Dispersal syndromes in challenging environments: A cross-species experiment.

Dispersal is a central biological process tightly integrated into life-histories, morphology, physiology and behaviour. Such associations, or syndromes, are anticipated to impact the eco-evolutionary dynamics of spatially structured populations, and cascade into ecosystem processes. As for dispersal on its own, these syndromes are likely neither fixed nor random, but conditional on the experienced environment. We experimentally studied how dispersal propensity varies with individuals' phenotype and local environmental harshness using 15 species ranging from protists to vertebrates. We reveal a general phenotypic dispersal syndrome across studied species, with dispersers being larger, more active and having a marked locomotion-oriented morphology and a strengthening of the link between dispersal and some phenotypic traits with environmental harshness. Our proof-of-concept metacommunity model further reveals cascading effects of context-dependent syndromes on the local and regional organisation of functional diversity. Our study opens new avenues to advance our understanding of the functioning of spatially structured populations, communities and ecosystems.

Title: Ecological relevance of least cost path analysis: An easy implementation method for landscape urban planning.

Landscape connectivity promotes dispersal and other types of movement, including foraging activity; consequently, the inclusion of connectivity concept is a priority in conservation and landscape planning in response to fragmentation. Urban planners expect the scientific community to provide them with an easy, but scientifically rigorous, method to identify highly connecting contexts in landscapes. The least-cost paths (LCP) method is one of the simplest resistance-based models that could be a good candidate to spatially identify areas where movement is potentially favored in a given landscape. We tested the efficiency of LCP predictions to detect highly connecting landscape contexts facilitating individual movements compared to those performed in un-connecting landscape contexts. We used a landscape-level behavioral experiment based on a translocation protocol and individual repeated measures. In the city of Rennes (France), 30 male hedgehogs (Erinaceus europaeus) were translocated and radio-tracked in both highly connecting and un-connecting contexts, respectively, which were determined by the presence and absence of modelled LCPs. Individual movement patterns were compared between the two predicted contexts. Individuals travelled longer distances, moved faster, and were more active in the highly connecting contexts compared to the un-connecting contexts. Moreover, in highly connecting contexts, hedgehog movement followed LCP orientation, with individuals using more wooded habitats than other land cover class. By using a rigorous experimental design, this study validated the ecological relevance of LCP analysis to identify highly connecting areas, and could be easily implemented by urban landscape planners.

Bottom-up and top-down control of dispersal across major organismal groups.

Ecology and evolution unfold in spatially structured communities, where dispersal links dynamics across scales. Because dispersal is multicausal, identifying general drivers remains challenging. In a coordinated distributed experiment spanning organisms from protozoa to vertebrates, we tested whether two fundamental determinants of local dynamics, top-down and bottom-up control, generally explain active dispersal. We show that both factors consistently increased emigration rates and use metacommunity modelling to highlight consequences on local and regional dynamics.

Functional connectivity in replicated urban landscapes in the land snail (Cornu aspersum).

Urban areas are highly fragmented and thereby exert strong constraints on individual dispersal. Despite this, some species manage to persist in urban areas, such as the garden snail, Cornu aspersum, which is common in cityscapes despite its low mobility. Using landscape genetic approaches, we combined study area replication and multiscale analysis to determine how landscape composition, configuration and connectivity influence snail dispersal across urban areas. At the overall landscape scale, areas with a high percentage of roads decreased genetic differentiation between populations. At the population scale, genetic differentiation was positively linked with building surface, the proportion of borders where wooded patches and roads appeared side by side and the proportion of borders combining wooded patches and other impervious areas. Analyses based on pairwise genetic distances validated the isolation-by-distance and isolation-by-resistance models for this land snail, with an equal fit to least-cost paths and circuit-theory-based models. Each of the 12 landscapes analysed separately yielded specific relations to environmental features, whereas analyses integrating all replicates highlighted general common effects. Our results suggest that urban transport infrastructures facilitate passive snail dispersal. At a local scale, corresponding to active dispersal, unfavourable habitats (wooded and impervious areas) isolate populations. This work upholds the use of replicated landscapes to increase the generalizability of landscape genetics results and shows how multiscale analyses provide insight into scale-dependent processes.

Refining the biogeographical scenario of the land snail Cornu aspersum aspersum: Natural spatial expansion and human-mediated dispersal in the Mediterranean basin.

