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The role of hummingbirds in the evolution and diversification of Bromeliaceae: unsupported claims and untested hypotheses


Kessler, Michael; Abrahamczyk, Stefan; Krömer, Thorsten (2020). The role of hummingbirds in the evolution and diversification of Bromeliaceae: unsupported claims and untested hypotheses. Botanical Journal of the Linnean Society, 192(4):592-608.

Abstract

At least half of the 3600 species of Bromeliaceae are pollinated by hummingbirds. There is little doubt that the four to 12 evolutionary shifts towards and c. 32 shifts away from hummingbird pollination opened new evolutionary spaces for bromeliad diversification, and that hummingbird pollination has led to increased bromeliad diversification rates. However, the mechanisms leading to these increased rates remain unclear. We here propose that there are four main types of mechanisms that may increase diversification rates of hummingbird-pollinated bromeliad clades: (1) bromeliad speciation through adaptation to different hummingbird species; (2) increased allopatric speciation in hummingbird-pollinated clades due to lower pollen transfer efficiency compared with other pollinators; (3) differential speciation rates in hummingbird-pollinated clades dependent on of flowering phenology and hummingbird behaviour; and (4) higher speciation rates of bromeliads in montane environments (where hummingbird pollination predominates) due to topographic population fragmentation. To date, none of these hypotheses has been appropriately tested, partly due to a lack of data, but also because research so far has focused on documenting the pattern of increased diversification in hummingbird-pollinated clades, implicitly assuming that this pattern supports an underlying mechanism while ignoring the fact that several competing mechanisms may be considered. The aim of the present review is to increase awareness of these mechanisms and to trigger research aimed at specifically testing them. We conclude that much additional research on the roles of hummingbird behaviour and gene flow between bromeliad species is needed to elucidate their contribution to the evolution of diversity in bromeliads and other plant families.

Abstract

At least half of the 3600 species of Bromeliaceae are pollinated by hummingbirds. There is little doubt that the four to 12 evolutionary shifts towards and c. 32 shifts away from hummingbird pollination opened new evolutionary spaces for bromeliad diversification, and that hummingbird pollination has led to increased bromeliad diversification rates. However, the mechanisms leading to these increased rates remain unclear. We here propose that there are four main types of mechanisms that may increase diversification rates of hummingbird-pollinated bromeliad clades: (1) bromeliad speciation through adaptation to different hummingbird species; (2) increased allopatric speciation in hummingbird-pollinated clades due to lower pollen transfer efficiency compared with other pollinators; (3) differential speciation rates in hummingbird-pollinated clades dependent on of flowering phenology and hummingbird behaviour; and (4) higher speciation rates of bromeliads in montane environments (where hummingbird pollination predominates) due to topographic population fragmentation. To date, none of these hypotheses has been appropriately tested, partly due to a lack of data, but also because research so far has focused on documenting the pattern of increased diversification in hummingbird-pollinated clades, implicitly assuming that this pattern supports an underlying mechanism while ignoring the fact that several competing mechanisms may be considered. The aim of the present review is to increase awareness of these mechanisms and to trigger research aimed at specifically testing them. We conclude that much additional research on the roles of hummingbird behaviour and gene flow between bromeliad species is needed to elucidate their contribution to the evolution of diversity in bromeliads and other plant families.

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Additional indexing

Item Type:Journal Article, refereed, further contribution
Communities & Collections:07 Faculty of Science > Department of Systematic and Evolutionary Botany
07 Faculty of Science > Zurich-Basel Plant Science Center
Dewey Decimal Classification:580 Plants (Botany)
Uncontrolled Keywords:Plant Science, Ecology, Evolution, Behavior and Systematics
Language:English
Date:27 March 2020
Deposited On:13 Jan 2020 11:35
Last Modified:28 Mar 2020 02:04
Publisher:Wiley-Blackwell Publishing, Inc.
ISSN:0024-4074
OA Status:Closed
Publisher DOI:https://doi.org/10.1093/botlinnean/boz100

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