Hostname: page-component-78c5997874-8bhkd Total loading time: 0 Render date: 2024-11-04T01:40:30.184Z Has data issue: false hasContentIssue false

Conservation biology of three threatened Limonium species endemic to Zakynthos Island (Ionian Islands, Greece)

Published online by Cambridge University Press:  30 October 2024

Anna-Thalassini Valli
Affiliation:
Laboratory of Systematic Botany, Department of Crop Science, Agricultural University of Athens, Athens, Greece
Charikleia Papaioannou
Affiliation:
Laboratory of Genetics, Department of Biology, University of Patras, Patras, Greece
Eleni Liveri
Affiliation:
Laboratory of Botany, Department of Biology, University of Patras, Patras, Greece
Vasileios Papasotiropoulos
Affiliation:
Laboratory of Plant Breeding and Biometry, Department of Crop Science, Agricultural University of Athens, Athens, Greece
Panayiotis Trigas*
Affiliation:
Laboratory of Systematic Botany, Department of Crop Science, Agricultural University of Athens, Athens, Greece
*
*Corresponding author, [email protected]
Rights & Permissions [Opens in a new window]

Abstract

Knowledge of the life history traits, reproductive biology and demography of rare species is fundamental for their conservation, yet plant population monitoring is uncommon. The restricted ranges of the Limonium species endemic to the Mediterranean area, combined with the vulnerability of their specialized littoral habitats, indicate the need for appropriate conservation measures. We evaluate the conservation status and estimate the future extinction risk of three Limonium species endemic to Zakynthos Island in the Ionian Islands, Greece (Limonium korakonisicum, Limonium phitosianum and Limonium zacynthium) using 5 years of monitoring data. We compile information on their geographical distribution, population dynamics, reproductive biology and genetic diversity. Population sizes and survival rates of seedlings exhibited marked annual fluctuations, although fecundity and relative reproductive success remained high throughout the monitoring period. We observed a dominance of mature individuals in all three species, indicating their increased tolerance to salinity. Three subpopulations each of L. phitosianum and L. zacynthium were genotyped using five microsatellite loci. The observed number of alleles and the low gene flow value potentially indicate reduced genetic diversity, inbreeding, and limited gene flow within and among subpopulations of both species. Based on the IUCN categories and criteria, we assess L. korakonisicum as Critically Endangered, L. phitosianum as Near Threatened and L. zacynthium as Endangered. Population viability analyses predict that, among the three species, L. zacynthium will face the highest risk of extinction within the next 50 years. Knowledge of the biology of these species provides data essential for identifying critical factors for their survival and for proposing targeted conservation measures.

Type
Article
Creative Commons
Creative Common License - CCCreative Common License - BY
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.
Copyright
Copyright © The Author(s), 2024. Published by Cambridge University Press on behalf of Fauna & Flora International

Introduction

Knowledge of the life history traits, reproductive biology and demographic characteristics of rare species is fundamental for their protection and restoration (Schemske et al., Reference Schemske, Husband, Ruckelshaus, Goodwillie, Parker and Bishop1994; Yates & Broadhurst, Reference Yates and Broadhurst2002). Monitoring, including assessing range size, population dynamics and exposure to anthropogenic threats, is one of the core activities of conservation biology and provides predictive power (Tienes et al., Reference Tienes, Skogen, Vitt and Havens2010). Long-term monitoring of marked individuals can provide information on vital rates (e.g. survival, transition between life stages) for estimating population growth rates and probability of extinction through matrix population modelling (Morris & Doak, Reference Morris and Doak2002; McCaffery et al., Reference McCaffery, Reisor, Irvine and Brunson2014).

Genetic information is important for managing threatened populations and species, and variability within populations is related to their evolutionary potential, which is often higher in more genetically variable populations (Hoffmann et al., Reference Hoffmann, Sgrò and Kristensen2017; Ørsted et al., Reference Ørsted, Hoffmann, Sverrisdóttir, Nielsen and Kristensen2019). Consequently, evaluating genetic variability is crucial when making management decisions for threatened species (Weeks et al., Reference Weeks, Sgro, Young, Frankham, Mitchell and Miller2011; Hoffmann et al., Reference Hoffmann, White, Jasper, Yagui, Sinclair and Kearney2020). Genetic studies enhance conservation effectiveness by identifying populations with low genetic diversity and predicting genetic drift effects (Nicoletti et al., Reference Nicoletti, Benedetti, Airò, Ruffoni, Mercuri and Minuto2012; Augustinos et al., Reference Augustinos, Sotirakis, Trigas, Kalpoutzakis and Papasotiropoulos2014).

Plant population monitoring is uncommon because it is time- and resource-demanding (Heywood & Iriondo, Reference Heywood and Iriondo2003). In Greece, for example, despite the high number of endemic and threatened plants (Phitos et al., Reference Phitos, Strid, Snogerup and Greuter1995, Reference Phitos, Constantinidis and Kamari2009; Dimopoulos et al., Reference Dimopoulos, Raus, Bergmeier, Constantinidis, Iatrou and Kokkini2013), studies of their conservation biology is scarce (but see Valli et al., Reference Valli, Chondrogiannis, Grammatikopoulos, Iatrou and Trigas2021a,Reference Valli, Koumandou, Iatrou, Andreou, Papasotiropoulos and Trigasb). Limonium Miller is one of the largest genera in the Mediterranean area, which is the centre of diversity of the genus (Brullo & Erben, Reference Brullo and Erben2016). The high diversity and complexity of Limonium is a result of the reproductive behaviour of the genus, which encompasses sexual and apomictic reproduction, frequent hybridization, and polyploidy (Georgakopoulou et al., Reference Georgakopoulou, Manousou, Artelari and Georgiou2006; Brullo & Erben, Reference Brullo and Erben2016; González-Orenga et al., Reference González-Orenga, Grigore, Boscaiu and Vicente2021). The Limonium species of the Mediterranean area often have punctiform distributions (Brullo & Erben, Reference Brullo and Erben2016; Buira et al., Reference Buira, Aedo and Medina2017).

