scholarly journals The contribution of global mountains to the latitudinal diversity gradient

2020 ◽  
Author(s):  
Elkin A. Tenorio ◽  
Paola Montoya ◽  
Natalia Norden ◽  
Susana Rodríguez-Buriticá ◽  
Beatriz Salgado-Negret ◽  
...  
Keyword(s):  
Species Richness ◽  
Unit Area ◽  
Species Turnover ◽  
Geographical Information ◽  
Mountain Ranges ◽  
Terrestrial Vertebrates ◽  
Latitudinal Diversity Gradient ◽  
Diversity Gradient ◽  
Diversity Gradients ◽  
Time And Energy

AbstractThe latitudinal diversity gradient (LDG) is widely attributed to be the result of factors such as time, area, and energy. Although these factors explain most of the variation in lowlands, they fail in mountainous systems, which are biodiversity hotspots that may contribute meaningfully to the strength of the pattern following different evolutionary pathways. However, because lowlands cover the largest portion of the total land, they may have overshadowed the contribution of mountains to the LDG, but no study has addressed this issue in previous macroecological analyses. Here, we propose that the LDG shows a stronger trend in mountain ranges due to their high species turnover, in spite of covering less than one third of the Earth’s land. Using the geographical information for ∼22000 species of terrestrial vertebrates, we show that worldwide mountains harbor the 40% of the global diversity, and when taking into account the area effect, we quantified that mountains harbor close to double the species inhabiting lowlands per unit area. Moreover, when we evaluated the LDG after accounting for area size, we found that species richness increased faster towards the Equator and was better predicted by latitude in mountains than in lowlands. Our findings challenge previously well-supported hypotheses that predict that those regions with greater area, time and energy accumulate more species richness, since mountains are geologically younger, exhibit less energy, and cover smaller areas than lowlands. Hence, mountains represent a paradox, which invites to reevaluate hypotheses regarding macroecological and evolutionary processes driving species diversity gradients.

scholarly journals Historical contingency, niche conservatism and the tendency for some taxa to be more diverse towards the poles

2018 ◽  
Author(s):  
Ignacio Morales-Castilla ◽  
Jonathan T Davies ◽  
Miguel Ángel Rodríguez
Keyword(s):  
Strongly Correlated ◽  
Historical Contingency ◽  
Land Bridge ◽  
Cold Temperatures ◽  
Latitudinal Diversity Gradient ◽  
Diversity Gradient ◽  
Tropical Diversity ◽  
Diversity Gradients ◽  
Climate Space

Successful explanations for diversity gradients should account for both the generalized tendency towards a higher tropical diversity and its exceptions. Moreover, identifying exceptions to general trends, such as the latitudinal diversity gradient can give insight into the mechanistic explanations responsible for structuring them. The Cenozoic biotic exchange of mammals across the Bering land-bridge provides an illuminating case-study. It allows comparing the diversity of clades that participated in the exchange (colonizers), whose ancestors withstood the Beringian cold temperatures, with that of the clades that did not participate (sedentaries). We find that assemblages of colonizers are more diverse towards higher latitudes, opposing the traditional latitudinal diversity gradient which is followed by sedentaries. Despite the long passage of time since this major dispersal event, the geographic distribution of colonizers is more strongly correlated to the distributions of other colonizers inhabiting a different continent than by the distribution of sedentary species. These results highlight the importance of historical migrations and dispersal in configuring present-day diversity gradients. Importantly, we also suggest that colonizers may be particularly vulnerable to projected climate change because of the predicted decrease in climate space in the extra-tropical realm where they are currently most diverse.

scholarly journals Fast diversification through a mosaic of evolutionary histories characterizes the endemic flora of ancient Neotropical mountains

2020 ◽  
Vol 287 (1923) ◽  
pp. 20192933 ◽  
Author(s):  
Thais N. C. Vasconcelos ◽  
Suzana Alcantara ◽  
Caroline O. Andrino ◽  
Félix Forest ◽  
Marcelo Reginato ◽  
...  
Keyword(s):  
Species Richness ◽  
Plant Species ◽  
Species Turnover ◽  
Plant Species Richness ◽  
Campo Rupestre ◽  
Population Isolation ◽  
Mountain Ranges ◽  
Extinction Rates ◽  
Speciation Rates ◽  
Endemic Flora

