Breeding Systems in Prunus

Biological Journal of the Linnean Society, 50(1): 65-84 (Sept 1993)
Pollination biology of Prunus mahaleb L.: deferred consequences of gender variation for fecundity and seed size
Pedro Jordano

Abstract
This study describes the reproductive biology of Prunus mahaleb, a rosaceous treelet, in a southeastern Spanish population. The species is gynodioecious with 55.4% of the plants being male-fertile and 44.6% presenting non-functional, shrunken anthers with no pollen, and behaving as functional females. Individual trees produced the same flower morph in four consecutive study years. Fruit set in bagged inflorescences was absent in male-sterile trees and was very reduced in male-fertiles. Open-pollinated flowers of male-fertiles showed greater fruit set (x̄= 29.1%) than male-steriles (x̄= 25.3%). Average fruit set in three experimental treatments (control, selfed, and crossed) were 29.05%, 41.9% and 38.6%, respectively, for male-fertile trees; those for male-steriles were 25.3%, 0% and 39.2%, respectively. Seeds from male-sterile plants were heavier (71.33 mg) than those of male-fertile plants (66.05 mg) but did not differ in germination ability. Male-fertile and male-sterile trees differ significantly in average nectar concentration (73.5% and 55.9%, respectively) and nectar volume secreted/flower and day (0.142 μl and 0.171 μl, respectively). A total of 41 species of insect flower visitors were recorded. Calliphorid and tachinid flies (41.97% of total visits), and andrenid bees (30.30%), were the most frequent visitors. The diversity of insect visitors was greater in male-fertile trees. Bees and flies accounted for 50.5% and 49.5%, respectively of total visits to male-fertile trees. Flies were far more frequent than bees at male-sterile flowers (76.9% and 23.1%, respectively). Male-sterile trees received higher average visitation (47 insects/census) than male-fertile trees (32 insects/census). Individual trees. showed a relative constancy of the fecundity rankings between years. Fruit production was significantly higher in male-sterile trees, with a four-year average of 6558 fruits, in contrast with male-fertile trees which yielded 4670 fruits. This 1.77-fold difference in favour of male-sterile trees over malefertiles was not compensated by the greater fruit set of the latter. This is attributable to the lower outcrossing rate of male-fertiles, estimated as 52.68% from seed mass data. In addition, greater seed mass of female progeny, and higher visitation rate by insects might explain the maintenance of this polymorphism. These results have far-reaching implications for the demography and seed-dispersal ecology of this endozoochorus species.

Mol Ecol. 14(6): 1821-30. (May 2005)
Mating patterns, pollen dispersal, and the ecological maternal neighbourhood in a Prunus mahaleb L. population.
García C1, Arroyo JM, Godoy JA, Jordano P.

Abstract
Gender polymorphism, plant-animal interactions, and environmental heterogeneity are the three important sources of variation in mating system and pollen dispersal patterns. We used progeny arrays and paternity analysis to assess the effects of gender type and density level on variation in mating patterns within a highly isolated population of Prunus mahaleb, a gynodioecious species. All the adult trees in the population were sampled and located. The direct estimate of long-distance insect-mediated pollination events was low (< 10%). Gender expression deeply influenced the mating system, decreasing the outcrossing rates (t(m)) and the pollen pool diversity in hermaphrodite trees. Long intermate distances (> 250 m) were significantly more frequent among female mother trees. Variation in local tree density also affected pollen pool diversity and intermate distance, with a higher effective number of fathers (k(e)) and longer intermate distances for female trees in low-density patches. A canonical correlation analysis showed significant correlations between mating variables and the maternal ecological neighbourhood. Only the first canonical variable was significant and explained 78% of variation. Outcrossing rates tended to decrease, and the relatedness among the fathers tended to increase, when mother trees grew in dense patches with high cover of other woody species and taller vegetation away from the pine forest edge. We highlight the relevance of considering maternal ecological neighbourhood effects on mating system and gene flow studies as maternal trees act simultaneously as receptors of pollen and as sources of the seeds to be dispersed.

Botany, 95(9): 913-922 (2017)
Sex morphs and invasiveness of a fleshy-fruited tree in natural grasslands from Argentina
M.R. Amodeo, S.M. Zalba

Abstract
Invasiveness has usually been studied as a species-level attribute; nevertheless, phenotypic differences between individuals in a population can lead to significant variations in colonization ability. In this paper, we analyse the potential effects of sex morphs of Prunus mahaleb L., a gynodioecius fleshy-fruited tree, on its invasiveness in natural grasslands in the southern Argentine Pampas. We assessed the abundance of both hermaphrodite and female plants, and compared their fecundity, propagule size, and germination response. We found that the females were less abundant in the invasive populations studied, apparently since the beginning of the colonization. However, our results demonstrated that at the present time, females do not show any fecundity reduction, which clearly shows that P. mahaleb has established an effective interaction with generalist pollinators that compensates for the apparently disadvantaged females. Fruit set showed a wider range of variability over time in the females than in the hermaphrodites, which could be the consequence of greater susceptibility to changes in the activity of pollinators. We found no evidence of a female benefit due to reallocation of resources or better outcrossed progeny when considering propagule size and germination. We discuss the relative importance of sex morphs and interactions at different stages of the invasion process.

Vermont Agricultural Experiment Station, Bulletin 53 (Dec 1898)
Pollination in Plums
F. A. Waugh

Sexual Affinities of Prunus americana (1895)
CLASSIFICATION OF THE SEXUAL AFFINITIES OF PRUNUS AMERICANA VAR.*
C. W. H. Heideman

CONCLUSIONS
Self-sterility of Prunus Americana in the heterostyled and bisexual forms is caused by the great differentiations of the sexual elements. Pollination by wind and insects cannot be controlled to any extent. Mixed planting, therefore, unless it be done with respect to the natural affinities of the varieties, may produce the most disastrous result for the horticulturist. Other species of Prunus observed show these characteristics of P. Americana, and it may be possible to bring them together and under a similar classification. Finally we have gained some knowledge in the summary production of hybrids. This study is necessarily preliminary to further investigation touching horticultural varieties of P. Americana, etc.

Wikipedia: Prunus geniculata

The species is andromonoecious, with individuals bearing both bisexual and male-only flowers.

Transactions of the Linnean Society of London: Botany. Second ser, 1: 338 (1875)
On the self-fertilization of plants
Rev. Henslow

Lastly, Prunus spinosa and Padus, as well as Crataegus oxycantha, are proterogynous.