Allozyme Variation Research Articles

Variation in the Local Grey Mullet Populations (Mugil cephalus) on the Western Pacific Fringe

Background: Understanding population genetic structures is crucial for planning and implementing conservation programmes to preserve species’ adaptive and evolutionary potential and thus ensure their long-term persistence. The grey mullet (Mugil cephalus) is a globally distributed coastal fish. Its populations in waters surrounding Taiwan on the western Pacific fringe are divided into at least two stocks (migratory and residential), but questions remain regarding their genetic divergence and gene flow. Methods and Results: To cast more light on this, allozyme variations at 21 presumptive gene loci of 1217 adult grey mullets from 15 localities in Japan, Taiwan and mainland China, and four gene loci from 1470 juveniles from three localities in Taiwan were used to investigate patterns of genetic variation. The mean expected heterozygosity (He) was 0.128—ranging from 0.031 (Matsu) to 0.442 (Kaoping)—and the mean observed heterozygosity (Ho) was 0.086—ranging from 0.017 (Kaohsiung) to 0.215 (Kaoping). Both AMOVA and the high overall mean FST of 0.252 indicated enormous genetic differentiation among populations and the positive mean value of FIS was 0.328, indicating a deficiency of heterozygotes. PCoA indicated that the samples of M. cephalus could be split into three groups and STRUCTURE analysis showed that all individuals were grouped into three genetic clusters. The results of mutation-drift equilibrium tests did not suggest that the populations experienced any recent genetic bottleneck. The results from all localities in the present investigation showed significant change in the GPI-A genotype frequencies with latitudes—e.g., increases in GPI-A*135/135 homozygote frequencies and GPI-A*100/100 frequencies were highly correlated with latitudinal cline. All migratory populations with the GPI-A genotype were almost exclusively the GPI-A*100/100 homozygote. During the life history of M. cephalus, the GPI-A*100/135 heterozygote frequency significantly decreases with age. Conclusions: Based on these data, we suggest that each GPI-A genotype represents trait combinations of higher fitness in some portions of the environment. Furthermore, the genotypic frequencies change in accordance with life stages, suggesting that selection occurs throughout the life span.

Microsatellite polymorphism based genetic variation in two sympatric species of Drosophila: D.bipectinata and D. malerkotliana

Drosophila bipectinata and D. malerkotliana are found to be distributed all along the Oriental-Australian continents and have common phylogenetic descent. The genetic divergence of these two species have been studied by using genetic markers like chromosome inversions and allozyme variants to establish the extent of variation they have experienced since their speciation. In this study, microsatellite variations have been considered to observe the genetic differentiation among the seven natural populations of D. bipectinata and six populations of D. malerkotliana. Results pertaining to both the species indicate that the level of average heterozygosity increases from north to south. Distinct genetic differentiation has been observed between north and south populations of both the species giving an indication that north and south populations have undergone genetic structuring due to absence of gene flow between them and varying environmental conditions. Based on the frequencies of microsatellite variants of the two species, we have computed the level of variation between these two species. The analysis in this regard shows an almost similar trend of genetic variation being experienced by these two species which could be a kind of parallel evolution occurring due to similar ecological niches occupied by them and similar impact of evolutionary forces.

The molecular background of the aspartate aminotransferase polymorphism in Littorina snails maintained by strong selection on small spatial scales