Mountains are among the most biodiverse areas on the globe. In young mountain ranges, exceptional plant species richness is often associated with recent and rapid radiations linked to the mountain uplift itself. In ancient mountains, however, orogeny vastly precedes the evolution of vascular plants, so species richness has been explained by species accumulation during long periods of low extinction rates. Here we evaluate these assumptions by analysing plant diversification dynamics in the campo rupestre , an ecosystem associated with pre-Cambrian mountaintops and highlands of eastern South America, areas where plant species richness and endemism are among the highest in the world. Analyses of 15 angiosperm clades show that radiations of endemics exhibit fastest rates of diversification during the last 5 Myr, a climatically unstable period. However, results from ancestral range estimations using different models disagree on the age of the earliest in situ speciation events and point to a complex floristic assembly. There is a general trend for higher diversification rates associated with these areas, but endemism may also increase or reduce extinction rates, depending on the group. Montane habitats, regardless of their geological age, may lead to boosts in speciation rates by accelerating population isolation in archipelago-like systems, circumstances that can also result in higher extinction rates and fast species turnover, misleading the age estimates of endemic lineages.

Can latitudinal richness gradients be measured in the terrestrial fossil record?

Paleobiology ◽  
2017 ◽  
Vol 43 (3) ◽  
pp. 479-494 ◽  
Author(s):  
Danielle Fraser
Keyword(s):  
Body Size ◽  
Fossil Record ◽  
Species Turnover ◽  
Small Body ◽  
Geographic Range ◽  
Biological Information ◽  
Gradient Estimates ◽  
Mammal Species ◽  
Latitudinal Diversity Gradient ◽  
Diversity Gradient

AbstractStudying the deep-time origins of macroecological phenomena can help us to understand their long-term drivers. Given the considerable spatiotemporal bias of the terrestrial fossil record, it behooves us to understand how much biological information is lost. The aim of this study is to establish whether latitudinal diversity gradients are detectable in a biased terrestrial fossil record. I develop a simulated fossilization approach, weighting the probability of terrestrial mammal species appearing in the fossil record based on body size and geographic-range size; larger species with larger range sizes are more likely to enter the fossil record. I create simulated fossil localities from the modern North American mammal record. I vary the percentage of species successfully fossilized and estimate the magnitude of the latitudinal diversity gradient (slope of the richness gradient and degree of species turnover). I find that estimates of the latitudinal diversity gradient are sensitive to the loss of species with small body size and geographic-range sizes. In some cases, simulated fossil-record bias completely obliterates evidence of declining richness with latitude, a phenomenon that is not ameliorated by the application of nonparametric richness estimation. However, if the rate of preservation is medium (50% of species) to high (75% of species), the magnitude of the latitudinal diversity gradient can be reliably estimated. Similarly, changes in the diversity gradient estimates are largely explained by differences in the diversity–climate relationship among iterations, suggesting that these relationships may be measurable in the fossil record.

scholarly journals Ecological causes of uneven speciation and species richness in mammals

2019 ◽  
Author(s):  
Nathan S. Upham ◽  
Jacob A. Esselstyn ◽  
Walter Jetz
Keyword(s):  
Species Richness ◽  
Species Turnover ◽  
Rate Variation ◽  
Ecological Traits ◽  
Ecological Opportunity ◽  
Diversification Rates ◽  
Speciation Rate ◽  
Diversity Gradient ◽  
Speciation Rates

ABSTRACTBiodiversity is distributed unevenly from the poles to the equator, and among branches of the tree of life, yet how those enigmatic patterns are related is unclear. We investigated global speciation-rate variation across crown Mammalia using a novel time-scaled phylogeny (N=5,911 species, ~70% with DNA), finding that trait- and latitude-associated speciation has caused uneven species richness among groups. We identify 24 branch-specific shifts in net diversification rates linked to ecological traits. Using time-slices to define clades, we show that speciation rates are a stronger predictor of clade richness than age. Speciation is slower in tropical than extra-tropical lineages, but only at the level of clades not species tips, consistent with fossil evidence that the latitudinal diversity gradient may be a relatively young phenomenon in mammals. In contrast, species tip rates are fastest in mammals that are low dispersal or diurnal, consistent with models of ephemeral speciation and ecological opportunity, respectively. These findings juxtapose nested levels of diversification, suggesting a central role of species turnover gradients in generating uneven patterns of modern biodiversity.

