Abstract
BackgroundFragmentation of habitats by roads, railroads, fields, buildings and other human activities can affect population size, pollination success, sexual and asexual reproduction specially in plants showing pollinator limitation, such as Mediterranean orchids. In this study, we assessed pollen flow, selfing rates, vegetative reproduction and female reproductive success and their correlations with habitat characters in nine fragmented subpopulations of Serapias lingua.To improve understanding of population structure effects on plant biology, we examined genetic differentiation among populations, pollen flow, selfing rates and clonal reproduction using nuclear microsatellite markers.ResultsSmaller populations showed a significant heterozygote deficit occurred at all five nuclear microsatellite loci, the coefficient of genetic differentiation among populations was 0.053 and pairwise FST was significantly correlated with the geographical distance between populations. Paternity analysis of seeds showed that most pollen flow occurred within a population and there was a positive correlation between percentage of received pollen and distance between populations.The fruit production rate varied between 5.10 % and 20.30 % and increased with increasing population size, while the percentage of viable seeds (78-85 %) did not differ significantly among populations. The extent of clonality together with the clonal and sexual reproductive strategies varied greatly among the nine populations and correlated with the habitats where they occur. The small, isolated populations tended to have high clonal diversity and low fruit production, whereas the large populations with little disturbance were prone to have reductions in clonal growth and increased sexual reproduction.ConclusionsWe found that clonality offers an advantage in small and isolated populations of S. lingua, where clones may have a greater ability to persist than sexually reproducing individuals.
Highlights
Fragmentation of habitats by roads, railroads, fields, buildings and other human activities can affect population size, pollination success, sexual and asexual reproduction specially in plants showing pollinator limitation, such as Mediterranean orchids
Population size and density The stands differed in population size, ranging from 284 to ~3200 individuals, in population density (0.70–5.75 individuals/m2) (Table 1) and degree of isolation
Reproductive success Significant differences were detected among the populations in their fruit production rate
Summary
Fragmentation of habitats by roads, railroads, fields, buildings and other human activities can affect population size, pollination success, sexual and asexual reproduction specially in plants showing pollinator limitation, such as Mediterranean orchids. We assessed pollen flow, selfing rates, vegetative reproduction and female reproductive success and their correlations with habitat characters in nine fragmented subpopulations of Serapias lingua. Fragmentation of plant populations, the process by which formerly continuous populations turn into patches of different sizes, isolated from each other, may have distinctive effects on populations: (1) affecting reproductive success, (2) altering patterns of pollen-mediated gene flow (pollen flow) and (3) affecting self-pollination and vegetative propagation. Reductions in reproductive success due to Pellegrino et al BMC Plant Biology (2015) 15:222 reduced insect movements are strong for plants which show a high degree of dependence on their pollinator mutualism (i.e. pollinator limitation) for fruit production [6], such as Mediterranean deceptive orchids [7]. Selfpollinating populations are more likely to establish in habitats where pollinators appear to be scarce, in which population size is small [8], and in environments with limited opportunity for outcrossing [9]
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