of terrestrial land (13-25%, Körner et al. 2011; Kapos et al 2000), mountain regions host an overproportional fraction of global biodiversity, supporting an estimated third of terrestrial biological diversity. On a global and regional scale, mountains that lie in areas of high biological richness are biodiversity hot spots because the rapid altitudinal change of climatic conditions over a very short distance gives rise to a range of bioclimatically defined vegetation types in close proximity. For example, in the tropics, mountains range from submontane forests to tropical alpine ecosystems, thereby concentrating high biodiversity on an area basis. High topographic diversity, characteristic feature of mountains, results in high habitat diversity and contributes to enhancing richness in biodiversity. Mountain biota, representing islands of high-elevation habitats and separated by the surrounding lowlands, have often formed in biogeographic isolation, resulting in high numbers on endemic species that further add to the uniqueness of mountain biodiversity.
Geographic patterns of species richness are influenced by many factors, but the role of shared physiographical and physiological boundaries in relation to range-size distributions has been surprisingly neglected, in spite of the fact that such geometric constraints lead to mid-domain richness peaks even without environmental gradients (the mid-domain effect). Relying on null models, several recent studies have begun to quantify this problem using simulated and empirical data. This approach promises to transform how we perceive geographic variation in diversity, including the long unresolved latitudinal gradient in species richness. The question is not whether geometry affects such patterns, but by how much.
Current global patterns of biodiversity result from processes that operate over both space and time and thus require an integrated macroecological and macroevolutionary perspective. Molecular time trees have advanced our understanding of the tempo and mode of diversification and have identified remarkable adaptive radiations across the tree of life. However, incomplete joint phylogenetic and geographic sampling has limited broad-scale inference. Thus, the relative prevalence of rapid radiations and the importance of their geographic settings in shaping global biodiversity patterns remain unclear. Here we present, analyse and map the first complete dated phylogeny of all 9,993 extant species of birds, a widely studied group showing many unique adaptations. We find that birds have undergone a strong increase in diversification rate from about 50 million years ago to the near present. This acceleration is due to a number of significant rate increases, both within songbirds and within other young and mostly temperate radiations including the waterfowl, gulls and woodpeckers. Importantly, species characterized with very high past diversification rates are interspersed throughout the avian tree and across geographic space. Geographically, the major differences in diversification rates are hemispheric rather than latitudinal, with bird assemblages in Asia, North America and southern South America containing a disproportionate number of species from recent rapid radiations. The contribution of rapidly radiating lineages to both temporal diversification dynamics and spatial distributions of species diversity illustrates the benefits of an inclusive geographical and taxonomical perspective. Overall, whereas constituent clades may exhibit slowdowns, the adaptive zone into which modern birds have diversified since the Cretaceous may still offer opportunities for diversification.
A phylogenetic reconstruction of the diversification of birds across space and time provides a novel resource for evolutionary studies. But the methods used to construct this tree, and what insights can be inferred from it, are a source of debate. Two evolutionary biologists provide opinions on how to draw the lines.
We studied the patterns of species richness and range–size rarity (as a measure of endemism) of two plant groups (Pteridophyta, Bromeliaceae) and birds along two gradients of elevation, humidity and human land use in a forested Andean valley. Both transects covered the transition from an arid valley bottom through a cloud forest zone to relictual high-elevation Polylepis forest, but transects differed in overall precipitation. Plants were surveyed in 88 plots of 400 m2 each, while birds were detected primarily through visual observations and tape recordings over areas of 0.3–1.5 km2. Global range sizes of all species were mapped on 1°-grids and range-size rarity was calculated as the mean inverse range size of all species recorded in elevational steps of 200 m. Patterns of species richness and range–size rarity were mainly unrelated between and within study groups. Monotonic increases and decreases and hump-shaped patterns were observed for species richness as well as range–size rarity. Several of these patterns can be interpreted in the light of the ecological requirements of each taxonomic group, e.g. dependence of fern species richness on humidity or of bird richness on habitat complexity. Species richness of ferns and birds peaked at higher elevations along the less rainy transect, possibly as a result of higher levels of solar radiation and ecosystem productivity. Patterns of species richness and endemism of the study groups are causally unrelated and cannot be used to predict those of other groups at the spatial scale of this study. Human impact was highest in areas of mostly low to intermediate species richness, but was often high in zones of high endemism.