scholarly journals Angiosperm speciation speeds up near the poles

2019 ◽  
Author(s):  
J. Igea ◽  
A. J. Tanentzap
Keyword(s):  
Species Richness ◽  
Environmental Change ◽  
Species Turnover ◽  
Undescribed Species ◽  
Opposite Pattern ◽  
Speciation Rate ◽  
Diversity Gradient ◽  
Speciation Rates ◽  
Angiosperm Species ◽  
The Tropics

AbstractRecent evidence has questioned whether the Latitudinal Diversity Gradient (LDG), whereby species richness increases towards the Equator, results from higher rates of speciation in the tropics. Allowing for time heterogeneity in speciation rate estimates for over 60,000 angiosperm species, we found that the LDG does not arise from variation in speciation rates because lineages do not speciate faster in the tropics. These results were consistently retrieved using two other methods to test the association between occupancy of tropical habitats and speciation rates. Our speciation rate estimates were robust to the effects of both undescribed species and missing taxa. Overall, our results show that speciation rates follow an opposite pattern to global variation in species richness. Greater ecological opportunity in the temperate zones, stemming from less saturated communities, higher species turnover or greater environmental change, may ultimately explain these results.

scholarly journals Evolutionary time best explains the latitudinal diversity gradient of living freshwater fish diversity

2019 ◽  
Author(s):  
Elizabeth Christina Miller ◽  
Cristian Román-Palacios
Keyword(s):  
Species Richness ◽  
Freshwater Fish ◽  
Surface Area ◽  
Explanatory Power ◽  
Additive Models ◽  
Fish Diversity ◽  
Diversification Rates ◽  
Latitudinal Diversity Gradient ◽  
Diversity Gradient ◽  
Basin Surface

AbstractAimThe evolutionary causes of the latitudinal diversity gradient are debated. Hypotheses have ultimately invoked either faster rates of diversification in the tropics, or more time for diversification due to the tropical origins of higher taxa. Here we perform the first test of the diversification rate and time hypotheses in freshwater ray-finned fishes, a group comprising nearly a quarter of all living vertebrates.LocationGlobal.Time period368–0 mya.Major taxa studiedExtant freshwater ray-finned fishes.MethodsUsing a mega-phylogeny of actinopterygian fishes and a global database of occurrence records, we estimated net diversification rates, the number of colonizations and regional colonization times of co-occurring species in freshwater drainage basins. We used Generalized Additive Models to test whether these factors were related to latitude. We then compared the influence of diversification rates, colonization numbers, colonization times and surface area on species richness, and how these factors are related to each other.ResultsWhile both diversification rates and time were related to richness, time had greater explanatory power and was more strongly related to latitude than diversification rates. Other factors (basin surface area, number of colonizations) also helped explain richness but were unrelated to latitude. The world’s most diverse freshwater basins (Amazon, Congo rivers) were dominated by lineages with Mesozoic origins. The temperate groups dominant today arrived near the K-Pg boundary, leaving comparatively less time to build richness. Diversification rates and colonization times were inversely related: recently colonized basins had the fastest rates, while ancient species-rich faunas had slower rates.Main conclusionsWe concluded that time is the lead driver of latitudinal richness disparities in freshwater fish faunas. We suggest that the most likely path to building very high species richness is through diversification over long periods of time, rather than diversifying quickly.

scholarly journals Relative effects of time for speciation and tropical niche conservatism on the latitudinal diversity gradient of phyllostomid bats

2011 ◽  
Vol 278 (1717) ◽  
pp. 2528-2536 ◽  
Author(s):  
Richard D. Stevens
Keyword(s):  
New World ◽  
Latitudinal Gradients ◽  
Future Research ◽  
Niche Conservatism ◽  
Environmental Determinants ◽  
Environmental Characteristics ◽  
Latitudinal Diversity Gradient ◽  
Diversity Gradient ◽  
Historical Processes ◽  
Diversity Gradients

