| host-parasitoid extinction and colonization in a fragmented prairie landscape. | few field studies of natural populations have examined the factors influencing local extinctions and colonization of empty habitat patches for a prey species and its predator. in this study, i carried out a census of planthopper (prokelisia crocea; hemiptera: delphacidae) and egg parasitoid (anagrus columbi; hymenoptera: mymaridae) incidence and densities in 147 host-plant patches (spartina pectinata; poaceae) over seven planthopper generations in a tall-grass prairie landscape. for both species ... | 2004 | 15095088 |
| from population sources to sieves: the matrix alters host-parasitoid source-sink structure. | field experiments that examine the impact of immigration, emigration, or landscape structure (e.g., the composition of the matrix) on the source sink dynamics of fragmented populations are scarce. here, planthoppers (prokelisia crocea) and egg parasitoids (anagrus columbi) were released among host-plant patches that varied in structural (caged, isolated, or in a network of other patches) and functional (mudflat matrix that impedes dispersal vs. brome-grass matrix that facilitates dispersal) conn ... | 2007 | 18229832 |
| shared parasitoids in a metacommunity: indirect interactions inhibit herbivore membership in local communities. | the interaction between species, mediated by a shared natural enemy (i.e., apparent competition), has been the subject of much theoretical and empirical investigation. however, we lack field experiments that assess the importance of apparent competition to metacommunity structure. here, i conducted a series of field experiments to test whether apparent competition, mediated by shared egg parasitoids (anagrus nigriventris and a. columbi), occurs between two abundant planthopper species (delphacod ... | 2007 | 18229833 |
| diffusion models for animals in complex landscapes: incorporating heterogeneity among substrates, individuals and edge behaviours. | 1. animals move commonly through a variety of landscape elements and edges in search of food, mates and other resources. we developed a diffusion model for the movement of an insect herbivore, the planthopper prokelisia crocea, that inhabits a landscape composed of patches of its host plant, prairie cordgrass spartina pectinata, embedded in a matrix of mudflat or smooth brome bromus inermis. 2. we used mark-release-resight experiments to quantify planthopper movements within cordgrass-brome and ... | 2008 | 18557959 |
| landscape context outweighs local habitat quality in its effects on herbivore dispersal and distribution. | past studies with spatially structured herbivore populations have emphasized the primacy of intrinsic factors (e.g., patch quality), patch geometry (e.g., patch size and isolation), and more recently landscape context (e.g., matrix composition) in affecting local population abundance and dispersal rate. however, few studies have examined the relative importance of each factor, or how they might interact to affect herbivore abundance or dispersal. here, we performed a factorial field experiment t ... | 2007 | 17120056 |
| edge behaviour in a minute parasitic wasp. | 1. changes in the density of an organism near a boundary elements (edge effects) are often thought to be generated by changes in movement behaviour, but in most cases the mechanism underlying these effects is unknown. 2. we quantified the movement behaviour of a minute parasitic wasp, anagrus columbi, in relation to edges in its habitat. this wasp attacks eggs of the planthopper prokelisia crocea, which inhabits a wet prairie ecosystem composed of patches of its host plant prairie cordgrass (spa ... | 2010 | 20002230 |