title: Invasion of the tropical earthwormPontoscolex corethrurus(Rhinodrilidae, Oligochaeta) in temperate grasslands.
abstract: The tropical earthwormPontoscolex corethrurus(Rhinodrilidae, Oligochaeta) presents a broad distribution (e.g., 56 countries from four continents). It is generally assumed that temperature appears to limit the success of tropical exotic species in temperate climates. However, the distribution range of this species could advance towards higher elevations (with lower temperatures) where no tropical species currently occur. The aim of this study was to evaluate the soil and climatic variables that could be closely associated with the distribution ofP. corethrurusin four sites along an altitudinal gradient in central Veracruz, Mexico. We predicted that the distribution ofP. corethruruswould be more related to climate variables than edaphic parameters. Five sampling points (in the grassland) were established at each of four sites along an altitudinal gradient: Laguna Verde (LV), La Concepción (LC), Naolinco (NA) and Acatlán (AC) at 11-55, 992-1,025, 1,550-1,619 y 1,772-1,800 masl, respectively. The climate ranged from tropical to temperate along the altitudinal gradient. Ten earthworm species (5 Neotropical, 4 Palearctic and 1 Nearctic) were found along the gradient, belonging to three families (Rhinodrilidae, Megascolecide and Lumbricidae). Soil properties showed a significant association (positive for Ngrass, pH, permanent wilting point, organic matter and P; and negative for Total N, K and water-holding capacity) with the abundance of the earthworm community. Also there seems to be a relationship between climate and earthworm distribution along the altitudinal gradient.P. corethruruswas recorded at tropical (LV and LC) and temperate sites (NA) along the altitudinal gradient. Our results reveal that soil fertility determines the abundance of earthworms and site (climate) can act as a barrier to their migration. Further research is needed to determine the genetic structure and lineages ofP. corethrurusalong altitudinal gradients.
authors.affiliation: Instituto de Biotecnología y Ecología Aplicada (INBIOTECA), Universidad Veracruzana , Xalapa , Veracruz , México.
authors.forename: Diana
authors.initials: D
authors.lastname: Ortiz-Gamino
authors.affiliation: Programa de Estadística, Colegio de Postgraduados-Campus Montecillo , Texcoco , Estado de México , México.
authors.forename: Paulino
authors.initials: P
authors.lastname: Pérez-Rodríguez
authors.affiliation: Instituto de Biotecnología y Ecología Aplicada (INBIOTECA), Universidad Veracruzana , Xalapa , Veracruz , México.
authors.forename: Angel I
authors.initials: AI
authors.lastname: Ortiz-Ceballos
keywords: Agroecosystems; Biological invasions; Exotic species; Soil fauna