Citation:

jbi.12538

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Abstract:

Aim: Greater understanding of the processes underlying biological invasions is required to determine and predict invasion risk. Two subspecies of olive (Olea europaea subsp. europaea and Olea europaea subsp. cuspidata) have been introduced into Australia from the Mediterranean Basin and southern Africa during the 19th century. Our aim was to determine to what extent the native environmental niches of these two olive subspecies explain the current spatial segregation of the subspecies in their non-native range. We also assessed whether niche shifts had occurred in the non-native range, and examined whether invasion was associated with increased or decreased occupancy of niche space in the non-native range relative to the native range.

Location: South-eastern Australia, Mediterranean Basin and southern Africa.

Methods: Ecological niche models (ENMs) were used to quantify the similarity of native and non-native realized niches. Niche shifts were characterized by the relative contribution of niche expansion, stability and contraction based on the relative occupancy of environmental space by the native and non-native populations.

Results: Native ENMs indicated that the spatial segregation of the two subspecies in their non-native range was partly determined by differences in their native niches. However, we found that environmentally suitable niches were less occupied in the non-native range relative to the native range, indicating that niche shifts had occurred through a contraction of the native niches after invasion, for both subspecies.

Main conclusions: The mapping of environmental factors associated with niche expansion, stability or contraction allowed us to identify areas of greater invasion risk. This study provides an example of successful invasions that are associated with niche shifts, illustrating that introduced plant species are sometimes readily able to establish in novel environments. In these situations the assumption of niche stasis during invasion, which is implicitly assumed by ENMs, may be unreasonable.

Comment:

Contains raster maps (ESRI ASCII format) for 29 environmental variables in three geographical regions (Mediterranean Basin, southern Africa and south-eastern Australia) at a 30-sec resolution.

These maps were used for ecological niche modelling of native populations of Olea europaea subspecies europaea (Mediterranean Basin), native populations of Olea europaea subspecies cuspidata (southern Africa) along with the introduced populations of these two subspecies in south-western Australia.

The bioclimatic variables considered comprise the 19 WORLDCLIM temperature and rainfall variables (denoted bio1 to bio19), 9 soil properties variables (Rooting capacity, Soil bulk density, Soil field capacity, Soil thermal capacity, Soil total nitrogen density, Oxygen availability, Soil profile available water capacity, Soil wilting point and Soil carbon density) and the mean normalized vegetative index (NDVI), averaged for months January and July from 2001 to 2011. See the original paper for details.

Parameter(s):

#	Name	Short Name	Unit	Principal Investigator
1	File name	File name		Cornuault, Josselin
2	File size	File size	kByte	Cornuault, Josselin
3	Uniform resource locator/link to file	URL file		Cornuault, Josselin

License:

Creative Commons Attribution 3.0 Unported (CC-BY-3.0)

Size:

9 data points

Data

Download dataset as tab-delimited text — use the following character encoding:

1 File name	2 File size [kByte]	3 URL file
Africa_Raster	49616	hdl:10013/epic.45381.d001
Australia_Raster	66400	hdl:10013/epic.45381.d002
MediterraneanBasin_Raster	96320	hdl:10013/epic.45381.d003