© 2016 The Linnean Society of London, Botanical Journal of the Linnean Society, 2017, 183, 106–123 106 Botanical Journal of the Linnean Society, 2017, 183, 106–123. With 6 figures How is genetic variability in the threatened rainforest vine Marsdenia longiloba distributed at different geographical scales? ALISON SHAPCOTT 1 *, ROBERT LAMONT 1 , KATIE O’CONNOR 1 , HEATHER JAMES 1 and ANDREW BENWELL 2 1 Faculty of Science, Health, Education and Engineering, Genecology Research Centre, University Sunshine Coast, Maroochydore, DC 4558 Qld, Australia 2 ECOS Environmental Pty Ltd, New Brighton, 2483 NSW, Australia Received 17 May 2016; revised 14 July 2016; accepted for publication 2 September 2016 Genetic analysis of rainforest vines has seldom been undertaken. Thus the genetic implications of habitat fragmentation are largely unknown, making guidance for conservation, recovery and translocations of threatened rainforest vines unpredictable. The threatened rainforest vine Marsdenia longiloba (Apocynaceae) has potentially been impacted by development and habitat fragmentation. This Australian species has rarely been observed to reproduce sexually leading to ambiguity in field identification and it was thought populations may be largely clonal. Genetic analysis was undertaken to clarify field identification, examine patterns of genetic variability and related aspects of its breeding system and identify patterns of genetic variation within and between populations of M. longiloba across the range of the species. Genetic variability was examined at fine, medium and broad geographical scales. The combination of DNA barcoding and microsatellite analysis has resolved potential species misidentifications in the field collections. Genetic analysis indicated that M. longiloba is not genetically depauperate and that larger populations contain more genetic diversity than smaller ones. Populations were not primarily composed of clones, although partial clonal structuring was detected especially in the southern part of its distribution. There was evidence of genetic clustering of plants at a medium landscape scale, but little evidence of broad regional genetic differences. © 2016 The Linnean Society of London, Botanical Journal of the Linnean Society, 2016 ADDITIONAL KEYWORDS: Apocynaceae – Asclepiadoideae – conservation genetics – DNA barcoding – endangered species. INTRODUCTION Little information is known about the impacts of fragmentation on threatened rainforest vines or the distribution of their genetic diversity (Schnitzer & Carson, 2001; Arnold & Rossetto, 2002; Putz, 2012). Vines form an important floristic and structural ele- ment in rainforest and adjacent moist open forest. Species vary in size from relatively small species like Marsdenia longiloba Benth. to large vine curtain species that play a key structural role in mesic forest ecosystems. Vines play a role in the protection of for- est edges from damaging external factors such as wind, light, weeds and disease and often play impor- tant roles during forest succession after natural and anthropogenic disturbances (Wiens, Crawford & Gosz, 1985; Schnitzer & Carson, 2001; Putz, 2012). Vines are also often implicated in structural deterio- ration in fragmented forests (Laurance et al., 2001; Putz, 2012), but some vines are sparsely distributed. Studies have suggested that internal fragmentation and proximity to patch edges may be more signifi- cant than landscape-level features of fragmentation for epiphyte and vine abundance in rainforest sys- tems (Magrach, Larrinaga & Santamar  ıa, 2012). Despite having been extensively fragmented, the region extending across the eastern border between New South Wales (NSW) and Queensland (Qld) Aus- tralia is important for biodiversity conservation with > 50 endemic genera found in this region (Lott & Duggin, 1993; Arnold & Rossetto, 2002). The forest *Corresponding author. E-mail: ashapcot@usc.edu.au Downloaded from https://academic.oup.com/botlinnean/article-abstract/183/1/106/2857494 by guest on 12 June 2020