The Hydrachnidia (water mites) represent the most important group of the Arachnida in fresh water. Over 6000 species have been described worldwide, representing 57 families, 81 subfamilies and more than 400 genera. The paper analyzes extant water mite diversity and biogeography. Data on distribution and species richness of water mites are substantial but still far from complete. Many parts of the world are poorly investigated, Oriental and Afrotropical regions in particular. Moreover, information among different freshwater habitats is unbalanced with springs and interstitial waters disproportionately unrepresented. Therefore, more than 10,000 species could be reasonably expected to occur in inland waters world-wide. Based on available information, the Palaearctic region represents one of the better investigated areas with the highest number of species recorded (1642 species). More than 1000 species have been recorded in each of the Neotropical (1305 species) and Nearctic regions (1025 species). Known species richness is lower in Afrotropical (787 species) and Australasian (694 species) regions, and lowest in the Oriental region (554 species). The total number of genera is not correlated with species richness and is distinctly higher in the Neotropical (164 genera); genus richness is similar in the Palaearctic, Nearctic and Australasian regions (128-131 genera) and is lower in the Afrotropical and Oriental regions with 110 and 94 genera, respectively. A mean number of about three genera per family occur in the Palaeartic, Nearctic and Oriental while an average of more than four genera characterizes the families of Australasian and Afrotropical regions and more than five genera those of the Neotropical. Australasian fauna is also characterized by the highest percentage of endemic genera (62 %), followed by Neotropical (50.6 %) and Afrotropical (47.2 %) regions. Lower values are recorded for the Palaearctic (26.9 %), Oriental (24.4 %) and Nearctic (21.4 %). The Palaearctic and Nearctic have the higher faunistic similarity, some minor affinities are also evident for the generic diversification of Holarctic and Oriental families. The faunas of Southern Hemisphere bioregions are more distinct and characterized by the presence of ancient Gondwanan clades with a regional diversification particularly evident in the Neotropics and Australasia. This scenario of water mite diversity and distribution reflect the basic vicariance pattern, isolation, phylogenetic diversification, recent climatic vicissitudes and episodes of dispersal between adjacent land masses together with extant ecological factors can be evoked to explain distribution patterns at a global scale.

Global diversity of water mites (Acari, Hydrachnidia; Arachnida) in freshwater

CICOLANI, Bruno;
2008-01-01

Abstract

The Hydrachnidia (water mites) represent the most important group of the Arachnida in fresh water. Over 6000 species have been described worldwide, representing 57 families, 81 subfamilies and more than 400 genera. The paper analyzes extant water mite diversity and biogeography. Data on distribution and species richness of water mites are substantial but still far from complete. Many parts of the world are poorly investigated, Oriental and Afrotropical regions in particular. Moreover, information among different freshwater habitats is unbalanced with springs and interstitial waters disproportionately unrepresented. Therefore, more than 10,000 species could be reasonably expected to occur in inland waters world-wide. Based on available information, the Palaearctic region represents one of the better investigated areas with the highest number of species recorded (1642 species). More than 1000 species have been recorded in each of the Neotropical (1305 species) and Nearctic regions (1025 species). Known species richness is lower in Afrotropical (787 species) and Australasian (694 species) regions, and lowest in the Oriental region (554 species). The total number of genera is not correlated with species richness and is distinctly higher in the Neotropical (164 genera); genus richness is similar in the Palaearctic, Nearctic and Australasian regions (128-131 genera) and is lower in the Afrotropical and Oriental regions with 110 and 94 genera, respectively. A mean number of about three genera per family occur in the Palaeartic, Nearctic and Oriental while an average of more than four genera characterizes the families of Australasian and Afrotropical regions and more than five genera those of the Neotropical. Australasian fauna is also characterized by the highest percentage of endemic genera (62 %), followed by Neotropical (50.6 %) and Afrotropical (47.2 %) regions. Lower values are recorded for the Palaearctic (26.9 %), Oriental (24.4 %) and Nearctic (21.4 %). The Palaearctic and Nearctic have the higher faunistic similarity, some minor affinities are also evident for the generic diversification of Holarctic and Oriental families. The faunas of Southern Hemisphere bioregions are more distinct and characterized by the presence of ancient Gondwanan clades with a regional diversification particularly evident in the Neotropics and Australasia. This scenario of water mite diversity and distribution reflect the basic vicariance pattern, isolation, phylogenetic diversification, recent climatic vicissitudes and episodes of dispersal between adjacent land masses together with extant ecological factors can be evoked to explain distribution patterns at a global scale.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11697/19097
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