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 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 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 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 Ancient tropical extinctions contributed to the latitudinal diversity gradient

2017 ◽  
Author(s):  
Andrea S. Meseguer ◽  
Fabien L. Condamine
Keyword(s):  
Time Variable ◽  
Cold Climate ◽  
Similar Species ◽  
High Latitudes ◽  
Latitudinal Diversity Gradient ◽  
Diversity Gradient ◽  
Tropical Diversity ◽  
Starting Point ◽  
Limited Dispersal ◽  
Extinction Events

AbstractBiodiversity currently peaks at the equator, decreasing toward the poles. Growing fossil evidence suggest that this hump-shaped latitudinal diversity gradient (LDG) has not been persistent through time, with similar species diversity across latitudes flattening out the LDG during past greenhouse periods. This provides a new starting point for LDG research. Most studies assume the processes shaping the LDG have acted constantly through time and seek to understand why diversity accumulated in the Holarctic at lower levels than at the equator, e.g. as the result of limited dispersal, or higher turnover in Holarctic regions. However, fossil investigations suggest that we need to explain when and why diversity was lost at high latitudes to generate the LDG. Unfortunately, diversity lost scenarios in the Holarctic have been repeatedly proposed but not yet clearly demonstrated. Here, we use diversification approaches for both phylogenies and fossils to study the LDG of Testudines, Crocodilia and Lepidosauria. We show the LDG of these groups has varied over time, with high latitudes serving as a source of tropical diversity but suffering disproportionate extinction during transitional periods to cold climate. We outline the ‘asymmetric gradient of extinction and dispersal’ (AGED) framework, which contextualizes previous ideas behind the LDG under a time-variable scenario. We suggest the current steep LDG may be explained by the extinction of clades adapted to warmer conditions from the new temperate regions formed in the Neogene, together with the equator-ward dispersal of organisms tracking their own climatic preferences, when tropical biomes became restricted to the equator. Conversely, high rates of speciation and pole-ward dispersals can account for the formation of an ancient flat LDG during the Cretaceous–Paleogene greenhouse period. Our results demonstrate that the inclusion of fossils in macroevolutionary studies allows detecting extinction events less detectable in analyses restricted to present-day data only.

Evolutionary and Ecological Causes of the Latitudinal Diversity Gradient in Hylid Frogs: Treefrog Trees Unearth the Roots of High Tropical Diversity

2006 ◽  
Vol 168 (5) ◽  
pp. 579-596 ◽  
Author(s):  
John J. Wiens ◽  
Catherine H. Graham ◽  
Daniel S. Moen ◽  
Sarah A. Smith ◽  
Tod W. Reeder
Keyword(s):  
Latitudinal Diversity Gradient ◽  
Diversity Gradient ◽  
Tropical Diversity

Exploring the origin of the latitudinal diversity gradient: Contrasting the sister fern generaPhegopterisandPseudophegopteris

2012 ◽  
pp. n/a-n/a
Author(s):  
Harald SCHNEIDER ◽  
Li-Juan HE ◽  
Jeannine MARQUARDT ◽  
Li WANG ◽  
Jochen HEINRICHS ◽  
...  
Keyword(s):  
Latitudinal Diversity Gradient ◽  
Diversity Gradient
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