Patterns of Species Ranges, Speciation, and Extinction

Birand, Aysegul
Vose, Aaron
Gavrilets, Sergey
The exact nature of the relationship among species range sizes, speciation, and extinction events is not well understood. The factors that promote larger ranges, such as broad niche widths and high dispersal abilities, could increase the likelihood of encountering new habitats but also prevent local adaptation due to high gene flow. Similarly, low dispersal abilities or narrower niche widths could cause populations to be isolated, but such populations may lack advantageous mutations due to low population sizes. Here we present a large-scale, spatially explicit, individual-based model addressing the relationships between species ranges, speciation, and extinction. We followed the evolutionary dynamics of hundreds of thousands of diploid individuals for 200,000 generations. Individuals adapted to multiple resources and formed ecological species in a multidimensional trait space. These species varied in niche widths, and we observed the coexistence of generalists and specialists on a few resources. Our model shows that species ranges correlate with dispersal abilities but do not change with the strength of fitness trade-offs; however, high dispersal abilities and low resource utilization costs, which favored broad niche widths, have a strong negative effect on speciation rates. An unexpected result of our model is the strong effect of underlying resource distributions on speciation: in highly fragmented landscapes, speciation rates are reduced.


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Divergence of gene expression is known to contribute to the differentiation and separation of populations and species, although the dynamics of this process in early stages of population divergence remains unclear. We analyzed gene expression differences in three organs (brain, liver, and testis) between two natural populations of Mus musculus domesticus that have been separated for at most 3000years. We used two different microarray platforms to corroborate the results at a large scale and identified hundr...
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Effective population size is a crucial concept of conservation biology. It is reduced by biased sex ratio, consequently causing loss of genetic variation. To evaluate genetic diversity related to gender, and investigate the possible effects of biased sex ratio, we analyzed available microsatellite DNA markers from 120 samples of Populus nigra L. (European black poplar) originating from five geographical regions in Turkey. Using 12 microsatellite markers, we detected 60 clones of the same genotype, out of 12...
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High levels of genetic diversity and connectivity are crucial for the persistence of local populations, especially at the edge of species' distribution ranges. Here, we assessed the potential and realized connectivity of populations of the Mediterranean seagrass Posidonia oceanica at its easternmost distribution using physical modelling and genetic analyses. Genetic assessments of diversity and gene flow among populations were carried out with 18 microsatellite loci, while oceanographic connectivity was ass...
Determinants of phytoplankton size structure in warm, shallow lakes
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Body size is an important trait of any organism, including phytoplankton, because it affects physiological and morphological performance, reproduction, population growth rate and competitive interactions. Understanding how interacting top-down and bottom-up factors influence phytoplankton cell size in different aquatic environments is still a challenge. Structural equation modeling (SEM) is a comprehensive multivariate statistical tool for detecting cause-effect relationship among different variables and th...
Strong population structure in a species manipulated by humans since the Neolithic: the European fallow deer (Dama dama dama)
Baker, K. H.; Gray, H. W. I.; Ramovs, V.; Mertzanidou, D.; AKIN PEKŞEN, Çiğdem; Bilgin, Cemal Can; Sykes, N.; Hoelzel, A. R. (2017-07-01)
Species that have been translocated and otherwise manipulated by humans may show patterns of population structure that reflect those interactions. At the same time, natural processes shape populations, including behavioural characteristics like dispersal potential and breeding system. In Europe, a key factor is the geography and history of climate change through the Pleistocene. During glacial maxima throughout that period, species in Europe with temperate distributions were forced south, becoming distribut...
Citation Formats
A. Birand, A. Vose, and S. Gavrilets, “Patterns of Species Ranges, Speciation, and Extinction,” AMERICAN NATURALIST, pp. 1–21, 2012, Accessed: 00, 2020. [Online]. Available: