João Semir

Fly‐pollinated Pleurothallis (Orchidaceae) species have high genetic variability: evidence from isozyme markers

We conducted an isozyme study in 22 populations of five Pleurothallis (Orchidaceae) species (12 loci in nine enzymatic systems). The genetic variability in all populations is surprisingly high (P = 58-83%, A = 2.1-3.8, H(e) = 0.25-0.43) in spite of the fact that the five species are pollinated by small flies whose behavior enables self-pollination. We suggest that self-incompatibility, inbreeding depression, and mechanical barriers that prevent self-pollination in these species are responsible for the maintainance of the high genetic variability. These traits are uncommon in Orchidaceae, but have been observed in these and some other species pollinated by flies or other pollinators with behavior that facilitates self-pollination. The genetic similarity among conspecific populations is also high for species with very short-range flying pollinators. Only one population of P. teres presented values of genetic similarity lower than usually observed in allopatric conspecific populations. Morphology, however, does not support its segregation as a new taxon. All species can be recognized by their enzymatic patterns, and the results agree with recently proposed taxonomic realignments. Conversely, the supposed affinities among these species based on floral morphology are not supported, and we hypothesize that it may be due to convergence in species with similar pollinators.

The Genus Petunia

The common garden petunia, Petunia hybrida, is derived from P. integrifolia and P. axillaris, two of many Petunia species endemic to South America. The geographic distribution includes temperate and subtropical regions of Argentina, Uruguay, Paraguay, Bolivia, and Brazil, with a center of diversity in southern Brazil. The presence of seven chromosomes and a number of morphological, anatomical, and biochemical characteristics differentiate the genus from its sister taxon, Calibrachoa. Included in this chapter is a taxononomic guide for the 14 currently recognized species, some of them restricted to very small geographic areas. Species diversity is in danger of diminishing significantly due to human intervention, particularly in the form of grassland destruction.

Temporal variation in pollinarium size after its removal in species of Bulbophyllum: A different mechanism preventing self-pollination in Orchidaceae

InBulbophyllum involutum andB. ipanemense (Orchidaceae), two closely related species, shortly after removal the pollinarium has a diameter of approximately twice that of the entrance of the stigmatic cavity, requiring a mean time of 105 to 135 minutes to shrink in width and allow pollination. Because the pollinators of these species remain for some minutes in the same flower after removing the pollinia this mechanism, previously unknown inOrchidaceae, may be very important in preventing self-pollination. This mechanism does not occur inB. weddellii, and the pollinator does not remain in the flower after removing the pollinia. The smaller diameter of the stigmatic cavity inB. involutum reduces by 50% the chances of interspecific pollination withB. weddellii, and interspecific crossing is strictly unidirectional. This is important in maintaining isolation between these sympatric species, which share the same pollinators and have synchronized flowering.

A simple solid injection device for the analyses of Bulbophyllum (Orchidaceae) volatiles

Abstract The volatile components of three orchid species ( Bulbophyllum weddellii , B. ipanemense and B. involutum ) were detected using GC/MS. Due to the minute dimension and amount of flowers, special traps and extraction methods were applied and the analyses were finally successful using a special solid sample injector which was constructed in our own laboratory. The chemical composition comparison revealed the high similarity between the volatiles present in B. weddellii and B. involutum , which is coherent with the pollinator sharing. On the other hand, the volatiles of B. ipanemense , a species pollinated by other pollinator species, are different from the two previous species.

Late‐Acting Self‐Incompatibility and Other Breeding Systems in Tabebuia (Bignoniaceae)

Although breeding system investigations were previously performed in only nine of the 100 Tabebuia species, indications of self‐incompatibility have been found in all of them, and the four species studied for the site of incompatibility reaction showed some kind of late‐acting self‐incompatibility. Polyembryony has been found in T. chrysotricha and T. ochracea, with adventitious origin of the extra embryos being shown in the latter. We investigated the breeding system in five species of Tabebuia by hand‐pollination experiments, fluorescence microscopy study of in situ pollen tube growth, and histological analysis of postpollination events. Although both T. chrysotricha and T. heptaphylla developed fruits by self‐pollination, polyembryony was verified only in the former, which indicates that self‐fertility in Tabebuia is not necessarily associated with apomixis. The remaining species were 100% self‐sterile. Although some penetrated ovules in crossed pistils of T. vellosoi were found at the 48‐h interval, none of the ovules in selfed pistil was penetrated at the same interval, with penetration of many ovules occurring 72 h postpollination. In T. impetiginosa, ovule penetration efficiency 48 h after pollination was higher in cross‐ than in self‐pollinated pistils, and the majority of the ovules in selfed pistils were penetrated and fertilized in 72 h. The incidences of ovule fertilization and endosperm initiation were significantly slower in selfed compared with crossed pistils, and a clear developmental slowdown of the endosperm occurred in selfed pistils before abscission, although no other signs of developmental malfunctions were detected. In all of the self‐sterile species, abortion of selfed pistils occurred in a small period after pollination, and no swelling of the ovary was observed in T. umbellata. All of these results agree with the occurrence of late‐acting self‐incompatibility in T. impetiginosa, T. umbellata, and T. vellosoi, and no evidence was found that self‐sterility in these species is due to inbreeding depression.

