Limits...
An engine for global plant diversity: highest evolutionary turnover and emigration in the American tropics.

Antonelli A, Zizka A, Silvestro D, Scharn R, Cascales-Miñana B, Bacon CD - Front Genet (2015)

Bottom Line: Our results, based on the analysis of c. 22,600 species and c. 20 million geo-referenced occurrence records, show no significant differences between the speciation and extinction of tropical and non-tropical angiosperms.In contrast, the outstanding species richness found today in the American tropics (the Neotropics), as compared to tropical Africa and tropical Asia, is associated with significantly higher speciation and extinction rates.These results imply that the Neotropics have acted as an engine for global plant diversity.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological and Environmental Sciences, University of Gothenburg Göteborg, Sweden ; Gothenburg Botanical Garden Göteborg, Sweden.

ABSTRACT
Understanding the processes that have generated the latitudinal biodiversity gradient and the continental differences in tropical biodiversity remains a major goal of evolutionary biology. Here we estimate the timing and direction of range shifts of extant flowering plants (angiosperms) between tropical and non-tropical zones, and into and out of the major tropical regions of the world. We then calculate rates of speciation and extinction taking into account incomplete taxonomic sampling. We use a recently published fossil calibrated phylogeny and apply novel bioinformatic tools to code species into user-defined polygons. We reconstruct biogeographic history using stochastic character mapping to compute relative numbers of range shifts in proportion to the number of available lineages through time. Our results, based on the analysis of c. 22,600 species and c. 20 million geo-referenced occurrence records, show no significant differences between the speciation and extinction of tropical and non-tropical angiosperms. This suggests that at least in plants, the latitudinal biodiversity gradient primarily derives from other factors than differential rates of diversification. In contrast, the outstanding species richness found today in the American tropics (the Neotropics), as compared to tropical Africa and tropical Asia, is associated with significantly higher speciation and extinction rates. This suggests an exceedingly rapid evolutionary turnover, i.e., Neotropical species being formed and replaced by one another at unparalleled rates. In addition, tropical America stands out from other continents by having "pumped out" more species than it received through most of the last 66 million years. These results imply that the Neotropics have acted as an engine for global plant diversity.

No MeSH data available.


The four regions (operational units) used in this study. Tropical regions are shown in red (dark red: rain forests, light red: savannas), non-tropical regions are shown in blue. Dots indicate species occurrence records of angiosperms (c. 20 million) used in this study and obtained from the Global Biodiversity Information Facility (GBIF).
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Figure 2: The four regions (operational units) used in this study. Tropical regions are shown in red (dark red: rain forests, light red: savannas), non-tropical regions are shown in blue. Dots indicate species occurrence records of angiosperms (c. 20 million) used in this study and obtained from the Global Biodiversity Information Facility (GBIF).

Mentions: We coded each species for its presence and absence in four large regions or operational units (Figure 2): tropical America (the Neotropics), tropical Africa (the Afrotropics), tropical Asia (including Australasia), and all other (non-tropical) regions combined. We delimited those regions by following the same boundaries for biomes and ecoregions as adopted by the World Wide Fund for Nature (WWF), as described in Olson et al. (2001). We considered the following ecoregions as forming together the tropical region: “Tropical and Subtropical Moist Broadleaf Forests,” “Tropical and Subtropical Dry Broadleaf Forests,” “Tropical and Subtropical Coniferous Forests” and “Tropical and Subtropical Grasslands, Savannas, and Shrublands.” All other ecoregions were merged to form our “non-tropical” region. We classified “Flooded Grasslands and Shrublands” as tropical or non-tropical depending on the surrounding biome and geographic position. We acknowledge that the WWF biome and ecoregion classification is to some extent arbitrary and based on expert opinion, rather than directly data derived (Vilhena and Antonelli, 2014). However, we consider that the level of accuracy of this classification is adequate for the purposes of this study, and superior to a classification based solely on latitudinal limits or a purely climatic classification without proper consideration of biotic components (Kottek et al., 2006).