Allozymes present several classical examples of divergent selection, including the variation in the cytosolic aspartate aminotransferase (AAT) in the intertidal snails Littorina saxatilis. AAT is a part of the asparate-malate shuttle, in the interidal molluscs involved in the anaerobic respiration during desiccation. Previous allozyme studies reported the sharp gradient in the frequencies of the AAT100and the AAT120 alleles between the low and high shores in the Northern Europe and the differences in their enzymatic activity, supporting the role of AAT in adaptation to desiccation. However, the populations in the Iberian Peninsula showed the opposite allele cline. Using the mRNA sequencing and the genome pool-seq analyses we characterize DNA sequences of the different AAT alleles, report the amino acid replacements behind the allozyme variation and show that same allozyme alleles in Northern and Southern populations have different protein sequences. Gene phylogeny reveals that the AAT100 and the northern AAT120 alleles represent the old polymorphism, shared among the closely related species of Littorina, while the southern AAT120 allele is more recently derived from AAT100. Further, we show that the Aat gene is expressed at constitutive level in different genotypes and conditions, supporting the role of structural variation in regulation of enzyme activity. Finally, we report the location and the structure of the gene in the L. saxatilis genome and the presence of two additional non-functional gene copies. Altogether, we provide a missing link between the classical allozyme studies and the genome scans and bring together the results produced over decades of the genetic research.

Malic enzyme, an “old-new player” in age at maturity in Atlantic salmon

Traditional genetic markers based on allozyme variation had indicated that in Atlantic salmon the genetic variation found for the locus coding for mMEP-2* could be adaptive, with the variation being related to river water temperature, growth, and maturation. More recently, SNP panels used to search for genes related to maturation in Atlantic salmon identified several genes, including the vgll3 gene related to early maturation. However, none of the analyses performed found an association between maturation and the already known locus coding for mMEP-2*. Recently, a method has been developed to characterize the different alleles of the locus coding for mMEP-2* using molecular techniques. In this work we use this method to study the salmon population of the Bidasoa River, located in the Iberian Peninsula, which is the limit of distribution of the species. We found a relationship between the presence of SNP G, equivalent to the 125* allele, and early maturation of Atlantic salmon in both males and females. It is possible that the relationship between the different alleles of this locus and maturation is not direct but is produced by differential growth during the juvenile and/or adult phase. It is also plausible that this association is exclusive to the salmon populations of the Iberian Peninsula.

DNA polymorphism underlying allozyme variation at a malic enzyme locus (mMEP-2*) in Atlantic salmon (Salmo salar L.).

A non-synonymous single nucleotide polymorphism (SNP) underlies a diallelic allozyme polymorphism at the mitochondrial NADP-dependent mMEP-2* locus in Atlantic salmon (Salmo salar L.). The resultant amino acid substitution, which alters the charge of the allelic products, matches the differential mobility of the two allozyme alleles, whereas allozyme and SNP assays revealed genotyping concordance in 257 of 258 individuals. A single mismatch, homozygous allozyme vs. heterozygote SNP, suggests the presence of a second, less common null allele.

Cyperaceae in a data‐rich era: New evolutionary insights from solid frameworks

Cyperaceae in a data‐rich era: New evolutionary insights from solid frameworks

A New Two-Lined Salamander (Eurycea bislineata Complex) from the Sandhills of North Carolina

The Eurycea bislineata complex (“two-lined salamanders”) of eastern North America contains six described species, of which three have very similar morphologies and relatively broad geographic distributions, and three have more divergent morphologies with narrow geographic distributions. Recent molecular phylogenetic analyses found that four of the six species in the complex contain deep genetic structure, and that two of the species (E. cirrigera and E. wilderae) are paraphyletic in mitochondrial and nuclear DNA, inferring that current taxonomy does not reflect actual species boundaries in the complex. The member of this complex in the Sandhills physiographic region of south-central North Carolina, USA, is notable for its distinctive coloration and ecology, and a study on allozymic variation published over 30 years ago demonstrated that it is genetically distinct but clustered within the paraphyletic E. cirrigera. This study investigates the taxonomic status of the Sandhills population using morphology, mitochondrial DNA, and a 21-locus nuclear DNA data set to test if the Sandhills taxon represents a local ecomorph that is conspecific with adjacent populations of E. cirrigera, or if it represents a divergent evolutionary lineage that warrants taxonomic recognition. Mitochondrial and nuclear DNA revealed that the Sandhills taxon is genetically distinct and phylogenetically unrelated to adjacent populations of E. cirrigera. Principal components analysis of 316 adult specimens of the Sandhills taxon and the three morphologically similar species in the complex found considerable overlap among these taxa, but pairwise comparisons of heavily loading morphological characters showed that the Sandhills taxon usually has a shorter body, shorter tail, and narrower head. Based on these corroborated lines of evidence, the hypothesis that the Sandhills taxon represents only a local ecomorph is rejected and it is described as a new species. Clarification of the extent of its geographic range (including its possible presence in South Carolina), differentiation of larvae from other members of the complex, and verification of hypothesized narrow zones of hybridization with E. cirrigera at the peripheries of its geographic range are needed. The description of the Sandhills taxon brings the number of endemic salamander species in North Carolina to seven. Integrative taxonomic revisions of the E. bislineata complex, particularly E. cirrigera and E. wilderae, are needed to estimate species diversity and distributions of these salamanders more accurately.

