Self-fertilization may have evolved in the peripheral population at the highest site of V. caracalla because of the benefits of reproductive assurance under reduced pollinator diversity.

The pollen:ovule ratio (P/O) has traditionally been used as a rough estimator of plant breeding systems. It has been shown that plant breeding systems are associated with particular floral traits. In this study, we determined the P/O in 21 Leguminosae species from Argentina and explored relationships between P/O and taxonomic position, flower size, floral rewards, pollen presentation and pollination mechanisms. According to the results, 15 out of the 21 species classified were obligate xenogamous, although some of them have been recorded as facultative xenogamous in previous studies. There was a significant effect of taxonomic position (genus), reward type and pollination mechanism on P/O. Species offering only nectar as a floral reward (which were species with a brush mechanism) had a significantly lower P/O than species offering pollen or pollen and nectar. Species with the brush pollination mechanism had the lowest P/O, while species with valvular and pump mechanism had the highest P/O. However, pollen presentation (primary and secondary) and flower size did not have a significant effect on P/O. Our results demonstrate that P/O variability is determined by taxonomic position and pollination mechanism in this plant group.

No abstract

Plants in the genus Erythrina are pollinated by birds, such that passerine pollination is the plesiomorphic state, whereas hummingbird pollination is the derived character. Phylogenetic studies suggest that Erythrina dominguezii belongs to a basal clade characterised as pollinated by both passerines and hummingbirds. Here, we characterise the pollination system of E. dominguezii. Floral morphology, nectar traits, breeding system, visitation rates and pollen deposition by its floral visitors were studied. Floral morphology of E. dominguezii showed traits associated with both passerine and hummingbird pollination. Nectar sugar concentration showed an intermediate value but closer to the hummingbird type; however, it was rich in hexose, which is typical of the passerine type. Approximately 5% of the flowers set fruits under free pollination. Almost 80% of recorded flowers were visited by birds, with the rest visited by hymenopterans (bumblebees and honeybees). Among avian pollinators, five species of hummingbirds and three passerine species were identified as pollinators. The hummingbird Chlorostilbon lucidus was the most efficient visitor in terms of pollen deposition and was second in frequency of visits. The passerine Icterus cayanensis was second in efficiency at depositing pollen and was the most frequent pollinator. Our results show that E. dominguezii has a generalised pollination system. In addition, we report a new case of closed flowers and secondary nectar presentation. This is the first study that compares effectiveness among different pollinators in Erythrina.

Reproductive aspects of Schinus areira (Anacardiaceae). Schinus areira is a naturalized tree in northwestern and western Argentina, and extensively cultivated in the country. Our goals were (1) to determine the floral and reproductive biology of S. areira, (2) to compare different pregerminative treatments, and (3) to analyze the morphology of the seedlings during the development for their correct taxonomical identification. Analyses of floral biology and reproductive system, fruit and seed morphology, and different pregerminative treatments were carried out. Seedlings development was recorded at 90, 180, and 270 days. As a result, it was found that the fruit/flower ratio was low, and the pollen/ovules ratio was very high. On the other hand, pregerminative treatments gave very low results that agree with fruit morphology. Seedlings had a normal growth reaching an average of 43 cm height at 270 days, and they developed simple basal leaves with a compuond leaves from approximatelly 180 days. We proposed that the species is dioecious and polygamomonoecious, mainly gynomonoecious, the pollination is ambophyly with predominance of entomophyly, and the seedlings development is phanerocotyledonar epigeous.Resumen: Schinus areira es un árbol naturalizado en el noroeste y oeste de Argentina y extensamente cultivado en el país. Nuestros objetivos fueron (1) determinar la biología floral y reproductiva de S. areira, (2) comparar diferentes tratamientos pregerminativos para la especie y (3) analizar la morfología de las plántulas durante el desarrollo para su correcta identificación taxonómica. Se realizaron análisis de biología floral y del sistema reproductivo, de morfología del fruto y semilla, y diferentes tratamientos pregerminativos. Se registró el desarrollo de plántulas a los 90, 180 y 270 días. Como resultado se obtuvo que la proporción frutos/flores fue baja, y la proporción polen/óvulo muy alta. Por otro lado, los tratamientos pregerminativos dieron resultados muy bajos lo cual concuerda con la morfología del fruto. Las plántulas tuvieron un crecimiento normal alcanzando un promedio de 43 cm de altura a los 270 días, y desarrollaron hojas basales simples con hojas compuestas a partir aproximadamente de los 180 días. Se propone que la especie es dioica y polígamo-monoica, mayormente ginomonoica, la polinización es ambófila con predominio de entomofilia, y el desarrollo de las plántulas fanerocotiledonar epígeo.Palabras clave: Morfología del fruto, plántula, sistema reproductivo, tratamiento pregerminativo.