Founder takes all: density-dependent processes structure biodiversity Jonathan M. Waters, Ceridwen I. Fraser, Godfrey M. Hewitt  Trends in Ecology & Evolution  Volume 28, Issue 2, Pages 78-85 (February 2013) DOI: 10.1016/j.tree.2012.08.024 Copyright © 2012 Elsevier Ltd Terms and Conditions

Figure 1 Rapid expansion of founding lineages effectively blocks establishment of latecomers. Different colors represent different genetic lineages. Populations founded by those first able to disperse into new territory can rapidly expand, hindering establishment of later immigrants and leading to a relative lack of genetic diversity in the newer populations. Trends in Ecology & Evolution 2013 28, 78-85DOI: (10.1016/j.tree.2012.08.024) Copyright © 2012 Elsevier Ltd Terms and Conditions

Figure 2 Density-dependent processes operate on various scales. The ‘founder takes all’ principle can explain various biological processes on a range of scales, such as sectoring in microbial cultures, island chain colonization, and postglacial recolonization of continents. (a) Microbial sectoring: when bacterial and yeast colonies are grown from an experimental application of two initially well-mixed lineages to the center of an agar plate; lineage sectoring occurs as the first lineage to colonize outwards rapidly multiplies in all unoccupied directions [4]. (b) Postglacial recolonization can similarly lead to sectoring of lineages as dispersal into newly available habitat (with poleward recession of glaciers) occurs in all unoccupied directions from leading-edge colonists leaving glacial refugia, and rapid increases in population density prevent colonization by latecomers. This example illustrates sectoring by four main mitochondrial lineages in two species of European hedgehog dispersing from southern refugia after the Last Glacial Maximum (LGM); similar patterns of sectored expansion from glacial refugia have been observed in a wide range of taxa (e.g., [17]) in Europe, North America, and the Southern Hemisphere. Colored hedgehog symbols indicate the known locations of hedgehog populations at various times based on either dated subfossil remains (upper two panels, [69]) or mtDNA samples (lower panel, [18,19]). (c) Taxa inhabiting volcanic island chains, such as Hawaii, have been observed to show phylogeographic patterns consistent with timing of island formation, with older lineages on older islands (the ‘progression rule’). Rapid establishment of the first lineage to arrive at a new island hinders establishment of latecomers. White arrows indicate successful dispersal and establishment; gray arrows represent failed dispersal events; and the phylogenetic tree in the bottom panel schematically illustrates relationships among lineages. Abbreviation: ka, 1000 years ago. Trends in Ecology & Evolution 2013 28, 78-85DOI: (10.1016/j.tree.2012.08.024) Copyright © 2012 Elsevier Ltd Terms and Conditions

Figure I High-density blocking by established populations. This example illustrates how density-dependent processes operate in southern bull-kelp (Durvillaea antarctica) populations. Inset photograph of detached kelp reproduced, with permission, from Martin Thiel. Trends in Ecology & Evolution 2013 28, 78-85DOI: (10.1016/j.tree.2012.08.024) Copyright © 2012 Elsevier Ltd Terms and Conditions