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.     

Alcuni aspetti della biologia della riproduzione del genere Limonium

“The New Red List of the Italian Flora” includes all the Italian policy species and other species of known conservation concerns for a total of 400 taxa, 65% of which are threatened with extinction. The Red List is based on a huge georeferenced data-set useful for conservation purposes.     

Population and reproductive structure of an endangered juniper from coastal pine forests

Plant species adapted to coastal systems are suffering severe declines. This is the case of the critically endangered Juniperus navicularis, which colonizes fossil dunes in the southwestern Iberian Peninsula and grows in the understory of pine plantations. This endemic juniper presents low reproduction rates and a decreasing number of populations has been reported in its western distribution edge. However, age structure and the demographic situation of its easternmost populations, that have been recently discovered, remain unknown. We used dendrochronological procedures to estimate the age structure of the easternmost isolated population of J. navicularis, considering three subpopulations under contrasting management regimes and selecting plots under pine cover and in open areas. We also assessed sex ratio, age at maturity and reproductive effort. We observed the predominance of 20–40 years-old stems in all study plots and a remarkable lack of young stems in open areas. Stem density was higher under pine canopies. There, junipers were, on average, younger than pine trees, meaning that junipers had grown in already forested areas. Only one sex per plot was found in all study plots but one, in which no reproductive stems were recorded, suggesting the existence of clonal growth. Reproductive effort increased with age in females, but was independent in males. We hypothesize that clonal growth might occur as a survival strategy to endure the harsher conditions of distribution edges. These results will help to develop more effective management strategies to preserve this endangered species, contributing to our understanding of dynamics of coastal ecosystems and setting the basis for future genetic studies.     

Endemic disease patterns in Paleopathology: Porotic hyperostosis

Recent research has shown that constitutional factors can elicit a porotic skeletal lesion pattern related to iron-deficiency anemia, even when adequate dietary iron is available. This study considers the pattern of skeletal involvement under conditions of chronic or endemic dietary stress. Analysis focused on 54 subadults aged 0–10 years at death from the Arroyo Hondo site. Early age of onset is documented in the pattern of coincident active periosteal reactions and porotic lesions under 6 months. Endemically inadequate diets affecting pregnant females and their fetuses, acting synergistically with immediately acquired infections, not weaning diets, are the probable major underlying causes for the early onset of iron-deficiency anemia at Arroyo Hondo.     

Biodiversity of living benthic foraminifera: How many species are there?

In ecological studies involving the analysis of  2.4 million living (stained) individual tests, to date  2140 species of benthic foraminifera have been recorded. Of these 602 species are agglutinated, 341 porcelaneous and 1197 hyaline. The numbers of species in the major environments are: marginal marine 701 (in  1.5 million individuals), shelf 989 (in  0.6 million individuals) and deep sea 831 (in  0.3 million individuals). 381 species occur in more than one major environment. Overall  33% have abundance of > 10% while  67% are of minor abundance (< 10%). The majority of species are rare, most are endemic and very few are cosmopolitan (5% or less). To estimate the potential total number of living species the following factors need to be quantified: the proportion of species already named (here considered unlikely to be less than 50% of the potential total), the number of species currently known to be dead but for which living representatives may yet to be found (assumed to be 5% = 107 species), and the proportion of species that are synonyms (10–25% = 214 to 535 species). Assuming that 50% of species have already been named (2140 + 107 = 2247), the potential total ranges from  3959 to  4280 species for 10% synonymy to  3210 to  3531 species for 25% synonymy.     

Age-structured homogeneous epidemic systems with application to the MSEIR epidemic model

In this paper, we develop a new approach to deal with asymptotic behavior of the age-structured homogeneous epidemic systems and discuss its application to the MSEIR epidemic model. For the homogeneous system, there is no attracting nontrivial equilibrium, instead we have to examine existence and stability of persistent solutions. Assuming that the host population dynamics can be described by the stable population model, we rewrite the basic system into the system of ratio age distribution, which is the age profile divided by the stable age profile. If the host population has the stable age profile, the ratio age distribution system is reduced to the normalized system. Then we prove the stability principle that the local stability or instability of steady states of the normalized system implies that of the corresponding persistent solutions of the original homogeneous system. In the latter half of this paper, we prove the threshold and stability results for the normalized system of the age-structured MSEIR epidemic model.      

Spatial patterns in a discrete-time SIS patch model

How do spatial heterogeneity, habitat connectivity, and different movement rates among subpopulations combine to influence the observed spatial patterns of an infectious disease? To find out, we formulated and analyzed a discrete-time SIS patch model. Patch differences in local disease transmission and recovery rates characterize whether patches are low-risk or high-risk, and these differences collectively determine whether the spatial domain, or habitat, is low-risk or high-risk. In low-risk habitats, the disease persists only when the mobility of infected individuals lies below some threshold value, but for high-risk habitats, the disease always persists. When the disease does persist, then there exists an endemic equilibrium (EE) which is unique and positive everywhere. This EE tends to a spatially inhomogeneous disease-free equilibrium (DFE) as the mobility of susceptible individuals tends to zero. The limiting DFE is nonempty on all low-risk patches and it is empty on at least one high-risk patch. Sufficient conditions for the limiting DFE to be empty on other high-risk patches are given in terms of disease transmission and recovery rates, habitat connectivity, and the infected movement rate. These conditions are also illustrated using numerical examples.     

Global Properties of <Emphasis Type="Italic">SIR</Emphasis> and <Emphasis Type="Italic">SEIR</Emphasis> Epidemic Models with Multiple Parallel Infectious Stages

We consider global properties of compartment SIR and SEIR models of infectious diseases, where there are several parallel infective stages. For instance, such a situation may arise if a fraction of the infected are detected and treated, while the rest of the infected remains undetected and untreated. We assume that the horizontal transmission is governed by the standard bilinear incidence rate. The direct Lyapunov method enables us to prove that the considered models are globally stable: There is always a globally asymptotically stable equilibrium state. Depending on the value of the basic reproduction number R ₀, this state can be either endemic (R ₀>1), or infection-free (R ₀≤1).     

Mutational signature of aristolochic acid: Clue to the recognition of a global disease

Mutational signatures associated with specific forms of DNA damage have been identified in several forms of human cancer. Such signatures provide information regarding mechanisms of tumor induction which, in turn, can reduce exposure to carcinogens by shaping public health policy. Using a molecular epidemiologic approach that takes advantage of recent advances in genome sequencing while applying sensitive and specific analytical methods to characterize DNA damage, it has become increasingly possible to establish causative linkages between certain environmental mutagens and disease risk. In this perspective, we use aristolochic acid, a human carcinogen and nephrotoxin found in Aristolochia herbs, to illustrate the power and effectiveness of this multidisciplinary approach. The genome-wide mutational signature for this toxin, detected initially in cancers of the upper urinary tract, has subsequently been associated with cancers of the liver and kidney. These findings have significant implications for global public health, especially in China, where millions of individuals have used Aristolochia herbal remedies as part of traditional Chinese medicine and, thus, are at risk of developing aristolochic acid nephropathy and/or upper urinary tract carcinomas. The studies reported here set the stage for research into prevention and early detection, both of which will be required to manage a potentially devastating global disease.