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 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 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 On the processes generating latitudinal richness gradients: identifying diagnostic patterns and predictions

2014 ◽  
Author(s):  
Allen H Hurlbert ◽  
James C Stegen
Keyword(s):  
Species Richness ◽  
Negative Relationship ◽  
Niche Conservatism ◽  
Glacial Cycles ◽  
Climatic Fluctuations ◽  
Extinction Rates ◽  
Available Energy ◽  
Speciation Rates ◽  
Tropical Climates ◽  
The Tropics

Many processes have been put forward to explain the latitudinal gradient in species richness. Here, we use a simulation model to examine four of the most common hypotheses and identify patterns that might be diagnostic of those four hypotheses. The hypotheses examined include (1) tropical niche conservatism, or the idea that the tropics are more diverse because a tropical clade origin has allowed more time for diversification in the tropics and has resulted in few species adapted to extra-tropical climates. (2) The productivity, or energetic constraints, hypothesis suggests that species richness is limited by the amount of biologically available energy in a region. (3) The tropical stability hypothesis argues that major climatic fluctuations and glacial cycles in extratropical regions have led to greater extinction rates and less opportunity for specialization relative to the tropics. (4) Finally, the speciation rates hypothesis suggests that the latitudinal richness gradient arises from a parallel gradient in rates of speciation. We found that tropical niche conservatism can be distinguished from the other three scenarios by phylogenies which are more balanced than expected, no relationship between mean root distance and richness across regions, and a homogeneous rate of speciation across clades and through time. The energy gradient, speciation gradient, and disturbance gradient scenarios all exhibited phylogenies which were more imbalanced than expected, showed a negative relationship between mean root distance and richness, and diversity-dependence of speciation rate estimates through time. Using Bayesian Analysis of Macroevolutionary Mixtures on the simulated phylogenies, we found that the relationship between speciation rates and latitude could distinguish among these three scenarios. We emphasize the importance of considering multiple hypotheses and focusing on diagnostic predictions instead of predictions that are consistent with more than one hypothesis.

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.

scholarly journals On the processes generating latitudinal richness gradients: identifying diagnostic patterns and predictions

2014 ◽  
Author(s):  
Allen H Hurlbert ◽  
James C Stegen
Keyword(s):  
Species Richness ◽  
Negative Relationship ◽  
Niche Conservatism ◽  
Glacial Cycles ◽  
Climatic Fluctuations ◽  
Extinction Rates ◽  
Available Energy ◽  
Speciation Rates ◽  
Tropical Climates ◽  
The Tropics

Many processes have been put forward to explain the latitudinal gradient in species richness. Here, we use a simulation model to examine four of the most common hypotheses and identify patterns that might be diagnostic of those four hypotheses. The hypotheses examined include (1) tropical niche conservatism, or the idea that the tropics are more diverse because a tropical clade origin has allowed more time for diversification in the tropics and has resulted in few species adapted to extra-tropical climates. (2) The productivity, or energetic constraints, hypothesis suggests that species richness is limited by the amount of biologically available energy in a region. (3) The tropical stability hypothesis argues that major climatic fluctuations and glacial cycles in extratropical regions have led to greater extinction rates and less opportunity for specialization relative to the tropics. (4) Finally, the speciation rates hypothesis suggests that the latitudinal richness gradient arises from a parallel gradient in rates of speciation. We found that tropical niche conservatism can be distinguished from the other three scenarios by phylogenies which are more balanced than expected, no relationship between mean root distance and richness across regions, and a homogeneous rate of speciation across clades and through time. The energy gradient, speciation gradient, and disturbance gradient scenarios all exhibited phylogenies which were more imbalanced than expected, showed a negative relationship between mean root distance and richness, and diversity-dependence of speciation rate estimates through time. Using Bayesian Analysis of Macroevolutionary Mixtures on the simulated phylogenies, we found that the relationship between speciation rates and latitude could distinguish among these three scenarios. We emphasize the importance of considering multiple hypotheses and focusing on diagnostic predictions instead of predictions that are consistent with more than one hypothesis.

scholarly journals A comparison of the gobiid fauna between a shoal and an island habitat in the central Visayas (Philippines)

2014 ◽  
Author(s):  
Klaus M. Stiefel ◽  
Alistair Merrifield ◽  
Matt Reed ◽  
David B. Joyce
Keyword(s):  
Species Richness ◽  
Dominant Role ◽  
Depth Range ◽  
Undescribed Species ◽  
Species Numbers ◽  
Speciation Rates ◽  
Species Area ◽  
Island Habitat ◽  
New Type

We surveyed the marine gobies of Malapascua island (Philippines), the surrounding islets and the nearby Monad shoal. We found 59 species in 19 genera, including 2 undescribed species of the genus Trimma, and 3 geographic and 6 depth range expansions. Furthermore we describe a new type of mimicry between the goby Koumasetta hectori and the cardinalfish Apogon nigrofasciatus. The comparison of the island versus shoal goby fauna showed a lesser species richness of shrimpassociated gobies at the shoal. This likely reflects the fact that hydrodynamic features of the environment play a dominant role in selecting which gobiid species, or their symbiotic shrimp, will be found in a certain location. We also observed a bias towards hovering species (of the genus Trimma) and away from shrimp-associated gobies at greater depths. These findings are in accord with the suspected shift of gobies towards planctotrophy with increasing depth. We furthermore compare this study to previous surveys of goby faunas, and plot the recorded species numbers against the survey areas. This species-area plot provides support for the notion of high speciation rates in gobies due to their low mobility.

