Les mollusques de Bourgogne-Franche-Comté : vers un nouvel inventaire.

8 pages; National audience

About the Influences of Some Major Biotic Drivers on the Population Dynamics in Host-parasite Systems: Interpretative Lessons from an Extended Nicholson-Bailey Model

Population dynamics within host-parasite systems in insects is governed by a series of factors, both endogenous and exogenous. Among them, five factors may be considered as major drivers: the respective inherent rates of increase of the host and of the parasite, the level of resource available to the host, the respective immigration rates of the host and of the parasite. While only the first two (the inherent rates of increase of host and parasite) are considered in the original Nicholson and Bailey model, an extended version of the model includes also the other three parameters, thus providing a broader (although still schematic) approach to the host-parasite population dynamics. A brief a…

Parasitic microfungi on land plants in France : a commented list of presumably unpublished taxa.

As part of an inventory of more than 800 parasitic Microfungi on land plants from the centre of France, 47 taxa reveal having no satisfactory correspondence with already described species in the usual textbooks devoted to this subject. As such, these seemingly yet unpublished taxa may constitute material of interest, for which critically commented descriptions are provided.

Covariations between shell-growth parameters and the control of the ranges of variation of functionally relevant shell-shape parameters in bivalves: a theoretical approach.

Major traits of shell shape in bivalves may alternatively be described in terms of (i) functionally relevant parameters, assumed to play a significant role in the adaptation of bivalves molluscs to their environments (such as the shell-outline elongation E, ventral convexity K, and dissymmetry D), or (ii) growth-based parameters, directly controlled by the animal. Due to the geometrical linkage between functionally-relevant and growth-based parameters, adaptive constraints that may either widen or narrow the respective ranges of variations of the functional parameters lead to the onset of specific covariations (either positive or negative) between the growth-based parameters. This has pract…

Investigations sur la distribution des arthropodes cécidogènes (inducteurs de «galles» sur les plantes) au long de la «Côte bourguignonne», entre Chatillon-sur-Seine et Mâcon.

15 pages; National audience; Les arthropodes inducteurs de galles sur les végétaux figurent parmi lesherbivores entretenant les relations les plus intimes, et corrélativement les plus étroites, avec leurs plantes hôtes respectives. À cet égard, il semble donc assez naturel de réaliser des inventaires superposables à des unités phytogéographiques caractérisées. Le présent inventaire répond à cette approche en se focalisant sur une unité bien définie, la « Côte bourguignonne » prise au sens large, de Chatillon-sur-Seine à Mâcon, les observations s’étendant à une dizaine d’alliancesphytosociologiques typiques de ces côtes calcaires en ambiance plus ou moins xérothermique.Inventaire entomologiq…

Interspecific-Competition Strongly Constrains Species-Richness and Species-Abundance Evenness in a Tropical Marine Molluscan Community Inhabiting Caulerpa Beds, as Compared to Coral-Reefs

Increasing species-richness at the local scale (within species communities) is accommodated, first, by the diversification of the niches respectively associated to species. Yet, in case of excessive supply in colonizing species issued from the regional pool, the corresponding increase in the number of solicited niches may lead to some “niche-overcrowding” resulting in significant niche-overlaps. Then, second, strong interspecific competition for shared resource can arise, triggered by the density in individuals among those species co-occurring at niche-overlaps. Accordingly, the accommodation of species-richness within a local community involves a balance between (i) the positive contributi…

Many More Consumers Not Always Induce Stronger Competition: Weaker Interspecific Competition Despite Higher Species Richness in Secondary Feeding Guild, as Compared to Primary

The species functional structuration (specifically in terms of species richness and average intensity of interspecific competition) is widely varying among species communities and this point is now very well documented in literature. But, what about the species functional structuration within the different feeding guilds that coexist in a same local community – in particular the primary and the secondary feeding guilds? Are there significant differences – or not – between them in this respect? This rather fundamental issue does not seem having been addressed yet, at least using appropriate investigative tools. However, a series of recently published case studies, precisely implementing such…

Covarying shell growth parameters and the regulation of shell shape in marine bivalves: a case study on Tellinoidea.

