Pollinator availability, mating system and variation in flower morphology in a tropical savanna tree

Abstract

Widely distributed organisms face different ecological scenarios throughout their range, which can potentially lead to micro-evolutionary differentiation at specific localities. Mating systems of animal pollinated plants are supposed to evolve in response to the availability of local pollinators, with consequent changes in flower morphology. We tested the relationship among pollination , mating system, and flower morphology over a large spatial scale in Brazilian savannas using the tree Curatella americana (Dilleniaceae). We compared fruit set with and without pollinators in the field, and analyzed pollen tube growth from self-and cross-pollinated flowers in different populations. Populations with higher natural fruit set also had lower fruit set in bagged flowers, suggesting stronger barriers to self-fertilization. Furthermore, higher levels of autogamy in field experiments were associated with more pollen tubes reaching ovules in self-pollinated flowers. Morphometric studies of floral and leaf traits indicate closer-set reproductive organs, larger stigmas and smaller anthers in populations with more autogamy. We show that the spatial variation in mating system, flower morphology and pollination previously described for herbs also applies to long-lived, perennial tropical trees, thus reemphasizing that mating systems are a population-based attribute that vary according to the ecological scenario where the plants occur.

Population‐level plant pollination mode is influenced by Quaternary climate and pollinators

“…In conclusion, our results indicate that historical instability in climate has favored autogamy, while pollinators are currently modulating the level of cross‐pollination. Although the direct impact of historical climate on pollinator communities should be examined in future studies, this association of historical climate instability to autogamy suggests a reproductive assurance strategy that may have benefitted the species during unstable conditions in the past (Rech et al., 2018). This strategy could be a key factor explaining why C .…”

“…The main flower visitors and potential pollinators of C. americana flowers were bees of different sizes (more details in Rech et al, 2018).…”

“…In (Rech et al, 2018). This strategy could be a key factor explaining why C. americana is one of the most conspicuous and widely distributed woody species in Neotropical savannahs (Ratter et al, 2003).…”

“…We chose Curatella americana L. (Dilleniaceae) as our species model as it is one of the main pollen types used to reconstruct the history of South American savannah environments (Absy et al., 1997; Behling, 1995). Moreover, the association of this species with savannahs and its mixed mating system (Rech et al., 2018) makes C . americana a suitable model to address ecological questions about spatial variability and historical climate stability on plant mating systems.…”

Biologia floral, fenologia reprodutiva e polinização de Xylopia aromatica (Lam.) Mart. (Annonaceae) em uma área de Cerrado no oeste da Bahia

“…Assim como outras espécies da família Annonaceae, X. aromatica é uma espécie alogâmica, protogínica e apresenta alto grau de autoincompatibilidade genética, de acordo com estudos desenvolvidos em área de Cerrado na região sudeste do Brasil (Costa et al, 1992). No entanto, o sistema reprodutivo de uma espécie pode variar dentro do alcance de sua distribuição geográfica devido à necessidade de equilibrar as garantias promovidas pela variabilidade genética, oriunda da polinização cruzada, e a segurança reprodutiva, promovida pela autopolinização, fatores que variam em resposta à diferentes condições espaço-temporais (Rech et al, 2018;Opedal et al, 2016). Isto justifica a importância de estudar a mesma espécie, em diferentes áreas e épocas, mesmo que já exista algum conhecimento prévio acerca de suas estratégias reprodutivas.…”