Orlanda C. B. Moreira

Bio: Orlanda C. B. Moreira is an academic researcher from University of the Azores. The author has contributed to research in topics: Population & Genetic variation. The author has an hindex of 6, co-authored 6 publications receiving 107 citations.

Polyploidy and microsatellite variation in the relict tree Prunus lusitanica L.: how effective are refugia in preserving genotypic diversity of clonal taxa?

Abstract: Refugia are expected to preserve genetic variation of relict taxa, especially in polyploids, because high gene dosages could prevent genetic erosion in small isolated populations. However, other attributes linked to polyploidy, such as asexual reproduction, may strongly limit the levels of genetic variability in relict populations. Here, ploidy levels and patterns of genetic variation at nuclear microsatellite loci were analysed in Prunus lusitanica, a polyploid species with clonal reproduction that is considered a paradigmatic example of a Tertiary relict. Sampling in this study considered a total of 20 populations of three subspecies: mainland lusitanica (Iberian Peninsula and Morocco), and island azorica (Azores) and hixa (Canary Islands and Madeira). Flow cytometry results supported an octoploid genome for lusitanica and hixa, whereas a 16-ploid level was inferred for azorica. Fixed heterozygosity of a few allele variants at most microsatellite loci resulted in levels of allelic diversity much lower than those expected for a high-order polyploid. Islands as a whole did not contain higher levels of genetic variation (allelic or genotypic) than mainland refuges, but island populations displayed more private alleles and higher genotypic diversity in old volcanic areas. Patterns of microsatellite variation were compatible with the occurrence of clonal individuals in all but two island populations, and the incidence of clonality within populations negatively correlated with the estimated timing of colonization. Our results also suggest that gene flow has been very rare among populations, and thus population growth following founder events was apparently mediated by clonality rather than seed recruitment, especially in mainland areas. This study extends to clonal taxa the idea of oceanic islands as important refugia for biodiversity, since the conditions for generation and maintenance of clonal diversity (i.e. occasional events of sexual reproduction, mutation and/or seed immigration) appear to have been more frequent in these enclaves than in mainland areas.

Seed Germination and Seedling Growth of the Endangered Azorean Cherry Prunus azorica

Abstract: Prunus azorica is an Azorean endemic tree considered as a priority species for conservation. It is important as a laurel forest component, particularly at medium altitude, and as a food source for the endangered bird Pyrrhula murina. The best conditions for seed germination were investigated after removal of the outer layers of the fruit by determining the effect of 1) using stones or seeds; 2) stratification regime (six treatments and a control); 3) incubation temperature (four alternating temperature regimes); and 4) gibberellic acid concentration (three levels). This resulted in a fully factorial design with 168 (2 · 7 · 4 · 3) treatments with three replicates per treatment and 25 seeds per replicate. Cumulative germination percentages were determined at the end of the trial. Globally, there was a significant effect of endocarp removal (49% germination with seeds and 15% with stones). Both for stones and seeds, there was a significant effect of incubation temperature, stratification regime, and growth regulator concentration. Stones attained a maximum germination of '80% under several stratification treatments including cold (4 8C) or warm (20 8C) followed by cold and at 10/5 8C without the addition of a growth regulator. Seeds attained a maximum germination of greater than 90% without stratification at 10/5 or 15/10 8C without the addition of a growth regulator. During the stratification process, germination occurred only for seeds, particularly for longer treatments, for example, those corresponding to 3 or more months of stratification, including warm followed by cold (75% to 80%) or cold alone (77%). According to seed morphology and germination results, the seed appears to have a non-deep physiological dormancy. Seeds ofP. azorica can thus be efficiently germinated after endocarp removal at temperatures of 10/5 or 15/10 8C with a daily light period of 12 hours. This protocol allowed producing hundreds of viable seedlings that were used in the reforestation of a laurel forest stand in a LIFE project.

Morphophysiological dormancy and germination in seeds of the Azorean tree Picconia azorica

Abstract: Picconia azorica (Oleaceae) is an Azorean tree with high ecological value. We investigated possible causes for P. azorica seed dormancy and the germination conditions to break it, using acid scarification (scarified stones) or complete removal of the endocarp (seeds), in conjunction with different stratification and incubation temperature regimes and gibberellic acid (GA3) treatments. Embryos in ripe drupes were subspatulate, axile and occupied 60% of the endosperm length. Water imbibition was verified for both acid scarified stones and seeds. The highest total phenolic compounds content occurred in the seed coat (36.4 ± 1.51 mg GAE g-1 FW). Germination was significantly affected by the type of endocarp treatment (acid scarification, 23%; removal of the endocarp, 46%), and by temperature (62% at 10/5°C and 15/10°C; 8% at 20/15°C and 4% 25/20°C), but not by concentration of GA3. Under the two best temperature regimes, only acid scarified stones were significantly affected by the stratification regime, with the highest germination (ca. 60%) after 60 days cold or 30 days warm followed by 30 days cold stratification regimes, although always lower than those obtained for seeds (> 80%). Epicotyl development required low temperature and three months to cotyledon leaf expansion. Germination requirements and embryo characteristics suggest a non-deep simple epicotyl morphophysiological dormancy including the occurrence of a possible chemical inhibition mechanism. For P. azorica propagation we recommend using naked seeds incubated at a temperature of 10/5 or 15/10°C.

