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- In defence of the entity of Macaronesia as a biogeographical regionPublication . Fernández‐Palacios, José María; Otto, Rüdiger; Capelo, Jorge; Caujapé‐Castells, Juli; De Nascimento, Lea; Duarte, Maria Cristina; Elias, Rui B.; García‐Verdugo, Carlos; Menezes de Sequeira, Miguel; Médail, Frédéric; Naranjo‐Cigala, Agustín; Patiño, Jairo; Price, Jonathan; Romeiras, Maria M.; Sánchez‐Pinto, Lázaro; Whittaker, RobertSince its coinage ca. 1850 AD by Philip Barker Webb, the biogeographical region of Macaronesia, consisting of the North Atlantic volcanic archipelagos of the Azores, Madeira with the tiny Selvagens, the Canaries and Cabo Verde, and for some authors different continental coastal strips, has been under dispute. Herein, after a brief introduction on the terminology and purpose of regionalism, we recover the origins of the Macaronesia name, concept and geographical adscription, as well as its biogeographical implications and how different authors have positioned themselves, using distinct terrestrial or marine floristic and/or faunistic taxa distributions and relationships for accepting or rejecting the existence of this biogeographical region. Four main issues related to Macaronesia are thoroughly discussed: (i) its independence from the Mediterranean phytogeographical region; (ii) discrepancies according to different taxa analysed; (iii) its geographical limits and the role of the continental enclave(s), and, (iv) the validity of the phytogeographical region level. We conclude that Macaronesia has its own identity and a sound phytogeographical foundation, and that this is mainly based on three different floristic components that are shared by the Macaronesian core (Madeira and the Canaries) and the outermost archipelagos (Azores and Cabo Verde). These floristic components are: (i) the Palaeotropical-Tethyan Geoflora, formerly much more widely distributed in Europe and North Africa and currently restricted to the three northern archipelagos (the Azores, Madeira and the Canaries); (ii) the African Rand Flora, still extant in the coastal margins of Africa and Arabia, and present in the southern archipelagos (Madeira, the Canaries and Cabo Verde), and (iii) the Macaronesian neoendemic floristic component, represented in all the archipelagos, a result of allopatric diversification promoted by isolation of Mediterranean ancestors that manage to colonize Central Macaronesia and, from there, the outer archipelagos. Finally, a differentiating floristic component recently colonized the different archipelagos from the nearest continental coast, providing them with different biogeographic flavours.
- Functional diversity and community convergence of land snails in the Aegean Sea islandsPublication . Proios, Konstantinos; Maroulis, Leonidas; Rigal, François; Matthews, Thomas J.; Cameron, Robert A. D.; Sfenthourakis, Spyros; Whittaker, Robert; Vardinoyannis, Katerina; Mylonas, Moissis; Triantis, KostasABSTRACT: Aim: Island biological communities are considered to comprise non-random assem-blages from surrounding source pools, but whether they converge towards predictable structural properties remains unclear. Here, we (i) test whether insular communities of land snails converge towards similar functional and/or taxonomic properties and (ii) evaluate whether island functional diversity is determined by island biogeographical characteristics such as area and distance to the pool as well as human-related variables.Location: Sixty-six continental Aegean islands.Taxon: Land snails. Methods: We compiled a database of two morphological traits with functional sig-nificance (shell height and width) for 163 island species and 1529 species from the major species pools. We quantified inter-specific morphological dissimilarity between pairs of islands (turnover), using a modified index of the mean nearest taxon distance. We tested for functional and taxonomic convergence using null models and assessing whether overall mean turnover among islands and pairwise island-by-island turnover were lower than expected by chance. We performed multiple regression analyses to test whether functional diversity metrics scale with island biogeographical character-istics and human-related variables. Results: Our analyses provide strong evidence that communities of land snails across the Aegean islands converge towards non-random functional properties and taxonomic structure. At the island level, a wide range of different shell shapes is observed, indicating greater functional richness than expected by chance. Regression analyses showed that island area is the only efficient predictor of functional diversity, indicating that available ecological/resource space is of central importance in driving the assembly of different shell shapes. Main Conclusions: Our findings, consistent with previous studies of other taxa from oceanic islands, highlight that island species communities are not randomly assembled and display convergence in their functional and taxonomic composition. Integrating functional diversity metrics within biogeographic analyses has the potential to further our understanding of island biodiversity patterns.
- Power-law scaling in intratumoral microbiota of colorectal cancerPublication . Dovrolis, Nikolas; Gazouli, Maria; Rigal, François; Whittaker, Robert; Matthews, Thomas J.; Georgiou, Konstantinos; Theodoropoulos, George; Triantis, KostasIt has recently been proposed that the study of microbial dynamics in humans may gain insights from island biogeographical theory. Here, we test whether the diversity of the intratumoral microbiota of colorectal cancer tumors (CRC) follows a power law with tumor size akin to the island species-area relationship. We confirm a direct correlation between the quantity of Amplicon Sequence Variants (ASVs) within CRC tumors and tumor sizes, following a (log)power model, explaining 47% of the variation. Understanding the processes involved, potentially through the analogy of tumors and islands, may ultimately contribute to future clinical and therapeutic strategies.