Many oceanic islands are notable for their high endemism, suggesting that islands may promote unique assembly processes. However, mainland assemblages. Y.E. Stuart, J. B. Losos, and A. C. Algar. “The island-mainland species turnover relationship.” Proceedings of the Royal Society Biological Sciences, . The species-area relationship (SAR) is one of the most thoroughly Two theories have been proposed to explain SARs: classical island The Slopes of the SARs for Island Communities are Steeper Compared to Mainland.
This article has been cited by other articles in PMC. Abstract Many oceanic islands are notable for their high endemism, suggesting that islands may promote unique assembly processes. However, mainland assemblages sometimes harbour comparable levels of endemism, suggesting that island biotas may not be as unique as is often assumed. Here, we test the uniqueness of island biotic assembly by comparing the rate of species turnover among islands and the mainland, after accounting for distance decay and environmental gradients.
We modelled species turnover as a function of geographical and environmental distance for mainland M—M communities of Anolis lizards and Terrarana frogs, two clades that have diversified extensively on Caribbean islands and the mainland Neotropics.
If island assembly is not unique, then the M—M model should successfully predict M—I and I—I turnover, given geographical and environmental distance. We found that M—I turnover and, to a lesser extent, I—I turnover were significantly higher than predicted for both clades. Thus, in the first quantitative comparison of mainland—island species turnover, we confirm the long-held but untested assumption that island assemblages accumulate biodiversity differently than their mainland counterparts.
The island–mainland species turnover relationship
Introduction Oceanic islands and archipelagos are often characterized by high rates of endemism [ 1 ] that probably result from rapid speciation anagenetic and cladogenetic on islands of sufficient area and isolation [ 2 — 7 ].
For example, the Hawaiian Archipelago hosts several classic adaptive radiations, including silverswords and honeycreepers.Stan Tatkin Healthy Relationships, Becoming Anchors for Others
The oft-cited pattern of high island endemism suggests that a unique combination of processes may govern assembly on islands.
However, many mainland areas also house endemic biotas with endemism levels that can rival the classic adaptive radiations of oceanic islands [ 8 ], especially in mountainous habitat islands characterized by dispersal barriers and steep environmental gradients [ 9 ].
Even in less mountainous regions, differences in habitat type, climatic gradients or spatial separation can lead to substantial turnover across space [ 1011 ]. The existence of mainland communities that harbour similar levels of endemism to islands suggests that island and mainland assembly may be more similar than currently recognized and that islands may not be the unique generators of diversity they have long been assumed to be.
Here, we focus on species turnover along geographical and environmental gradients to test for an island effect on biotic assembly. Mainland—island species diversity relationships have been, and remain, a stimulus of evolutionary and biogeographic theory [ 712 — 14 ]. However, the predominant focus has been on the species richness of individual islands relative to the mainland.
In contrast, the mainland—island relationship for species turnover remains undescribed and unexplored.
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Their data are plotted below, using the log10 of the area and species number. The two data points furthest to the right represent, from left to right, South Florida the area south of Lake Okeechobee and the entire state of Florida.
All other data points are from the Keys. We can also plot the log10 of species number against the log10 of the distance of the islands from the Florida mainland.
The relationship between the log10 of the species number and the log10 of island area clearly shows an increasing trend, and is well-approximated by the linear form of the model.
The island–mainland species turnover relationship
Similarly, a decreasing trend of species number with island distance can be seen from the second graph. Whether or not the number of species is at equilibrium is less clear; interpretation of the data regarding this question is made more difficult by uncertainty about the history of sea-level changes over the past 10, years. Both island size and distance from the mainland are associated with the number of species present.
In general, it has been found that the relationship between island area and number of species present is fairly constant for islands in a given geographic region. In this way it is possible to make potentially useful predictions about the number of species on islands or habitat islands when little information other than size is available.
For conservation planning, knowledge of this relationship is of utmost importance. Estimate the equation for a line fitting the data in the graph of log10 species number by log10 distance.