Determinants of contemporary patterns of diversity, particularly those spanning extensive latitudinal gradients, are some of the most intensely debated issues in ecology. Recently, focus has shifted from a contemporary environmental perspective to a historical one in an attempt to better understand the construction of latitudinal gradients. Although the vast majority of research on historical mechanisms has focused on tropical niche conservatism (TNC), other historical scenarios could produce similar latitudinal gradients. Herein, I formalize predictions to distinguish between two such historical processes—namely time for speciation (TFS) and TNC—and test relative support based on diversity gradients of New World bats. TFS and TNC are distinctly spatial and environmental mechanisms, respectively. Nonetheless, because of the way that environmental characteristics vary spatially, these two mechanisms are hard to distinguish. Evidence provided herein suggests that TNC has had a more important effect than TFS in determining diversity gradients of New World bats. Indeed, relative effects of different historical mechanisms, as well as relative effects of historical and contemporary environmental determinants, are probably context-dependent. Future research should move away from attempting to identify the mechanism with primacy and instead attempt to understand the particular contexts in which different mechanisms have greater influence on diversity gradients.

scholarly journals Truncated bimodal latitudinal diversity gradient in early Paleozoic phytoplankton

2021 ◽  
Vol 7 (15) ◽  
pp. eabd6709
Author(s):  
Axelle Zacaï ◽  
Claude Monnet ◽  
Alexandre Pohl ◽  
Grégory Beaugrand ◽  
Gary Mullins ◽  
...  
Keyword(s):  
Species Richness ◽  
Climate Changes ◽  
Sea Surface ◽  
Marine Phytoplankton ◽  
Sampling Effort ◽  
Early Paleozoic ◽  
Latitudinal Diversity Gradient ◽  
Diversity Gradient ◽  
Geological Past

The latitudinal diversity gradient (LDG)—the decline in species richness from the equator to the poles—is classically considered as the most pervasive macroecological pattern on Earth, but the timing of its establishment, its ubiquity in the geological past, and explanatory mechanisms remain uncertain. By combining empirical and modeling approaches, we show that the first representatives of marine phytoplankton exhibited an LDG from the beginning of the Cambrian, when most major phyla appeared. However, this LDG showed a single peak of diversity centered on the Southern Hemisphere, in contrast to the equatorial peak classically observed for most modern taxa. We find that this LDG most likely corresponds to a truncated bimodal gradient, which probably results from an uneven sediment preservation, smaller sampling effort, and/or lower initial diversity in the Northern Hemisphere. Variation of the documented LDG through time resulted primarily from fluctuations in annual sea-surface temperature and long-term climate changes.

scholarly journals Out of the extratropics: the evolution of the latitudinal diversity gradient of Cenozoic marine plankton

2021 ◽  
Vol 288 (1950) ◽  
Author(s):  
Nussaïbah B. Raja ◽  
Wolfgang Kiessling
Keyword(s):  
Species Richness ◽  
Opposite Direction ◽  
Large Scale ◽  
Climatic Changes ◽  
Marine Plankton ◽  
Latitudinal Diversity Gradient ◽  
Diversity Gradient ◽  
Cenozoic Era ◽  
The Tropics ◽  
Early Cenozoic

Many ecological and evolutionary hypotheses have been proposed to explain the latitudinal diversity gradient, i.e. the increase in species richness from the poles to the tropics. Among the evolutionary hypotheses, the ‘out of the tropics’ (OTT) hypothesis has received considerable attention. The OTT posits that the tropics are both a cradle and source of biodiversity for extratropical regions. To test the generality of the OTT hypothesis, we explored the spatial biodiversity dynamics of unicellular marine plankton over the Cenozoic era (the last 66 Myr). We find large-scale climatic changes during the Cenozoic shaped the diversification and dispersal of marine plankton. Origination was generally more likely in the extratropics and net dispersal was towards the tropics rather than in the opposite direction, especially during the warmer climates of the early Cenozoic. Although migration proportions varied among major plankton groups and climate phases, we provide evidence that the extratropics were a source of tropical microplankton biodiversity over the last 66 Myr.

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