Fine-scale interactions between habitat quality and genetic variation suggest an impact of grazing on the critically endangered Crau Plain grasshopper (Pamphagidae: Prionotropis rhodanica)

Piry Sylvain, Berthier Karine, Streiff Réjane, Cros-Arteil Sandrine, Foucart Antoine, Tatin Laurent, Bröder Linda, Hochkirch Axel, Chapuis Marie-Pierre. 2018. Fine-scale interactions between habitat quality and genetic variation suggest an impact of grazing on the critically endangered Crau Plain grasshopper (Pamphagidae: Prionotropis rhodanica). Journal of Orthoptera Research, 27 (1) : 61-73.

Résumé : The Crau Plain grasshopper, Prionotropis rhodanica Uvarov, 1923 (Orthoptera: Pamphagidae: Thrinchinae), is a rare grasshopper species endemic to the Crau Plain, a steppic habitat in France with unique floristic and faunistic communities. During recent decades, the area covered by these steppic grasslands has been highly reduced and fragmented due to the development of irrigation-based agriculture, roads, as well as industrial and military complexes. The restricted distribution, low population density and poor dispersal ability of P. rhodanica, combined with the destruction of its habitat, has led to the classification of this species as critically endangered in the IUCN Red List of Threatened Species. Decreases in habitat quality due to intensive grazing in the remnant grassland patches constitute an additional threat for P. rhodanica that can impact population dynamics at a relatively small-scale. In this work, we focused on a small area of about 3 km2 occupied by one of the largest subpopulations observed in 2000–2001. We conducted a single-time snapshot intensive survey of grasshopper density and genetic variation at 11 microsatellite markers. We used a recent method, MAPI, to visualize the spatial genetic structure as a continuous surface and to determine, with the simultaneous use of spatial cross-correlograms, whether the normalized difference vegetation index, which informs on the balance between vegetation productivity and grazing intensity, can explain grasshopper population structure at such a fine scale. We found that both population density and gene flow were strongly and positively correlated to habitat quality (higher productivity of grasslands and/or lower sheep grazing). The spatial scales of interaction between these variables were estimated to be highly similar, in the range of 812–880 meters. This result suggests that P. rhodanica is very sensitive to the quality of the grasslands it inhabits.

Mots-clés géographiques Agrovoc : Provence-Alpes-Côte d'Azur, France

Mots-clés libres : Conservation, Grazing, Landscape genetics, MAPI, NDVI

Classification Agris : P01 - Conservation de la nature et ressources foncières
L60 - Taxonomie et géographie animales

Champ stratégique Cirad : Axe 6 (2014-2018) - Sociétés, natures et territoires

Auteurs et affiliations

• Piry Sylvain, INRA (FRA)
• Berthier Karine, INRA (FRA)
• Streiff Réjane, INRA (FRA)
• Cros-Arteil Sandrine, INRA (FRA)
• Foucart Antoine, CIRAD-BIOS-UMR CBGP (FRA)
• Tatin Laurent, Conservatoire des espaces naturels de Provence Alpes Côte d'Azur (FRA)
• Bröder Linda, Universität Trier (DEU)
• Hochkirch Axel, Universität Trier (DEU)
• Chapuis Marie-Pierre, CIRAD-BIOS-UMR CBGP (FRA) - auteur correspondant

Source : Cirad-Agritrop (https://agritrop.cirad.fr/588051/)

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