Aradus serbicus Horvath 1888

Aradus serbicus (Horváth, 1888) (Aradidae)

Material: Germany, Hesse, Kellerwald-Edersee National Park, 425 m a.s.l., on Fagus sylvatica, 27.v. – 24. vi.2008, 1 Ψ, U. Schaffrath leg., C. Morkel det. (Fig. 2)

The distribution area of the extremely rare A. serbicus known so far, ranges from southern France and Italy to Greece, including Austria and the Balkan peninsula with the countries Croatia, Serbia, Hungary, Bulgaria, and Macedonia (Heiss & Péricart 2007). Among the associated trees, chiefly Fagus sp. is documented; however, also Quercus sp. in combination with Fagus from records from Greece, are mentioned (Heiss 2006, Heiss & Péricart 2007).

The current extralimital record of A. serbicus was obtained from a pitfall trap exposed in a living beech tree (Fig. 3) split by lightning several decades ago, containing a large rot-hole as well as specific fungi infestation, including Oudemansiella mucida (Schrad. ex Fr.), a species characteristic of old beech forests. The associated coleopterous fauna contained several species (Schaffrath, pers. comm. 2010) classified as primeval forest relict species according to Müller et al. (2005). The habitat itself, located on a steep slope, represents one of the small patches of virgin forest within Kellerwald-Edersee National Park showing a very long continuity concerning dead wood quality and quantity due to the impossibility of forestry.

The vast majority of palaearctic Aradidae are known to be dendrobiont and mycetophagous, relying more or less specifically on wood- and tree-infesting fungi (Heiss & Pericart 2007). For some of the most rarely found species within Central Europe, a temporal continuity of several centuries in the occurrence of dead wood structures of various decomposition stages (‘habitat tradition’) necessary for the colonisation by particular fungi species (Goßner et al. 2007) is hypothesized to be essential.

Judging from the circumstances of finding of the recent record as well as published data (Heiss 2006), A. serbicus is considered to feed on a specific range of wood-dwelling fungi limited to broad-leafed trees or even exclusively to Fagus sylvatica. Moreover, the recent record strongly indicates a long habitat tradition to have been critical for the occurrence of A. serbicus.

Thus, considering the extralimital documentation of A. serbicus in combination with the habitat conditions described, and the only 17 localities recorded so far (with the correct determination of A. serbicus for ten of them confirmed by Heiss & Péricart 2007), the species is considered to represent a primeval forest relict in the closest sense (see Müller et al. 2005) within Central Europe.

Records of the closely related Aradus truncatus Fieber, 1860 of European distribution are confirmed mainly from southern Europe by Heiss & Péricart (2007); those from remaining countries, especially Germany, Poland, Denmark, Sweden, and Finland, should be verified in order to clarify if some of them represent A. serbicus, and if the occurrence of A. serbicus corresponds with the distribution area of Fagus sylvatica.

Further investigations concerning the biology of A. serbicus should be conducted, in order to support the hypothesis regarding the species´habitat preferences and to obtain data on its host fungi..