prilagođeno pretraživanje po punom tekstu

ŠUMARSKI LIST 11-12/2016 str. 20     <-- 20 -->        PDF

The interactions of organisms associated with Scolytinae are sometimes even more complex than being strictly based on phoresy or parasitism. In case when fungal spores are regularly carried by mites, as it concerns for example Ophiostoma sp. and some Tarsonemus species, the term hyperphoresy is commonly used (e.g. Wirth & Pernek 2012). Fungus spores, which are carried by phoretic mites into bark beetle galleries can influence the microclimatic conditions inside these micro habitats (Wirth & Pernek 2012). The authors of this research documented the case of Histiostoma sp. (Histiostomatidae), which was conspicuously covered by fungal spores of the Ascomycota.
It is important also for applied reasons to record phoretic mites on bark beetles as they can negatively influence the reproductivity of the beetles due to imported fungus spores or due to their life styles (e.g. Moser 1975).
Aim of this work was the recording of mite taxa being phoretically associated with Ips cembrae and Ips typographus Linnaeus, 1758 in Croatia. I. cembrae is a secondary pest of the European larch, Larix decidua Miller 1754 the species is also exceptionally able to colonize also spruce, Picea abies(L.) Karst Its impact is less harmful than the key pest I. typographus. These beetles are considered sister species by some authors (Stauffer, 1997)
Locations of collections – Mjesta sakupljanja
The sampling period was May 2012. Total numbers of collected mites are presented in Table 2. All sampling sites were located in Central Croatia and were characterized by a continental climate in the early summer season. Collectors were the authors themselves. Trees where the samplings were performed were usually still alive and characterized by yellow or reddish crones. All sampling areas were dense forests.
The key to determine juvenile stages of Histiostoma is based on studies performed at the Tyumen State University (Russia, 2015/ 16).
Sampling locations are shown in Fig. 1 with detailed description below:
– Nova Gradiška Ips typographus from Picea abies. 45°11´11˝S, 17°51´53˝I
– Koprivnica Ips cembrae from Larix decidua. 46°08´13˝S, 16°40´29˝I
– Gospić Ips typographus from Picea abies and Pinus sylvestris. 44°50´04˝S, 15°14´49˝I
– Jastrebarsko (Volavje) Ips typographus from five freshly felled tree trunks of Picea abies, stacked on each other for forestry utilization and being not yet decorticated, all beetle stages available in great numbers. 45°39´55˝S, 156°36´04˝I
Sampling – Sakupljanje uzoraka
The bark of dead and still living trees was peeled of using a cleaver and a chisel. The collected pieces of bark with adult beetles, pupae and larvae were put into plastic bags (60 liters) for transport and to avoid dehydration. Additionally, single beetles and their larvae were individually collected out of their galleries, using a spring steel tweezer and were transferred into small plastic dishes (volumina 250 ml and 125 ml). Original substrate (bark pieces and bore dust) was added.
At the sampling location Koprivnica, additionally to the usual sampling methods, three blocks were cut off a still living spruce tree trunk (height 40 cm, 50 cm in diameter). For this purpose, that almost dying tree was felled using a chainsaw and a cleaver. The blocks were finally cut off at a level between 3-5 m.
Preparation of Samples – Priprema uzoraka
Moist pulp paper was placed to the bottom of the dishes to guarantee permanent moisture. These dishes were used to keep beetles inside their original substrates alive. The same dishes were later used as cultivation wells for mites from these original substrates.
The wood blocks from Koprivnica were stored inside metal cages with a fine grid on all four sides to avoid an escape of newly hatched beetles. The cages remained in a climate chamber under controlled constant conditions (21 °C, 16/8 day-night-rhythm). The spruce blocks were sprinkled with water once every two days. In the same rhythm young beetles, which hatched out of the bark, were collected and examined for phoretic mites. Phoretic mite numbers on these young Ips cembrae beetles, which hatched out of the blocks and those from old beetles, which had been collected out of their galleries at the sampling site, were later compared with each other. Numbers