Variation characteristics of an invasive Alternanthera philoxeroides community along latitudinal gradients in spring

Abstract

Latitude and season are the crucial environmental factors that affect biological invasions, such as Alternanthera philoxeroides, a malignant invasive weed native to South America and now widely found in several provinces of China. To explore variation characteristics of an A. philoxeroides community along latitudinal gradients and also to test its invasive effect on native plant diversity (α diversity indices) and community stability (Godron coordinate values) in spring, a latitudinal field survey was conducted in April with 15 invasive and 15 control plots selected in the 22°-30° N (spanning Guangdong, Guangxi, Hunan, and Hubei Provinces) terrestrial habitats of South China. Analysis included the ordination method of canonical correspondence analysis (CCA) based on species and environmental matrixes, as well as the curve regression between A. philoxeroides cover and α diversity indices (the Simpson, Shannon, Pielou, and Patrick indices). Results showed that: 1)species cover of Alternanthera philoxeroides increased with increasing latitude from 22°-30° N of China with the Simpson, Shannon, and Pielou indices all significantly and negatively correlated (P=0.012, r=-0.629; P=0.020, r=-0.591; P=0.024, r=-0.579, respectively) to latitude in the invasive community but significantly and positively correlated (P=0.041, r=0.533; P=0.020, r=0.591; P=0.010, r=0.641, respectively) in the control community. The Patrick index had no significant correlation with latitude. 2) Invasion decreased species diversity at the whole community level (t=7.811, PA. philoxeroides coverA. philoxeroides was near to the central position indicating it had a wider latitudinal adaptability. These findings would be helpful for predicting dynamics of an invasive plant community and also very important for biological invasion control and native biodiversity protection.