1. Department of Zoology, University of Hawaii at Manoa, Honolulu, Hawaii 96822, USA
2. School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand

Correspondence to: Tadashi Fukami¹ Correspondence and requests for materials should be addressed to T.F. (Email: tfukami@hawaii.edu).

Abstract

Diversity in biological communities is a historical product of immigration, diversification and extinction^{1, 2, 3, 4}, but the combined effect of these processes is poorly understood. Here we show that the order and timing of immigration controls the extent of diversification. When an ancestral bacterial genotype was introduced into a spatially structured habitat, it rapidly diversified into multiple niche-specialist types⁵. However, diversification was suppressed when a niche-specialist type was introduced before, or shortly after, introduction of the ancestral genotype. In contrast, little suppression occurred when the same niche specialist was introduced relatively late. The negative impact of early arriving immigrants was attributable to the historically sensitive outcome of interactions involving neutral competition³ and indirect facilitation. Ultimately, the entire boom-and-bust dynamics of adaptive radiation were altered. These results demonstrate that immigration and diversification are tightly linked processes, with small differences in immigration history greatly affecting the evolutionary emergence of diversity.

1. Department of Zoology, University of Hawaii at Manoa, Honolulu, Hawaii 96822, USA
2. School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand

Correspondence to: Tadashi Fukami¹ Correspondence and requests for materials should be addressed to T.F. (Email: tfukami@hawaii.edu).

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