Ecology of the orchid Goodyera repens in its southern distribution limits

Goodyera repens, a species of central and northern Europe, forms large populations in the Scotch pine forests in some areas of Mt Rhodopi (NE Greece), while it is completely absent in other areas with the same habitat type. The present study aims to investigate the ecological factors that constitute a barrier in the distribution of G. repens in its southernmost distribution limit. Data from 65 localities were sampled and chemical soil parameters were measured. Using the WorldClim database, the summer maximum temperatures and precipitation values were extracted. Binary logistic regression was used to determine the variables that best explain the distribution of G. repens. The data have been found to fit the model in a significant manner, and the independent variables significantly explaining the probability of G. repens being present were phosphorus, copper, and zinc. The results indicate that the distribution of G. repens is indirectly affected by soil variables through the establishment of mycorrhizal symbiosis. Furthermore, its distribution is found to be negatively correlated with the nutrient content of the soil. The high habitat specificity of the species and its sensitivity to soil nutrient status makes it a convenient indicator for monitoring the consequences of vegetation succession on forest biodiversity.