Consequences of habitat fragmentation on the reproductive success of two Tillandsia species with contrasting life history strategies

Fragmentation of natural habitats generally has negative effects on the reproductive success of many plant species; however, little is known about epiphytic plants. Epiphytes are non-parasitic plants that grow on other plants and they represent almost 10 % of vascular plant species. They are particularly important to tropical forest ecosystems due to their high taxonomic and functional diversity, and their roles in supplying nutrients, water and shelter for other organisms. Epiphytes are considered to be highly sensitive to habitat disturbance because they have low growth rates, delayed sexual maturity, limited seed dispersal, and no seed bank.

A recent study by Sáyago et al. published in AoBP assessed the impact of habitat fragmentation on plant-pollinator interactions and reproductive success of two epiphytic Mexican Tillandsia species over three years. The two study species, T. intermedia and T. makoyana, differ in life history strategies (monocarpic vs. polycarpic respectively), yet share pollinators and have similar flowering seasons. Pollinator assemblages differed between fragmented and continuous habitats for T. intermedia. Hummingbirds, the most important pollinators of both Tillandsia species, were however effective under both habitat conditions reflecting their ability to easily move across human-modified landscapes. T. makoyana had a lower seed set under fragmented conditions, suggesting that differences in pollination quality (i.e. amount and quality of pollen deposited onto stigmas) exist between habitat conditions. Changes in plant reproductive systems and pollinator assemblages resulting from habitat fragmentation may have further undocumented consequences on gene flow, levels of inbreeding and progeny quality of these dry forest Tillandsia species. The results of this study highlight the need for further research into the impacts of habitat fragmentation on epiphytic species, as even these closely related Tillandsia species show contrasting responses to human disturbance.