Limonium species typically grow in littoral habitats, and they are adapted to the environmental stress of rocky and sandy seashores and salt marshes (Erben, Reference Erben, Castroviejo, Aedo, Cirujano, Laínz, Montserrat and Morales1993; Caperta et al., Reference Caperta, Espírito-Santo, Silva, Ferreira, Paes and Róis2014). However, a substantial number of these littoral species are threatened (van der Maarel & van der Maarel-Versluys, Reference van der Maarel and van der Maarel-Versluys1996), primarily as a result of anthropogenic impacts in coastal regions. Fourteen Limonium species endemic to Greece are already considered threatened (Phitos et al., Reference Phitos, Strid, Snogerup and Greuter1995, Reference Phitos, Constantinidis and Kamari2009). The Greek Ionian Islands host 14 Limonium species, nine of which are endemic to this archipelago (Dimopoulos et al., Reference Dimopoulos, Raus, Bergmeier, Constantinidis, Iatrou and Kokkini2013; Flora Ionica Working Group, 2016). Among these, three species (Limonium korakonisicum R. Artelari & Valli, Limonium phitosianum R. Artelari and Limonium zacynthium R. Artelari) are endemic to Zakynthos Island. The narrow ranges of the endemic Limonium species in the Ionian Islands combined with the high vulnerability of their specialized habitats indicate the need for appropriate conservation measures.

Here we combine demographic and genetic approaches to assess conservation status and population trends, and predict the extinction risk of the three Limonium species endemic to Zakynthos Island. We aimed to (1) define the distribution of the species by exploring all potentially suitable habitats, (2) assess their population dynamics and reproductive biology, (3) estimate genetic diversity and potential gene flow within and among subpopulations of L. phitosianum and L. zacynthium, and (4) propose conservation measures for the management and maintenance of the three species.

Methods

Studied species

Limonium korakonisicum, L. phitosianum and L. zacynthium are endemic to Zakynthos Island (Plate 1). Although endemism in Limonium is usually associated with apomixis (Erben, Reference Erben1978; Artelari, Reference Artelari1984a; Castro & Rosselló, Reference Castro and Rosselló2007; Brullo & Erben, Reference Brullo and Erben2016), most of the Ionian endemics, including L. phitosianum and L. zacynthium, are sexually reproducing diploids (2n = 18; Artelari, Reference Artelari1984a,Reference Artelarib; Artelari & Kamari, Reference Artelari and Kamari1986). Other Limonium species are mostly polyploids and typically apomictic, and L. korakonisicum is the only endemic apomictic polyploid species (6×) known in this area (Valli & Artelari, Reference Valli and Artelari2015). The latter species forms a small population in the Korakonisi area, where it coexists with L. phitosianum (Valli & Artelari, Reference Valli and Artelari2015). Limonium phitosianum and L. zakynthium are included in The European Threatened Plant List (Sharrock & Jones, Reference Sharrock and Jones2009). A record of L. phitosianum from the Stamfani islet in the Strofades Islands c. 46 km south-south-east of Zakynthos (Brullo & Erben, Reference Brullo and Erben2016) is based on a single incomplete specimen (Messenien, Insel Stamfani, 14 September 1980, Pieper s.n. (Herb. Greuter)), and its occurrence there is considered doubtful. All subsequently collected Limonium specimens from Strofades Islands belong to Limonium virgatum (Willd.) Fourr., and therefore L. phitosianum is considered endemic to Zakynthos.

Plate 1 The three species and their habitats: (a) Limonium korakonisicum, (b) Limonium phitosianum and (c) Limonium zacynthium.

Geographical distribution and spatial data

To document distribution, we conducted a 5-year survey (2014–2018) encompassing all suitable habitats (i.e. calcareous maritime cliffs, rocky and sandy coastal areas) across Zakynthos Island. We mapped each species once per year, during flowering, using a GPS, and calculated extent of occurrence (EOO) for each species and the local extent of occurrence (local EOO) of each subpopulation using ArcGIS 10.5.1 (Esri, USA), and estimated area of occupancy (AOO) as the sum of the occupied 2 × 2 km grid cells per species (IUCN, 2022a). Estimated EOO and AOO were cross-checked using GeoCAT (Bachman et al., Reference Bachman, Moat, Hill, de la Torre and Ben Scott2011). Local EOO was calculated following Andreou et al. (Reference Andreou, Delipetrou, Kadis, Tsiamis, Bourtzis and Georghiou2011) as the smallest polygon or polygons encompassing all plant colonies uninterrupted by unsuitable habitat at each subpopulation location. We chose this approach because a 2 × 2 km grid is too coarse for species with restricted geographical distributions, particularly littoral species, and provides a more precise measure of a species' spatial extent within its fragmented habitats, often yielding smaller values than the traditional EOO. In 2023, we revisited the locations of all three species to ascertain whether there had been any changes in EOO or AOO since 2018.

Population size

The terminology used (mature individual, population, subpopulation, population size and location) follows IUCN (2022a). To estimate population size, a count of all mature individuals was conducted during flowering and fruiting across all subpopulations of each species. For L. korakonisicum, we completely censused mature individuals in 5 consecutive years (2014–2018; Table 1). For L. phitosianum, we counted mature individuals in 20 random 5 × 5 m plots in subpopulations Lp1, Lp2, Lp8, Lp9 and Lp11, and in complete censuses in other subpopulations over the same 5-year period, except for Lp13 and Lp14 (only in 2018). For L. zacynthium, we counted mature individuals in four random 5 × 5 m plots in subpopulation Lz1, and in complete censuses in other subpopulations for the same 5 consecutive years, except for Lz2 and Lz3 (4 years of counts). The number of plants per m2 provided an approximate estimate of plant density (Andreou et al., Reference Andreou, Kadis, Delipetrou and Georghiou2015), calculated by dividing the number of mature individuals by the local EOO for each subpopulation. To assess the stage-structure distribution, plants were categorized as seedlings, non-reproductive (juveniles, immatures, non-flowering), and reproductive (flowering/fruiting). Limonium korakonisicum seedlings were distinguishable from those of the sympatric L. phitosianum by morphological features (Valli & Artelari, Reference Valli and Artelari2015). Discrimination between L. zacynthium and L. phitosianum seedlings was not feasible, resulting in their exclusion from life stage recordings in subpopulations where both species coexist (i.e. Lz5/Lp8, Lz1/Lp9, Lz4/Lp11). The population size of all three species was re-evaluated in 2023.

Table 1 Geographical data for the subpopulations of Limonium korakonisicum, Limonium phitosianum and Limonium zacynthium, with area of occupancy (AOO) and number of individuals sampled for genetic analyses.

