Tribe Miconieae Research Articles

Floral indumentum of Miconia: in search of diagnostic characters for the tribe Miconieae

The tribe Miconieae was composed of a few genera, such as Miconia, Clidemia, Leandra, and Ossaea, but recent works have recognized Miconia as the only genus of the tribe. The morphological diversity of trichomes in Melastomataceae have been employed for systematic purposes, especially the foliar indumentum. In the present paper, hypanthium trichomes of 24 species of Miconieae were investigated, 8 species of Miconia sensu stricto and 16 species of Leandra, as a contribution to the taxonomy of the tribe. Samples were obtained from herbarium and plant specimens collected in a state park in Paraná, Brazil. The hypanthium indumentum of the samples was analyzed using a scanning electron microscope. Our results revealed that long-peduncle stellate trichomes appear only within Miconias.s., while dendritic eglandular trichomes and glandular trichomes appear only in Leandra. Mixed trichomes with a lateral gland are less frequent and were found in both genera. It is not surprising, therefore, that the hypanthia of the investigated species possess indumentum of potential taxonomic significance. The characters of the indumentum of Miconia s.s., and Leandra may be useful in the infrageneric taxonomy of the new proposal for the tribe Miconieae.

Biogeography and diversification of the Caribbean clade of Miconia (Melastomataceae): a Cuban origin underlies one of the largest Antillean radiations

Abstract The Greater Antilles are renowned as a biodiversity hotspot and known to be geologically complex, which has led, in part, to the generation of organismal diversity in this area. One of the most species-rich montane groups within the Greater Antilles is the tribe Miconieae (Miconia s.l.) of the Melastomataceae, with ca. 325 species found there. The most diverse clade of Miconia in the Caribbean, the Caribbean clade, composes roughly half of that diversity, with an estimated 160 species, nearly all of which are endemic to the Greater Antilles. It is unclear how that diversity has been generated through time or where it originated, but we now have sufficiently well-sampled and robust datasets to test these patterns. Using a custom-built plastome dataset, we generated a robust phylogenetic hypothesis for 106 of the 160 Caribbean clade members and tested biogeographical patterns among the islands. Our results suggest that the Caribbean clade originated in the mid-Miocene, probably from a South American ancestor, and diversified substantially on the island of Cuba before repeatedly dispersing across other parts of the Greater Antilles, especially into nearby Hispaniola and then, to a lesser extent, into Jamaica, Puerto Rico and, finally, into the Lesser Antilles.

Limited dispersal ability and restricted niche characterize “depauperons” in Melastomataceae

The asymmetric pattern in species richness is a notable feature across different lineages and geographic regions. While some lineages have high richness, diversity and wide distribution, others have the opposite. Despite low rates of diversification, the latter might also be phylogenetically isolated. Lineages that accumulate these characteristics are known as “depauperons'' and explaining their existence and persistence through time is still a challenge. The plant family Melastomataceae contains both megadiverse lineages (such as the tribe Miconieae, with around 1900 species) and groups with few species (such as the tribes Eriocnemeae, Lithobieae, and Rupestreeae with 7, 1 and 2 species, respectively). These three clades are restricted to eastern Brazil, where they have been seldom studied. The lack of information about their basic biology as well as which processes determine their distribution have not been previously studied. Here we integrated metrics of dispersal ability, species distribution models (SDMs) and natural history data compilation in order to uncover common patterns shared by these depauperons in Melastomataceae and raise conservation concerns. For all nine species we estimated the dispersal ability and generated SDMs in different time-periods (past, present and future). Dispersal ability was associated with predicted distribution models under future scenarios to evaluate shifts and/or retractions in suitable areas. In addition, we compared the climatic tolerances of the depauperons with their megadiverse sister tribes via climatic envelopes. Overall, our results indicate limited dispersal ability, dependency on water for dispersal, and restricted niche as common characteristics for all species in the deupauperon tribes Eriocnemeae, Lithobieae and Rupestreeae. Our analyses also show that the climatic niche spaces of the depauperons are limited and totally included within the niche space of its sister tribes. Based on our findings, the level of threat in these groups can be potentiated by rapid climate change, mainly due to their inability to spread over long distances, restricted niches and increased habitat fragmentation. We suggest that future conservational actions prioritize these unique taxa in Melastomataceae, especially if a phylogenetic diversity perspective is taken into account.

