Background Sympatric congeneric plants might share pollinators, or each species might avoid competition by evolving specialized traits that generate partitions in pollinator assemblages. In both cases, pollen limitation (a decrease in the quality and quantity of compatible reproductive pollen) can occur, driving the plant mating system to autogamy as a mechanism of reproductive assurance. We assessed the relationships between pollinator assemblages and mating systems in a group of sympatric congeneric plants. We attempted to answer the following questions: (i) How similar are pollinator assemblages among sympatric cactus species? (ii) Which mating systems do sympatric cactus species use? Methods We studied sympatric Eriosyce taxa that inhabit a threatened coastal strip in a mediterranean-type ecosystem in central Chile. We performed field observations on four taxa and characterized pollinators during the years 2016 and 2017. We estimated differences in the pollinator assemblages using the Bray–Curtis index. To elucidate the mating systems, we conducted hand-pollination experiments using three treatments: manual cross-pollination, automatic self-pollination, and control (unmanipulated individuals). We tested differences in seed production for statistical significance using Kruskal–Wallis analysis. Results Eriosyce subgibbosa showed a distinctive pollinator assemblage among the sympatric species that we studied (similarity ranged from 0% to 8%); it was visited by small bees and was the only species that was visited by the giant hummingbird Patagona gigas. Pollinator assemblages were similar between E. chilensis (year 2016 = 4 species; 2017 = 8) and E. chilensis var. albidiflora (2016 = 7; 2017 = 4); however, those of E. curvispina var. mutabilis (2016 = 7; 2017 = 6) were less similar to those of the aforementioned species. E. curvispina var. mutabilis showed the highest interannual variation in its pollinator assemblage (18% similarity). Reproduction in E. subgibbosa largely depends on pollinators, although it showed some degree of autogamy. Autonomous pollination was unfeasible in E. chilensis, which depended on flower visitors for its reproductive success. Both E. chilensis var. albidiflora and E. curvispina var. mutabilis showed some degree of autogamy. Discussion We observed differences in pollinator assemblages between E. subgibbosa and the remaining Eriosyce taxa, which depend on hymenopterans for pollen transfer. Pollinator assemblages showed considerable interannual variation, especially those of E. subgibbosa (ornithophilous syndrome) and E. curvispina var. mutabilis (melitophilous syndrome). Autogamous reproduction in these taxa may act as a reproductive assurance mechanism when pollinator availability is unpredictable. Our study contributes to improving our understanding of the reproductive systems of ecological interactions between threatened species in a Chilean mediterranean-type ecosystem.

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Background. Sympatric plant species that share pollinators may have similar mating systems because their floral traits are subject to comparable canalization imposed by pollinators. However, if each sympatric species bears specialized floral morphology, each species may attract different pollinators. Our study aims to describe the pollinator diversity and pollination systems of four taxa of Eriosyce that co-occur in an endangered coastal Mediterranean ecosystem in Central Chile. We took two approaches in our study: we assessed the composition and similarity of flower visitors among taxa, and we characterized the breeding systems to determine dependence on pollinators and self-compatibility. Methods. We performed field observations to characterized pollinators during two consecutive years (2016-2017). Additionally, we performed pollination experiments to elucidate reproductive modes using three treatments: manual cross-pollination, automatic self-pollination, and control (unmanipulated individuals). Results. We observed one bird species (Giant hummingbird Patagona gigas only visiting E. subgibbosa) and 14 bee species (13 natives plus Apis mellifera) visiting cacti of the genus Eriosyce. We observed variation in the similarity of intra-specific pollinator composition between years and among Eriosyce species within the same year. Individuals of E. subgibbosa were visited by less number of species (2016 = 4; 2017 = 2), while E. chilensis (2016 = 4; 2017 = 8), E. chilensis var. albidiflora (2016 = 7; 2017 = 4) and E. curvispina var. mutabilis (2016 = 7; 2017 = 6) were visited by a richest guild of visitors (up to 10 bee species each).Autonomous pollination was unfeasible inE. chilensis, which depend on bees to achieve their reproductive success. Eriosyce subgibbosa, visited mainly by the Giant hummingbird, depends on pollinators to achieve reproductive success. Both E. chilensis var. albidiflora and E. curvispina var. mutabilis were visited by a diverse assemblage of non-social native bees, showing some degree of autonomous pollination and self-compatibility. Discussion. Pollinator diversity analyses showed considerable pollinator differences between the species with ornithophilous flowers (E. subgibbosa) and remain taxa which solely dependent on Apoidea species for pollen transfer. The high diversity of native bees among sympatric Eriosyce may be a caused by their microclimatic differences at spatial (differences among cacti microhabitats) and temporal levels (differences of climatic conditions between August to December when different Eriosyce species bloom). Our study contributes to unveiling the evolutionary mechanisms for pollinator partitioning of sympatric close-related plant species. Furthermore, it improves understanding of threatened species reproductive system and ecological interactions, especially to E. chilensis and E. chilensis var. albidiflora, whose studied populations are the only known for these taxa.

Background. Sympatric plant species that share pollinators may have similar mating systems because their floral traits are subject to comparable canalization imposed by pollinators. However, if each sympatric species bears specialized floral morphology, each species may attract different pollinators. Our study aims to describe the pollinator diversity and pollination systems of four taxa of Eriosyce that co-occur in an endangered coastal Mediterranean ecosystem in Central Chile. We took two approaches in our study: we assessed the composition and similarity of flower visitors among taxa, and we characterized the breeding systems to determine dependence on pollinators and self-compatibility. Methods. We performed field observations to characterized pollinators during two consecutive years (2016-2017). Additionally, we performed pollination experiments to elucidate reproductive modes using three treatments: manual cross-pollination, automatic self-pollination, and control (unmanipulated individuals). Results. We observed one bird species (Giant hummingbird Patagona gigas only visiting E. subgibbosa) and 14 bee species (13 natives plus Apis mellifera) visiting cacti of the genus Eriosyce. We observed variation in the similarity of intra-specific pollinator composition between years and among Eriosyce species within the same year. Individuals of E. subgibbosa were visited by less number of species (2016 = 4; 2017 = 2), while E. chilensis (2016 = 4; 2017 = 8), E. chilensis var. albidiflora (2016 = 7; 2017 = 4) and E. curvispina var. mutabilis (2016 = 7; 2017 = 6) were visited by a richest guild of visitors (up to 10 bee species each).Autonomous pollination was unfeasible inE. chilensis, which depend on bees to achieve their reproductive success. Eriosyce subgibbosa, visited mainly by the Giant hummingbird, depends on pollinators to achieve reproductive success. Both E. chilensis var. albidiflora and E. curvispina var. mutabilis were visited by a diverse assemblage of non-social native bees, showing some degree of autonomous pollination and self-compatibility. Discussion. Pollinator diversity analyses showed considerable pollinator differences between the species with ornithophilous flowers (E. subgibbosa) and remain taxa which solely dependent on Apoidea species for pollen transfer. The high diversity of native bees among sympatric Eriosyce may be a caused by their microclimatic differences at spatial (differences among cacti microhabitats) and temporal levels (differences of climatic conditions between August to December when different Eriosyce species bloom). Our study contributes to unveiling the evolutionary mechanisms for pollinator partitioning of sympatric close-related plant species. Furthermore, it improves understanding of threatened species reproductive system and ecological interactions, especially to E. chilensis and E. chilensis var. albidiflora, whose studied populations are the only known for these taxa.