Realized niche and spatial pattern of native and exotic halophyte hybrids

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: Oecologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/24/2018
Publication Date: 8/25/2018
Citation: Gallego-Tevar, B., Curado, G., Grewell, B.J., Figueroa, E., Castillo, J.M. 2018. Realized niche and spatial pattern of native and exotic halophyte hybrids. Oecologia. 188(3):849-862. https://doi.org/10.1007/s00442-018-4251-y.
DOI: https://doi.org/10.1007/s00442-018-4251-y

Interpretive Summary: Interspecific hybridization is an important and common evolutionary mechanism, but there are a lack of field studies analyzing changes in realized niches and zonation patterns of native and exotic hybrids in relation to their parental species. We examined the main sedimentary characteristics of the realized niches of native Sarcocornia hybrids, invasive Spartina hybrids and their parental species in 14 marshes of four estuaries in Southwest Iberian Peninsula, and the level of interaction between plant taxa and the zonation pattern along the intertidal gradient. The native Sarcocornia hybrids and the exotic Spartina hybrids showed different habitat amplitudes, zonation patterns and ecological behaviors than their parental species. While the native and fertile hybrids of Sarcocornia showed similar realized niche amplitude as their parental species and shared the marsh with other species, the exotic and sterile hybrids of Spartina exhibited realized niche amplitudes lower than their parental species (probably related to dispersion limitations). The exotic invasive hybrids did not share their occupied space with other halophytes. Thus, while the native hybrids play a structuring role, the exotic Spartina hybrids appear to be playing a disruptive role in the native zonation pattern, which could get aggravated if these sterile hybrids would become fertile. In view of our results, steps must be taken as soon as possible to eradicate both Spartina hybrids in the Gulf of Cadiz. Our study shows that the niche concept may be an important tool to analyze species roles in the ecosystems, incorporating many ideas from the individual to the ecosystem levels. Thus, our approach to the niche provides a framework to explore the function of plant hybrid taxa in plant communities in relation to their parental species, examining the ways hybrids respond to their environment (i.e. their requirements) and how reciprocally they impact the environment (i.e. through biotic interactions such as interspecific competition). This framework for invasive species impact assessment can be applied to estuaries elsewhere in Europe, and in California where hybrids of exotic and native Spartina species are spreading. Our results point to fertile and sterile, and native and exotic, hybrids carrying out contrasted responses to the abiotic environment and developing different roles in how plant communities assemble, which may be relevant to the biological evolution of hybrids.

Technical Abstract: Interspecific hybridization is an important and common evolutionary mechanism, but there are a lack of field studies analyzing changes in realized niches and zonation patterns of native and exotic hybrids in relation to their parental species. We examined the main sedimentary characteristics of the realized niches of native Sarcocornia hybrids, invasive Spartina hybrids and their parental species in 14 marshes of four estuaries in Southwest Iberian Peninsula, and the level of interaction between plant taxa and the zonation pattern along the intertidal gradient. The native Sarcocornia hybrids and the exotic Spartina hybrids showed different habitat amplitudes, zonation patterns and ecological behaviors than their parental species. While the native and fertile hybrids of Sarcocornia showed similar realized niche amplitude as their parental species and shared the marsh with other species, the exotic and sterile hybrids of Spartina exhibited realized niche amplitudes lower than their parental species (probably related to dispersion limitations). The exotic invasive hybrids did not share their occupied space with other halophytes. Thus, while the native hybrids play a structuring role, the exotic Spartina hybrids appear to be playing a disruptive role in the native zonation pattern, which could get aggravated if these sterile hybrids would become fertile. In view of our results, steps must be taken as soon as possible to eradicate both Spartina hybrids in the Gulf of Cadiz.