38 



jJTcana, Symphoricarpos albus, Fhlaris arundinacea . and Rosa 

 sp. Associated aquatic species include Alisma plctntaao- 

 aquatica . Sium suave . Carex rostra ta . Lemna minor 

 (Duckweed) , Eleocharis sp. , and Callitriche heterophylla . 



4. Dcndnanoe and frequency of the taxcn: Howell ia aquatilis is 

 often distrilxited in a patchy pattern within its habitat, 

 and varies from scarce to relatively frequent (20-30% 

 cover) . It was generally observed to occi^jy less densely 

 vegetated areas. In Montana, two situaticxis were observed 

 in particular: 1.) in many ponds, the greatest densities 

 of iJ. aquatilis were found around the pond margins, under 

 the cover of surrounding overhanging shrubs ( Salix spp. , 

 Alnus incana . Comus stolon if era ) . In this zone other 

 emergent aquatic species do not occur in abundance, and H. 

 aquatilis is able to ^read throughout the open eopeas, often 

 grcving in thick mats; 2.) in ponds dominated throu^out by 

 Carex vesiceiria and/or Equisetum fluviatile, H. aquatilis 

 was frequently observed to occupy openings among such 

 vegetation. Similarly, in the central open water of some 

 ponds H, aquatilis becomes very dense (near 100% cover) . 

 While the species was found to occur amongst the stems of 

 other emergent plants, it was often not as abundant in such 

 situations. These observations suggest that y. aquatilis 

 may prefer more open microhabitats within the ponds it 

 oco^jies, and that it cannot oonpete vigorously with other 

 aquatic plant ^secies. However, at least one site in 

 Washington is dcminated by Fhalaris arundinacea (Reed Cancury 

 Grass), but iJ. aquatilis is abundant (J. Gamon, pers. 



ooiin. ) . In Idaho, the 30 individuals observed in 1988 had a 

 patchy distribution, occurring mostly in the center of the 

 pond. No observable factors appeared responsible for this 

 pattern. 



5. Suooessicnal phencnena: In Montana, the pothole pcyrds 

 inhabited by y. aquatilis appear to be at an early stage 

 within the successicxial series for such hcibitats. In 

 classifications of wetland habitat types, such ponds could 

 generally be classified as inland shallow fresh marshes 

 (Shaw and Fredine 1956) or seascral ponds (Stewcirt and 

 Kantrud 1971) . Such wetlands cire often characterized by 

 aquatic grasses (i.e, Glyceria spp., Alopecurus aequalis ) 

 and sedges (i.e., Carex vesicaria . C. rostra ta . C. 

 atherodes ) . pcaidweeds ( Potamogeton spp.), and burreeds 

 f Sparqanium spp.) (Weller 1981). With increasing 

 sedimentation and accumulaticMi of organic matter, and 

 subsequent lowering of the water table, such habitats can 

 eventually develop into sedge meadows (Reuter 1986) . 

 Numerous exanples of such meadows ccin be found in the Swcin 

 Valley in Montana. Ihey are dominated most often by Carex 

 lasiocarpa . and the water table is at or below the soil 

 surface. Such sites were never observed to contain H. 

 aquatilis . 



