AgriPop Friday Talks

Friday's Agripop Talk

19 April 2013 - 11:30 - Salle Seminaire (!)

From habitat use to habitat selection: which key factors drive breeding little bustard distribution?

Pierrick Devoucoux

 This week's talk will be about a really cool species, the Little Bustard (Tetrax tetrax). This species is also of high conservation concern (Near Threatened on the IUCN Red List) as it prefers open grasslands and undisturbed habitat -- requirements which often conflict with agricultural practices.

Whilst the species has gone extinct in several parts of Europe, especially in the east, several populations still survive in southern and western France. One remarkably high density population lives in France, in the Costière Nîmoise, near the city of Nîmes in southern France, with around 700 breeding males in an area of just 40km length! Not surprisingly the area is protected since 2006 and a current question of interest is understanding which are the key factors allowing to obtain such high population densities, as this would be quite handy to know for improving the conditions for other breeding populations.

All fine, hence? Well, not really. This year a new TGV train line will start to be build right across this protected area...

 Yeah, indeed an unfortunate state of affairs. Apparently the decision cannot be reversed, but Pierrick's work is part of an initiative funded to find ways to mitigate the impact on this important breeding population. As part of this, Pierrick has already concluded one field season last year and will present us some new results on the patterns and drivers of Little Bustard breeding habitat selection. Here the official abstract of the talk:

Conservation measures generally act on landscape composition at large and fine scale. However, global distribution and local density are not only under environmental influences. Social factors play an important role, especially in species with complex mating system. Hence the real question is about habitat selection. This study will investigate the relative weight of social and environmental factors in habitat selection on  a protected species in a high sensibility  context of conservation.

Especially, the population lives in an agricultural landscapes and agricultural practices profoundly determine and change the landscape structure. The different roles of soil occupancy on vegetation type and structure, and hence foraging availability, will be studied and the role of intra and inter sexual interactions explored. Conclusions are expected to help managers to build efficient conservation measures.

So, a really interesting talk - and as you have seen Pierrick has taken also great pictures of Little Bustards during his last field season -- so come, listen, and enjoy! And let's hope his work will help improve mitigation measures, so that also in the future we'll be able to see flocks of this bird flying and breeding in this population.

AgriPop Friday Talks

Friday's Agripop Talk

05 April 2013 - 11:30 - Salle Ragondin

Musings on community ecology by a lonely plant ecologist stuck in the forest of Chizé: Can we infer process from pattern?

Nicolas Gross

 

Image from www.stuckincustoms.com/

Stuck in the forest. Can you imagine this happening to a guy who's spent most of his (research) life so far studying nice open grasslands? Well, our research centre is indeed in the middle (sort of) of a forest but Nico is surviving, has been making escapes to study grasslands in Spain (more on that on Friday) and even started to explore the grasslands in our study area outside the forest.

So, why does Nico study grasslands? Well, plants do not escape or hide from researchers and in general do not move (except as seeds or pollen). Hence, a quite convenient study system to investigate what drives the strcture of ecological communities - the main interest of Nico's research. 

OK, but what is that 'pattern vs. process' bit? Well, that's actually a highly contentious one - here an example (hey, I know, it's a paper from 1989, so what! Still interesting to read, isn't it?). A pattern is what we see, like the configuration or traits of a system, but what we actually want to understand is which processes did generate these patterns. Unfortunately, it is often the case that a multitude of contrasting processes could have created the same patterns, which has led to decade-long debates. In general this is related to the problem of distinguishing correlation from causation (here a recent paper on that). One key process that has been often debated is the role of biotic interactions and this is what Nico will talk about this Friday. To exemplify his points he will use a grassland study system in New Zealand, similar to this:

from: http://bit.ly/SSmJZb

Well, nearly -- just 500km more south of that. And the title will actually be slightly less informal. So, here's the official abstract:

Importance of biotic interactions in structuring plant communities: Moving from patterns to processes

How biotic interactions determine the structure of plant communities is a central question in ecology. Different approaches have been used to address this question. These can be broadly separated in two categories: (i) the individual-centered approach; (ii) the community scale approach. The first approach has mainly focused on the species response to local biotic interactions (competition, facilitation) along large ecological gradients. This approach has led to a better understanding on how the intensity of biotic interactions changes depending on local environmental conditions. However, it is difficult from this approach to evaluate how biotic interactions observed at the individual scale translate at the community level and determine the properties of the whole system. 

