scholarly journals Diversification rates and species richness across the Tree of Life

2016 ◽  
Vol 283 (1838) ◽  
pp. 20161334 ◽  
Author(s):  
Joshua P. Scholl ◽  
John J. Wiens
Keyword(s):  
Species Richness ◽  
Positive Relationship ◽  
Tree Of Life ◽  
Diversification Rate ◽  
Substantial Variation ◽  
Diversification Rates ◽  
Higher Taxa ◽  
Over Time

Species richness varies dramatically among clades across the Tree of Life, by over a million-fold in some cases (e.g. placozoans versus arthropods). Two major explanations for differences in richness among clades are the clade-age hypothesis (i.e. species-rich clades are older) and the diversification-rate hypothesis (i.e. species-rich clades diversify more rapidly, where diversification rate is the net balance of speciation and extinction over time). Here, we examine patterns of variation in diversification rates across the Tree of Life. We address how rates vary across higher taxa, whether rates within higher taxa are related to the subclades within them, and how diversification rates of clades are related to their species richness. We find substantial variation in diversification rates, with rates in plants nearly twice as high as in animals, and rates in some eukaryotes approximately 10-fold faster than prokaryotes. Rates for each kingdom-level clade are then significantly related to the subclades within them. Although caution is needed when interpreting relationships between diversification rates and richness, a positive relationship between the two is not inevitable. We find that variation in diversification rates seems to explain most variation in richness among clades across the Tree of Life, in contrast to the conclusions of previous studies.

scholarly journals Thirty-six years of legal and illegal wildlife trade entering the USA

Oryx ◽  
2019 ◽  
pp. 1-10 ◽  
Author(s):  
Maria Therese Bager Olsen ◽  
Jonas Geldmann ◽  
Mike Harfoot ◽  
Derek P. Tittensor ◽  
Becky Price ◽  
...  
Keyword(s):  
Decision Making ◽  
Species Richness ◽  
Positive Relationship ◽  
Species Conservation ◽  
Wildlife Trade ◽  
Country Size ◽  
The Usa ◽  
Taxonomic Groups ◽  
Over Time ◽  
Main Region

AbstractThe USA is the largest consumer of legally, internationally-traded wildlife. A proportion of this trade consists of species listed in the Appendices of CITES, and recorded in the CITES Trade Database. Using this resource, we quantified wildlife entering the USA for 82 of the most frequently recorded wildlife products and a range of taxonomic groups during 1979–2014. We examined trends in legal trade and seizures of illegally traded items over time, and relationships between trade and four national measures of biodiversity. We found that: (1) there is an overall positive relationship between legal imports and seizures; (2) Asia was the main region exporting CITES-listed wildlife products to the USA; (3) bears, crocodilians and other mammals (i.e. other than Ursidae, Felidae, Cetacea, Proboscidea, Primates or Rhinocerotidae) increased in both reported legal trade and seizures over time; (4) legal trade in live specimens was reported to be primarily from captive-produced, artificially-propagated or ranched sources, whereas traded meat was primarily wild sourced; (5) both seizures and legally traded items of felids and elephants decreased over time; and (6) volumes of both legally traded and seized species were correlated with four attributes of exporting countries: species endemism, species richness, number of IUCN threatened species, and country size. The goal of our analysis was to inform CITES decision-making and species conservation efforts.

scholarly journals The Dynamics of Bird Diversity in the New World

2020 ◽  
Vol 69 (6) ◽  
pp. 1180-1199 ◽  
Author(s):  
Antonin Machac
Keyword(s):  
Species Richness ◽  
New World ◽  
Dominant Role ◽  
Bird Diversity ◽  
Biodiversity Hotspots ◽  
Relative Importance ◽  
Diversification Rates ◽  
The Andes ◽  
The Rich ◽  
Over Time

