The increase in species diversity with decreasing latitude, or high tropical species richness, is an ecological pattern that has long intrigued naturalists1. ⦠The pattern of increasing biological diversity from high latitudes to the equator [latitudinal diversity gradient (LDG)] has been recognized for > 200 years.
This ranks among the broadest and most notable biodiversity patterns on Earth. Despite lack of consensus on the issue, some evolutionary ecologists including Brown & Lomolino 1998, Farrell et al. We examined the applicability of three versions of the energy hypothesis, the habitat heterogeneity hypothesis, and historical contingency to the gradient of terrestrial birds.
1993). Faster speciation and reduced extinction in the tropics contribute to ⦠1. no one compelling (consensual) explanation 2. hypothesis not mutually exclusive. turris) and the northern limit of several cold-water species Several historical, evolutionary and ecological (e.g. Of course, we now refer to the ï¬rst part of the pattern as the ââlatitudinal diversity gradient,ââ and the second as a ââspeciesâarea relationship The latitudinal diversity gradient is the largest scale, and longest known, pattern in ecology. Several hypotheses have been proposed but until now ecological ones have predominated over half a century. Because γ diversity varies along both latitudinal and elevational gradients, its influence on α and β diversity must be accounted for before any ecological explanations are offered. Given the myriad ways biological diversity can overlap in space, understanding the distribution of range sizes may help use reduce the number of diversity hypotheses we have to test. Oikos 65 514â527 10.2307/3545569 [Google Scholar] Rolland J., Condamine F. L., Jiguet F., Morlon H. (2014). Introducing the LDG. A problem with this gradient is that it conflates two key explanations, namely biome stabil ⦠4 Differential contribution of mammalian orders to the latitudinal gradient of species richness in the New World based on data from 5 degree latitudinal bands. The latitudinal gradient in diversity (LDG) remains one of the most well-known but least-understood patterns in ecology and evolution (Willig et al., 2003; Hillebrand, 2004).A phylogenetic perspective is increasingly recognized as crucial for a mechanis-tic explanation (Wiens & ⦠empirical data to assess whether the diversity patterns of fish fauna along 4000 km of the Chilean coast (20°â55° S) can be explained in relation to the environmental latitudinal gradient. Because of the tilt of the earth on its axis, the tropics receive direct solar energy for a greater proportion of the year compared to higher latitudes (temperate and polar zones). Nature 405: 220-227. Environmental stress affects species richness and diversity in communities, but the precise form of the relationship is unclear. The latitudinal diversity gradient describes the phenomenon in which the diversity of species inhabiting biomes is higher near the equator and lower near the poles. But our documentation of a latitudinal gradient in bacteria suggests otherwise.
Explanation: This idea is also referred to as the latitudinal diversity gradient, meaning that as you move from the equator towards the poles, diversity lessens. Processes that can produce latitudinal gradients in the diversity of stream invertebrate assemblages are demonstrated, indicating that flood disturbance varying with latitude may influence abundance and local extinction rates of rare species, consequently affecting ⦠At low levels of disturbance, more competitive organisms will push subordinate species to extinction and dominate the ecosystem. Here we review two major hypotheses for the origin of the latitudinal diversity gradient. 1. spatial heterogeneity hypothesis 2. competition hypothesis 3. predation hypothesis 4. mutualism and coevolution hypothesis. Latitudinal diversity gradients are among the most striking patterns in nature. latitudinal gradient in species richness, the latitudinal gradient in species geographical range size (Rapoportâs rule), species geographical range boundaries and patterns of invasion in the tropics. Read on to learn more about existing hypotheses that attempt to explain why this gradient exists, and how scientists may benefit from considering more than one hypothesis at a⦠The latitudinal diversity gradient (LDG) is the most pernicious of problems. gradients in species richness (e.g.
This method was called the midpoint method. 2000. Surprisingly though, after decades of study, a universally accepted explanation for the latitudinal diversity gradient remains elusive. The tropical conservatism hypothesis has been proposed as a general explanation for the latitudinal diversity gradient that links the ecological factors correlated with species richness patterns (e.g., climate) to the evolutionary and biogeographic processes that ultimately cause these patterns (e.g., speciation, continentalâscale dispersal). ers on time as an explanation for the latitudinal diversity gradient has waxed and waned over the years (Stephens & Wiens, 2003), re-cent studies that have inferred colonization and diversification his-tory simultaneously have found a strong role for time in explaining richness patterns (Economo et al., 2018; Jansson et al., 2013; Li & to explain this latitudinal diversity gradient [10,11], the number of species in a given clade and region is ultimately explained by four major components: the time since the clade colonized the region, speciation rates, extinction rates, and dispersal events [12]. Biotic interactions are believed to play a role in the origin and maintenance of species diversity, and multiple hypotheses link the latitudinal diversity gradient to a presumed gradient in the importance of biotic interactions. 1998). Latitudinal gradients of biodiversity are biogeographic patterns that quantify the ways in which taxonomic, phylogenetic, functional, genetic, or phenetic biodiversity change with latitudinal position on the surface of the earth (Fig. We note that one group of marine protists, planktonic foraminiferans, have long been known to have a global latitudinal gradient of diversity , with 90% of the variability explained by temperature .
