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"Insularity"
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Plant Biogeography and Vegetation Patterns of the Mediterranean Islands
2022
With about 11,100 islands and islets of which ca. 250 are regularly inhabited by human, the Mediterranean Sea represents one of the regions of the world with the most islands and archipelagos. These numerous islands represent a significant component of the Mediterranean biodiversity, notably with the presence of range-restricted species and peculiar vegetation types. The aim of this review is to provide a balanced view of this highly diverse phytoecological heritage, but also taking into account the medium sized islands and the smaller ones that have not been highlighted so far. Mediterranean islands constitute both a museum for ancient lineages (paleoendemic taxa) and cradle for recent plant diversification. The complex historical biogeography (paleogeographical events of the Neogene, Messinian salinity crisis, climatic and eustatic changes of the Pleistocene, influence of glacial events) has profoundly influenced the current patterns of plant diversity. These insular landscapes were also precociously impacted by prehistoric man, possibly by Neanderthals. Among the 157 large Mediterranean islands (i.e. with a surface area exceeding 10 km
2
), 49 have a surface greater than 100 km
2
. The main patterns and dynamics of vegetation on the largests islands (Balearic Islands, Corsica, Sardinia, Sicily, Croatian islands, Greek islands, Crete, Cyprus) are summarized. Then, the specific ecosystem functioning (disturbance, plant-animal interactions) and vegetation structures of the small Mediterranean islands (i.e. a surface area less than 10 km
2
or 1000 ha), are highlighted by evoking successively the small rocky islands, the volcanic ones, and the sandy and flat islands. Owing to their uniqueness and fragility, Mediterranean islands urgently need some integrated and ambitious conservation planning, aiming at the long-term preservation of their outstanding biotic and cultural heritage.
Journal Article
Functional diversity mediates macroecological variation in plant–hummingbird interaction networks
by
Fischer, Erich
,
Maglianesi, María A.
,
Rui, Ana M.
in
Apolysis trochilides
,
Biodiversity
,
climate
2018
Aim: Species interaction networks are known to vary in structure over large spatial scales. We investigated the hypothesis that environmental factors affect interaction network structure by influencing the functional diversity of ecological communities. Notably, we expect more functionally diverse communities to form interaction networks with a higher degree of niche partitioning. Location: Americas. Time period: Current. Major taxa studied: Hummingbirds and their nectar plants. Methods: We used a large dataset comprising 74 quantitative plant–hummingbird interaction networks distributed across the Americas, along with morphological trait data for 158 hummingbird species. First, we used a model selection approach to evaluate associations between the environment (climate, topography and insularity), species richness and hummingbird functional diversity as predictors of network structure (niche partitioning, i.e., complementary specialization and modularity). Second, we used structural equation models (SEMs) to ask whether environmental predictors and species richness affect network structure directly and/or indirectly through their influence on hummingbird functional diversity. For a subset of 28 networks, we additionally evaluated whether plant functional diversity was associated with hummingbird functional diversity and network structure. Results: Precipitation, insularity and plant richness, together with hummingbird functional diversity (specifically, functional dispersion), were consistently strong predictors of niche partitioning in plant–hummingbird networks. Moreover, SEMs showed that environmental predictors and plant richness affected network structure both directly and indirectly through their effects on hummingbird functional diversity. Plant functional diversity, however, was unrelated to hummingbird functional diversity and network structure. Main conclusions: We reveal the importance of hummingbird functional diversity for niche partitioning in plant–hummingbird interaction networks. The lack of support for similar effects for plant functional diversity potentially indicates that consumer functional diversity might be more important for structuring interaction networks than resource functional diversity. Changes in pollinator functional diversity are therefore likely to alter the structure of interaction networks and associated ecosystem functions.
Journal Article
Power in numbers. Drivers of high population density in insular lizards
by
Feldman, Anat
,
Kadison, Amy E.
,
Meiri, Shai
in
Competition
,
correlation
,
Density compensation
2016
AIM: Islands organisms usually have fewer predator and competitor species than mainland ones. This is thought to result in high population densities on islands. We hypothesize that insular lizards have denser populations than mainland species and that density, in general, is negatively correlated with competitor and predator richness. LOCATION: Global. METHODS: We compared densities of 346 lizard species on islands and the mainland while examining the relationship between density and, predator and competitor richness, primary productivity, seasonality and island area. We controlled for phylogenetic non‐independence, body mass and study area, which are known to strongly affect population density. RESULTS: Insular populations (especially on snake‐free islands) are denser than mainland ones. Mainland populations of lizard species that also inhabit islands were denser than those of species that do not inhabit islands. Population density was the highest on islands with low net primary productivity and was not significantly affected by competitor or predator richness. Moreover, insular populations show high density regardless of island area. MAIN CONCLUSIONS: We conclude that the ability of mainland species to reach high population densities may increase their chances in reaching and successfully colonizing islands. We postulate that population density may be affected by predator and competitor density rather than by their richness. Density increase on islands may result not from the environmental simplicity of island faunas but through propagule sorting or pressure.