scholarly journals Signals of recent tropical radiations in Cunoniaceae, an iconic family for understanding Southern Hemisphere biogeography

2020 ◽  
Author(s):  
Ricardo A. Segovia ◽  
Andy R. Griffiths ◽  
Diego Arenas ◽  
A. A. Piyali Dias ◽  
Kyle G. Dexter
Keyword(s):  
Species Richness ◽  
Phylogenetic Diversity ◽  
Tropical Regions ◽  
Biogeographic History ◽  
Angiosperm Diversification ◽  
The Family ◽  
Tropical Areas ◽  
Recent Species ◽  
Angiosperm Species ◽  
The Tropics

AbstractExtratropical angiosperm diversity is thought to have arisen from lineages that originated in the more diverse tropics, but studies of dispersal between tropical and extratropical environments and their consequences for diversification are rare. In order to understand the evolutionary effects of shifts between the tropics and extratropics, defined here as areas that do versus do not regularly experience freezing temperatures, we studied the biogeographic history and associated diversification patterns of Cunoniaceae. We mapped the distribution of all species in the family and combined this with a newly constructed phylogeny for the family. The family shows a long evolutionary association with both tropical and extratropical environments, the tropics house considerably greater species richness of Cunoniaceae. Indeed, both tropical and extratropical environments appear to have had a similar number of lineages until 12 Ma, after which time the number of lineages in tropical areas increased at a faster rate. In addition, community phylogenetic approaches show that tropical regions have markedly less phylogenetic diversity than expected given their species richness, which is further suggestive of recent species radiations in tropical areas. The Cunoniaceae show an atypical pattern for angiosperms of frequent shifts between tropical and extratropical environments, but despite this, shows a more conventional pattern of higher, although recent, diversification rates in the tropics. Our results support the idea that high angiosperm species richness in the tropics may result from the tropics acting as a cradle of recent angiosperm diversification.

scholarly journals Cryptic species diversity reveals biogeographic support for the ‘mountain passes are higher in the tropics’ hypothesis

2016 ◽  
Vol 283 (1832) ◽  
pp. 20160553 ◽  
Author(s):  
B. A. Gill ◽  
B. C. Kondratieff ◽  
K. L. Casner ◽  
A. C. Encalada ◽  
A. S. Flecker ◽  
...  
Keyword(s):  
Species Richness ◽  
Cryptic Species ◽  
Integrative Taxonomy ◽  
Cryptic Diversity ◽  
Opposite Pattern ◽  
The Andes ◽  
Low Latitudes ◽  
Dispersal Traits ◽  
Morphological Differences ◽  
The Tropics

The ‘mountain passes are higher in the tropics’ (MPHT) hypothesis posits that reduced climate variability at low latitudes should select for narrower thermal tolerances, lower dispersal and smaller elevational ranges compared with higher latitudes. These latitudinal differences could increase species richness at low latitudes, but that increase may be largely cryptic, because physiological and dispersal traits isolating populations might not correspond to morphological differences. Yet previous tests of the MPHT hypothesis have not addressed cryptic diversity. We use integrative taxonomy, combining morphology (6136 specimens) and DNA barcoding (1832 specimens) to compare the species richness, cryptic diversity and elevational ranges of mayflies (Ephemeroptera) in the Rocky Mountains (Colorado; approx. 40°N) and the Andes (Ecuador; approx. 0°). We find higher species richness and smaller elevational ranges in Ecuador than Colorado, but only after quantifying and accounting for cryptic diversity. The opposite pattern is found when comparing diversity based on morphology alone, underscoring the importance of uncovering cryptic species to understand global biodiversity patterns.

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.

scholarly journals Minimal effects of latitude on present-day speciation rates in New World birds

2015 ◽  
Vol 282 (1809) ◽  
pp. 20142889 ◽  
Author(s):  
Daniel L. Rabosky ◽  
Pascal O. Title ◽  
Huateng Huang
Keyword(s):  
Phylogenetic Trees ◽  
New World ◽  
Evolutionary Dynamics ◽  
Cohort Analysis ◽  
Speciation Rate ◽  
Species Formation ◽  
Speciation Rates ◽  
History Of ◽  
New World Birds ◽  
The Tropics

The tropics contain far greater numbers of species than temperate regions, suggesting that rates of species formation might differ systematically between tropical and non-tropical areas. We tested this hypothesis by reconstructing the history of speciation in New World (NW) land birds using BAMM, a Bayesian framework for modelling complex evolutionary dynamics on phylogenetic trees. We estimated marginal distributions of present-day speciation rates for each of 2571 species of birds. The present-day rate of speciation varies approximately 30-fold across NW birds, but there is no difference in the rate distributions for tropical and temperate taxa. Using macroevolutionary cohort analysis, we demonstrate that clades with high tropical membership do not produce species more rapidly than temperate clades. For nearly any value of present-day speciation rate, there are far more species in the tropics than the temperate zone. Any effects of latitude on speciation rate are marginal in comparison to the dramatic variation in rates among clades.

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