Montserrat Arista

Genetic diversity and population structure in natural populations of moroccan atlas cedar (Cedrus Atlantica; Pinaceae) determined with cpSSR markers

Atlas cedar (Cedrus atlantica) is an ecologically and economically important forest tree species of northern Africa and is considered one of the endangered conifer species in the region. Chloroplast microsatellites (cpSSR) were used to study genetic variation within and among populations and geographical structure in natural populations of C. atlantica throughout its entire distribution range in Morocco. A total of 25 chloroplast haplotypes and 66 cpSSR alleles were found among 162 individuals. The cpSSRs indicate that C. atlantica appears to maintain a high level of genetic diversity (mean H(e) = 0.95), as observed in most coniferous species. Values of mean pairwise distance within a population (D(2)(SH)) were related to the size and location of the populations. AMOVA analysis showed that most of the variation in C. atlantica occurs within populations and confirmed the general tendency of gymnosperms to display lower values of population differentiation than angiosperms. The distance-based clustering method (PCoA and neighbor-joining analysis) and the geographical structure revealed a poor structure among the six populations of Cedrus atlantica. Also, a Mantel test indicated a weak correlation between geographic and genetic distances (P = 0.106, r = 0.363). These results are also interpreted in the context of postglacial history of the region plus human impacts.

LOW REPRODUCTIVE SUCCESS IN TWO SUBSPECIES OF JUNIPERUS OXYCEDRUS L.

Mature seed cone and seed production were studied in six populations of Juniperus oxycedrus (three of subspecies oxycedrus and three of subspecies macrocarpa). In both subspecies, seed cone abortion took place mainly just after the pollination period, and most of the remaining seed cones reached full size. Percentage of mature cones was significantly higher in subspecies oxycedrus than in macrocarpa. In both taxa, seed cones developed fully in the absence of filled seeds. Both the number of full-sized seeds per cone and the seed viability were low, and they were similar in both subspecies. However, seed potential was markedly higher in subsp. macrocarpa (mean 4.1 ovules/cone) than in subspecies oxycedrus (mean 2.8 ovules/cone), indicating a lower seed efficiency in subspecies macrocarpa. Results indicate that deficient pollination and site quality can be causes of low seed cone production and low seed viability in both subspecies of J. oxycedrus.

Abiotic factors may explain the geographical distribution of flower colour morphs and the maintenance of colour polymorphism in the scarlet pimpernel

Summary1. Flower colour polymorphism is traditionally attributed to pollinator selection although otherfactors, such as indirect selection on correlated traits, can play an important role.2. Lysimachia arvensis is a widespread annual species with two colour morphs differing in anthocy-anin composition. We explored the hypothesis that colour polymorphism is maintained by selectionrelated to environmental heterogeneity. Morph frequencies and environmental traits were recorded in51 populations along a wide geographical range. To explore the existence of morph-by-environmentinteractions, we conducted an experimental study comparing the two morphs under treatments differ-ing in water and light availability.3. A geographical pattern was found with a negative association between blue frequencies and lati-tude. The proportion of the blue morph increased with temperature and sunshine hours, butdecreased with precipitation. Flowering onset and flower size differed between morphs and scarcelyvaried across treatments. In contrast, several fitness components such as germination, seedlingsurvival, seedling mass and flower production showed important morph-by-environment interactions.The blue morph showed higher overall male and female fitness in all the treatment combinationsexcepting in sun-wet conditions where the red morph had higher fitness.4. Synthesis. Our results indicate that the mechanism of selection on flower colour seems to berelated to differences in fitness of both morphs due to abiotic factors. These differences couldexplain the geographical distribution of flower colour morphs and the maintenance of the colourpolymorphism. The marked difference in flowering time between morphs leaves open the potentialfor assortative mating and speciation in Lysimachia arvensis.Key-words: Anagallis, anthocyanins, clinal variation, flower phenology, morph-by-environmentinteraction, pleiotropy, reproductive ecology, selectionIntroduction

Explosive seed dispersal in two perennial Mediterranean Euphorbia species (Euphorbiaceae)

