Frank Cézilly

Conflict between co-occurring manipulative parasites? An experimental study of the joint influence of two acanthocephalan parasites on the behaviour of Gammarus pulex

When two parasite species are manipulators and have different definitive hosts, there is a potential for conflict between them. Selection may then exist for either avoiding hosts infected with conflicting parasites, or for hijacking, i.e. competitive processes to gain control of the intermediate host. The evidence for both phenomena depends largely on the study of the relative competitive abilities of parasites within their common intermediate host. We studied the effects of simultaneous infection by a fish acanthocephalan parasite, Pomphorhynchus laevis, and a bird acanthocephalan parasite, Polymorphus minutus, on the behaviour of their common intermediate host, the amphipod Gammarus pulex. We compared the reaction to light and vertical distribution of individuals infected with both parasites to those of individuals harbouring a single parasite species and uninfected ones under controlled conditions. Compared to uninfected gammarids that were photophobic and tended to remain at the bottom of the water column, P. laevis-infected gammarids were attracted to light, whereas P. minutus-infected individuals showed a modified vertical distribution and were swimming closer to the water surface. The effects of both P. laevis and P. minutus appeared to be dependent only on their presence, not on their intensity. Depending on the behavioural trait under study, however, the outcome of the antagonism between P. laevis and P. minutus differed. The vertical distribution of gammarids harbouring both parasites was half-way between those of P. laevis- and P. minutus-infected individuals, whereas P. laevis was able to induce altered reaction to light even in the presence of P. minutus. We discuss our results in relation to the occurrence of active avoidance or hijacking between conflicting manipulative parasites and provide some recommendations for future research.

Sex- and age-related variation in survival and cost of first reproduction in greater flamingos

We analyzed survival of breeding Greater Flamingos, Phoenicopterus ruber roseus, using the capture histories of 2000 breeding birds ringed as chicks and resighted at their natal colony in the Camargue, southern France. As found in previous analyses, recapture probability varied according to year, sex, and age of the bird, and annual survival was strongly affected by winter severity. However, by using a much larger data set than in earlier analyses, we detected previously nonsignificant effects. Indeed, for the first time, sex and age of the bird were found to influence annual survival probability. We tested the hypothesis that the observed sex-related difference in survival corresponded to asymmetric costs of reproduction. A model including a cost of first observed reproduction on survival in young females only provided the best fit to the data and explained the majority of the sex-related difference in survival of birds <7 yr old. Because a cost of reproduction may be partially masked by birds that have already bred undetected, we estimated the proportion of experienced females among those observed breeding for the first time. This proportion varied with the age of the birds and was used to calculate the expected cost of early recruitment. Such a cost of early reproduction may have contributed to the evolution of deferred breeding in females. Survival of experienced females was higher than that of males, with the difference being more pronounced in early age classes. Age had a significant positive effect on survival probability of birds.

Personality predicts social dominance in female zebra finches, Taeniopygia guttata, in a feeding context

Although personality has been defined as a suite of correlated behaviours, most studies of animal personality actually consider correlations between a few traits. We examined the repeatability and correlational structure of five potential personality traits (activity, neophobia, exploratory tendencies, risk-taking behaviour and obstinacy), in female zebra finches. In addition, we assessed to what extent personality influenced social dominance in a feeding context in this gregarious species. All personality traits were found to be highly repeatable within individuals. In addition, except for obstinacy, all of them were related to each other, thus defining a behavioural syndrome. Social dominance was predicted by personality, with proactive individuals being more likely to be dominant. Our results suggest that personality can be considered as a new static factor influencing within-group hierarchies. We finally discuss these results in terms of the consequences for the evolution of personalities and the need to take several traits into account to provide full descriptions of individual personality.

