Floristic composition and potential invasiveness of alien herbaceous plant in Western Mexico

Abstract

Introduction: Numbers of alien plant species are rising around the globe, but not all of them become invasive. Whereas introductions have been documented for several decades in some regions of the world, knowledge on alien species in Western Mexico is limited. Here, we study roadside vegetation along an elevational gradient, which includes a protected area. Objective: We analysed the floristic composition of herbaceous alien species, their distribution patterns, and their relationship with various environmental factors. A relative importance value index (IVI) identified the most important and, therefore, probably invasive taxa. Methods: During 2017 and 2018, roadside vegetation was documented with 4-6 transects every 300 altitudinal meters, from 0 to 2 100 m, for a total of 37 transects. Each transect consisted of five 1 m² plots. All herbaceous species were registered and alien taxa identified. A cluster analysis distinguished grouping of species based on elevation. The potentially invasive species were identified by their IVI, based on the sum of relative frequency and density values. The influence of environmental variables was analysed with a canonical correspondence analysis. Results: Most alien species were grasses; other families were represented by one or two species. The species were grouped into three main clusters. The first group included rare species, the second consisted of species restricted to higher altitudes, and the third group were tropical taxa with a distribution from sea level to medium altitudes. The most important potentially invasive species were: Urochloa maxima, Melinis repens, Eragrostis ciliaris and Cynodon dactylon, all African grasses introduced for grazing. The IVI of the species was related to tree cover, leaf litter depth and surface stone cover for some species and, for others, to soil compaction, distance to major roads and elevation. Conclusions: The alien ruderal species clustered according to the general climate (temperate vs. tropical). Grasses of African origin are of highest concern as invasive species. Although most introductions are related to human disturbance, each species becomes dominant under certain environmental conditions. Thus, management programs must be specifically adjusted to each individual invasive alien.

Alien and Potentially Invasive Plants in Four Lagoons on the Island of Cozumel, Mexico

“…A relatively large number of the species found in the 4 lagoons (13.9%) were alien, and considered potentially invasive, since they have been reported as invasives elsewhere in Mexico and in different types of ecosystems and environments. For example, Cynodon dactylon was considered potentially invasive in the mountain ranges along the Mexican Pacific coast [24] and in northwestern Mexico (Baja California) [25] after its introduction for grazing.…”

“…Invasion drivers-Different environmental conditions are relevant for species invasion. Nutrient contents, floristic structure, vegetation density, climate, and hydrology oftentimes play a decisive role in the colonization, establishment, and invasion of alien species [24,25]. Because the lagoons we studied are on an island, the most likely drivers of colonization are human activities (cattle ranching) and decisions (ornamental plants).…”

Vegetación viaria en el municipio de Malinalco, Estado de México, México

“…Recientemente, las especies ruderales y, en especial, las viarias, han despertado interés como posibles hábitats y conectores paisajísticos para polinizadores y otros animales. La vegetación viaria también se conoce como ruta de expansión para plantas invasoras (Cerazo & Conticello 2007, Pérez-Postigo et al 2021.…”

“…La vegetación de las orillas de carretera tampoco ha sido centro de atención para los botánicos, ya que se conoce poco sobre su composición y ecología (Flores-Huitzil et al 2020, Pérez-Postigo et al 2021. Entre las contribuciones al respecto se encuentran Barradas Medina (1992), quien exploró aspectos ecológicos y florísticos de las especies en el tramo de carretera Xalapa-Veracruz.…”

“…En este estudio se reportó una mayor proporción de especies herbáceas, dispersión de diásporas principalmente a través del viento y por gravedad, las cápsulas y los aquenios como tipos de fruto dominantes y reproducción sexual, en la mayoría de las especies. Posteriormente, Pérez-Postigo et al (2021) encontraron que, en el borde de una carretera de la Sierra de Manantlán y regiones aledañas en el suroeste de Jalisco, la mayoría de las especies introducidas eran gramíneas, destacando como las especies potencialmente invasoras más importantes a Megathyrsus maximus, Melinis repens, Eragrostis ciliaris y Cynodon dactylon.…”