Pollination biology and breeding system of syntopic Adenocalymma nodosum and A. peregrinum (Bignonieae, Bignoniaceae) in the Brazilian savanna

Abstract

The tropical Bignoniaceae is mostly late-acting self-incompatible (LSI) and depends on a guild of medium to large sized bees for their pollination. Adenocalymma nodosum and A. peregrinum are syntopic shrubs in savanna areas with similar flowers and flowering overlap. In this sense, the aims of the present study were to analyse the pollination biology and breeding systems of these species, and to check for bilateral compatibility which could hinder reproductive isolation and species boundaries. Flower features such as yellow corolla, sweet scent and diurnal one-day anthesis were similar between species. However, they differed in nectar production patterns, which showed higher volume in A. nodosum and was irregular in A. peregrinum. The main pollinators for both species were medium to large Centridini bees. Many nectar and pollen robbers may disturb effective pollination and help to explain the low natural fruit-set. The species were self-sterile but pollen tube growth down to the ovules and differential ovary development indicated LSI, as in most Bignoniaceae studied to date, which reinforce the idea of family clustering for this self-incompatibility system. Fruit-set from interspecific hand pollinations was similar to those of intraspecific cross-pollinations, with high seed viability (88%) and seedling development. Similar floral biology and guild of pollinators, and bilateral inter-compatibility indicate that natural hybridization is possible among these species.

Reproductive systems and low outbreeding barriers between Jacaranda cuspidifolia and J. mimosifolia (Jacarandeae, Bignoniaceae)

“…Our microscopy analysis of post-pollination events indicates that the self-sterility observed in J. cuspidifolia is due LSI, as for the majority of outcrossing species of Bignoniaceae investigated to date (Bittencourt 2017, Gibbs 2014. Despite the effective fertilization of most ovules in self-pollinated pistils before their abscission, a delay in ovule penetration, fertilization and initial endosperm development were observed in these pistils in all analyzed post-pollination intervals, similar to those observed in J. racemosa (Bittencourt and Semir 2006) and other LSI species of Bignoniaceae (Gibbs and Bianchi 1999, Bittencourt et al 2003, 2011, Bittencourt and Semir 2005, Gandolphi and Bittencourt 2010, Sampaio et al 2016). These events are concurrent with a small but significant growth and a slightly extended longevity of the ovary in selfed pistils (compared with unpollinated pistils) up to their abscission, which seem to result from the delayed nature of selfed pistil rejection underlying the physiology LSI (Gibbs et al 2004, Bittencourt et al 2011, Bittencourt 2017.…”

“…Fruit set data from experimental pollinations in J. cuspidifolia indicated complete self-sterility (no fruit initiated from flowers tested for spontaneous (automatic) and induced (manual) self-pollination in six individuals). Despite the high ovule-seed conversion efficiency of compatible pollinations (including open pollination) in J. cuspidifolia, fruit set by natural pollination was remarkably lower than in cross-pollination in both species which implies their low reproductive efficacy, a common feature in most self-sterile species of Jancaranda (Vieira et al 1992, Guimarães et al 2008, Maués et al 2008, Milet-Pinheiro et al 2008, Sampaio 2010) and other Bignoniaceae (Bittencourt et al 2003, 2011, Bittencourt and Semir 2004, 2005, Gandolphi and Bittencourt 2010, Sampaio 2010, Alves et al 2013, Sampaio et al 2016) that may be related to pollen limitation and ovule discounting (Barrett 2002).…”

“…following effective self-pollen tube growth down to the ovary and penetration of most ovules) that typically results in null or almost null seed-set after full fertilization of ovules (Gibbs 2014). Ovule selfing after self-pollination in these species is followed by no embryo development and delayed (but structurally normal) ovary growth/endosperm initiation, which culminates in an assembled pistil abortion a short time after pollination relative to the regular period spent on fruit growth and maturation (Bittencourt et al 2003, 2011, Bittencourt and Semir 2005, Gandolphi and Bittencourt 2010, Sampaio et al 2016, Bittencourt 2017. In spite of numerous studies that have evidenced the occurrence of LSI in several taxa since its first description Bawa 1986, Sage et al 1994), this phenomenon has been neglected due to its similarity to early acting inbreeding depression (Gibbs 2014), especially in cases like those observed in Bignoniaceae where rejection of selfing operates post-zygotically.…”

The Influence of Fire and Deforestation on the Floral Symmetry and Fitness of Adenocalymma nodosun (Bignoniaceae)

“…In addition, our results support the idea of pollinators' preference for less asymmetrical flowers and a higher production of fruit (although not significant) in burned area than in the area of pruning. Sampaio et al (2016) mentions that the species A. nodusum has naturally low reproductive success, which is usually related to the limitation of pollen or ovule. In this sense, the presence of asymmetry could further reduce productivity.…”

“…Its leaves are petiolate, bi or tripinnate and imparipinnate, its leaflets are narrow and lanceolate, sessile when simple, petiolate when they are compound leaflets and the flowers arise in the axils of bracts (Sampaio et al, 2016). The plant species studied is important for the reproductive pollinating insects (Sampaio et al, 2016).…”