Permanent Genetic Resources added to Molecular Ecology Resources Database 1 December 2009-31 January 2010

This article documents the addition of 220 microsatellite marker loci to the Molecular Ecology Resources Database. Loci were developed for the following species: Allanblackia floribunda, Amblyraja radiata, Bactrocera cucurbitae, Brachycaudus helichrysi, Calopogonium mucunoides, Dissodactylus primitivus, Elodea canadensis, Ephydatia fluviatilis, Galapaganus howdenae howdenae, Hoplostethus atlanticus, Ischnura elegans, Larimichthys polyactis, Opheodrys vernalis, Pelteobagrus fulvidraco, Phragmidium violaceum, Pistacia vera, and Thunnus thynnus. These loci were cross‐tested on the following species: Allanblackia gabonensis, Allanblackia stanerana, Neoceratitis cyanescens, Dacus ciliatus, Dacus demmerezi, Bactrocera zonata, Ceratitis capitata, Ceratitis rosa, Ceratits catoirii, Dacus punctatifrons, Ephydatia mülleri, Spongilla lacustris, Geodia cydonium, Axinella sp., Ischnura graellsii, Ischnura ramburii, Ischnura pumilio, Pistacia integerrima and Pistacia terebinthus.

Differential Mortality of Two Closely Related Host Species Induced by One Parasite

Understanding the importance of parasites in affecting the biodiversity of host species in ecosystems is a central aim of conservation biology. Recent advances in ecology have suggested that differential parasite susceptibilities between taxonomically related host species may be a determinant of animal community structure. Although conceptually appealing, such an hypothesis suffers from a lack of field evidence. Here, we report that the populations of two congeneric and sympatric host species (Gammarus insensibilis and G. aequicauda), infected by the same parasite (Microphallus Papillorobustus), exhibit a strongly contrasted pattern of parasite-induced mortality.

LOCAL RECRUITMENT IN THE GREATER FLAMINGO: A NEW APPROACH USING CAPTURE–MARK–RECAPTURE DATA

Although the establishment of new individuals in the breeding component of a population is an essential feature of population regulation, only a few attempts have been made to test biological hypotheses about recruitment. Most previous studies rely on ad hoc calculations or are flawed with unwarranted assumptions about survival. We use a recently developed approach, based on capture-mark-recapture, in which analysis of local recruitment is similar to a time-reversed analysis of survival. The basic data set consists of capture histories viewed in reverse order, with initial capture at year of birth, and subsequent observations corresponding to years when the animal has bred. The model considers two essential components, the probability for any breeding individual to reproduce for the first time (a, the probability of first reproduction) and the probability of recapture (p), both conditional on survival. Contrary to previous attempts at modeling recruitment, the present approach does not assume an age at which breeding propensity stabilizes to a maximum value. The flexibility achieved allows the comparison of recruitment among groups within a population and also allows one to consider the effects of environmental variables, as well as interactions between such effects. Practically, the procedure starts from a global model, based upon the a priori knowledge of the biology of the species, and assesses its fit. Then more parsimonious models are selected using Akaikes Information Criterion and likelihood ratio tests. Finally, maximum likelihood estimates of model pa- rameters are obtained with estimates of precision. We used a modified version of program RELEASE for goodness-of-fit tests, and program SURGE for iterative model fitting and the computation of likelihood ratio tests. We illustrate the method with the study of local recruitment of Greater Flamingos (Phoenicopterus ruber roseus) in the Camargue (southern France) between 1984 and 1994. We found additive effects of age and year to affect recruitment. Breeding propensity increased with age. Recruitment was noticeably higher in the year following an increase in mortality rate due to a particularly severe winter. Long- lasting effects of this increased mortality on recruitment were observed in the three fol- lowing years. There was no evidence for an effect of sex or cohort (year of birth) on recruitment. However, sex, as well as time and age, affected recapture rates. We discuss the various advantages and limitations of the model for the study of local recruitment in long-lived species and mention some potential developments.

The effect of the acanthocephalan parasite Pomphorhynchus laevis on the lipid and glycogen content of its intermediate host Gammarus pulex.

Besides conspicuous changes in behaviour, manipulative parasites may also induce subtle physiological effects in the host that may also be favourable to the parasite. In particular, parasites may be able to influence the re-allocation of resources in their own favour. We studied the association between the presence of the acanthocephalan parasite, Pomphorhynchus laevis, and inter-individual variation in the lipid and glycogen content of its crustacean host, Gammarus pulex (Amphipoda). Infected gravid females had significantly lower lipid contents than uninfected females, but there was no difference in the lipid contents of non-gravid females and males that were infected with P. laevis. In contrast, we found that all individuals that were parasitised by P. laevis had significantly increased glycogen contents, independent of their sex and reproductive status. We discuss our results in relation to sex-related reproductive strategies of hosts, and the influence they may have on the level of conflict over energy allocation between the host and the parasite.

