Forest connectivity boosts pollen flow among populations of the oil-producing Nierembergia linariifolia

Abstract

The process of forest fragmentation determines landscapes with isolated forest patches immersed in a distinct matrix. This process may hinder pollinator movement throughout the landscape, which may negatively impact on pollen flow among native plant populations. Objectives: We evaluated the effect of the loss of forest connectivity on pollen dispersal by specialized native bees in the oil-producing and self-incompatible Nierembergia linariifolia. Methods: We estimated pollen flow between plants of N. linariifolia at an agroecosystem with remnant forest of central Argentina. Six plant populations (source populations) were treated with fluorescent dyes as pollen analogues, and stigmata of recipient plants were collected to seek for dye particles. Dye deposition rate was assessed for plants that were connected through remnant forest to a source population or unconnected by a crop matrix, and at increasing distances to a source population. Results: Deposition rate per plant was higher in connected than in unconnected plants, and decreased with increasing distances to a source population in an exponential fashion. Most of the dispersal events between connected plants occurred at the vicinity of a source population. Long dispersal events (up to 1259 m) were recorded between plants located at neighbouring forest patches separated by an agricultural matrix. Conclusions: Landscape connectivity through forest remnants is key to enhance pollen flow between self-incompatible plants such as N. linariifolia. Besides, the evidence of pollen dispersal through the agricultural matrix pinpoints the essential role of native pollinators in maintaining pollen flow among unconnected plant populations in fragmented landscapes.