scholarly journals Evaluating the correlation between area, environmental heterogeneity, and species richness using terrestrial isopods (Oniscidea) from the Pontine Islands (West Mediterranean)

2021 ◽  
Author(s):  
Gabriele Gentile ◽  
Roberto Argano ◽  
Stefano Taiti
Keyword(s):  
Species Richness ◽  
Environmental Heterogeneity ◽  
Geographic Distance ◽  
Habitat Diversity ◽  
Tyrrhenian Sea ◽  
Island Species ◽  
Random Placement ◽  
Species Area ◽  
Pontine Islands ◽  
Volcanic Islands

AbstractArea and environmental heterogeneity influence species richness in islands. Whether area or environmental heterogeneity is more relevant in determining species richness is a central issue in island biogeography. Several models have been proposed, addressing the issue, and they can be reconducted to three main hypotheses developed to explain the species-area relationship: (1) the area-per se hypothesis (known also as the extinction-colonisation equilibrium), (2) the random placement (passive sampling), and the (3) environmental heterogeneity (habitat diversity). In this paper, considering also the possible influence of geographic distance on island species richness, we explore the correlation between area, environmental heterogeneity, and species richness by using faunistic data of Oniscidea inhabiting the Pontine Islands, a group of five small volcanic islands and several islets in the Tyrrhenian Sea, located about 60 km from the Italian mainland. We found that the colonisation of large Pontine Islands may occur via processes independent of geographic distance which could instead be an important factor at a much smaller scale. Such processes may be driven by a combination of anthropogenic influences and natural events. Even in very small-size island systems, environmental heterogeneity mostly contributes to species richness. Environmental heterogeneity could influence the taxocenosis structure and, ultimately, the number of species of Oniscidea via direct and indirect effects, these last mediated by area which may or may not have a direct effect on species richness.

scholarly journals Insights into the late-Sixties taxocenosis of Oniscidea from the Pontine islands (West Mediterranean) (Peracarida: Isopoda)

2019 ◽  
Vol 51 (2) ◽  
pp. 217-223
Author(s):  
Gabriele Gentile ◽  
Roberto Argano ◽  
Stefano Taiti
Keyword(s):  
Research Program ◽  
Environmental Conditions ◽  
Small Island ◽  
National Council ◽  
Tyrrhenian Sea ◽  
Number Of Species ◽  
Pontine Islands ◽  
Volcanic Islands ◽  
Very High

We report and discuss faunistic data of Oniscidea inhabiting the Pontine islands, a group of five small volcanic islands and several islets in the Tyrrhenian Sea, located about 60 km from the Italian mainland. Data here presented were primarily obtained from the examination of the material collected during a three-year (1965-1968) research program supported by the Italian National Council of Research and aimed at investigating Mediterranean small island faunas, including Oniscidea. Despite the sampling was not specifically directed at Oniscidea, these data may provide insights into the structure of the Oniscidean taxocenosis of the islands as it existed fifty years ago. Thirty-five species belonging to 11 families, 8 ecological and 7 biogeographical classes were found on these islands. Such number of species of Oniscidea is very high, if we consider the low number of islands and their small sizes. Changes in climate and environmental conditions occurred in the last fifty years would call for a new investigation.

scholarly journals A global model of island species–area relationships

2019 ◽  
Vol 116 (25) ◽  
pp. 12337-12342 ◽  
Author(s):  
Thomas J. Matthews ◽  
François Rigal ◽  
Kostas A. Triantis ◽  
Robert J. Whittaker
Keyword(s):  
Species Richness ◽  
Structural Equation ◽  
Negative Relationship ◽  
Equation Model ◽  
Local Scale ◽  
Ecological Process ◽  
Global Pattern ◽  
Island Species ◽  
Species Area ◽  
Globally Distributed

The increase in species richness with island area (ISAR) is a well-established global pattern, commonly described by the power model, the parameters of which are hypothesized to vary with system isolation and to be indicative of ecological process regimes. We tested a structural equation model of ISAR parameter variation as a function of taxon, isolation, and archipelago configuration, using a globally distributed dataset of 151 ISARs encompassing a range of taxa and archipelago types. The resulting models revealed a negative relationship between ISAR intercept and slope as a function of archipelago species richness, in turn shaped by taxon differences and by the amount and disposition of archipelago area. These results suggest that local-scale (intra-archipelago) processes have a substantial role in determining ISAR form, obscuring the diversity patterns predicted by island theory as a function of archipelago isolation. These findings have implications for the use and interpretation of ISARs as a tool within biogeography, ecology, and conservation.

