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Population Viability of the keeled skimmer (Orthetrum coerulescens) and metapopulation functioning of the Blue Alcon (Phengaris alcon) within the bog network of the Montselgues plateau in France1

Fifty years ago, the Montselgues plateau in France was covered by heathland and bogs. Then forestry replaced the breeding sheep economic activity leading to the reduction of the heathland and bog area and their fragmentation by forestry pine (figure 1). In 2005, the site benefits a LIFE project (http://www.life-montselgues.eu) to restore the bog network of the Montselgues plateau. In 2006, at the starting of the project, the site's conservation managers (Conservatoire des Espaces Naturels de Rhône-Alpes (CEN RA) and the Parc Naturel des Monts d'Ardeche (PNR MA)) used dragonflies populating as an indicator of the bog network habitat quality2. In 2010, by the end of the LIFE project, they contacted the station d'écologie expérimentale du CNRS à Moulis (SEEM CNRS) to assist them in evaluating whether the population of O. coerulescens was viable within the site. The SEEM proposed them to test MetaConnect 3 in an applied conservation context.


Figure 1: The bog network (red shade) of the Montselgues plateau in France (France, Ardeche, 44°30'13.63"N, 4°00'32.29"E, alt. 1032 m) is covered by heathland and bog fragmented by pine forestry.



Acquiring the demographic characteristics of the local keeled skimmer population

To estimate the demographic parameters necessary to setup MetaConnect to perform a population viability analysis (PVA), we conducted a mark-release-recapture (MRR) survey4 of O. coerulescens. The MRR study provided us for survival (Φ), population size (N) and individuals flows between bogs of the network (ψ) within the 9 capture session (i.e. weeks) of the field work (table 1).

Table 1: Survival, population size and dispersal probabilities estimated using the MARK software5 with model POPAN6 to estimate N and multistate models7 to estimate Φ and ψ for each bog of the Montselgues plateau (Narcettes: N, Cham de Chabreille: C and Granges des Rouveyrettes: R). Results are presented as mean ± SE.

Site Φ N ψ
N C R
N 0.62±0.05 434±16 NA 0.02±0.01 0.004±0.003
C 0.62±0.05 350±23 0.02±0.01 NA 0.007±0.004
R 0.62±0.05 519±19 0.004±0.003 0.006±0.003 NA


We setup and run MetaConnect with the demographic parameters estimated above to perform the PVA analysis of keeled skimmer within the bog network of the Montselgues plateau. We repeated 100 times a 200 time steps (200 years) simulation of the metapopulation dynamic. The runs were performed on the total network (3 populations) and for each patch independently to estimate the patch dependency in regard to the species maintenance and gene flow. To perform the PVA, we checked for extinction probability and genetic structure of the population8,9.

At the scale of the complete network, the extinction probability over the 200 time steps in null. In addition, the flow of individual prevents from a genetic structure within the bog network (figure 2).


Figure 2: Examples (10 runs show) of individual population dynamic (left panel) and genetic structure (Fst, right panel) of Orthetrum coerulescens within the bog network of the Montselgues plateau in France simulated with MetaConnect. At the global scale (black line) and for each bog of the network separately (Narcettes: red, Chabreille: green and Rouveyrettes: blue), the keeled skimmer population is viable and stable over the 200 time steps simulations. In addition, the low asymptotic value of Fst (0.1), shows that the actual landscape would probably have the ability to structure the population genetic.


However, if the bog network is viable, simulations considering each bog independently show that if the population size is stable over the 200 time steps, the heterozygosity (Ho) level is crashing down in Chabreille (figure 3) when Narcettes and Rouveyrettes are not threatened by inbreeding by their own. This results suggests that the smallest bog by its area and population size, should be protected from isolation.


Blue Alcon meta-population functioning

In 2013, the PNR MA and CEN RA wanted to evaluate Phengaris alcon metapopulation functioning within the Montselgues bog network. In this respect, we used MetaConnect to estimate the meta-population viability and functioning. Demographic characteristics of P. alcon are well documented 10-16 especially on the study site 17-19, but the interaction between the land cover and P. alcon dispersal abilities remains unclear. To determine P. alcon locomotor performances and behavior in a new habitat, we adapted the protocol proposed by Turlure et al. 20 and determined the rugosity coefficient for P. alcon associated with each of the different land covers it could meet within the bog network.

For the analysis of the meta-population functioning, the P. alcon population dynamic was parameterized using values extracted from the literature. Dispersal characteristics (dispersal kernel, rugosity coefficients...) were derived from a field study designed based on Turlure's and coauthor's (2011) experimental design. Suitable habitat patches were defined as buffers of 10 meters around each geolocalized Gentiana pneumonanthes which is the host plant of P. alcon.

After simulations of 100 years, results (figure 3) show that:
  1. The metapopulation would persist
  2. South-western populations cannot persist
  3. There is no dispersal between northern and southern populations
  4. Genetic differentiation would be very high between populations (a genetic cluster per population)
  5. The artificial corridor between Narcettes and Chabreille favored dispersal but not sufficiently to avoid genetic differentiation.


Figure 3: MetaConnect simulation results for P. alcon within the Montselgues bog network. Suitable habitat patches defined as 10m buffers around existing G. pneumonanthes are in black. Pies correspond to population assignation to a genetic cluster performed with STRUCTURE 21 and analyzed following the Evanno method 22. Landscape occupation during functional dispersal events follows a gradient from green (rare) to red (often).


