Here I report the results of two years of field manipulations in which I investigated the role of the small, annual hemiparasite, Triphysaria pusilla (Benth.
The parasitic plants at this site, mostly Triphysaria pusilla (but also a few T.
To examine the role of Triphysaria in the coastal prairie community, I selected 21 blocks, each 1 x 1 m, of low-growing prairie vegetation in early March 1994 after most germination was complete.
Finally, I calculated the Shannon-Wiener index of species diversity for each plot and used a sign test to examine whether Triphysaria removal altered host diversity in any consistent direction.
In addition to effects of Triphysaria on various host species, I also evaluated (1) the effect of different hosts and host combinations on Triphysaria performance and (2) the competitive interactions among pairs of hosts in the presence and absence of Triphysaria.
Because it was difficult to identify grasses to species before flowering and because the grasses all have fine, fibrous roots, I combined the grass species into a group that may act as functionally similar hosts for Triphysaria.
5 m in diameter that contained seedlings of all four focal taxa: Triphysaria, Lupinus, Hypochaeris, and grasses.
I also included a treatment of Triphysaria grown in the absence of any hosts to assess the extent of host dependence for this partially autotrophic parasite.
To assess whether there were any initial differences among the experimental treatments, I recorded the number of individuals of Lupinus, Hypochaeris, and Triphysaria as well as the percentage cover of grasses on 18 February.
To examine effects on individual biomass and reproductive performance, I subsampled 10 Triphysaria, Hypochaeris, and Lupinus individuals randomly from each of the plots in which they occurred.