Recognition of Miconia sect. Sagraeoides (Melastomataceae: Miconieae) and associated nomenclatural changes

Recent phylogenetic studies incorporating DNA sequence data have corroborated the suspected non-monophyly of many currently recognized genera of tribe Miconieae (Melastomataceae), which includes about 1800 species restricted to the Neotropics. The genus Mecranium, comprising 24 species endemic to the Greater Antilles and their satellite islands, appears to be a monophyletic exception within the tribe. However, the continued recognition of Mecranium as a genus, at best, would render Miconia paraphyletic. The most practical solution to the problem of non-monophyletic circumscription of genera in the Miconieae is the recognition of a broadly defined Miconia, with the taxonomic recognition of its subclades as subgenera and sections. Here the Mecranium clade is recognized as a section within a broadly circumscribed Miconia, all recognized species are listed, and 26 new names and nomenclatural combinations are published. In addition, the section is described, and the phylogenetic relationships of its species are discussed briefly based on molecular and morphological phylogenetic analyses.

Unusual diversity of apomictic mechanisms in a species of Miconia, Melastomataceae

Apomixis, the asexual formation of seeds, seems to be a reproductive alternative for many angiosperms, involving various pathways with different genetic and ecological consequences. It is common in some megadiverse tropical groups such as Melastomataceae, of which approximately 70% of the species studied so far in the tribe Miconieae are autonomous apomictics. Hence, Miconia appears to be a good model for the study of the embryological pathways associated with apomixis. In the present study, we analyzed the polyploid and autonomous apomictic M. fallax and compared its embryology to that of the diploid and sexual M. pepericarpa, both treelets species common in the Cerrado, the Neotropical savanna areas of Central Brazil. Ovule structure and basic megasporogenesis and megagametogenesis events were similar in both species. However, M. fallax showed exclusive features associated with apomixis: aposporous embryo sac development, with the parthenogenetic development of unreduced egg cells, autonomous endosperm formation, nucellar embryony and polyembryony. Moreover, both gametophytic and sporophytic apomixis occurred in parallel to the development of a sexual embryo sac, a rarely described condition, which probably confers a great reproductive flexibility to the species.

Primers for low-copy nuclear genes in the Melastomataceae.

Premise of the study:Low-copy nuclear gene primers were developed for phylogenetic studies across the Melastomataceae.Methods and Results:Total genomic libraries from eight species in the Melastomataceae along with one transcriptome were used for marker identification and primer design. Eight exon-primed intron-crossing markers were amplified with success in taxa of nine tribes in the Melastomataceae. The new markers were directly sequenced for eight samples of closely related species of Miconia (Chaenanthera clade) in the tribe Miconieae. The DNA sequences for the eight loci ranged from 660 to 818 aligned base pairs. Compared with four commonly used markers in other studies, the loci developed here had a higher number of variable sites than plastid spacers (7–16 vs. 26–45) and comparable variation to the ribosomal spacers (28–39).Conclusions:The novel primer pairs should be useful for a broad range of studies of systematics and evolution in the diverse Melastomataceae.

