-(Reproductive strategy of Cochlospermum orinocense (Kunth) Steud.: phenology, fl oral biology and breeding system of an Amazonian forest pioneer species). Cochlospermum orinocense (Kunth) Steud. is an arboreal species found in forest edges, canopy gaps and secondary forests. Phenology, fl oral biology and breeding system data was gathered at the edge of an 80 ha primary terra-fi rme Amazonian forest fragment in the São Luís Island, Maranhão state. Cochlospermum orinocense is a deciduous species which fl ower annually, showing intense and synchronized fl owering early in the dry season. Its hermaphrodite and slightly zygomorphic fl owers are arranged in terminal infl orescences and last only one day. Each ovary has on average 250 ovules and the androecium about 160 poricidal dehiscence anthers presenting 81.6% viable pollen and P/O ratios of 16,019.2. Anthesis is diurnal and the fl owers are pollinated mainly by solitary bees of the species Centris spp. Cochlospermum orinocense is self-compatible (ISI = 0.98) with high reproductive effi cacy (RE = 0.81) and reduced or null apomixis. Clustered distribution in deciduous trees together with intense and synchronized fl owering in the dry season leads to highly effi cient pollination. Fecundity is thus limited to resources constraints and not by pollen availability. Geitonogamy, the commonest form of endogamy, may assure the reproductive success of isolated individuals in the forest but leads to endogamic depression. The high density clustering often found in this species encourages allogamy and may allow high reproductive effi ciency and higher fecundity as endogamic depression is minimized.Key words -Cochlospermum orinocense, geitonogamy, inbreeding depression, mixed mating system RESUMO -(Estratégia reprodutiva de Cochlospermum orinocense (Kunth) Steud.: fenologia, biologia fl oral e sistema de cruzamento em uma espécie pioneira de fl orestas na Amazônia). Cochlospermum orinocense (Kunth) Steud. é uma espécie arbórea freqüente em clareiras, na borda da fl oresta e em fl orestas secundárias na Amazônia. Dados da fenologia, biologia fl oral e sistema de cruzamento foram obtidos em indivíduos na borda de um fragmento de 80 ha de fl oresta Amazônica primária, de terra fi rme, na ilha de São Luís, MA. Cochlospermum orinocense é uma espécie decídua com fl oração anual precoce, intensa e sincronizada na estação seca. Suas fl ores hermafroditas e levemente zigomorfas estão dispostas em infl orescências terminais e têm duração de um dia. Cada ovário possui em média 250 óvulos e o androceu é composto por cerca de 160 anteras, de deiscência poricida, apresentando 81,6% de pólen viável e razão P/O de 16.019,2. A antese é diurna e as fl ores são polinizadas predominantemente por abelhas solitárias Centris spp. A espécie é autocompatível (IAI = 0,98) com alta efi cácia reprodutiva (ER = 0,81), sendo a apomixia reduzida ou nula. Distribuição agrupada e fl oração intensa e sincronizada na seca, em árvores decíduas, induzem alta efi ciência na polinização, sendo a fecundi...
-(Predation and parasitism on seeds of two populations of Parkia platycephala Benth., from "cerrado" areas in Northeast Brazil). Two morphologically distinct populations of Parkia platycephala with different densities in the Cerrado, have their seeds preyed by larvae of the coleoptera Acanthoscelides imitator Kingsolver 1985, which are parasitized by the hymenoptera Stenocorse bruchivora Crawford 1900. In this study the effects of nesting, predation, and parasitism on seed germination were evaluated, and the rates of these events were compared between the two populations. Germination tests were conducted in laboratory, using four replicates of 50 seeds. Nesting, predation and parasitism rates for each population were estimated by sampling seeds from 20 fruits per individual, and from 15 individuals per population. The seeds of P. platycephala exhibit dormancy enforced by the seed coat. The nesting breaks the dormancy, and the pre-dispersal predation of seeds by the coleoptera larvae make them inviables. The larvae predation is biologically controlled by the hymenoptera parasitism. The seed predation rates for each population were 28% and 12%, respectively, being significantly higher in the white population, which produces more and smaller seeds per fruit than the other population. The highest predation occurs because of the highest nesting rate by the coleopterans, which is positively correlated with the number of seeds per fruit. The parasitism rate was 8%, approximately, and was not significantly different between the populations. The results indicate that the differences between the densities of these populations were not related to the biological interactions, as seed predation and parasitism.Key words -"cerrado", germination, parasitism, Parkia platycephala, seed predation RESUMO -(Predação e parasitismo em sementes de duas populações de Parkia platycephala Benth., em áreas de cerrado no nordeste do Brasil). Duas populações morfologicamente distintas de Parkia platycephala, que diferem quanto à densidade no cerrado, têm suas sementes predadas por larvas de coleópteros Acanthoscelides imitator Kingsolver 1985 as quais são parasitadas por himenópteros Stenocorse bruchivora Crawford 1900. Neste trabalho determinou-se o efeito da nidificação, predação e parasitismo na germinação das sementes, comparando-se as taxas destes eventos entre as duas populações. Os testes de germinação foram conduzidos em laboratório, utilizando-se quatro repetições de 50 sementes. As taxas de nidificação, predação e parasitismo nas populações no cerrado foram estimadas em amostras de sementes colhidas de 20 frutos por indivíduo, em 15 indivíduos por população. As sementes de P. platycephala exibem dormência imposta pelo tegumento. A nidificação quebra a dormência e a predação pré-dispersão das sementes por larvas dos coleópteros as inviabiliza, sendo biologicamente controlada pelo parasitismo das larvas pelos himenópteros. A taxa de predação das sementes foi de 28% e 12% respectivamente, sendo significativamente maior na pop...
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