Reproductive ecology of Rhododendron ponticum (Ericaceae) in relict Mediterranean populations

Abstract

In the southern Iberian Peninsula, Rhododendron ponticum occurs in restricted and vulnerable populations as a Tertiary relict. Population structure and the main phases of the reproductive process were examined in order to shed light on recruitment patterns and limitations. Rhododendron ponticum flowers are self‐compatible and attract a diverse array of insects, which are responsible for a considerable number of seeds set in the populations. Nevertheless, only adults form populations, whilst seedlings are scarce and saplings virtually absent (only two juveniles out of 2489 adults sampled). Non‐specialized vegetative multiplication by layering was observed. Recruitment failure seems to depend on the scarcity of safe microsites, which are free from drought, for seedling establishment. The observations contrast with R. ponticum's reputation as an aggressive invader in temperate Atlantic areas. It is proposed that the species shows a variable balance between sexual reproduction and vegetative multiplication depending on environmental conditions. At present, only the latter seems to be prevailing in relict populations in the Iberian Peninsula. This flexible reproductive strategy is also discussed as a mechanism allowing persistence during geological climatic oscillations. © The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 140, 297–311.

The use of in vitro culture to improve the propagation of Rhododendron ponticum subsp. baeticum (Boiss. & Reuter)

“…Similar results were reported by F. Besnier-Romero [19]. Also, Mejías et al [4] observed virtually no germination when seeds were buried in situ.…”

“…baeticum survive mainly on riverbanks running through steep terrain, with shadow-rainy environment, or in the mountains with frequent fogs. These populations, although locally abundant, are formed mainly by adult plants showing low or no effective recruitment, and a lack of young plants [4]. The populations persist probably because it has been observed that lower branches of adult plants produce new ramets by layering.…”

Comparison of fine-scale spatial genetic structure of two sympatricRhododendronshrub species in forest habitat having different seed weights: A case study

“…In addition, the two Rhododendron species depend on insect pollination. At our study site, bumblebee species are the pollinators for flowers of the two Rhododendron species, which is consistent with the findings of previous studies suggesting that the main pollinators for R. semibarbatum are bumblebee species (Ono et al, 2008) and bumblebee species are common pollinators for Rhododendron species (Kudo, 1993;Ng and Corlett, 2000;Mejías et al, 2002). Therefore, we might exclude the possibility that pollen limitation and difference in pollinator species could explain the differences in the intensity of SGS between the two Rhododendron species.…”

“…Rhododendron species are reported to commonly exhibit clonal structure through layering (Escaravage et al, 1998;Naito et al, 1999;Mejías et al, 2002;Elliott and Vose, 2012). To remove the effect of clonal structure on the SGS, SGS should be analyzed for one stem from each clone (multi-locus lineage; MLLs) based on clonal identification.…”

Historical connectivity, contemporary isolation and local adaptation in a widespread but discontinuously distributed species endemic to Taiwan, Rhododendron oldhamii (Ericaceae)

“…Recent intensive field studies of populations showed that northern populations flower during the spring, whereas southern populations flower heterogeneously at different times of the year (Chi, 2009). Flowering time differences between populations have also been reported in other Rhododendron species (Kudo, 1993;Kameyama et al, 2001;Mejías et al, 2002). The occurrence of reproductive isolation or reproductive incompatibility is related to assortative mating, because immigrants that flower at different times from those of local individuals cannot reproduce, and as a consequence no gene flow occurs (Gavrilets and Vose, 2007).…”