The second approach has focused on observed pattern of species similarities or dissimilarities within communities in order to evaluate the community scale impact of biotic interactions. In this context, the use of plant functional traits has been proposed as a key metric to quantify species convergence and divergence across communities, the central assumption being that trait divergence reflects competition while trait convergence reflects the effect of environmental filtering. 

However, inferring the impact of biotic interactions from community scale patterns remains challenging because many alternative processes can lead to similar trait distributions at the community scale. For instance, while competition has been primarily hypothesized to promote trait divergence at the community level, superior competitors can also have a disproportionally large effect on local resources and thus act as an environmental filter. Facilitation has also been shown to increase trait divergence at the community level by promoting the coexistence of functionally contrasted species. Finally, abiotic factors are usually considered to cause community trait convergence. They may also act as a disruptive force when different functional strategies exhibit equal fitness in response to similar abiotic constraints (e.g. stress-avoidance vs. tolerance strategies). 

Here, I present some results from a study conducted in highly invaded grasslands (New-Zealand) where we have evaluated how biotic interactions between alien and native species determine the success of aliens in their new environment. I will show how we have tried to merge species and community scale approaches to explicitly test the importance of biotic interactions at the whole community scale.

Figure 1. Highly invaded grasslands in New-Zealand. View from Mt Herbert, 920 m (Banks Peninsula, South Island). Semi-natural grasslands are constituted by a mix of native and alien species (tussock species are Poa cita and Festuca Novae-Zelandiae). Small alien plant species dominate inter-tussock area (e.g. Poa pratense; Lolium perenne; Agrostis capillaris), while tall alien species are more abundant close to the tussocks (e.g. Holcus Lanatus; Dactylis glomerata; Arrhenatherum elatius).

So, see you all this Friday, usual time (11:30) and place.

AgriPop Friday Talks

Friday's Agripop Talk - 29 March 2013

Hey, we've got a busy day ahead -- 2 talks on the same day!

29 March 2013 - 11:00 - Salle Seminaire

Learning trophic networks : apprehending patterns and generalities from real data

David Bohan

Who eats whome and how to find this out without the need to actually observe the act of predation, or without the need of lengthy analysis of the diet -- just come and listen how David uses commonly available distribution and abundance data to infer trophic relationships between carabid beetles and weeds in arable farmlands.

David worked until recently in the UK at Rothamsted, after which he moved to Dijon to take up a IINRA DR1 position.

 

Lindy Mary Corredores Hurtado

29 March 2013 - 15:30 - Salle Ragondin
Bees and their landscape: mapping the distribution of floral resources in agricultural landscapes and their use by wild bees 

Lindy will present us her sampling plan for mapping the distribution of wild flower resources, especially of poppy flowers, and assess their use by domestic bees. Please come all and help out Lindy - she'll be keen to hear your feedback and advise!

And, what better way to finish the week listening to a talk about bees and wild flowers ... just before pub time??? :-) So, see you all there et bon weekend!

AgriPop Friday Talks

Friday's Agripop Talk

21 March 2013 - 11:15 - Salle Ragondin

The structuring processes of passerine’s communities, the share of the stochastic, environment and biotic interactions

Laura Henckel

Actually, it's a thursday talk!

Which mechanisms drive the assembly of communities is a longstanding question in ecololgy. However there is a renewed of interest for this problematic since the last decades due to some original studies : coexistence theory of Chesson (2000), Hubbell’s unified neutral theory (2001), or due to new available tools (ie. phylogenetic). But notwhithstanding the numerous studies, the debate remain open and there is no consensus amoung the various theories. The controversies concern in particular the relative importance of the processes involved (stochasticity, dispersal, biotic interactions or environmental screen).