Discovery of unusual anatomical and continuous characters in the evolutionary history of Conostegia (Miconieae: Melastomataceae)

Conostegia has been traditionally defined to consist of 42 species in the tribe Miconieae. Recent phylogenetic studies have cast doubt on the monophyly of the genus and highlighted the need for a phylogenetic study focused on Conostegia. The purpose of this study was to test the monophyly of Conostegia and address relationships in the genus. We addressed the evolutionary history of Conostegia using DNA sequences from six loci. Difficulty in finding discrete characters that support clades prompted an anatomical survey of leaves and flowers as well as the exploratory use of some continuous characters. We coded as many species as possible for fifteen characters. Lastly, field work was conducted to document floral traits at anthesis due to the poor quality of preservation of flowers on herbarium specimens. Conostegia was found to be paraphyletic and composed of three main clades. The historically important characters of a calyptrate calyx and pleiostemony were found to have evolved more than once inside the Conostegia clade. Several other characters were found to support the clades we identified. The most unusual characters were mucilage inside the ovary which is here reported in the Melastomataceae for the first time, a stele inside the style which is mostly restricted to one clade of Conostegia and known only in this clade of the Melastomataceae, and herkogamy which has been lost in two clades within Conostegia. A combination of molecular phylogenetic analyses and broad morphological surveys allowed the better understanding of the evolutionary history in a clade of mostly cloud forest Neotropical trees. The need to include anatomical studies and tackle continuous characters is here demonstrated.

Anther wall and pollen development in Neotropical species-rich Miconia (Melastomataceae)

Miconia is one of the largest exclusively Neotropical genera, inserted in the tribe Miconieae. Although the monophyly of the tribe has recently been recognized, the delimitation of its genera is considered quite arbitrarily defined, mainly due to the great diversity combined with little morphological and genetic characterization of its members. Recent findings have associated this diversity with polyploidy, apomixis and hybridization, mechanisms commonly found in the group. The conventional delimitation of sections in Miconia, which has been largely based on stamen morphology, has proved to be undoubtedly artificial; nevertheless, the potential taxonomic significance of anther wall and pollen ontogenetic characters within the genera Miconia has been little explored. Hence, this study intended to fill that gap in our knowledge, by investigating the anther wall and pollen development in six closely related species of Miconia: M. albicans, M. fallax, M. latecrenata, M. paucidens, M. pepericarpa and M. stenostachya. Routine techniques for both light and electronic microscopy were used to examine anthers and pollen grains in several developmental stages. The species studied here share several character states, such as the remarkable monocotyledonous anther wall development, the persistent endothecium in the mature anthers with no cell wall thickenings, the bilocular dehiscent anther and the psilate pollen exine. This study also reports for the first time bisporangiate anthers, crystals and proteinoplasts in tapetal cells for Melastomataceae, and ultrastructural features of anther and pollen wall for Miconia.

Taxonomic studies in the Miconieae (Melastomataceae). XI. A revision of Miconia sect. Calycopteris on Hispaniola

A new section, Miconia sect. Calycopteris, is described and characterized. It includes 15 species previously recognized within Calycogonium, Clidemia, Henriettella, Leandra, Miconia, and Ossaea. Species descriptions, nomenclatural information, specimen citations, and eco-geographical characterization for each of the eight species occurring on Hispaniola are presented, along with an identification key. Section Calycopteris likely represents a monophyletic group within the Caribbean clade of tribe Miconieae (Melastomataceae) and is restricted to Hispaniola and Cuba. The section is characterized by strongly 4-lobed ovaries and hypanthia, calyx teeth that are flattened parallel to the floral radii, and seeds with a distinctive, dark-colored and expanded raphe. The following new combinations and new names are presented: Miconia hispidula, M. calycopteris, M. tetragonoloba, M. formonensis, M. nanophylla, M. reticulato-venosa, M. vegaensis, and M. maculata.

