A glimpse of the tropics – spiders ( Araneae ) in the greenhouses of the Botanic Garden Berlin-Dahlem

In a survey of the spider fauna in greenhouses of the Botanic Garden Berlin-Dahlem, 30 spider species were recorded. Two species are new to Europe: Theotima minutissima (Petrunkevitch, 1929) and Heteroonops spinimanus (Simon, 1891). T. minutissima is the first member of the family Ochyroceratidae reported from Europe. Oecobius navus Blackwall, 1859 is new to Central Europe. Triaeris stenaspis Simon, 1891, is recorded from Germany for the first time. Zodarion italicum (Canestrini, 1868) is new to eastern Germany. Despite the discovery of some species previously unknown to Germany, the spider fauna in the Botanic Garden consisted mainly of wellknown synanthropic species and common inhabitants of greenhouses. Several alien spiders recently found in greenhouses, garden centers and houses were not recorded in the Botanic Garden. The species composition of the exotic spider fauna in greenhouses seems to depend chiefly on the specific modes of acquisition of plants and plant substrate.

The spider fauna of botanic gardens and greenhouses has attracted several researchers, starting with Simon (1896) and followed by PlCKARD-Cambridge (1906), Van der Hammen (1949a), HOLZAPEEL (1932) and others. BOETTGER (1929) was the first to investigate the invertebrate fauna of the greenhouses of the Botanic Garden in Berlin-Dahlem (Germany). His main interest focused on molluscs. Nevertheless, he caught several exotic spiders new to Germany. The next survey of the fauna in the Dahlem greenhouses was conducted by W. Eichler between 1936and 1938(EiCHLER 1952 In the last days of World War II, the greenhouses were severely damaged. Today, global trade and climate change facilitate the importation and invasion of exotic spiders to Europe (JÄGER 2005, KOBELT &c NENTWIG 2008. The number of established alien species is expected to rise. Therefore, a new survey of the spider fauna in the greenhouses of the Botanic Garden Berlin-Dahlem was conducted to compare the results with the data of BOETTGER (1929) and Eichler (1952). In 2008, spiders in the greenhouses were collected by hand (including beating of plants and litter sieving) as well as by pitfall traps. Sampling was done as the opportunity presented itself and did not follow a fixed regime.
Most of the native spiders belonged to this group.
Five species were confined to the hothouses. In the wild, these spiders live in subtropical or tropical climates and, in one case, in Mediterranean climate conditions.
Compared to the results of BOETTGER (1929) and EICHLER (1952), 10 species recorded previously were not found in the current study (Tab. 1). Only five species were found in all studies: P tepidariorum, Ara?ieus diadematus, Zygiella x-notata, Tegenaria atrica, and the jumping spider Hasarius adansoni. Tegenaria domestica was caught only in the study of BOETTGER (1929). According to KOMPOSCH (2002), this funnel-web spider has been common in urban habitats in the 19'^c entury, but is now rare. It could have been displaced by T. atrica. Another intriguing species is Nesticus cellulanus. In Berlin-Dahlem, it was found only in the 1920"s.
Holzapfel (1932) reported it to be a frequent inhabitant of hothouses in the Botanic Garden of Bern (Switzerland) at the same time. P phalangioides is known to displace other spider species (KOMPOSCH 2002) and might be responsible for the decline of N. cellulanus in the greenhouses.
Two exotic spiders reported by BOETTGER (1929)  The whereabouts of the material from the study of EICHLER (1952) are unclear. The apparent absence of small spider species in the preceding studies of the fauna in the Dahlem greenhouses may have been due to low sampling effort. EICHLER (1952: 63) did not try to identify the small spiders, whose webs he often found on the underside of leaves with mealybugs. HOLZAPFEL (1932) apparently paid more attention to smaller spiders. She recorded several species belonging to the Linyphiidae and Dictynidae as well as an unidentified oonopid spider in Bern.
Five species recorded in the present study are particularly remarkable. Detailed information on these spiders is given below.
Theotima minutissima (Petrunkevitch, 1929) Diagnosis: This is a very small six-eyed spider (< 1 mm). The carapace shows a pattern of dark and light brown streaks. Four eyes form a straight transverse row with the two remaining eyes behind them.
The females have no externally chitinized epigyne. The genital opening does not extend laterally on the abdomen as is the case in many species of the fam- While the other members of the genus are confined to tropical and subtropical America or Africa, T. minutissima is a pantropical species (DEELEMAN-REINHOLD 1995). This is the first record of a member of the family Ochyroceratidae (midget ground weavers) in Europe and the first record of T minutissima from a greenhouse.
Theotima minutissima builds irregular webs in the ground litter. It was placed in a guild of "nocturnal ground weavers" by HÖFER 8c BRESCOVIT (2001). HÖFER (1990,1997) reported it as one of the dominant species in several inundation forests in Brazil, constituting up to 35% of the total catch in pitfall traps. The spiders ascended tree trunks to avoid inundation. The species was not present in a terra firma forest (HÖFER 1997). In a wet subtropical forest in Puerto Rico, T minutissima reached a density of about 60 individuals m^of the litter layer (EDWARDS Sc EDWARDS 2006). It showed a slight preference for wetter litter with more decayed material in the forest.
The females lay 4-6 eggs and carry them in their chelicerae until the spiderlings are fully developed.

