Ants contribute to pollination but not to reproduction in a rare calcareous grassland forb

Abstract

The number of plants pollinated by ants is surprisingly low given the abundance of ants and the fact that they are common visitors of angiosperms. Generally ants are considered as nectar robbers that do not provide pollination service. We studied the pollination system of the endangered dry grassland forb Euphorbia seguieriana and found two ant species to be the most frequent visitors of its flowers. Workers of Formica cunicularia carried five times more pollen than smaller Tapinoma erraticum individuals, but significantly more viable pollen was recovered from the latter. Overall, the viability of pollen on ant cuticles was significantly lower (p < 0.001)—presumably an antibiotic effect of the metapleural gland secretion. A marking experiment suggested that ants were unlikely to facilitate outcrossing as workers repeatedly returned to the same individual plant. In open pollinated plants and when access was given exclusively to flying insects, fruit set was nearly 100%. In plants visited by ants only, roughly one third of flowers set fruit, and almost none set fruit when all insects were excluded. The germination rate of seeds from flowers pollinated by flying insects was 31 ± 7% in contrast to 1 ± 1% resulting from ant pollination. We conclude that inbreeding depression may be responsible for the very low germination rate in ant pollinated flowers and that ants, although the most frequent visitors, play a negligible or even deleterious role in the reproduction of E. seguieriana. Our study reiterates the need to investigate plant fitness effects beyond seed set in order to confirm ant-plant mutualisms.

Reproductive isolation between wild and domesticated chaya (Cnidoscolus aconitifolius) in sympatry

“…However, the fact that one of two shared pollinators was an ant (which are often nectar thieves; e.g. Rost as et al 2018) and also that the flowers of the cultivated plants were visited far less frequently, leads us to conclude that pollen transfer from wild to cultivated plants is low.…”

“…Since the reproductive organs are anatomically normal, this mutation probably affects pollen production during meiosis (e.g. Saumitou-Laprade et al 1994). The lack of pollen is not consciously selected; rather, it is probably genetically correlated with other plant traits that are being artificially selected (Mungu ıa-Rosas et al 2019).…”

Pollen adaptation to ant pollination: a case study from the Proteaceae

“…Most animals involved in such interactions are insects, and they account for the pollination of ~88 % of all animal-pollinated plants ( Potts et al , 2010 ; Thomann et al , 2013 ). Among the insect-pollinated plants, pollination by ants appears to be poorly represented ( de Vega and Gómez, 2014 ; Kuriakose et al , 2018 ; Rostás et al , 2018 ; Del-Claro et al , 2019 ), whereas bees and other close relatives are recognized as important pollinators worldwide ( Potts et al , 2016 ). Moreover, interactions between ants and flowers are generally assumed to be antagonistic.…”

Pollination effectiveness in a generalist plant: adding the genetic component

“…Genetically diverse pollen loads provide the appropriate environments for pollen competition (Marshall & Folsom, 1991;Marshall et al, 2007), influencing the quality component of effectiveness in multiple ways. For example, it can increase the number of fertilized ovules by enhancing the germination of compatible pollen (Montalvo, 1992) and the production of more vigorous offspring (G omez, 2000;Herrera, 2000;Rost as et al, 2018). Moreover, it also can result in multiple paternity within the same fruit (Ellstrand, 1984).…”