Diplospory and obligate apomixis in Miconia albicans (Miconieae, Melastomataceae) and an embryological comparison with its sexual congener M. chamissois

Apomixis, or asexual reproduction through seeds, has been reported for species of the tribe Miconieae, Melastomataceae, but details of the process have yet to be described. We analyzed and compared sporogenesis and gametogenesis in the apomictic Miconia albicans and the sexual M. chamissois. The results point to some differences between species, which were related to the apomictic process. In M. albicans microsporogenesis, problems during meiosis and degeneration of its products led to total pollen sterility, while M. chamissois presented normal bicellular pollen grains in the mature anther. The absence or abnormality of meiosis in M. albicans megasporogenesis led to the formation of an unreduced embryo sac and also to egg cell parthenogenesis, which gave rise to the apomictic embryo. Embryo and endosperm development were autonomous, resulting in seeds and fruits independent of pollination and fertilization. Thus, in this species, apomixis can be classified as diplosporic and obligate. In contrast, meiosis was as expected in the sexual M. chamissois, and led to the development of a reduced embryo sac. Despite the divergent pathways, many embryological characteristics were similar between the studied species and other Melastomataceae and they seem to be conservative character states for the family.

Seed diversity in the Miconieae (Melastomataceae): morphological

The seed morphology of 234 species distributed among 16 genera of the tribe Miconieae (Melastomataceae) was examined and documented with the use of scanning electron microscopy (SEM). Based on our observations and previously published investigations, we propose a set of 37 morphological characters for describing size, general shape, raphal zone, appendage, testa characters, and individual cell features of Miconieae seeds. Using these characters, we assembled detailed descriptions of all species in our sampling and constructed a data matrix for preliminary phenetic analysis (UPGMA algorithm; results to be presented elsewhere). In general, seed characters were easily identified and coded, although some of them presented difficulties, mostly due to the compression effects induced by fruit walls and neighboring seeds (e.g., shape). In contrast with other studies, we avoided the use of morphotypes, which have been shown to underutilize phenotypic variation. Our phenetic analysis does not agree with the traditional generic circumscription of the tribe, the sectional classification within Miconia , or with molecular phylogenetic analyses. This raises questions about the systematic and phylogenetic value of seed morphological characters in the tribe Miconieae.

Large-scale monographs and floras: the sum of local floristic research

Large-scale systematic efforts, both floristic and taxonomic, are the result of the unification of information found in smaller-scale projects or even collections. Three examples, all from tropical America, are presented to illustrate how these data and ideas are pooled. The effort to monograph the genus Leiothrix (Eriocaulaceae) is the successful work of a single researcher over time. The project to monograph the tribe Miconieae (Melastomataceae) demonstrates how joint effort by a collaborating group can monograph a group too large for any single person to attempt. The ‘List of Species of the Flora of Brazil’ project, with over 40,000 species listed, shows how over 400 systematists successfully contributed their knowledge to create a large-scale floristic reference.

Two new species of Miconia sect. Sagraea (Melastomataceae) from the Macaya Biosphere Reserve, Haiti, and twelve relevant new species combinations

The Sagraea clade (Melastomataceae, tribe Miconieae) is briefly characterized, typified, and formally treated as a section within Miconia. In addition, two new species of Miconia sect. Sagraea, endemic to the floristically diverse Massif de la Hotte of southwestern Haiti and discovered during the course of a systematic revision of the Caribbean species of this section, are here described and illustrated. Miconia hottensis and M. navifolia, morphologically similar and possible sister species, are compared to each other and to the widespread Caribbean species M. capillaris and the southwestern Dominican Republic endemic M. tetraptera; these four species share rectangular stems with four low ridges or wings and minute, short-stalked, peltate or pseudopeltate hairs and likely form a clade.