Organisation de la richesse et de la composition floristiques d'îles de la Méditerranée occidentale (sud-est de la France)

1998 ◽  
Vol 76 (2) ◽  
pp. 321-331 ◽  
Author(s):  
Frédéric Médail ◽  
Éric Vidal
Keyword(s):  
Species Richness ◽  
Species Composition ◽  
Plant Species ◽  
Habitat Diversity ◽  
Mediterranean Islands ◽  
Plant Dispersal ◽  
Number Of Species ◽  
Continental Islands ◽  
Species Area ◽  
Species Area Relationship

The effects of physiographic variables (area, isolation, elevation, and substrate) and habitat diversity on plant species richness and composition have been investigated on some Mediterranean islands (southeastern France). The number of species - area relationship is significant but there are more diverse vegetation patterns on smallest islands (area smaller than 3.5 ha and, ultimately, 0.2 ha). Although the species composition is positively correlated to the distance from the continent, the effect of isolation is not so obvious because of the small distance of these continental islands from the continent. Some islands nearest to shore show very different plant species composition, suggesting a nonselective plant dispersal through some narrow stretches of sea. Habitat diversity represents one of the major explanatory factors of the species richness; nevertheless, it is not possible to settle between the two hypotheses effect of habitat diversity versus effect of area per se because of the correlation between the two factors. Key words: Mediterranean islands, insular biogeography, number of species - area relationship, isolation, habitat diversity, islets.

scholarly journals Maintenance of biodiversity on islands

2016 ◽  
Vol 283 (1829) ◽  
pp. 20160102 ◽  
Author(s):  
Ryan A. Chisholm ◽  
Tak Fung ◽  
Deepthi Chimalakonda ◽  
James P. O'Dwyer
Keyword(s):  
Species Richness ◽  
Island Biogeography ◽  
Mechanistic Model ◽  
Neutral Theory ◽  
Small Island ◽  
Small Islands ◽  
Island Area ◽  
Island Species ◽  
Theory Of Island Biogeography ◽  
Species Area

MacArthur and Wilson's theory of island biogeography predicts that island species richness should increase with island area. This prediction generally holds among large islands, but among small islands species richness often varies independently of island area, producing the so-called ‘small-island effect’ and an overall biphasic species–area relationship (SAR). Here, we develop a unified theory that explains the biphasic island SAR. Our theory's key postulate is that as island area increases, the total number of immigrants increases faster than niche diversity. A parsimonious mechanistic model approximating these processes reproduces a biphasic SAR and provides excellent fits to 100 archipelago datasets. In the light of our theory, the biphasic island SAR can be interpreted as arising from a transition from a niche-structured regime on small islands to a colonization–extinction balance regime on large islands. The first regime is characteristic of classic deterministic niche theories; the second regime is characteristic of stochastic theories including the theory of island biogeography and neutral theory. The data furthermore confirm our theory's key prediction that the transition between the two SAR regimes should occur at smaller areas, where immigration is stronger (i.e. for taxa that are better dispersers and for archipelagos that are less isolated).

Island Species Richness Increases with Habitat Diversity

2009 ◽  
Vol 174 (6) ◽  
pp. E205-E217 ◽  
Author(s):  
Joaquín Hortal ◽  
Kostas A. Triantis ◽  
Shai Meiri ◽  
Elisa Thébault ◽  
Spyros Sfenthourakis
Keyword(s):  
Species Richness ◽  
Habitat Diversity ◽  
Island Species

scholarly journals Calling for a new strategy to measure environmental (habitat) diversity in Island Biogeography: a case study of Mediterranean tenebrionids (Coleoptera: Tenebrionidae)

2015 ◽  
Vol 47 (1) ◽  
pp. 1 ◽  
Author(s):  
Simone Fattorini ◽  
Leonardo Dapporto ◽  
Giovanni Strona ◽  
Paulo A.V. Borges
Keyword(s):  
Species Richness ◽  
Land Cover ◽  
Island Biogeography ◽  
Environmental Heterogeneity ◽  
Habitat Diversity ◽  
Central Mediterranean ◽  
Environmental Diversity ◽  
New Strategy ◽  
Per Se

