Isolation of seven polymorphic microsatellite loci,using an enrichment protocol,in the high Andean Asteraceous Chaetanthera pusilla

We report the development of seven microsatellite markers in the high Andean Asteraceae Chaetanthera pusilla. An enrichment protocol was used to isolate microsatellite loci, and polymorphism was explored with samples from two natural populations collected in the high Andes at La Parva and Valle Nevado (Chile). We found a high level of polymorphism, heterozygote deficiency and strong differentiation among populations. Four of the seven loci successfully cross‐amplified in other Chaetanthera species.     

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

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.     

Diet of Montagu's Harrier Circus pygargus in central Spain: analysis of temporal and geographic variation

The diet of Montagu's Harrier Circus pygargus was studied for 4 years near Madrid, Spain, with the use of pellets and prey remains collected during the breeding season. The diet of the study birds included a wide variety of prey categories, the most important one by weight being lagomorphs (mainly Hares Lepus granatensis ). The diet varied seasonally, with Hares predominating early in the breeding season, while birds increased in importance later. The shift was partly a result of variation in availability (with fledgling birds being more abundant late in the season), but statistical analysis suggested that lagomorphs and then birds were actively chosen in the prelaying and nestling periods, respectively. Montagu's Harrier seemed to be an opportunistic species, hunting a wider range of prey types in more southern latitudes, but specialized in each region in the prey species that was most profitable. This was the only study on Montagu's Harriers to date which found lagomorphs to be the most important part of the diet throughout the season.     

Phylogeny and evolution of Perezia （Asteraceae： Mutisieae： Nassauviinae）

A molecular phylogenetic analysis of most of the species of Perezia reveals that, as traditionally defined, the genus is not monophyletic with two species more closely related to Nassauvia than to Perezia. In addition, our results show that Burkartia （Perezia） lanigera is related to Acourtia and is the only member of that clade in South America. The remaining species are monophyletic and show a pattern of an early split between a western temperate and an eastern subtropical clade of species. Within the western clade, the phylogeny indicates a pattern of diversification that proceeded from southern, comparatively low-elevation habitats to southern high-elevation habitats, and ultimately into more northern high-elevation habitats. The most derived clades are found in the high central Andes, where significant radiation has occurred.     

Pollinator shifts and the loss of style polymorphism in Narcissus papyraceus (Amaryllidaceae)

Darwin proposed that the driving force for the evolution of style polymorphisms is the promotion of cross‐pollination between style morphs, through accurate placement of pollen on the pollinator’s body. This hypothesis has received much attention, but the effect of different pollinators in the fitness of morphs remains poorly understood. Narcissus papyraceus is a style dimorphic species (long ‐L‐ and short ‐S‐ styled) with isoplethic (1 : 1) and L‐monomorphic populations, mainly visited by long‐tongued (LT) nocturnal and short‐tongued (ST) diurnal pollinators, respectively. We studied natural female fertility of morphs, and assessed the role of diurnal and nocturnal pollinators. We also quantified female fertility of the morphs in experimental populations with different morph ratio, exposed to predominately long‐ or short‐tongued pollinators. We found that with LT pollinators, both morphs were successfully pollinated in all morph ratio conditions, suggesting that these insects could be involved in maintenance of the polymorphism, although other factors may also play a role. However, with ST pollinators, S‐plants displayed less fertility than L‐plants, and mating among L‐plants was favoured, implying that the polymorphism is lost. These results underscore the role of pollinators on variations in style polymorphism.     

The effects of rootstock and scion on tobacco mosaic virus infection in susceptible, tolerant and immune cultivars of tomato

Reciprocal grafts were made between tomato cultivars Potentate, susceptible, and Virocross, tolerant (heterozygous for resistance gene Tm-i) to tobacco mosaic virus (TMV) isolates of Pelham type o and between isogenic lines of cv. Craigella, susceptible and homozygous for gene Tm-i. The grafted plants were inoculated with a type o isolate; both scion and stock inoculation were studied in the former, scion inoculation only, in the latter. With scion inoculation the virus content of a tolerant scion was greater on a susceptible stock than on a tolerant one, but that of a susceptible scion was unaffected by the type of stock: in contrast, the virus content of a tolerant stock was unaffected by the type of scion but that of a susceptible stock was less with a tolerant than with a susceptible scion. With root inoculation the virus contents of both tolerant and susceptible scions were greater on a susceptible than on a tolerant stock. With cv. Craigella the genotype Tm-1/Tm-1 was found to be immune to the type o isolate used, but in grafts the leaves of Tm-1/Tm-1 scions became tolerant to leaf inoculation when on susceptible stocks and the virus entered the stock. Tm-1/Tm-1 stocks became infected when attached to infected, susceptible scions and did not affect the virus content of those scions. The results indicate that a susceptible healthy stock may change the reaction of a tolerant or immune scion to infection by a strain of TMV.     

The regional variation of aboveground live biomass in old-growth Amazonian forests

The biomass of tropical forests plays an important role in the global carbon cycle, both as a dynamic reservoir of carbon, and as a source of carbon dioxide to the atmosphere in areas undergoing deforestation. However, the absolute magnitude and environmental determinants of tropical forest biomass are still poorly understood. Here, we present a new synthesis and interpolation of the basal area and aboveground live biomass of old‐growth lowland tropical forests across South America, based on data from 227 forest plots, many previously unpublished. Forest biomass was analyzed in terms of two uncorrelated factors: basal area and mean wood density. Basal area is strongly affected by local landscape factors, but is relatively invariant at regional scale in moist tropical forests, and declines significantly at the dry periphery of the forest zone. Mean wood density is inversely correlated with forest dynamics, being lower in the dynamic forests of western Amazonia and high in the slow‐growing forests of eastern Amazonia. The combination of these two factors results in biomass being highest in the moderately seasonal, slow growing forests of central Amazonia and the Guyanas (up to 350 Mg dry weight ha^?1) and declining to 200–250 Mg dry weight ha^?1 at the western, southern and eastern margins. Overall, we estimate the total aboveground live biomass of intact Amazonian rainforests (area 5.76 × 10⁶ km² in 2000) to be 93±23 Pg C, taking into account lianas and small trees. Including dead biomass and belowground biomass would increase this value by approximately 10% and 21%, respectively, but the spatial variation of these additional terms still needs to be quantified.