Herbivorous mammals as seed dispersers in a Mediterranean dehesa

Endozoochrous seed dispersal by herbivorous mammals has been verified repeatedly and its possible influence on the structure and function of herbaceous communities has been suggested. Quantitative studies, however, are lacking in the field of seed dispersal via the dung of herbivore guilds in little-altered environments. The present paper analyses seed dispersal via rabbit, fallow deer, red deer and cow dung in a Mediterranean dehesa (open woodland used for hunting and ranching) during the seeding season. Dung seed content was determined by the glasshouse cultivation of eight dung samples from each herbivore, collected fortnightly between February and August. The four herbivores disperse many seeds (spring averages are 6–15 seeds per gram of dry dung and maxima of 25–70) from a large number of species (totals between 52 and 78). Dispersal seems to be mainly determined by seed production of the plant comminity. This is reflected in (i) the dissemination of a high percentage of the species present in the dehesa, (ii) great seasonal variability, related to seed production, in the amount of seeds and number of species dispersed, and (iii) a high semi-quantitative similarity of seed content in the four types of herbivore dung throughout the year. There is also important quantitative variation that depends on animal traits and feeding habits. These results and the characteristics of species found in dung suggest the adaptation of plant species to the dispersal of their seeds via herbivore gut. This process may well have profound implications for vegetation dynamics and the evolution of plant traits.     

Types of pollination and seed dispersal in Mediterranean plants

Abstract

Selected examples of pollen and seed dispersal in Mediterranean plants are described. The aspects of pollination considered are: comparison between cleistogamous and chasmogamous forms in the same species; differences in attractants and rewards; duration of pollen viability according to pollination syndrome. The aspects of seed dispersal considered are: presence or absence of specialized structures for dispersal; examples of active, passive and induced dispersal; animals involved in seed dispersal and their reward; type and functions of elaiosomes.     

The mycorrhizal status of the woody Mediterranean shrub Myrtus communis L.

  Myrtus communis L. (myrtle), a typical Mediterranean plant species belonging to the family Myrtaceae, was shown to form arbuscular mycorrhizal symbioses in nature. Many different spore types were isolated from its rhizosphere and grown in pot cultures; six of them were identified as Glomus species. In the laboratory, the myrtle root system was colonized by indigenous endophytes as well as by an Italian isolate of Glomus intraradices. In greenhouse experiments, mycorrhizal inoculation reduced transplant stress in 60-day-old myrtle seedlings; their growth was renewed immediately after transplanting, whereas non-mycorrhizal plants stopped development. Significantly larger growth responses were obtained using indigenous fungi than the Italian isolate of Glomus intraradices. Accepted: 16 January 1997     

Somatic embryogenesis and plant regeneration in myrtle (Myrtaceae)

Somatic embryos of myrtle (Myrtus communis L.) were induced from mature zygotic embryos cultured in MS medium supplemented with several concentrations of 2,4-D (2.26 μM – 18.98 μM) or Picloram (2.07 μM – 16.5 μM) combined with 0.087 M or 0.23 M sucrose. For all the concentrations of 2,4-D or Picloram tested, 0.087 M sucrose proved to be more effective than 0.23 M. The best frequencies of induction were obtained in a medium containing 2.26 μM 2,4-D in which 97.3% of the explants produced somatic embryos. Although most embryos were produced from the adaxial side of the cotyledons, some of them differentiated from the hypocotyl. Secondary somatic embryos were often seen arising from the periphery of the former somatic embryos. Somatic embryo development was not synchronous but practically all the embryos germinated well after being transferred to media containing GA₃ (0.29, 0.58 and 1.44 μM) alone. When benzyladenine was combined with gibberellic acid, germinating somatic embryos produced adventitious shoot buds which contributed to an increase in plantlet regeneration. Histological observations suggested that somatic embryos arise from the upper surface of the cotyledons probably from peripheral cells. Polyphenol-rich cells were usually seen in association with meristematic-like cells from which somatic embryos originate or with earlier steps of somatic embryo differentiation. Regenerated plants were phenotypically normal, showing a diploid (2n = 22) set of chromosomes. This revised version was published online in June 2006 with corrections to the Cover Date.     

