Mediterranean island biodiversity and climate change: the last 10,000 years and the future

Mediterranean islands (MI) are hotspots of global biodiversity and lie in one of the most susceptible to climate change (CC) areas of the world; a big challenge for any conservation strategy. In fact, there is already increasing evidence for CC in the region and associated biological responses in MI ecosystems. These include phenological changes and upward elevation shifts of species and plant communities; although evidence is frequently contrasting for different taxa. Threats are also evident, mainly for endemic species from most taxonomic groups, while communities in mountain and coastal regions are likely to be affected most. For MI conservation under CC additional factors need to be considered: (i) their position at the crossroads of three continents; with which they share common environmental characteristics, (ii) their great variability in sizes and topography and (iii) their climatic differences; with a clear west-east basin divide. CC synergies with changing tourist aspiration and agricultural practices will, in the medium term, modify island landscapes and provide further challenges for biodiversity conservation. Such a combined impact from CC, land-use change, fragmentation of habitats and tourism is difficult to predict. Furthermore, the limited space on islands (especially habitat availability and climatic range limitations) imposes a barrier to species range expansion. Thus, conservation of MI biodiversity under CC requires: (i) future research to focus on improved climate predictions linked to improved understanding of ecological (climate-biotic) responses, incorporating lessons learnt from (island) biogeography, (ii) specific adaptation measures for spatial planning and improvement in regional institutional capacities.     

Medical Product Development, Innovation, and Life-Cycle Regulation: The Challenges for Biostatistics

The article provides a perspective on the challenges for biostatistics as well as on contributions that biostatisticians are making and can make to medical product development and regulation and what the future might be in these areas. The current environment in the United States for pharmaceutical development and regulation is discussed along with the expectations that the public has for how medical products should contribute to public heath. The globalization of research and the use of study designs that incorporate multi-regional populations present new challenges for design and inference. The emerging interest in and development of the science of safety assessment and quantitative approaches to risk evaluation is considered. Guidance development, especially in the area of clinical trials design, continues to be one of the needs that FDA is asked to meet. Guidance development is proceeding for non-inferiority study designs, adaptive designs, multiple endpoints in clinical trials, and missing outcome data in clinical trials. Biostatisticians will be asked and challenged to take on leadership roles in new areas such as personalized medicine, biomarker and genomics, development of new tools for visual display of clinical data, quality assurance and monitoring in clinical trials.     

Environmental Fluctuations and Level of Density-Compensation Strongly Affects the Probability of Fixation and Fixation Times

The probability of, and time to, fixation of a mutation in a population has traditionally been studied by the classic Wright–Fisher model where population size is constant. Recent theoretical expansions have covered fluctuating populations in various ways but have not incorporated models of how the environment fluctuates in combination with different levels of density-compensation affecting fecundity. We tested the hypothesis that the probability of, and time to, fixation of neutral, advantageous and deleterious mutations is dependent on how the environment fluctuates over time, and on the level of density-compensation. We found that fixation probabilities and times were dependent on the pattern of autocorrelation of carrying capacity over time and interacted with density-compensation. The pattern found was most pronounced at small population sizes. The patterns differed greatly depending on whether the mutation was neutral, advantageous, or disadvantageous. The results indicate that the degree of mismatch between carrying capacity and population size is a key factor, rather than population size per se, and that effective population sizes can be very low also when the census population size is far above the carrying capacity. This study highlights the need for explicit population dynamic models and models for environmental fluctuations for the understanding of the dynamics of genes in populations.     

Predation by Allothrombium pulvinum on the spider mites Tetranychus urticae and Amphitetranychus viennensis: Predation Rate, Prey Preference and Functional Response

The deutonymphs of Allothrombium pulvinum Ewing (Acari: Trombidiidae) are among the most important natural enemies of spider mites in North, North East and West Iran. In this study, maximum predation rate and preference experiments were conducted with A. pulvinum deutonymphs on apple leaf discs, to determine their preference for either of two spider mite species: Amphitetranychus viennensis (Zacher) and Tetranychus urticae Koch (Acari: Tetranychidae). Maximum predation rate tests showed that the predatory mite consumed more eggs and females of T. urticae than of A. viennensis. Furthermore, the Manly’s preference index for eggs and females of T. urticae confirmed that T. urticae were the preferred prey. The functional response of A. pulvinum deutonymphs on females of T. urticae was examined over a 24-h period. Predation of A. pulvinum deutonymphs presented with females of T. urticae followed a type III functional response. Estimated handling time for the predatory mites was 4.51 h and attack coefficient b, which describes the changes in attack rate with prey densities in a type III functional response, was 0.021.     

