Relative Stability of Core Groups in Pollination Networks in a Biodiversity Hotspot over Four Years

Abstract

Plants and their pollinators form pollination networks integral to the evolution and persistence of species in communities. Previous studies suggest that pollination network structure remains nested while network composition is highly dynamic. However, little is known about temporal variation in the structure and function of plant-pollinator networks, especially in species-rich communities where the strength of pollinator competition is predicted to be high. Here we quantify temporal variation of pollination networks over four consecutive years in an alpine meadow in the Hengduan Mountains biodiversity hotspot in China. We found that ranked positions and idiosyncratic temperatures of both plants and pollinators were more conservative between consecutive years than in non-consecutive years. Although network compositions exhibited high turnover, generalized core groups – decomposed by a k-core algorithm – were much more stable than peripheral groups. Given the high rate of turnover observed, we suggest that identical plants and pollinators that persist for at least two successive years sustain pollination services at the community level. Our data do not support theoretical predictions of a high proportion of specialized links within species-rich communities. Plants were relatively specialized, exhibiting less variability in pollinator composition at pollinator functional group level than at the species level. Both specialized and generalized plants experienced narrow variation in functional pollinator groups. The dynamic nature of pollination networks in the alpine meadow demonstrates the potential for networks to mitigate the effects of fluctuations in species composition in a high biodiversity area.

Effective pollinia transfer by settling moths’ legs in an orchid Habenaria aitchisonii

“…Pollinator visits to flowers were observed in the field from July to August in 2012 and 2013. In the daytime, pollinators were observed for more than 20 h from 10:00 to 17:00 on sunny days (see Fang & Huang, , ). Night‐time observations took place from 18:30 to 22:00; one observer focused on a plot containing approximately 10 flowering individuals.…”

Evaluation of pollinator effectiveness based on pollen deposition and seed production in a gynodieocious alpine plant, Cyananthus delavayi

“…This study was conducted at Shangri‐La Alpine Botanical Garden (27°54′5″N, 99°38′17″E, 3300–3350 m above sea level), Yunnan Province, southwest China, in 2016. In the study population, flowers of Pedicularis species were common in the meadow, and Astragalus pullus , Halenia elliptica , and some Apiaceae species were less abundant (Fang & Huang, ).…”

Geographical variation in mutualistic networks: similarity, turnover and partner fidelity

“…This was repeated 1000 times, and z-scores (used as a proxy for deviation from randomness) were calculated for each species as (Sor emp 2 Sor rand )/Sor SD , where Sor rand and Sor SD are mean and standard deviations of partner fidelities achieved from the 1000 random assortments of partners, respectively. Taxonomic resolution of partners (species, genus, family or order) probably influences level of partner similarity [23,33]. For comparison, we therefore resolved partners of plants to species, genus, family and order, and partners of pollinators to species and family.…”

“…Fang & Huang [23] found that plants tended to interact with the same functional groups of pollinators over a 4-year period, and in a meta-analysis, Rosas-Guerrero et al [33] found evidence for pollination syndromes-both suggestive of some level of partner fidelity at a higher hierarchical level. Working at species level, we found that 95% of the plant species and half of the pollinators showed partner fidelities (i.e.…”