Patterns and drivers of species richness and turnover of neo-endemic and palaeo-endemic vascular plants in a Mediterranean hotspot: the case of Crete, Greece

Abstract

BackgroundExploring species richness and turnover patterns and their drivers can provide new insights into underlying mechanisms shaping community assembly, with significant implications for biodiversity conservation. Here, we explored diversity patterns of non-endemic, neo-endemic and palaeo-endemic vascular plants in Crete, Greece, a Mediterranean hotspot of plant richness and endemism. We evaluated the relationship between α-diversity and environmental (bioclimatic variables, topography), and anthropogenic variables by Generalized Additive Models, after accounting for spatial autocorrelation. Then, we quantified turnover using the novel concept of zeta diversity (the number of shared species by multiple sites), a framework which allows to explore the full spectrum of compositional turnover, the contribution of rare and widespread species to observed patterns and the underlying processes shaping them. Finally, we explored the abiotic and biotic effects, i.e. how well one category of species (non-endemics, palaeo-endemics, neo-endemics) predicts the patterns of the other categories, on zeta diversity by multi-site Generalized Dissimilarity Modelling.ResultsWe found a strong correlation between neo-endemic and palaeo-endemic α-diversity, with climate, topography, and human impact driving species richness. Zeta diversity analysis revealed a sharper decrease of shared palaeo-endemic species, followed by neo-endemics, and then by non-endemics with the number of sites considered to estimate compositional turnover. Perhaps, the narrow distributions of palaeo-endemics as relict species and often habitat specialists, thus persisting locally, and of neo-endemics that may have not reached yet their potential geographical range, resulted in the observed zeta diversity decline pattern. Deterministic processes controlled species turnover of rare non-endemic and neo-endemic species, while deterministic and stochastic processes contributed similarly to palaeo-endemic turnover. However, stochasticity dominates in the case of widespread species in all occasions. The environmental and anthropogenic variables were poor predictors of compositional turnover, especially of widespread species. However, the non-endemic species composition was correlated to rare palaeo-endemics and neo-endemics, highlighting the importance of biotic effects in driving turnover patterns.ConclusionsIt seems that centers of neo-endemism of vascular plants coincide with centers of palaeo-endemism in Crete, but species richness and species turnover are shaped by different drivers.

Management implications based on diversity patterns under climate change scenarios in a continental island biodiversity hotspot

“…In this context, altitudea proxy of environmental heterogeneity (e.g., Cabral et al, 2014) emerged as the most important predictor of PE and RPE in Crete, followed by MDR, pH and CS. Niche-related processes thus seem to play a minor role in generating endemism patterns in Crete, which is in line with previous studies at a coarser scale (Lazarina et al, 2019). Distinct endemism patterns may be found in sites with phylogenetically distinct assemblages, even if environmental similarity is high, due to phylogenetically conserved niche breadth and dispersal ability (Wiens and Graham, 2005).…”

“…After all, the most important gradient for determining SIEC turnover is PET, followed by geographical distance (Figs. S21-22) and niche-based processes were found to exert some influence in the distribution of species occurring in Crete (Lazarina et al, 2019). These regional variation shifts in beta diversity could disrupt ecosystem functioning and provisioning of ecosystem services (Cardinale et al, 2012).…”

Spatial Phylogenetics, Biogeographical Patterns and Conservation Implications of the Endemic Flora of Crete (Aegean, Greece) under Climate Change Scenarios

“…It is a speciation center for animal and plant taxa (e.g., [ 60 , 102 ] and references therein), due to its rugged topography, past climatic stability, environmental heterogeneity and long-term isolation, all being crucial factors promoting lineage diversification and persistence [ 17 , 103 ]. Palaeogeographical history, mountain uplift and climate have shaped Crete’s biodiversity and biogeographical patterns (e.g., [ 59 , 104 , 105 ]). Climate change is expected to modify biodiversity and biogeographical patterns globally [ 6 ], with islands and mountain summits exhibiting higher vulnerability to these impacts (e.g., [ 33 , 37 ]).…”

Multi‐site generalized dissimilarity modelling reveals drivers of species turnover in ectoparasite assemblages of small mammals across the northern and central Palaearctic

“…Despite its recent development, MS-GDM has been successfully used for investigating the drivers of compositional turnover in several taxa at various scales and in a number of geographic regions (Baird, Janion-Scheepers, Stevens, Leihy, & Chown, 2019;Krasnov et al, 2020;Latombe et al, 2017;Latombe, Richardson, Richardson, Pyšek, Kučera, & Hui, 2018;Latombe, Roura-Pascual, & Hui, 2019;Lazarina et al, 2019).…”

“…Given the exclusion of species with an increasing zeta order, the relative contribution of each predictor to the explained variation in turnover is expected to vary between zeta orders (Latombe et al., 2017). Despite its recent development, MS‐GDM has been successfully used for investigating the drivers of compositional turnover in several taxa at various scales and in a number of geographic regions (Baird, Janion‐Scheepers, Stevens, Leihy, & Chown, 2019; Krasnov et al., 2020; Latombe et al., 2017; Latombe, Richardson, Richardson, Pyšek, Kučera, & Hui, 2018; Latombe, Roura‐Pascual, & Hui, 2019; Lazarina et al., 2019).…”