The land snail Cornu aspersum aspersum, native to the Mediterranean region, has been the subject of several anatomical and molecular studies leading to recognize two divergent lineages, named "East" and "West" according to their geographical distribution in North Africa. The first biogeographical scenario proposed the role of Oligocene paleogeographic events and Quaternary glacial refugia to explain spatial patterns of genetic variation. The aim of this study was to refine this scenario using molecular and morphometric data from 169 populations sampled across Mediterranean islands and continents. The two previously described lineages no longer correspond to distinct biogeographical entities. Phylogenetic relationships reveal the existence of seven clades, do not support the Tyrrhenian vicariance hypothesis, and suggest that C. a. aspersum most likely originates from North Africa. We found two contrasted patterns with the seven clades defining spatially well-structured populations in the southern Mediterranean whereas one clade is distributed across the basin. High genetic diversities and rates of endemism in North Africa support the role of this region for the diversification of C. a. aspersum. In referring to divergence times previously estimated, we suggest allopatric differentiation due to geological changes of the Atlas system and multiple refugial areas during Pleistocene glaciations. The new biogeographical scenario implies an initial range expansion from North Africa to the Iberian Peninsula and the peri-Tyrrhenian regions through land bridges connections during the Messinian Salinity Crisis and Pleistocene glaciations. Historical events appear to have also structured morphometric variation but recent dispersal events favored the emergence of secondary contacts between clades. Southern Mediterranean clades are limited to their initial distribution and populations of the recent clade would have rapidly recolonized the whole Mediterranean in the Holocene due to greater adaptive potential and the influence of human transportations.

Density-dependence across dispersal stages in a hermaphrodite land snail: insights from discrete choice models.

Dispersal movements, i.e. movements leading to gene flow, are key behaviours with important, but only partially understood, consequences for the dynamics and evolution of populations. In particular, density-dependent dispersal has been widely described, yet how it is determined by the interaction with individual traits, and whether density effects differ between the three steps of dispersal (departure, transience, and settlement), remains largely unknown. Using a semi-natural landscape, we studied dispersal choices of Cornu aspersum land snails, a species in which negative effects of crowding are well documented, and analysed them using dispersal discrete choice models, a new method allowing the analysis of dispersal decisions by explicitly considering the characteristics of all available alternatives and their interaction with individual traits. Subadults were more dispersive than adults, confirming existing results. In addition, departure and settlement were both density dependent: snails avoided crowded patches at both ends of the dispersal process, and subadults were more reluctant to settle into crowded patches than adults. Moreover, we found support for carry-over effects of release density on subsequent settlement decisions: snails from crowded contexts were more sensitive to density in their subsequent immigration choices. The fact that settlement decisions were informed indicates that costs of prospecting are not as important as previously thought in snails, and/or that snails use alternative ways to collect information, such as indirect social information (e.g. trail following). The observed density-dependent dispersal dynamics may play an important role in the ability of C. aspersum to successfully colonise frequently human-disturbed habitats around the world.

Movement propensity and ability correlate with ecological specialization in European land snails: comparative analysis of a dispersal syndrome.

Intra- and interspecific differences in movement behaviour play an important role in the ecology and evolution of animals, particularly in fragmented landscapes. As a consequence of rarer and generally more fragmented habitat, and because dispersal tends to disrupt benefits brought by local adaptation, theory predicts that mobility and dispersal should be counter-selected in specialists. Using experimental data and phylogenetic comparative tools, we analysed movement propensity and capacity, as well as dispersal-related phenotypic traits, in controlled conditions in 20 species of European land snails from the Helicoidea superfamily. Costs of movement in terrestrial gastropods are among the highest in animals, which make them a potentially powerful model to test these predictions. Habitat specialists were indeed less likely to cross a boundary between a familiar and an unfamiliar substrate than generalists. They also had smaller feet, after accounting for size. Furthermore, exploring specialists were slower than generalists and had more tortuous trajectories, leading them to stay closer to the familiar patch. Movement traits were generally evolutionary labile, but some were constrained by body size, a phylogenetically conserved trait. High specialization and low-dispersal ability are two traits often considered to increase species vulnerability to fragmentation, climate changes and extinction. This study confirms they should not be considered separately, due to their integration in a dispersal syndrome. Therefore, specialist species face double penalty under habitat loss and other environmental changes, making them more vulnerable to extinction and contributing to the biotic homogenization of communities.

Linking immune patterns and life history shows two distinct defense strategies in land snails (gastropoda, pulmonata).