Journal Article
What is the importance of islands to environmental conservation?
2017
This article discusses four features of islands that make them places of special importance to environmental conservation. First, investment in island conservation is both urgent and cost-effective. Islands are threatened hotspots of diversity that concentrate unique cultural, biological and geophysical values, and they form the basis of the livelihoods of millions of islanders. Second, islands are paradigmatic places of human–environment relationships. Island livelihoods have a long tradition of existing within spatial, ecological and ultimately social boundaries and are still often highly dependent on local resources and social cohesion. Island cultures and their rich biocultural knowledge can be an important basis for revitalizing and innovating sustainable human–nature relationships. Third, islands form a global web that interlinks biogeographic regions and cultural spaces. They are nodes in a global cultural network: as multicultural island societies, through diaspora islander communities on continents and through numerous political and trade relationships among islands and between islands and countries on continents. Fourth, islands can serve as real-world laboratories that enable scientific innovation, integration of local and generalized knowledge and social learning and empowerment of local actors. We conclude that island systems can serve as globally distributed hubs of innovation, if the voices of islanders are better recognized.
Journal Article
The Greek Archipelago: A Unique Representative Case-Study of Differential Legal Status and of Double Insularity
2021
Greece’s insular space results into the birth of a unique case of double insularity in Europe where smaller islands act as satellites of bigger ones and depend upon them much more than on the mainland. Adoption of laws, public policies, the organization of public administration and the issue of administrative acts take into account this condition. The implementation of the principle of insularity is analyzed and clarified through two case-studies, law 4361/2016 on the “Regulation of issues concerning the transfers of soldiers, personnel care and other provisions” as well as law 4551/2018 on the “Implementation mechanism, state supervision, general conditions for the implementation of the transport equivalent. Insularity should not be considered as a reason for providing unjustifiable rights and privileges, but as a principle which should be taken into consideration and respected by the legislator and the administration in order to overcome the vulnerability of the islanders and counterbalance for the harsh conditions suffered due to geographic isolation.
Journal Article
The effect of area and isolation on insular dwarf proboscideans
by
van der Geer, Alexandra A. E.
,
Due, Rokus Awe
,
van den Bergh, Gerrit D.
in
Animal behavior
,
Biological evolution
,
Body size
2016
Aim: We investigated the hypothesis that insular body size of fossil elephants is directly related to isolation and surface area of the focal islands. Location: Palaeo-islands worldwide. Methods: We assembled data on the geographical characteristics (area and isolation) of islands and body size evolution of palaeo-insular species for 22 insular species of fossil elephants across 17 islands. Results: Our results support the generality of the island rule in the sense that all but one of the elephants experienced dwarfism on islands. The smallest islands generally harbour the smallest elephants. We found no support for the hypothesis that body size of elephants declines with island isolation. Body size is weakly and positively correlated with island area for proboscideans as a whole, but more strongly correlated for Stegodontidae when considered separately. Average body size decrease is much higher when competitors are present. Main conclusions: Body size in insular elephants is not significantly correlated with the isolation of an island. Surface area, however, is a significant predictor of body size. The correlation is positive but relatively weak; c. 23% of the variation is explained by surface area. Body size variation seems most strongly influenced by ecological interactions with competitors, possibly followed by time in isolation. Elephants exhibited far more extreme cases of dwarfism than extant insular mammals, which is consistent with the substantially more extended period of deep geological time that the selective pressures could act on these insular populations.
