4.1. Range shift of Z. spina-christi and Z. nummularia
The present geographical range ofZ. spina-christi is primarily concentrated in the southern regions of Fars, parts of Bushehr, the southern and western portions of Khuzestan, as well as areas to the south of Kohgiluyeh-Boyar Ahmad and Kerman provinces. Climatically suitable habitats are limited in the country’s southeastern part, specifically in Hormozgan and Sistan-Baluchistan. The Khalijo-Omanian zone, a subregion of the Saharo-Sindian region in Iran, encompasses this area. This phytogeographical region can be further divided into two distinct territories: Khalijio-Omani. These territories exhibit ecological differences, with varying climates and higher temperatures along the Omani coasts. The average temperature in this zone tends to increase from west to east (Sagheb Talebi et al., 2014).
Within the Khaliji territory, Z. spina-christi plays a pivotal role. In the Omani territory, the prevailing plant community consists mainly of Acacia genus, which are paramount in the region’s woody flora (Sagheb Talebi et al., 2014). The decrease in habitat suitability for Z. spina-christi in southeastern Iran reflects the shifting plant communities. Our study has illuminated significant distinctions between these two ecological zones. In an optimistic scenario (i.e., SSP-126), during two periods (2041-2071 and 2071-2100), the spatial distribution of Z. spina-christi is expected to expand slightly into the central parts of Fars and the western regions of Khuzestan. However, under the SSP-585 scenario for the 2041-2070 period, suitable habitats are projected to fragment and diminish in southern Kerman and Khuzestan. Conversely, habitat expansion and extension are anticipated in Fars towards higher latitudes.
In light of the temperature increase projected in scenario SSP-585, the period from 2071 to 2100 may witness the contraction and reduction of local habitats in southern Kerman while new suitable habitats emerge in the northwest of Kerman. Fars province is expected to experience a shift in suitable habitats towards higher latitudes, and suitable habitat is anticipated to develop in South Khorasan province, where the presence ofZ. spina-christi presence has not been previously documented. In summary, the overall trend for the distribution ofZ. spina-christi is expected to increase. Several global studies have reported similar patterns of species range changes, including Ksiksi et al. (2019), Liu et al. (2021), Singh et al. (2022), and Koldasbayeva et al. (2022).
As for Z. nummularia , its current range is primarily located in the southwestern and western regions of the country, covering an area of approximately 23,000 square kilometers. Typically, this species is observed and recorded as a companion species within Z. spina-christi vegetation communities, but they do not form distinct plant communities. The habitat suitability ofZ. nummularia in the future, under the optimistic SSP-126 scenario for the periods of 2041-2070 and 2071-2100, may result in the elimination and possible local extinction of suitable habitats for this species in Fars, Bushehr, and Kohgiluyeh-Boyar Ahmad, with a reduction in existing habitats in Khuzestan. Conversely, in the pessimistic SSP-585 scenario and the 2041-2070 periods, there is an anticipation of a slight expansion of this species’ spatial distribution in Khuzestan province, extending to higher latitudes.
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However, under the climatic scenario SSP-585 from 2071 to 2100, this species’ habitat is projected to experience widespread contraction and extinction. This will destroy all suitable habitats for Z.nummularia in Fars, Bushehr, Kohgiluyeh-Boyar Ahmad, and southern Khuzestan, while new habitats will emerge at higher latitudes in Ilam province. Ultimately, the overall trend for the distribution of Z. nummularia is expected to decrease. Various studies support the observed pattern of changes in Z. nummularia distribution, including those conducted by Tarnian et al. (2021) and Khanal et al. (2022).Top of Form