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Zur Biologie und Überlebensstrategie der Sandlaufkäfer offener Habitate zentralamazonischer Überschwemmungsgebiete (Col.: Carabidae: Cicindelinae) (Brasilien)


Zerm,  M.
Working Group Tropical Ecology, Max Planck Institute for Limnology, Max Planck Institute for Evolutionary Biology, Max Planck Society;

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Zerm, M. (2002). Zur Biologie und Überlebensstrategie der Sandlaufkäfer offener Habitate zentralamazonischer Überschwemmungsgebiete (Col.: Carabidae: Cicindelinae) (Brasilien). Amazoniana, 17(1/2), 249-282.

Life cycles, habitats, activity patterns, and other parameters were investigated during 1997-1999 in eight tiger beetle species inhabiting open habitats in white- and blackwater floodplains in the Manaus region (Brazil). Field work was carried out mainly at the southern beach of Ilha de Marchantaria (an island in the Amazon/Solimões river) and at a large beach along the Rio Negro ("Praia Grande"). Phenology, habitats, and behavior were observed monthly at these sites. In addition, other places were visited sporadically. Adult beetles were regularly collected in the field and brought to the laboratory for examination of gonad maturity and flight muscle development. Further adults were needed to start laboratory cultures and for experiments. Larvae were also brought to the laboratory for rearing and experiments. Larvae were reared under controlled conditions in the laboratory to (a) elucidate the identity of unknown larvae, and (b) determine the duration of larval development (including the pupal phase). The maximum duration of inundation survived by larval field populations was determined in two species. Several laboratory experiments were performed to quantify submersion tolerance or resistance in larvae and adults of different species. This contribution summarizes the results of this study published hitherto. (1) The hitherto unknown larvae of five species/subspecies were identified by rearing larvae until the adult beetle. A key was provided which allows the determination of all species known to occur in Central Amazonian floodplains. (2) All species investigated showed univoltine life cycles driven by the flood pulse: - (a): Phaeoxantha klugii, P. lindemannae, P. aequinoctialis ssp. (and presumably also P. limata) had a long larval phase (appr. 7-12 months) and life span in adult beetles was relatively short (3-4 months) with the exception of P. a. bifasciata (>6 months). - (b) On the contrary, Tetracha sobrina punctata, Pentacomia cribrata, and presumably T. spinosa and Cylindera suturalis completed the larval phase within 3-4 months, without a phase of dormancy. As the adult beetles are known or presumed to survive the aquatic phase at 'dry' places, adult life span is expected to be at least 9 months. (3) Most species were stenotopic with regard to white- vs. blackwater floodplains, only one species (T. s. punctata) occurred in both floodplain types. The species P. limata was found at the blackwater site as well as at a non-flooded upland site. (4) The habitats of the species were described in detail, based on the regular field observations. Larvae of most species were confined to specific micro-habitats differing in sediment properties, vegetation structure and position along the flood gradient. (5) The intraspecific structure of black- and whitewater guilds ranged from partial overlap to almost complete segregation of larvae and adult beetles. This was due to seasonal and/or diel temporal segregation as well as different micro-habitats (spatial segregation). The interspecific structure of both guilds was characterized by strong segregation (= niche separation). In adult beetles this was related to different life cycles, diel activity patterns, and micro-habitats (seasonal, diel temporal, and spatial segregation). In larvae it was mainly due to different micro-habitats (spatial segregation). In adult beetles, species differed in prey spectrum as inferred from different mandible gapes (functional segregation). Possible causes and implications of these findings are discussed. (6) The following survival strategies were described: - (a): Phaeoxantha species survive the aquatic phase as larvae submerged in the soil. Thus, they exhibit a non-migratory survival strategy which implies a long larval phase, great resistance against submersion and, presumably, hypoxic conditions, and rapid gonad maturation. - (b): All other species complete their larval development within the terrestrial phase and survive the aquatic phase as adult beetles at 'dry' places. Thus, they show a migratory survival strategy which implies an obligatory habitat shift in adults, a shortened larval and a prolonged adult phase, and gonad dormancy during the aquatic phase. Both types of survival strategy are discussed and compared with other tiger beetles and carabid species in general. (7) Larvae of P. klugii und P. lindemannae which pass the aquatic phase in the soil survived 3-4 months of inundation in the field. However, laboratory experiments showed that active (i.e. non-dormant) larvae only survived a few days submerged in water. A similar low tolerance was also found in a species with adult beetles surviving the aquatic phase. Dormant larvae of P. klugii were somewhat more resistant. Larvae of the former two species that were gradually flooded from underneath within sediment in the laboratory (simulating field conditions) survived 3 months of inundation which is in agreement with the field observations. The gradualness of the flooding process apparently allows for or induces a physiological alteration which ensures the great submersion resistance. (8) The migratory survival strategy implies a habitat shift in adult beetles which is mostly possible by flight only. Accordingly, all dissected specimens of these species showed fully developed flight muscles. Species exhibiting non-migratory survival strategies do not need flight for surviving the aquatic phase. Correspondingly, only 0-60 % of the dissected specimens had flight muscles, varying from species to species