Geographical pattern of genetic diversity in Capsella bursa-pastoris (Brassicaceae)-A global perspective.

We analyzed the global genetic variation pattern of Capsella bursa‐pastoris (Brassicaceae) as expressed in allozymic (within‐locus) diversity and isozymic (between‐locus) diversity. Results are based on a global sampling of more than 20,000 C. bursa‐pastoris individuals randomly taken from 1,469 natural provenances in the native and introduced range, covering a broad spectrum of the species’ geographic distribution. We evaluated data for population genetic parameters and F‐statistics, and Mantel tests and AMOVA were performed. Geographical distribution patterns of alleles and multilocus genotypes are shown in maps and tables. Genetic diversity of introduced populations is only moderately reduced in comparison with native populations. Global population structure was analyzed with structure, and the obtained cluster affiliation was tested independently with classification approaches and macroclimatic data using species distribution modeling. Analyses revealed two main clusters: one distributed predominantly in warm arid to semiarid climate regions and the other predominantly in more temperate humid to semihumid climate regions. We observed admixture between the two lineages predominantly in regions with intermediate humidity in both the native and non‐native ranges. The genetically derived clusters are strongly supported in macroclimatic data space. The worldwide distribution patterns of genetic variation in the range of C. bursa‐pastoris can be explained by intensive intra‐ and intercontinental migration, but environmental filtering due to climate preadaption seems also involved. Multiple independent introductions of genotypes from different source regions are obvious. “Endemic” genotypes might be the outcome of admixture or of de novo mutation. We conclude that today's successfully established Capsella genotypes were preadapted and found matching niche conditions in the colonized range parts.

Seed Total Protein Profiling in Discrimination of Closely Related Pines: Evidence from the Pinus mugo Complex.

The Pinus mugo complex includes several dozen closely related European mountain pines. The discrimination of specific taxa within this complex is still extremely challenging, although numerous methodologies have been used to solve this problem, including morphological and anatomical analyses, cytological studies, allozyme variability, and DNA barcoding, etc. In this study, we used the seed total protein (STP) patterns to search for taxonomically interesting differences among three closely-related pine taxa from the Pinus mugo complex and five more distant species from the Pinaceae family. It was postulated that STP profiling can serve as the backup methodology for modern taxonomic research, in which more sophisticated analyses, i.e., based on the DNA barcoding approach, have been found to be useless. A quantitative analysis of the STP profiles revealed characteristic electrophoretic patterns for all the analyzed taxa from Pinaceae. STP profiling enabled the discrimination of closely-related pine taxa, even of those previously indistinguishable by chloroplast DNA barcodes. The results obtained in this study indicate that STP profiling can be very useful for solving complex taxonomic puzzles.