Reproductive biology

The reproductive characteristics of the species (fertility: the mean number of seeds produced per individual; Burns et al., Reference Burns, Pardini, Schutzenhofer, Chung, Seidler and Knight2013; relative reproductive success: the per cent of ovules developing into seeds), were determined by tagging 10 randomly selected mature individuals per subpopulation at the onset of flowering and monitoring them until the end of fruiting. Limonium korakonisicum and L. zacynthium were monitored for 4 years (2015–2018) and L. phitosianum for 5 years (2014–2018), except for Lp13 and Lp14 (only in 2018).

We recorded the number of flowering/fruiting stems per individual and the number of flowers and fruits (caryopses) per stem weekly throughout flowering and fruiting. To determine the number of viable seeds per flower and per stem, we collected two stems during each fruiting period from tagged individuals and examined them under a stereoscope to identify sound seeds devoid of morphological alterations or infestations. We calculated relative reproductive success by dividing the actual sound seed production by the maximum potential seed yield, and estimated seed rain by multiplying the estimated seed number per individual by the number of mature individuals in each subpopulation and dividing this by the local EOO for each subpopulation (Andreou et al., Reference Andreou, Kadis, Delipetrou and Georghiou2015). For assessing seedling survival rate, we randomly tagged seedlings during August and checked viability during the following breeding season, for the single known subpopulation of L. korakonisicum and for subpopulations Lp1, Lp2, Lp10 of L. phitosianum during 2015–2018, and for subpopulations Lz2 and Lz3 of L. zacynthium during 3 years (2016–2018).

The duration of flowering and fruiting across all species and subpopulations was monitored at intervals of 1–2 weeks over the 5 consecutive years. Correlation of the duration of flowering/fruiting with mean annual temperature, maximum and minimum temperatures, and precipitation was examined with stepwise multiple linear regression analysis. Meteorological data were obtained from the Hellenic National Meteorological Service. Comparisons of reproductive data were assessed using One Way ANOVA, and differences among pairs of means were validated using Tukey's Method in Statistica 8.0 (StatSoft, Germany).

Population viability analysis and conservation status assessment

We conducted a population viability analysis in RAMAS Ecolab 2 (Rexstad et al., Reference Rexstad, Akçakaya, Burgman and Ginzburg2000), using the simple, unstructured population model. Initial abundance was based on population size in the first year, and seedling survival rate was used as the survival rate. Population growth rate (R), reflecting population size interannual variation (N(t + 1)/Nt), where N is number of individuals in year t, was characterized by mean and SD values, accounting for environmental stochasticity. We used the demographic stochasticity option facilitating the consideration of variations in annual recruitment, growth and mortality rates, even under stable environmental conditions. The model assumed density-independent, exponential population growth until reaching ceiling K, at which point the growth rate abruptly reduced to 1.0 (Akçakaya et al., Reference Akçakaya, Burgman and Ginsburg1999) because of uncertainties regarding density dependence in the three Limonium species. Projections were to 10 and 50 years from 2018, and simulations ran with 1,000 replications, with 95% confidence intervals based on the Kolmogorov–Smirnov dispersion test (Sokal & Rohlf, Reference Sokal and Rohlf1981). For L. phitosianum and L. zacynthium, analyses were conducted for both total populations and individual subpopulations. Conservation assessment followed IUCN (2022a).

Threats

Any direct threats to the habitats and/or individuals of the three species and any stresses they cause to the species were recorded in situ and classified according to IUCN (2022b).

Genetic analyses of the diploid Limonium species

We sampled a total of 56 individuals from three subpopulations of L. zacynthium and three subpopulations of L. phitosianum in September 2021 (Table 1). Fresh leaf material was immediately placed in silica gel to dry. To ensure sampling of separate individuals, material was only collected from plants at least 5 m apart. Total genomic DNA was extracted from 20 mg of dried leaf samples using the NucleoSpin Plant II kit (Macherey-Nagel, Germany) following the manufacturer's instructions. The quantity and quality of the extracted DNA were assessed by agarose gel electrophoresis and spectrophotometer. We stored DNA samples at −20 °C until used.

Of the eight microsatellite markers initially selected for genotyping (Supplementary Table 1), five (Ln39, Ln68, Ln115, Ln152, Ld423) that showed correct amplification pattern by polymerase chain reaction (PCR) testing were selected and genotyped. Multiplex PCR reactions were carried out in 96-well plates containing c. 10 ng of template DNA, 0.2 μM forward and reverse primers, 1.5 mM MgCl2, 0.2 mM dNTPs, 1 × KAPA Taq buffer and 1 U of KAPA Taq DNA Polymerase (Kapa Biosystems, USA). Cycling conditions consisted of an initial 94 °C denaturation step for 5 min, followed by 30 cycles of 40 s at 94 °C, 50 s at 54/64 °C (depending on the primer pairs used) and 50 s at 72 °C, with a final extension at 72 °C for 7 min. PCR products were separated on SeqStudio Genetic Analyzer (Applied Biosystems, USA). Allele sizes were determined using STRand 2.4.110 (Toonen & Hughes, Reference Toonen and Hughes2001).

We used GenAlEx 6.5 (Peakall & Smouse, Reference Peakall and Smouse2012) and GENEPOP 4.7.5 (Raymond & Rousset, Reference Raymond and Rousset1995; Rousset, Reference Rousset2008) to calculate the numbers of alleles (Na) and effective alleles (Ne), Shannon's information index (I), observed (Ho) and expected (He) heterozygosity, total mean fixation index (FST), inbreeding coefficient (Fis) and gene flow (Nm).

Results

Distribution

Limonium korakonisicum is currently known only from its type locality in Korakonisi, south-west Zakynthos (Fig. 1). Its EOO and AOO are 4 km2, and its local EOO is 463 m2 (Tables 1 & 2; values of local EOO for the three species are for 2018).

Fig. 1 Distribution of Limonium korakonisicum and Limonium zacynthium, their area of occupancy (i.e. the number of occupied 2 × 2 km grid cells), and the estimated extent of occurrence (EOO) of L. zacynthium. Numbers indicate subpopulations (Lz1, etc.; Table 1).

Table 2 Number of mature individuals (counted in complete censuses, except for subpopulations noted), local extent of occurrence (EOO, in m2) and plants per m2 in each subpopulation and population of the three Limomium species in 2014–2018 and 2023.