Mucolipidosis type IV and the mucolipins

MLIV (mucolipidosis type?IV) is a neurodegenerative lysosomal storage disorder caused by mutations in MCOLN1, a gene that encodes TRPML1 (mucolipin-1), a member of the TRPML (transient receptor potential mucolipin) cation channels. Two additional homologues are TRPML2 and TRPML3 comprising the TRPML subgroup in the TRP superfamily. The three proteins play apparently key roles along the endocytosis process, and thus their cellular localization varies among the different group members. Thus TRPML1 is localized exclusively to late endosomes and lysosomes, TRPML2 is primarily located in the recycling clathrin-independent GPI (glycosylphosphatidylinositol)-anchored proteins and early endosomes, and TRPML3 is primarily located in early endosomes. Apparently, all three proteins' main physiological function underlies Ca(2+) channelling, regulating the endocytosis process. Recent findings also indicate that the three TRPML proteins form heteromeric complexes at least in some of their cellular content. The physiological role of these complexes in lysosomal function remains to be elucidated, as well as their effect on the pathophysiology of MLIV. Another open question is whether any one of the TRPMLs bears additional function in channel activity.     

Phytochemicals: the good, the bad and the ugly?

Phytochemicals are constitutive metabolites that enable plants to overcome temporary or continuous threats integral to their environment, while also controlling essential functions of growth and reproduction. All of these roles are generally advantageous to the producing organisms but the inherent biological activity of such constituents often causes dramatic adverse consequences in other organisms that may be exposed to them. Nevertheless, such effects may be the essential indicator of desirable properties, such as therapeutic potential, especially when the mechanism of bioactivity can be delineated. Careful observation of cause and effect, followed by a coordinated approach to identify the responsible entities, has proved extremely fruitful in discovering roles for phytochemical constituents. The process is illustrated by selected examples of plants poisonous to animals and include the steroidal alkaloid toxin of Veratrum californicum (Western false hellebore), piperidine alkaloids of Lupinus species (lupines), and polyhydroxy indolizidine, pyrrolizidine and nortropane alkaloids of Astragalus and Oxytropis species (locoweeds), Castanospermum australe (Moreton Bay chestnut) and Ipomoea species (morning glories).     

The phylogeny,evolutionary developmental biology,and paleobiology of the Deuterostomia: 25 years of new techniques,new discoveries,and new ideas

Over the past 25 years, new techniques, new discoveries, and new ideas have profoundly impacted our understanding of deuterostome interrelationships and, ultimately, deuterostome evolution. During the late 1980s and early 1990s morphological cladistic analyses made predictions about both taxonomic history and homology, predictions that would be tested independent of the morphological characters themselves with the advent of molecular systematics, the rise of evolutionary developmental biology, and continued exploration of the fossil record. Thanks to these three areas of inquiry, we have gone from scenarios where animals like mobile enteropneust hemichordates and chordates were derived from sessile filter-feeding animals like modern lophophorates, echinoderms, and pterobranch hemichordates, to a new perspective where hemichordates are recognized as the nearest living relative of the echinoderms, and that vagile gill-bearing animals like Cambrian vetulicolians are seen—at least by some—as close to the deuterostome last common ancestor, with both sessility and filter-feeding convergent features of deuterostomes (e.g., echinoderm) and non-deuterostomes (e.g., lophophorates) alike. Although much of the backbone of the new deuterostome phylogeny is supported by multiple independent data sets, as are statements of homology of several different morphological characters, in particular the homology of gill slits across Deuterostomia, nonetheless, the next quarter century of study on this remarkable group of animals promises to be as equally illuminating and exciting as the past quarter century.     

Prey Selection,Vertical Migrations and the Impacts of Harvesting Upon the Population Dynamics of a Predator-Prey System

A model is developed to describe the interaction between a predator and two prey types located in different regions. Conditions for stability and persistence are analysed. The effects of harvesting the predators are investigated by making the predator mortality rate habitat dependent. Results demonstrate that for any given set of parameter values there is a value of the intrinsic preference of the predator for each prey type at which the system undergoes a Hopf bifurcation. Above this critical value the system evolves towards a stable equilibrium, whereas below it, stable limit cycles arise by Hopf bifurcations. Simulations demonstrate that the presence of demographic stochasticity may destabilise oscillatory populations, thereby causing population extinctions. An application of the model to the foraging behaviour of North Sea cod is described. It is shown that if the preferred prey is more productive, it is likely that the equilibrium will be stable, whereas if the less preferred prey is more productive, populations are likely to display cycles and in the stochastic case become extinct. As cod fishing mortality is increased, the point of bifurcation and region of parameter space for which the system is unstable decreases. An increased understanding of how cod behave may enable fish stocks to be managed more successfully, for example by indicating where marine reserves should be placed.     