Conclusion

MetaConnect permitted us to assist efficiently conservation managers by:
  1. Answer the question whether the population of Orthetrum coerulescens and Phengaris alcon is viable within the bog network of the Montselgues plateau.
  2. Identify the site (the Cham de Chabreille) that first requires a special attention to prevent a part of the dragonfly meta-population from inbreeding.
  3. Propose a hierarchized sequence of management to improve viability and connectivity for P. alcon (Figure 4).


Figure 4: Management proposal to improve viability and connectivity of P. alcon within the Montselgues bog network. The existing corridor is delimited by red lines. Red points correspond to areas for which the G. peumonanthes development should be favored (pasture exclusion) to relax the genetic differentiation between close populations. Red dashed lines correspond to new corridors which may improve connectivity between bogs. Red dashed circles correspond to current areas of very low quality but presenting G. pneumonanthes and for which habitat quality must be highly improved to sustain viable populations of P. alcon.



References

1 Moulherat, S., Chabbert, R., Pascault, B., Dupieux, N. & Clobert, J. Population viability of the keeled skimmer (O. coerulescens) within the bog network of the Montselgues plateau in France. (in prep).

2 Jullian, L. & Coic, B. Révision du plan de gestion 2002-2008. 1-69 (MEDDE, CR Rhône-Alpes, 2002).

3 Moulherat, S. et al. MetaConnect, a new platform for population viability modeling to assist decision makers in conservation and urban planning. Environmental Modelling & Software (submitted).

4 Lebreton, J. D. & Pradel, R. Multistate recapture models: modelling incomplete individual histories. J. Appl. Stat. 29, 353-369, doi:10.1080/02664760120108638 (2002).

5 White, G. C. & Burnham, K. P. Program MARK: survival estimation from populations of marked animals. Bird Study 46, 120-139 (1999).

6 Arnason, A. N., Baniuk, L. & Jolly, G. M. POPAN-2 - Data maintenance and analysis system for mark-recapture data -. Biometrics 35, 527-527, doi:10.2307/2530358 (1979).

7 Doligez, B. et al. Costs of reproduction: assessing responses to brood size manipulation on life-history and behavioural traits using multi-state capture-recapture models. J. Appl. Stat. 29, 407-423, doi:10.1080/02664760120108845 (2002).

8 Baguette, M., Blanchet, S., Legrand, D., Stevens, V. M. & Turlure, C. Individual dispersal, landscape connectivity and ecological networks. Biological Reviews, n/a-n/a, doi:10.1111/brv.12000 (2012).

9 Pe'er, G. et al. A Protocol for Better Design, Application, and Communication of Population Viability Analyses. Conservation Biology 27, 644-656, doi:10.1111/cobi.12076 (2013).

10 Dupont, P. (ed de l'Energie du Developpement Durable et de la Mer Ministere de l'Ecologie) 138 (Paris, 2010).

11 Als, T. D., Nash, D. R. & Boomsma, J. J. Adoption of parasitic Maculinea alcon caterpillars (Lepidoptera : Lycaenidae) by three Myrmica ant species. Animal Behaviour 62, 99-106, doi:10.1006/anbe.2001.1716 (2001).

12 Habel, J. C., Schmitt, T., Hardtle, W., Lutkepohl, M. & Assmann, T. Dynamics in a butterfly-plant-ant system: influence of habitat characteristics on turnover rates of the endangered lycaenid Maculinea alcon. Ecol. Entomol. 32, 536-543, doi:10.1111/j.1365-2311.2007.00903.x (2007).

13 Mouquet, N. et al. Conserving community modules: A case study of the endangered lycaenid butterfly Maculinea alcon. Ecology 86, 3160-3173, doi:10.1890/04-1664 (2005).

14 Nowicki, P. et al. From metapopulation theory to conservation recommendations: Lessons from spatial occurrence and abundance patterns of Maculinea butterflies. Biological Conservation 140, 119-129, doi:10.1016/j.biocon.2007.08.001 (2007).

15 Thomas, J. A., Elmes, G. W. & Wardlaw, J. C. Polymorphic growth in larvae of the butterfly Maculinea rebeli, a social parasite of Myrmica ant colonies. Proceedings of the Royal Society B-Biological Sciences 265, 1895-1901 (1998).

16 WallisDeVries, M. F. A quantitative conservation approach for the endangered butterfly Maculinea alcon. Conservation Biology 18, 489-499 (2004).

17 Rozier, Y. Contribution a l'étude de la biologie de la conservation de Maculinea sp. (Lepidoptera, Lycaenidae) dans les zones humides de la vallée du Haut-Rhône PhD thesis, Université Claude Bernard Lyon I, (1999).

18 Merlet, F. & Dupont, P. L'Azuré des mouilleres Maculinea alcon. 10 (Office pour les insectes et leur environnement, 2012).

19 Lhonoré, J. Rapport final sur la biologie, l'écologie et la répartition géographique de quatre especes de lépidoptres rhopaloceres protégés (Lycaenidae, Satyridae) dans l'ouest de la France. 130 (1996).

20 Turlure, C., Baguette, M., Stevens, V. M. & Maes, D. Species-and sex-specific adjustments of movement behavior to landscape heterogeneity in butterflies. Behavioral Ecology 22, 967-975, doi:10.1093/beheco/arr077 (2011).

21 Pritchard, J. K., Stephens, M. & Donnelly, P. Inference of population structure using multilocus genotype data. Genetics 155, 945-959 (2000).

22 Evanno, G., Regnaut, S. & Goudet, J. Detecting the number of clusters of individuals using the software STRUCTURE: a simulation study. Molecular Ecology 14, 2611-2620, doi:10.1111/j.1365-294X.2005.02553.x (2005).
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