The Cerrado plant species present periodic variations in its growth and reproduction usually closely related to climate seasonality. This study aimed to compare the reproductive phenology (flowering and fruiting) of plant species from a dry and a wet grassland in a Cerrado (Brazilian savanna) area at southeastern Brazil (Itirapina, SP) in order to answer the following questions: (i) do the plant species of each physiognomy flower and fruit seasonally? (ii) are the phenological patterns similar, in each physiognomy, among different life forms? (iii) do the physiognomies differ in respect to the proportion of species according to seed dispersal modes? (iv) do the physiognomies differ in respect to the fruiting patterns according to seed dispersal modes? (v) is the reproductive phenology of the species in each physiognomy, according to its life forms and dispersal modes, correlated to the climatic seasonality? We analyzed the vouchers included in the collection of the Herbarium of the Instituto de Biociências de Rio Claro, Universidade Estadual Paulista -UNESP from 1983 to 2005. The plant species were classified into life forms (woody and herbaceous) and dispersal modes (anemo, auto and zoochorous). In both physiognomies the phenological patterns were very seasonal, usually with a peak during the wet season, but differing according to the life form and dispersal mode. The observed differences were related to the environmental conditions of each physiognomy, mainly to the patterns of soil drainage. Phenological patterns were largely influenced by life forms, but the dispersal modes did not show the expected fruiting patterns, based on other studies of different Cerrado areas, emphasizing the importance of conducting detailed field phenological studies in dry and wet grasslands.
Flowering patterns are crucial to understand the dynamics of plant reproduction and resource availability for pollinators. Seasonal climate constrains flower and leaf phenology, where leaf and flower colors likely differ between seasons. Color is the main floral trait attracting pollinators; however, seasonal changes in the leaf-background coloration affect the perception of flower color contrasts by pollinators. For a seasonally dry woody cerrado community (Brazilian savanna) mainly pollinated by bees, we verified whether seasonality affects flower color diversity over time and if flower color contrasts of bee-pollinated species differ between seasons due to changes in the leaf-background coloration. For 140 species, we classified flower colors based on human-color vision, and for 99 species, we classified flower colors based on bee-color vision (spectral measurements). We described the community’s flowering pattern according to the flower colors using a unique 11 years phenological database. For the 43 bee-pollinated species in which reflectance data were also available, we compared flower color diversity and contrasts against the background between seasons, considering the background coloration of each season. Flowering was markedly seasonal, peaking at the end of the dry season (September), when the highest diversity of flower colors was observed. Yellow flowers were observed all year round, whereas white flowers were seasonal, peaking during the dry season, and pink flowers predominated in the wet season, peaking in March. Bee-bluegreen flowers peaked between September and October. Flowers from the wet and dry seasons were similarly conspicuous against their corresponding background. Regardless of flowering season, the yellowish background of the dry season promoted higher flower color contrast for all flower species, whereas the greener background of the wet season promoted a higher green contrast. Temporal patterns of flower colors and color contrasts were related to the cerrado seasonality, but also to bee’s activity, visual system, and behavior. Background coloration affected flower contrasts, favoring flower conspicuousness to bees according to the season. Thus, our results provide new insights regarding the temporal patterns of plant–pollinator interactions.
Summary
Genetic divergence between species depends on reproductive isolation (RI) due to traits that reduce interspecific mating (prezygotic isolation) or are due to reduced hybrid fitness (postzygotic isolation). Previous research found that prezygotic barriers tend to be stronger than postzygotic barriers, but most studies are based on the evaluation of F1 hybrid fitness in early life cycle stages.
We combined field and experimental data to determine the strength of 17 prezygotic and postzygotic reproductive barriers between two Lysimachia species that often co‐occur and share pollinators. We assessed postzygotic barriers up to F2 hybrids and backcrosses.
The two species showed near complete RI due to the cumulative effect of multiple barriers, with an uneven and asymmetric contribution to isolation. In allopatry, prezygotic barriers contributed more to reduce gene flow than postzygotic barriers, but their contributions were more similar in sympatry.
The strength of postzygotic RI was up to three times lower for F1 progeny than for F2 or backcrossed progenies, and RI was only complete when late F1 stages and either F2 or backcrosses were accounted for. Our results thus suggest that the relative strength of postzygotic RI may be underestimated when its effects on late stages of the life cycle are disregarded.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.