1 Counts of mature individuals were in 20 random 5 × 5 m plots.

2 Counts of mature individuals were in four random 5 × 5 m plots.

The population of L. phitosianum comprises 14 subpopulations (Table 1, Fig. 2). We discovered several new subpopulations (Lp2, Lp4, Lp9, Lp10, Lp12, Lp13, Lp14), expanding the known range of this species. Habitat loss has occurred, however, as a result of anthropogenic activities, including the construction of a port that led to the extinction of a subpopulation in Aghios Nikolaos (Volimes). The EOO of L. phitosianum is 460 km2, the AOO is 60 km2 and the local EOO is 83,443 m2 (Fig. 2).

Fig. 2 Distribution of Limonium phitosianum, its area of occupancy (i.e. the number of occupied 2 × 2 km grid cells), and the estimated extent of occurrence (EOO). Numbers indicate subpopulations (Lp1, etc.; Table 1).

We confirmed L. zacynthium at all of its known localities except its locus classicus on Keri Lake beach, which has suffered habitat destruction from a tourism-related development. We discovered one new subpopulation, Lz3 (Pelouzo islet). The species has three large subpopulations (Lz1, Lz2, Lz3) but subpopulations Lz4 and Lz5 comprise only 2–5 individuals. The EOO of L. zacynthium is 93 km2, the AOO is 28 km2 and the local EOO is 9,036 m2 (Fig. 1).

Re-evaluation of the range of the three species in 2023 revealed no substantial change, except for a decrease in the local EOO of subpopulation Lp11, probably as a result of new recreational facilities in Porto Roxa. The EOO and AOO of L. phitosianum were not affected, however.

Population size

The population size of L. korakonisicum remained relatively stable during the monitoring period. Limonium phitosianum showed varying trends, with some subpopulations decreasing and others increasing in size. The population of L. zacynthium significantly declined in 2018, primarily because of reductions in the Lz1 subpopulation (Table 2). By 2023, the population size of all three species had decreased (Table 2). Observations of developmental stages were consistent across all studied species, with a predominance of reproductive individuals in all subpopulations and with seedlings comprising only a small proportion of individuals (Supplementary Table 2).

Reproductive biology

For L. korakonisicum, the survival rate of seedlings ranged from 25% in 2016 to 50% in 2015 and 2017 (Table 3). Pearson's correlation coefficient revealed a significant positive correlation between annual seedling survival rate and the population growth rate (r = 0.593, P < 0.05). The mean annual relative reproductive success was consistently high (69.3–76.3%). Flowering was 52.6 days on average (early August–late September). Fruiting was mid August–mid/late October (average duration 63.4 days), sometimes extending to early November (Fig. 3).

Fig. 3 Flowering and fruiting periods of the three species of Limonium during 2014–2018.

Table 3 Reproductive characteristics of the three Limonium species during the monitoring period; n indicates the number of randomly selected mature individuals or number of stems of tagged individuals. Different superscript letters indicate significant differences (P < 0.05) between years for each reproductive parameter.

1 Measurements taken at specific points in time.

For L. phitosianum, seedling survival rate varied from 27.3% in 2018 to 57.5% in 2017, and relative reproductive success was consistently high (67–74.3%). The number of flowers and caryopses were significantly higher in 2017 and 2018 compared to earlier years. Flowering was 50.4 days (early August–late September) and fruiting 54.4 days (mid August–early October) on average (Fig. 3). Fruiting duration was inversely correlated (r = −0.7098, P < 0.05) with mean monthly precipitation during September–October.

For L. zacynthium, seedling survival rate was 35.7–66.7%. Relative reproductive success was consistently high (69.3–76.3%). Mean number of caryopses per flower and relative reproductive success were significantly higher in 2017 and 2018 compared to earlier years. The duration of flowering (56–67 days, late July–late September) and fruiting (average 56 days, late August–mid-October) was relatively stable throughout the monitoring period (Fig. 3).

Population viability analysis

For L. korakonisicum, population extinction risk is zero over the next 10 years, and increases to 4.2% within the next 50 years (Fig. 4). The population of L. phitosianum faces no extinction risk in either period (Fig. 4). However, subpopulations Lp2, Lp5 and Lp7 have increased risks of extinction over the next 50 years, of 13.3–58% (Supplementary Fig. 1). In the next 10 years, subpopulations Lz1 and Lz3 of L. zacynthium have a gradual reduction in size but no risk of extinction. However, within the next 50 years, the species faces a high risk of extinction (67.8%), with a substantial likelihood (89.1%) that subpopulation Lz1 will go extinct.

Fig. 4 Population viability analysis for the three species of Limonium over the next 10 years and the next 50 years from 2018. The graphs display the average number of extant populations (solid line), along with  ± 1 standard deviation. Dots indicate the minimum and maximum numbers of extant populations. This analysis illustrates potential population trends and variability of each species over the specified time periods.

Threats

The threats identified for L. korakonisicum are: tourism development (threat code 1.3), including construction of canteens and secondary roads (4.1), resulting in the reduction of the species' habitat, and competition with other species (8.2), especially with sympatric seedlings of L. phitosianum.

The primary threat to L. phitosianum is uncontrolled tourism development (1.3), particularly through resort construction and alteration of rocky shores affecting subpopulations Lp1, Lp3, Lp4 and Lp8–11, leading to habitat degradation and loss. Additionally, trampling in highly tourist-visited areas such as Lp7, Lp8 and Lp10 poses a significant threat (6.1). An immediate threat in Porto Limnionas-Roxa (Lp11) arises from the invasive plant Carpobrotus edulis (8.1.2). These threats were identified across all 14 locations.

The threats to L. zacynthium include: tourism development (1.3), such as the construction of a canteen at Marathias (Lz1) and alteration of rocky shores in subpopulations Lz1, Lz4 and Lz5; competition with other species (8.2) observed at Lz1, where L. zacynthium competes with L. phitosianum; and trampling (6.1) occurring at Marathonisi islet (Lz2). The extinction of L. zacynthium from its locus classicus at Keri Lake beach as a result of tourism development underscores the severity of this threat to endemic littoral plant species. These threats were identified across four of the five locations.