Abstract Three prominent explanations have been proposed to explain the dramatic differences in species richness across regions and elevations, (i) time for speciation, (ii) diversification rates, and (iii) ecological limits. But the relative importance of these explanations and, especially, their interplay and possible synthesis remain largely elusive. Integrating diversification analyses, null models, and geographic information systems, I study avian richness across regions and elevations of the New World. My results reveal that even though the three explanations are differentially important (with ecological limits playing the dominant role), each contributes uniquely to the formation of richness gradients. Further, my results reveal the likely interplay between the explanations. They indicate that ecological limits hinder the diversification process, such that the accumulation of species within a region gradually slows down over time. Yet, it does not seem to converge toward a hard ceiling on regional richness. Instead, species-rich regions show suppressed, but continued, diversification, coupled with signatures of possible competition (esp. Neotropical lowlands). Conversely, species-poor, newly-colonized regions show fast diversification and weak to no signs of competition (esp. Nearctic highlands). These results held across five families of birds, across grid cells, biomes, and elevations. Together, my findings begin to illuminate the rich, yet highly consistent, interplay of the mechanisms that together shape richness gradients in the New World, including the most species-rich biodiversity hotspots on the planet, the Andes and the Amazon. [Biogeography; community; competition; macroevolution; phylogenetics; richness gradient.]

scholarly journals Polyploidy increases overall diversity despite higher turnover than diploids in the Brassicaceae

2019 ◽  
Author(s):  
Cristian Román-Palacios ◽  
Y. Franchesco Molina-Henao ◽  
Michael S. Barker
Keyword(s):  
Species Richness ◽  
Chromosome Numbers ◽  
Long Term Evolution ◽  
Tree Of Life ◽  
Evolutionary Significance ◽  
Diversification Rates ◽  
Diversity Patterns ◽  
Term Evolution ◽  
Speciation Rates

AbstractAlthough polyploidy, or whole-genome duplication, is widespread across the Plant Tree of Life, its long-term evolutionary significance is still poorly understood. Here we examine the effects of polyploidy in driving macroevolutionary patterns within the angiosperm family Brassicaceae, a speciose clade exhibiting extensive inter-specific variation in chromosome numbers. We inferred ploidal levels from haploid chromosome numbers for 80% of species in the most comprehensive species-level chronogram for the Brassicaceae published to date. After evaluating a total of 54 phylogenetic models of diversification, we found that ploidy drives diversification rates across the Brassicaceae, with polyploids experiencing faster rates of speciation and extinction, but relatively slower rates of diversification. Nevertheless, diversification rates are, on average, positive for both polyploids and diploids. We also found that despite diversifying significantly slower than diploids, polyploids have played a significant role in driving present-day differences in species richness among clades. Overall, although most polyploids go extinct before sustainable populations are established, rare successful polyploids persist and significantly contribute to the long-term evolution of lineages. Our findings suggest that polyploidy has played a major role in shaping the long-term evolution of the Brassicaceae and highlight the importance of polyploidy in shaping present-day diversity patterns across the plant Tree of Life.Significance statementAlthough polyploidy is a source of innovation, its long-term evolutionary significance is still debated. Here we analyze the evolutionary role of polyploidy within the Brassicaceae, a diverse clade exhibiting extensive variation in chromosome numbers among species. We found that, although polyploids diversify slower than diploids, polyploids have faster extinction and speciation rates. Our results also suggest that polyploidy has played an important role in shaping present-day differences in species richness within the Brassicaceae, with potential implications in explaining diversity patterns across the plant Tree of Life.

scholarly journals Multicellularity and sex helped shape the Tree of Life

2021 ◽  
Vol 288 (1955) ◽  
pp. 20211265
Author(s):  
Lian Chen ◽  
John J. Wiens
Keyword(s):  
Species Richness ◽  
Sexual Reproduction ◽  
Tree Of Life ◽  
Diversification Rates ◽  
Species Numbers

Across the Tree of Life, there are dramatic differences in species numbers among groups. However, the factors that explain the differences among the deepest branches have remained unknown. We tested whether multicellularity and sexual reproduction might explain these patterns, since the most species-rich groups share these traits. We found that groups with multicellularity and sexual reproduction have accelerated rates of species proliferation (diversification), and that multicellularity has a stronger effect than sexual reproduction. Patterns of species richness among clades are then strongly related to these differences in diversification rates. Taken together, these results help explain patterns of biodiversity among groups of organisms at the very broadest scales. They may also help explain the mysterious preponderance of sexual reproduction among species (the ‘paradox of sex’) by showing that organisms with sexual reproduction proliferate more rapidly.