The distance of explosive dispersal, its pattern in time, and the relative importance of autochory have been studied in two diplochorous species: Euphorbia boetica and E. nicaeensis. The seeds of E. boetica released by explosive dispersal reached a median distance of 156 cm and a maximum of almost 8 m, while the distances reached by the seeds of E. nicaeensis were lower: a median of 132 cm and a maximum of 5 m. The differences in explosive dispersal distance between species seem to depend on both seed mass and caruncle retention. The seeds of both species present a caruncle, but in E. boetica this is tiny, and in most cases is shed during the explosion of the capsules. The distances reached by the seeds of these species, dispersed just by capsule explosion, were similar to or greater than the distances to which ants disperse seeds in the Mediterranean sclerophyllous vegetation. Diplochorous plants may maximize either the distance of primary dispersal or that of secondary dispersal. Given that the seeds of E. boetica, that lose their caruncles, are not gathered by myrmecochorous ants, the results suggest that E. boetica maximizes its primary dispersal distance, whereas E. nicaeensis favors its secondary dispersal.

POLLINATOR ATTENDANCE AND REPRODUCTIVE SUCCESS IN CISTUS LIBANOTIS L. (CISTACEAE)

We studied pollen flow and reproductive success in two different‐density stands of Cistus libanotis, a self‐incompatible species. The pollinator spectrum comprised Hymenoptera, Coleoptera, and Diptera, but their relative frequencies at the flowers differed between stands. The pollen loads carried by insect visitors were from a considerable number of plant species (up to 11 species) apart from C. libanotis. Hymenoptera showed the highest activity rate and the highest flower visitation rate and carried by far the highest number of both total pollen grains and C. libanotis pollen grains. These factors indicate that Hymenoptera are the most effective pollinators and the major contributors to C. libanotis reproductive success. Nevertheless, considering the insect species, a dipteran, the syrphid Eristalis tenax appears to be more effective than some Hymenoptera on the basis of its C. libanotis–pollen carrying ability. Fluorescent dust dispersal indicated that the neighborhood area for pollen dispersal was different among stands and could change during the flowering season. Considering the reproductive output over the flowering season, differences in pollinator spectrum and in pollen flow among stands did not affect the reproductive success of C. libanotis individuals; both fruit and seed set were similar among stands.

A multi-year study of factors affecting fruit production in Aristolochia paucinervis (Aristolochiaceae)

Pollen limitation, resource limitation, fruit abortion, and predation have all been proposed as factors explaining low fruit set in hermaphroditic plants. We conducted a 5-year study combining field observations and pollination experiments to determine the causes of the low fruit set in Aristolochia paucinervis, a Mediterranean species with a specialized pollination system in two populations in SW Spain. Fruit initiation was markedly low, and between 28.6 and 75.0% of the flowering stems did not initiate any fruit. In most flowers, the number of germinated pollen grains was less than the number of ovules, and supplemental pollination significantly increased fruiting, indicating deficient pollination. In A. paucinervis, autonomous self-pollination seems to be a decisive factor in fruit production because the number of germinated pollen and the fruit set from flowers bagged before anthesis were similar to those in free-pollinated flowers. Only in 2005 did flowers that were successfully pollinated outnumber ripened fruits, suggesting that other factors limit fruiting. We found a significant positive correlation between tuber mass and fruit set. Deficient pollination and lack of resources could explain the low fruit set, but the relative consequences seem to vary spatially and temporarily.

Apical pattern of fruit production in the racemes of Ceratonia siliqua (Leguminosae: Caesalpinioideae): role of pollinators.

Fruit production and arrangement within the raceme were studied in two dioecious populations of Ceratonia siliqua (Leguminosae: Caesalpinioideae), an arboreal species that produces caulogenous racemes (emerging only from the old branches) with numerous flowers. Fruit production per raceme was low and similar between years and populations and even between individuals. During flowering, there were considerable flower losses from predation and lack of pollination. A mean of nine flowers per raceme began the transformation into fruits, of which 77% aborted. The final fruit production per raceme increased significantly following hand pollination, but was always very much lower than the availability of flowers in the raceme. The results suggest that fruit production of each raceme is limited by both availability of resources and a deficient pollination. In racemes setting fruit arrangement follows a definite pattern that remains constant between years and populations: fruit production was significantly higher in the apical zone of the raceme and lower in the basal zone. The pollinators of C. siliqua (flies and wasps) showed a clear preference for beginning their visits at the apex of a raceme. As a result, the pollen load deposited on the stigmas decreased from apex to base of the raceme. In most of the flowers situated in the central and basal zone of the raceme, the number of pollen grains deposited on their stigmas was lower than the number of their ovules. The high number of seeds in developed fruits suggests that the plant selectively aborts flowers that receive a smaller pollen load. The results indicate that the final pattern of fruit arrangement within the raceme is a direct result of pollinator activity.