The role of the brown-eared bulbulHypsypetes amaurotis as a seed dispersal agent

The role of the brown-eared bulbul,Hypsypetes amaurotis, as a dispersal agent for seeds of fruiting plants was studied by field observations for two years, in parallel with laboratory experiments on seed germination. Bulbuls consumed fruits of 53 species from 24 plant families. The fruits of these plants had similar color and size, and these characteristics were likely to enhance the feeding efficiency of the frugivore. Laboratory experiments on 20 food plant species demonstrated that: (1) no seeds were injured by passing through the bulbul's gut; (2) seeds that had passed through the bulbul's gut were still able to germinate and (3) fruit pulp reduced germination ability. When pulp was removed by passing through bulbul's gut, or by hand, germination was improved. An estimate of the home range of six bulbuls suggested that they may transport seeds for at least 300 m.     

Ancient introductions of mammals in the Mediterranean Basin and their implications for conservation

• 1 The importance of taxonomy to the determination of conservation priorities and actions is widely accepted. It should be not surprising therefore that the taxonomic treatment of mammal species that have been subject to human actions in antiquity may well influence the contemporary assessment of conservation priorities at various levels.
• 2 As a result of early extinctions caused by humans and protohistoric and historic introductions, we suggest that the Mediterranean Basin and its islands are particularly prone to misdirection of efforts towards biodiversity conservation.
• 3 The two main risks associated with the failure to use an evolutionary and palaeoecological approach to conservation efforts are (i) an underestimation of the conservation importance of distinctive continental taxa vs. the apparent endemicity of island taxa; and (ii) a serious risk for native and endemic island species when anthropochorous mammals, especially ungulates, misguidedly become the focus of conservation actions, particularly inside protected areas.
• 4 Urgent measures, including refinement of mammal taxonomy, the exclusion of known anthropochorous taxa from conservation lists and implementation of protective legislation, are necessary to maintain the uniqueness and richness of the Mediterranean biodiversity hotspot.

     

Comparative palynology and seed morphology in annual pansies (Viola sect. Melanium,Violaceae): implications for species delimitation

Abstract

This integrated study provides new insights into pollen and seed morphology and pollen heteromorphism of four closely related annual taxa of Viola sect. Melanium. The plant material, both fresh and dried, was collected in Italy and studied using light and scanning electron microscope. Palynological data for V. hymettia together with a detailed comparative analysis of seed morphology and micromorphology of the four species are reported for the first time. Results of this work highlight some pollen and seed features as useful diagnostic characters. The pollen size proves to be of diagnostic value to easily separate V. kitaibeliana, having the smallest pollen grains, from the others, especially from V. arvensis with the largest ones. Exine ornamentation is microreticulate, showing no relevant differences among species. We can partially confirm the diagnostic value of the prevailing pollen morph as it can be useful only for V. arvensis (five-aperturate) versus V. tricolor and V. hymettia (four-aperturate). The macro- and micromorphology of seeds provide additional useful distinguishing characters. Particularly, seed size was found to be a good delimitating character, especially to distinguish V. kitaibeliana (with the smallest seeds) from V. arvensis, and easy to be measured with no need of particular equipment.     

Critical phases in the seed development of common juniper (Juniperus communis)

Common juniper (Juniperus communis L.) populations in northwest European lowlands are currently declining in size and number. An important cause of this decline is a lack of natural regeneration. Low seed viability seems to be one of the main bottlenecks in this process. Previous research revealed a negative relation between seed viability and both temperature and nitrogen deposition. Additionally, the seeds of common juniper have a variable ripening time, which possibly influences seed viability. However, the underlying mechanisms remain unresolved. In order to elucidate this puzzle, it is important to understand in which phases of seed production the main defects are situated, together with the influence of ripening time. In this study, we compared seed viability of populations with and without successful recruitment. We examined three seed phases: (i) gamete development; (ii) fertilisation and early‐embryo development; and (iii) late‐embryo development. After the first two phases, we found no difference in the percentage viable seeds between populations with or without recruitment. After late‐embryo development, populations without recruitment showed a significantly lower percentage of viable seeds. These results suggest that late‐embryo development is a bottleneck in seed development. However, the complex interaction between seed viability and ripening time suggest that the causes should be in the second seed phase, as the accelerated development of male and female gametophytes may disturb the male–female synchrony for successful mating.     