scholarly journals Constant diversification rates of endemic gastropods in ancient Lake Ohrid: ecosystem resilience likely buffers environmental fluctuations

2015 ◽  
Vol 12 (23) ◽  
pp. 7209-7222 ◽  
Author(s):  
K. Föller ◽  
B. Stelbrink ◽  
T. Hauffe ◽  
C. Albrecht ◽  
T. Wilke
Keyword(s):  
Diversification Rate ◽  
Ancient Lakes ◽  
Freshwater Species ◽  
Ecosystem Resilience ◽  
Ancient Lake ◽  
Lake Ohrid ◽  
Deep Drilling ◽  
Diversification Rates ◽  
Environmental Events ◽  
Over Time

Abstract. Ancient lakes represent key ecosystems for endemic freshwater species. This high endemic biodiversity has been shown to be mainly the result of intra-lacustrine diversification. Whereas the principle role of this mode of diversification is generally acknowledged, actual diversification rates in ancient lakes remain little understood. At least four types are conceivable. Diversification rates may be constant over time, they may fluctuate, rates may be higher in the initial phase of diversification, or there may be a pronounced lag phase between colonization and subsequent diversification. As understanding the tempo of diversification in ancient lake environments may help reveal the underlying processes that drive speciation and extinction, we here use the Balkan Lake Ohrid as a model system and the largest species flock in the lake, the non-pyrgulinid Hydrobiidae, as a model taxon to study changes in diversification rates over time together with the respective drivers. Based on phylogenetic, molecular-clock, lineage-through-time plot, and diversification-rate analyses we found that this potentially monophyletic group is comparatively old and that it most likely evolved with a constant diversification rate. Preliminary data of the SCOPSCO (Scientific Collaboration On Past Speciation Conditions in Lake Ohrid) deep-drilling program do indicate signatures of severe environmental/climatic perturbations in Lake Ohrid. However, so far there is no evidence for the occurrence of catastrophic environmental events. We therefore propose that the constant diversification rate observed in endemic gastropods has been caused by two factors: (i) a potential lack of catastrophic environmental events in Lake Ohrid and/or (ii) a probably high ecosystem resilience, buffering environmental changes. Parameters potentially contributing to the lake's high ecosystem resilience are its distinct bathymetry, ongoing tectonic activities, and karst hydrology. The current study not only contributes to one of the overall goals of the SCOPSCO deep-drilling program – inferring the driving forces for biotic evolution in Lake Ohrid. It might also enhance our understanding of how ecosystem resilience, in general, may promote relatively constant diversification rates in isolated ecosystems. However, we encourage future studies testing hypotheses about the lack of catastrophic events in Lake Ohrid. These studies should be based on high-resolution data for the entire geological history of the lake, and they should potentially involve information from the sediment fossil record, not only for gastropods but also for other groups with a high share of endemic taxa.

scholarly journals Diversification rates and the latitudinal gradient of diversity in mammals

2012 ◽  
Vol 279 (1745) ◽  
pp. 4148-4155 ◽  
Author(s):  
Víctor Soria-Carrasco ◽  
Jose Castresana
Keyword(s):  
Species Richness ◽  
Species Distribution ◽  
Phylogenetic Trees ◽  
Latitudinal Gradient ◽  
Diversification Rate ◽  
Independent Contrasts ◽  
Diversification Rates ◽  
Extinction Rates ◽  
Phylogenetically Independent Contrasts ◽  
Distribution Ranges

The latitudinal gradient of species richness has frequently been attributed to higher diversification rates of tropical groups. In order to test this hypothesis for mammals, we used a set of 232 genera taken from a mammalian supertree and, additionally, we reconstructed dated Bayesian phylogenetic trees of 100 genera. For each genus, diversification rate was estimated taking incomplete species sampling into account and latitude was assigned considering the heterogeneity in species distribution ranges. For both datasets, we found that the average diversification rate was similar among all latitudinal bands. Furthermore, when we used phylogenetically independent contrasts, we did not find any significant correlation between latitude and diversification parameters, including different estimates of speciation and extinction rates. Thus, other factors, such as the dynamics of dispersal through time, may be required to explain the latitudinal gradient of diversity in mammals.

scholarly journals Can net diversification rates account for spatial patterns of species richness?