The structure and dynamics of an Abies pinsapo forest in southern Spain

Abstract The forest composition and age-diameter relationships of Abies pinsapo were studied in a natural forest in the Nature Reserve of the Sierra de Grazalema (southern Spain). The composition and structure of the forest was very different with respect to gaps and closed forest. Altitudinal differences in forest composition were also found. Abies pinsapo was the dominant species, Quercus rotundifolia and Quercus faginea were the other important overstorey species. The diameter distributions of A. pinsapo were skewed toward the larger size classes, with a large seedling proportion of about 70%. Abies pinsapo establishment rates were higher in the gaps. Seedlings of Abies pinsapo established under the closed canopy forest had suppressed growth, as indicated by their relatively advanced ages. Seedlings and saplings with suppressed growth can survive for a mean of 40 years, constituting a pool from which canopy trees may be recruited. Results show that the pinsapo forest of the Sierra de Grazalema is in equilibrium and that its dynamics are conditioned by a small-sapling bank and canopy gap formation.

Endozoochory by beetles: a novel seed dispersal mechanism

BACKGROUND AND AIMS Due in part to biophysical sized-related constraints, insects unlike vertebrates are seldom expected to act as primary seed dispersers via ingestion of fruits and seeds (endozoochory). The Mediterranean parasitic plant Cytinus hypocistis, however, possesses some characteristics that may facilitate endozoochory by beetles. By combining a long-term field study with experimental manipulation, we tested whether C. hypocistis seeds are endozoochorously dispersed by beetles. METHODS Field studies were carried out over 4 years on six populations in southern Spain. We recorded the rate of natural fruit consumption by beetles, the extent of beetle movement, beetle behaviour and the relative importance of C. hypocistis fruits in beetle diet. KEY RESULTS The tenebrionid beetle Pimelia costata was an important disperser of C. hypocistis seeds, consuming up to 17·5 % of fruits per population. Forty-six per cent of beetles captured in the field consumed C. hypocistis fruits, with up to 31 seeds found in individual beetle frass. An assessment of seeds following passage through the gut of beetles indicated that seeds remained intact and viable and that the proportion of viable seeds from beetle frass was not significantly different from that of seeds collected directly from fruits. CONCLUSIONS A novel plant-animal interaction is revealed; endozoochory by beetles may facilitate the dispersal of viable seeds after passage through the gut away from the parent plant to potentially favourable underground sites offering a high probability of germination and establishment success. Such an ecological role has until now been attributed only to vertebrates. Future studies should consider more widely the putative role of fruit and seed ingestion by invertebrates as a dispersal mechanism, particularly for those plant species that possess small seeds.

Genetic races associated with the genera and sections of host species in the holoparasitic plant Cytinus (Cytinaceae) in the Western Mediterranean basin

* Speciation via race formation is an important evolutionary process in parasites, producing changes that favour their development on particular host species. Here, the holoparasitic plant Cytinus, which has diverse host species in the family Cistaceae, has been used to study the occurrence of such races. * Amplified fragment length polymorphism (AFLP) analyses were performed on 174 individuals of 22 populations parasitizing 10 Cistaceae species in the Western Mediterranean basin. * Neighbour-joining, multivariate ordination analyses, and individual-based Bayesian analyses, clustered Cytinus populations into five well-characterized genetic races that, overall, agreed with the taxonomic sections of their hosts. In the AMOVA, among-races differences accounted for almost 50% of the genetic variation. The isolation-by-distance model was not supported by a Mantel test among Cytinus populations (r = 0.012; P = 0.456). All races showed low within-population genetic diversity, probably as a result of restricted pollen flow aggravated by flowering asynchrony, restricted seed dispersion, or stochastic processes. * The genetic differentiation among the five races of Cytinus is congruent with the view that these races are well-characterized lineages that have evolved independently as a result of selective pressures imposed by their hosts. This pattern, with genetically distinctive groups associated with the infrageneric sections of the host species, has not been reported previously for parasitic angiosperms.