Honeybees facilitate the invasion of Phyla canescens (Verbenaceae) in Australia – no bees, no seed!

Abstract

Several environmental weeds rely on the pollination services of introduced bees. The transfer of this knowledge to weed control management has not been fully explored. In part, this may be because it is difficult to quantify the economic impact of environmental weeds. This diminishes the prospects for expensive research and development required for integrated weed management. In this study, we examine the reproductive ecology of Phyla canescens, a species native to South America that is an aggressive agricultural and environmental weed in many parts of the world. We found that P. canescens is self-compatible, but not capable of automatic selfpollination. A vector is required to effect seed set. Field studies showed that 45% of seeds produced through open pollination are viable. Using exclosure cages, we showed that non-native Apis mellifera L. (honeybee) was the primary floral visitor and pollinator. Honeybee abundance was positively correlated with P. canescens abundance. Within the study site of 0.51 ha, almost 500 000 seeds ha )1 would be produced annually, as a result of honeybee pollination. This study shows that a shared evolutionary history is not required for honeybees to be successful pollinators. Facilitation is demonstrated through the obligate need for pollinators and the successful recruitment of the species through seed. Models for the control of feral honeybees in agricultural systems require development.

Decreased insect visitation to a native species caused by an invasive tree in the Cape Floristic Region

“…Additional measurements of the effect of A. saligna on interspecific pollen transfer within native communities, and its effect on seed set in native species, are needed. Furthermore, honeybees are generalist foragers that can facilitate the invasion of flowering alien plants (Gross et al, 2010), and more research is needed to determine their contribution to A. saligna pollination and reproductive success. …”

“…Our results also concur with a growing body of Table 1 Study site locations, focal species, and floral display metrics used in this study. Statistic and p values for comparing vegetation parameters between invaded and uninvaded plots can be found in Appendix D. Fabaceae n/a n/a n/a n/a n/a n/a 18°44.6E literature reporting the importance of honeybees in the pollination and spread of invasive flowering plants ( Barthell et al, 2001;Gross et al, 2010;Richardson et al, 2000a;Stout et al, 2002). Our observations of the broad spectrum of visitors to A. saligna adds support for the idea that the spread of invasive plant species is often not limited by a lack of suitable pollinators (Richardson et al, 2000a).…”

The Phylogeny and Biogeography of Phyla nodiflora (Verbenaceae) Reveals Native and Invasive Lineages throughout the World

“…data, 2006 whereas P. canescens is not capable of autogamous seed production, [18]). Our research has found that there is little geographic overlap in the species in either the native or Australian range (Figure 2) [17] respectively.…”

“…Their distinction was based on leaf shape, leaf size, leaf apex characters and leaf indumentum. In this paper we follow the taxonomy of Kennedy [6] and Munir [8] because (i) the species are morphologically distinctive [6,8,17] ( Figure S1a,b); (ii) they appear to have a mostly non-overlapping distribution in their native range [6] and Australia [6,17]; (iii) have distinctive climatic preferences [8,17] and (iv) the species vary in their breeding biology (Fatemi, unpub data, see below; [18]). Table 1.…”

“…Greene. Phyla canescens is a highly invasive herb in Australia [18,[47][48][49] whereas P. cuneifolia, P. fructicosa and P. lanceolata are not listed as occurring in Australia (Australia's Virtual Herbarium, accessed 26 February 2017). The taxa outside of Australia with the closest native range to P. nodiflora include the Latin American P. canescens, P. betulifolia (Kunth) Greene and P. fructicosa (= P. nodiflora var.…”