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Floral nectaries are essential for plant reproduction but little is known about the relationship between these secretory structures and pollination system in cacti. To test phenotypic patterns in nectaries associated with pollination syndromes and/or with its pollinators, we selected from evolutionarily related genera Cleistocactus, Denmoza, and Echinopsis, a set of species with bird-pollinated flowers and floral traits that may fit with ornithophily or with sphingophily, and other set of sphingophilous species with moths as effective pollinator. Observations were made under light microscope and scanning and transmission electron microscopes. Nectaries are located at the base of the filaments welded to the tube, forming a chamber. The nectary consists of the epidermis with distinctive features in each genus, a secretory parenchyma which may be vascularized and a non-secretory vascularized parenchyma. Anatomical variants observed in nectaries of different species are not consistent with the floral pollination syndromes neither with groups of pollinators. The basic structure of the nectar chamber is relatively conserved, a fact that may be explained by phylogenetic conservatism among the genera investigated. Our results revalue the role of anatomical traits for the systematics of Cactaceae.

Abstract Climate change can disrupt mutualisms by causing temporal or spatial mismatch between interacting species. However, the effects of climate change forecasts on biotic interactions remain poorly studied. In cactus species, pollination constitutes a fundamental process in the production of fruits and seeds. Thus, we aimed to analyse the impact of future climate change on the geographical distributions of 11 cactus species from the southern Central Andes and their spatial match with their pollinators. We used species distribution modelling to forecast the geographic range shifts of these cactus species and their pollinators under two future scenarios (RCP 4.5 and RCP 8.5) for the years 2050 and 2070. We predicted geographic range contractions under future scenarios that reached almost 80% for some cactus species. Our results indicate that the geographical distributions of cacti would be constrained by the presence of the pollinator species on which they depend in the present; however, climate change would not cause spatial mismatch between cacti and their animal pollinators in the future. For most cactus species, we predicted an increase in the spatial match with their mutualists under future scenarios. This is the first study that estimates the geographic range of cacti using both abiotic and biotic factors. Given the importance that positive interactions have on the life cycle of many plant species, our approach could be used to better understand the potential effects of climate change, particularly on species that are of special interest for conservation actions. Highlights • We estimate the geographic range of cacti using both abiotic and biotic factors. • The current range of cacti would be constrained by the presence of their pollinators. • Severe geographic range contractions were predicted under future climate scenarios. • Climate change would not cause spatial mismatch between cacti and their pollinators in the future. [ABSTRACT FROM AUTHOR]

Cactus flowers have traditionally been considered to be specialized to certain pollination guilds, but pollination studies reveal that most species are actually generalists. This suggests that floral traits are not always predictive of the animal visitors that pollinate cactus flowers. Here, we studied the pollination of Echinopsis leucantha (Gillies ex Salm-Dyck) Walp., an endemic cactus of Argentina, whose floral traits would suggest that it is pollinated by moths. The floral lifespan and flower availability throughout the reproductive period were evaluated. Field experiments were carried out to study the reproductive system and the identity and effectiveness of floral visitors. Echinopsis leucantha flowers had a nocturnal anthesis time that extended into the following morning. The species was self-incompatible. Floral visitors included moths, bees, and passerine birds. However, diurnal visitors were more effective as pollinators than nocturnal ones. The flowers of E. leucantha were phenotypically specialized (sphingophily); however, the pollination system was functionally and ecologically generalized. The results confirm that generalized pollination systems are widespread among species of the Echinopsis genus with nocturnal flowers, for which diurnal pollinators seem to have a key role in fruit and seed production. Our study constitutes the first record of passerine bird pollination in the Cactaceae for mainland South America. [ABSTRACT FROM AUTHOR]