Negative interactions. 



1. Herbivores, predators, pests, parasites and diseases: Leaves of Spiranthes 

 diluvialis at most sites showed signs of browse. Even those plants 

 represented by immature rosette leaves under a continuous canopy cover of 

 grass, located in the monitoring study, had browse on one or more leaves, 

 though sometimes only the tip of the leaf. Some of the browsing may be 

 caused by whitetail deer because their numbers are high in the general area 

 and there is evidence (scat, bedding, tracks, direct observation) that they use 

 the same habitat. Alternatively, it may be caused by smaller mammals. In any 

 case, there are not the accompanying swathes of vegetation removal 

 characteristic of grazing livestock as was seen when livestock were in 

 pastures at the same time as Spiranthes diluvialis flowering. 



Livestock grazing takes place at almost all of the occurrences though it tends 

 to be earlier in the growing season when the uplands are still green rather than 

 during flowering when only the wetlands are green. Clear signs of trampled 

 plants were found at the monitoring site where livestock grazing overlapped 

 with the flowering period in part of one season. This species has a fragile 

 stem and leaves which are readily broken or damaged. The substrate is also 

 subject to trampling when it is wet. 



Browsing of the flowering stem has not been observed in Montana. By 

 contrast, vole herbivory of infloresences was identified as a significant threat 

 to the long-term survival of Spiranthes diluvialis at one Colorado site (Arft 

 1995a). 



Weevils were observed browsing some infloresences in one Gallatin and one 

 Jefferson Coimty occurrence. 



2. Competition. 



a. Intraspecific: Individual plants are unlikely to compete with one 

 another and may in fact aid in cross-pollination. Plant densities in 

 Montana are low compared to those documented in a Colorado 

 monitoring site (Arft 1995) . A relatively high density in Montana is 

 five plants per 1 x 1 m. Two of the ten occurrences had no more than 

 a total of one or two plants flowering in the entire survey area that 

 year. 



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