Analysis of genetic diversity in oilseed brassica germplasm through ISSR markers and isozyme profiling

Eleven Brassica germplasm were characterized through the application of 12 oligonucleotide Inter Simple Sequence Repeat (ISSR) primers. A total 1248 bands were amplified through polymorphic chain reaction and were visualized by agarose gel electrophoresis. Among the amplified marker bands 71.47% were polymorphic in nature and 352 bands were found to be monomorphic. The polymorphic bands of the amplified DNAs mostly ranged between 110 bp and 3 kb. Genetic distance among the germplasm ranged between 0.0468 and 0.7189. Moreover, three isozyme systems such as esterase, acid phosphatase and peroxidase were analyzed for allozyme variability that detected distinct 93 isozyme loci of which nearly 61.9% were polymorphic. Two dendrograms were constructed based on the ISSR profiling and isozyme data obtained through electrophoresis to find out the relatedness and phylogenetic relationship among the investigating Brassica germplasm. The clusters of the phylogenetic tree revealed 4 distinct groups of Brassica based upon their ISSR banding patterns and isozyme analysis. Nei’s genetic distance analysis provided strong information about the existence of variability among the germplasm of Brassica. All the germplasm was found to be clustered according to their respective species. Brassica carinata (Ethiopian mustard) showed individuality from all the germplasm studied and made a different branch in the phylogenetic tree suggesting its diverse origin. From the clustering pattern and genetic relationship obtained with ISSR markers and isozyme analysis, breeders can successfully identify the diverse germplasm from different cluster and use them in their future breeding program.

The genetically healthy terrestrial orchid <i>Liparis krameri</i> on southern Korean Peninsula

Neutral genetic diversity found in plant species usually leaves an indelible footprint of historical events. Korea’s main mountain range (referred to as the Baekdudaegan [BDDG]), is known to have served as a glacial refugium primarily for the boreal and temperate flora of northeastern Asia. In addition, life-history traits (life forms, geographic range, and breeding systems) influence the within- and among-population genetic diversity of seed plant species. For example, selfing species harbor significantly less within-population genetic variation than that of predominantly outcrossers. A previous study of two Liparis species (L. makinoana and L. kumokiri) emphasizes the role of the abovementioned factors shaping the levels of genetic diversity. Liparis makinoana, mainly occurring on the BDDG and self-incompatible, harbors high levels of within-population genetic diversity (expected heterozygosity, HeP = 0.319), whereas there is no allozyme variation (HeP = 0.000) in L. kumokiri, which is self-compatible and mainly occurs in lowland hilly areas. To determine if this trend is also found in other congeners, we sampled five populations of L. krameri from the southern part of the Korean Peninsula and investigated the allozyme-based genetic diversity at 15 putative loci. The somewhat intermediate levels of within-population genetic variation (HeP = 0.145) found in L. krameri are most likely due to its occurrence in mountainous areas that, despite being outside of the main ridge of the BDDG, still served as refugia, and a self-incompatible breeding system. Management strategies are suggested for L. krameri and L. makinoana based on the levels and distribution of genetic diversity and inbreeding.

Evaluation of the taxonomic rank of the terrestrial orchid <i>Cephalanthera subaphylla</i> based on allozymes