A Definitive Book on Seed Ecology@@@Seeds: Ecology, Biogeography, and Evolution of Dormancy and Germination

Abstract: Introduction. Ecologically Meaningful Germination Studies. Types of Seed Dormancy. Germination Ecology of Seeds with Nondeep Physiological Dormancy. Germination Ecology of Seeds with Morphophysiological Dormancy. Germination Ecology of Seeds with Physical Dormancy. Germination Ecology of Seeds in the Persistent Seed Bank. Causes of Within-Species Variations in Seed Dormancy and Germination Characteristics. A Geographical Perspective on Germination Ecology: Tropical and Subtropical Zones. A Geographical Perspective on Germination Ecology: Temperate and Arctic Zones. Germination Ecology of Plants with Specialized Life Cycles and/or Habitats. Biogeographical and Evolutionary Aspects of Seed Dormancy. Subject Index.

Recent progress and challenges in population genetics of polyploid organisms: an overview of current state-of-the-art molecular and statistical tools.

Abstract: Despite the importance of polyploidy and the increasing availability of new genomic data, there remain important gaps in our knowledge of polyploid population genetics. These gaps arise from the complex nature of polyploid data (e.g. multiple alleles and loci, mixed inheritance patterns, association between ploidy and mating system variation). Furthermore, many of the standard tools for population genetics that have been developed for diploids are often not feasible for polyploids. This review aims to provide an overview of the state-of-the-art in polyploid population genetics and to identify the main areas where further development of molecular techniques and statistical theory is required. We review commonly used molecular tools (amplified fragment length polymorphism, microsatellites, Sanger sequencing, next-generation sequencing and derived technologies) and their challenges associated with their use in polyploid populations: that is, allele dosage determination, null alleles, difficulty of distinguishing orthologues from paralogues and copy number variation. In addition, we review the approaches that have been used for population genetic analysis in polyploids and their specific problems. These problems are in most cases directly associated with dosage uncertainty and the problem of inferring allele frequencies and assumptions regarding inheritance. This leads us to conclude that for advancing the field of polyploid population genetics, most priority should be given to development of new molecular approaches that allow efficient dosage determination, and to further development of analytical approaches to circumvent dosage uncertainty and to accommodate ‘flexible’ modes of inheritance. In addition, there is a need for more simulation-based studies that test what kinds of biases could result from both existing and novel approaches.

Do island plant populations really have lower genetic variation than mainland populations? Effects of selection and distribution range on genetic diversity estimates

Abstract: Ecological and evolutionary studies largely assume that island populations display low levels of neutral genetic variation. However, this notion has only been formally tested in a few cases involving plant taxa, and the confounding effect of selection on genetic diversity (GD) estimates based on putatively neutral markers has typically been overlooked. Here, we generated nuclear microsatellite and plastid DNA sequence data in Periploca laevigata, a plant taxon with an island–mainland distribution area, to (i) investigate whether selection affects GD estimates of populations across contrasting habitats; and (ii) test the long-standing idea that island populations have lower GD than their mainland counterparts. Plastid data showed that colonization of the Canary Islands promoted strong lineage divergence within P. laevigata, which was accompanied by selective sweeps at several nuclear microsatellite loci. Inclusion of loci affected by strong divergent selection produced a significant downward bias in the GD estimates of the mainland lineage, but such underestimates were substantial (>14%) only when more than one loci under selection were included in the computations. When loci affected by selection were removed, we did not find evidence that insular Periploca populations have less GD than their mainland counterparts. The analysis of data obtained from a comprehensive literature survey reinforced this result, as overall comparisons of GD estimates between island and mainland populations were not significant across plant taxa (N = 66), with the only exception of island endemics with narrow distributions. This study suggests that identification and removal of markers potentially affected by selection should be routinely implemented in estimates of GD, particularly if different lineages are compared. Furthermore, it provides compelling evidence that the expectation of low GD cannot be generalized to island plant popula

Genetic Diversity and Differentiation of Juniperus thurifera in Spain and Morocco as Determined by SSR

Abstract: Juniperus thurifera L. is an important tree endemic to the western Mediterranean basin that it is able to grow in semi-arid climates. It nowadays exhibits a disjunct distribution pattern, occurring in North Africa, Spain, France and the Italian Alps. The Strait of Gibraltar has acted as an efficient barrier against gene flow between African and European populations, which are considered different subspecies by some authors. We aimed at describing the intraspecific genetic diversity of J. thurifera in populations from the Iberian Peninsula and Morocco and the phylogeographical relationships among these populations. The ploidy level of J. thurifera was examined and eleven nuclear microsatellites (nSSRs) developed for J. thurifera were assessed for genotyping this species. Six nSSRs were polymorphic and subsequently used to assess the genetic diversity and structure of the studied populations. Genotyping of the tetraploid J. thurifera using nuclear microsatellites supports the separation of Moroccan and Spanish populations into two genetically differentiated groups that correspond to the proposed subspecies africana and thurifera. High values of within population genetic diversity were found, that accounted for 90% of the total genetic variance, while population structure was weak. The estimators of genetic diversity were higher in populations of Spain than in populations of Morocco pointing for a possible loss of genetic diversity during the spread of this species to Africa from Europe.