Global diversity patterns of freshwater fishes – potential victims of their own success

Abstract

Aim To examine the pattern and cumulative curve of descriptions of freshwater fishes world-wide, the geographical biases in the available information on that fauna, the relationship between species richness and geographical rarity of such fishes, as well as to assess the relative contributions of different environmental factors on these variables. Location Global.Methods MODESTR was used to summarize the geographical distribution of freshwater fish species using information available from data-based geographical records. The first-order jackknife richness estimator was used to estimate the completeness of such data in all terrestrial 1-degree cells world-wide. An a-shape procedure was used to build range maps capable of providing relatively accurate species richness and geographical rarity values for each grid cell. We also examined the explanatory capacity of a high number of environmental variables using multiple regressions and Support Vector Machine. ResultsCumulative species description curves show that a high number of species of freshwater fishes remain to be discovered. Completeness values indicate that only 199 one-degree grid cells, mainly located in eastern North America and Europe, could be considered as having relatively accurate inventories. Range maps provide species richness values that are positively and significantly related to those resulting from the first-order jackknife richness estimator. The relationship between species richness and geographical rarity is triangular, so that these species-rich cells are those with a higher proportion of distributionally rare species. Species richness is predicted by climatic and/or productivity variables but geographical rarity is not.Main conclusions In general, species-rich tropical areas harbour a higher number of narrowly distributed species although comparatively species-poor subtropical cells may also contain narrowly distributed species. Historical factors may help to explain the faunistic composition of these latter areas; a supposition also supported by the low predictive capacity of climatic and productivity variables on geographical rarity values.

Fish and amphibians as bat predators

“…In fishes, almost all records were located in North and South America, two regions with the highest global diversity of freshwater fishes (Pelayo-Villamil et al 2015). Similarly, majority of bat-hunting incidences by amphibians were from Neotropical, Australian and Nearctic regions, which are again characterised by really high diversity of amphibians (AmphibiaWeb 2015b).…”

Factors influencing when species are first named and estimating global species richness

“…Freshwater fish species inventories have been found most complete in Europe and eastern North America, and least in southern South America, Northern Africa and west Asia (Pelayo-Villamil et al, 2015). While a greater proportion of species discovered in less explored locations will be new to science, the actual number of species new to science may still come from the already explored but species rich areas.…”

“…This is because areas with most species tend to have the most rare and geographically restricted (i.e. endemic) species in freshwater (Pelayo-Villamil et al, 2015) and marine (Costello unpublished data) environments. …”

“…Other estimates of how many fish species remain to be discovered ranged from 2%-30%: namely 30% (i.e. 5,000 or 22%) of all marine fish (Eschmeyer et al, 2010;Costello et al, 2012); 12%-15% of tropical East Pacific fish (Zapata and Robertson, 2007); 2%-5% of freshwater fish in Europe (Essl et al, 2013); and 13% (2,300) of freshwater fish globally (Pelayo-Villamil et al, 2015).…”

FactorsR: An RWizard Application for Identifying the Most Likely Causal Factors in Controlling Species Richness

“…Some comparative studies in environmental applications have shown that SVM outperforms MR or other modeling techniques [9][10][11][12][13]. SVM has been successfully applied to explain the factors affecting species richness of marine elasmobranchs [14] and of freshwater fish species [15].…”