Does the presence of grassy strips and landscape grain affect the spatial distribution of aphids and their carabid predators?

Abstract

International audience1 We investigated, over the course of 2 years, the spatial distribution and abundance of two species of aphid, Metopolophium dirhodum and Sitobion avenae, and predatory species of carabid. This was undertaken in 24 wheat fields in 'coarse-grain' and 'finegrain' landscapes in western France. A greater percentage of the latter landscape was covered by hedgerows and grassland and the total area covered by fields and the average size of the fields were smaller. 2 The effects on aphid abundance of the distance from field margins, the presence of grassy strips and carabid abundance were determined in both landscapes. 3 Both aphid species were more abundant in the 'fine-grain' landscape, which may have been a result of the higher density of semi-natural elements. In both types of landscape, the total numbers of aphids were negatively correlated with the distance from the field margin. This may have been because aphids were dispersing from overwintering sites in field margins. The abundance of M. dirhodum was strongly negatively correlated with the presence of grassy strips in the 'coarsegrain' landscape, although there were no such significant correlations for either of the aphid species in the 'fine-grain' landscape. 4 Aphid and carabid abundances were negatively correlated in the 'fine-grain' and positively in 'coarse-grain' landscape. 5 The results obtained in the present study emphasize the importance of semi-natural areas in agricultural landscapes in shaping the spatial distribution of aphids and carabid beetles, their natural enemies, at different spatial scales

Landscape scale study of diversity and interaction in cereal aphids - parasitoids system (Homoptera; Hymenoptera)

“…Poluprirodna staništa, poput živica, utrina, šumaraka i vegetacije uz kanale i puteve, predstavljaju relativno stabilna staništa sa manjim stepenom narušavanja od okolnih ageoekosistema i imaju funkciju rezervoara za biljke i životinje (de Snoo, 1999;Lee et al, 2001;Marshall & Moonen, 2002;Duelli & Obrist, 2003;van Buskirk & Willi, 2004;Schmidt & Tscharntke, 2005a,b;Grüebler et al, 2008;Steingröver et al, 2010;Thomson & Hoffmann, 2010;Tscharntke et al, 2011;Al Hassan et al, 2013). Zbog toga predeli koji imaju veći procenat poluprirodnih staništa imaju i veći biodiverzitet u odnosu na predele sa velikim procentom agroekosistema (Steffan-Dewenter 2002Kruess, 2003;Purtauf et al, 2005;Schmidt et al, 2005;Holzschuh et al, 2010).…”

“…U tom slučaju se heterogenost sastava najčešće zapravo posredno izražava preko procenta prirodnih i poluprirodnih staništa. Ovaj pristup je iskoriščen u velikom broju studija (Marino & Landis, 1996;Menalled et al, 1999Menalled et al, , 2003Thies & Tscharntke, 1999;Tscharntke, 2000;Kruess, 2003;Steffan-Dewenter, 2003;Costamagna et al, 2004;Bianchi et al, 2005Bianchi et al, , 2006Thies et al, 2003Thies et al, , 2005Thies et al, , 2011Purtauf et al, 2005;Roschewitz et al, 2005;Schmidt & Tscharntke, 2005b;Tscharntke et al, , 2007Brewer et al, 2008;Schmidt et al, 2008;Vollhardt et al, 2008;Holzschuh et al, 2010;Perović et al, 2010;Chaplin-Kramer et al, 2011;Gagic et al, , 2012Winqvist et al, 2011;Caballero-López et al, 2012;Jonsson et al, 2012;Rand et al, 2012;Woltz et al, 2012a,b;Al Hassan et al, 2013;Rusch et al, 2013;Veres et al, 2013). Heterogenost konfiguracije predela pokazuje kakvi su prostorni odnosi pojedinačnih elemenata bez obzira na tip elemenata.…”

“…Ovakav sastav vrsta i velika zastupljenost velike žitne vaši je u skladu sa rezultatima nekoliko prethodnih studija (Petrović, 1996;Sigsgaard, 2002;Schmidt et al, 2003;Roschewitz et al, 2005;Thies et al, 2005;Gagic et al, 2011Gagic et al, , 2012Kos et al, 2012;Al Hassan et al, 2013), ali i u suprotnosti sa studijama koje su zabeležile drugačije odnose relativne zastupljenosti (Tomanović et al, 2008;Caballero-López et al, 2012;Lohaus et al, 2012) kao i drugačiji sastav vrsta (Brewer & Elliott, 2004;Brewer et al, 2008;Caballero-López et al, 2011). Najmanje zastupljena vrsta je bila S. maydis koja je bila prisutna samo u dva kompleksna predela u toku jedne godine.…”

“…Povećana brojnost biljnih vašiju u kompleksnim predelima je u suprotnosti sa našom početnom hipotezom, ali se podudara za rezultatima nekoliko sličnih studija Thies et al, 2005;Freier et al, 2007;Al Hassan et al, 2013;i delom u Thies et al, 2011). Međutim, postoje i studije u kojima nije zabeležen nikakav efekat kompleksnosti predela na brojnost biljnih vašiju (Vollhardt et al, 2008;CaballeroLópez et al, 2012).…”

“…Inspekcijom predela sa malim poljima utvrđeno je da na ivicama pojedinačnih polja gotovo uopšte ne postoji ivična poluprirodna vegetacija i da je ukupan procenat prirodnih i poluprirodnih staništa u predelu vrlo mali. Na taj način se predeli sa malim poljima ne razlikuju mnogo od predela sa velikim poljima što nije uobičajen slučaj, jer se u literaturi ova dva aspekta, veličina polja i procenat poluprirodnih staništa, vrlo često dovode u vezu i ne razdvajaju (Marino & Landis, 1996;Menalled et al, 1999Menalled et al, , 2003Costamagna et al, 2004;Fahrig et al, 2011;Al Hassan et al, 2013). Time se pozitivni efekat poluprirodnih staništa odvojio od efekta veličine polja što je dovelo do uočene situacije.…”