Heteroonops spinimanus is widespread in Central
America and the southern United States (CHICK-ERING 1973). It has been introduced to St. Helena and the Seychelles. The male of H. spinimanus is unknown (CHICKERING 1973), and the species is believed to be parthenogenetic (SAARISTO 2001 Van HeLSDINGEN 1999). Records in Belgium date back to 1985 ( VAN Keer 2007). In Estonia it was recorded for the first time in 1974 (ViLBASTE 1974) and occurred shortly afterwards in Latvia (Sternbergs 1980 (Santos 6c Gonzaga 2003, Voss et al. 2007), but have also been found under rocks in coastal areas (GlATZ 1967) or bush land and in caves. In northern Europe and Japan, they live in the interior of buildings (MiYASHITA 1992, VAN KEER 2007, ViLBASTE 1974. Van Keer (2007) doubted the ability of 0. navus to live outside of buildings in Belgium. Contrary to this, STERNBERGS (1980) reported that the spider lives in crevices of tree bark in Latvia. It was found there even after a hard winter. According to GlATZ (1967) (Van Keer et al. 2006). In Germany it has been caught mainly in the south-west (STAUDT 2008 A good example to this is Uloborus plumipes Lucas, 1846. In 1989, the species was recorded for the first time in Germany (KÜMHOF et al. 1992). Today it can be found in greenhouses, garden centers and flower shops all over the country. In Berlin, the species was caught in a butterfly house in 1995 (BROEN &RUDLOFF 1996) and is now ubiquitous.
It is a conspicuous spider, and easily spotted due to its typical resting posture in the web. Nevertheless, I never encountered it in the Dahlem greenhouses.
Unlike other institutions, the Botanic Garden does not normally buy plants from commercial suppliers. Plant material is collected during field trips or acquired through exchange with other botanic gardens. Thus, the species composition of the exotic spider fauna in greenhouses seems to depend chiefly on the specific modes for acquisition of plants and plant substrate.
A common feature of the ochyroceratid and oonopid spiders found in the Botanic garden is the parthenogenetic reproduction. Parthenogenesis seems to be advantageous for colonization. Introduction of a single female of the species is sufficient to establish a population. These tiny spiders showed a heterogeneous, patchy distribution in the greenhouses. When they occur in low numbers, they are hard to find. In Berlin Dahlem, they were probably not recent immigrants, but had been overlooked in other studies. Most likely they can be found in other German greenhouses as weU, at least the most common species T. stenaspis.