Pollination ecology in the tropical Andes: moving towards a cross-scale approach

Abstract

Plant-pollinator interactions structure ecological communities and represent a key component of ecosystem functioning. Pollination networks are expected to be more diverse and specialised in the tropics, but pollination ecology in these regions has been understudied in comparison to other areas. We reviewed research on pollination in the tropical Andes, one of the major biodiversity hotspots on Earth, where the uplift of mountains and past climate have resulted in spatiotemporally distinct species interactions. We found 1010 scientific articles on pollination in the Andes, of which 473 included or were carried out in tropical regions. The number of publications on pollination ecology in the tropical Andes has increased exponentially, with Colombia having the most articles, followed by Ecuador and Peru, and with Bolivia and Venezuela having notably fewer studies. More research has been carried out in humid montane forests and agricultural landscapes, and it has predominantly focused on describing diversity of species and interactions while neglecting analyses on the resilience and adaptability of pollinating systems, even though the Andean region is particularly susceptible to the effects of climate change and continues to undergo land conversion and degradation. Remarkably few studies have incorporated local knowledge, thus ignoring connections to human livelihoods and communities. A phytocentric perspective has been predominant, with fewer studies focusing directly on pollinators and a notable lack of articles with a holistic approach to the study of pollination across taxonomic groups at the community or ecosystem level. We propose that future research adopts a cross-scale approach that considers the complexity of the ecological contexts in which plant-pollinator interactions occur, and incorporates long-term monitoring with broader multilayer networks and molecular tools, experiments focused on ecophysiology and behaviour, animal telemetry, process-modelling approaches and participatory science. A stronger field driven by interdisciplinary collaborations will contribute to knowledge about pollination at a global scale, as well as increase our understanding of the diversity and resilience of pollination interactions in this region, thus improving our capacity to predict and avoid ecosystem collapses.

Keywords: South America; biotic interactions; ecological monitoring; ecosystem functioning; plant–pollinator networks; pollinators.

Fig. 1

Current and future land cover projections for the tropical Andes region. For this literature review, the tropical Andes region was defined as occurring north of the Tropic of Capricorn (23.4394° S), excluding areas in Chile and Argentina. (A) Current land cover for the region in 2020 at 1 km spatial resolution from the HILDA+ version 2b data set (Winkler et al., 2025). (B) Future land cover projections for 2100 under SSP5‐RCP8.5 (socioeconomic scenario of growth fuelled by fossil fuel consumption). (C) Projected areas of six land use and land cover classes from 2020 to 2100 under five socioeconomic scenarios (SSP1‐RCP2.6, sustainable development; SSP2‐RCP4.5, business as usual, SSP3‐RCP7.0, regional competition; SSP4‐RCP6.0, increased inequality, and SSP5‐RCP8.5, fossil fuels). Note that ‘Unmanaged grass/shrubs’ is equivalent to ‘Unmanaged grass/shrublands’ in the HILDA+ data set. The map for A and B was extracted from the GMBA Mountain Inventory (Snethlage et al., 2022a,b) and we added a 50 km buffer to include lowland areas that are still under Andean influence (e.g. inter‐Andean valleys and foothills). See Fig. S1 for projections by country.