The taxonomic rank of the tiny-leaved terrestrial orchid Cephalanthera subaphylla Miyabe & Kudo has been somewhat controversial, as it has been treated as a species or as an infraspecific taxon, under C. erecta (Thunb.) Blume [C. erecta var. subaphylla (Miyabe & Kudo) Ohwi and C. erecta f. subaphylla (Miyabe & Kudo) M. Hiro]. Allozyme markers, traditionally employed for delimiting species boundaries, are used here to gain information for determining the taxonomic status of C. subaphylla. To do this, we sampled three populations of five taxa (a total of 15 populations) of Cephalanthera native to the Korean Peninsula [C. erecta, C. falcata (Thunb.) Blume, C. longibracteata Blume, C. longifolia (L.) Fritsch, and C. subaphylla]. Among 20 putative loci resolved, three were monomorphic (Dia-2, Pgi-1, and Tpi-1) across the five species. Apart from C. longibracteata, there was no allozyme variation within the remaining four species. Of the 51 alleles harbored by these 17 polymorphic loci, each of the 27 alleles at 14 loci was unique to a single species. Accordingly, we found low average values of Nei’s genetic identities (I) between ten species pairs (from I = 0.250 for C. erecta versus C. longifolia to I = 0.603 for C. falcata vs. C. longibracteata), with C. subaphylla being genetically clearly differentiated from the other species (from I = 0.349 for C. subaphylla vs. C. longifolia to 0.400 for C. subaphylla vs. C. falcata). These results clearly indicate that C. subaphylla is not genetically related to any of the other taxa of Cephalanthera that are native to the Korean Peninsula, including C. erecta. In a principal coordinate analysis (PCoA), C. subaphylla was positioned distant not only from C. falcata, C. longibracteata, and C. longifolia, but also from C. erecta. Finally, K = 5 was the best clustering scheme using a Bayesian approach, with five clusters precisely corresponding to the five taxa. Thus, our allozyme results strongly suggest that C. subaphylla merits the rank of species.

Ecotypic divergences of the alpine herb Potentilla matsumurae adapted to fellfield-snowbed habitats across a series of mountain sky islands.

Divergent selection due to environmental heterogeneity can lead to local adaptation. However, the ecological and evolutionary processes of local adaptation that occurs across multiple regions are often unknown. Our previous studies reported on the ecotypic divergence within a local area of variation of Potentilla matsumurae, an alpine herb adapted to the fellfield-snowbed environment. Here we investigated large-scale geographic patterns of ecotypic differentiation in this species to infer local adaptation and selective forces across multiple regions. We compiled information on the overall distributions of fellfield and snowbed habitats on the mountains in Japan across the distribution of the species. Next, we conducted common garden experiments to test the adaptive divergence of the fellfield-snowbed plants derived from multiple regions. Finally, we evaluated phylogeographic structures based on cpDNA and allozyme variations and inferred the evolutionary history of ecotype differentiation. The mosaic distribution of the fellfield-snowbed ecotypes across isolated mountaintops constitutes indirect evidence for habitat-specific natural selection. The significant difference in survivorship between the ecotypes observed in a controlled snow environment provides more substantial evidence of local selection. Phylogeographic structures support the hypothesis that ecotypic divergence events from fellfield to snowbed populations occurred independently in at least two distinct regions. Ecotypic divergence of P. matsumurae has occurred across a series of mountain sky islands. Local selection in snowy environments is a driving force that maintains the divergent ecotypes across multiple mountain regions and can contribute to the diversification of plants in heavy-snow regions.

Genetic Differentiation of Citrullus colocynthis L. Populations Depending on Allozyme Diversity

CITRULLUS colocynthis (L.) is a desert plant having a large history in pharmaceutical industries as an important medicinal plant. Allozyme variation and population genetic structure of C. colocynthis in 6 natural populations from western region, Saudi Arabia, were investigated by 6 enzyme systems. The genetic differentiation within and among C. colocynthis populations has been revealed by allozyme analysis. Ten loci were monomorphic in all populations, whereas seven loci having two alleles (α-EST-1, β-EST-1, MDH-1, ADH-4, ADH-5, ALO-4 and PRX-2) were polymorphic. The mean allozyme variability indices within C. colocynthis populations (P = 31.17%; A = 1.21) were lower than those for insect-pollinated species (P = 34%; A = 2.67; He = 0.205) except He value (0.415) was higher. The observed mean heterozygosity (Ho= 0.757) was higher than the expected mean heterozygosity (He= 0.415) indicating the existence of natural selection against homozygosity. The Inbreeding coefficient values (F) of polymorphic loci were negative suggesting a significant excess of heterozygosity in the studied populations. The UPGMA dendrogram of 84 individuals of C. colocynthis confirmed the notable variability within populations. Differentiation among-population (FST) recorded 16.2% of the total variation. Low FST and high genetic distance (D) values suggested a low differentiation among C. colocynthis populations. Little gene flow (Nm ) was deduced in all populations except ME based on the allozyme data. We suggest that population ME can be recommended for both genetic conservation and breeding programs.

