Limonium species endemic to Zakynthos Island 597
in the previous year, could be linked to increased vegetation density, indicating the species is a weak competitor. Different developmental stages in halophytes have distinct optimal salinity thresholds (Espinar et al., 2005; Redondo-Gómez et al., 2008). The high negative correlation of seedling survival with mean monthly precipitation in the preceding October–December suggests that intense precipi- tation during these wet months decreases seedling survival the following year. Additional studies on seed germination and seedling growth under varying salinity conditions are necessary to investigate this. The differences in the population sizes of the studied spe-
cies in 2023 compared to 2018 may be attributed to variations in developmental stages within populations. Similar annual variations in population size have been reported in other Limonium species (e.g. Laguna et al., 2016; González-Orenga et al., 2021). The markedly lower population size of L. kora- konisicumin 2023 underscores the urgent need for implemen- ting conservation management measures for this species.
Genetic variability
The analysis of microsatellites indicated reduced genetic diversity and inbreeding and restricted gene flow within and among subpopulations of L. phitosianum and L. za- cynthium. Genetic diversity is critical for maintenance of long-term fitness, adaptation and potential for survival (Frankham et al., 2002;Bouzat, 2010). Small population sizes and restricted distribution area can elevate inbreeding levels (e.g. Barrett&Kohn, 1991; Falconer&Mackay, 1996), and discrepancies between observed and expected hetero- zygosity can suggest potential inbreeding (Schimidt et al., 2021). In our study, expected heterozygosity was generally higher than the observed, indicating inbreeding across all subpopulations analysed except Lp1. In addition, the posi- tive inbreeding coefficient (Fis) across all subpopulations indicates an excess of homozygous individuals (i.e. more inbreeding than randomly expected); its high value implies a high degree of inbreeding for at least subpopulations Lz1 and Lz3, and gene flow appears to be reduced among sub- populations. The value of the mean fixation index (FST) across all analysed subpopulations for both species indi- cates a certain degree of genetic differentiation among them (FST measures the proportion of genetic variance that is a result of differences between populations com- pared to within populations). Higher FST values typically reflect greater genetic differentiation and reduced gene flow among populations (Frankham et al., 2002). In this study, the observed mean FST value implies limited gene flow and restricted intercrossing (Balloux & Lugon- Moulin, 2002), contributing to genetic divergence among subpopulations. This is also the case for FST values cal- culated within each species separately, reinforcing the
conclusion that there is significant genetic divergence and lack of genetic exchange among the subpopulations both within and among the species studied.
Conservation implications
The status of the three species of Limonium studied is di- rectly related to the identified threats. The main threat is coastal development for tourism, leading to habitat degrada- tion. Although these species occur both within and outside protected areas of the Natura 2000 Network (GR2210001, GR2210002), management within protected areas, overseen by the Management Unit of Zakynthos and Ainos National Parks and the Protected Areas of the Ionian Islands, is the most feasible option as the majority of land on Zakynthos is privately owned. We recommend installation of signage in heavily touristic areas, education of landowners about the importance of conservation, and installation of fencing at selected sites (such as Korakonisi and Marathonisi islet) as initial management measures for the conservation of the three species. These measures would curtail the effects of trampling and foster improved conditions for seedling growth. Additionally, eradication of Carpobrotus edulis in Porto Limnionas-Roxa (subpopulation Lp11) bymanual up- rooting would reduce the threat from this invasive species. The establishment of a plant micro-reserves network (Laguna et al., 2020) within the Management Unit’s jurisdic- tion would benefit multiple species simultaneously and en- sure management, protection and collective benefits for all three studied species. Our findings align with the higher levels of inbreeding depression observed in stressful environments, such as lit- toral rocks, resulting in decreased seedling survival rates (Frankham et al., 2017). We recommend genetic mixing for L. zacynthium through the creation of safety neopopula- tions, as suggested by Laguna&Ferrer-Gallego (2012), using seeds sourced from all known natural subpopulations. Similarly, for L. korakonisicum this strategy should be em- ployed alongside the reinforcement of the existing subpopu- lation, a combined approach successfully applied for other Limonium species (e.g. Caperta et al., 2014; Laguna et al., 2016). These in situ conservation efforts should be comple- mented by ex situ measures such as seed bank storage and propagation trials, to facilitate future reintroduction and/or population reinforcement (Krigas et al., 2022). In 2024, the staff of the Management Unit for Zakynthos
and Ainos National Parks and the Protected Areas of the Ionian Islands deployed informational signs across the Natura 2000 Network. These signs alert the public to the ex- istence of rare and threatened plant species and emphasize that uprooting them is strictly prohibited. This initiative marks the beginning of the management and conservation of these species.
Oryx, 2024, 58(5), 587–599 © The Author(s), 2024. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605324000140
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