Conservation status assessment

We assess L. korakonisicum as Critically Endangered based on criteria B1ab(v) + 2ab(v), with EOO < 100 km2 (B1) and AOO < 10 km2 (B2), and only one location (a) and a projected continuing decline (b) in number of mature individuals (v), and C2a(ii), with < 250 mature individuals (C) and a projected continuing decline in number of mature individuals (2), and all individuals in a single subpopulation (a(ii)). We assess L. phitosianum as Near Threatened, as it is close to meeting the criteria for Vulnerable based on its EOO and AOO, with the exception of the number of locations, which is > 10. We assess L. zacynthium as Endangered based on criteria B1ab(iv,v) + B2ab(iv,v), with EOO < 100 km2 (B1) and AOO < 10 km2 (B2), and ≤ 5 locations (a), and a projected continuing decline in number of mature individuals (b(v)) and number of locations or subpopulations (b(iv)).

Genetic analyses

Analysis of the five microsatellite loci revealed 28 alleles (1–22 alleles/locus) in total. Ln115 and Ln152 loci were monomorphic in both species, and Ln39 is monomorphic in L. phitosianum but polymorphic in L. zacynthium, with a private allele in subpopulation Lz2. Ln68 was monomorphic in L. zacynthium and polymorphic in L. phitosianum, with a private allele in subpopulation Lp7. Ld423 was highly polymorphic, with 22 different alleles across all subpopulations. Of these, seven were present in both species, and the others were species-specific. Limonium phitosianum had 11 private alleles, some of which were subpopulation-specific (three in subpopulation Lp7, six in subpopulation Lp10), and two occurred in more than one subpopulation (Lp1 and Lp7; Lp7 and Lp10). Limonium zacynthium had four private alleles, one in subpopulation Lz1 and three in Lz2.

Mean number of alleles (Na) ranged from 1.000 to 3.200 (for subpopulationa Lp1 and Lp10, respectively), and the mean effective number of alleles (Ne) ranged from 1.000 to 2.706 (for the same subpopulations). Shannon's information index (I) ranged from 0.000 to 0.474 (for Lp1 and Lp10, respectively). Observed heterozygosity (Ho) was lowest in Lz3 and Lp1 (0.000) and highest for Lp7 (0.220), and expected heterozygosity (He) had the lowest and highest values in Lp1 and Lp7, respectively (Supplementary Table 3). The inbreeding coefficient (Fis) values were positive for all subpopulations, except for Lp1 where no value was obtained by GENEPOP. Fis was 1.000 for Lz3, and for the other subpopulations the following values were estimated: 0.0913 (Lz2), 0.1091 (Lp7), 0.1884 (Lp10), 0.3000 (Lz1). The mean fixation index (FST) value was 0.172 when calculated only among L. phitosianum subpopulations and 0.151 among L. zacynthium subpopulations. The overall FST calculated using the data available for both species was 0.159, and the value of gene flow (Nm) was 0.424.

Discussion

Population size and reproductive biology

In this study, we monitored all extant subpopulations of three rare Limonium species endemic to Zakynthos Island for 5 years. The EOO and AOO remained stable throughout the study for all three species.

There was a prevalence of mature individuals of L. korakonisicum, with low seedling abundance. The rocky calcareous substrate and potential competition with seedlings of the sympatric L. phitosianum could impede successful establishment and growth of L. korakonisicum seedlings, although relative reproductive success was consistently high, indicating this is not a limiting factor for the species' survival. Given a seed germination rate of up to 86% (Valli & Artelari, Reference Valli and Artelari2015), we suggest that seedling establishment and survival could be a bottleneck in the species' reproductive cycle. The population viability analysis indicated a 3.9% extinction risk over the next 50 years. However, deterministic models may underestimate quasi-extinction probability by not considering other factors influencing population viability (Akçakaya et al., Reference Akçakaya, Burgman and Ginsburg1999; Morris & Doak, Reference Morris and Doak2002).

There were fluctuations in the seedling survival rate of L. phitosianum. The lowest spring rainfall during monitoring, in 2018 (14.7 mm), corresponded with the species' lowest seedling survival rate, suggesting dependence on salinity influenced by climate conditions. The negative correlation of fruiting duration with mean monthly precipitation in September–October emphasizes the importance of water availability in fruit ripening. Seed dispersal in L. phitosianum is triggered by water absorption, a mechanism also observed in Limonium creticum (Fournaraki, Reference Fournaraki2010). The high annual seed production but relatively low per cent of seedlings indicates that seedling establishment is the critical stage for this species.

The population size of L. zacynthium is notably small, and it halved in 2018, primarily a result of a decrease in subpopulation Lz1, where the highest number of dead individuals occurred in that year. This decline, combined with increased relative reproductive success and seed production 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., Reference Espinar, García and Clemente2005; Redondo-Gómez et al., Reference Redondo-Gómez, Naranjo, Garzón, Castillo, Luque and Figueroa2008). The high negative correlation of seedling survival with mean monthly precipitation in the preceding October–December suggests that intense precipitation 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 species 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., Reference Laguna, Navvaro, Pérez-Rovira, Ferrando and Ferrer-Gallego2016; González-Orenga et al., Reference González-Orenga, Grigore, Boscaiu and Vicente2021). The markedly lower population size of L. korakonisicum in 2023 underscores the urgent need for implementing 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. zacynthium. Genetic diversity is critical for maintenance of long-term fitness, adaptation and potential for survival (Frankham et al., Reference Frankham, Ballou and Briscoe2002; Bouzat, Reference Bouzat2010). Small population sizes and restricted distribution area can elevate inbreeding levels (e.g. Barrett & Kohn, Reference Barrett, Kohn, Falk and Holsinger1991; Falconer & Mackay, Reference Falconer and Mackay1996), and discrepancies between observed and expected heterozygosity can suggest potential inbreeding (Schimidt et al., Reference Schimidt, Jasper, Weeks and Hoffmann2021). In our study, expected heterozygosity was generally higher than the observed, indicating inbreeding across all subpopulations analysed except Lp1. In addition, the positive 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 subpopulations. The value of the mean fixation index (FST) across all analysed subpopulations for both species indicates a certain degree of genetic differentiation among them (FST measures the proportion of genetic variance that is a result of differences between populations compared 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, Reference Balloux and Lugon-Moulin2002), contributing to genetic divergence among subpopulations. This is also the case for FST values calculated 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 directly related to the identified threats. The main threat is coastal development for tourism, leading to habitat degradation. 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) by manual uprooting would reduce the threat from this invasive species. The establishment of a plant micro-reserves network (Laguna et al., Reference Laguna, Fos, Ferrando-Pardo, Ferrer-Gallego and Grigore2020) within the Management Unit's jurisdiction would benefit multiple species simultaneously and ensure 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 littoral rocks, resulting in decreased seedling survival rates (Frankham et al., Reference Frankham, Ballou, Ralls, Elbridge, Dudash and Fenster2017). We recommend genetic mixing for L. zacynthium through the creation of safety neopopulations, as suggested by Laguna & Ferrer-Gallego (Reference Laguna and Ferrer-Gallego2012), using seeds sourced from all known natural subpopulations. Similarly, for L. korakonisicum this strategy should be employed alongside the reinforcement of the existing subpopulation, a combined approach successfully applied for other Limonium species (e.g. Caperta et al., Reference Caperta, Espírito-Santo, Silva, Ferreira, Paes and Róis2014; Laguna et al., Reference Laguna, Navvaro, Pérez-Rovira, Ferrando and Ferrer-Gallego2016). These in situ conservation efforts should be complemented by ex situ measures such as seed bank storage and propagation trials, to facilitate future reintroduction and/or population reinforcement (Krigas et al., Reference Krigas, Karapatzak, Panagiotidou, Sarropoulou, Samartza and Karydas2022).