Features of Spatial Structure of Mikizha Parasalmo mykiss in the Kol River, Western Kamchatka: On the Problem of the Population Integration in the Complex River System

The features of within-river migrations, biological and morphological characteristics, and allozyme variation are studied in mikizha Parasalmo mykiss in the Kol River basin, Western Kamchatka. In this river system with a complex geomorphology, mikizha spawns in tundra-type tributaries, and each tributary is characterized by a certain combination of size, water content, hydrological, and thermic regime. Therefore, the spawning conditions, as well as spatial distribution and biological characteristics of the progeny, are variable. Based on the mark-recapture data, mikizha intensively migrates within the river system, and it does not show any fidelity to certain sites; the spawners can enter different tributaries in various years. Based on the variation of morphometric characters, the difference between the juveniles from various tributaries is absent. The results of allozyme variation show that, despite a mosaic structure of the habitats, mikizha of the Kol River is represented by a single population with a common genofond. Based on the results of this study, it is concluded that mikizha of the Kol River is a single and highly integrated population despite the factors facilitating the diversity. A mechanism of a stable population unity is connected with the within-river migrations, and the spawners are redistributed in different tributaries of the river during each year. This redistribution is directed against the founder effect and gene drift.

Hybridisation and detection of a hybrid zone between mesic and desert ragworts (Senecio) across an aridity gradient in the eastern Mediterranean

ABSTRACTBackground: Hybrid zones provide excellent opportunities for studying plant adaptation and speciation.Aims: We tested whether two herbaceous species of Senecio, S. vernalis and S. glaucus, hybridise in the eastern Mediterranean region and form a hybrid zone across an aridity gradient in the Jordan Rift Valley.Methods: Allozyme variation surveyed across both species was analysed by the programme STRUCTURE to assign individuals to genetic groups and determine levels of admixture. Populations in the Jordan Rift Valley were subsequently subjected to a cline analysis.Results: STRUCTURE showed that interspecific hybrids were produced at low frequency along the Israeli coastal plain where S. glaucus is represented by ssp. glaucus. In contrast, hybrids were more commonly produced in central populations of the Jordan Rift Valley. Here, the two species form a hybrid zone with S. vernalis occurring in mesic sites to the north and S. glaucus (ssp. coronopifolius) in arid sites to the south. Cline analysis showed that the hybrid zone is centred towards the northern end of the Dead Sea, but the analysis failed to distinguish how it is maintained.Conclusions: Future detailed genetic and ecological analysis of the Senecio hybrid zone should improve our understanding of plant adaptation and speciation across aridity gradients.

Genetic diversity of the extremely rare Habenaria dentata and the rare Habenaria linearifolia (Orchidaceae) in South Korea: implications for population history and conservation

Background and aims – Since historical events often leave an indelible mark on levels of genetic diversity of plant populations, one may indirectly infer their evolutionary history with the help of current patterns of genetic diversity. The terrestrial orchid Habenaria dentata, an element of warm-temperate/subtropical vegetation, reaches its northernmost limits in the Korean Peninsula, and thus it is extremely rare there. As H. dentata was absent from the Peninsula during the Last Glacial Maximum (LGM), it is likely to be of post-glacial origin having arrived from either a single refugium or multiple refugia. However, its rare, temperate/boreal congener H. linearifolia might have persisted in situ in either macrorefugia or microrefugia on the Peninsula during the LGM.Methods – To test which hypothesis is most appropriate for each species, we investigated levels of allozyme-based (17 loci) genetic diversity and population genetic structure in the two only known populations of H. dentata and in 12 populations of H. linearifolia.Key results – No allozyme diversity was found in H. dentata (He = 0.000), whereas H. linearifolia exhibited low within-population variation (He = 0.060) and high among-population differentiation (FST = 0.237). We found little association between populations in relation to their geographic location; several populations presented individuals belonging to different clusters.Conclusions – Our results suggest that H. dentata likely originated from a single ancestral population (perhaps from southern Japan or southern China) through post-glacial dispersal, whereas H. linearifolia probably survived the LGM in situ in microrefugia situated at low to mid-elevated regions. We further suggest that separate conservation strategies for each species should be employed, given that the two taxa have different ecological and demographic traits and harbour different levels of genetic diversity.

