The effect of invasive hybrid taxa on the ecological succession of coastal marshes

Authors: GALLEGO-TEVAR, BLANCA - University Of Sevilla; CURADO, GUILLERMO - University Of Sevilla; Grewell, Brenda; FIGUEROA, ENRIQUE - University Of Sevilla; CASTILLO, JESUS - University Of Sevilla

Submitted to: Biological Invasions
Publication Type: Abstract Only
Publication Acceptance Date: 3/14/2018
Publication Date: 9/7/2018
Citation: Gallego-Tevar, B., Curado, G., Grewell, B.J., Figueroa, E., Castillo, J.M. 2018. The effect of invasive hybrid taxa on the ecological succession of coastal marshes. Biological Invasions. [Abstract].

Interpretive Summary: Hybridization following colonization of invasive species in novel environments frequently results in offspring with improved biological and competitive functions referred to as heterosis or hybrid vigor. However, little is known about the effect of these invasive hybrids on the structuring and functioning of invaded ecosystems. Highly competitive, invasive hybrid taxa may play an important role in advanced stages of ecological succession in which competition becomes the dominant process determining the spatial distribution of plant taxa. In the marshes of the Gulf of Cadiz (SW Iberian Peninsula) the invasive cordgrass with South American origin Spartina densiflora (2n = 70) has hybridized with the native Spartina maritima (2n = 60) giving rise to two different hybrids Spartina maritima x densiflora (2n = ca. 95) and Spartina densiflora x martitima (2n = 65) with different ecological niches. To assess the role of these new genotypes in ecological succession, we recorded the size (diameter) of different tussocks of the Spartina hybrids and determined their annual lateral expansion growth rates in low and middle marshes in four invaded estuaries. The year of colonization was estimated for every tussock, and annual growth rates were compared to recorded meteororological with the aim to relate specific environmental conditions with colonization events of the invasive hybrids. Additionally, in a model invaded marsh in the Guadiana River Estuary, we recorded the cover of both Spartina hybrid taxa along the intertidal elevational gradient in January 2003 and 2016, and temporal changes in cover and distribution were analyzed. Results suggest that changes in meteorological conditions may increase hybridization risk and contribute to altering ecological succession within plant communities of coastal marsh ecosystems. In a scenario of climate change, results of this study are especially relevant to increase our knowledge about the effects of meteorological conditions on heterotic plant invasions.

Technical Abstract: Hybridization following colonization of invasive species in novel environments frequently results in offspring with improved biological and competitive functions referred to as heterosis or hybrid vigor. However, little is known about the effect of these invasive hybrids on the structuring and functioning of invaded ecosystems. Highly competitive, invasive hybrid taxa may play an important role in advanced stages of ecological succession in which competition becomes the dominant process determining the spatial distribution of plant taxa. In the marshes of the Gulf of Cadiz (SW Iberian Peninsula) the invasive cordgrass with South American origin Spartina densiflora (2n = 70) has hybridized with the native Spartina maritima (2n = 60) giving rise to two different hybrids Spartina maritima x densiflora (2n = ca. 95) and Spartina densiflora x martitima (2n = 65) with different ecological niches. To assess the role of these new genotypes in ecological succession, we recorded the size (diameter) of different tussocks of the Spartina hybrids and determined their annual lateral expansion growth rates in low and middle marshes in four invaded estuaries. The year of colonization was estimated for every tussock, and annual growth rates were compared to recorded meteororological with the aim to relate specific environmental conditions with colonization events of the invasive hybrids. Additionally, in a model invaded marsh in the Guadiana River Estuary, we recorded the cover of both Spartina hybrid taxa along the intertidal elevational gradient in January 2003 and 2016, and temporal changes in cover and distribution were analyzed. Results suggest that changes in meteorological conditions may increase hybridization risk and contribute to altering ecological succession within plant communities of coastal marsh ecosystems. In a scenario of climate change, results of this study are especially relevant to increase our knowledge about the effects of meteorological conditions on heterotic plant invasions.