From seed to seedling: A critical transitional stage for the Mediterranean psammophilous species Dianthus morisianus (Caryophyllaceae)

Abstract

Seed germination, seedling emergence and seed persistence in the soil were investigated for Dianthus morisianus (Caryophyllaceae), a psammophilous endemic species of Sardinia. Stored and freshly collected seeds were incubated in a range of constant temperatures (5–25°C) and an alternating temperature regime (25/10°C). The effect of seed burial depth on seedling emergence was investigated under controlled environmental conditions. Seed persistence in the soil was verified by in situ experimental seed burials. Seeds of this species were non-dormant, and all seed lots germinated both in the light and darkness, mainly at low temperatures (≤20°C), with a maximum at 15°C (≥95%). Optimal seedling emergence was obtained when seeds were buried at a depth of 1–2 cm, and a declining emergence with increasing depth was observed. D. morisianus was also unable to form a persistent soil seed bank. The fate of the seeds that, after dispersal, do not emerge from the soil in the spring is, therefore, presumably to die before the next favourable growing season.     

The effect of bat (Rousettus aegyptiacus) dispersal on seed germination in eastern Mediterranean habitats

The fruit-bat Rousettus aegyptiacus (Pteropodidae) in Israel consumes a variety of cultivated and wild fruits. The aim of this study was to explore some of its qualities as a dispersal agent for six fruit-bearing plant species. The feeding roosts of the fruit-bat are located an average of 30 m from its feeding trees and thus the bats disperse the seeds away from the shade of the parent canopy. The bat spits out large seeds but may pass some (2%) of the small seeds (<4 mg) through its digestive tract. However, neither the deposited seeds nor the ejected seeds (except in one case) had a significantly higher percentage germinating than intact seeds. Although the fruit-bat did not increase the percentage germinating, seeds of three plant species subject to different feeding behaviors (deposited in feces or spat out as ejecta) had a different temporal pattern of germination from the intact seeds. The combined seed germination distribution generated by these different treatments is more even over time than for each treatment alone. It is sugested that this increases asynchronous germination and therefore enhances plant fitness by spreading the risks encountered during germination, especially in eastern Mediterranean habitats where the pattern of rainfall is unpredictable.     

Seed biology and in vitro seed germination of Cypripedium

Abstract

Cypripedium orchids have high horticultural value. The populations of most species are very geographically restricted and they are becoming increasingly rare due to the destruction of native habitats and illegal collection. Reduction of the commercial value through large-scale propagation in vitro is a preferable option to reduce pressure from illegal collection. Cypripedium species are commercially propagated via seed germination in vitro. This review focuses on in vitro seed germination and provides an in-depth analysis of the seed biology of this genus.     

Effective gene dispersal and female reproductive success in Mediterranean maritime pine (Pinus pinaster Aiton)

Understanding population-scale processes that affect allele frequency changes across generations is a long-standing interest in genetic, ecological and evolutionary research. In particular, individual differences in female reproductive success and the spatial scale of gene flow considerably affect evolutionary change and patterns of local selection. In this study, a recently developed maximum-likelihood (ML) method based on established offspring, the Seedling Neighbourhood Model , was applied and exponentially shaped dispersal kernels were fitted to both genetic and ecological data in a widespread Mediterranean pine, Pinus pinaster Aiton. The distribution of female reproductive success in P. pinaster was very skewed (about 10% of trees mothered 50% of offspring) and significant positive female selection gradients for diameter (γ = 0.7293) and cone crop (γ = 0.4524) were found. The selective advantage of offspring mothered by bigger trees could be due to better-quality seeds. These seeds may show more resilience to severe summer droughts and microsite variation related to water and nutrient availability. Both approaches, ecological and of parentage, consistently showed a long-distance dispersal component in saplings that was not found in dispersal kernels based on seed shadows, highlighting the importance of Janzen-Connell effects and microenvironmental variation for survival at early stages of establishment in this Mediterranean key forest tree.