Specific parameters characterising shell shape may arguably have a significant role in the adaptation of bivalve molluscs to their particular environments. Yet, suchfunctionally relevantshape parameters (shell outline elongation, dissymmetry, and ventral convexity) are not those parameters that the animal may directly control. Rather than shell shape, the animal regulates shell growth. Accordingly, an alternative,growth-baseddescription of shell-shape is best fitted to understand how the animal may control the achieved shell shape. The key point is, in practice, to bring out the link between those two alternative modes of shell-shape descriptions, that is, to derive the set of equations whi…

A New, Ecologically Self-Significant Metric of Species-Abundance Unevenness, Reliably Highlighting the Intensity of Interspecific Competition

A wide series of commonly used metrics of abundance-evenness (or -unevenness) have been proposed to characterize synthetically the distributions of species-abundances, accounting for the hierarchic-like organization of species within natural communities. Among them, most – if not all–have been relevantly criticized on their serious limitations regarding both their “descriptive” and their “interpretative” capacities. From the descriptive point of view, many authors have already repeatedly emphasized the formal non-independenceof conventional (un-)evenness metrics with respect to species-richness, leading, in particular, to unacceptable bias when comparing communities differing by their speci…

Adult Shell-size Regulation in Conispirally-coiled Shells: Evidence for a Widespread Negative Covariance between Whorls Growth-rate and the Final Number of Whorls in Land Snails

As shown, in particular, by the late S.J. Gould, the involvement of a regulation process, aiming at limiting the range of intraspecific variations in adult shell size, in those land snail species with determinate growth, can be indirectly, but conveniently, diagnosed by highlighting a negative covariance between the whorls growth-rate and the whorls number reached at adulthood. However, up to now, such kind of regulation had only been demonstrated in very few cases among land snails and shelled Gastropods in general. Accordingly, quite more extensive checking is required, across both the taxonomic spectrum and the geometrical range of shell profiles. The present report is a very preliminary…

Progressive Recovery of a Marine Gastropod Community Following Atmospheric Nuclear Tests in French- Polynesia: A Socio-ecological Interpretation

Aims: The way species-richness is accommodated and how species-abundance distribution is organized in a hierarchic pattern is central to community ecology. Yet, the process by which species-richness and species-abundances are progressively accommodated can hardly be monitored, in practice, at a sufficiently large spatial scale. Fortunately, the progressive recovery of marine communities, after their complete destruction by atmospheric nuclear tests, yet offered unique opportunity to monitor the full process of accommodation of increasing species-richness and the associated, transient development of strong interspecific competition, all along the process of recovery.
 Methods: Taking fu…

Shelled-Molluscs Fauna at Abrolhos Bank (Brazil): Assessment of Both Total Species Richness and the Completed Distribution of Species Frequencies by Numerical Extrapolation of a Partial Survey

Numerous anthropogenic threats to the exceptionally rich coral-reef ecosystem at Abrolhos Bank (Brazil) arguably require implementing drastic conservation policy and meanwhile, urge for the prior detailed assessment of species richness and the species distribution across the Bank. Due to their unavoidable incompleteness, the already implemented “Rapid Assessment Surveys” at Abrolhos Bank deserve being completed, at least numerically, by implementing an appropriate extrapolation procedure, to avoid serious bias precisely due to ignoring both the number and the frequency distribution of those species still remaining undetected after Rapid Assessment Surveys. Complying with this concern, I rep…

La " Distribution des Abondances Spécifiques " : un outil dédié pour le suivi des conséquences des stress environnementaux sur la structuration des communautés à l'échelle locale.

A contribution to the inventory of parasitic microfungi on land plants in Champsaur region (French Alps, “Parc National des Ecrins”).

