Keeping it in the family: strong fine-scale genetic structure and inbreeding in Lodoicea maldivica, the largest-seeded plant in the world
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The fine-scale spatial genetic structure (FSGS) of plant populations is strongly influenced by patterns of seed dispersal. An extreme case of limited dispersal is found in the charismatic yet endangered palm Lodoicea maldivica, which produces large fruits (up to 20 kg) dispersed only by gravity. To investigate patterns of seed dispersal and FSGS in natural populations we sampled 1252 individual adults and regenerating offspring across the species’ natural range in the Seychelles archipelago, and characterised their genotypes at 12 microsatellite loci. The average dispersal distance was 8.7 ± 0.7 m. Topography had a significant effect on seed dispersal, with plants on steep slopes exhibiting the longest distances. FSGS was intense, especially in younger cohorts. Contrary to what might be expected in a dioecious species, we found high levels of inbreeding, with most neighbouring pairs of male and female trees (≤10 m) being closely related. Nonetheless, levels of genetic diversity were relatively high and similar in the various sampling areas, although these differed in disturbance and habitat fragmentation. We discuss potential trade-offs associated with maternal resource provisioning of progeny, seed dispersal and inbreeding, and consider the implications of our findings for managing this globally significant flagship species.
KeywordsCoco de mer Dioecy Fine-scale spatial genetic structure Inbreeding Limited seed dispersal Seychelles Islands
The authors thank the Seychelles Islands Foundation, Ravin de Fond Ferdinand Nature Reserve, Seychelles National Parks Authority, and GVI Seychelles for project support and permission to work in the Lodoicea forests. In particular Marc Jean-Baptiste, Wilna Accouche, Nancy Bunbury, Estephan Germain, Allen Cedras and Chris Mason-Parker for providing valuable advice and information, and facilitating field work. We also thank Gerry Rose and Fabio Lesperance who were invaluable field assistants, and Kirsti Määttänen for advice in the lab. Myriam Heuertz and three anonymous reviewers provided useful comments that allowed us to improve the manuscript. Permission to conduct research, and export of samples was approved by the Seychelles Bureau of Standards and the Ministry of Environment, Energy and Climate Change, respectively. Fragment analysis was conducted at the Genetic Diversity Centre (GDC), ETH Zürich. C.N.K.-B. received funding from the DFG (KA 3349/2-1).
This research was funded under grant number ETH-37 12-1 ETH, Zürich.
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