Many recent researches in island biogeography attempted to disentangle the effects of area <em>per se</em> and “habitat diversity” on species richness. However, the expression “habitat diversity” in this context should be avoided, because habitats can be only recognized by referring to the resources needed by a particular species. What is really measured in such researches is some form of “environmental heterogeneity”. Although habitat heterogeneity can be measured in various ways, most researches in island biogeography simply used the number of biotopes (typically classified as land cover categories). However, not all biotopes have the same surface. On the basis of the area occupied by each land cover category, it is possible to calculate indices of environmental diversity, evenness and dominance, as commonly done in community ecology research. These indices can be used to investigate the role of environmental diversity in determining species richness. We used the tenebrionid beetles inhabiting twenty-five small islands around Sicily (Central Mediterranean) to illustrate these concepts. We found that both area per se and environmental heterogeneity contributed to determine species richness. Moreover, we found that the relationship between species richness and environmental homogeneity followed a power function model. This indicates that environmental homogenization may determine a rapid, non linear decline in species richness.

scholarly journals Island species-area relationships in the Andaman islands emerge because rarer species are disproportionately favored on larger islands

2019 ◽  
Author(s):  
Leana D. Gooriah ◽  
Priya Davidar ◽  
Jonathan M. Chase
Keyword(s):  
Species Richness ◽  
Random Sampling ◽  
Common Species ◽  
Sampling Effort ◽  
Island Species ◽  
Total Species Richness ◽  
Species Area ◽  
Using Data ◽  
Species Richness And Abundance ◽  
Total Species

AbstractThe Island Species-Area relationship (ISAR) describes how the number of species increases with increasing size of an island (or island-like habitat), and is of fundamental importance in island biogeography and conservation. Here, we use a framework based on individual-based rarefactions to infer whether ISARs result from random sampling, or whether some process are acting beyond sampling (e.g., disproportionate effects and/or habitat heterogeneity). Using data on total and relative abundances of four taxa (birds, butterflies, amphibians and reptiles) across the Andamans and Nicobar archipelago, we examine how different metrics of biodiversity (total species richness, rarefied species richness, and abundance-weighted effective numbers of species emphasizing common species) vary with island area. Total species richness increased for all taxa, as did rarefied species richness for a given sampling effort. This indicates that the ISAR did not result because of random sampling, but that instead, species were disproportionately favored on larger islands. This disproportionate effect was primarily due to changes in the abundance of rarer species, because there was no effect on the abundance-weighted diversity measure for all taxa except butterflies. Furthermore, for the two taxa for which we had plot-level data (lizards and frogs), within-island β -diversity did not increase with island size, suggesting that heterogeneity effects were unlikely to be driving these ISARS. Overall, our results indicate that the ISAR of these taxa is most likely because rarer species are more likely to survive and persist beyond that which would have been expected by random sampling alone, and emphasizes the role of these larger islands in the preservation and conservation of species.

scholarly journals Urbanization and species-energy relationships

2018 ◽  
Author(s):  
Lucas M. Leveau
Keyword(s):  
Species Richness ◽  
Primary Productivity ◽  
Positive Relationship ◽  
Environmental Heterogeneity ◽  
Negative Relationship ◽  
Habitat Diversity ◽  
Bird Abundance ◽  
Bird Richness ◽  
Urban Rural ◽  
Energy Relationships

AbstractSpecies-energy relationships (SER) have been used scarcely to predict responses of biodiversity to changes in land use. In this work, two hypothesis of the SER were tested on bird communities along urbanization gradients: the increasing population size (IPS) and the niche position (NP) hypotheses. The IPS hypothesis states that sites with more primary productivity have more individuals, decreasing the probability of extinction and increasing species richness. The HPN predicts that sites with greater primary productivity and environmental heterogeneity allow the availability of a greater variety of resources and the presence of specialist species, thus increasing species richness. The hypothesis of habitat heterogeneity was evaluated by which more complex habitats provide more variety of resources and greater species richness. Birds were counted along three urban-rural gradients in the Pampean region of Argentina during the breeding season. The productive energy was measured from the NDVI and the environmental heterogeneity through the Shannon-Wiener diversity index, calculated with the percentage coverage of different substrates. Bird richness and habitat diversity were higher at intermediate levels of urbanization, while primary productivity had a negative relationship with urbanization. Although there was a positive relationship between bird richness and abundance, there was no positive relationship between bird abundance and primary productivity. Bird richness showed a positive relationship with habitat diversity and primary productivity; although path analysis revealed that the habitat diversity increased bird richness through an increase of bird abundance. The NP hypothesis was the most consistent to predict the bird richness along urban-rural gradients.

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