Panayiotis Trigas

Elevational gradient of vascular plant species richness and endemism in Crete--the effect of post-isolation mountain uplift on a continental island system.

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 Rapoports 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.

Species diversity, endemism and conservation of the family Caryophyllaceae in Greece

The family Caryophyllaceae includes world-wide 86 genera and approximately 2100 species. Greece is one of its most important centres of diversity and endemism. A total of 428 Caryophyllaceae taxa are distributed in Greece, 161 of them being endemic to the Greek political territory. The endemic element represents approximately 5% of the global diversity of the family at the species level. The aim of this paper is to discuss the distribution patterns of the Greek endemic Caryophyllaceae, as well as those with a limited distribution range to the neighbouring areas of the Balkans and Anatolia, on the basis of the phytogeographical regions of Greece in order to identify the important regions for their conservation. The majority of the Greek endemic Caryophyllaceae (64.6%) are distributed in only one single phytogeographical region, or even a smaller area indicating the extremely restricted distribution ranges of the endemic plants in Greece. Actually 83 Greek endemic Caryophyllaceae can be grouped on cytotaxonomic criteria. Most of them belong to the category of schizoendemics (91.6%), indicating that the endemism of Caryophyllaceae in Greece has mainly originated in an active way. Cluster analysis has been used to classify the phytogeographical regions according to their floristic similarities. Two iterative complementarity methods were used to evaluate the importance of each phytogeographical region in the conservation of the endemic Caryophyllaceae in Greece. Peloponnisos, Kriti-Karpathos and Sterea Ellas are the most important phytogeographical regions in this respect, followed by North Central and North East. When adding the Balkan-Aegean-Anatolian endemics to the analysis, Peloponnisos, North Central, Kriti-Karpathos, North East and Eastern Aegean result as the most important areas. In every case, an elevated number of sites are required for the conservation of Caryophyllaceae in Greece, reflecting the great dissimilarities in the floristic composition of the various phytogeographical regions. The results provided by the different methods are compared. A catalogue of the Greek endemic Caryophyllaceae is appended.

Distribution Patterns and Conservation Perspectives of the Endemic Flora of Peloponnese (Greece)

An inventory of the endemic vascular plants of the Peloponnese (395 species and subspecies) has been created based on literature, herbarium and field data. Endemics’ distribution patterns, altitudinal distribution and habitat specificity were investigated. A rarity score for each endemic has been calculated based on its population size, geographic range and habitat specificity. The main mountainous areas of the Peloponnese are largely congruent to the hotspots of endemism. Altitudinal range and niche breadth of the endemics were positively correlated to their range size. The elevational gradient of the endemic species richness showed a hump-shaped pattern, in contrast to the monotonically decreasing pattern of total species richness. Endemic species were found to support boundary theory, while total species richness distribution followed the Rapoport’s elevational rule. The elevational distribution of the average rarity score and the average weighted threat of the endemics resulted in low values for mid-elevation intervals and increased values for low and high altitude areas, indicating that conservation efforts should focus on the two extremes of the elevational gradient. Area prioritization methods were applied using a rarity/complementarity based algorithm with two species weighting schemes. Their results were largely congruent confirming the significance of the main mountainous areas for the conservation of the endemics. Spatial overlap among selected grid cells using the rarity/complementarity analysis and Natura 2000 network was found to be low. Our results revealed the conservation importance of at least one new area located on Kythera Island.

Floristic and phytosociological investigation of the island Antikythera and nearby islets (SW Aegean, Greece)

Abstract Tzanoudakis, D., Panitsa, M., Trigas, P. & Iatrou, G.: Floristic and phytosociological investigation of the island Antikythera and nearby islets (SW Aegean area, Greece). — Willdenowia 36 (Special Issue): 285–301. — ISSN 0511-9618;

The local endemic flora of Evvia (W Aegean, Greece)

Abstract Trigas, P. & Iatrou, G.: The local endemic flora of Evvia (W Aegean, Greece).— Willdenowia 36 (Speciar Issue): 257–270. — ISSN 0511-9618;

Identifying important areas for orchid conservation in Crete

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.

