Male and female reproductive success in natural and anthropogenic populations of Malaxis monophyllos (L.) Sw. (Orchidaceae)

In the presented study, male and female reproductive success was analyzed in relation to the population size, floral display and pollinators’ availability in natural and anthropogenic populations of the orchid Malaxis monophyllos (L.) Sw. Our results indicated significant differences between all investigated populations in parameters of floral display, including heights and number of flowers per inflorescence, as well the number of flowering individuals and their spatial structure. Additionally, populations differed both in male (pollinia removal) and female (fruit set) reproductive success, but only the fruit set clearly differentiated anthropogenic and natural populations. Despite the average flower number per plant being significantly higher in two of the anthropogenic populations, it was not related to the fruits set, which was significantly lower there. Moreover, our preliminary study concerning the potential pollinators of M. monophyllos showed a higher contribution of flies in natural habitats than in anthropogenic ones. Thus, we can suspect that the main factors influencing the level of female reproductive success in M. monophyllos populations are abundance of effective pollinators, as well as flower visitors, which may have resulted in a different level of pollen discounting in populations. Therefore, further studies concerning breeding system and pollination as important forces that shape demographic processes in M. monophyllos populations are necessary. Our results also indicate that suitable conservation methods in M. monophyllos should always include the preservation of potential pollinators, especially in these new, secondary habitats

Pollinator limitation affects low reproductive success in populations of nectarless orchid in the Biebrza National Park

The deficiency of pollinators is indicated as the main factor limiting fruit set in orchids. Nectariferous species are more successful in setting fruits than nectarless species. In the present study, we tested whether pollinator limitation lowers reproductive success in populations of Cypripedium calceolus on environmental islands in the Biebrza National Park, NE Poland. Moreover, we analyzed how population size and structure affect pollination success. Our observations and results of experiments document the low level of fruiting in populations of nectarless C. calceolus (9.2% on average) and strong pollen limitation. Generally, we noted a positive relationship between pollination success and all parameters of population size (measured by both occupied area and number of clumps or shoots) and parameters measuring floral display (number of flowers in population, number of flowers in clumps, spatial structure of flowering shoots). We suggest that information about factors influencing the reproductive success of this endangered species may be useful for planning appropriate conservation actions

Breeding system variability, pollination biology, and reproductive success of rare Polemonium caeruleum L. in NE Poland

Polemonium caeruleum (Polemoniaceae) represents a very interesting system of compatibility transition. Studies of its biological and ecological properties in the context of the breeding system of various populations may help to understand the evolutionary mechanism of this process. We investigated some aspects of the breeding system, diversity and foraging behavior of the visitors, and relationship between population properties and fruit set in three populations from NE Poland. We found distinct compatibility systems in two studied populations and showed that if a population is self-compatible (SC), selfing is mediated by insects via geitonogamous pollen transfer. Despite the population properties (compatibility, visitor diversity and activity, population size, density, or floral display), P. caeruleum is not pollen limited and pollinators are highly important as a key factor determining the high reproductive success. Visitor assemblages (including key pollinators, bumblebees, and honey bees) and their foraging behavior on inflorescences vary between the populations, which may influence differences in the breeding system. The self-incompatible population was visited by a more diverse group of insects from Hymenoptera, Diptera, Lepidoptera, Heteroptera, and Coeloptera, which may favor effective cross-pollen transfer, whereas the SC population was pollinated mainly by Apis mellifera, which may promote mixed-mating. Studies on a wider range of P. caeruleum populations are needed to determine selective factors responsible for compatibility transition

Seed dispersal in six species of terrestrial orchids in Biebrza National Park (NE Poland)

Knowledge about seed dispersal is required to explain problems in ecology, phylogeography, and conservation biology. Even though seed dispersal is a fundamental mechanism to understand problems at different levels of biological organization (individual, population, species, landscape), it remains one of the least recognized processes. Similar to other groups of plants, very little is known regarding patterns and distances of seed dispersal in orchids. Orchid seeds are generally assumed to be widely dispersed by wind because of their small size and low weight. Between 2006 and 2008, we conducted a field study of the distances at which orchid seeds are dispersed, and determined factors affecting dispersal. Investigations included 13 populations of six terrestrial orchid species – Cypripedium calceolus, Cephalanthera rubra, Epipactis helleborine, Goodyera repens, Neottia ovata, and Platanthera bifolia. To evaluate seed dispersal in orchid populations, 8.5-cm Petri dishes (traps) with self-adhesive paper were placed along transects, starting from a group of fruiting plants, which were considered to be the dispersal source. Seeds of the investigated orchid species were dispersed over relatively short distances. There were statistically significant negative correlations between seed density and distance from the fruiting plants. Seeds of species with taller fruiting shoots were dispersed farther than those with shorter ones (R = 0.68, p < 0.05). We discuss the causes and consequences of the dispersal patterns of orchid seeds

Pollinator limitation affects low reproductive success in populations of nectarless orchid in the Biebrza National Park

The deficiency of pollinators is indicated as the main factor limiting fruit set in orchids. Nectariferous species are more successful in setting fruits than nectarless species. In the present study, we tested whether pollinator limitation lowers reproductive success in populations of Cypripedium calceolus on environmental islands in the Biebrza National Park, NE Poland. Moreover, we analyzed how population size and structure affect pollination success. Our observations and results of experiments document the low level of fruiting in populations of nectarless C. calceolus (9.2% on average) and strong pollen limitation. Generally, we noted a positive relationship between pollination success and all parameters of population size (measured by both occupied area and number of clumps or shoots) and parameters measuring floral display (number of flowers in population, number of flowers in clumps, spatial structure of flowering shoots). We suggest that information about factors influencing the reproductive success of this endangered species may be useful for planning appropriate conservation actions

Breeding system variability, pollination biology, and reproductive success of rare Polemonium caeruleum L. in NE Poland

Polemonium caeruleum (Polemoniaceae) represents a very interesting system of compatibility transition. Studies of its biological and ecological properties in the context of the breeding system of various populations may help to understand the evolutionary mechanism of this process. We investigated some aspects of the breeding system, diversity and foraging behavior of the visitors, and relationship between population properties and fruit set in three populations from NE Poland. We found distinct compatibility systems in two studied populations and showed that if a population is self-compatible (SC), selfing is mediated by insects via geitonogamous pollen transfer. Despite the population properties (compatibility, visitor diversity and activity, population size, density, or floral display), P. caeruleum is not pollen limited and pollinators are highly important as a key factor determining the high reproductive success. Visitor assemblages (including key pollinators, bumblebees, and honey bees) and their foraging behavior on inflorescences vary between the populations, which may influence differences in the breeding system. The self-incompatible population was visited by a more diverse group of insects from Hymenoptera, Diptera, Lepidoptera, Heteroptera, and Coeloptera, which may favor effective cross-pollen transfer, whereas the SC population was pollinated mainly by Apis mellifera, which may promote mixed-mating. Studies on a wider range of P. caeruleum populations are needed to determine selective factors responsible for compatibility transition