Lack of allozyme variation in the two carnivorous, terrestrial herbs Utricularia bifida and Utricularia caerulea (Lentibulariaceae) co-occurring on wetlands in South Korea: Inference of population history

This research was supported by Basic Science Program through the National Research Foundation of Korea (NRF-2017R1A2B4012215) funded by the Ministry of Education, Science and Technology to M.G.C.

Patterns of Genetic Diversity in Rare and Common Orchids Focusing on the Korean Peninsula: Implications for Conservation

To provide basic information for orchid conservation, we surveyed the plant allozyme literature to summarize genetic diversity and structure data for (i) rare orchids native to the Korean Peninsula, and (ii) their congeners irrespective of being common and rare or Korean or not. A total of 68 taxa (32 taxa in Korea and 37 outside Korea; Goodyera repens being included in both datasets) were considered in this study. Overall, rare Korean orchid species had significantly lower levels of genetic diversity than their common congeners and common orchids in general at both population and species levels. However, mean values of G ST (or F ST) for rare and common orchids (Korean or not) did not differ significantly from each other. We found patterns of both low and high genetic diversity in rare Korean orchids. Many rare orchids harbored a complete lack of allozyme variation or extremely low within-population variation, perhaps due to rarity associated with random genetic drift and/or, for the case of warm-temperate orchids, to founder effects during post-glacial re-colonization. In contrast, high levels of genetic variation were found for a few orchids that have become recently rare (due to over-collection during the past several decades), probably because there have not been sufficient generations for the initial diversity to be substantially eroded. In addition, several orchids occurring in the main mountain system of the Korean Peninsula (the Baekdudaegan), that served as a glacial refugium, maintained moderate to high levels of within-population genetic diversity. Based on our genetic data, conservation priority should be given to rare orchid species. Particularly, urgent measures should be implemented on Jeju Island, a popular vacation spot, because it also a hotspot for threatened orchids with low levels of genetic diversity.

Recurrent origin of peripheral, coastal (sub)species in Mediterranean Senecio (Asteraceae)

Background: It is argued that coastal endemic taxa may evolve in parallel at the periphery of the distributional range of a widespread species.Aims: We tested this hypothesis for the origins of three peripheral, coastal isolates of Senecio, S. glaucus ssp. glaucus (Israel), S. g. ssp. coronopifolius p.p. (Sicily), and S. hesperidium (Morocco), from widespread S. glaucus ssp. coronopifolius. We also determined the relative roles of selection vs. genetic drift in shaping phenotypic divergence in ssp. glaucus and S. hesperidium, using Lande’s test of neutral morphological change.Methods: We surveyed morphological and/or allozyme variation in the three peripheral isolates and mainly inland populations of S. g. ssp. coronopifolius.Results: Genetic data supported independent origins of the coastal taxa from nearby populations of ssp. coronopifolius. These descendant and ancestral populations showed pronounced morphological but weak genetic differentiation. Phenotypic similarities between ssp. glaucus (Israel) and S. hesperidium (Morocco) in plant height and floral traits may have resulted from parallel divergent selection from ssp. coronopifolius, though drift remains an alternative cause in S. hesperidium.Conclusions: Our results indicate parallel ecotype formation and (sub)speciation in Senecio in which primarily selective vs. neutral determinants promoted the recurrent origin of coastal types in, respectively, Israel and Morocco.