Synthesis reveals that island species–area relationships emerge from processes beyond passive sampling

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.

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Maintenance of biodiversity on islands

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2016.0102 ◽

2016 ◽

Vol 283 (1829) ◽

pp. 20160102 ◽

Cited By ~ 22

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).

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

Organisms Diversity & Evolution ◽

10.1007/s13127-021-00523-x ◽

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.

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Model averaging fails to improve the extrapolation capability of the island species–area relationship

Journal of Biogeography ◽

10.1111/jbi.13598 ◽

2019 ◽

Author(s):

Thomas J. Matthews ◽

Thomas W. H. Aspin

Keyword(s):

Model Averaging ◽

Island Species ◽

Species Area ◽

Species Area Relationship

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A framework for disentangling ecological mechanisms underlying the island species–area relationship

Frontiers of Biogeography ◽

10.21425/f5fbg40844 ◽

2019 ◽

Vol 11 (1) ◽

Cited By ~ 12

Author(s):

Jonathan M. Chase ◽

Leana Gooriah ◽

Felix May ◽

Wade A. Ryberg ◽

Matthew S. Schuler ◽

...

Keyword(s):

Island Species ◽

Species Area ◽

Ecological Mechanisms ◽

Species Area Relationship

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Using Network Analysis to Explore the Role of Dispersal in Producing and Maintaining Island Species–Area Relationships

The Species–Area Relationship ◽

10.1017/9781108569422.021 ◽

2021 ◽

pp. 368-398

Author(s):

Joseph A. Veech ◽

Giovanni Strona

Keyword(s):

Network Analysis ◽

Island Species ◽

Species Area

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Explaining Variation in Island Species–Area Relationship (ISAR) Model Parameters between Different Archipelago Types: Expanding a Global Model of ISARs

The Species–Area Relationship ◽

10.1017/9781108569422.007 ◽

2021 ◽

pp. 51-77

Author(s):

Thomas J. Matthews ◽

François Rigal ◽

Konstantinos Proios ◽

Kostas A. Triantis ◽

Robert J. Whittaker

Keyword(s):

Global Model ◽

Model Parameters ◽

Island Species ◽

Species Area ◽

Species Area Relationship

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Boreal ground-beetle (Coleoptera: Carabidae) assemblages of the mainland and islands in Lac la Ronge, Saskatchewan, Canada

The Canadian Entomologist ◽

10.4039/tce.2017.12 ◽

2017 ◽

Vol 149 (4) ◽

pp. 491-503 ◽

Cited By ~ 2

Author(s):

Aaron J. Bell ◽

Iain D. Phillips ◽

Scott E. Nielsen ◽

John R. Spence

Keyword(s):

Species Richness ◽

Island Biogeography ◽

Passive Sampling ◽

Unit Area ◽

Ground Beetle ◽

Small Islands ◽

Island Size ◽

Extinction Rates ◽

Theory Of Island Biogeography ◽

Species Area

AbstractWe tested the applicability of the “passive sampling” hypothesis and theory of island biogeography (TIB) for explaining the diversity of forest-dwelling carabid assemblages (Carabidae: Coleoptera) on 30 forested islands (0.2–980.7 ha) in Lac la Ronge and the adjacent mainland in Saskatchewan, Canada. Species richness per unit area increased with distance to mainland with diversity being highest on the most isolated islands. We detected neither a positive species-area relationship, nor significant differences in species richness among island size classes, or between islands and the mainland. Nonetheless, carabid assemblages distinctly differed on islands <1 ha in area and gradually approached the structure of mainland assemblages as island area increased. Small islands were characterised by abundant populations of small-bodied, winged species and few if any large-bodied, flightless species like Carabus taedatus Fabricius. Our findings suggest that neither the “passive sampling” hypothesis nor the theory of island biogeography adequately explain carabid beetle diversity patterns observed among islands in Lac la Ronge. Instead, we hypothesise that population processes such as higher extinction rates of large-bodied, flightless species and the associated release of smaller-bodied, flying species from intra-guild predation on small islands contribute to observed differences in the structure of carabid assemblages between islands.

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