POLLINATION ECOLOGY OF POLYLEPIS TOMENTELLA (ROSACEAE), AN ANDEAN ANEMOPHILOUS TREE PRESENTING A POTENTIAL FLORAL FUNGAL INFECTION Alejandra I. Domic, 1, * Peter Bernhardt,† Retha Edens-Meier,‡ Gerardo R. Camilo,† and José M. Capriles§ *Centro de Estudios Avanzados en Zonas Áridas (CEAZA), La Serena, Chile; and Herbario Nacional de Bolivia, Universidad Mayor de San Andrés, La Paz, Bolivia; †Department of Biology, Saint Louis University, Saint Louis, Missouri 63130, USA; ‡School of Education, Saint Louis University, Saint Louis, Missouri 63130, USA; and §Department of Anthropology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA Editor: Michele R. Dudash Premise of research. Anemophily is considered to be a mechanism that evolved to promote pollination suc- cess. However, reproductive output can decrease if pollen loads are scarce due to low abundance of compatible mates or floral infections. Here we analyze the effects of breeding system, pollen limitation, and a potential floral fungal infection on the reproductive output of the Andean tree Polylepis tomentella (Rosaceae). Methodology. We performed pollen supplementation experiments in the field to assess the extent of the ef- fect of pollen limitation on fruit and seed set and to identify any pre- or postzygotic self-incompatibility re- sponses within receptive pistils. Supplementary scanning electron microscopy and epifluorescence microscopy were used to observe the possible effects of a potential floral fungal infection on sexual reproduction. Pivotal results. Pollen supplementation did not increase fruit and seed set, suggesting weak evidence of pol- len limitation. Most stigmas from self- and cross-pollinated flowers showed germinated pollen grains and pol- len tubes in the style, indicating that the species exhibits prezygotic self-compatibility. The presence of three As- comycota genera in stigmas and styles appears to have negatively affected the germination of pollen grains by inhibiting pollen tube growth, but we did not find evidence suggesting that hyphae are able to penetrate the ovary. Conclusions. This study showed that P. tomentella possesses a prezygotic self-compatible system and that fruit and seed set are not affected by pollen limitation. Therefore, reproductive assurance is achieved through pollen transfer between plants by wind and the role played by self-compatibility that allows selfing in the spe- cies. However, it is possible that the potential fungal infection could reduce the fecundity of its tree host, as hyphae are able to penetrate pollen grains. Keywords: pollen limitation, potential floral fungal infection, prezygotic self-incompatibility, treeline, wind pollination. Introduction The tree genus Polylepis (Rosaceae) inhabits the Andean tree- line and is widely but fragmentally distributed through South America. Thanks to key morphological and physiological adap- tations, such as small leaflets, multilayered bark, and high pho- tosynthetic capacity, these trees have successfully colonized ex- treme elevations (Macek et al. 2009; Rada et al. 2009; Toivonen et al. 2014). Nevertheless, presently 60% of the species are un- dergoing some form of population decline, mostly attributed to direct and indirect human agency (Capriles and Flores Bedregal 2002; Gareca et al. 2010; Cuyckens et al. 2016). Conservation efforts have been focused on reforestation; however, the success of these programs is variable due in part to low production of viable seeds. Causes of low viable seed yield have been broadly attributed to intrinsic factors, such as pollen limitation and par- thenorcarpy, as well as extrinsic factors, such as habitat degra- dation and resource limitation (Renison et al. 2005; Seltmann et al. 2008; Domic 2012). Furthermore, the breeding system of Polylepis has not been systematically investigated, and it could include a wide variation in breeding systems, from obligate out- crossing species to autonomously selfing species, as has been shown in the other genera of the Rosaceae family (Ashman 1999). Thus, we focus on understanding the reproductive sys- tem of Polylepis tomentella by testing the hypothesis of pollen limitation, evaluating whether there is self-incompatibility and assessing a potential floral fungal infection, which might con- stitute a likely new external factor causing low seed set. The im- plications of the results are significant for understanding the reproductive systems of other endangered anemophilous trees around the world. 1 Author for correspondence; current address: Department of An- thropology, The Pennsylvania State University, University Park, Penn- sylvania 16802, USA; e-mail: alejandradomic@gmail.com. Manuscript received July 2016; revised manuscript received April 2017; electronically published May 10, 2017. Int. J. Plant Sci. 178(7):000–000. 2017. q 2017 by The University of Chicago. All rights reserved. 1058-5893/2017/17807-00XX$15.00 DOI: 10.1086/692504 000 This content downloaded from 128.032.010.164 on May 16, 2017 05:47:08 AM All use subject to University of Chicago Press Terms and Conditions (http://www.journals.uchicago.edu/t-and-c).