Life history integration of the defense response was investigated at intra- and interspecific levels in land snails of the family Helicidae. Two hypotheses were tested: (i) fitness consequences of defense responses are closely related to life history traits such as size at maturity and life span; (ii) different pathways of the immune response based on "nonspecific" versus "specific" responses may reflect different defense options. Relevant immune responses to a challenge with E. coli were measured using the following variables: blood cell density, cellular or plasma antibacterial activity via reactive oxygen species (ROS) level, and bacterial growth inhibition. The results revealed that the largest snails did not exhibit the strongest immune response. Instead, body mass influenced the type of response in determining the appropriate strategy. Snails with a higher body mass at maturity had more robust plasma immune responses than snails with a lower mass, which had greater cell-mediated immune responses with a higher hemocyte density. In addition, ROS appeared also to be a stress mediator as attested by differences between sites and generations for the same species.

Tracing the invasion of the mediterranean land snail Cornu aspersum aspersum becoming an agricultural and garden pest in areas recently introduced.

This study is the first on the genetics of invasive populations of one of the most widely spread land mollusc species known in the world, the "Brown Snail" Cornu aspersum aspersum. Deliberately or accidentally imported, the species has become recently a notorious pest outside its native Mediterranean range. We compared the spatial structure and genetic variability of invasive (America, Oceania, South Africa) versus native populations using five microsatellite loci and mitochondrial (Cyt b and 16S rRNA) genes as a first step towards (i) the detection of potential source populations, and (ii) a better understanding of mechanisms governing evolutionary changes involved in the invasion process. Results based on multivariate analysis (Discriminant Analysis of Principal Components), Bayesian statistical inference (Clustering, Approximate Bayesian Computation) and demographic tests allowed a construction of the introduction pathways of the species over recent centuries. While emigrants originated from only one of the two native lineages, the West one, the most likely scenario involved several introduction events and "source switching" comprising (i) an early stage (around 1660) of simultaneous introductions from Europe (France, Spain) towards Oceania (New Zealand) and California, (ii) from the early 18(th) century, a second colonization wave from bridgehead populations successfully established in California, (iii) genetic admixture in invasive areas where highly divergent populations came into contact as in New Zealand. Although these man-made pathways are consistent with historical data, introduction time estimates suggest that the two putative waves of invasion would have occurred long before the first field observations recorded, both in America and in Oceania. A prolonged lag period as the use of an incorrect generation time could explain such 100-150 years discrepancy. Lastly, the contrasting patterns of neutral genetic signal left in invasive populations are discussed in light of possible ways of facing novel environments (standing genetic variation versus new mutation).

Dual strategy for immune defense in the land snail Cornu aspersum (Gastropoda, Pulmonata).

Immune defenses have been shown to be heavily involved in the evolution of physiological trade-offs. In this study, we compared the internal defense systems in two subspecies of the land snail Cornu aspersum that exhibit contrasting life-history strategies. The "fast-living" Cornu aspersum subsp. aspersa is widespread throughout the world, especially in ecosystems disturbed by man, whereas natural populations of the giant Cornu aspersum subsp. maxima, characterized by a longer life span, are present only in north Africa. Snails were experimentally challenged with Escherichia coli; the measurements used to assess their internal defense for cell- and humoral-mediated immune responses were bacterial clearance, hemocyte density, reactive oxygen species (ROS) production, and plasma antibacterial activity. Both subspecies showed a similar ability to clear bacteria from their hemolymph; however, they varied in the robustness of different individual immune components. Cornu aspersum aspersa had higher ROS activity than did C. a. maxima and lower plasma bactericidal activity. These results suggest that ecological factors can sculpt the immune response. One interpretation is that shorter life span selects for immune defenses such as ROS that, although effective, can cause long-term damage. Such different immune patterns obviously entail various costs involved in the strong intraspecific variation of life-history trade-offs we previously observed. We also have to consider that such variation might be related to intraspecific differences in the relative strength of resistance and tolerance mechanisms.

Historical biogeography of the land snail Cornu aspersum: a new scenario inferred from haplotype distribution in the Western Mediterranean basin.