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 existence 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.

Acknowledgements

We thank Dimitris and Alexandros Petropoulos for their assistance with fieldwork; Martin Fisher and two anonymous reviewers for their helpful and constructive comments; and the staff of the Management Unit of Zakynthos and Ainos National Parks and the Protected Areas of the Ionian Islands for their assistance with the surveys. This research was funded by the General Secretariat for Research and Technology (GSRT) and the Hellenic Foundation for Research and Innovation (HFRI), grant number 1585 to A-TV.

Author contributions

Conception and study design: A-TV, PT; data collection: A-TV; monitoring and data analysis: A-TV, PT; genetic analysis: CP, EL, VP; writing: A-TV, VP, PT; revision: all authors.

Conflicts of interest

None.

Ethical standards

All monitoring and experimental procedures were approved by the Hellenic Ministry of the Environment and Energy, Directorate of Forest Protection (approval no. MEE/DFP/125613/6014) and this research abided by the Oryx guidelines on ethical standards.

Data availability

All relevant data are available in the article and supplementary material.

Footnotes

The supplementary material for this article is available at doi.org/10.1017/S0030605324000140

References

Akçakaya, H.R., Burgman, M.A. & Ginsburg, L.R. (1999) Applied Population Ecology: Principles and Computer Exercises Using RAMAS Ecolab 2.0. 2nd edition. Sinauer Associates, Sunderland, Massachusetts, USA.Google Scholar
Andreou, M., Delipetrou, P., Kadis, C., Tsiamis, G., Bourtzis, K. & Georghiou, K. (2011) An integrated approach for the conservation of threatened plants: the case of Arabis kennedyae (Brassicaceae). Acta Oecologica, 37, 239248.CrossRefGoogle Scholar
Andreou, M., Kadis, C., Delipetrou, P. & Georghiou, K. (2015) Conservation biology of Chionodoxa lochiae and Scilla morrisii (Asparagaceae): Two priority bulbous plant species of the European Union in Cyprus. Global Ecology and Conservation, 3, 511525.CrossRefGoogle Scholar
Artelari, R. (1984a) Biosistimatiki meléti tou génous Limonium (Plumbaginaceae) stin periochi tou Ioniou pelágous. PhD thesis. University of Patras, Patras, Greece.Google Scholar
Artelari, R. (1984b) Two new species of Limonium (Plumbaginaceae) from Zakynthos Island (Greece). Mitteilungen der Botanischen Staatssammlung München, 20, 429440.Google Scholar
Artelari, R. & Kamari, G. (1986) A karyological study of ten Limonium species (Plumbaginaceae) endemic in the Ionian area, Greece. Willdenowia, 15, 497513.Google Scholar
Augustinos, A., Sotirakis, K., Trigas, P., Kalpoutzakis, E. & Papasotiropoulos, V. (2014) Genetic variation in three closely related Minuartia (Caryophyllaceae) species endemic to Greece: implications for conservation management. Folia Geobotanica, 49, 603621.CrossRefGoogle Scholar
Bachman, S., Moat, J., Hill, A.W., de la Torre, J. & Ben Scott, J. (2011) Supporting Red List threat assessments with GeoCAT: geospatial conservation assessment tool. Zookeys, 150, 111126.CrossRefGoogle Scholar
Balloux, F. & Lugon-Moulin, N. (2002) The estimation of population differentiation with microsatellite markers. Molecular Ecology, 11, 155165.CrossRefGoogle ScholarPubMed
Barrett, S.C.H. & Kohn, J.R. (1991) Genetic and evolutionary consequences of small population sizes in plants: implications for conservation. In Genetics and Conservation of Rare Plants (eds Falk, D.A. & Holsinger, K.A.), pp. 330. Oxford University Press, New York, USA.CrossRefGoogle Scholar
Bouzat, J.L. (2010) Conservation genetics of population bottlenecks: the role of chance, selection, and history. Conservation Genetics, 11, 463478.CrossRefGoogle Scholar
Brullo, S. & Erben, M. (2016) The genus Limonium (Plumbaginaceae) in Greece. Phytotaxa, 240, 001212.CrossRefGoogle Scholar
Buira, A., Aedo, C. & Medina, L. (2017) Spatial patterns of the Iberian and Balearic endemic vascular flora. Biodiversity and Conservation, 26, 479508.CrossRefGoogle Scholar
Burns, J.H., Pardini, E.A., Schutzenhofer, M.R., Chung, Y.A., Seidler, K.J. & Knight, T.M. (2013) Greater sexual reproduction contributes to differences in demography of invasive plants and their noninvasive relatives. Ecology, 94, 9951004.CrossRefGoogle ScholarPubMed
Caperta, A.D., Espírito-Santo, M.D., Silva, V., Ferreira, A., Paes, A.P., Róis, A.S. et al. (2014) Habitat specificity of a threatened and endemic, cliff-dwelling halophyte. AoB Plants, 18, plu032.Google Scholar
Castro, M. & Rosselló, J.A. (2007) Karyology of Limonium (Plumbaginaceae) species from the Balearic Islands and the western Iberian peninsula. Botanical Journal of the Linnean Society, 155, 257272.CrossRefGoogle Scholar
Dimopoulos, P., Raus, T., Bergmeier, E., Constantinidis, T., Iatrou, G., Kokkini, S. et al. (2013) Vascular Plants of Greece: An Annotated Checklist. Botanischer Garten und Botanisches Museum Berlin, Berlin, Germany, and Hellenic Botanical Society, Athens, Greece.CrossRefGoogle Scholar
Erben, M. (1978) Die Gattung Limonium im südwest mediterranen Raum. Mitteilungen der Botanischen Staatssammlung München, 14, 361631.Google Scholar
Erben, M. (1993) Limonium Miller. In Flora Iberica, Vol. 3. Plumbaginaceae (partim)—Capparaceae (eds Castroviejo, S., Aedo, C., Cirujano, S., Laínz, M., Montserrat, P., Morales, R. et al.), pp. 2143. Real Jardı́nBotánico, CSIC, Madrid, Spain.Google Scholar
Espinar, J.L., García, L.V. & Clemente, L. (2005) Seed storage conditions change the germination pattern of clonal growth plants in Mediterranean salt-marshes. American Journal of Botany, 92, 10941101.CrossRefGoogle ScholarPubMed
Falconer, D.S. & Mackay, T.F.C. (1996) Introduction to Quantitative Genetics. 4th edition. Longman Scientific and Technical, Harlow, UK.Google Scholar
Flora Ionica Working Group (2016) Flora Ionica: An inventory of ferns and flowering plants of the Ionian Islands (Greece). floraionica.univie.ac.at [accessed 20 June 2023].Google Scholar
Fournaraki, C. (2010) Conservation of threatened plants of Crete: seed ecology, operation and management of a gene bank. PhD thesis. National and Kapodistrian University of Athens, Athens, Greece.Google Scholar
Frankham, R., Ballou, J.D. & Briscoe, D.A. (2002) Introduction to Conservation Genetics. Cambridge University Press, Cambridge, UK.CrossRefGoogle Scholar
Frankham, R., Ballou, S.D., Ralls, K., Elbridge, M.D.B., Dudash, M.R., Fenster, C.B. et al. (2017) Genetic Management of Fragmented Animal and Plant Populations. Oxford Academic, Oxford, UK.CrossRefGoogle Scholar
Georgakopoulou, A., Manousou, S., Artelari, R. & Georgiou, O. (2006) Breeding systems and cytology in Greek populations of five Limonium species (Plumbaginaceae). Willdenowia, 36, 741750.CrossRefGoogle Scholar
González-Orenga, S., Grigore, M.-N., Boscaiu, M. & Vicente, O. (2021) Constitutive and induced salt tolerance mechanisms and potential uses of Limonium Mill. species. Agronomy, 11, 413.CrossRefGoogle Scholar