Asteraceae do Parque Nacional da Serra da Canastra, Minas Gerais, Brasil

A check-list of Asteraceae was carried out between February 1994 until January 1998, in Serra da Canastra National Park, which is located in Southern Brazil. All specimens are deposited at the herbarium of the Universidade Federal de Uberlândia, Minas Gerais, Brazil (HUFU). The Asteraceae is the most diverse family of the Serra da Canastra. The total number is 215 species, belonging to 66 genera, and 11 tribes. One significative result is the discovery of 27 new species, representing 19 genera of seven different tribes. Some of them belong to monotypic or small genera as Xerxes, Hololepis, Pseudobrickellia, and Inulopsis, and others to several genera which have great importance to the Brazilian Asteraceae flora, such as Lessingianthus, Chromolaena, Stevia, Mikania, Aspilia, Calea, and Senecio. This inventory has the highest number of species recorded in one study area in Brazil.

O gênero Miconia Ruiz & Pav. (Melastomataceae) no Estado de São Paulo

The present paper deals with the species of Miconia occuring in the Brazilian State of Sao Paulo. The 53 species listed and described here probably represent all taxa of the genus collected in this State.

Fenologia da floração e biologia floral de bromeliáceas ornitófilas de uma área da Mata Atlântica do Sudeste brasileiro

This study dealt with phenology and flower visitors of some Bromeliaceae species in an Atlantic Forest area at Parque Estadual Intervales, southeastern Brazil. The taxa studied belonged to the genera Tillandsia L. (3 spp.), Vriesea Lindl. (5 spp.), Aechmea Ruiz & Pav. (3 spp.), Billbergia Thunb. (1 sp.) and Nidularium Lem. (2 spp.). Sample transects were established in areas with different succession stages, where the bromeliads were localized and marked. Flowering phenology surveys were made monthly. The bromeliad community showed a sequential flowering all along the year and most species flowered during the rainy season. The floral visitors were recorded by naturalistic observations. Eight hummingbird species visited the bromeliads flowers. Among them, Phaethornis eurynome Lesson and Thalurania glaucopis Gmelin were the most frequent visitors. Bromeliads were divided in two groups by similarity analysis of floral visitors (hummingbirds): a group represented by species visited by Trochilinae hummingbirds and another visited by Phaethornis eurynome (subfamily Phaethornithinae). The competition among bromeliad species for pollinators is reduced due to their spatial distribution and the flowering periods.

Local genetic differentiation in Proteopsis argentea (Asteraceae), a perennial herb endemic in Brazil

Abstract. Proteopsis argentea (Asteraceae, Vernonieae) is a perennial herb endemic to the “campos rupestres” of the Espinhaço Range in Minas Gerais, Brazil, with fragmented populational distribution. Eleven populations were sampled, throughout the entire distribution of the species, and assayed for isozyme variation. Low intra-population genetic diversity was found (P = 19.2; A = 1.30; He = 0.058) whereas species level diversity was higher (P = 55.5, A = 2.0, He = 0.093). The most geographically isolated population showed exclusive alleles at two loci, whereas two populations less than 2 km apart from each other showed inverted frequencies for two alleles. Mean genetic identity was high (I = 0.974), but the large Fst (0.30) indicates that the species could lose an important part of its genetic variation with the extinction of a single population. Our findings indicate that geographic isolation alone cannot explain population differentiation: localized pollinator behaviour and selection, for example, may be contributing to the patterns observed.

Pollination biology and breeding system of Zeyheria montana (Bignoniaceae)

Abstract.The reproductive biology of Zeyheria montana was studied through field observations of flower visitors and floral events, controlled manual pollinations, and observations of pollen tube growth and ovule penetration by fluorescence microscopy. Analysis of secretory areas of the nectar chamber was made by flower dissections and histology of serial sections. The flower lasted 6–8 days, but pollen exposure and stigma receptivity occurred only up to the end of the first and second days, respectively. Pollination was effected by several species of hummingbirds, especially Colibri serrirostris. The flowers present a rudimentary, non-functional disc, and secretion of nectar is performed by corolla-borne glandular trichomes. Only hand cross-pollinated and natural-pollinated flowers set fruits. Artificially self-pollinated and non-pollinated flowers dried off after anthesis without presenting any swelling of the ovary. Almost all the ovules in selfed and crossed pistils were penetrated 96 h after pollination. However, a delay in ovule penetration in self-pollinated pistils was verified, which indicates the occurrence of late-acting self-incompatibility.