Numbers of Bird Species on the California Islands

Power, Dennis M.

doi:10.2307/2407019

Cited by 51 publications

(34 citation statements)

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“…Other investigators have found that indices of environmental diversity such as the number of plant species on an island explained more variance in bird species numbers than area (Watson 1964, Powers 1972. In contrast, I have found that, for just the older deep-water islands, area alone is the best predictor.…”

Section: The Number Of Lizard Species_mentioning

confidence: 72%

Species Numbers, Density Compensation, and Colonizing Ability of Lizards on Islands in the Gulf of California

Case¹

1975

Ecology

170

116

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The distribution of lizard species and numbers on islands in the Gulf of California was examined in light of island biogeographic theory. Using linear multiple regression techniques with the percent completeness of the island's lizard fauna as the dependent variable (LS), the relationship and predictive power of several island independent variables (in original and transformed forms) were explored. The results of this analysis differed sharply for different subsets of islands. The independent variable accounting for the most variance in LS for oceanic islands was island area; their distance from the mainland explained most of the residual variance. For land—bridge islands, maximum island elevation was the most predictive single variable, and island distance was least important. In both these island groups and considering all the islands together, island area, elevation, and the number of perennial plant species were highly correlated and explained little of each others residual variance. On 12 islands, diversity of shrub volume was also measured and was found to have less predictive power than the other variables considered. Life history attributes of each lizard species were gleaned from the literature and compared with the respective colonizing abilities of the species. In general species occurring on many Gulf islands (e.g., Uta stansburiana) may reach high mainland population densities, have potentially high birth rates and high death rates, and may be habitat generalists. Species absent from most islands and most likely to go extinct on land—bridge islands (e.g., Xantusia vigilis) have the converse of these attributes. The reasons for the divergence of these results and those expected from predictions is discussed. Lizard fauna relaxation times were calculated for land—bridge islands and were found to be inversely related to island area as predicted from island biogeographic theory. Extinction rates for lizards are about one half as high as those calculated for birds and mammals. Timed searches for lizards were also performed on most of the islands and the adjacent Baja California peninsula. These revealed that the numbers of Uta and total lizard numbers were both inversely related to the number of lizard species occupying an island. The probable reasons for such excess density compensation were examined, and it was concluded that differences in pedation intensity, insect productivity, and possibly competitive interference account for the extremely high number of lizards on some small isolated islands.

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Section: The Number Of Lizard Species_mentioning

confidence: 72%

Species Numbers, Density Compensation, and Colonizing Ability of Lizards on Islands in the Gulf of California

Case¹

1975

Ecology

170

116

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“…This means that larger islands and islands closer to the mainland are predicted to have a lower extinction rate and a higher immigration rate, respectively, than smaller and more isolated ones, both resulting in higher species diversity. The importance of both parameters has been verified by several empirical studies (Kalmar & Currie, 2006;Power, 1972;Simpson, 1974).…”

mentioning

confidence: 73%

Island biogeography theory explains the genetic diversity of a fragmented rock ptarmigan (Lagopus muta) population

Costanzi

Steifetten

2019

Ecology and Evolution

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The island biogeography theory is one of the major theories in ecology, and its applicability to natural systems is well documented. The core model of the theory, the equilibrium model of island biogeography, predicts that species diversity on an island is positively related to the size of the island, but negatively related by the island's distance to the mainland. In recent years, ecologists have begun to apply this model when investigating genetic diversity, arguing that genetic and species diversity might be influenced by similar ecological processes. However, most studies have focused on oceanic islands, but knowledge on how the theory applies to islands located on the mainland (e.g., mountain islands, forest islands) is scarce. In this study, we examined how the size and degree of isolation of mountain islands would affect the genetic diversity of an alpine bird, the rock ptarmigan ( Lagopus muta ). Within our study area, we defined the largest contiguous mountain area as the mainland, while smaller mountains surrounding the mainland were defined as islands. We found that the observed heterozygosity ( H o ) was significantly higher, and the inbreeding coefficient ( F is ) significantly lower, on the mainland compared to islands. There was a positive significant relationship between the unbiased expected heterozygosity ( H n.b. ) and island size (log km 2 ), but a negative significant relationship between H o and the cost distance to the mainland. Our results are consistent with the equilibrium model of island biogeography and show that the model is well suited for investigating genetic diversity among islands, but also on islands located on the mainland.

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“…Soil drainage heterogeneity exerted a greater effect on total plant species richness than area (Table 3), thus allowing it to be used as a more precise independent predictor of biodiversity. Aspects of geomorphology are more directly correlated with species diversity than area itself in other studies (Koopman 1958;MacArthur 1964;Power 1972;Johnson 1975).…”

Section: Refuge Sizementioning

confidence: 83%

The Influence of Geomorphological Heterogeneity on Biodiversity II. A Landscape Perspective

Nichols¹,

Killingbeck²,

August³

1998

Conservation Biology

162

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The influence of geomorphological heterogeneity on vascular plant species richness was studied in 26 Rhode Island Audubon refuges ranging in size from 1.4 to 58.6 ha. Indices of abiotic heterogeneity reflecting spatial variation in slope, aspect, and soil drainage were calculated from extant databases in a geographic information system. After removing the influence of refuge size on both biotic diversity and geomorphological heterogeneity, vascular plant species richness was found to be highly related to geomorphological heterogeneity. Diversity in soil drainage class alone accounted for more than 50% of the variance in total plant species richness ( r 2 ϭ 0.53, p Ͻ 0.001) and was significantly related to the species richness of 10 of the 11 life-form classes of plants studied. When two refuges considered to be mathematical and biological outliers were removed from the regression analysis, soil drainage heterogeneity accounted for more than 65% of the variance in total plant species richness ( r 2 ϭ 0.67, p Ͻ 0.001). Aspect heterogeneity, slope heterogeneity, and the composite index of all three measures of geomorphological heterogeneity were each less related to total plant richness than soil drainage heterogeneity alone, but they were all more effective at predicting richness of native woody species ( r 2 ϭ 0.23-0.45, p Ͻ 0.05) than soil drainage heterogeneity ( r 2 ϭ 0.08, p Ͼ 0.05). In a stepwise multiple regression analysis, soil drainage heterogeneity and refuge size explained 66% ( p Ͻ 0.001) of the variation in species richness (soil drainage heterogeneity, partial r 2 ϭ 0.39; refuge size, partial r 2 ϭ 0.27). These results explicitly support the tenet that geomorphological heterogeneity plays a major role in determining species richness. Because biotic and abiotic diversity were intricately linked at the scale of the landscape, conservation of geomorphological heterogeneity may be an effective strategy for conserving biodiversity.

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Numbers of Bird Species on the California Islands

Cited by 51 publications

References 0 publications

Species Numbers, Density Compensation, and Colonizing Ability of Lizards on Islands in the Gulf of California

Species Numbers, Density Compensation, and Colonizing Ability of Lizards on Islands in the Gulf of California

Island biogeography theory explains the genetic diversity of a fragmented rock ptarmigan (Lagopus muta) population

The Influence of Geomorphological Heterogeneity on Biodiversity II. A Landscape Perspective

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