Fig. 2

Photographs showcasing examples of plant–pollinator interactions in the tropical Andes. (A) Bombus rubicundus, a pollinator that is an important hub of interactions both within and between modules in plant–pollinator networks at high elevations, visiting rosetted plants (Espeletia grandiflora) endemic to paramos. (B) Two flies (left, Hirtodrosophila sp. and right, Zygothrica antedispar) attracted to the mushroom‐smelling orchid Dracula laffleurii. (C) Diurnal hawkmoth visiting flowers of Stachytarpheta cf. cayennensis, an exotic verbena flower popular in ornamental gardens. (D) Orchid bees of the genus Euglossa visiting flowers of Anthurium antioquiense, a plant endemic to the Central Cordillera of Colombia. (E) Solitary male bees of the genus Caenohalictus visiting a flower of the cactus Cumulopuntia sphaerica in mountainous desert shrubland, where these bees are frequent pollinators of cacti but have been largely understudied. (F) Stingless bee Melipona sp. in a sanctuary dedicated to meliponiculture, visiting a native aster, Cosmos sp., that is commonly used to attract insect pollinators to gardens and crops. (G) A male fly of Eudejeania sp. pseudocopulating with a flower of the sexually deceptive orchid Telipogon salinasiae. (H) Anoura fistulata, the nectar bat with the longest tongue relative to its body recorded for any mammal, drinking from the flowers of bromeliad Werauhia gladioliflora. (I) Phaethornis guy, a hermit hummingbird with a long, curved bill visiting Heliconia sp. by hovering. (J) Oxypogon guerinii, a hummingbird with a short, straight bill visiting Espeletia grandiflora by clinging to the flowers. (K) Nectar‐robbing by Diglossa cyanea through holes it pierces in the base of the corolla of an exotic Kniphofia sp. (L) Nectar‐robbing by Aglaiocercus kingii from Fuchsia sp., using holes previously made by flowerpiercers. Photographs by Laura Milena Manrique‐Garzón (A), Lorena Endara (B), Diego Emerson Torres (C), Daniel Salazar Rios (D), Yeison Calizaya Melo (E), José Isidro Vargas (F), Carlos Martel (G), Nathan Muchhala (H), and Pedro A. Camargo‐Martínez (I–L).

Fig. 3

Geographic, temporal, thematic, and taxonomic distribution of research on pollination ecology in the tropical Andes. (A) Density of articles about pollination in the tropical Andes according to study site elevation in metres above sea level (m a.s.l.), with the green curve showing lower bounds and the blue curve showing the upper bounds of study locations. When studies were carried out at a single elevation, the lower and upper bounds are the same. Dashed lines indicate elevations of capital cities in tropical Andean countries, with the addition of Cusco, which was the capital of the Inka empire. Note that Caracas and Lima are not located in the Andes. The same plot by country is available in Fig. S3. (B) Accumulated total publications through time for each tropical Andean country. Studies with a continental approach (i.e. encompassing several countries and aiming for broad spatial coverage) are classified as ‘continental’. (C) Number of publications according to major research themes (top panel) and taxonomic groups (bottom panel). ‘Diversity’ refers to functional, genetic and species diversity. Studies that were not focused on a single group but rather studied pollination as a whole are classified as ‘General’.

Fig. 4

Natural and anthropogenic ecosystem types where research on pollination ecology has been conducted in the tropical Andes. Ecosystem types were extracted from publications that described the ecosystem where they were carried out (359 publications) and are classified as shown in the legend, based on the map of South America ecosystems provided by The Nature Conservancy (2008) (see Table S2) and adding three anthropogenic categories: agriculture (croplands and pastures), forestry and urban areas. We removed one very early study (1950, in agricultural ecosystem type in Peru) to ease visualisation. See Fig. S4 for plots by country.

Fig. 5

Relationships among major research themes, taxonomic groups and main methods used in the scientific literature on pollination ecology in the tropical Andes. Thickness of lines is proportional to the number of studies, with a line being drawn each time a major theme (left) or method (right) is included in a study, so several lines can be drawn if a study has more than one theme or method. Colours indicate taxonomic groups: plants (green), arthropods (lilac), birds (pink), mammals (yellow), and a general (black) approach to pollination (i.e. not focused on taxonomic groups). ‘Diversity’ refers to functional, genetic and species diversity; SDM = species distribution model; ‘Morphometrics’ and ‘Phenology’ include plant and pollinator morphometrics and phenology, respectively; ‘Other’ includes several other methods (Table S1). A histogram of studies by method is available in Fig. S5.