2017 ◽  
Author(s):  
Camilo Sanín ◽  
Iván Jiménez ◽  
Jon Fjeldså ◽  
Carsten Rahbek ◽  
Carlos Daniel Cadena
Keyword(s):  
Species Richness ◽  
Spatial Variation ◽  
Spatial Patterns ◽  
Explanatory Power ◽  
Large Family ◽  
Diversification Rate ◽  
Diversification Rates ◽  
Grain Sizes ◽  
Time Period ◽  
Richness Patterns

ABSTRACTThe diversification rate hypothesis (DRH) proposes that spatial patterns of species richness result from spatial variation in net diversification rates. We developed an approach using a time-calibrated phylogeny and distributional data to estimate the maximum explanatory power of the DRH, over a given time period, to current species richness in an area. We used this approach to study species richness patterns of a large family of suboscine birds across South America. The maximum explanatory power of the DRH increased with the duration of the time period considered and grain size; it ranged from 13 – 37 fold local increases in species richness for T = 33 Ma to less than 2-fold increases for T ≤ 10 Ma. For large grain sizes (≤ 8° × 8°) diversification rate over the last 10 Ma could account for all the spatial variance in species richness, but for smaller grain sizes commonly used in biogeographical studies (1° × 1°), it could only explain < 16% of this variance. Thus, diversification since the Late Miocene, often thought to be a major determinant of Neotropical diversity, had a limited imprint on spatial richness patterns at small grain sizes. Further application of our approach will help determine the role of the DRH in explaining current spatial patterns of species richness.Note to readersThis manuscript has been seen by a few researchers, some of whom suggested that before publishing our work in a peer-reviewed journal we should conduct simulations to demonstrate that our methods properly estimate the contribution of variance in diversification rates to spatial variation in species richness. Although we believe that our approach derives logically from theory and statistics and is therefore valid, we understand that it is rather unique and see why some readers would think that an independent validation is necessary. Unable to complete such validation in the near future, however, we decided to make this manuscript available as a preprint to share our ideas and hopefully stimulate discussion on what we believe is a most interesting topic. We also hope to receive feedback that may enable us to improve our work for publication in a journal at a later date.

scholarly journals Constant diversification rates of endemic gastropods in ancient Lake Ohrid: ecosystem resilience likely buffers environmental fluctuations

2015 ◽  
Vol 12 (16) ◽  
pp. 14271-14302 ◽  
Author(s):  
K. Föller ◽  
B. Stelbrink ◽  
T. Hauffe ◽  
C. Albrecht ◽  
T. Wilke
Keyword(s):  
Diversification Rate ◽  
Ancient Lakes ◽  
Freshwater Species ◽  
Ecosystem Resilience ◽  
Ancient Lake ◽  
Lake Ohrid ◽  
Deep Drilling ◽  
Diversification Rates ◽  
Environmental Events ◽  
Over Time

Abstract. Ancient lakes represent key ecosystems for endemic freshwater species. This high endemic biodiversity has been shown to be mainly the result of intra-lacustrine diversification. Whereas the principle role of this mode of diversification is generally acknowledged, actual diversification rates in ancient lakes remain little understood. At least four modes are conceivable. Diversification rates may be constant over time, they may fluctuate, rates may be higher in the initial phase of diversification, or there may be a pronounced lag phase between colonization and subsequent diversification. As understanding the tempo of diversification in ancient lake environments may help unrevealing the underlying processes that drive speciation and extinction, we here use the Balkan Lake Ohrid as a model system and the largest species flock in the lake, the non-pyrgulinid Hydrobiidae, as a model taxon to study changes in diversification rates over time together with the respective drivers. Based on phylogenetic, molecular-clock, lineage-through-time plot and diversification-rate analyses we found that this monophyletic group is comparatively old and that it most likely evolved with a constant diversification rate. Preliminary data of the SCOPSCO deep-drilling program do indicate signatures of severe environmental/climatic perturbations in Lake Ohrid. However, so far there is no evidence for the occurrence of catastrophic environmental events. We therefore propose that the rate homogeneity observed in endemic gastropods has been caused by two factors: (i) a potential lack of catastrophic environmental events in Lake Ohrid and/or (ii) a high ecosystem resilience, buffering environmental changes. Parameters potentially contributing to the lake's high ecosystem resilience are its distinct bathymetry, ongoing tectonic activities, and karst hydrology. The current study not only contributes to one of the overall goals of the SCOPSCO deep-drilling program – inferring the driving forces for biotic evolution in Lake Ohrid. It might also enhance our understanding of how ecosystem resilience, in general, may promote relative constant diversification rates in isolated ecosystems. However, we encourage future studies testing hypotheses about the lack of catastrophic events in Lake Ohrid. These studies should be based on high-resolution data for the entire geological history of the lake, and potentially involving information from the sediment fossil record, not only for gastropods but also for other groups with a high share of endemic taxa.