BACKGROUND: Despite its key location between the rest of the continent and Europe, research on the phylogeography of north African species remains very limited compared to European and North American taxa. The Mediterranean land mollusc Cornu aspersum (= Helix aspersa) is part of the few species widely sampled in north Africa for biogeographical analysis. It then provides an excellent biological model to understand phylogeographical patterns across the Mediterranean basin, and to evaluate hypotheses of population differentiation. We investigated here the phylogeography of this land snail to reassess the evolutionary scenario we previously considered for explaining its scattered distribution in the western Mediterranean, and to help to resolve the question of the direction of its range expansion (from north Africa to Europe or vice versa). By analysing simultaneously individuals from 73 sites sampled in its putative native range, the present work provides the first broad-scale screening of mitochondrial variation (cyt b and 16S rRNA genes) of C. aspersum. RESULTS: Phylogeographical structure mirrored previous patterns inferred from anatomy and nuclear data, since all haplotypes could be ascribed to a B (West) or a C (East) lineage. Alternative migration models tested confirmed that C. aspersum most likely spread from north Africa to Europe. In addition to Kabylia in Algeria, which would have been successively a centre of dispersal and a zone of secondary contacts, we identified an area in Galicia where genetically distinct west and east type populations would have regained contact. CONCLUSIONS: Vicariant and dispersal processes are reviewed and discussed in the light of signatures left in the geographical distribution of the genetic variation. In referring to Mediterranean taxa which show similar phylogeographical patterns, we proposed a parsimonious scenario to account for the "east-west" genetic splitting and the northward expansion of the western (B) clade which roughly involves (i) the dispersal of ancestral (eastern) types through Oligocene terranes in the Western Mediterranean (ii) the Tell Atlas orogenesis as gene flow barrier between future west and east populations, (iii) the impact of recurrent climatic fluctuations from mid-Pliocene to the last ice age, (iv) the loss of the eastern lineage during Pleistocene northwards expansion phases.

Phylogeography and historical demography of the Lusitanian snail Elona quimperiana reveal survival in unexpected separate glacial refugia.

BACKGROUND: Present day distributions of Palearctic taxa in northern latitudes mainly result from populations having survived in local patches during the Late Pleistocene and/or from recolonizing populations from southern temperate refugia. If well-studied Mediterranean and eastern European refugia are widely accepted, some recent biogeographical assumptions still remain unclear, such as the occurrence of multiple glacial refugia in Iberia and cryptic refugia in northern Europe during the last glaciations. The Lusitanian snail Elona quimperiana has a remarkably disjunct distribution, limited to northwestern France (Brittany), northwestern Spain and the Basque Country. By describing the phylogeographical structure of this species across its entire range, the present study attempts to identify refugia and subsequent recolonization routes. RESULTS: Results based on 16S and COI gene sequences showed that the low genetic diversity observed in the Brittany populations should be associated with a recent demographic expansion. By contrast, populations from Spain exhibit several differentiated lineages and are characterized by demographic equilibrium, while the Basque populations are the only ones harboring typical distinct haplotypes. The center of the star-like networks of both gene sequences is occupied by a common ancestral-like haplotype found in Brittany and Spain, which might have originated from the middle of Northern Spain (i.e. Asturias, eastern Lugo and western Cantabria). Estimates of the divergence time between the Spain-Brittany and Basque lineages strongly suggest that E. quimperiana survived the Pleistocene glaciations in distinct refugia on the Iberian Peninsula, one of which is situated in Picos de Europa, and the other in the Basque Country. The occurrence of a northern refugium in France cannot be rejected as of yet. CONCLUSION: Present results confirm the Iberian origin of the land snail E. quimperiana and strongly support the emerging phylogeographic hypothesis of multiple refugia in Iberia during the last glaciations. The scenario of a spatial expansion of E. quimperiana from an Iberian refuge located in Asturias to northern areas provides the most probable explanation for the present distribution of this land snail. By harboring distinct haplotypes, the Basque Country populations appear to be of great importance in terms of potential adaptation, long term persistence and hence, the conservation of E. quimperiana.

Effect of a toxicant on phagocytosis pathways in the freshwater snail Lymnaea stagnalis.

The disturbance of plasma membrane carbohydrates and of lipopolysaccharide (LPS) ligands in relation to cytoskeletal transformations of haemocytes has been investigated after chronic exposure of pond snails (Lymnaea stagnalis) to the peroxidizing toxicant fomesafen. Neither of the two lectins used (concanavalin A and wheat germ agglutinin) showed any binding modification after incubation of the snails in the presence of the toxicant. However, after exposure of the snails to fomesafen, a clear and persistent reduction in LPS labelling of haemocytes occurred. The actin cytoskeleton of the same cells also appeared to be sensitive to the toxicant. The reduction in LPS-binding sites was related to actin staining, leading to the hypothesis that LPS ligands and actin could be similarly modulated by the toxicant. Damaged cells showed non-adherent membrane portions with reduced filopodial extrusions, exhibiting a smooth surface free of microvilli. These changes could lower the spreading and adhesion of the cells and could therefore account for the loss in their phagocytic capabilities.

