Pilzmückenblumen als Pilzmimeten

Summary of part I and II

Observations covering a period of several years have shown that Asarum caudatum is regularly pollinated by fungus gnats. Thereby attention was directed to certain appendages resembling mushrooms or parts thereof, occurring on perianths, axes, or bracts of ecologically related flowers.

A hypothesis is being put forward that these appendages are dummies for deceptive attraction of fungivorous Diptera such as Mycetophilids, Sciarids, etc., to ensure cross pollination by these insects.

In Asarum spp. as well as in the Aroids Arisarum proboscideum and Arisaema utile, this function has been substantiated by direct proof. By analogy, or from observations of related, non-mimetic species, the visit of fungus gnats is equally predicted for Aristolochia arborea, species of the Orchid genera Masdevallia (sect. Chimaeroideae), Cypripedium and Corybas, the section Trisecta of Arisaema, and Arachnitis uniflora, member of Corsiaceae, all of them mimicking fungus parts, too.

The fungus mimetes - as fungus gnat flowers, in general, a hitherto undescribed subclass of the myiophilous style - are dwellers of the dark forest floor, with blossoms close to the bottom (geophily), of dark purple brown hues as a rule and white or translucent patterns, of seeming scentlessness or mushroom-like and musky odors, and intensive local transpiration of the fungus-like parts. They are urn-shaped or kettle-traps of a simple type.

The fungus gnats whose relation to mushrooms is discussed regarding its parasitic ultilization by the deception flowers, approach the latter on account of their breeding instincts. Misled by their releasing system involving olfactory, light, tactile and humidity perception, the midges lay their eggs (or try to do so) into the lamella or pore imitations and thus they pollinate the flower. Eggs and larvae, incapable of eating the flower tissue, die before anthesis is finished. Mating males of the gnats also contribute to pollination.

Counts of the eggs and larvae in Asarum caudatum flowers resulted in visit rates up to 76 % of the flowers in cultivation and up to 35 % in natural surroundings. Infected flowers contained 4 eggs on the average. Mostly not more than one egg is laid per oviposition. Fungus gnat visits in Asarum caudatum continue during the first five days, fade then, and finish completely, after anthesis - of 9—12 days total duration — has come to an end. Allogamy by the help of fungus gnats is presumed to be a general feature of Asarum (incl. Heterotropa), a genus in which fungus-like structures occur in 8 of its sections