This
PhD thesis is part of an ANR project (REPAST, 2019-2024):
“Retro-observatories of animal biodiversity during the Anthropocene: how
have global changes affected populations and communities?”.
Context
The
populations of many European bat species experienced a dramatic decline
in the 1950s-1970s, and most of them are currently considered to be
vulnerable or endangered species. Several species, widespread in all
Europe before the 1940s, became locally extinct. Scientists failed to
clearly identify the causes of such a decline. In the absence of
long-term data, international groups of bat experts listed the most
likely causes of bat decline. This hypothetical list of causes of
decline includes land-use changes, disturbance and loss of roosts,
environmental pollution, climate changes, decline of insect preys, loss
of genetic diversity, and infectious diseases. Although these are
credible, they are poorly supported by field data, and are
geographically and temporally variable. Moreover, these causes may act
simultaneously, as none of them can explain alone the decline.
In
this context, REPAST propose to crossbreed methods generally used in
paleoecology, environmental history and ecology to reconstruct long-term
history of bat populations and some of the hypothetical causes of their
decline, using three types of archives:
1) Bat guano accumulations. All bat populations exhibit a yearly life cycle: the location of their roosts varies in time (i.e. season)
and space. However, bats are known to be highly philopatric:
individuals, at least females, come back every year in their natal roost
where they can form large (and sometimes multispecies) colonies. Some
roosts have been sheltering hundreds of bats for decades, centuries or
even millennia. In these roosts, the droppings (guano) fall to the
ground and accumulate chronologically until reaching substantial
thickness over time. If these guano accumulations have not been
disturbed (trampled or mixed for instance), they can constitute
historical archives containing temporally situated information about bat
populations, environmental context, and human pressures.
2) Historical archives. The
scientific literature does not contain global long-term surveys of bat
populations before the 1990s, for most of the >40 European species,
and most of the European countries. Bat decline was first reported in
the literature in 1970, after some scientists demonstrated that colonies
of several species decreased or disappeared in all European countries.
Before the 1970s, scientists essentially focused on bat biology and
reproduction, and not on the dynamics of populations and their long-term
health evolution. However, some historical archives can help to
reconstitute global patterns of bat demography from the 1940s to
nowadays. Information about colony size, population distribution range,
and global demographic trends can be found in atlases, national
specialized journals, archives of natural history museum reports or
naturalist society reports, etc.
3) Museum specimens. During
the last decade, the use of museum specimens for biological
conservation purposes has substantially increased, mainly due to the
advent of molecular genetic approaches. Because most specimens stored in
collections are from the 19th and the beginning of the 20th Century,
museum specimens offer unique opportunities to quantify evolutionary or
microevolutionnary changes that occurred since the 19th Century,
for the reconstruction of population history. Particularly, the study
of gene pools in museum specimens and nowadays samples can help to
determine whether a low genetic variability is the consequence of recent
population declines, or represents an ancestral state.
REPAST
will (i) use biological archives (both guano accumulation and museum
specimens) for reconstituting the temporal dynamics of populations and
environmental parameters explaining the loss of animal biodiversity,
(ii) use methods of monitoring that inform about key population and
environment features that scientists failed to assess by regular
monitoring over time. Overall, the underlying hypothesis of REPAST is
that one or several stressors (habitat or climate changes, exposure to
pollutants) will be associated to temporal variations of biological
responses (pathogen prevalence, shift in diet, genetic diversity, bat
richness). The nature and the pattern of this association (what
stressor(s) is(are) linked to what response(s) and how (from long and
continuous associations to sudden shifts) will improve our understanding
of the mechanism(s) of bat decline. As some past environmental
stressors still persist nowadays, this project will contribute to the
prioritization of the current threats to animal species and their
habitats and will ultimately guide conservation measures. This
retrospective study will be used to parameterise predictive scenarios of
the evolution of animal population dynamics in relation to the
long-term predictions of different stressors.
PhD student tasks
The
PhD student will be mainly involved in work packages aiming to relate
human pressure indices and some descriptors of bat colonies through the
study of guano cores. Human pressures measured will be:
- Modifications in foraging areas: through pollen composition, pollutant concentrations, and historical data about landscapes.
- Climate changes, through the assessment of microclimate data (using data generated by meteorological stations).
These human pressures will be related to longitudinal data on: 1) bat
specific richness in colonies, the composition of bat assemblages, shift
in bat diet, and bat genetic diversity; 2) exposure to parasites.
Student
The
candidate should hold a Master degree or equivalent in ecology with a
strong interest for biological conservation and interdisciplinary
research at the interface of molecular ecology, ecotoxicology, and
history (landscape evolution). The candidate should have advanced
knowledges in statistical analyses (using the R software). A solid
knowledge in molecular ecology (in particular population genetics)
and/or ecotoxicology will be an advantage. Concerning the laboratory
analyzes (molecular analyses and analytical chemistry), the student will
be supported by technical staff, but will have to show the qualities
necessary for the correct interpretation of the data.
The
candidate should be rigorous, proactive, with a reasonable degree of
autonomy, with good organizational skills and be willing to evolve in an
interdisciplinary project. Moreover she/he should have a solid English
level and good writing skills.
Application
The
application should include 1) a cover letter describing the candidate,
her/his research interests and her/his motivation to do a PhD, 2) a CV,
3) a copy of the undergraduate and master degree, and a copy of the
master report, and 4) the names and contact information of at least two
reference persons (e-mail address and phone number). The application
should be written in French or English.
Ideally, the thesis should start at the beginning of November 2019.