Influence of temperature acclimation and gut content on the supercooling ability of the land snail Cornu aspersum.

The invasive land snail Cornu aspersum possesses a low ability to supercool (c. -5 degrees C in winter) and survives only minimal ice formation in its body fluids, what may limit its expansion to colder environments. In the present study, we investigated the influence of acclimation and starvation on its supercooling ability. During eight weeks, individuals were maintained at 20 degrees C, fed or starved, or placed at 5 degrees C, directly or with progressive acclimation to cold and shorter photoperiod. Temperature of crystallisation of whole individual (Tc(I)) and hemolymph (Tc(H)), mass data and gut content were recorded every two weeks. Hemolymphatic glucose and glycerol were measured at the end of experiment and occurrence of intestinal ice-nucleating agents (INA) was researched. Acclimation had no effect on Tc(I) but stimulated purging of the gut. Starvation induced a slight decrease of Tc(I) whereas a high quantity of alimentary particles in the digestive tract limited the supercooling ability. Glucose and glycerol were not synthesized in cold conditions. Mean Tc(H) was low (c. -17 degrees C), some INA being present in hemolymph of fed animals. Intestinal content of starved individuals exhibited a mean Tc of c. -6 degrees C, decreasing to c. -12 degrees after heating, suggesting the presence of organic INA.

[Morphological variation of the spermatheca in the garden snail Cantareus aspersus]. / Variation morphologique de la spermathèque chez l'escargot terrestre Cantareus aspersus.

Spermathecal morphology is known to play an important role in postcopulatory sexual selection of many invertebrates. In helicid land snails, the spermatheca is subdivided into tubules, whose number is sometimes subject to a strong inter-individual variation. Significance of this variation for postcopulatory sexual selection is unknown, but it might be related to cryptic female choice. In the present work, we have investigated the fine multi-tubular structure of the sperm storage organ in Cantareus aspersus. We found between 3 and 13 tubules per individual in a single population, which represents a degree of variation rarely observed in helicid land snails.

Haemocyte apoptosis as a general cellular immune response of the snail, Lymnaea stagnalis, to a toxicant.

The effects of a xenobiotic on the circulating haemocytes of Lymnaea stagnalis were investigated after short-term (24 h, 96 h) and long-term (504 h) exposure of snails to environmental concentrations. Fomesafen, a pro-oxidant generator led to the activation of the haemocyte apoptotic program by promoting reactive oxygen species (ROS). Cells entering apoptosis underwent a series of events, both on the plasma membrane and in the mitochondria; these events were quantified by flow cytofluorometry. The data showed a loss of mitochondrial transmembrane potential (Deltapsim), which was dose-dependent and time-dependent and related to an increased release of superoxide anions. The phosphatidylserine that was exposed at the outer plasma membrane was not related to the disruption of either ROS or Deltapsim but was strongly correlated with the haemocyte concentration (total haemocyte count). This cascade of apoptotic processes occurred in a dose-independent manner and was not strengthened over time. The increase of circulating haemocytes depended upon the life span of the cells and might have reflected either facilitated cell turn-over or the accompanying presence of haemocytes phagocytosing apoptotic cells.

Supercooling ability is surprisingly invariable in eggs of the land snail Cantareus aspersus.

From an ontogenetic point of view, invertebrate eggs are generally the most freezing intolerant stage of a species. Development state, water content and acclimation may affect their supercooling ability. In this study, we measured fresh mass, water content and temperature of crystallisation (T(c)) of eggs of the edible land snail Cantareus aspersus, depending on its form ("aspersa"vs. "maxima"), incubation temperature (20, 12 and 7 degrees C) and physiological age (as part of the complete development). We also tested their tolerance to freezing. Despite a high number of individual observations (n=759) and significant differences of fresh mass and water content between both subspecies, no effect of origin, incubation temperature or development state has been found in this study. T(c) remained constant whatever the condition, with an overall mean of -5.40+/-0.24 degrees C (mean+/-SD). We suggest that fresh mass is important, a high water content and a constantly wet surface confer to land snail eggs a poor ability to supercool. Moreover, the presence of ice nucleating agents at the egg surface (microorganisms present in the soil, calcium carbonate crystals of the egg shell) might induce freezing. Thus, considering the present results, to delay hatching by cryopreservation of eggs does not seem possible.

