Tropical Forest Fragmentation Limits Movements, but Not Occurrence of a Generalist Pollinator Species

Abstract

Habitat loss and fragmentation influence species distributions and therefore ecological processes that depend upon them. Pollination may be particularly susceptible to fragmentation, as it depends on frequent pollinator movement. Unfortunately, most pollinators are too small to track efficiently which has precluded testing the hypothesis that habitat fragmentation reduces or eliminates pollen flow by disrupting pollinator movement. We used radio-telemetry to examine space use of the green hermit hummingbird (Phaethornis guy), an important ‘hub’ pollinator of understory flowering plants across substantial portions of the neotropics and the primary pollinator of a keystone plant which shows reduced pollination success in fragmented landscapes. We found that green hermits strongly avoided crossing large stretches of non-forested matrix and preferred to move along stream corridors. Forest gaps as small as 50 m diminished the odds of movement by 50%. Green hermits occurred almost exclusively inside the forest, with the odds of occurrence being 8 times higher at points with >95% canopy cover compared with points having <5% canopy cover. Nevertheless, surprisingly. the species occurred in fragmented landscapes with low amounts of forest (~30% within a 2 km radius). Our results indicate that although green hermits are present even in landscapes with low amounts of tropical forest, movement within these landscapes ends up strongly constrained by forest gaps. Restricted movement of pollinators may be an underappreciated mechanism for widespread declines in pollination and plant fitness in fragmented landscapes, even when in the presence of appropriate pollinators.

Land use change has stronger effects on functional diversity than taxonomic diversity in tropical Andean hummingbirds

“…Some hummingbird species have daily movements of more than 1 km (Hadley & Betts, ) and may exploit resources across different land cover types; for example, a recent study by Volpe et al. () found that the presence of the hummingbird Phaethornis guy in small forest patches is highly dependent in the connectivity of the native forest at the landscape scale. Thus, the use of different land cover types in a landscape may undermine negative effects of land use change at small local scales for many hummingbird species.…”

“…In addition, the strong association found between all three landscape factors and hummingbird functional diversity suggests that relationship between local-scale factors and hummingbirds might be largely dependent on the landscape context (Renjifo, 2001;Tscharntke et al, 2012). Some hummingbird species have daily movements of more than 1 km (Hadley & Betts, 2009) and may exploit resources across different land cover types; for example, a recent study by Volpe et al (2016) found that the presence of the hummingbird Phaethornis guy in small forest patches is highly dependent in the connectivity of the native forest at the landscape scale. Thus, the use of different land cover types in a landscape may undermine negative effects of land use change at small local scales for many hummingbird species.…”

Forest fragmentation and loss reduce richness, availability, and specialization in tropical hummingbird communities

“…We separately quantified the landscape composition of these 14 landscapes within two distances surrounding the focal patch representing roughly one (500 m) and two times the radius (1000 m) of species thought to have among the largest home ranges in the system (Volpe et al . ). Composition metrics included the amount of mature tropical forest, regenerating forest (1–3 m tall), agricultural land (primarily coffee/banana plantations), and pasture (Fig.…”

Consequences of Habitat Fragmentation on the Reproductive Success of two Tillandsia species with Contrasting Life History Strategies

“…This change in relative visitation frequencies among pollinator species—only observed for T. intermedia —may be the result of different factors: (i) the populations of certain groups of floral visitors, such as Euglossine bees, are often negatively impacted by habitat loss or fragmentation (e.g. Storck-Tonon and Peres 2017); (ii) the movement of animal pollinators may be constrained by open spaces in fragmented habitats (Volpe et al 2016); and (iii) pollinator behaviour may change along with vegetation structure and floral resources after fragmentation (Goverde et al 2002; Hadley and Betts 2009). In this study, Euglossine bees did not visit Tillandsia flowers in forest fragments, and hummingbirds changed their frequencies according to habitat condition in T. intermedia .…”