Àngel Romo

High level of genetic differentiation of Juniperus phoenicea (Cupressaceae) in the Mediterranean region: geographic implications

Fourteen natural populations of Juniperus phoenicea L. from the quite entire species range have been compared using isoenzyme polymorphism. Among 17 loci, 5 (Got1, 6Pgd3, Pgi2, Pgm2 and Shdh2) appeared to be differentiated sufficiently to provide useful information for discrimination between the subspecies phoenicea and turbinata (Guss.) Nyman. Two distinct groups of populations were detected using the Nei’s genetic distance unweighted pair group method with arithmetic mean (UPGMA) and discrimination analyses, one including the inland populations of the eastern Iberian Peninsula and southern France (subsp. phoenicea), and the second from the Mediterranean and Atlantic shores, and from the Atlas mountains in Africa (subsp. turbinata). The high level of differences confirms a long period of isolation, probably during the whole Pleistocene. The population from the Aegean Sea shore differed from the other Mediterranean shore plus Atlas mountain population. It also suggests spatial isolation between them, at least during the last Glaciation.

Population genetic structure of Juniperus phoenicea (Cupressaceae) in the western Mediterranean Basin: gradient of diversity on a broad geographical scale

Abstract• Introduction, Material and MethodsThe genetic structure and diversity of ten natural populations of Juniperus phoenicea L. from the western part of the species range have been studied using random amplified polymorphic DNA (RAPD) markers.• Results and discussionAmong 10 analyzed primers only 3 reproduced consistently across successful PCR reactions and gave 45 loci. The percentage of polymorphic loci (P) and Nei’s heterozygosity (He) have average values of 64.9% and 0.177. The average expected heterozygosity of particular populations positively correlate with latitude and negatively with altitude (τ = 0.556, P = 0.025; τ = −0.494, P = 0.047, respectively). The proportion of genetic variation contributed by the differences between populations was low (GST  = 0.056). The gene flow (Nm) has an average value of 4.2, and was higher in subsp. turbinata (7.3) than in subsp. phoenicea (4.1). Significant proportion of the variation (ΦST = 0.106) was attributable to differences among populations, as revealed in analysis of molecular variance analysis of pair-wise RAPD distances. No evidence for isolation by distance was detected in Mantel test on genetic (ΦST) and geographic distances. European populations differed at a higher level from the African, subsp. phoenicea from turbinata (3.97% and 3.14% of total variance, respectively). The significant level of differences between European and African populations can result from (1) the earlier divergence and considerably low level of gene flow between them, or (2) a different mutation rate within population of different continent.• ConclusionThe results suggest rather local forest economy with J. phoenicea, without seed exchange on large distance.

Morphological versus molecular markers to describe variability in Juniperus excelsa subsp. excelsa (Cupressaceae)

This is a large scale investigation of morphological diversity in Juniperus excelsa excelsa. It offers complementary results to those obtained for the same populations using molecular markers. These two approaches are complementary and should be considered together in order to obtain a comprehensive view of the variability of J. excelsa excelsa.

Relationships among Cedrus libani, C. brevifolia and C. atlantica as revealed by the morphological and anatomical needle characters

The main aim of the present study was testing the value of the morphological and anatomical characteristics of the needles in distinguishing Cedrus atlantica, C. libani and C. brevifolia. Nine populations were sampled in their natural habit and 25 characters were used to describe the variation of the brachyblast needles and to analyze the differences between species. The results indicated that morphological and anatomical needle characters provide valuable tools in discrimination of the taxa. The scored differences were statistically significant, as revealed in the Tukey’s t test, discrimination analysis and hierarchical analysis of variation. The results support treating C. libani, C. atlantica and C. brevifolia as independent species.

Morphological differentiation supports the genetic pattern of the geographic structure of Juniperus thurifera (Cupressaceae)

Juniperus thurifera is an important component of woodland communities of dry sites within the West Mediterranean region and is characterised by a strongly disjunctive geographic range. Two subspecies were recognised, subsp. thurifera in Europe and subsp. africana in Africa. The aim of the study was the comparison of phenetic diversity to the pattern of AFLP geographic differentiation of the species described in the literature. The examination of phenetic diversity was based on the biometrical analysis of 17 populations using 12 morphological characters of cone and seed. The differences among populations were analysed using Student’s t test, analysis of discrimination, UPGMA agglomeration and hierarchical analysis of variance. The majority of morphological characters differentiated at a statistically significant level between populations and between J. thurifera subsp. thurifera and subsp. africana. Three groups of populations were detected using multivariate statistical analyses. The first, well separated, is subsp. africana, while the following two concern subsp. thurifera. The morphological differentiation of populations appeared similar to that described on the AFLP. The Gibraltar Straight appeared to be the most important barrier.

Morphological diversity and structure of West Mediterranean Abies species

The aim of this study was the biometrical comparison of Abies pinsapo Boiss., Abies maroccana Trab. and Abies tazaotana Côzar ex Villar from Spain and Morocco. The morphological and anatomical analysis of the needle characters of these firs revealed significant taxonomic differences. The results showed considerable distances between regions and very small differences among the Moroccan fir taxa. The examination of the needles and earlier genetic analysis did not provide evidence for distinguishing A. tazaotana at the species level.

