Comparative effects of two species of floricolous <em>Metschnikowia</em> yeasts on nectar

Abstract

Canto, A., Herrera, C.M., García, I.M., García, M., Bazaga, P. 2015.Comparative effects of two species of floricolous Metschnikowia yeasts on nectar. Anales Jard. Bot. Madrid 72(1): e019Nectar yeast communities in southern Spain are dominated by two closely-related species, Metschnikowia reukaufii Pitt & M.W. Mill. and M. gruessii Gim.-Jurado (Ascomycota, Saccharomycetales), although they tend to be distributed differentially across different host plants. We explore here the possibility that the two yeasts play different functional roles in floral nectar by differing in their impact on sugar concentration and composition of nectar. Experiments were undertaken under controlled conditions using bumblebees caught foraging on the flowers of two different host plants each of which is known to harbor predominantly one of the two yeasts. Bumblebees were used as sources of inocula to obtain two groups of samples from the nectar of Helleborus foetidus L. (Ranunculaceae): nectar samples inoculated with M. gruessii and samples inoculated with M. reukaufii. Metschnikowia gruessii was poorly represented in nectar samples, while M. reukaufii was by far the most common and had the highest cell density. Although the two yeasts caused relatively similar changes in nectar sugar composition, which involved increasing fructose and decreasing sucrose proportions, they marginally differed in their quantitative impact on total nectar sugar concentration. Results suggest that differential yeast occurrence across host plants may lead to yeast specialization and modify the outcomes of the plant-pollinator interface. . Ambas levaduras son especies muy cercanas entre sí, pero se distribuyen diferencialmente entre las especies de plantas cuyo néctar las hospeda. En este trabajo se explora la posibilidad de que las levaduras tengan funciones distintas impactando diferencialmente la concentración y composición del néctar. Para esto se realizaron experimentos bajo condiciones controladas usando individuos de abejorros que fueron capturados cuando visitaban flores que albergan predominantemente una de las dos posibles levaduras mencionadas. Los abejorros fueron utilizados como agentes inoculantes naturales en el néctar de Helleborus foetidus L. para obtener dos grupos de muestras, unas con M. reukaufii y otras con M. gruessii. Los resultados mostraron que M. gruessii estuvo pobremente representada en las muestras; en contraste, M. reukaufii fue la más frecuente y de mayor densidad en el néctar. Aun cuando ambas levaduras tuvieron un efecto similar en la composición proporcional de los azúcares en el néctar, aumento de la fructosa y decremento de la sacarosa, las dos especies difieren marginalmente en su impacto en la concentración total de azúcares. Los resultados sugieren que la ocurrencia diferencial de las especies de levaduras entre sus plantas hospederas, puede conducir a una modificación en las interacciones entre las plantas y sus visitantes florales y también a una especialización de levaduras por hospedero.

Community‐wide consequences of sexual dimorphism: evidence from nectar microbes in dioecious plants

“…3). Compared to the typical variation in nectar microbial community structure among plant species (e.g., De Vega et al 2009, Herrera and Pozo 2010, Alvarez-P erez and Herrera 2013, Aleklett et al 2014, Herrera 2014, Canto et al 2015, Mittelbach et al 2015, the intraspecific variation we report here was surprisingly large, with more than a 2-and 10-fold difference between flower sexes in microbial prevalence ( Fig. 2a, b) and abundance ( Fig.…”

“…Many dioecious plants show sexual dimorphism in the chemical characteristics of floral nectar including the concentration and composition of sugars and other chemicals, which might reflect adaptive evolution towards increased pollination (Baker and Baker 1983, Delph and Lively 1992, Eckhart 1999, Bai et al 2011, Heil 2011, Nepi et al 2012. Although rarely considered in the context of sexual dimorphism (Golonka and Vilgalys 2013, Wei and Ashman 2018), the chemical properties of nectar could also affect its quality as a microbial habitat , Herrera and Pozo 2010, Pozo et al 2012, Alvarez-P erez and Herrera 2013, Aleklett et al 2014, Herrera 2014, Canto et al 2015, Mittelbach et al 2015. Nectar is often colonized by multiple species of fungi and bacteria via flower-visiting animals, resulting in microbial community assembly in each flower (Lachance et al 2001, Brysch-Herzberg 2004.…”

Nectar yeasts: a natural microcosm for ecology

“…Second, nectar yeast communities are simple enough to make it possible to study species interactions in detail. Nectar yeast communities are characterized by low species richness (but see Canto, Herrera, & Rodriguez, for preliminary evidence suggesting that nectar yeast diversity might be higher in the tropics than in temperate regions), dominated by a small number of species in the class Saccharomycetes, especially those in the genus Metschnikowia (Brysch‐Herzberg, ; Canto, Herrera, García, García, & Bazaga, ; Lachance, ; Pozo, Lachance, & Herrera, ), and potentially also by a few species in the basidiomycete class Tremellomycetes (Aleklett, Hart, & Shade, ; Brysch‐Herzberg, ; Peay et al, ; Pozo et al, ; Pozo, Herrera, & Bazaga, ). These species have presumably evolved a set of traits that facilitate survival and growth in the high osmotic pressure of floral nectar (Herrera et al, ; Peay et al, ).…”

“…Fourth, the ways in which nectar yeasts modify the environmental conditions of their habitats can be easily characterized, allowing detailed investigations into species interactions driven by niche preemption and modification. In addition to altering the sugar composition and concentration in floral nectar (Canto et al, ; Canto & Herrera, ; Herrera, García, & Pérez, ; Misra, Raghuwanshi, Gupta, Dutt, & Saxena, ; Pozo, de Vega, Canto, & Herrera, ; Schaeffer, Vannette, & Irwin, ), nectar yeasts can modify nectar secondary (specialized) metabolites (Vannette & Fukami, ), produce volatile organic compounds to attract pollinators (Golonka, Johnson, Freeman, & Hinson, ; Pozo et al, ; Raguso, ; Rering et al, ), draw down nitrogen in nectar (Dhami, Hartwig, & Fukami, ; Peay et al, ; Vannette & Fukami, ), and even increase nectar temperature (Herrera & Medrano, ; Herrera & Pozo, ). Researchers can use synthetic nectar to test how changing abiotic factors mediate biotic interactions between nectar microbes and other actors, such as pollinators.…”

Efficient production of isomelezitose by a glucosyltransferase activity in Metschnikowia reukaufii cell extracts

“…It is the predominant microorganism in nectaries of plants such as Helleborous foetidus (Pozo et al, 2011;Belisle et al, 2012;Herrera, 2014;Dhami et al, 2016). Although the ecological function of this yeast is relatively unknown, several studies relate it to the nectar sugar composition, the synthesis of volatile compounds or even with the nectaries temperature increases, all factors that may have incidence on the pollinators behaviour (Herrera and Pozo, 2010;Canto et al, 2015;Yang et al, 2019).…”