Avian Diversity (1 Viewer)

Joseph A. Tobias, Jente Ottenburghs & Alex L. Pigot, 2020

Avian Diversity: Speciation, Macroevolution, and Ecological Function

Annual Review of Ecology, Evolution, and Systematics 51 (advance online publication)
doi: https://doi.org/10.1146/annurev-ecolsys-110218-025023
https://www.annualreviews.org/doi/abs/10.1146/annurev-ecolsys-110218-025023

Abstract


The origin, distribution, and function of biological diversity are fundamental themes of ecology and evolutionary biology. Research on birds has played a major role in the history and development of these ideas, yet progress was for many decades limited by a focus on patterns of current diversity, often restricted to particular clades or regions. Deeper insight is now emerging from a recent wave of integrative studies combining comprehensive phylogenetic, environmental, and functional trait data at unprecedented scales. We review these empirical advances and describe how they are reshaping our understanding of global patterns of bird diversity and the processes by which it arises, with implications for avian biogeography and functional ecology. Further expansion and integration of data sets may help to resolve longstanding debates about the evolutionary origins of biodiversity and offer a framework for understanding and predicting the response of ecosystems to environmental change.

Enjoy,

Fred

Fig. 1. The speciation cycle in birds. Starting with a parent species (top middle blue oval), ( 1 ) populations become spatially separated by geographic barriers (vicariance) or dispersal (peripatry), then ( 2 ) geographic isolates form incipient species, after which the cycle can proceed along two alternative routes. In ( 3 ), lineages continue to diverge in allopatry until reproductively isolated. After range expansion, these species later achieve secondary contact ( 4 ), eventually followed by transition to widespread secondary sympatry ( 5 ). This final stage requires divergence in species ecological niches either prior to contact (ecological sorting) or upon contact (ecological character displacement). In the alternative route, incipient species disperse and come back into secondary contact before they are reproductively isolated ( 6 ). Incipient species may undergo reproductive character displacement (reinforcement) resulting in the transition to widespread sympatry ( 7 ). Once species attain widespread sympatry, the cycle is completed, initiating two new cycles of the process. Embedded within the full speciation cycle is a faster (ephemeral) speciation cycle ( 1 → 2 → 8  or 1 → 2 → 6 → 9 ) that does not lead to an increase in species richness. In this cycle, incipient species are rapidly formed but then aborted either because of stochastic extinction events ( 8 , marked with a red ×) or high rates of gene flow (hybridization) upon secondary contact ( 9 ), causing them to merge back into a single population. Note that populations can stall at the secondary contact phase ( 6 ) if parapatry is maintained by hybridization. Also note that most steps in the cycle are reversible (bidirectional). The outer rings illustrate various types of research input and the stage of the cycle to which they are most relevant, highlighting new technologies, data sets, and potential applications.

Fred