Neotyphodium endophyte infection frequency in annual grass populations: relative importance of mutualism and transmission efficiency

GUNDEL, PE; BATISTA, WH; TEXEIRA,M; MARTINEZ-GHERSA,MA; OMACINI,M; GHERSA,CM

PROCEEDINGS OF THE ROYAL SOCIETY OF LONDON. SERIES B: BIOLOGICAL SCIENCES.

Año: 2008 vol. 275 p. 897 - 905

0962-8452

Persistence and ubiquity of the vertically transmitted Neotyphodium endophytes in grass populations is puzzling because infected plants do not consistently exhibit increased fitness. Using a closed-population mathematical model, we show that the problems for matching endophyte infection with increased host fitness are likely to arise from tiny-effect-detection difficulties. Although the endophyte would persist in the long term only if the infection confers some fitness-increase to the host plants, such increase can be very small, as long as the transmission efficiency is larger than the ratio between the multiplication rates of non-infected and infected plants. Our model illustrates how imperfect transmission limits effectively the equilibrium infection level even if infected individuals have a large reproductive advantage. Sensitivities of the equilibrium infection frequency to changes in transmission efficiency and host reproductive enhancement suggest that environmental variation in these two drivers is likely to keep grass populations away from equilibrium infection levels.