Breeding success and mate retention in birds: a meta-analysis

Abstract. Several hypotheses about the adaptive value of divorce in birds predict a positive effect of breeding success on mate retention. Although some studies have provided direct support for this prediction, others have failed to demonstrate any significant influence of breeding success on mate retention. To date, no one has investigated the overall empirical evidence for such a relationship. We used a meta-analysis of published results to investigate whether the rate of divorce between consecutive breeding seasons differed between successful and unsuccessful breeders among monogamous bird species. The analysis was based on 38 studies involving 35 different species. The mean weighted effect size, measured as the Pearson product-moment correlation coefficient, was 0.112 and differed significantly from zero. Despite the relatively low mean effect size, this finding is extremely robust given the large fail-safe number, indicating that more than 1,333 additional nonsignificant studies would be necessary to reduce the effect size to a nonsignificant value. There was no evidence that year of publication had a significant influence on the results. Comparing between species, the difference in divorce rates between unsuccessful and successful pairs was negatively related to clutch size, even after controlling for phylogenetic dependence and the potential effect of adult survival rate. This indicates that the traditional measure of breeding success (failed versus fledged at least one young) may not be appropriate for species that typically lay large clutches. Therefore, the relatively moderate overall effect of breeding success on divorce might be considered as an underestimation of the true effect.

COMPARATIVE EVIDENCE FOR A POSITIVE ASSOCIATION BETWEEN DIVORCE AND EXTRA-PAIR PATERNITY IN BIRDS

Although most bird species are socially monogamous, they show a large variation in both divorce rate and the proportion of extra-pair paternity (EPP). Recently, adaptive explanations of avian monogamy have considered divorce and EPP as related behavioural strategies by which individuals paired with low quality mates can improve their breeding status within ecological and time constraints. It has been suggested that, at both the intra- and inter-specific levels, divorce rate should be associated with the frequency of EPP. Divorce and EPP could coexist as alternative strategies whose relative frequencies would depend on ecological conditions, resulting in a negative association between the two phenomena. Or, they can be seen as synergistic tactics co-varying with variation in mate quality between populations or species and are thus positively associated. Here, applying two different comparative methods: the comparison of independent linear contrast and the pairwise comparison of closely related taxa, we show that high rates of divorce are positively associated with high rates of extra-pair paternity in socially monogamous species of birds, even when controlling for survival rate as a potentially confounding variable. This constitutes the first comparative evidence for a relation between divorce and adultery in animals. We discuss this result in relation to recent hypotheses on the adaptiveness of divorce and extra-pair copulations in birds and natural variation in mate quality among populations or species. The pattern found is most consistent with the hypothesis that birds may divorce to gain a better breeding position, but alternatives cannot be fully ruled out.

Differential influence of Pomphorhynchus laevis (Acanthocephala) on the behaviour of native and invader gammarid species

Although various species of acanthocephalan parasites can increase the vulnerability of their amphipod intermediate hosts to predation, particularly by altering their photophobic behaviour, their influence on the structure of amphipod communities and the success of invader species has so far received little attention. We compared the prevalence and behavioural influence of a fish acanthocephalan parasite, Pomphorhynchus laevis, in two species of amphipods, Gammarus pulex and Gammarus roeseli in sympatry in the river Ouche (Burgundy, eastern France). There, G. pulex is a resident species, whereas G. roeseli is a recent coloniser. Both uninfected G. pulex and G. roeseli were strongly photophobic. although less so in the invading species. However, there was no significant difference in reaction to light between infected and uninfected G. roeseli, whereas infected G. pulex were strongly photophilic. We discuss our results in relation to the parasites ability to manipulate invading host species, the possibility that resistant individuals have been selected during the invasion process, and the role that acanthocephalan parasites can play in shaping the structure of amphipod communities.