Because it is difficult to test directly the effect of these processes via a mechanistic model, a wide range of indirect approachs were proposed in recent years. This great diversity of methods can partly explained the divergence of conclusions. Furthermore, it appears that these results are strongly dependent on the scale of analysis (spatial extent and grain), on taxa and even on the characteristic of the study site. Another thing is that a wide part of the studies on community assemblages remain theoretical and most of the others concern micro-organisms or plant communities. For these reasons further studies are needed, combining both a consistent set of methods and a multi-scale approach in a way to strengthen the results and reduce biases or misinterpretation. We therefore use some of these methods in way to understand the assembly processes that structure the passerine community in the particular context of the intensive agro-ecosystems.

This question constitutes both a scientific and societal challenge in the context of the strong decline of farmland birds observed during the past decades due to agricultural intensification.  For this purpose I will use the point count data collected between 2009 to 2012 on the workshop area “Plaine et Val de Sevre”, which are distributed on the whole area (every 1km²) allowing me to conducted a multi-scale approach by varying the grain and the extent of analysis.  A set of different methods will be used to distangle the processes involved (ie. multiple regressions on distance matrix, co-occurrence analysis) and different models will be compared (stochastic vs different determist models) to try to identify which processes are involved and at which scale. This work constitutes a preliminary study for my PhD which will focus more specifically on the environmental factors and in particular on the landscape heterogeneity effect (crop composition and configuration) on farmland birds.

AgriPop Friday Talks

Friday's Agripop Talks

  15 March 2013 - 11:30 - Salle Ragondin

The evolutionary history of Petrels: 

A microevolutionary and macroevolutionary approach 

 

Adriana Iglesias Vasquez

 Tube-nosed seabirds. Yes, exactly. This week's seminar will be about "tube-nosed seabirds in the bird order Procellariiformes" (Wikipedia docet), commonly known as petrels. But you can do much better and these birds have stimulated the immagination of poets -- you might recall:

Up above the sea's grey flatland, wind is gathering the clouds. In between the sea and clouds proudly soaring the Petrel, reminiscent of black lightning.

Glancing a wave with his wingtip, like an arrow dashing cloudward, he cries out and the clouds hear his joy in the bird's cry of courage.

In this cry -- thirst for the tempest! Wrathful power, flame of passion, certainty of being victorious the clouds hear in that bird's cry.

 Much better, isn't it? And, it turns out, petrels are also interesting from an evolutionary point of view, with a clear lack of research about their evolutionary history. And that's the subject of Adriana's PhD thesis:

Evolution in simple words is understood as the change in the form and behavior of organisms among generations. Variation in the organism’s forms occurs at all levels from DNA sequences to macroscopic morphology promoting the diversity of life (Futuyma, 1998). To understand the processes that shape such diversity evolution could be studied from two approaches acting at two levels and on two timescales: microevolution and macroevolution. Microevolution acts rapidly within populations through adaptive and neutral evolution while macroevolution occurs slowly and the patterns it produces are driven by speciation and extinction (Stearns & Hoekstra, 2005).

My thesis research will focus on these two evolutionary scales having as a biological model a group of the Procellariidae family well known as Petrels. The evolutionary history of these seabirds is unclear, as most of evolutionary studies have focused on terrestrial birds, and likely complex,  with two opposed evolutionary forces shaping its genetic structure: phylopatry and mobility. This Friday I will introduce you the three main questions from which I will develop my thesis: 

1. Is there a correlation between neutral genetic variation and morphological traits? 

2. Is the pattern of genetic differentiation concordant across molecular marker types - nuclear and mitochondrial? 

3. What is the mechanism of speciation that better explains the formation of new species of Petrels?

Thus, come this Friday - usual time and place: 11:30 Salle Ragondin.