Polyembryony in Melastomataceae from Brazilian Cerrado: multiple embryos in a small world

Polyembryony has been commonly associated with apomixis in the angiosperms and seems to be more common than expected, even in biomes where sexual reproduction processes are predominant. Recent studies in Cerrado, the Neotropical savannas of Central Brazil, showed high frequencies of apomixis and polyembryony and indicated these processes as reproductive and evolutionary alternatives for plants in these areas. In this sense, we investigated the occurrence of polyembryony and its relationships with ecological (season and type of dispersal, ploidy, species distribution and breeding system) and taxonomic (tribe) factors in the Melastomataceae, a mostly tropical family already known for its high frequency of apomixis and very common in Cerrado. We collected seeds from 69 populations of 53 species, which were sown in germination chambers. After seed germination, the presence and number of seedlings per seed were evaluated as a method to estimate polyembryony. We encountered 18 species (33.96%) with polyembryony (more than one seedling, or gemellar seedlings, originated per seed) concentrated in species of the tribe Miconieae (64%) and Microlicieae (16.67%), but absent in Melastomeae. Monoembryony was present only in sexual species, while all apomictic species were polyembryonic. In Miconia, the polyembryony was correlated with polyploidy, and monoembryony with diploid species. Polyembryony was more common among species with wide distribution in the Cerrado region, which indicates that the presence of gemellar seedlings is important for establishment and survival of the group in the Cerrado biome.

Calycogonium pseudofloribundum, a new species ofMelastomataceae, Miconieae, from eastern Cuba

Abstract Becquer E. R.: Calycogonium pseudofloribundum, a new species of Melastomataceae, Miconieae, from eastern Cuba [Novitiae florae cubensis 37], — Willdenowia 41: 289–294. December 2011. — Online ISSN 1868-6397; © 2011 BGBM Berlin-Dahlem. Stable URL: http://dx.doi.org/10.3372/wi.41.41210 Calycogonium pseudofloribundum of the Melastomataceae tribe Miconieae, from eastern Cuba, a species new to science, is described and illustrated. C. pseudofloribundum is closely related to C. floribundum, with which it has been confused for a long time. It can be distinguished from the latter species by leaf features (the ovate to lanceolate leaves have an acute to apiculate apex, the blade is flat to slightly revolute, the margin usually obscurely to minutely dentate towards the apex, the adaxial surface is flat and usually opaque to whitish in dry material by presence of wax layers; they have two, rarely one, pair of secondary veins, the second pair originating 2–9 mm above the base), the external calyx teeth being...

A New Species of Physeterostemon (Melastomataceae) from Bahia, Brazil, with Notes on the Phylogeny of the Genus

Physeterostemon thomasii is described from the southern Bahian Atlantic forest of Brazil. It differs from the other two species of the genus by the paleaceous trichomes on young stems and petioles, and by the strongly bullate/foveolate leaves. A phylogenetic analysis with all three species, based on rbcL and ndhF DNA sequence data, showed that Physeterostemon forms a monophyletic group, sister to Eriocnema fulva, and this clade is placed in a polytomy at the base of the tribe Miconieae sensu stricto. However, there is no resolution within Physeterostemon, thus the phylogenetic relationships of the three species cannot be established.

Phylogeny ofMiconia(Melastomataceae): Patterns of Stamen Diversification in a Megadiverse Neotropical Genus

Phylogenetic relationships within Miconia and other genera in the Neotropical tribe Miconieae were investigated using a maximum parsimony analysis of nuclear internal transcribed spacer and ndhF nucleotide sequences. Included were all sections in Miconia (212 species, ∼20% of the genus) and 12 of the 15 remaining genera assigned to the tribe (an additional 239 species). Given the tribe’s reputation for problematic generic distinctions, it was not surprising that most traditionally recognized taxonomic groups—both genera and sections—were shown to be polyphyletic or paraphyletic. Nevertheless, Miconia is composed of several distinct monophyletic groups, with a large majority of the species belonging to only four clades. Some of these groups represent parts of sections proposed in the last revision of the genus, but most of the diversification seems to have occurred in geographical areas that are more restricted than would have been predicted by the distribution of these sections. Moreover, parallel evoluti...

