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

BACKGROUND AND AIMS: Ant-plant associations are widely diverse and distributed throughout the world, leading to antagonistic and/or mutualistic interactions. Ant pollination is a rare mutualistic association and reports of ants as effective pollinators are limited to a few studies. Conospermum (Proteaceae) is an insect-pollinated genus well represented in the south-western Australia biodiversity hotspot, and here we aimed to evaluate the role of ants as pollinators of C. undulatum. METHODS: Pollen germination after contact with several species of ants and bees was tested for C. undulatum and five co-flowering species for comparison. We then sampled the pollen load of floral visitors of C. undulatum to assess whether ants carried a pollen load sufficient to enable pollination. Lastly, we performed exclusion treatments to assess the relative effect of flying- and non-flying-invertebrate floral visitors on the reproduction of C. undulatum. For this, we measured the seed set under different conditions: ants exclusion, flying-insects exclusion and control. KEY RESULTS: Pollen of C. undulatum, along with the other Conospermum species, had a germination rate after contact with ants of ~80 % which did not differ from the effect of bees; in contrast, the other plant species tested showed a drop in the germination rate to ~10 % following ant treatments. Although ants were generalist visitors, they carried a pollen load with 68-86 % of suitable grains. Moreover, ants significantly contributed to the seed set of C. undulatum. CONCLUSIONS: Our study highlights the complexity of ant-flower interactions and suggests that generalizations neglecting the importance of ants as pollinators cannot be made. Conospermum undulatum has evolved pollen with resistance to the negative effect of ant secretions on pollen grains, with ants providing effective pollination services to this threatened species.

Pre-zygotic reproductive isolation between two synchronopatric Opuntia (Cactaceae) species in the Brazilian Chaco.

Opuntia (Cactaceae) is known for high rates of hybridization and ploidisation, resulting in the formation of new species. The occurrence of two sympatric and closely related species of Opuntia, O. elata and O. retrorsa, in Brazilian Chaco enabled us to test the hypothesis that pre-zygotic reproductive isolation mechanisms operate in both species. We monitored the flowering period, as well as floral biology, and compared the morphological variation of floral structures through measurements, performed intra- and interspecific cross-pollination tests, and recorded the guild of floral visitors and pollinators. Flowering was seasonal and highly synchronous. Floral biology exhibits similar strategies, and although floral morphology differs significantly in many of the compared structures, such morphological variation does not result in the selection of exclusive pollinators. Floral visitors and pollinators are oligolectic bees shared by both species. Opuntia elata and O. retrorsa are self-compatible. While interspecific cross-pollination (bidirectional) resulted in germination, the pollen tube did not penetrate the stigma. Opuntia elata and O. retrorsa are closely related; however, they are isolated and do not hybridise in Brazilian Chaco. We found that both have weak pre-pollination barriers, but that they are strongly isolated by pollen-pistil incompatibility, i.e. post-pollination barrier.

Apis mellifera pollen loads to understand the pollen foraging pattern used for apicultural practice in a potentially agricultural belt in Bengal, India / Cargas polínicas de Apis mellifera para entender los patrones de forrajeo de polen usados en apicultura en una franja potencialmente agrícola en Bengala, India

Abstract For accurate determination of polleniferous taxa vis-a-vis floral fidelity of Apis mellifera L. in North 24 Pargana, West Bengal, we carried out pollen analyses of individual corbicular pollen loads collected from four apiaries during 2015-2016. Among the 2 434 analyzed loads, 72.97 % were unifloral type, 19.0 % bifloral and 8.10 % were multifloral in pollen composition. We identified 43 different types of palynomorphs belonged to 28 botanical families. Major polleniferous plant species include: Alangium salviifolium, Borassus flabellifer, Brassica nigra, Coriandrum sativum, Croton bonplandianum, Cyanotis axillaris, Luffa cylindrica, Neolamarckia cadamba, Phoenix sylvestris, Poa gangetica, Sesamum indicum and Trema orientalis. Among them, T. orientalis is newly reported from West Bengal especially during June to August (monsoon season). The plant family provided maximum number of loads was Arecaceae (20.91 %), followed by Brassicaceae (16.2 %), Poaceae (6.70 %), Pedaliaceae (6.38 %), Apiaceae (6.16 %) and Fabaceae (5.38 %). Month wise highest number of pollen diversity were obtained during March (13 pollen types) and a minimum of 6 types in November. The present investigation will help the beekeepers to maintain their hives in the region for sustainable apicultural practices.(AU)

Resumen Para una determinación precisa de taxa polinífero y fidelidad floral de Apis mellifera en Pargana Norte 24, Bengala Occidental, realizamos análisis de cargas individuales de polen corbicular, recolectados en cuatro apiarios durante 2015-2016. De las 2 434 cargas analizadas, 72.97 % fueron de tipo unifloral, 19.0 % bifloral y 8.10 % multifloral, en la composición del polen. Identificamos 43 tipos diferentes de palinomorfos pertenecientes a 28 familias botánicas. Las especies principales de plantas poliníferas incluyen: Alangium salviifolium, Borassus flabellifer, Brassica nigra, Coriandrum sativum, Croton bonplandianum, Cyanotis axillaris, Luffa cylindrica, Neolamarckia cadamba, Phoenix sylvestris, Poa gangetica, Sesamum indicum y Trema orientalis. Entre estas, T. orientalis ha sido reportada recientemente en Bengala Occidental, especialmente de junio a agosto (temporada de monsones). La familia de plantas que presentó máxima cantidad de cargas fue: Arecaceae (20.91 %), seguida por Brassicaceae (16.2 %), Poaceae (6.70 %), Pedaliaceae (6.38 %), Apiaceae (6.16 %) y Fabaceae (5.38 %). De acuerdo al mes, el número mayor de diversidad de polen se obtuvo durante marzo (13 tipos de polen) y un mínimo de seis tipos en noviembre. La presente investigación ayudará a los apicultores a mantener sus colmenas en la región para prácticas apícolas sostenibles.(AU)