And the Petrel soars while crying, reminiscent of black lightning, like an arrow piercing the clouds, 

with his wing rips foam from the waves.

...

AgriPop Friday Talks

Friday's Agripop Talks

  08 March 2013 - 11:30 - Salle Ragondin

Spatial depletion models highlight distribution rules of foraging sea ducks

Vincent Tolon

Seaducks? Yes, there are also ducks in the sea, not only in your local lake! And what do they eat? Clams and other shellfish - but no, not exactly as you are just thinking:

Immage downloaded from http://bit.ly/YCSM3G

... but indeed the same ones that we humans enjoy eating. And one problem with similar resources is that, once a forager takes them, they get depleted! So, how to forage for similar resources? Vincent will address this question using a population of seaducks living on the northern coast of France as study system. Here's a summary from Vincent of what he will show us this week:

Understanding distribution rules of foragers in their environment is one of the main topics of behavioural ecology. For predators that prey on non-renewable resources, depletion (i.e. the simple removal of food that other individuals can consume) is a likely mechanism driving population distributions. Since two decades, spatial depletion models (SDMs) have been developed to predict effects of resource depletion on predator distributions. These models commonly predict that predators should first exploit the richest patch, and include other patches when they become as profitable as previously depleted areas. 

SDMs can help determining how the distribution should change in response to resource depletion, and can provide a reference over which more complex distribution rules (e.g. density dependence) can be tested. We located groups of common scoters Melanitta nigra foraging on benthic communities on a French coast used as wintering areas. We first tested if simple “Ideal Free” SDMs can explain theirs seasonal distribution dynamics between and within large ranges (areas of several dozen of km²). We tested such models for different combination of prey type and determined how much the model/data matching can be explained by density variations.

And here also a cool GIF of Vincent's model predictions:

Cool, isn't it? So, come and listen!

AgriPop Friday talks

Friday's Agripop Talks

01 March 2013 - 11:30 - Salle Ragondin

Land use influences the ground beetle Poecilus cupreus at different spatial and temporal scales in an agricultural landscape

Ronan Marrec

Certains facteurs peuvent contraindre la distribution et les abondances des espèces. L'abondance d'une population à n'importe quel endroit d'un paysage a été résumée comme fonction des taux de natalité et de mortalité; la capacité intrinsèque de l'espèce à se disperser et se déplacer au sein et entre les sites; et l'accessibilité des sites aux individus dispersant.

Dans les environnements complexes et instables, tels que les agroécosystèmes, l'accessibilité et la favorabilité des habitats pourraient être restreintes, pour deux raisons majeures. Premièrement, la plupart des cultures sont annuelles, et deuxièmement, la plupart des cultures ont des phénologies asynchrones et variant dans le temps. En conséquence, les terres arables ne fournissent pas un habitat constant au cours de l'année et d'une année sur l'autre.
Dans de tels environnements changeants, j'étudie (i) quels types d'éléments paysagers affectent les patrons de distribution et d'abondance chez un Coléoptère carabique très abondant dans les agrosystèmes de l'ouest de la France, Poecilus cupreus (L.), et (ii) à quelle(s) échelle(s) ils influences ces patrons. Je vous présenterai vendredi 1er mars mes résultats sur ce sujet...

Some factors constrain species' distribution and abundances. The population abundance at any location in a landscape has been summarized as a function of local birth and death rates; the intrinsic ability of species to disperse and move within and between areas; and the accessibility of sites to dispersing individuals.

In complex and unstable environments, such as agroecosystems, accessibility and suitability of habitats could be restricted in time and space, for two main reasons. First, much of the fields are annual, and secondly, much crop identities have asynchronous and varying phenologies. As a consequence, arable fields do not provide a constant habitat throughout the year and from one year to another.
In such moving environments, I am studying (i) which kinds of environmental features affect distribution and abundance patterns in a very abundant carabid beetle in our agrosystems in Western France, Poecilus cupreus (L.), and (ii) at which scale(s) they influence these patterns. I will present you on Friday 1st March my results on this subject...