A preliminary investigation of the flora of parasitic microfungi on land plants is reported, focused upon the mountain and the base of the subalpine ranges, in Champsaur region, (south-western French Alps, mainly within the “Parc National des Ecrins”). Sheltered by 128 host-plant species, 182 species of microfungi have been identified. Their respective distributions, among 24 investigated localities (including four located within the Central Zone of the “Parc National des Ecrins”), are specified. Moreover, seven of these 182 microfungi do not match satisfactorily any of the consulted diagnosis in the specialized literature. Accordingly, a detailed description of the main distinctive traits …

Quantitative aspects of egg-laying behaviour contribute to the eruptive success of Cameraria ohridella parasiting horse-chestnuts.

5 pages; International audience; The invasive leaf-mining moth, Cameraria ohridella, revealed to be a consistent eruptive species throughout Europe, at the expense of its host, the common horse chest-nut tree Aesculus hippocastanum. Its repeated outbreaks, year after year, are admittedly caused, in part, by the inadequacy of the ambient cortege of natural enemies as an effective mean of control of the dynamics of populations of this pest.Less attention has been given to other parameters also contributing to the moth’s impact in term of mines density, such as (i) the degree of selectivity of C. ohridella mothers among host-leaves prior to oviposition and (ii) the average clutch-size.Although…

Characterizing the Phase Transitions between Stable Equilibrium and Periodic Oscillations in Predator-prey Population Dynamics: A Theoretical Appraisal from an Extended Nicholson & Bailey Model

Multi-phase patterns with more or less sharp phase transitions, first highlighted in thermodynamics, have progressively revealed having wider relevance, being encountered in various other contexts, for example fluid mechanics, and can even occur in the interactive dynamics in biological populations involving two or more species that share opposite interests, such as predator-prey or parasite-host pairs of species. In the latter, the pattern of abundances of both interacting species usually reaches an equilibrium level which can be either stable or cyclic (with large periodic oscillations in the latter case). Both alternative modes are separated by well-define boundaries and, accordingly, ca…

An Algebraic Derivation of Chao’s Estimator of the Number of Species in a Community Highlights the Condition Allowing Chao to Deliver Centered Estimates

Anne Chao proposed a very popular, nonparametric estimator of the species richness of a community, on the basis of a limited size sampling of this community. This expression was originally derived on a statistical basis as a lower-bound estimate of the number of missing species in the sample and provides accordingly a minimal threshold for the estimation of the total species richness of the community. Hereafter, we propose an alternative, algebraic derivation of Chao’s estimator, demonstrating thereby that Chao’s formulation may also provide centered estimates (and not only a lower bound threshold), provided that the sampled communities satisfy a specific type of SAD (species abundance dist…

Sur quelques aspects quantitatifs du comportement maternel avant ponte chez les micro-lépidoptères à larves mineuses.

9 pages; National audience

Extrapolation of the Species Accumulation Curve for Incomplete Species Samplings: A New Nonparametric Approach to Estimate the Degree of Sample Completeness and Decide when to Stop Sampling

9 pages; International audience; Incomplete species samplings are deemed to remain the common practice in those groups of animals, such as small or micro- invertebrates, with numerous species that often are more or less difficult to detect in the field. Thus, extrapolating the Species Accumulation Curve as far as possible beyond the actual sample size may thus serve as a useful (although imperfect) surrogate to the desired, but practically inaccessible, complete samplings. In this context, several kinds of theoretical or empirical models for the Species Accumulation Curve and also a lot of estimators of the asymptotic limit of the Curve (i.e. total species richness) have been proposed. The …

Inferring True Species Richness and Complete Abundance Distribution in Six Reef-fish Communities from Red-sea, Using the Numerical Extrapolation of Incomplete Samplings

Even when ecological communities are incompletely sampled (which is most frequent in practice, at least for species-rich assemblages including many rare species), it remains possible to retrieve much more information than could be expected first, by applying numerical extrapolation to incomplete field data. Indeed, recently developed procedures of numerical extrapolation of partial samplings now allow to estimate, with fair accuracy, not only the number of the still unrecorded species but, moreover, the distribution of abundances of each of these unrecorded species, thereby making available the full range of the Species Abundance Distribution, despite dealing with incomplete data only. In t…

Time-series analyses of species richness and relative abundances at the local scale: some methodological advices to secure the relevance of interpretations based on unavoidably incomplete inventories.