Effect of invader removal: pollinators stay but some native plants miss their new friend

Abstract

Removal of invasive species often benefits biological diversity allowing ecosystems' recovery. However, it is important to assess the functional roles that invaders may have established in their new areas to avoid unexpected results from species elimination. Invasive animal-pollinated plants may affect the plant-pollination interactions by changing pollinator availability and/or behaviour in the community. Thus, removal of an invasive plant may have important effects on pollinator community that may then be reflected positive or negatively on the reproductive success of native plants. The objective of this study was to assess the effect of removing Oxalis pescaprae, an invasive weed widely spread in the Mediterranean basin, on plant-pollinator interactions and on the reproductive success of co-flowering native plants. For this, a disturbed area in central Portugal, where this species is highly abundant, was selected. Visitation rates, natural pollen loads, pollen tube growth and natural fruit set of native plants were compared in the presence of O. pes-caprae and after manual removal of their flowers. Our results showed a highly resilient pollination network but also revealed some facilitative effects of O. pes-caprae on the reproductive success of co-flowering native plants. Reproductive success of the native plants seems to depend not only on the number and diversity of floral visitors, but also on their efficiency as pollinators. The information provided on the effects of invasive species on the sexual reproductive success of natives is essential for adequate management of invaded areas. Keywords Biological invasions Á Competition Á Facilitation Á Mutualistic relationships Á Oxalis pescaprae Á Plant-pollinator networks Electronic supplementary material The online version of this article (

Exotic Plant Species in the Mediterranean Biome: A Reflection of Cultural and Historical Relationships

“…Moreover, facilitative effects on the reproductive success of co-flowering native plants have been reported in the presence of the invasive weed Oxalis pescaprae [150]. Likewise, it has been shown that litter of invasive exotic plants facilitated growth of the dominant native plants by altering soil moisture in Californian shrublands [151].…”

“…Therefore, eradication programmes to re-establish the original vegetation might provoke severe local extinction of endemic species [127,154], population bottlenecks, and cascading effects across trophic levels [126,155], as well as on pollinator communities [150]. Some exotic species can contribute to achieve native species conservation policies [133]; sometimes, even the employment of exotic species has been proposed as an effective action for ecological restoration [156,157].…”

Two invasive acacia species secure generalist pollinators in invaded communities

“…Invasive plants tend to be pollinated by generalist insects both in their native and nonnative ranges (Chrobock et al, 2013;Gibson et al, 2011;Gotlieb et al, 2011;Lopezaraiza-Mikel et al, 2007;Padr on et al, 2009), and often offer large floral displays and floral rewards which can influence pollinator behaviour and preferences and thus affect the surrounding plant community either positively, by attracting shared pollinators to the site, neutrally, or negatively, by competing for pollination services (Moragues and Traveset, 2005;Larson et al, 2006;Bartomeus et al, 2008). Such effects are often speciesspecific, and invasive plants can benefit some native species while harming others in the same community (Ferrero et al, 2013;Moragues and Traveset, 2005). In any case, the presence of invasive species has the potential to influence pollinator species composition and relative abundance, influencing pollination efficiency and reproductive success of native plants (Ferrero et al, 2013;Gibson et al, 2012;Gotlieb et al, 2011;Lopezaraiza-Mikel et al, 2007).…”

Invasive plants as drivers and passengers of community change in a disturbed urban forest.

“…In some situations, invasive species may have the potential to maintain ecosystem function lost due to habitat disturbance or degraded habitat. For example, invasive Oxalis pes-caprae in the Mediterranean basin has some facilitative effects on native pollination, and removal of this species decreased pollinator efficiency and reproductive output in native plants (Ferrero et al 2013). The invaded sites in our study are highly disturbed by frequent flooding and urban run-off, and no native ephemerals occur directly in the riparian area with R. ficaria.…”