Abstract
Pollinators can be a limited resource and natural selection should favour differences in phenotypic characteristics to reduce competition among plants. Bats are important pollinators of many Neotropical plants, including the Bromeliaceae; however, the pre-pollination mechanisms for isolation among sympatric bat-pollinated bromeliads are unknown. Here, we studied the mechanisms for reproductive segregation between Pitcairnia recurvata, Pseudalcantarea viridiflora, Werauhia noctiflorens and W. nutans. The study was conducted at Los Tuxtlas Biosphere Reserve, in Veracruz, Mexico We carried out ex situ and in situ manual pollination treatments to determine the breeding system by assessing fruiting and seedling success and sampled bat visitors using mist-nets and infrared cameras. We determined the nocturnal nectar production pattern, estimating the energetic content of this reward. All four bromeliads are self-compatible, but only P. recurvata appears to require pollinators, because the physical separation between anthers and stigma prevents self-pollination, it is xenogamous and presents a strictly nocturnal anthesis. The bats Anoura geoffroyi, Glossophaga soricina and Hylonycteris underwoodi are probable pollinators of three of the studied bromeliads. We did not record any animal visiting the fourth species. The flowering season of each species is staggered throughout the year, with minimal overlap, and the floral morphology segregates the locations on the body of the bat where the pollen is deposited. The most abundant nectar per flower is provided by P. viridiflora, but P. recurvata offers the best reward per hectare, considering the density of flowering plants. Staggered flowering, different pollen deposition sites on the body of the pollinator and differences in the reward offered may have evolved to reduce the competitive costs of sharing pollinators while providing a constant supply of food to maintain a stable nectarivorous bat community.
Highlights
Zoophilous pollination has been important for the evolution and diversification of angiosperms (Hu et al 2008), with nearly 90 % of the extant angiosperms presenting this form of pollination (Ollerton et al 2011)
The aim of this paper is to study the floral phenology, pollinators and floral rewards of four sympatric bromeliads, which belong to three different genera Pitcairnia, Pseudalcantarea and Werauhia
Pitcairnia recurvata initiated flowering in mid-May and flowered until mid-July
Summary
Zoophilous pollination has been important for the evolution and diversification of angiosperms (Hu et al 2008), with nearly 90 % of the extant angiosperms presenting this form of pollination (Ollerton et al 2011). Many plant species use a variety of different animals as pollinators (Waser et al 1996; Ollerton et al 2009). Evolution should favour adaptations that act to reduce heterospecific pollen deposition (Ashman and Arceo-Gómez 2013) as well as pollen misplacement during the visits to foreign stigmas (male fitness component; Morales and Traveset 2008; Muchhala et al 2010). In this sense, sharing pollinators could promote a divergence in phenotypic characteristics related to attracting pollinators (Feinsinger 1987; Muchhala and Thomson 2012). Pollinator sharing could be advantageous to the plant community, since co-flowering plants could attract and maintain local populations of pollinators over the course of the year (facilitation; Schemske 1981; Moeller 2004; Ghazoul 2006; Sargent and Ackerly 2008)
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