Surprisingly though, after decades of study, a universally accepted explanation for the latitudinal diversity gradient remains elusive. Another major problem with Rapoportâs rule con-cerns the relationships between the latitudinal diversity gradient, latitudinal trends in potential range extents, and observed patterns (Kolasa et al.
Explanations for the latitudinal correlation with species rich- Academia.edu is a platform for academics to share research papers. Poleward declines in the number of species are known for terrestrial, aquatic, coastal marine and pelagic marine biotas, but the explanation for these patterns remains a challenge for theoretical ecology (Gaston 2000). However, most analyses of historical inï¬uences on the present-day latitudinal diversity gradient have focused on how origi-nation and/or diversiï¬cation rates vary with latitude (pat-terns of extinction remain poorly known) and have ig- Latitudinal species diversity gradients (LSDGs) are among the most conspicuous biogeographic patterns on Earth. As only three processes (specia-tion, extinction and dispersal) can directly affect species richness in areas, similar factors may be responsible for both classical (high tropical diversity) and inverse (high temperate diversity) gradients. Location Data were taken from North and South America, Europe, Asia, Africa and oceanic islands. The latitudinal diversity gradient (LDG) is one of the most striking ecological patterns on our planet.
Our findings constitute a latitudinal gradient in functional diversity, paralleling recent findings in other taxa. explanation for the latitudinal diversity gradient remains elusive. Here we address whether biotic interactions are more important at low latitudes, finding support for this hypothesis from a wide range of interactions. changes in a and g diversity, we use two data sets of woody plants. Latitudinal gradients in species diversity Species richness, or biodiversity, increases from the poles to the tropics for a wide variety of terrestrial and marine organisms, often referred to as the latitudinal diversity gradient (LDG) [1].The LDG is one of the most widely recognized patterns in ecology [1].The LDG has been observed to varying degrees in Earth's past. Latitudinal diversity gradients are among the most striking patterns in nature.
Molecules diffuse from areas of high concentration, to areas of low concentration, down a concentration gradient. The concentration gradient therefore represents the concept that, just as a ball rolls down a slope, during diffusion molecules move down the concentration gradient. The time and area hypothesis holds that tropical climates are o ⦠The latitudinal diversity gradient is the largest scale, and longest known, pattern in ecology. Climate is the most often cited explanation of the latitudinal species diversity gradient. Elevational diversity gradient (EDG) is an ecological pattern where biodiversity changes with elevation.The EDG states that species richness tends to increase as elevation increases, up to a certain point, creating a "diversity bulge" at middle elevations. Keywords Climate change, evolutionary time, extinction, latitudinal gradient, mean root distance, New World birds, palaeoclimate, species diversity, species. Three kinds of explanations have been proposed for the gradient: ecological hypotheses that focus on mechanisms of species coexistence and the maintenance of species diversity (Fig. Allen, A. P., and Gillooly, J. F. 2006.
A cradle: At least some marine species tend to originate in the tropics. A latitudinal diversity gradient in planktonic marine bacteria Jed A. Fuhrman, Joshua A. Steele, Ian Hewson, Michael S. Schwalbach, Mark V. Brown, ... consensus explanation (1-6).
instead seek a general explanation for the slope (b) of the LDG (Log 10 S a b Latitude, where S is the number of taxa from a given clade in a fixed area, and a is the esti-mated number of taxa found at the equator) and test this explanation with a standardized dataset. The pattern of having lots of species at the equator with diversity dwindling off towards the poles is known as the Latitudinal Diversity Gradient â âlatitudinalâ meaning how far north or south of the equator, âdiversityâ meaning the number of species, and âgradientâ meaning the transition between high and low. Nonetheless, notable exceptions to the general pattern exist, and it is well recognized that patterns may be dependent on characteristics of spatial scale and taxonomic hierarchy. We examined the applicability of three versions of the energy hypothesis, the habitat heterogeneity hypothesis, and historical contingency to the gradient of terrestrial birds. Description. Gradient level reads the current slope as a percentage. Often used on roads and railroads to indicate the steepness of a grade. Many model railroaders use this while building layouts. Gradient level works in auto mode to read the grade from any of the 6 sides of a device automatically. The intermediate disturbance hypothesis (IDH) suggests that local species diversity is maximized when ecological disturbance is neither too rare nor too frequent. We note that one group of marine protists, planktonic foraminiferans, have long been known to have a global latitudinal gradient of diversity , with 90% of the variability explained by temperature .