Latitudinal Diversity Gradients

Description

Mind Map on Latitudinal Diversity Gradients, created by beth.ge on 12/04/2013.
beth.ge
Mind Map by beth.ge, updated more than 1 year ago
beth.ge
Created by beth.ge about 11 years ago
11
1

Resource summary

Latitudinal Diversity Gradients
  1. Biodiversity: the variety in life both within and between species and higher taxa (Any group or rank in a biological classification into which related organisms are classified)
    1. Most ecological studies focus on the taxonomic component of biodiversity, species richness (Species richness is simply the number of species present in a sample, community, or taxonomic group). But this is only one component concept biodiversity dependign on questions asked other considerations could be important.
      1. species richness only one component of species diversity alone it misses out vital info on the evenness of relative abundance of individuals of different taxa ( Evenness measures the variation in the abundance of individuals per species within a community). All else being equal, communities with greater evenness are considered to have greater species diversity. Diversity Indicies= Shannon–Wiener and Simpson’s
        1. even these measures contain no information about the relative uniqueness and importance of the taxa. Are the species contained within the taxa endemic to that area or widespread
      2. at largest scales, species richness is almost always the only diversity measure available
      3. The generality of LDG
        1. Most taxanomic groups for which we have good data show a decrease in diversity from the equator to the poles: past 400 million years but more pronounced today
          1. emphasis on higher order plants and vertibrate studied and disproportionate amount in the new world. Few studies have addressed macro-scale diversity patterns of invertebrates, parasites, bacteria and soil organisms, even though these groups comprise the majority of global biodiversity
            1. In some instances, taxa with good data are found to deviate from the classical pattern
              1. Exceptions to the latitudinal gradient generally do not occur deep in the taxonomic hierarchy (e.g. they are much more likely to occur at the family level than at the phylum level). generality of latitudinal gradient more questionable when higher taxonomic groups deviate from the global trend
          2. Investigating and Analysing Geographical Patterns of Biodiversity
            1. measuring biodiversity: scale
              1. Biodiversity is scale-dependent; that is, diversity depends strongly on the size of the units used in data collection.
                1. 3 attributes of scale particularly important in species richness studies.Grain- the area represented by each sampling point (Quadrat size). Focus- the area of the analytical unit (single or attribution of data points). Extent- total geographic area studied
                  1. species richness depends on them because of species area effect: As area increases more individuals, habitats and biomes, are incorporated, resulting in higher species richness
                    1. control for the effect of area through sampling techniques: using sample units of equal area and shape
                2. Different factors are likely to explain diversity patterning best at different scales. Potential explanatory variables make sense at some scales but not others.
                  1. The diversity of any region depends upon the richness of the smaller areas that it contains, and on the compositional turnover between these areas (turnover: the compositional change in species assemblages through either time or space)
                    1. Whittakers Scheme. Alpha diversity refers to finer scale species richness. Gamma diversity to coarser scale. Beta Diversity to species turnover at all scales
                3. Explaining the LDG
                  1. Latitude is not ecologically meaningful (interactions between organism and their environments), but correlates with variation in ecologically meaningful variables such as climate and area. Both product of contemporary processes and historical factors influencing speciation, extinction and dispersal only just starting to notice both linked
                    1. regardless of complexity of proposed causes LDG fundamentally a result of spatial variation in speciation/immigration (increasing species richness) and extinction/emigration (decreasing species richness)
                    2. hypotheses
                      1. geometric hypotheses
                        1. Area has two important, related ecological effects.
                          1. First, diversity tends to increase with area. However, this would imply that greater diversity should exist on all other great circles, but it does not, so something about latitude must explain. Tropical habitat more extensive than polar also because tropical zones contiguous where as temperate or polar are seperate
                            1. second, species of larger biomes are able to maintain larger ranges increasing the chance of allopatric speciation (speciation by geographic isolation,something extrinsic to the organisms prevents two or more groups from mating, eventually causing that lineage to speciate) and reducing extinction probability via larger potential populations and the provision of niche refugia (location of an isolated or relict population of a once more widespread species)
                              1. little testing, criticism some places dont fit the trend eg hawaii vs antarctica
                            2. the mid domain effect
                              1. diversity gradients can arise in the absence of environmental gradients from the random placement of species’ ranges in constraints of a bounded domain. species' ranges would tend to overlap more toward the center of the domain than towards its limits, forcing a mid-domain peak in species richness
                        Show full summary Hide full summary

                        Similar

                        KEE1
                        harrym
                        Romeo and Juliet essay
                        Tambo234
                        A-Level Physics: Course Overview
                        cian.buckley+1
                        IB Economics SL: Microeconomics
                        Han Zhang
                        Physics P2
                        Phoebe Drew
                        Biology -B2
                        Sian Griffiths
                        An Inspector Calls - Quotes
                        jaynejuby
                        Truman Doctrine, Marshall Plan, Cominform and Comecon
                        Alina A
                        Top learning tips for students
                        Micheal Heffernan
                        PHR and SPHR Practice Questions
                        Elizabeth Rogers8284