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Nonlinear thermal gradients shapebroad-scale patterns in geographic rangesize and can reverse Rapoport’s rule

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Nonlinear thermal gradients shapebroad-scale patterns in geographic rangesize and can reverse Rapoport’s rule

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RESULTS:
The temperature limited model predicts that species macroecological thermal ranges show initially increase with increasing latitudinal range along all three margins.
As predicted by the temperature limited model, the empirical bivalve data along the western margins of ocean basins show that geographically broad ranging species tend to have smaller thermal ranges than intermediate range species.
The temperature limited model predicts that latitudinal ranges will be significantly greater at low altitudes than at high latitudes in the western margins.

DISCUSSION:
Therefore, species broader latitudinal ranges tend to occupy widespread, relatively constant temperature, rather than being generalist that occupy the broad temperature range.
The empirical patterns also show a tropical maximum in latitudinal range size. this maximum is significantly greater than predicted by the null model in the western pacific and western atlantic.
Other factors related to range expansion also inversely relationship between latitudinal range size and latitude. For example, a decrease in dispersal limitation towards the tropics related to the frequency of species with highly

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Discussion
-Rapoport's rule and the latitudinal gradient in species richness arise from similar ecological process
-Natural selection favor the wide climatic tolerance of individuals in high lattitude areas thus, their distribution shows greater latitudinal extent than species in low lattitudes.

Rapoport Rule
-Produce latitudinal gradient in species richness
-Organism in low lattitude have narrow tolerance for climatic conditions than high lattitude species
-Rapoport Suggest that tropical organism have narrow environmental tolerance that temperate or polar organism that lead to greater spatial heterogeneity and discontinuity of areas where that organism do well
-Also state that if low lattitude species have narrow environmental tolerance then equal dispersal abilities in two group will place more tropical oraganism out of their preferred habitat than higher lattitude species out of their preferred habitat . To be conclude, large number of accidentals (species that poorly suited for habitat) occur in tropical assemblages. The constant input of these accidentals inflates species number and inhibits competitive exclusion

Exception to rapoport rule
-The pattern of latitudinal extent of Soviet bird breeding distribution is exceptional
-The observation that organism migrating long distance do not show the Rapoport's rule phenomenon

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Only partially hypothesis from the articles support the hypothesis of Rapoport's Rule.

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1. Nonlinear thermal Gradient shape broad-scale patterns in geographic range size and can reverse Rapoport's rule

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1. Nonlinear thermal Gradient shape broad-scale patterns in geographic range size and can reverse Rapoport's rule

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Rapoport's rule hypothesis:

Species living at latitudes that have greater annual temperature variations are expected to achieve broader geographic ranges than species living at latitudes that have smaller annual temperature variation.

Range size and latitude have positive relationship.

Research paper hypothesis:

The nonlinear relationship between temperature and latitude within each hemisphere, with weaker spatial variation in annual minimum, mean and maximum daily temperature at low than at mid latitudes can be apply in both terrestrial and marine environments.

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4. Unifying latitudinal gradients in range size richness across marine and terrestrial systems.

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4. Unifying latitudinal gradients in range size richness across marine and terrestrial systems.

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Invalidating hypothesis : Gradients in species richness by specific range-size dynamics rather than by gradients in net species diversification.

They hypothesize
that genus-level patterns shared across the marine and terrestrial
environments reflect commonalities in the propensity of
species-rich genera to expand to new latitudes.

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Rapoport's rule is an ecogeographical rule that states that latitudinal ranges of plants and animals are generally smaller at lower latitudes than at highet latitudes.

This rule named after Eduardo H. Rapoport by Stevens (1989).

The rule is use to explain greater species diversity in the tropica in the sense that latitudinal gradients in species diversity.

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The generalization of Rapoport’s Rule

-Steven (1992) demonstrate that animals and plants generally have fewer species on mountain top than in the low land.

-He also adding the definition of Rapoport’s Rule: “there exist a correlation between the mean geographical breadth of taxa occurring at any particular point along a biogeographical gradient and the relative position of the point along the gradient”

- However, there are two important objections to his method:

a) Colwell & Hurtt (1994) – a spurious Rapoport’s Rule effect can be caused by sampling bias alone

b) Roy, Jablonski & Valentine (1994) – means of data for latitudinal ranges used by Stevens (1989) are ‘inappropriate measures of central tendency, given the strong non-normal distributions of species latitudinal ranges, for any given latitudinal band’

The explanation of the ‘latitudinal’ Rapoport’s Rule

- Rapoport’s Rule has never been shown to apply any animal group in the tropics.

