Understanding diversity patterns along environmental gradients and their underlying mechanisms is a major topic in current biodiversity research. In this study, we investigate for the first time elevational patterns of vascular plant species richness and endemism on a long-isolated continental island (Crete) that has experienced extensive post-isolation mountain uplift. We used all available data on distribution and elevational ranges of the Cretan plants to interpolate their presence between minimum and maximum elevations in 100-m elevational intervals, along the entire elevational gradient of Crete (0–2400 m). We evaluate the influence of elevation, area, mid-domain effect, elevational Rapoport effect and the post-isolation mountain uplift on plant species richness and endemism elevational patterns. Furthermore, we test the influence of the island condition and the post-isolation mountain uplift to the elevational range sizes of the Cretan plants, using the Peloponnese as a continental control area. Total species richness monotonically decreases with increasing elevation, while endemic species richness has a unimodal response to elevation showing a peak at mid-elevation intervals. Area alone explains a significant amount of variation in species richness along the elevational gradient. Mid-domain effect is not the underlying mechanism of the elevational gradient of plant species richness in Crete, and Rapoport's rule only partly explains the observed patterns. Our results are largely congruent with the post-isolation uplift of the Cretan mountains and their colonization mainly by the available lowland vascular plant species, as high-elevation specialists are almost lacking from the Cretan flora. The increase in the proportion of Cretan endemics with increasing elevation can only be regarded as a result of diversification processes towards Cretan mountains (especially mid-elevation areas), supported by elevation-driven ecological isolation. Cretan plants have experienced elevational range expansion compared to the continental control area, as a result of ecological release triggered by increased species impoverishment with increasing elevation.

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TaxonAltitude (m) (Mean ± SD) Arrhenath ( 129) Brachyp ( 180) Calamagro ( 3) Calthion ( 18) Chrysopog ( 134) Cynosurion ( 274) Deschamp ( 31) Festucetalia (137)

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Crete is especially rich in orchids and their distribution is well known and documented by many floristic accounts. This information, however, is yet to be used to set conservation plans and priorities. We used MaxEnt incorporating both published and unpublished distribution data together with environmental variables to predict the potential distribution of orchids on Crete. The resulting probabilistic maps of species occurrence were used to identify the important areas for orchid conservation on the island. Sites prioritization was performed by applying a species weighting scheme, which was based on species niche breadth. The existence of ecological patterns determining site prioritization was determined using a regression tree analysis based on environmental variables and scores derived from Zonation analysis. The high importance sites were found on Mts Thripti, Ida and Lefka Ori, as well as at low altitude areas east of Heraklion and at the easternmost part of the island. Most of the variation in the site scores was explained by geological substrate, latitude and altitude. Based on the regression tree analysis, sites with the highest scores were at medium and high altitude areas, which are located at the interior of the island. These areas have soils mainly derived from limestones, ophiolites and deposits of calcareous rocks. The lack of a significant effect of vegetation type in explaining the distribution of high importance areas highlights the need for the establishment of micro-reserves for the conservation of orchids in Crete. Finally, endangered orchid species in need of specific conservation actions are indicated.