Fig. 6

A cross‐scale approach to the study of pollination ecology. Pollination includes key players that range from the level of molecules, genes and microorganisms (A) to the web of interactions of communities (B) and landscapes across elevation gradients and geographic regions (C). (A) Circles highlight microscopic factors that can influence pollination, including volatile molecules that attract pollinators to flowers, microorganisms resident in the soil or plant organs, and the genes of both plant and pollinator partners. (B) Web of interactions at the community level, with orange lines showing floral visitors as potential pollinators, and white lines showing fruit development and seed dispersal. Dashed lines indicate additional biotic interactions within (blue) and between (yellow) species, such as direct competition (hummingbirds in territorial dispute), and indirect competition (fly and bee feeding on nectar, shrubs competing for light under the canopy), predation (owl hunting hummingbird), and interaction antagonism (phoretic mite on hummingbird competing for flower nectar). The honeybee is in a pink circle to depict invasive species. (C) Landscape configurations of habitats within and across elevational bands, which can also be approached at large continental scales. Colours indicate different habitat types, black dashed lines show movement within or between habitat patches and white dashed lines indicate movement across elevations. Note that illustrations are not to scale, and they represent functional groups rather than species. Figure created in BioRender (https://BioRender.com/o34w763).

Fig. 7

Variation of monitored interaction networks across elevations. Monitoring is part of the GLORIA‐Andes project in Piedras Blancas, Parque Nacional La Culata, Venezuela at 4200, 4400 and 4600 m above sea level (a.s.l.). All networks are highly specialised and have marked seasonal fluctuations, but the two lowest summits have similar species richness and structural indices compared to the highest site. Across sites, probabilities of interactions are linked to plant species occurrence, plant phenology and sampling effort. Nodes on the left side of networks indicate visited plants and nodes on right show pollinators, with colours indicating different taxonomic groups as shown in the legend. Thickness of connecting lines show frequency of visits and size of nodes represent degree centrality. Figure adapted from Pelayo et al. (2021).

Fig. 8

Experimental approach to simulate climate change with open‐top chambers (OTCs). OTCs set up in the Paramo Sumapaz in Colombia at 3500 m above sea level (a.s.l.) (A) and in the Paramo in the Antisana Volcano in Ecuador at 4580 m a.s.l. (B). Photographs by Eloisa Lasso.

Fig. 9

Automated radio telemetry system to track movement of pollinators in high‐Andean ecosystems. (A) Map of grid set up in the Valle de los Frailejones in Chingaza National Park, Colombia, with 46 receiving nodes (white points) and main antenna (pink flag). (B) Set‐up of the main antenna 10 m above the ground. Data are received from nodes in the valley by receiving yagi antennas (i) and downloaded using the Cellular Tracking Technologies (CTT) SensorStation (ii). Power is supplied to the system from a marine deep cycle battery (iii) that has additional charge from a solar panel (iv). (C–E) Birds with attached CTT LifeTags radio transmitters: (C) great sapphirewing (Pterophanes cyanopterus) with a hummingbird harness; (D) masked flowerpiercer (Diglossa cyanea) with a leg loop harness; and (E) sparkling violetear (Colibri coruscans) with glue‐on tag. Map made using Google Earth and photographs by Cristina Rueda‐Uribe (B, E), Manuela Lozano (C), and Pedro A. Camargo‐Martínez (D).

Fig. 10

Examples of nature‐based solutions and research involving local communities. Activities carried out in El Zoque Nature Reserve in the Eastern Cordillera of Colombia include (A) a plant nursery with slow‐growing Puya sp. bromeliads of the paramo, experimenting with different growing techniques and employing local people; (B) active restoration efforts with community training; (C) farmers and nature guides sharing produce from goat milk as a productive alternative to dairy cows; and (D) an artistic mural made by young community leaders of a charismatic plant–pollinator interaction of the region (flowers of stem rosette Espeletia grandiflora and green‐bearded helmetcrest, Oxypogon guerinii). Photographs by Mauricio Restrepo (A, B) and Cristina Rueda‐Uribe (C, D).