Multiple Events of Dispersal and Radiation of the Tribe Miconieae (Melastomataceae) in the Caribbean

In the Caribbean region, the Melastomataceae are represented by about 450 species (from 28 genera), close to 400 of them endemic. The majority of these endemic species (approximately 330) belong to the tribe Miconieae, a monophyletic group characterized by flowers with inferior or partly inferior ovaries that develop into baccate fruits, stamens with no or only poorly developed connective appendages, and the absence of megastyloids and imbricate bracts at the base of the flowers. A phylogenetic analysis of 460 accessions from 450 species of the tribe Miconieae, including 139 present in the Antilles (103 of these endemic), was performed based on nuclear (nrITS) and plastid (ndhF) DNA sequence data. This analysis shows that most of the Caribbean endemics are the product of five radiation events: (1) a clade containing the Caribbean endemic (or near-endemic) genera Pachyanthus, Calycogonium, Tetrazygia and Charianthus, as well as a few representatives of Miconia and Leandra. (2) The genus Mecranium. (3) The Caribbean species of Miconia section Chaenopleura (which are probably not the sister group of Andean Chaenopleura). (4) The Greater Antillean species of Clidemia and Ossaea (including Sagraea). (5) The Lesser Antillean representatives of Clidemia. Caribbean endemics that are more closely related to mainland species, rather than other Caribbean species are rare, and these often are segregates of widespread continental species. Because of a lack of resolution at the base of several clades, it is currently not possible to determine which mainland groups are the closest relatives of these Caribbean endemics, thus preventing us from establishing unequivocally the geographical origins of these species.

Anatomia foliar de Melastomataceae do cerrado do Estado de São Paulo

Foi estudada a estrutura foliar de 22 especies de Melastomataceae (tribos Miconieae, Tibouchinieae e Microlicieae) encontradas no cerrado do estado de Sao Paulo. Em todos os representantes, as folhas sao dorsiventrais e hipostomaticas e a nervura principal e formada por xilema e por floema nas duas faces (exceto por uma unica especie). Determinados caracteres presentes nesses orgaos, como tipo e posicao dos estomatos e aspecto das superficies adaxial e abaxial, na regiao da nervura principal, variam consideravelmente dentro de um mesmo genero. Outros como espessura da cuticula nas duas superficies, tipo e morfologia dos tricomas, presenca ou nao de emergencias, porcentagem de parenquima palicadico e posicao e forma do sistema vascular principal, quando considerados em conjunto podem auxiliar na caracterizacao dos diferentes generos dentro das tribos. Esses aspectos sao descritos para os 22 representantes estudados e discutidos dentro de um contexto sistematico.

A preliminary phylogeny of the tribe Miconieae (Melastomataceae) based on nrITS sequence data and its implications on inflorescence position

Miconieae is the most diverse tribe of Melastomataceae, with 30 genera and over 2200 species. The tribe is characterized by fleshy fruits and partially to totally inferior ovaries. To test monophyly of the tribe and assess phylogenetic relationships within it, sequence data from nrITS were gathered and analyzed for 110 taxa in Miconieae and 32 putative outgroups. The tribe Miconieae is not resolved as monophyletic, but rather composed of two distinct clades: one composed of the cauliflorous genera Henriettea, Henriettella, Loreya and Bellucia, and a second clade with all other taxa in Miconieae, sister to a polytomy that includes representatives from tribes Merianieae and Blakeeae. Terminal inflorescences are optimized as basal within Miconieae, with lateral inflorescences evolving in at least four different instances. Cauliflory does not appear to be derived from truly axillary inflorescences; instead it seems to have evolved independently. The terminal–flowered genera Tococa, Conostegia, Tetrazygia, Anaectocalyx, Charianthus, Calycogonium, and Leandra pro parte seem to be derived from within the large genus Miconia, as is Clidemia, a genus with both axillary inflorescences and terminal inflorescences that are deflexed to a lateral position by an axillary branch. Maieta and Necranium, both with axillary inflorescences, are resolved as derived from within Clidemia.