On the Modelling of Biological Patterns with Mechanochemical Models: Insights from Analysis and Computation

The diversity of biological form is generated by a relatively small number of underlying mechanisms. Consequently, mathematical and computational modelling can, and does, provide insight into how cellular level interactions ultimately give rise to higher level structure. Given cells respond to mechanical stimuli, it is therefore important to consider the effects of these responses within biological self-organisation models. Here, we consider the self-organisation properties of a mechanochemical model previously developed by three of the authors in Acta Biomater. 4, 613–621 (2008), which is capable of reproducing the behaviour of a population of cells cultured on an elastic substrate in response to a variety of stimuli. In particular, we examine the conditions under which stable spatial patterns can emerge with this model, focusing on the influence of mechanical stimuli and the interplay of non-local phenomena. To this end, we have performed a linear stability analysis and numerical simulations based on a mixed finite element formulation, which have allowed us to study the dynamical behaviour of the system in terms of the qualitative shape of the dispersion relation. We show that the consideration of mechanotaxis, namely changes in migration speeds and directions in response to mechanical stimuli alters the conditions for pattern formation in a singular manner. Furthermore without non-local effects, responses to mechanical stimuli are observed to result in dispersion relations with positive growth rates at arbitrarily large wavenumbers, in turn yielding heterogeneity at the cellular level in model predictions. This highlights the sensitivity and necessity of non-local effects in mechanically influenced biological pattern formation models and the ultimate failure of the continuum approximation in their absence.     

Validated age and growth estimates for the shortfin mako, Isurus oxyrinchus, in the North Atlantic Ocean

Age and growth estimates for the shortfin mako, Isurus oxyrinchus, derived from vertebral centra of 258 specimens (118 males, 140 females), ranging in size from 64 to 340 cm fork length (FL) were compared with data from 22 tag–recaptured individuals (74–193 cm FL) and length–frequency data from 1822 individuals (1035 males, 787 females; 65–215 cm FL). Annual band-pair deposition, confirmed by a concurrent bomb radiocarbon validation study, was used as the basis for band interpretation. Validation was further confirmed with a tetracycline-injected male shortfin mako recaptured after being at liberty off South Africa for 1 year and aged at 18 years. Growth rates from tag–recapture analysis (GROTAG) were higher than those derived from vertebral annuli and were only available from sharks up to 193 cm FL at recapture. Modal length–frequency data were used to verify the first four age classes. Growth curves were fit using both von Bertalanffy and Gompertz models. The 3-parameter version of the von Bertalanffy growth function produced the most biologically reasonable values for males, based on observed data (L _∞  = 253 cm FL, K = 0.125 year^?1 (estimated longevity = 21 year), and L ₀ = 72 cm). The 3-parameter version of the Gompertz growth function produced the most biologically reasonable estimates, for females (L _∞  = 366 cm FL, K = 0.087 year^?1 (estimated longevity = 38 year) and L ₀ = 88 cm. Males and females were aged to 29 (260 cm FL) and 32 years (335 cm FL), respectively. Both sexes grew similarly to age 11 (207 cm FL, 212 cm FL for males and females, respectively) when the curve leveled in males and continued to rise in females. Age at 50% maturity was estimated at 8 years for males (185 cm FL) and 18 years for females (275 cm FL). The species grows slower, matures later and has a longer life span than previously reported in North Atlantic waters.     

The Final Size of an Epidemic and Its Relation to the Basic Reproduction Number

We study the final size equation for an epidemic in a subdivided population with general mixing patterns among subgroups. The equation is determined by a matrix with the same spectrum as the next generation matrix and it exhibits a threshold controlled by the common dominant eigenvalue, the basic reproduction number R₀{\mathcal{R}_{0}}: There is a unique positive solution giving the size of the epidemic if and only if R₀{\mathcal{R}_{0}} exceeds unity. When mixing heterogeneities arise only from variation in contact rates and proportionate mixing, the final size of the epidemic in a heterogeneously mixing population is always smaller than that in a homogeneously mixing population with the same basic reproduction number R₀{\mathcal{R}_{0}}. For other mixing patterns, the relation may be reversed.     

Agri-environment schemes and butterflies: the utilisation of 6 m grass margins

The utilisation of 6 m countryside stewardship scheme (CSS) grass margins by butterflies was studied at two farms in Essex between 1997 and 2000. The aim of the study was to establish whether grass margins in cereal fields, as set up and managed under CSS guidelines, would be beneficial to common farmland butterflies. Eight 6 m grass margins (total length 3492 m) and two control sections (no margin; total length 700 m) were monitored over the first years of the agreements using the transect method. Significantly greater total numbers of butterflies and individuals of Maniola jurtina were seen on the 6 m grass margins than on the control sections. There was a significant increase in abundance of Maniola jurtina on the margins over the 4-year study period. Significantly more butterflies and Maniola jurtina were seen on the sown 6 m grass margin next to set-aside than on any of the other methods of establishment. Sown next to set-aside was best for Pyronia tithonus, but not significant.