Heywood, V.H. & Iriondo, J.M. (2003) Plant conservation: old problems, new perspectives. Biological Conservation, 113, 321335.CrossRefGoogle Scholar
Hoffmann, A.A., Sgrò, C.M. & Kristensen, T.N. (2017) Revisiting adaptive potential, population size, and conservation. Trends in Ecology and Evolution, 32, 506517.CrossRefGoogle ScholarPubMed
Hoffmann, A.A., White, V., Jasper, M., Yagui, H., Sinclair, S. & Kearney, M. (2020) An endangered flightless grasshopper with strong genetic structure maintains population genetic variation despite extensive habitat loss. Ecology and Evolution, 11, 53645380.CrossRefGoogle Scholar
IUCN (2022a) Guidelines for Using the IUCN Red List Categories and Criteria. Version 15.1. IUCN Species Survival Commission, Gland, Switzerland. iucnredlist.org/documents/RedListGuidelines.pdf [accessed 10 April 2023].Google Scholar
IUCN (2022b) Threats Classification Scheme. Version 3.3. IUCN, Gland, Switzerland. iucnredlist.org/resources/threat-classification-scheme [accessed 5 February 2023].Google Scholar
Krigas, N., Karapatzak, E., Panagiotidou, M., Sarropoulou, V., Samartza, I., Karydas, A. et al. (2022) Prioritizing plants around the cross-border area of Greece and the Republic of North Macedonia: integrated conservation actions and sustainable exploitation potential. Diversity, 4, 570.CrossRefGoogle Scholar
Laguna, E. & Ferrer-Gallego, P.P. (2012) Proximity reinforcements and safety neopopulations, new complementary concepts for certain types of in situ plant introductions. Conservacion Vegetal, 16, 14.Google Scholar
Laguna, E., Navvaro, A., Pérez-Rovira, P., Ferrando, I. & Ferrer-Gallego, P.P. (2016) Translocation of Limonium perplexum (Plumbaginaceae), a threatened coastal endemic. Plant Ecology, 2017, 11831194.CrossRefGoogle Scholar
Laguna, E., Fos, S., Ferrando-Pardo, I. & Ferrer-Gallego, P.P. (2020) Endangered halophytes and their conservations: lessons from eastern Spain. In From Molecules to Ecosystems Towards Biosaline Agriculture (ed. Grigore, M.N.), pp. 164. Springer, Cham, Switzerland, and Heidelberg, Germany.Google Scholar
McCaffery, R.M., Reisor, R., Irvine, K. & Brunson, J. (2014) Demographic monitoring and population viability analysis of two rare beardtongues from the Uinta basin. Western North American Naturalist, 74, 257274.CrossRefGoogle Scholar
Morris, W.F. & Doak, D.F. (2002) Quantitative Conservation Biology. Sinauer Associates, Sunderland, Massachusetts, USA.Google Scholar
Nicoletti, F., Benedetti, L.D., Airò, M., Ruffoni, B., Mercuri, A., Minuto, L. et al. (2012) Spatial genetic structure of Campanula sabatia, a threatened narrow endemic species of the Mediterranean basin. Folia Geobotanica, 47, 249262.CrossRefGoogle Scholar
Ørsted, M., Hoffmann, A.A., Sverrisdóttir, E., Nielsen, K.L. & Kristensen, T.N. (2019) Genomic variation predicts adaptive evolutionary responses better than population bottleneck history. PLOS Genetics, 15, e1008205.CrossRefGoogle ScholarPubMed
Peakall, R. & Smouse, P. (2012) GenAlEx 6.5: genetic analysis in Excel. Population genetic software for teaching and research—an update. Bioinformatics, 28, 25372539.CrossRefGoogle ScholarPubMed
Phitos, D., Strid, A., Snogerup, S. & Greuter, W. (1995) The Red Data Book of Rare and Threatened Plants of Greece. WWF Greece, Athens, Greece.Google Scholar
Phitos, D., Constantinidis, T. & Kamari, G. (2009) The Red Data Book of Rare and Threatened Plants of Greece, Vol. II (E-Z). Hellenic Βotanical Society, Patras, Greece.Google Scholar
Raymond, M. & Rousset, F. (1995) GENEPOP (version 1.2): population genetics software for exact tests and ecumenicism. Journal of Heredity, 86, 248249.CrossRefGoogle Scholar
Redondo-Gómez, S., Naranjo, E.M., Garzón, O., Castillo, J.M., Luque, T. & Figueroa, M.E. (2008) Effects of salinity on germination and seedling establishment of endangered Limonium emarginatum (Willd.) O. Kuntze. Journal of Coastal Research, 24, 201205.CrossRefGoogle Scholar
Rexstad, E., Akçakaya, H.R., Burgman, M.A. & Ginzburg, L.R. (2000) Applied population ecology: principles and computer exercises using RAMAS EcoLab. Journal of Mammalogy, 81, 11791181.Google Scholar
Rousset, F. (2008) GENEPOP ‘007: A complete re-implementation of the genepop software for Windows and Linux. Molecular Ecology Resources, 8, 103106.CrossRefGoogle ScholarPubMed
Schemske, D.W., Husband, B.C., Ruckelshaus, M.H., Goodwillie, C., Parker, I.M. & Bishop, J.G. (1994) Evaluating approaches to the conservation of rare and endangered plants. Ecology, 75, 584606.CrossRefGoogle Scholar
Schimidt, T.L., Jasper, M.-E., Weeks, A.R. & Hoffmann, A.A. (2021) Unbiased population heterozygosity estimates from genome-wide sequence data. Methods in Ecology and Evolution, 12, 18881898.CrossRefGoogle Scholar
Sharrock, S. & Jones, M. (2009) Conserving Europe's Threatened Plants: Progress Towards Target 8 of the Global Strategy for Plant Conservation. Botanic Gardens Conservation International, Richmond, UK.Google Scholar
Sokal, R.R. & Rohlf, J.F. (1981) Biometry: The Principles and Practice of Statistics in Biological Research. W.H. Freeman and Company, San Francisco, California, USA.Google Scholar
Tienes, M., Skogen, K., Vitt, P. & Havens, K. (2010) Optimal Monitoring of Rare Plant Populations. USDA, Forest Service, Washington, DC, USA.Google Scholar
Toonen, R.J. & Hughes, S. (2001) Increased throughput for fragment analysis on an ABI Prism 377 automated sequencer using a membrane comb and STRand software. Biotechniques, 31, 13201325.Google Scholar
Valli, A.-T. & Artelari, R. (2015) Limonium korakonisicum (Plumbaginaceae), a new species from Zakynthos Island (Ionian Islands, Greece). Phytotaxa, 217, 6372.CrossRefGoogle Scholar
Valli, A.-T., Chondrogiannis, C., Grammatikopoulos, G., Iatrou, G. & Trigas, P. (2021a) Conservation of Micromeria browiczii (Lamiaceae), Endemic to Zakynthos Island (Ionian Islands, Greece). Plants, 10, 778.CrossRefGoogle ScholarPubMed
Valli, A.-T., Koumandou, V.L., Iatrou, G., Andreou, M., Papasotiropoulos, V. & Trigas, P. (2021b) Conservation biology of threatened Mediterranean chasmophytes: The case of Asperula naufraga endemic to Zakynthos island (Ionian Islands, Greece). PLOS One, 16, e0246706.CrossRefGoogle ScholarPubMed
van der Maarel, E. & van der Maarel-Versluys, M. (1996) Distribution and conservation status of littoral vascular plant species along the European coasts. Journal of Coastal Conservation, 2, 7392.CrossRefGoogle Scholar
Weeks, A.R., Sgro, C.M., Young, A.G., Frankham, R., Mitchell, N.J., Miller, K. et al. (2011) Assessing the benefits and risks of translocations in changing environments: a genetic perspective. Evolutionary Applications, 4, 709725.CrossRefGoogle ScholarPubMed
Yates, C.J. & Broadhurst, L.M. (2002) Assessing limitations on population growth in two critically endangered Acacia taxa. Biological Conservation, 108, 1326.CrossRefGoogle Scholar
Figure 0

