Isotropic and anisotropic processes influence fine-scale spatial genetic structure of a keystone tropical plant. Issue 1 (6th January 2018)

• Record Type: Journal Article
• Authors: Geremew, Addisie; Woldemariam, Melkamu G; Kefalew, Alemayehu; Stiers, Iris; Triest, Ludwig
• Is Part Of: AoB plants. Volume 10:Issue 1(2018)
• Publication Date: 2018-01-06
• Subjects: Anemochory -- anisotropic -- fine-scale spatial genetic structure -- isotropic -- papyrus -- parentage analysis; Plants -- Periodicals; Botany -- Periodicals; 580.5
• DOI: 10.1093/aobpla/plx076
• Languages: English
• ISSNs: 2041-2851

Abstract

Abstract : Propagule dispersal shapes fine-scale spatial genetic structure (FSGS), which is mostly a function of physical distance between individuals. However, such a relation with distance may not occur when asymmetric processes, for instance, wind direction during dispersal, are involved. We combined genetic and seed dispersal data to assess the pattern of FSGS in the keystone species Cyperus papyrus as a function of distance and wind direction. Differences in FSGS between adults and juveniles were detected as a function of distance between individuals. Fine-scale spatial genetic structure was also found to be a function of wind direction during dispersal. Our findings further suggest post-dispersal processes could also influence FSGS. Abstract: Limited seed or pollen dispersal enhances spatial genetic relatedness between individuals (fine-scale spatial genetic structure, FSGS), which usually decreases as a function of physical distance. However, such isotropic pattern of FSGS may not always occur when spatially asymmetric processes, for instance, wind direction during dispersal, are considered in wind-pollinated and -dispersed plants. This study assessed the pattern of FSGS in the keystone tropical wetland plant Cyperus papyrus (papyrus) as a function of these isotropic and anisotropic processes. We tested the hypothesis that the FSGS would be influenced by predominant wind direction during pollen and seed dispersal, as well as by the physical distance between individuals. We genotyped a total of 510 adults and 407 juveniles from three papyrus swamps (Ethiopia) using 15 microsatellite markers. In addition, the contemporary directional dispersal by wind was evaluated by seed release-recapture experiments and complemented with parentage analysis. Adults and juveniles differed in the strength of isotropic FSGS ranging from 0.09 to 0.13 and 0.12 to 0.16, respectively, and this suggests variation in dispersal distance. Anisotropic FSGS was found to be a function of asymmetric wind direction during dispersal/pollination that varied between sites. Historical gene dispersal distance was astoundingly low (<4 m), possibly due to localized seed rain. According to our contemporary dispersal estimates, mean pollen dispersal distances were longer than those of seed dispersal (101 and <55 m, respectively). More than two-thirds of seeds and half of pollen grains were locally dispersed (≤80 m). The difference in historical and contemporary dispersal distance probably resulted from the asymmetric wind direction due to change in vegetation cover in the surrounding matrix. We further concluded that, in addition to wind direction, post-dispersal processes could influence gene dispersal distance inferred from the FSGS.