518 research outputs found

    Genetic diversity of Tamarindus indica populations: Any clues on the origin from its current distribution?

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    Tamarindus indica is a domesticated species of high economic value for the Sahel region. Despite this importance, very few data is available on its diversity as well as its structure leading to controversialdiscussions on its origin. Thus it is questionable whether the knowledge of its genetic diversity and organisation may help in identifying the area of its origin. We have studied 10 populations using markers RAPDs with the seeds collected from Asia (India and Thailand), Africa (Burkina Faso, Senegal, Kenya and Tanzania), from three islands (Madagascar, Réunion and Guadeloupe). The results showed that T. indica has a high intra population genetic variability with a higher value obtained in the population from Cameroon. This high intra-population variability did not allow us to determinate the origin of the species. However, if we take into account the paleontological and anthropological results, we can assume that T. indica has an African origin

    Breeding system and pollination biology of the semidomesticated fruit tree, Tamarindus indica L. (Leguminosae: Caesalpinioideae): Implications for fruit production, selective breeding, and conservation of genetic resources

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    In this paper, we provide data on the breeding system of Tamarindus indica, examining fruit production as well as pollen tube growth under different controlled pollination experiments (open, cross and selfpollination). We discuss implications of the results for management for fruit production in Tamarind, conservation of genetic resources and the potential for selective breeding. Observation of the germination and the pollen tubes growth under various pollination modes show that the tamarind is an incompatible species partially. This incompatibility appears at the pre level zygotic (IE on the level of the stigmatic, style and ovary) and post zygotic by the abortion of seeds

    The probing behaviour of nymphs of Vanduzeea arquata and Enchenopa binotata (Homoptera: Membracidae) on host and non-host plants

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    1. Nymphs of Vanduzeea arquata Say have been found to be more host-specific in nature and to show a higher degree of selectivity in host discrimination experiments than nymphs of Enchenopa binotata (Say), It was hypothesized that this differential selectivity would be reflected in the probing behaviour of individuals placed on twigs of host and non-host plants. Probing behaviour was examined by direct observation of nymphs and by sectioning and staining the probed plant tissues. 2. All nymphs probed readily and for extended periods on both host and non-host twigs. E.binotuta nymphs showed no consistent differences in probing behaviour on hosts versus non-hosts, but V.atquuta nymphs were more likely to withdraw their stylets within 60 s when on non-host twigs and produced honeydew only when on their host species. V.urquatu nymphs reached the phloem sieve elements only when on host twigs and broke many cells in peripheral plant tissue layers while probing. E.binotata nymphs broke few cells and often reached the phloem of non-host as well as host plants. 3. Nymphs of V.arquata always reject non-host plants, apparently in the course of probing and prior to encountering the phloem sap. Chemical compounds released from ruptured parenchyma cells may act as probing stimulants or inhibitors. E.binotura nymphs often feed on non-host plants in a non-choice situation; their preferential settling on host twigs in discrimination experiments may reflect a tendency to abandon non-host twigs more readily than host twigs.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72791/1/j.1365-2311.1984.tb00840.x.pd

    Inherited biotic protection in a Neotropical pioneer plant

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    Chelonanthus alatus is a bat-pollinated, pioneer Gentianaceae that clusters in patches where still-standing, dried-out stems are interspersed among live individuals. Flowers bear circum-floral nectaries (CFNs) that are attractive to ants, and seed dispersal is both barochorous and anemochorous. Although, in this study, live individuals never sheltered ant colonies, dried-out hollow stems - that can remain standing for 2 years - did. Workers from species nesting in dried-out stems as well as from ground-nesting species exploited the CFNs of live C. alatus individuals in the same patches during the daytime, but were absent at night (when bat pollination occurs) on 60.5% of the plants. By visiting the CFNs, the ants indirectly protect the flowers - but not the plant foliage - from herbivorous insects. We show that this protection is provided mostly by species nesting in dried-out stems, predominantly Pseudomyrmex gracilis. That dried-out stems remain standing for years and are regularly replaced results in an opportunistic, but stable association where colonies are sheltered by one generation of dead C. alatus while the live individuals nearby, belonging to the next generation, provide them with nectar; in turn, the ants protect their flowers from herbivores. We suggest that the investment in wood by C. alatus individuals permitting stillstanding, dried-out stems to shelter ant colonies constitutes an extended phenotype because foraging workers protect the flowers of live individuals in the same patch. Also, through this process these dried-out stems indirectly favor the reproduction (and so the fitness) of the next generation including both their own offspring and that of their siblings, alladding up to a potential case of inclusive fitness in plants