Plate 1 The three species and their habitats: (a) Limonium korakonisicum, (b) Limonium phitosianum and (c) Limonium zacynthium.

Figure 1

Table 1 Geographical data for the subpopulations of Limonium korakonisicum, Limonium phitosianum and Limonium zacynthium, with area of occupancy (AOO) and number of individuals sampled for genetic analyses.

Figure 2

Fig. 1 Distribution of Limonium korakonisicum and Limonium zacynthium, their area of occupancy (i.e. the number of occupied 2 × 2 km grid cells), and the estimated extent of occurrence (EOO) of L. zacynthium. Numbers indicate subpopulations (Lz1, etc.; Table 1).

Figure 3

Table 2 Number of mature individuals (counted in complete censuses, except for subpopulations noted), local extent of occurrence (EOO, in m2) and plants per m2 in each subpopulation and population of the three Limomium species in 2014–2018 and 2023.

Figure 4

Fig. 2 Distribution of Limonium phitosianum, its area of occupancy (i.e. the number of occupied 2 × 2 km grid cells), and the estimated extent of occurrence (EOO). Numbers indicate subpopulations (Lp1, etc.; Table 1).

Figure 5

Fig. 3 Flowering and fruiting periods of the three species of Limonium during 2014–2018.

Figure 6

Table 3 Reproductive characteristics of the three Limonium species during the monitoring period; n indicates the number of randomly selected mature individuals or number of stems of tagged individuals. Different superscript letters indicate significant differences (P < 0.05) between years for each reproductive parameter.

Figure 7

Fig. 4 Population viability analysis for the three species of Limonium over the next 10 years and the next 50 years from 2018. The graphs display the average number of extant populations (solid line), along with  ± 1 standard deviation. Dots indicate the minimum and maximum numbers of extant populations. This analysis illustrates potential population trends and variability of each species over the specified time periods.

Supplementary material: File

Valli et al. supplementary material

Valli et al. supplementary material
Download Valli et al. supplementary material(File)
File 213.8 KB