Androdioce

Androdioceus is a form of gender distribution in flowering plants . It is a mixed form of diocyte and monocyte : there are male plants and hermaphrodite plants in a population .

Androdioce is a rather rare phenomenon. Theoretically, it offers few advantages, since all female plants are also male and therefore not protected from self-fertilization . Male plants can only introduce their genes into the gene pool through pollination or vegetative reproduction; they lack female fitness. Only under conditions of pollen deficiency is the presence of excess men an advantage. This is the case with wind-pollinated species when the purely male individuals produce significantly more pollen than the hermaphrodites.

The first clear evidence of androdioceus was only published in 1990. One of the most famous examples is Datisca glomerata ( Datiscaceae ), whose closest relative is the diocese Datisca cannabina . In D. glomerata , the hermaphroditism is determined by two coupled dominant alleles , male individuals are double recessive homozygous . The species developed from the diocese sister species or common diocese ancestor. Male plants of this wind-pollinating species produce three times as much pollen as hermaphrodites. In hermaphrodites, self-fertilization leads to inbreeding depression . The outcrossing rate , i.e. the proportion of cross-pollination, is over 60%.

The second clearly confirmed case is the saxifrage Saxifraga cernua . This widespread species reproduces mainly apomictically through inflorescence bulbils . Many populations do not flower at all. In Abisko , northern Sweden , however, there are Androdioecan populations, with the male plants predominating. In some subpopulations there are no hermaphrodites at all. Male plants produce more bulbils than hermaphroditic plants. Hermaphrodites are also completely self-sterile. Androdioce does not lead to increased outcrossing here. Rather, the predominantly asexually reproducing male individuals have the advantage of not having to form female structures, but they can still reproduce sexually through pollen transfer.

Androdioceus has been reported from some tropical fruit trees, such as Nephelium lappaceum . These and other species with hermaphrodite flowers are probably functionally dioecious, since the pollen of the hermaphrodite flowers is often sterile. This has also been shown for nine Australian nightshade species, which are morphologically androdiocial, but functionally dioecious.

Otherwise, androdioecia probably only occurs due to cytogenetic coincidences, for example in some populations of Mercurialis annua , or due to pathogen infestation, as in Silene dioica .

supporting documents

• AJ Richards: Plant Breeding Systems . Chapman & Hall, London 1997, pp. 332-334. ISBN 0-412-57440-3 .