    Macroevolution of defense syndromes in Ficus (Moraceae)

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    Recursive adaptations and counter‐adaptations of plant‐feeding insects are thought to have driven chemical and physical diversity in plant defenses. Among existing theories on defensive diversity, the syndromes hypothesis predicts that plants may evolve suites of covarying defense traits along evolutionary arms races with herbivores. We use the large, phenotypically diverse angiosperm genus Ficus (Moraceae) to test the major predictions of this hypothesis: i) plant species will form distinctive combinations of defensive traits; ii) these traits will be correlated within each syndrome. Trait combinations need not map well onto phylogenies because plant species can converge onto similar trait values, but strong phylogenetic signal driven by selection (as opposed to drift) suggests roles for escalation and co‐evolution. Finally, Ficus species with complementary combinations of defenses will be less susceptible to insect damage and harbor distinct insect communities. We quantified susceptibility to insect herbivory and nine leaf traits related to resource acquisition and defense in 36 Ficus species growing in a common‐garden setting, in dry and wet seasons over two years. We recovered a set of three syndromes defined by relatively small sets of trait combinations. Broadly speaking, these syndromes grouped fig species with different life forms. For example, epiphytic figs had nutrient‐poor, tough, tannin‐rich leaves, while free‐standing trees tended to have leaves covered in trichomes and full of alkaloid‐rich latex. When season and species identity were accounted for, the combination of two traits, higher C/N and higher latex tannin content, provided significantly stronger defense than did either trait taken singly. Several individual traits (C/N, latex tannin and trichome density) were significantly negatively correlated with herbivore damage, while alkaloid content was positively correlated (perhaps as a result of feeding by adapted herbivores). Several defensive traits influenced insect herbivore community structure. Finally, traits followed different evolutionary trajectories. While latex tannin, C/N and leaf tannin fit a Brownian‐motion model of evolution, the first two escalating across Ficus phylogeny, others appeared to have more limited phylogenetic signal or tended to de‐escalate. Overall, the patterns we detected support the concept of coordinated defense syndromes, demonstrating that evolutionary arms races can drive combinations of traits in this genus

    Range Expansion Drives Dispersal Evolution In An Equatorial Three-Species Symbiosis

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    A-09-14International audienceBackground Recurrent climatic oscillations have produced dramatic changes in species distributions. This process has been proposed to be a major evolutionary force, shaping many life history traits of species, and to govern global patterns of biodiversity at different scales. During range expansions selection may favor the evolution of higher dispersal, and symbiotic interactions may be affected. It has been argued that a weakness of climate fluctuation-driven range dynamics at equatorial latitudes has facilitated the persistence there of more specialized species and interactions. However, how much the biology and ecology of species is changed by range dynamics has seldom been investigated, particularly in equatorial regions. Methodology/Principal Findings We studied a three-species symbiosis endemic to coastal equatorial rainforests in Cameroon, where the impact of range dynamics is supposed to be limited, comprised of two species-specific obligate mutualists –an ant-plant and its protective ant– and a species-specific ant parasite of this mutualism. We combined analyses of within-species genetic diversity and of phenotypic variation in a transect at the southern range limit of this ant-plant system. All three species present congruent genetic signatures of recent gradual southward expansion, a result compatible with available regional paleoclimatic data. As predicted, this expansion has been accompanied by the evolution of more dispersive traits in the two ant species. In contrast, we detected no evidence of change in lifetime reproductive strategy in the tree, nor in its investment in food resources provided to its symbiotic ants. Conclusions/Significance Despite the decreasing investment in protective workers and the increasing investment in dispersing females by both the mutualistic and the parasitic ant species, there was no evidence of destabilization of the symbiosis at the colonization front. To our knowledge, we provide here the first evidence at equatorial latitudes that biological traits associated with dispersal are affected by the range expansion dynamics of a set of interacting species
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