scholarly journals Quantifying the effects of the break up of Pangaea on global terrestrial diversification with neutral theory

2016 ◽  
Vol 371 (1691) ◽  
pp. 20150221 ◽  
Author(s):  
Sean M. R. Jordan ◽  
Timothy G. Barraclough ◽  
James Rosindell
Keyword(s):  
Species Richness ◽  
Fossil Record ◽  
Neutral Theory ◽  
Continental Drift ◽  
Geological Time ◽  
Ecological Processes ◽  
Diversification Rates ◽  
Higher Taxa ◽  
Break Up ◽  
Taxonomic Groups

The historic richness of most taxonomic groups increases substantially over geological time. Explanations for this fall broadly into two categories: bias in the fossil record and elevated net rates of diversification in recent periods. For example, the break up of Pangaea and isolation between continents might have increased net diversification rates. In this study, we investigate the effect on terrestrial diversification rates of the increased isolation between land masses brought about by continental drift. We use ecological neutral theory as a means to study geologically complex scenarios tractably. Our models show the effects of simulated geological events that affect all species equally, without the added complexity of further ecological processes. We find that continental drift leads to an increase in diversity only where isolation between continents leads to additional speciation through vicariance, and where higher taxa with very low global diversity are considered. We conclude that continental drift by itself is not sufficient to account for the increase in terrestrial species richness observed in the fossil record.

Community characteristics of forest understory birds along an elevational gradient in the Horn of Africa: A multi-year baseline

The Condor ◽  
2021 ◽  
Author(s):  
Kyle D Kittelberger ◽  
Montague H C Neate-Clegg ◽  
Evan R Buechley ◽  
Çağan Hakkı Şekercioğlu
Keyword(s):  
Species Richness ◽  
Species Turnover ◽  
Survival Rates ◽  
Elevational Gradient ◽  
Forest Understory ◽  
Bird Abundance ◽  
Tropical Mountains ◽  
Demographic Rates ◽  
Understory Birds ◽  
Over Time

Abstract Tropical mountains are global hotspots for birdlife. However, there is a dearth of baseline avifaunal data along elevational gradients, particularly in Africa, limiting our ability to observe and assess changes over time in tropical montane avian communities. In this study, we undertook a multi-year assessment of understory birds along a 1,750 m elevational gradient (1,430–3,186 m) in an Afrotropical moist evergreen montane forest within Ethiopia’s Bale Mountains. Analyzing 6 years of systematic bird-banding data from 5 sites, we describe the patterns of species richness, abundance, community composition, and demographic rates over space and time. We found bimodal patterns in observed and estimated species richness across the elevational gradient (peaking at 1,430 and 2,388 m), although no sites reached asymptotic species richness throughout the study. Species turnover was high across the gradient, though forested sites at mid-elevations resembled each other in species composition. We found significant variation across sites in bird abundance in some of the dietary and habitat guilds. However, we did not find any significant trends in species richness or guild abundances over time. For the majority of analyzed species, capture rates did not change over time and there were no changes in species’ mean elevations. Population growth rates, recruitment rates, and apparent survival rates averaged 1.02, 0.52, and 0.51 respectively, and there were no elevational patterns in demographic rates. This study establishes a multi-year baseline for Afrotropical birds along an elevational gradient in an under-studied international biodiversity hotspot. These data will be critical in assessing the long-term responses of tropical montane birdlife to climate change and habitat degradation.

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