A seed infecting (Tilletia ehrhartae) could provide a partial biological control mechanism for invasive Veldt grass ( calycina). Briana Overman*, Fritz Light, and Francis Villablanca Biological Sciences, California Polytechnic State University, San Luis Obispo, CA 93407 Introduction Methods Results

Figure 7. Infected individuals showed Invasive species disrupt and alter ecosystem diversity, We collected Veldt grass samples from sand dune habitat at clustering of smutted stems, species composition, and ecological function. Management two locations, the Guadalupe-Nipomo Dunes National Wildlife and separate root masses of invasive species can lead to significant economic cost Refuge (N=24) and Los Osos (N=24), CA (Fig. 3). Quadrats leading to non-smutted stems. (Torchin and Mitchell 2004). Veldt grass, (Ehrharta were used to subsamples within each location. Quadrats (N= We interpreted this as an calycina), is causing a decline in plant diversity and a 6 / location) measuring 20m2 were placed so that they escape from systemic change in ecosystem processes in Coastal California. It is spanned variation in slope and aspect. The smutted infection. The average length ranked as “high concern” by the Calif. Invasive Plant individual (Fig. 4) closest to each for smutted stems and the Council because of it’s rate of spread and overall impacts. quadrat corner, with a diameter average length for non-smutted stems is shown in Figure 7. The paired t-test (at 10 cm above ground) <10 cm, (averages were compared within individuals and not across individuals, t-value = was collected. For each smutted The enemy release hypothesis (ERH) posits that plant 20.95, p-value << 0.0001) supports a decrease in vigor in smutted stems. species, on introduction to a novel region, experience a individual (4 per quadrat), the decrease in interactions with natural enemies that would nearest uninfected neighbor was normally regulate their distribution and abundance (Keane & also collected. We recorded the Crawley 2002). The fungus Tilletia ehrhartae (Fig. 1a) is a following data from 48 infected species-specific seed pathogen of Ehrharta calycina (Pasco and 48 uninfected individuals: et al. 2005). The fungal (Fig. 1b), is known from the plant diameter, height of each native range of Veldt grass () and stem, and total number of Figure 3. Map of study sites. Both If infection decreases vigor, then release from infection should correlate with an sites are within San Luis Obispo (ibid.). Infection by this smut is systemic (Castlebury et al. smutted and non-smutted stems. County, CA. Los Osos was sub increase in vigor. We tested for an increase in vigor associate with escape from 2005): the entire seed is replaced by fungal spores. Under In infected individuals, stem sampled at several State Parks and infection. An increase in vigor could be represented by “superior” growth (Fig. 5). open space preserves. The the ERH, the smut represents a potential biological control height of infected versus Guadalupe-Nipomo Dunes National An increase in vigor could also be represented by “socket” growth (uninfected) agent of Veldt grass. Studies have been conducted on uninfected stems was evaluated Wildlife Refuge GNDNWR was surrounding “ball” growth (infected) (Fig. 6). In both cases, no correlation was likewise subsampled at various 2 released from pathogens (Mitchell and Power 2003), to determine whether infection locations. discovered by X analysis (Table 1 abs 2). and it is known that pathogens can have a negative impact stimulated or inhibited growth. on host population densities and growth rates (Torchin and We also used growth at the site Mitchell 2004). But, it is also known that fungal infections of escape (in the root mass) to Conclusions can cause an increased in growth vigor (Wenndstrom 1999). evaluate inhibition/stimulation by An increase in vigor would make this plant more, not less, comparing infected and • Individuals exhibited escape from infection. invasive. uninfected parts of the root mass. Smutted • A significant difference in stem height between smutted (infected) and non- Specifically we determined if the Non-smutted smutted (uninfected) stems, suggesting a decrease in vigor with infection. • No correlation between infection and stimulated or inhibited vigor in growth. Herein we report escaped (uninfected) portions Figure 4. A comparison of smutted to the presence of were “superior” (Fig. 5), or if they non-smutted stems. • Because the plant is able to escape infection, the fungal infection becomes Tillatia erhartae in showed “ball and socket” (Fig. 6) less relevant over time. CoastalCalifornia, Coastal California growth forms. Either form would • Additional control methods including seed predators, herbicides, and removal we present indicate more vigorous growth in might aid in regulating this invasive species. evidence that the escaped (uninfected) portions of plants are able to escape fungal the root than in infected portions. infection, and we compared smutted References (infected) to escaped (uninfected) parts Castlebury, LA, Carris, LM, Vanky, K, 2005. Phylogenetic analysis of Tilletia and allied genera in order (Ustilaginomycetes; Exobasidiomycetidae) based on large subunit nuclear rDNA sequences. Mycologia 97: 888-900. of individual plants in order to estimate Superior Mitchell, CE, Power, AG, 2003. Release of Invasive Plants from Fungal and Viral Pathogens. Nature 421: 625‐627. Figure 5. Non-smutted stems as Pasco, IG, Priest, MJ, Shivas, RG, Cunnington, JH, 2005. Uslospores of Tillea ehrharta, a smut of Ehrharta calycina, are common contaminants the relative increase or decrease in Socket of Australian grain, and a potenal source of confusion with Tillea indica the cause of of wheat. Plant Pathology 54: Figure 1. Smut of Veldt superior to smutted stems 161‐168. vigor associated with the smut. grass, a. Teliospores of Ball Torchin, ME, Mitchell, CE, 2004. Parasites, Pathogens, and Invasions by Plants and Animals. Froners in Ecology and the Environment 2: Tilletia ehrhartae. b. Figure 6. Connection from smutted 183‐190. Smutted seed heads stems to non-smutted stems Wennstrom, A, 1999. The Effect of Systemic Rusts and Smuts on Clonal Plants in Natural Systems. Plant Ecology 144: 93-97. * [email protected], and [email protected]