Identification of Apocynaceae climbers in the Sangha Trinational, Central Africa Melanie Bayo August 2020 Thesis submitted in partial fulfilment for the MSc in the Biodiversity and Taxonomy of Plants 2 Abstract Apocynaceae climbers are easy to distinguish from other plant families due to the white latex and the opposite leaves. Identification at lower taxon levels, however, is more difficult as fertile material is rarely available in the field. This study aimed to facilitate the identification of Apoc- ynaceae climbers in the Sangha Trinational, Central Africa. For this, a morphological study on 42 species was conducted by examining digital specimens from across their distribution. An identification key to the species based on sterile characters is presented. Results showed that Apocynaceae climbers can be grouped based on sterile traits, however, for a few species, de- limitation without fertile characters has proved to be difficult. The key is the first of that kind to be produced for central African Apocynaceae climbers, yet it needs to be subject to further revision and testing. Secondly, this study aimed to assess the utility of rbcL as barcode marker for plants of the Sangha Trinational. For this, 87 rbcL sequences of 50 species in 28 families were subjected to two BLAST searches. Results showed that rbcL performs well at discriminating families (97 % identification matches) and is satisfactory at genus-level (77 %). Potentials and perils of DNA barcoding for identification are discussed. Keywords: Apocynaceae, identification key, DNA barcoding, rbcL, Sangha Trinational 3 Acknowledgements I would first like to thank my principal supervisor Dr David Harris for his invaluable support, guidance and motivating words throughout the project. I would also like to thank my supervi- sors Dr Laura Forrest and Dr Michelle Hart for their expertise and input on DNA barcoding. Thanks to Hannah Atkins and Dr Colin Pendry for testing the identification key. Special thanks to my fellow students at RBGE for their friendship throughout the year. And last but not least, thanks to my family for their support during my studies and beyond. 4 Contents Abstract ..................................................................................................................................... 2 Acknowledgements ................................................................................................................... 3 List of Figures ........................................................................................................................... 7 List of Tables ............................................................................................................................. 8 Index of abbreviations ............................................................................................................. 8 1 Introduction ....................................................................................................................... 9 1.1 Introduction to Apocynaceae Jussieu .................................................................................. 9 1.2 Introduction to tropical climbers ......................................................................................... 9 1.3 Identification of Apocynaceae climbers ............................................................................ 10 1.3.1 Morphological identification ................................................................................... 10 1.3.2 Molecular identification: DNA barcoding ............................................................... 10 1.4 Aims of the study .............................................................................................................. 10 2 Assembling data and information on Apocynaceae climbers in the Sangha Trinational .............................................................................................................................. 11 2.1 Materials and Methods ................................................................................................... 11 2.1.1 Study area ................................................................................................................ 11 2.1.2 Sangha Trinational dataset ....................................................................................... 12 2.1.3 RAINBIO dataset ..................................................................................................... 14 2.2 Results .............................................................................................................................. 16 2.2.1 Study species from the Sangha Trinational without occurrences in the RAINBIO dataset ................................................................................................................................ 16 2.2.2 Expected species in the Sangha Trinational ............................................................ 18 2.3 Discussion ......................................................................................................................... 22 2.3.1 Input data ................................................................................................................. 22 2.3.2 Selection of study species ........................................................................................ 23 2.3.3 Expected species in the Sangha Trinational ............................................................ 23 5 3 Morphological identification .......................................................................................... 24 3.1 Introduction ..................................................................................................................... 24 3.2 Materials and Methods ................................................................................................... 24 3.2.1 Herbarium specimens studied .................................................................................. 24 3.2.2 Character examination ............................................................................................. 25 3.2.3 Key building ............................................................................................................ 26 3.3 Results .............................................................................................................................. 26 3.3.1 Characters examined ................................................................................................ 26 3.3.2 Key to Apocynaceae climbers in the Sangha Trinational ........................................ 32 3.3.3 Sample species descriptions of Saba comorensis and Oncinotis tenuiloba ............. 36 3.4 Discussion ......................................................................................................................... 40 3.4.1 Character scoring ..................................................................................................... 40 3.4.2 Identification key ..................................................................................................... 40 3.4.3 Problematic names ................................................................................................... 42 4 The potential of DNA barcoding for identification ...................................................... 43 4.1 Introduction ..................................................................................................................... 43 4.1.1 The concept of DNA barcoding ............................................................................... 43 4.1.2 Use of DNA barcoding for plant identification ....................................................... 44 4.1.3 DNA barcoding in Apocynaceae ............................................................................. 45 4.1.4 Aim .......................................................................................................................... 46 4.2 Materials and Methods ................................................................................................... 46 4.2.1 Input data ................................................................................................................. 46 4.2.2 DNA sequence analysis ........................................................................................... 47 4.2.3 rbcL identification ................................................................................................... 47 4.3 Results .............................................................................................................................. 48 4.3.1 Sequences ................................................................................................................ 48 4.3.2 Similarity values of BLAST results ......................................................................... 50 6 4.3.3 Family ...................................................................................................................... 50 4.3.4 Genus ....................................................................................................................... 50 4.3.5 Species ..................................................................................................................... 54 4.4 Discussion ......................................................................................................................... 54 4.4.1 Sequence quality ...................................................................................................... 54 4.4.2 Reference databases ................................................................................................