Odonatological Abstracts

(16022) STEFFENS, W.P. & W.A. SMITH, 1999. Status survey for special concern and endangered dragonflies of Minnesota: population status, inventory and monitoring recommendations. Minnesota Dept Natural Resourses (Natural Heritage & Nongame Research Program). 56 pp. — (Addresses not stated). Status determination surveys for Ophiogomphus anomalus, O. susbehcha and Somatochlora hineana were conducted throughout eastern, central and northern Minnesota, USA. Threats to these rare spp. were evaluated and conservation and population status recommendations for Minnesota Anisoptera are presented. Baseline data on other Anisopt. in undersurveyed habitats are reported, including several state records and numerous county records. Several Zygoptera collections are also reported along with county distribution information, and recommendations for future odon. surveys and monitoring are offered. (16023) YANOVIAK, S.P, 1999. Community structure in water-filled tree holes of Panama; effects of hole height and size. Selbyana 20: 106-115. – (Evergreen St. Coll., Lab. I, Olympia, WA 98505, USA). Water-filled tree holes are common aquatic habitats in many neotropical forests, yet little is known of factors influencing their biodiversity. Here, community parameters (species richness, abundance and composition) of tree hole macroorganisms are compared at different heights (canopy, midstory, understory) in the forest of Barro Colorado Isl., Panama. Data from multiple censuses of 40 artificial tree holes during 3 wet seasons (1995-1997) revealed a small but significant decrease in the average number of spp. present with increasing height above the ground. Species richness and abundance were greater in larger holes. Similar patterns were observed in 206 natural tree holes. Of 7 top predator spp. (inch 3 odon. taxa), Megaloprepus coerulatus larvae were not found in artificial or natural holes above 7 m. Chemical properties of tree hole water did not ditfer with height, but canopy tree holes dried out more frequently and were thermally less stable than midstory and understory holes. Harsh thermal conditions and higher disturbance frequency may be responsible for the decline in species richness with height.