-However, it has been demonstrated for several group above latitudes of approximately 40-50°N

-There are many animals like mammal and fishes cannot be verified to follow this rule by many scientists.

-Data available to date suggest that an increase in latitudinal ranges with latitude occurs only in animals of northern land masses from mid to high latitudes.

Explanation of latitudinal gradients in species richness

-Rapoport’s Rule is just one of the many ‘explanations’ of the much greater species diversity in tropical than in the cold environment.

-such ‘explanations’ are usually based on supposed correlation of particular parameter with species diversity.

-However, Rohde (1992) has shown there are always exception to the correlation, and even the correlation were perfect, it would not constitute proof for the cause of latitudinal gradient in species richness.

-the latitudinal Rapoport’s Rule has never been shown to apply in group of tropical animals.

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1. Nonlinear thermal gradients shape broad-scale patterns in geographic range size can reverse Rapoport's rule. (2016)

2.  Rapoport's rule - The latitudinal gradient in geographical ranges: How so many species coexist in the tropics. (1989)

3.  Rapoport's rule is a local phenomenon and cannot explain latitudinal gradient in species diversity. (1996)Unifying latitudinal gradients in range size richness across marine and terrestrial systems.(2018)

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4. Unifying latitudinal gradients in range size richness across marine and terrestrial systems.

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4. Unifying latitudinal gradients in range size richness across marine and terrestrial systems.

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# Marine and Terrestrial

Have similar latitudinal gradients in species richness.

but opposite gradient in range size. ( Land > range size smaller at tropic) (Sea > range size bigger at tropic)

# Terrestrial bird and marine bivalves

They find that gradient range size are concordant at the level of genera.

Both group show a nested pattern in which narrow-ranging genera are confined to the tropics and broad-ranging genera extend across much of the gradient.

1. Genus range size and its variation with latitude is closely associated with per-genus species richness.

2. Broad-ranging genera contain more species both within and outside of the tropics when compared with tropical or temperate region (only genera).

Despite underlying differences in the species range-size gradients, species-rich genera are more likely to produce a descendant that extends its range relative to the ancestor’s range.

# Extent of the study system and through time.

Species in terrestrial clades (e.g. birds, mammals, amphibians, insects, and trees) tend to have smaller latitudinal ranges in the tropics and increase towards mid-latitudes, at least across the Northern Hemisphere.

Latitudinal ranges in marine clades (e.g. teleost fish, corals, bivalves, and brachyuran crabs) tend to be broadest in the tropics and decline towards the poles.

Invalidating hypothesis : Gradients in species richness by specific range-size dynamics rather than by gradients in net species diversification.

A positive correlation between range size and latitude can arise in two way:

1. Narrow-ranging taxa may be replaced by broad-ranging taxa towards high latitudes in the absence of a latitudinal gradient in range overlap (Rapoport's Rule).

2. Narrow-ranging taxa may be nested within the distributions of broad-ranging taxa, with an increasing number of narrow-ranging taxa towards low latitudes.

# Discussion and summary

Bivalves and birds show discordant latitudinal gradients in species range size that we suggest result from the biogeographic behaviour of clades during and after Pleistocene glaciations, and reflect general differences in environmental heterogeneity between marine and terrestrial systems.

The two groups share a latitudinal gradient in species and genus richness, mean per-genus species richness and genus range size, with higher latitudes increasingly enriched in broad-ranging and (globally) species-rich genera as diversity declines.

These shared patterns at the genus level suggest that species richness gradients originate independently of species range-size gradients in both groups, and support a simple underlying process whereby genera with higher net species diversification are more likely to enter novel latitudes and climates than are species-poor genera.

Evolutionary and biogeographic dynamics appear to be closely tied.

They hypothesize
that genus-level patterns shared across the marine and terrestrial
environments reflect commonalities in the propensity of
species-rich genera to expand to new latitudes.

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Eventhough tropical species have narrower microecological thermal ranges than high latitude species, the constant temperature over wide areas of tropics allow tropical species to achieved broad latitudinal ranges.

Null Model
The method used are the Null Model. This model shows the geographic ranges places on the ocean surface independently of thermal gradient.

Range Expansion Model
the second model is by using the Range Expansion Model. These model shows the minimum and maximum temperature encompassed by geographic range of a species which positively related to the annual temperature where species originated.

It is proven with the model that shows inversely relationship between range size and the latitude, which is opposite with the Rapoport Rule. Thus, only a few hypothesis accept by the Rapoport Rule while others are a failure.