DOI: 10.5061/dryad.nf515
title: Data from: Fungal symbionts maintain a rare plant population but demographic advantage drives the dominance of a common host

description: 1. A potential driver of species abundance that remains understudied is
 the interaction between host species and their microbial symbionts.
 Beneficial symbionts could promote the dominance of common host species by
 increasing their population growth rates more than they do for rare
 species, and symbiont benefits could be important for maintaining rare
 species in communities. Alternatively, intrinsic differences in
 demography, independent of interactions with symbionts, could be the main
 driver of species’ relative abundances. 2. Here, we used demographic
 modelling with 5 years of data from experimental host populations to
 compare how symbiotic fungal endophytes, which are vertically transmitted
 from parent plant to offspring, influenced the population dynamics of one
 pair of co-occurring, congeneric rare versus common host grasses (genus
 Poa). 3. The common plant species achieved higher population growth than
 the rare species. Endophyte symbiosis increased the geometric population
 growth rate (λ) of rare and common species by 18% and 32%, respectively,
 but only the rare species was predicted to decline (λ &lt; 1) in the
 absence of the endophyte, demonstrating that symbiosis was essential to
 maintain this species in the community. 4. Endophyte symbiosis
 differentially affected the demographic transitions of the two hosts,
 increasing survival and growth for the common host, Poa sylvestris, and
 increasing survival but decreasing the probability of flowering for the
 rare host, Poa alsodes. The total contribution of the endophyte effects on
 host demographic rates to the overall difference in population growth
 between host species was small compared to the plants’ intrinsic
 differences in demography. However, low rates of vertical transmission in
 P. sylvestris lessened its advantage in intrinsic demography over P.
 alsodes and thus decreased the projected difference in population growth
 between host plants. 5. Synthesis. Our results highlight the importance of
 plant–symbiont interactions in the persistence of a rare plant population,
 as well as the utility of demographic models in teasing apart the relative
 importance of plant demographic rates versus host–symbiont interactions on
 the regional abundance of rare and common host plant species.
description: Poa alsodes demographic
 transitionsSurvival, growth, and
 reproduction of Poa alsodes individuals in experimental plots 2008-2011.
 Populations established at the Indiana University Research and Teaching
 Preserve at Lilly Dickey Woods, Nashville, Indiana, USA
 (39°14'54''N, –86°13'05''W). Column heading
 descriptions as follows: "TAG": individual identifier,
 "PLOT": the plot to which that individual belongs,
 "Endo": whether plant was endophyte-symbiotic (1) or
 endophyte-free (0), "Year1": the beginning year of the
 transition period, "Age1": age of individual at year 1,
 "Size1": size of individual at year 1 (number of tillers),
 "Seeds1": projected amount of seed production at year1,
 "Survto2": whether that individual survives to the next year,
 "Size2": if it survives, the size of the individual at the next
 year.POAL_transitions_R.csvPoa sylvestris demographic transitionsSurvival, growth, and reproduction of Poa sylvestris individuals in experimental plots 2008-2011. Populations established at the Indiana University Research and Teaching Preserve at Lilly Dickey Woods, Nashville, Indiana, USA (39°14'54''N, –86°13'05''W). Column heading descriptions as follows: "TAG": individual identifier, "PLOT": the plot to which that individual belongs, "Endo": whether plant was endophyte-symbiotic (1) or endophyte-free (0), "Year1": the beginning year of the transition period, "Age1": age of individual at year 1, "Size1": size of individual at year 1 (number of tillers), "Seeds1": projected amount of seed production at year1, "Survto2": whether that individual survives to the next year, "Size2": if it survives, the size of the individual at the next year.POSY_transitions_R.csvPoa alsodes seedling establishmentSeedling establishment rates of Poa alsodes at the plot level 2008-2011. Column headings as follows: "Plot": plot identifier, "Endo": whether plants in that plot were endophyte-symbiotic (1) or endophyte-free (0), "Year1": beginning year of transition, "Seeds1": total number of seeds produced by plants in that plot , "Recruits2": total number of new recruits to that plot the next year, "P.est": rate of seedling establishment (=Recruits2/Seeds1).POAL_p.est_R.csvPoa sylvestris seedling establishmentSeedling establishment rates of Poa sylvestris at the plot level 2008-2011. Column headings as follows: "Plot": plot identifier, "Endo": whether plants in that plot were endophyte-symbiotic (1) or endophyte-free (0), "Year1": beginning year of transition, "Seeds1": total number of seeds produced by plants in that plot , "Recruits2": total number of new recruits to that plot the next year, "P.est": rate of seedling establishment (=Recruits2/Seeds1).POSY_p.est_R.csvGrowth and survival of Poa alsodes new recruitsGrowth and survival of Poa alsodes new recruits in their first year. Column headings are as follows: "TAG": seedling identifier, "PLOT": plot into which seedling recruited, "Endo": the endophyte status of that plot, "Year1": the year seedling first recorded, "Size1": size (number of tillers) of seedling, "Seeds1": reproduction of seedling at first year, "Survto2": seedling survival into the next year, "Size2": if it survived, seedling size in the next year.POAL_seedlings_R.csvGrowth and survival of Poa sylvestris new recruitsGrowth and survival of Poa sylvestris new recruits in their first year. Column headings are as follows: "TAG": seedling identifier, "PLOT": plot into which seedling recruited, "Endo": the endophyte status of that plot, "Year1": the year seedling first recorded, "Size1": size (number of tillers) of seedling, "Seeds1": reproduction of seedling at first year, "Survto2": seedling survival into the next year, "Size2": if it survived, seedling size in the next year.POSY_seedlings_R.csvIPM and LTRE codeR code to parameterize integral projection models for each species with transitions between endophyte statuses based on transmission rates. Between-species LTRE modeled to compare the contributions of intrinsic demographic rates and effects of endophyte symbiosis towards the observed difference in population growth.