Spatial genetic pattern in the land mollusc Helix aspersa inferred from a 'centre-based clustering' procedure.

The present work provides the first broad-scale screening of allozymes in the land snail Helix aspersa. By using overall information available on the distribution of genetic variation between 102 populations previously investigated, we expect to strengthen our knowledge on the spread of the invasive aspersa subspecies in the Western Mediterranean. We propose a new approach based on a centre-based clustering procedure to cluster populations into groups following rules of geographical proximity and genetic similarity. Assuming a stepping-stone model of diffusion, we apply a partitioning algorithm which clusters only populations that are geographically contiguous. The algorithm used, which is actually part of leading methods developed for analysing large microarray datasets, is that of the k-means. Its goal is to minimize the within-group variance. The spatial constraint is provided by a list of connections between localities deduced from a Delaunay network. After testing each optimal group for the presence of spatial arrangement in the genetic data, the inferred genetic structure was compared with partitions obtained from other methods published for defining homogeneous groups (i.e. the Monmonier and SAMOVA algorithms). Competing biogeographical scenarios inferred from the k-means procedure were then compared and discussed to shed more light on colonization routes taken by the species.

Multiple paternity and postcopulatory sexual selection in a hermaphrodite: what influences sperm precedence in the garden snail Helix aspersa?

Sperm competition has been studied in many gonochoric animals but little is known about its occurrence in simultaneous hermaphrodites, especially in land snails. The reproductive behaviour of the land snail Helix aspersa involves several features, like multiple mating, long-term sperm storage and dart-shooting behaviour, which may promote sperm competition. Cryptic female choice may also occur through a spermatheca subdivided into tubules, which potentially allows compartmentalized sperm storage of successive mates. In order to determine the outcome of postcopulatory sexual selection in this species, we designed a cross-breeding experiment where a recipient ('female') mated with two sperm donors ('males'). Mates came from either the same population as the recipient or from a distinct one. To test for the influence a recipient can have on the paternity of its offspring, we excluded the effects of dart shooting by using only virgin snails as sperm donors because they do not shoot any dart before their first copulation. We measured the effects of size of mates as well as time to first and second mating on second mate sperm precedence (P2; established using microsatellite markers). Multiple paternity was detected in 62.5% of clutches and overall there was first-mate sperm precedence with a mean P2 of 0.24. Generalized linear modelling revealed that the best predictors of paternity were the time between matings and the time before first mating. Overall, both first and second mates that copulated quickly got greater parentage, which may suggest that postcopulatory events influence patterns of sperm precedence in the garden snail.

INBREEDING AND FITNESS IN THE FRESHWATER SNAIL LYMNAEA PEREGRA: AN EVALUATION OVER TWO GENERATIONS OF SELF-FERTILIZATION.

Inbreeding depression was estimated from an outbreeding population of the freshwater snail Lymnaea peregra, on the basis of two successive generations of enforced selling and outcrossing, and 70 maternal lineages. Outcrossing was analyzed under two treatments, groups of two and five individuals. The fitness parameters measured included fecundity, growth, and survival. In the first generation, we contrasted three treatments (selfers vs. paired outcrossers and group outcrossers). Very similar results were obtained between the two outcrossing treatments. A strong self-fertilization depression (which includes parental fecundity and progeny fitness) was detected in the selling treatment (about 90%). In the second generation, there was again marked evidence for self-fertilization depression, with the highest contributions coming from parental fecundity and progeny hatching rate. Our results suggest that the decreased parental fecundity is a consequence of the mating system in the previous generation, although the role of partial self-incompatibility and the copulation behavior could not be ruled out. Hatching rate and early survival data are suggestive of purging of lethal mutations. Significant variation in fitness among selfing lineages was found for most fitness traits. Our experimental design also allowed to test for interactions among fitness loci. Only one trait of the nine studied behaved as expected under synergistic interactions. However we cannot rule out some purging during the experiment, which could have biased results towards linearity. Inbreeding depression was also inferred from the change of inbreeding level across generations in the same population. We obtained a value similar to the experimental estimate.