Distance between south-European and south-west Asiatic refugial areas involved morphological differentiation: Pinus sylvestris case study

The phenotypic differentiation of relic P. sylvestris in southern Europe and southwestern Asia was verified using thirty-two populations sampled from the Iberian Peninsula, Massif Central, Balkan Peninsula, Crimea and Anatolia. Twenty-one morphological and anatomical needle traits and 18 cone morphological characteristics were examined to describe the population diversity and differentiation. The needle characters were not correlated to those of cone. The differences between regions were significant based on 12 needle and 9 cone characteristics, suggesting spatial isolation. The differentiation between the Iberian and Anatolian populations was the highest, which indicates the isolation by distance. The high level of morphological differentiation was also found among Iberian populations, supporting the already known complex history of the species in that region. Populations within other regions were differentiated at lower levels; however, the West Anatolian populations differed morphologically from the eastern ones. The described pattern of morphological differentiation supports the idea of the long-lasting existence of P. sylvestris in the south-European and Anatolian mountain regions. To conserve this variation, seed transfer between regions in the forest economy should be restricted.

Genome size and ploidy levels in highly fragmented habitats: the case of western Mediterranean Juniperus (Cupressaceae) with special emphasis on J. thurifera L.

Mediterranean junipers are of special ecological importance as key components of resource islands in semi-arid mountain ecosystems of the Mediterranean basin. The fragmentation of their habitat, which was primarily natural and driven by climatic drought conditions, is currently being aggravated by anthropogenic pressure. In the framework of this concern, the present work aims to contribute establishing a genomic profile of Juniperus in its western Mediterranean range, with a special emphasis placed on J. thurifera. DNA contents were assessed by flow cytometry in 43 populations of nine taxa within their Mediterranean range (first reports for J. navicularis, J. thurifera subsp. africana and J. thurifera subsp. thurifera). Chromosome numbers were determined by orcein staining in eight taxa (first counts for J. oxycedrus subsp. badia, J. phoenicea subsp. phoenicea, J. phoenicea subsp. turbinata, of 2n = 2x = 22, and for J. thurifera subsp. thurifera, of 2n = 4x = 44). Tetraploid cytotypes have been the only ones found in the 19 populations of J. thurifera studied, this being the first report of a Juniperus species exclusively polyploid. In J. thurifera, C-value does not respond to habitat fragmentation, in the same way that genetic diversity within populations was previously shown to be unaltered, suggesting that this factor has not had, at least to date, a significant impact on populations at genomic and genetic levels. Habitat fragmentation leads to deeply age-biased populations with a male-biased imbalanced sex ratio (lack of females), indicating an urgent need to improve regeneration within the populations of this species.

Genome size variation in gymnosperms under different growth conditions

The genome is structurally and functionally influenced by ecological factors during adaptive processes. Several natural factors can cause this, and here we present the effects of different growth conditions on the genome size. Genome size assessments were carried out by flow cytometry for a set of 19 taxa for each of three growing conditions: (i) wild plants growing in their natural habitats used as a control group; (ii) potted plants; and (iii) bonsai plants. Our results show a large variation in the genome size of bonsai and potted plants compared to their wild representatives. The most important conclusion is that 1Cx values measured in potted plants can be up to 8.48% lower and in bonsai plants up to 26.83% higher than the values assessed for the respective wild individuals. In the case of Juniperus thurifera, this divergence largely exceeded the genome size variation previously estimated along the natural geographical range of the species. Such deviation from expected values could be interpreted as genuine genome size variation, or to result from biochemical or/and DNA compactness changes triggered by growth conditions. The present results provide evidence for plant response to human-induced environmental changes, thus making the current approach potentially interesting for the prediction of the influence of climate change on plants and for other applications.

Taxonomic and geographic differentiation of Juniperus phoenicea agg. based on cone, seed, and needle characteristics

The aim of this study was to examine the diversity of, and differentiation between, 41 natural populations representing Juniperus phoenicea complex within their geographic range using the morphological characteristics of cones, seeds, and sprouts with leaves. Seven populations of J. phoenicea s.s., 25 J. turbinata and nine J. canariensis, each represented by ∼20–30 individuals, were studied. The characteristics describing the size of cones and seeds and their proportions were different between J. phoenicea s.s., J. turbinata, and J. canariensis, and were useful in distinguishing between these three taxa. The populations of J. canariensis had a significantly higher percentage of trimerous cones, a higher number of cone scales, but a lower number of seeds, which were also larger than the seeds from other taxa. Juniperus phoenicea s.s., J. turbinata, and J. canariensis revealed a high level of multivariate differentiation, but there were no single characteristics which allowed one to distinguish between these alone. We detected significant differences between populations of J. turbinata from Europe and Africa, which supports the role of the Gibraltar Straight in the structuring of conifer species. Significant differences were also detected between European and Asiatic populations in several characters examined, indicating the important role of the Aegean Sea in the structuring of this taxon.