Plant–pollinator interactions in a Mexican Acacia community

Abstract

Competition for pollination is thought to be an important factor structuring flowering in many plant communities, particularly among plant taxa with morphologically similar and easily accessible flowers. We examined the potential for heterospecific pollen transfer (HPT) in a community of four Acacia species in a highly seasonal tropical habitat in Mexico. Partitioning of pollen flow among sympatric species appears to be achieved, in part, through segregation of flowering in seasonal time, and interspecific differences in pollinator guilds. However, two coflowering species (Acacia macracantha and Acacia angustissima) shared multiple flower visitors, raising the possibility of HPT. Each of these coflowering species showed high intraspecific daily synchrony in pollen release, but dehisce at different times of day. Pollinators rapidly harvested available pollen from one species before abandoning it to visit the flowers of the second later in the day. The activity of shared pollinators, predominantly bees, is thus structured throughout the day, and potential for HPT reduced. Suggestive evidence in favour of a resource partitioning explanation for this pattern is provided by the fact that A. macracantha showed significantly greater intraspecific synchrony when coflowering with a potential competitor (A. angustissima) than when flowering alone. We discuss our results in light of previous work on coflowering acacia assemblages in Tanzania and Australia.

Do climatic and habitat conditions affect the reproductive success of an invasive tree species? An assessment of the phenology of Acacia longifolia in Portugal

“…6a, b). Recent findings indicate that an extended flowering period is a trait correlated with the invasiveness potential of exotic species, thus increasing their competitiveness for pollinators (Raine et al 2007) and may help mitigate pollinator limitation (Gibson et al 2011). We did not evaluate plant-insect relations in this study but it is well known that acacia flowers, including A. longifolia, do not require a highly specific relationship with specific pollinators (Stone et al 2003).…”

Daily temporal structure in African savanna flower visitation networks and consequences for network sampling

“…(See also Stone et al [1996Stone et al [ , 1998 for similar patterns for a set of acacia species in Tanzania.) Timing of pollen release in acacias and other plants is sensitive to microclimate and can vary at the same site between days, with knock-on effects on the activity of associated pollinators (e.g., Stone et al 1998, Raine et al 2007. Which component of the visitor community for S. brevispica is detected will thus depend on when it is observed.…”

“…For pollinators such as bees that regularly remove pollen from their bodies, daily temporal partitioning of visitation among coflowering plants can turn a potentially negative interaction (competition for pollination) into a positive interaction (facilitation of fruit set) (Armbruster and Herzig 1984, Stone et al 1998, Raine et al 2007). Which of these scenarios holds generates diametrically opposing predictions of the impact of species gain (by invasion or habitat restoration) or loss (by extinction).…”

An evaluation of physical and mechanical scarification methods on seed germination of Vachellia macracantha (Humb. & Bonpl. ex Willd.) Seigler & Ebinger

“…An important trait of this species is root nodule formation, which implies the presence of Ensifer or Rhizobium rhizobacteria, which are highly effective in fixing nitrogen (Cordero, Ruiz, de la Peña, Balaguer, Lucas, Rincón & Pueyo, 2016). The flowers of these trees are important for recruiting different pollinators, predominantly bees (Raine, Pierson & Stone, 2007). Additionally, the canopy hosts numerous insects that draw migratory birds, making V. macrantha a viable option for conservation.…”