An engine for global plant diversity: highest evolutionary turnover and emigration in the American tropics.

Antonelli A, Zizka A, Silvestro D, Scharn R, Cascales-Miñana B, Bacon CD - Front Genet (2015)

The four regions (operational units) used in this study. Tropical regions are shown in red (dark red: rain forests, light red: savannas), non-tropical regions are shown in blue. Dots indicate species occurrence records of angiosperms (c. 20 million) used in this study and obtained from the Global Biodiversity Information Facility (GBIF).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4389561&req=5

Figure 2: The four regions (operational units) used in this study. Tropical regions are shown in red (dark red: rain forests, light red: savannas), non-tropical regions are shown in blue. Dots indicate species occurrence records of angiosperms (c. 20 million) used in this study and obtained from the Global Biodiversity Information Facility (GBIF).
Mentions: We coded each species for its presence and absence in four large regions or operational units (Figure 2): tropical America (the Neotropics), tropical Africa (the Afrotropics), tropical Asia (including Australasia), and all other (non-tropical) regions combined. We delimited those regions by following the same boundaries for biomes and ecoregions as adopted by the World Wide Fund for Nature (WWF), as described in Olson et al. (2001). We considered the following ecoregions as forming together the tropical region: “Tropical and Subtropical Moist Broadleaf Forests,” “Tropical and Subtropical Dry Broadleaf Forests,” “Tropical and Subtropical Coniferous Forests” and “Tropical and Subtropical Grasslands, Savannas, and Shrublands.” All other ecoregions were merged to form our “non-tropical” region. We classified “Flooded Grasslands and Shrublands” as tropical or non-tropical depending on the surrounding biome and geographic position. We acknowledge that the WWF biome and ecoregion classification is to some extent arbitrary and based on expert opinion, rather than directly data derived (Vilhena and Antonelli, 2014). However, we consider that the level of accuracy of this classification is adequate for the purposes of this study, and superior to a classification based solely on latitudinal limits or a purely climatic classification without proper consideration of biotic components (Kottek et al., 2006).

Bottom Line: Our results, based on the analysis of c. 22,600 species and c. 20 million geo-referenced occurrence records, show no significant differences between the speciation and extinction of tropical and non-tropical angiosperms.In contrast, the outstanding species richness found today in the American tropics (the Neotropics), as compared to tropical Africa and tropical Asia, is associated with significantly higher speciation and extinction rates.These results imply that the Neotropics have acted as an engine for global plant diversity.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological and Environmental Sciences, University of Gothenburg Göteborg, Sweden ; Gothenburg Botanical Garden Göteborg, Sweden.

ABSTRACT
Understanding the processes that have generated the latitudinal biodiversity gradient and the continental differences in tropical biodiversity remains a major goal of evolutionary biology. Here we estimate the timing and direction of range shifts of extant flowering plants (angiosperms) between tropical and non-tropical zones, and into and out of the major tropical regions of the world. We then calculate rates of speciation and extinction taking into account incomplete taxonomic sampling. We use a recently published fossil calibrated phylogeny and apply novel bioinformatic tools to code species into user-defined polygons. We reconstruct biogeographic history using stochastic character mapping to compute relative numbers of range shifts in proportion to the number of available lineages through time. Our results, based on the analysis of c. 22,600 species and c. 20 million geo-referenced occurrence records, show no significant differences between the speciation and extinction of tropical and non-tropical angiosperms. This suggests that at least in plants, the latitudinal biodiversity gradient primarily derives from other factors than differential rates of diversification. In contrast, the outstanding species richness found today in the American tropics (the Neotropics), as compared to tropical Africa and tropical Asia, is associated with significantly higher speciation and extinction rates. This suggests an exceedingly rapid evolutionary turnover, i.e., Neotropical species being formed and replaced by one another at unparalleled rates. In addition, tropical America stands out from other continents by having "pumped out" more species than it received through most of the last 66 million years. These results imply that the Neotropics have acted as an engine for global plant diversity.

No MeSH data available.