Recovery Plan for the Northern Spotted Owl - DRAFT

Some examples of species with limited distribution include a largelyundescribed species cluster in Juga, restricted to a few streams in the WesternColumbia Gorge, Washington, and Oregon; the species Juga (C.) acutifilosa,known from only eight spring sites in northern California and southwestOregon; and Vorticifex neritoides and Physella columbiana, both restricted tothe lower 60 miles of the Columbia River. Narrowly endemic molluscs often areassociated closely with other endemic groups or species. For example, endemicarthopods and molluscs frequently inhabit the same springs in theColumbia River Gorge, and Fluminicola species are associated with the JennyCreek sucker and redband trout.In land and freshwater forms, most narrow endemics have been discoveredonly within the last decade and presumably many more will be found. Recently(spring and summer 1991), for example, a new endemic cluster of fiveFluminicola species was discovered that is restricted to two creeks and associatedsprings on the California-Oregon border in the Siskiyou Mountains.Arthropods and Other InvertebratesThe litter and soil of the forest floor are the site of some of the highest biologicaldiversity found anywhere. Scientists estimate that about 8,000 species ofarthropods inhabit a single study site in an Oregon old-growth forest, most ofthem in the soil (J. Lattin, A. Moldenke, Oregon State University, pers. comm.).To date taxonomists have been able to identify 3,400 arthropod species at theH.J. Andrews Experimental Forest (about 45 miles east of Eugene, Oregon)(Parsons et al. 1991). Invertebrates of the forest soil are critical in determiningthe long-term productivity of the forest. The soil under a square yard of forestmay hold as many as 200,000 mites from a single suborder, plus tens ofthousands of other mites, beetles, centipedes, pseudoscorpions, springtails,and "microspiders." Most of these species probably are undescribed. Thestructure and function of temperate forest soils may be determined by thedietary habits of the soil arthropods. They are the basic consumers of theforest floor where they ingest and process massive amounts of organic litterand debris, from large logs to bits of moss. The richness of arthropod speciesin old-growth forests suggests a great number of different processes andfunctions, but little is known about how these arthropods interact and survive.There are a number of species prominent in older forests that occur infrequentlyin young forests: further study undoudtedly will reveal others (A.Moldenke, Oregon State University, pers. comm.).Fifty-nine species of arthropods within the range of the northern spotted owlare listed as "species of special concern" or category 2 candidate species forfederal listing (Table D.6). Thirty-four species are category 2 candidate speciesand the remainder are designated "species of special concern". Thirty-four ofthe species are aquatic and 25 are terrestrial forms. Twenty-two of the speciesare endemic to Oregon; six to California, and none is found in all three states.This list is not exhaustive, but is representative.Several significant points can be made about the arthropods as a group thatare relevant to the recovery plan for spotted owls. First, many species areflightless, which means that their dispersal capabilities are limited. Second,the flightless condition is believed to reflect habitat stability and permanenceover a long time period. Some old forest associates have highly disjunctdistributions and are found only in undisturbed forests. They share similardistribution patterns on the west side of the Cascade Mountains from BritishColumbia south to southern Oregon and northern California (i.e., they are355