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Morphometric delimitation of Gnetum species in Africa

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Abstract

The economically important gymnosperm Gnetum L. is distributed in humid tropical forests of Africa. Its leaves are used as commercialized vegetables and greatly alleviate poverty for local people. Previously, the number of species recognized in Africa was uncertain, and Gnetum africanum Welw. and G. buchholzianum Engl. had been variously, and erroneously, applied to specimens. Based on recent morphological studies, species limits were clarified and two new African species, Gnetum interruptum E.H.Biye and G. latispicum E.H.Biye, were described. The purpose of this study was to determine species limits, to investigate potential infraspecific variation in wild African Gnetum species and to determine which features distinguish them in order to assess the validity of four species recognized by Biye et al. (Pl Syst Evol 300(2):263–272, 2014). Sixty-seven morphological characters were scored for a total of 175 (56 male and 119 female) specimens and analysed using cluster, principal components and principal coordinates analyses. Four distinct clusters of Gnetum specimens were recognized that correspond to the species now described as G. africanum, G. buchholzianum, G. interuptum and G. latispicum. A lack of geographical correlation with subclusters as well as their structure suggests there is no justification for recognizing infraspecific taxa. Characters that describe features of the spikes should be used to differentiate between and identify the species in Africa. In view of the high levels of utilization of two species and rarity of a third, it is urgent to assess the threat status of Gnetum species in Africa and to design appropriate conservation strategies to conserve these economically valuable plants.

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Acknowledgments

The authors express their thanks to the curators of the herbaria cited in Online Resource 1 and to partners of the Aluka initiative (http://www.aluka.org) for access to specimens and/or digital images of types. Our thanks also go to Donald McCallum for the graphics in Figs. 3, 4, 7 and 8. We are grateful for the support received from the University of the Witwatersrand, Johannesburg in South Africa, the University of Yaounde I in Cameroon and the various sponsors who provided the necessary travel grants. Financial supports from the National Research Foundation of South Africa (Grant Numbers 65704 to K Balkwill and 62060 to GV Cron) and the University of the Witwatersrand are gratefully acknowledged.

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Authors and Affiliations

  1. School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, Johannesburg, Wits 2050, South Africa

    Elvire H. Biye, Glynis V. Cron & Kevin Balkwill

  2. Plant Biology Department, Faculty of Science, University of Yaoundé I, PO Box 812, Johannesburg, South Africa

    Elvire H. Biye

Authors
  1. Elvire H. Biye
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  2. Glynis V. Cron
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  3. Kevin Balkwill
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Correspondence to Elvire H. Biye.

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Handling editor: Karol Marhold.

Information on Electronic Supplementary Material

Information on Electronic Supplementary Material

Information on Electronic Supplementary Material

Online Resource 1. List of voucher specimens of Gnetum examined in the phenetic study arranged in order of identification number for male and then female specimens.

Online Resource 2. Eigen vectors for the first three axes resulting from ordination of the characters for interpretation of the PCO analysis of the female Gnetum specimens.

Online Resource 3. Eigen vectors for the first three axes resulting from ordination of the characters for interpretation of the PCO analysis of the female Gnetum specimens.

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Biye, E.H., Cron, G.V. & Balkwill, K. Morphometric delimitation of Gnetum species in Africa. Plant Syst Evol 302, 1067–1082 (2016). https://doi.org/10.1007/s00606-016-1317-3

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