The post-fire effects on the outcrossing rate of a Brazilian savannah shrub, Helicteres sacarolha A.St.-Hil

Abstract

-(The post-fire effects on the outcrossing rate of a Brazilian savannah shrub, Helicteres sacarolha A.St.-Hil.). The effect of post-fire, plant density and number of flowers per plant on outcrossing rates was examined in a Brazilian savannah shrub, Helicteres sacarolha. Data on number of flowering plants and flowers per plant were collected during the flowering season in January and February of 1994. In October of 1994, a fire swept through the studied area after 30 years of fire absence. The burnt plants of H. sacarolha resprouted, producing flowers and fruits in 1995. Seeds from several plants in both years were collected. Allozyme markers were used to estimate the multilocus outcrossing rates for 1994 and 1995 progenies. After the fire, outcrossing rates increased. In 1995, plants flowered vigorously, increasing flower density and probably pollinator activity. Helicteres sacarolha seems to be fire resistant, like other plant species of the Brazilian savannah, but several plants tagged in 1994 were not found after the fire, and may have died. Thus, although genetic diversity and outcrossing rates increased following the fire in 1994, repeated events of fire may decrease drastically the population size of H. sacarolha, leading to a diminished genetic diversity and outcrossing rates.Key words -cerrado, flower density, Helicteres, plant outcrossing rate, post-fire effect RESUMO -(Os efeitos pós-fogo na taxa de cruzamento de um arbusto do cerrado, Helicteres sacarolha A.St.-Hil.). Os efeitos do fogo, da densidade de plantas, do número de flores por planta na taxa de cruzamento foram checados para uma espécie de arbusto do cerrado, Helicteres sacarolha. Dados de número de plantas e flores por planta foram coletados durante o período de floração de janeiro a fevereiro de 1994. Em outubro de 1994, uma queimada ocorreu na área de estudo após 30 anos de ausência de fogo. No entanto, as plantas queimadas de H. sacarolha brotaram, produzindo flores e frutos em 1995. Sementes de várias plantas foram coletadas em 1994 e 1995. Marcadores aloenzimáticos foram utilizados para estimar a taxa de cruzamento para as progênies de 1994 e 1995. A taxa de cruzamento aumentou após a ocorrência do fogo. Em 1995, as plantas floresceram vigorosamente, aumentando a densidade de flores e, provavelmente, a atividade dos polinizadores entre as plantas da população. Como muitas espécies do cerrado brasileiro, H. sacarolha é tolerante ao fogo, contudo várias plantas marcadas em 1994 não foram encontradas após o fogo e podem ter morrido queimadas. Desta forma, eventos repetidos de fogo podem levar a uma drástica diminuição do tamanho da população de H. sacarolha e, conseqüentemente, a um decréscimo em suas taxas de diversidade genética e de cruzamento.Palavras-chave -cerrado, densidade de flor, efeito do fogo, Helicteres, taxa de cruzamento

Effects of an accidental dry-season fire on the reproductive phenology of two Neotropical savanna shrubs

“…Fire-stimulated flowering and reproduction have often been observed for subshrubs and herbaceous species in the cerrado (Munhoz and Felfili, 2005;2007;Neves and Damasceno-Junior, 2011), but fire effects on woody plants vary from inhibition to stimulation of reproduction (Hoffmann, 1998;Felfili, et al 1999;Franceschinelli and Bawa, 2005;Lucena et al, 2015). Our results corroborate this variation in the fire responses for woody species, which cannot be explained by factors such as growth form (Lamont and Downes, 2011), leaf deciduousness (Lucena et al, 2015), or seed dispersal syndromes (Lamont and Downes, 2011).…”

“…obs. ), and the smaller activity and intensity indices of flowering in the burnt plants may putatively impact the pollinator community as well as decrease outcrossing (Franceschinelli and Bawa, 2005). Similarly, the lower fruit production by burnt individuals of M. albicans, especially considering that only five of the 30 burnt M. albicans plants produced ripe fruits during the study period, may have impacts on the frugivorous community, as the fruits of this species are consumed by at least 19 bird species at the study site (Allenspach and Dias, 2012).…”

Post-fire flowering and fruiting in Vellozia sincorana, a caulescent rosette plant endemic to Northeast Brazil

“…Th e abundant fl owering and fruiting in the weeks immediately following a fi re creates a sudden, abundant supply of resources for local fauna. Th is, in turn, can have a positive system-wide eff ect on pollination and fruit production (Franceschinelli & Bawa 2005). Seed dispersal during the wet season and the pulse of nutrients aft er burning (Johnson et al 1994;Whelan 1995) may benefi t the germination and establishment of plants following fi res that occur at the end of the dry season, which happened in this study of V. sincorana.…”

“…Several papers report the importance of fi re in the sexual reproduction of plant species in diff erent ecosystems (Coutinho 1977;Lamont & Downes 1979;Pyke 1983;Givnish et al 1986;Johnson et al 1994;Taylor et al 1998;Lamont et al 2000;Verboom et al 2002;Bowen & Pate 2004;Franceschinelli & Bawa 2005;Schmidt et al 2005;Paula & Pausas 2008). However, fi re is also viewed as an undesirable disturbance with negative impacts on the local, regional and even global environment, infl uencing climatic patterns, and sometimes precipitating changes in vegetation communities, mitigated by ecosystem type, local site characteristics, the season of year, frequency of fi re, and the amount of dry combustible material accumulated, among other factors (McNeely et al 1990;Whelan 1995;RamosNeto & Pivello 2000;Franceschinelli & Bawa 2005;Pivello 2006;Cochrane 2009).…”

“…However, fi re is also viewed as an undesirable disturbance with negative impacts on the local, regional and even global environment, infl uencing climatic patterns, and sometimes precipitating changes in vegetation communities, mitigated by ecosystem type, local site characteristics, the season of year, frequency of fi re, and the amount of dry combustible material accumulated, among other factors (McNeely et al 1990;Whelan 1995;RamosNeto & Pivello 2000;Franceschinelli & Bawa 2005;Pivello 2006;Cochrane 2009).…”