Many marine and terrestrial clades show similar latitudinal gradients in species richness, but opposite gradients in range size—on land, ranges are the smallest in the tropics, whereas in the sea, ranges are the largest in the tropics. Therefore, richness gradients in marine and terrestrial systems do not arise from a shared latitudinal arrangement of species range sizes. Comparing terrestrial birds and marine bivalves, we find that gradients in range size are concordant at the level of genera. Here, both groups show a nested pattern in which narrow-ranging genera are confined to the tropics and broad-ranging genera extend across much of the gradient. We find that (i) genus range size and its variation with latitude is closely associated with per-genus species richness and (ii) broad-ranging genera contain more species both within and outside of the tropics when compared with tropical- or temperate-only genera. Within-genus species diversification thus promotes genus expansion to novel latitudes. Despite underlying differences in the species range-size gradients, species-rich genera are more likely to produce a descendant that extends its range relative to the ancestor's range. These results unify species richness gradients with those of genera, implying that birds and bivalves share similar latitudinal dynamics in net species diversification.
Latitudinal range limits of birds at global scales
Latitudinal range limits of bird genera and species at global scales defined on the basis of 2,785,600 occurrences from published literature, sightings, and from museum specimens (Rahbek and Graves 2001; Rahbek et al. 2012). Ranges were compiled at a resolution of 1° x 1°. References: Rahbek, C. & Graves, G. R. 2001 Multiscale assessment of patterns of avian species richness. Proc. Natl. Acad. Sci. USA 98, 4534-4539. Rahbek, C., Hansen, L. A. & Fjelds, J. 2012. One degree resolution database of the global distribution of birds. Natural History Museum of Denmark, University of Copenhagen, Denmark.
Global bird range limits.xls
Latitudinal range limits of birds in the New World
Latitudinal range limits of bird genera and species in the New World defined on the basis of occurrences from published literature, sightings, and from museum specimens (Rahbek and Graves 2001; Rahbek et al. 2012). Ranges were compiled at a resolution of 1° x 1°. References: Rahbek, C. & Graves, G. R. 2001 Multiscale assessment of patterns of avian species richness. Proc. Natl. Acad. Sci. USA 98, 4534-4539. Rahbek, C., Hansen, L. A. & Fjelds, J. 2012. One degree resolution database of the global distribution of birds. Natural History Museum of Denmark, University of Copenhagen, Denmark.
New World bird range limits.xls
Latitudinal range limits of bivalves at global scales
Latitudinal range limits of bivalve genera and species at global scales, occurring at depths < 200 m. They were compiled from both the literature and museum collections. Reference: Jablonski, D., Belanger, C. L., Berke, S. K., Huang, S., Krug, A. Z., Roy, K., Tomasovych, A. & Valentine, J. W. 2013 Out of the tropics, but how? Fossils, bridge species, and thermal ranges in the dynamics of the marine latitudinal diversity gradient. Proc. Natl. Acad. Sci. USA 110, 10487-10494.
Global bivalve range limits.xls
Latitudinal range limits of bivalves in the Eastern Pacific
Latitudinal range limits of bivalve genera and species in the Eastern Pacific, occurring at depths < 200 m. They were compiled from both the literature and museum collections. Reference: Jablonski, D., Belanger, C. L., Berke, S. K., Huang, S., Krug, A. Z., Roy, K., Tomasovych, A. & Valentine, J. W. 2013 Out of the tropics, but how? Fossils, bridge species, and thermal ranges in the dynamics of the marine latitudinal diversity gradient. Proc. Natl. Acad. Sci. USA 110, 10487-10494.
Eastern Pacific bivalve range limits.xls
Latitudinal range limits of bivalves in the Western Atlantic
Latitudinal range limits of bivalve genera and species in the Western Atlantic, occurring at depths < 200 m. They were compiled from both the literature and museum collections. Reference: Jablonski, D., Belanger, C. L., Berke, S. K., Huang, S., Krug, A. Z., Roy, K., Tomasovych, A. & Valentine, J. W. 2013 Out of the tropics, but how? Fossils, bridge species, and thermal ranges in the dynamics of the marine latitudinal diversity gradient. Proc. Natl. Acad. Sci. USA 110, 10487-10494.
Western Atlantic bivalve range limits.xls