Biology subjects

Stragier, C.

Publications and source records attributed to Stragier, C..

3 recordsLinked to original sources

bioRxiv2022

Mark loss can strongly bias demographic rates in multi-state models: a case study with simulated and empirical datasets

O_LIThe development of methods for individual identification in wild species and the refinement of Capture-Mark-Recapture (CMR) models over the past few decades have greatly improved the assessment of population demographic rates to address ecological and conservation questions. In particular, multi-state models, which offer flexibility in analysing complex study systems, have gained popularity within the ecological community. In this study, we focus on the issue of mark loss and the associated recycling of remarked individuals, which requires further exploration given the increasing use of these models. C_LIO_LITo fill this knowledge gap, we employed a wide range of simulation scenarios that reflect commonly encountered real case studies, drawing inspiration from the survival rates of 700 vertebrate species. Using a multi-state, Arnason-Schwartz (AS) modelling framework, we estimated the effects of mark loss and recycled individuals on parameter estimates. We assessed parameter bias by simulating a metapopulation system with varying capture and survival rates. Additionally, we demonstrated how mark loss can be easily estimated and accounted for using a 10-year empirical CMR dataset of bats. The bats were individually identified using Passive Integrated Transponder (PIT) tag technology as potentially lost marks and multi-locus genotypes as permanent marks. C_LIO_LIOur simulation results revealed that the occurrence of bias and the affected parameters were highly dependent on the study system, making it difficult to establish general rules to predict bias a priori. The model structure and the interdependency among parameters pose challenges in predicting the impact of bias on estimates. C_LIO_LIOur findings underscore the importance of assessing the effect of mark loss when using AS models. Ignoring such violations of model assumptions can have significant implications for ecological inferences and conservation policies. In general, the use of permanent marks, such as genotypes, should always be preferred when modelling population dynamics. If that is not feasible, an alternative is to combine two independent types of temporary marks, such as PIT tags and bands. C_LIO_LIAnalysis of our empirical dataset on Myotis myotis bats revealed that tag loss is higher in juveniles than in adults during the first year after tagging. The use of surgical glue to close the injection hole reduces tag loss rate from 28% to 19% in juveniles, while it has no effect on the tag loss rate in adults ([~]10%). The main bias observed in our metapopulation system appears in the survival rate, with up to a 20% underestimation if tag loss is not accounted for. C_LI

ecology↗

bioRxiv2019

Toxoplasma gondii in house mice Mus musculus domesticus from Dakar, Senegal: clues for oral rather than vertical mode of infection

Toxoplasma gondii is an ubiquitous highly prevalent zoonotic protozoan. Cats are the definitive hosts, while all other warm-blooded animals are intermediate hosts for this parasite. Commensal rodents, being the main preys of cats, are probably the major reservoir for T. gondii. Rodents often develop dormant tissue cysts after ingestion of oocysts shed in the environment by cats in the form of contaminated feces. Experimental evidence that vertical transmission can be sufficient to the perpetuation of transmission between generations of mice has also been found. In natural settings, the relative epidemiological importance of vertical transmission over oral transmission is a matter of debate and raises the question of the possibility of a T. gondii cycle in the absence of cats. In the present study, we took advantage of an extensive survey of commensal rodents in Dakar, Senegal, where the house mouse Mus musculus domesticus is the predominant putative reservoir of T. gondii. Host genotype and spatial location through GPS referencing of all trapping localizations were investigated in relation to T. gondii infection in 12 sites of the city of Dakar and on Goree Island. In each sampled site, the occurrence of over-prevalence zones of T. gondii infection was investigated through Kulldorfs statistic using SaTScan software. For the sites where a possible over-prevalence zone was identified, mice family lines were inferred from Discriminant Analysis of Principal Components (DAPC). In 3 of the 4 identified possible over-prevalence zones, T. gondii infection was not confined to a single family line, which suggested no association between kinship and infection occurrence. This finding rather suggests an environmental source of infection for mice associated with localized putative foci of environmental contamination and supports an oral route of infection for mice from Dakar rather than a cycle based on vertical transmission.

epidemiology↗

bioRxiv2019

Impact of historical and current features of the cityscape on the genetic structure of the house mouse (Mus musculus domesticus) in Dakar (Senegal, West Africa)

AO_SCPLOWBSTRACTC_SCPLOWPopulation genetic approaches may be used to investigate dispersal patterns of species living in highly urbanized environment in order to improve management strategies for biodiversity conservation or pest control. However, in such environment, population genetic structure may reflect both current features of the cityscape and urbanization history. This can be especially relevant when focusing on exotic commensal rodents that have been introduced in numerous primary colonial European settlements. Accounting for spatial and temporal cityscape heterogeneity to determine how past and recent demographic events may interplay to shape current population genetic structure of synanthropic rodents may provide useful insights to manage their populations. In this study, we addressed these issues by focusing on the house mouse, Mus musculus domesticus, in Dakar, Senegal, where the species may have been introduced as soon as Europeans settled in the middle of the nineteenth century. We examined genetic variation at one mitochondrial locus and 15 nuclear microsatellite markers from individuals sampled in 14 sampling sites representing different stages of urbanization history and different socio-economic environments in Dakar. We used various approaches, including model-based genetic clustering and model-free smoothing of pairwise genetic estimates. We further linked observed spatial genetic patterns to historical and current features of Dakar cityscape using random forest and Bayesian conditional autoregressive models. Results are consistent with an introduction of the house mouse at colonial time and the current genetic structure exhibits a gradient-like pattern reflecting the historical process of spatially continuous expansion of the city from the first European settlement. The genetic patterns further suggest that population dynamics of the house mouse is also driven by the spatial heterogeneity of the current cityscape, including socio-economics features, that translate in habitat quality. Our results highlight the potential importance of accounting for past demographic events to understand spatial genetic patterns of nonnative invasive commensal rodents in highly urbanized environment.

ecology↗