Journal Article
Rootability confinement and soil-husbandry solutions for urban trees in sealed and insular sites
2023
AimsCramped and sealed sites common in compact city areas limit tree growth due to multiple physical restrictions and physiological stresses. Fast urbanization and densification have intensified the pressure on urban trees, demanding innovative methods and solutions. The subaerial tree-growth space attracts more attention, but the more intractable subterranean rootability constraints are often overlooked. They are expressed as external (macro-scale) soil-body volume and internal (micro-scale) soil-pore volume limitations. The double jeopardy of urban soil insularity acutely restricts root growth, root spread, tree health, and stability.MethodsSome novel solutions can be distilled from a comprehensive review of recent research findings to bring effective relief.ResultsPedestrians and vehicles can co-use the expanded soil area in dense urban areas. Various creative soil expansion techniques can allow tree roots to break out from conventional confined tree pits or tree strips. Subsurface connections can link a planting site to an adjacent one or a nearby green patch. The soil union could be realized by subsurface soil conduits (large-diameter buried pipes) or subsurface soil corridors covered by pier-supported paving. In the spirit of landscape altruism, soil sharing by neighbor trees optimizes using the scarce rootable soil resource. Internal soil volume expansion can be accompanied by high-quality soil mix and compaction-prevention measures to resolve porosity and rootability deficit.ConclusionsUrban tree managers can adopt out-of-the-box thinking in managing critical physical soil deficiencies. New research findings can more promptly inform policymakers and practitioners. Close interactions between science and practice can be proactively cultivated.
Journal Article
Evolution of personality and locomotory performance traits during a late Pleistocene island colonization in a tree frog
by
Bisconti, Roberta
,
Chiocchio, Andrea
,
Liparoto, Anita
in
Amphibians
,
Animal locomotion
,
Behavior
2023
Abstract
Recent empirical and theoretical studies suggest that personality and locomotory performance traits linked to dispersal abilities are crucial components of the dispersal syndromes, and that they can evolve during range expansions and colonization processes. Island colonization is one of the best characterized processes in dispersal biogeography, and its implication in the evolution of phenotypic traits has been investigated over a wide range of temporal scales. However, the effect of island colonization on personality and performance traits of natural populations, and how these traits could drive island colonization, has been little explored. Noteworthy, no studies have addressed these processes in the context of late Pleistocene range expansions. Here, we investigated the contribution of island colonization triggered by postglacial range expansions to intraspecific variation in personality and locomotory performance traits. We compared boldness, exploration, jumping performance, and stickiness abilities in populations from 3 equidistant areas of the Tyrrhenian tree frog Hyla sarda, 2 from the main island (Corsica Island), and 1 from the recently colonized island of Elba. Individuals from Elba were significantly bolder than individuals from Corsica, as they emerged sooner from a shelter (P = 0.028), while individuals from Corsica showed markedly higher jumping and stickiness performance (both P < 0.001), resulting as more performing than those of Elba. We discuss these results in the context of the major microevolutionary processes at play during range expansion, including selection, spatial sorting, founder effects, and their possible interaction with local adaptation processes.
Journal Article
Digestive Enzyme Activity and Temperature: Evolutionary Constraint or Physiological Flexibility?
by
Sagonas, Konstantinos
,
Paraskevopoulou, Foteini
,
Sozopoulos, Ilias
in
digestion
,
Efficiency
,
Enzymes
2025
Temperature strongly influences physiological processes in ectotherms, including digestion, yet its effects on digestive enzyme activity remain poorly understood. We examined the temperature dependence of digestive performance in eight Mediterranean wall lizard species (Podarcis spp.) from mainland and island populations. Under controlled laboratory conditions, we measured the activity of three key enzymes, protease, lipase, and maltase, across a temperature gradient (20–55 °C), alongside gastrointestinal (GI) morphology. Enzyme activity generally increased with temperature up to 50 °C and declined thereafter, reflecting typical thermal kinetics. Lipase activity was consistently higher in island species, while protease and maltase showed no significant geographic or phylogenetic trends. Island lizards also exhibited longer and heavier GI tracts relative to body size (SVL), suggesting enhanced nutrient absorption capacity. Phylogenetic signal analyses (Pagel’s λ and Abouheif’s Cmean) revealed no significant evolutionary constraints on digestive traits, indicating that observed differences reflect ecological adaptation rather than ancestry. Overall, island species appear to have evolved digestive traits that improve energy extraction under resource-limited conditions, but may be more sensitive to extreme heat. These findings highlight contrasting adaptive strategies between island and mainland reptiles and underscore the importance of digestive physiology in predicting the response of species to warming climates.
Journal Article
The Island and the Insularity at the Confluence between Disciplines
2017
The present article investigates one of universal literature’s most prolific motifs: the island. This particular motif goes beyond the boundaries of literature and becomes a subject of interest for several areas and disciplines: philosophy, anthropology, biogeography,mythology, psychoanalysis. In the context of the contemporary world, a new discipline devloped, “the nissology”, which deals with the study of the islands “in their own terms”
Journal Article