ABSTRACT South Brazilian grasslands are among the most species-rich grasslands worldwide yet they have been suffering ongoing degradation due to land-use. Little is known about the reproductive ecology of the native species of these grasslands. Thus, our goal was to characterize seed traits and germination requirements of three native species of the tribe Tigridieae (Iridaceae, Iridoideae) due to its richness in the Pampa biome and the contrasting morphology, cytogenetics, and geographic distributions of its representatives. We tested if closely related species possess similar seed traits and whether species with wider distributions have broader germination requirements. Seed production and mass were estimated, and morphological analyses, germination experiments and viability tests were performed. Principal component analysis (PCA) was used to describe correlations between seed traits and species’ distributions. Germination was assessed using time-to-event analysis and the Cox model. All seed traits differed among the analyzed species/cytotypes. Final germination percentage (FGP) averaged 39.1 % and with overall viability of 89.9 %. Germination tests showed that seeds benefit from negative photoblasty. Species/cytotypes with wider distributions and heavier and larger seeds generally had better germination performances than narrower distributed species/cytotypes with lighter and smaller seeds.

Abstract Evolutionary analyses have been widely used for evaluation of genetic diversity of natural populations and correlate these data to the fitness of the species, especially in the case of threatened species. Calydorea crocoides occurs in a restricted area at altitudes from 800 to 1500 m in southern Brazil and is considered endangered. A study assessing genetic diversity, cytogenetic features and ecological niche was performed aiming to characterize C. crocoides by multidisciplinary approaches. Molecular data highlighted that most of the total variation (76%; p < 0.001) was found within populations and the parameters of genetic diversity were high at the species level (PPB = 98.97%; I = 0.4319; h = 0.2821). Gene flow (Nm) was estimated in 0.97 individuals per generation. Cytogenetically, C. crocoides presents a bimodal karyotype and low asymmetry. DAPI banding pattern was uniform, but the CMA-signal evidenced a pericentric inversion in the population ESC688. The species presents high pollen viability and two different morphologies of pollen grains. Our data showed high levels of polymorphism maintained in this species that could ensure conservationist practices in which the main goal is to preserve the evolutionary potential of the species through the maintenance of genetic diversity.

Para que as estratégias de melhoramento genético em espécies arbóreas tenham sucesso, o conhecimento da biologia reprodutiva da espécie envolvida é indispensável. Um dos fatores críticos ao sucesso reprodutivo das espécies do gênero Acacia é a presença de vetores para a polinização. Os objetivos deste trabalho foram identificar os visitantes florais em um plantio comercial de Acacia mearnsii De Wild. e quantificar as políades aderidas à superfície corporal dos insetos. As observações foram realizadas em uma torre localizada no plantio comercial durante o período de floração de 2002 e 2003. Os visitantes florais foram capturados no período diurno com o auxílio de rede entomológica e de um cesto aéreo instalado em um trator. No período noturno, os insetos foram capturados com o auxílio de armadilhas luminosas instaladas entre as copas florescidas. Foram observados insetos pertencentes às ordens Coleoptera, Hymenoptera, Diptera, Hemiptera e Lepidoptera. Os besouros da espécie Macrodactylus suturalis foram considerados como dispersores do pólen de acácia-negra, pela alta frequência de indivíduos presentes no povoamento estudado e pela grande quantidade de políades aderidas no corpo dos insetos capturados (X=229,36 políades/inseto). As abelhas da espécie Apis mellifera, embora tenha sido quantificada uma grande quantidade de políades nos indivíduos capturados (X=448,50 políades/inseto), não foram observadas com frequência na área analisada. Uma das formas recomendadas para aumentar a frequência de abelhas e vespas nos plantios comerciais de acácia-negra é a manutenção de fontes de néctar e a introdução de caixas com abelhas A. mellifera.

To ensure the success of the strategies of genetic improvement in tree species, knowledge of the reproductive biology of the species involved is essential. One of these critical factors in reproductive success of the genus Acacia is the presence of vectors to pollination. The purpose of this study was to identify flower visitors to a commercial plantation of Acacia mearnsii De Wild. and quantify the polyads attached to the body surface of the insects. The observations were made from a tower in a commercial stand during flowering, in 2002 and 2003. During the day, flower visitors were captured with an entomological net and an air basket installed on a tractor. At night, insects were caught with light traps installed between the flowering crowns. Insects belonging to orders Coleoptera, Hymenoptera, Diptera, Hemiptera and Lepidoptera were observed. Beetles of the species Macrodactylus suturalis were considered dispersers of black wattle pollen, based on the high frequency of individuals in the population studied and the high quantity of polyads adhered to the body of the caught insects (X=229,36 polyads/insect). The amount of polyads verified on bees of the species Apis mellifera was significantly greater (X=448,50 polyads/insect), but the frequency in the study area was insignificant. One of the recommended ways to increase the frequency of bees and wasps in black-watle commercial plantations is the maintenance of sources of nectar and the introduction of bee hives.

O objetivo deste trabalho foi analisar a receptividade de estigmas de Acacia mearnsii De Wild. em 20 árvores da Área de Produção de Sementes (APS) da Fazenda Locatelli, da empresa SETA S.A., no município de Butiá (RS) e comparar os períodos de receptividade de estigmas e de viabilidade polínica em diversas fases da abertura floral. Foi utilizado como método de colorimetria o reagente de Baker para indicar a receptividade e a viabilidade. As análises foram conduzidas em delineamento inteiramente casualizado e a estatística χ2 foi utilizada para verificar a significância dos eventos estudados. Foi observada receptividade no início da abertura floral (71%), alcançando a total receptividade (100%) em plena antese. A viabilidade polínica foi detectada no início da antese (77%) e em total abertura floral (88%). Na fase de senescência foram observados estigmas receptivos (50%) e políades viáveis (23%). Há sobreposição da fase de viabilidade masculina e de receptividade feminina, aumentando as chances de autopolinização. Na maioria das árvores analisadas (85%) foi observada a total receptividade (100%) nos estigmas amostrados. Em três árvores (15%) observou-se uma média inferior a 95% de estigmas receptivos. Não foi observada diferença significativa pelo teste do χ2 na receptividade dos estigmas no germoplasma analisado, sugerindo que o genótipo não interfere diretamente para a receptividade dos estigmas.

The purpose of this study was to evaluate the stigma receptivity of Acacia mearnsii De Wild. in 20 trees of the Seed Production Area on the Fazenda Locatelli of the company SETA S.A., in the county of Butiá, state of Rio Grande do Sul, and to compare the periods of stigma receptivity and pollen viability at different stages of flower opening. The colorimetry method of the Baker reagent was used to determine receptivity and viability. The analyses were evaluated in a completely randomized design and the χ2 statistics were used to verify the significance of the studied events. The receptivity increased from the beginning of flower opening (71%) to total receptivity (100%) at full anthesis. Pollen viability was detected in the beginning of anthesis (77%) and at total flower opening (88%). Receptive stigmas (50%) and viable polyads (23%) were observed in the senescence stage. The phases of male viability and female receptivity were superposed, which increases the chances of self-pollination. Full receptivity (100%) was observed in the sampled stigma of most evaluated trees (85%). In three trees (15%) receptive stigmas were in the mean below 95%. No significant difference was detected by the χ2 test in the stigma receptivity of the germplasm under study, indicating that the genotype does not interfere directly with stigma receptivity.