Speciation and the Latitudinal Diversity Gradient: Insights from the Global Distribution of Endemic Fish

Abstract

The nearly universal pattern that species richness increases from the poles to the equator (the latitudinal diversity gradient [LDG]) has been of intense interest since its discovery by early natural-history explorers. Among the many hypotheses proposed to explain the LDG, latitudinal variation in (1) productivity, (2) time and area available for diversification, and (3) speciation and/or extinction rates have recently received the most attention. Because tropical regions are older and were formerly more widespread, these factors are often intertwined, hampering efforts to distinguish their relative contributions to the LDG. Here we examine the global distribution of endemic lake fishes to determine how lake age, area, and latitude each affect the probability of speciation and the extent of diversification occurring within a lake. We analyzed the distribution of endemic fishes worldwide (1,933 species and subspecies from 47 families in 2,746 lakes) and find that the probability of a lake containing an endemic species and the total number of endemics per lake increase with lake age and area and decrease with latitude. Moreover, the geographic locations of endemics in 34 of 41 families are found at lower latitudes than those of nonendemics. We propose that the greater diversification of fish at low latitudes may be driven in part by ecological opportunities promoted by tropical climates and by the coevolution of species interactions.

Unexpected fish diversity gradients in the Amazon basin

“…In addition to area, results showing that energy availability and temperature were positively related to species richness are compatible with both components of the species energy hypothesis: Productivity facilitates larger population sizes, decreasing extinction rates, or allows more niche specialists to cohabit by increasing resources availability ( 16 ), and higher temperatures promote species richness by increasing metabolic rates and thus potentially speciation rates [( 22 ), but see ( 30 , 31 ) for questioning this last hypothesis] and/or by relaxing thermal constraints on species, lowering extinction rates ( 16 ). The positive effect of temperature stability on fish diversity suggests that climatically stable regions may promote lower rates of extinction through relative constancy of resources ( 32 ). Last, results showing the negative effect of habitat harshness on sub-basin richness were highly expected, as harsh habitat conditions (e.g., high elevation and steep gradients in our case) are well known to exclude fishes from successful colonization ( 33 ).…”

Latitudinal gradients of parasite richness: a review and new insights from helminths of cricetid rodents

“…Its presence has been corroborated across multiple taxa (Hillebrand 2004), including mammals (Kaufman 1995, Kaufman and Willig 1998, Buckley et al 2010, Rolland et al 2014, fish (Hobson 1994, Macpherson and Duarte 1994, Hanly et al 2017, insects (Condamine et al 2012, Fattorini and Baselga 2012, Heino et al 2015, aquatic invertebrates (France 1992, Yasuhara et al 2012a, bacteria (Pommier et al 2007, Fuhrman et al 2008, Andam et al 2016) and plants (Dobzhansky 1950, Janzen 1970, Heino and Toivonen 2008, Xu et al 2015, among others. Its presence has been corroborated across multiple taxa (Hillebrand 2004), including mammals (Kaufman 1995, Kaufman and Willig 1998, Buckley et al 2010, Rolland et al 2014, fish (Hobson 1994, Macpherson and Duarte 1994, Hanly et al 2017, insects (Condamine et al 2012, Fattorini and Baselga 2012, Heino et al 2015, aquatic invertebrates (France 1992, Yasuhara et al 2012a, bacteria (Pommier et al 2007, Fuhrman et al 2008, Andam et al 2016) and plants (Dobzhansky 1950…”

“…The LDG is generally accepted as one of the dominant biodiversity patterns on the earth. Its presence has been corroborated across multiple taxa (Hillebrand 2004), including mammals (Kaufman 1995, Kaufman and Willig 1998, Buckley et al 2010, Rolland et al 2014, fish (Hobson 1994, Macpherson and Duarte 1994, Hanly et al 2017, insects (Condamine et al 2012, Fattorini and Baselga 2012, Heino et al 2015, aquatic invertebrates (France 1992, Yasuhara et al 2012a, bacteria (Pommier et al 2007, Fuhrman et al 2008, Andam et al 2016) and plants (Dobzhansky 1950, Janzen 1970, Heino and Toivonen 2008, Xu et al 2015, among others. However, there are exceptions to the LDG, generally demonstrated when investigating latitudinal diversity patterns at smaller geographic or lower taxonomic scales.…”

The origin and evolution of coral species richness in a marine biodiversity hotspot*

“…Under that assumption, the CT is not recognizable as a center of origin for corals. However, endemism is an unreliable proxy for sites of origin and thus, by itself, should not be used to test macroevolutionary models of diversity gradients (Goldberg et al 2005;Bellwood and Meyer 2009;Cowman 2014; but see Hanly et al 2017).…”