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

By

Piry, Sylvain
Berthier, Karine
Streiff, Réjane
Cros-Arteil, Sandrine
Tatin, Laurent
Foucart, Antoine
Bröder, Linda
Hochkirch, Axel
Chapuis, Marie-Pierre

Type

Article

Date of Publication

2018-6-12

Original Publication

Journal of orthoptera research : JOR

Volume

27

Series / Issue

Issue: 1

Pages

61--73

Subjects

Conservation , Grazing , landscape genetics , MAPI , NDVI

Contributed by

Pensoft Publishers

Language

English

Published by

Philadelphia, Penn Orthopterists' Society 1992-

Identifiers

DOI: https://doi.org/10.3897/jor.27.15036

 

Abstract

The Crau Plain grasshopper,PrionotropisrhodanicaUvarov, 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 ofP.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 forP.rhodanicathat can impact population dynamics at a relatively small-scale. In this work, we focused on a small area of about 3 km2occupied 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 thatP.rhodanicais very sensitive to the quality of the grasslands it inhabits.