Movement of two grassland butterflies in the same habitat network: the role of adult resources and size of the study area

Abstract

Abstract. 1. Movement patterns of two butterfly species (meadow brown Maniola jurtina L. and scarce copper Lycaenae virgaureae L.) were studied in a 172 ha area within a landscape with a high percentage of suitable habitats for mark-release-recapture experiments.2. Adult resource density, but not patch size or larval food plant abundance, influenced the numbers and the fractions of residents, emigrants, and immigrants.3. Differences between species were observed in movement frequency and maximum distances moved but not in mean distances moved. 4. The scarce copper showed much greater movement ability than expected from the results of published studies. This is believed to be a result of the comparatively large size of the study area and the high cover of suitable habitat (>50%).5. The mean and maximum distances travelled by butterflies reflected differences in the size of the study area.

Monitoring the impact ofBtmaize on butterflies in the field: estimation of required sample sizes

“…While the size of the field margin had an influence on butterfly abundance, it did not affect species richness, in contrast to island biogeography theory predicting the increase of species diversity with habitat area (Connor and McCoy, 1979;MacArthur and Wilson, 1967). However, other studies on butterflies have shown that factors other than habitat size are important in determining butterfly species richness, including habitat qualities (Collinge et al, 2003;Munguira and Thomas, 1992;Schneider et al, 2003;Steffan-Dewenter and Tscharntke, 1997), disturbance (Feber et al, 1996), isolation of habitat patches (Dennis and Shreeve, 1997;Summerville and Crist, 2001;Thomas et al, 2001), landscape diversity (Hodgson, 1993;Weibull et al, 2000), and species metapopulation patterns (Gutiérrez et al, 1999). In general, narrow margins along intensively managed agricultural fields are poor habitats for many butterflies, and a limited set of "typical" species seem to occur on arable field margins, colonisation by other species being dependent on increases in habitat quality rather than margin size.…”

“…Thus, it might be argued that monitoring adult butterflies is not the ideal stage to detect Bt maize effects. So far, published work is inconsistent, with some studies showing a positive correlation between number of larvae and adult butterfly abundance at a site, and others not (Munguira and Thomas, 1992;Schneider et al, 2003;Steffan-Dewenter and Tscharntke, 1997).…”

“…Diverse habitats support more butterfly species because these habitats contain more larval food plants (Niemelä and Baur, 1998;Steffan-Dewenter and Tscharntke, 1997;Thomas et al, 2001). Diverse biotopes may at the same time provide the nutritional resources for adult butterflies (Feber et al, 1996(Feber et al, , 1999Schneider et al, 2003;Steffan-Dewenter and Tscharntke, 2000), thus providing the necessary resources for both larval and adult stages in close proximity. While the size of the field margin had an influence on butterfly abundance, it did not affect species richness, in contrast to island biogeography theory predicting the increase of species diversity with habitat area (Connor and McCoy, 1979;MacArthur and Wilson, 1967).…”

“…Calculations are based on the average numbers (± 1SD) recorded in N field margins, and on the further assumptions that a twosample t-test for independent data is used, the test is one-tailed, the statistical power is 80%, the significance level α is 0.05, and the sample size is equally distributed between the two samples. Several of the species observed in field margins are unlikely to be affected by Bt maize, which potentially threatens larvae, because they reproduce at sites remote, while the adult butterflies only visit the flowers for feeding (Feber et al, 1996;Firbank et al, 2003;Schneider et al, 2003). Thus, it might be argued that monitoring adult butterflies is not the ideal stage to detect Bt maize effects.…”

Causes and consequences of animal dispersal strategies: relating individual behaviour to spatial dynamics

“…for butterflies : Hill, Thomas & Lewis, 1996 ;Kuussaari et al, 1996 ;Baguette, Petit & Quéva, 2000 ;and other insects: Kareiva, 1985;Kindvall, 1999 but no effect in Roland et al, 2000 ;Schneider et al, 2003). Traditionally, patch size has been proposed to influence emigration rates through edge to size ratios.…”