Lavandula latifolia



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Lavandula latifolia is an evergreen shrub occurring in the eastern Iberian Peninsula and southern France. In the Sierra de Cazorla the species typically occupies well-insolated habitats at mid elevations, such as the understory of open pine or oak forests, forest clearings and edges, and successional scrub. Individual plants live for up to 25-35 yr. Local populations may persist for many generations on permanently favorable places like open forests and sparse scrublands on rocky outcrops or poor soils. Other habitats, like natural forest clearings on more humid locations with fertile soils, may remain favorable for the species for only a few generations. At these sites, L. latifolia populations decline to local extinction in a few decades after colonization, as succession proceeds and a developing forest canopy reduces insolation.

Population size and abundance, and within-population genetic diversity, vary predictably with altitude, being highest at middle elevations and declining steadily towards both the upper and lower altitudinal distribution margins. Genetic differentiation tended to follow the opposite trend. These altitudinal patterns result from variation with elevation in the relative influence of gene flow and drift on the distribution of genetic variation. Genetic drift prevails around the upper and lower altitudinal limits, while a situation closer to a drift-gene flow equilibrium exists at the centre of the altitudinal distribution (click here for further details on patterns of genetic variation in this species).

Flowers are hermaphroditic, protandrous, have pale-blue tubular corollas (tube length 7-8 mm), and are produced over a short (3-6 cm) terminal portion of the stalks in a dichasium-like arrangement. Flowers are self-compatible, but spontaneous autogamy occurs very infrequently due to protandry and, principally, to the spatial separation of anthers and stigma. In the absence of pollinators, < 4% of flowers set fruit. Outcross pollination results in greater proportion of flowers setting fruit, and greater proportion of ovules yielding seeds per fruit, relative to self-pollination. Flowers have four ovules, each potentially producing an independent nutlet.

In the study region, L. latifolia is pollinated by a diverse array of bee, fly, and butterfly species (click here or here for details), which differ widely in their pollinating efficiency (click here). Flowers exposed to pollination regimes differing in pollinator composition have been shown experimentally to differ in their contribution to population recruitment in the field, as measured in terms of established seedlings (see here). Seeds lack special dispersal mechanisms, falling beneath or very close to the parent plant shortly after maturation, although large herbivorous mammals might occasionally disperse seeds at long distances. Seeds are short-lived, becoming inviable after 2-3 yr in the soil, hence the establishment of new populations will generally depend on seed colonization rather than regeneration from a pre-existing soil seed bank.

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