Contribution to the Study of the Greek Insular Flora: Antikythera and the Islets Around Kythera

The Kythera-Antikythera island chain is one of the most interesting areas of Greece, from a floristic and biogeographical point of view. It is considered as the remnant of an old landbridge which connected Western Crete with Southern Peloponnisos. The whole area is dominated by limestone cliffs, a biotope where many Greek and Aegean floristic elements find refuge. The island chain consists of 3 main, inhabited islands, Elafonissos, Kythera and Antikythera, and a number of small and uninhabited islets (Fig. 1). Elafonissos and Kythera are considered floristically well known (see Tzanoudakis & Panitsa 1994 for references), so we focused our efforts on the floristic exploration of the islets, which remained quite unexplored, and also to Antikythera which is the most remote and isolated among the larger ones. The latter is included in “Flora Kytherea” of Greuter and Rechinger (1967), but the floristic information are based on collections made by the authors and Prof. Phitos, during the same season (first half of May) of the same year (1964).

Multivariate morphometric analysis of Petrorhagia subsect. Saxifragae (Caryophyllaceae) in Greece, with a new species from SE Peloponnisos: P. laconica

Abstract: The intra-generic relationships within the intriguing genus Petrorhagia are currently debated, as the genus is underrepresented in recent taxonomic studies. In this study, we investigate the relationships among the species of Petrorhagia [sect. Petrorhagia] subsect. Saxifragae occurring in Greece. Based on a combination of ordination methods and discriminant analyses of 36 macromorphological characters, five species are recognized in Greece. The analyses showed that all currently known species from Greece (P. fasciculata, P. graminea, P. phthiotica and P. saxifraga) represent distinct taxonomic entities. According to our results, two recently collected populations from SE Peloponnisos represent a fifth, new Petrorhagia species, which is first described and illustrated here as P. laconica. It is related to the widespread P. saxifraga and the Greek endemic P. graminea, but clearly distinct from both species by a combination of morphological characters, including indumentum, inflorescence, calyx, capsule and seed characters. Citation: Trigas P., Kougioumoutzis K., Ermidou A. & Kalpoutzakis E. 2018: Multivariate morphometric analysis of Petrorhagia subsect. Saxifragae (Caryophyllaceae) in Greece, with a new species from SE Peloponnisos: P. laconica. — Willdenowia 48: 137–146. doi: https://doi.org/10.3372/wi.48.48110 Version of record first published online on 5 April 2018 ahead of inclusion in April 2018 issue.

The effects of presence/absence vs. continuous suitability data on reserve selection

Species distribution models are widely applied for generating the appropriate data for designing networks of reserve systems. The aim of the present study is to compare the use of presence/absence and continuous suitability data, derived from species distribution models, in reserve selection, and to detect any systematic trends in the reserve networks produced on the basis of these two types of data. The MAXENT model was applied to predict orchids’ potential distribution in east Macedonia (northeast Greece). One presence/absence and one with suitability values data set was made and used in the ZONATION decision support tool in order to prioritize the cells of the study area for inclusion in a reserve network. In the selection procedure, species weighting has been applied by using the species specialization index. Results show that the presence/absence data set favors the selection of cells with more extreme climatic conditions and more distant from the mean habitat of the study area. Furthermore, the continuous suitability data set provides higher suitability values for the specialist taxa in comparison with the presence/absence data set, while the opposite is happening for the generalist taxa. The present study reveals that the suitability data outperform the presence/absence data in reserve selection because: (a) they better represent the average environmental conditions of the study area in the selected networks; (b) they ensure higher suitability values for the specialist species, which are more prone to extinction in the future; and (c) they take full advantage of species weighting according to their habitat specificity.