The reproductive biology and taxonomy of the 'myrtaceae' of the Distrito Federal (Brazil)

Recent phytosociological studies in the Distrito Federal have shown that the Myrtaceae are the third ecologically most important family in the woody stratum of local savanna woodland, and that they may also be an important component in forests. The family, with c. 65 species in the area, is also the fifth in total number of species in the Distrito Federal. The taxonomic treatment includes a key to the genera and monographs of Subtribes Eugeniinae and Myrtinae (which account for 39 of the species). The Eugeniinae are represented by genera Eugenia (15 species), Myrciaria (2 species) and Siphoneugena (1 species). The Myrtinae are represented by genera Blepharocalyx (1 species), Campomanesia (6 species), Pimenta (1 species) and Psidium (13 species). The biological and historical factors which create difficulties in the taxonomy of the family are outlined. Approximately 800 Distrito Federal numbers of Myrtaceae were examined, and an additional 500 numbers of extra-Distrito Federal material of the same species. Most of the examined material came from the local IBGE, HEPH and UB Herbaria, but E and K were also visited personally and had their collections surveyed; the following Herbaria sent material (mostly types) on request: BR, EG, G, M, S, U, UEC, US. Data was stored and manipulated using the Hypertaxonomy software designed by Dr. Flemming Skov for systematic studies in Botany; this runs on the HyperCard application of the Apple Macintosh. Keys to flowering, sterile and fruiting material are provided and many new synonyms are proposed, some of which are tentative and must await consultation of type material. The distribution of the species showed that many had their northerly limit in the Distrito Federal region. The climate, which is the coolest in Brazil at this latitude, and has a reasonable amount of rainfall, may be responsible (allied to very poor soils), and the various isohyets and isotherms which underpin these distribution patterns were mapped for Brazil. A review of the reproductive biology of the family is presented, which highlights the limited data available for the family in the Neotropics. Eight species were studied from the point of view of flowering phenology, floral and pollination biology, breeding system and success of fruit-set. These were chosen with the purpose of giving an overview, both taxonomically and ecologically: Eugenia dysenterica, a savanna tree, Siphoneugena densiflora, a tall savanna woodland to gallery forest tree, Blepharocalyx salicifolius, a tall savanna woodland tree, Campomanesia puhescens, a savanna shrub, Campomanesia velutina, a gallery forest tree, and Myrcia linearifolia, Myrcia rhodosepala and Psidium firmum, all rather open savanna shrubs. Results showed that all species were bee-pollinated and offered pollen as the floral reward, that flowers opened very early in the morning and lasted a day and that flowering strategies were 'steady state' 'big-bang' and 'cornucopia' as defined in classical studies by Alwyn Gentry. Buzz-pollination was registered in S. densiflora. B. salicifolius and M. rhodosepala, although anthers were non-poricidal, an unexpected finding with implications in the evolution of the Melastomataceae, one of the closest families to Myrtaceae, in which buzz-pollination allied to poricidal anthers is fixed. Pollinator-sharing by Bombus spp. bees occurred in the five savanna shrubs, C. pubescens, M. linearifolia, M. rhodosepala and P. firmum. The two trees which occur in gallery forest, C. velutina and S. densiflora, are both self-incompatible, as well as B. salicifolius, which is one of the largest trees of dystrophic tall savanna woodland. The five other species, all shrubby except for E. dysenterica, have diverse degrees of self-compatibility although fruit-set was consistently higher after cross-pollination than after self-pollination. If pre-emergent reproductive success (PERS) is accepted as a dependable parameter to evaluate breeding system, all species are predominantly outcrossing. Precise synchronization of flowering, environmentally cued by the abrupt fluctuations in humidity of the air which occur at the dry season/rainy season transition, may be one of the factors promoting outcrossing in self-compatible species such as C. pubescens and E. dysenterica