LOCAL DIVERSITY OF A BIOINDICATOR TAXON: TIGER BEETLES (COLEOPTERA: CICINDELIDAE: CICINDELA SPP.) OF THE BIG THICKET AND PINEYWOODS

摘要

Tiger beetles have been identified as important indicator taxa of regional biodiversity. In a comparison of tiger beetle diversity in the U.S., the Big Thicket and Pineywoods region (BT and PW) had significantly more species than the average species number in the U.S. Only regions elsewhere in Texas, New Mexico, Colorado, Kansas and Nebraska ranked higher than BT and PW in tiger beetle species richness. In a similar analysis of the species numbers within the ten major vegetational areas of Texas, BT and PW ranked third (17 species), after Gulf Prairies and Marshes (19 species), and the Post Oak Savannah (18 species). When species were assigned a rarity score based on their occurrence among the ten vegetational areas, such that rare taxa received a higher score, BT and PW had a low average score. This reflects the fact that many BT and PW tiger beetles are found throughout Texas. When the species richness and average rarity ranks were averaged, BT and PW had the fourth highest value of tiger beetle diversity. Nestedness analyses confirm these results and identify both regions and species of conservation interest. Two local taxa may be of special concern: one found primarily in BT and PW (Cicindela pilatei) and one typically restricted to coastal flats (Cicindela severa). These analyses of tiger beetle diversity provide support for the suggestion that the Big Thicket and Pineywoods fauna is unusually species rich and is composed of both common and rare taxa.