Sexual ratio and floral biology of the dioecious Neea theifera Oerst. (Nyctaginaceae) in a cerrado rupestre of central Brazil

Abstract

Sexual ratio and fl oral biology of the dioecious Neea theifera Oerst.(Nyctaginaceae) in a cerrado rupestre of central Brazil Dioecy is characterized by a complete separation of sexual functions on male and female plants. It has evolved many times in fl owering plants and is widespread among distinct Angiosperm families. It is viewed as a reproductive strategy to reduce endogamy, and to promote optimal resource allocation between male and female sexual functions. Neea theifera is a common species in Cerrado, neotropical savannas in Brazil, but information regarding its reproductive biology is still incomplete. In order to investigate how environmental conditions possibly aff ect this dioecious species, we studied its fl oral biology, sex ratio and spatial distribution of sexual morphs along a soil-altitudinal gradient. Th e sex ratio did not signifi cantly deviate from the expected 1:1 ratio. However, fl ower abundance in the population was signifi cantly biased towards staminate fl owers. Female individuals were larger than male individuals and plant size was negatively correlated with altitude, but did not diff er between sexual morphs. Th e population did not show spatial segregation of sexes and male individuals were sexually mature earlier than female ones. Staminate fl owers were larger than pistillate fl owers and presented high pollen viability. Meliponini bees, small fl ies and thrips were potential pollinators, but pollination success was very low. Dioecy in N. theifera corroborates many general features of this reproductive strategy, such as woody habit, inconspicuous fl owers, pollination by small generalist insects and diff erential resource allocation between male and female plants. However, reproduction in this species seems to be impaired by pollinator limitation. Th e results showed that the soil-altitude gradient infl uenced the growth pattern of the species and may play an important role in its reproductive biology but did not aff ect dioecy directly.

Four o'clock pollination biology: nectaries, nectar and flower visitors in Nyctaginaceae from southern South America

“…Bullock () proposed wind pollination for Pisonia and Guapira Aubl., based on the small and inconspicuous flowers. However, our study clearly corroborates other records indicating that entomophily could be a pollination syndrome of this group, as found in P. aculeata (Chodat & Rehfous, ), Guapira noxia (Netto) Lundell and Neea theifera Oerst (Oliveira & Gibbs, ; Amorim et al ., ). Both male and female flowers of P. zapallo var guaranitica Toursark.…”

Foraging behavior and pollination efficiency of generalist insects in an understory dioecious shrubHelwingia japonica

“…Many understory dioecious species are characterized by relatively small white, yellow, or pale green flowers, pollinated by a wide variety of relatively small generalist visitors, primarily small bees (Bawa and Opler, 1975; Bawa, 1980, Thomson and Brunet, 1990), or eusocial and solitary bees, flies, and beetles (Opler et al, 1980; Muenchow, 1987). For example, in Neea theifera , inconspicuous flowers were visited by small generalist insects, meliponine bees, small flies, and thrips (Amorim et al, 2011). Direct investigations of visitor preference in several dioecious species indicated that insect visits to male and female plants were opportunistic and unbiased (Borkent and Harder, 2007; Brown and McNeil, 2009; Matsuyama et al, 2009).…”

Flowering phenology of Catopsis compacta (Bromeliaceae), a dioecious epiphyte in an oak forest

“…Male plants allocate more resources to produce more flowers because their fitness is directly linked to the number of pollen grains released. Further, the bigger the floral display, the more likely it is to be visited by pollinators (Bram & Quinn 2000, Amorim et al 2011, Forrest 2014.…”

“…These costs are energetically expensive, dramatically more so for epiphytes considering the oligotrophic environment in which they grow (Benzing 1990, Espírito-Santo et al 2003, Amorim et al 2011.…”