Transcript Commonness and rarity

Commonness and rarity in species distribution
Sophia Qian Niu
Graduate seminar: Lost in space
Concepts and terms
Commonness and rarity regards species distribution patterns across
geographic rage
- Rabinowitz, 1982
‘Seven kind of rarity determined by three properties’
Concepts and terms
Shoener, 1994
Suffusive rarity characterizes a species that is rare
everywhere and the species' range is completely covered or
filled; diffusive rarity characterizes a species that is rare in
certain parts of its range but common in other parts
Occurrence and abundance rarity should be correlated,
while the correlation should not be symmetrical: seldomencountered species is likely to be very scarce but nonabundant species is not necessarily rare
Concepts and terms
Species-abundance distribution (SAD)
McGill et al., 2007
- describes abundance of all species in a local community, while spatial issue
is important it may not be directly incorporated in SAD (e.g. logserires,
lognormal, power law distribution)
- seeks for ecological process that drive the observed pattern, and to
understand community structure in general, and also interested in species
commonness and rarity, but approaches this question quite differently
-build models on different process (e.g. Lotka-Volterra, niche partitioning,
metacommunity, and neutral theory), compare predicted and observed SAD
Example of SAD and effects of spatial scale
(McGill et al., 2007; Ulrich et al., 2008)
Why patterns on commonness and rarity is important?
Central question in biogeographic and conservation biology
- conservation concerns: having species exhibiting high rates
of extinction relative to others will lead to rare species
- nature of community structure and biodiversity pattern: how
does commonness-rarity pattern vary among taxonomic
groups, geographic location, and species richness
- mechanistic explanation on why species become common
and rare?
Commonness and rarity patterns
Australian birds (Shoener, 1987)
- determine whether it is diffusive or suffusive rarity
- how does this pattern change among taxonomic groups
Commonness and rarity patterns
Commonness and rarity patterns
Results
- effects of quadrat size
- distributions of range size are strikingly skewed toward small
number of quadrats (most of species have restricted range)
- diffusive rarity (rare in some quadrat but not rare in others)
- more species are common across their occurrence range
- range size is negatively correlated with abundance
Commonness and rarity patterns
Results
- effects of quadrat size
- distributions of range size are strikingly skewed toward small
number of quadrats (most of species have restricted range)
- diffusive rarity (rare in some quadrat but not rare in others)
- more species are common across their occurrence range
- range size is negatively correlated with abundance
Commonness and rarity patterns
North American Freshwater Fishes (Pritt and Primtong, 2010)
Commonness and rarity patterns
Tree Species in Upper Amazonian Forests (Pitman et al., 2001; did not
consider the geographic rage; more like SAD, and overall density is used)
Commonness and rarity patterns
Pitman et al. (2001)
-Many common species: 150 common out of 300-500 species.
Ecuadorean taxa accounted for 15-22% of all species, 56-68% of total
basal area, and 63-73% of all stems inventoried in Ecuador and Peru
forests
-Common species showed taxonomic pattern whereas rarity did not
-No correlation between range size and abundance; monoecious
species are more common (recruitment)
Commonness and rarity patterns
Island: Core, satellite and uniform (Mehranvar and Jackson, 2001)
Commonness and rarity patterns
Island: Core, satellite and uniform (Mehranvar and Jackson, 2001)
Less core species on Oceanic island than land bridge: on oceanic island
species never shared an ancestral biota, thus their potential for being core
species is low (opportunistic dispersal and colonization)
Common species showed
higher correlation with
overall species richness
pattern (e.g. Cucherousset et
al., 2008)
Why species became common and rare –
historical, genetic and ecological processes
1) Phylogenetic constrains (nonrandom rarity)/traits-related
Cornwell and Arkly, 2010
(i) Among co-occurring taxa, do species’ traits correlate with abundance
and rarity?
(ii) Does the relationship between traits and abundance change at different
spatial scales or in different abiotic contexts?
Why species became common and rare
Relationships were seen from plot
scale, not the landscape scale;
Some traits-abundance
relationship varied along
environmental gradient
Nonneutral, trait-based processes
play an important role in
determining abundance within
local communities
Why species became common and rare
2) Demographic process
Münzbergova (2005)
Seed predation that manifests to growth rate rather than seed mass is
the key factor causing a lower population growth rate in the rare
species
The combination of full demography with data on the intensity of seed
predation in two related species differing in rarity and sharing the
same habitat demonstrated significantly lower population growth rates
in the rare species
Why species became common and rare
2) Demographic process
Münzbergova (2005)
Why species became common and rare
3) Resource use (Tale et al., 2008)
Testing alternative hypotheses of resource use and niche
breath - species of high abundance and wide range is
associated with resources distribution that are also wide
spread and unlimited (not correlated with niche breadth
cf. resource or habitat specialization)
Why species became common and rare
4) Genetic variation (Cole, 2003; Honnay & Acquemyn, 2006)
The reduction in gene flow among populations of rare species was
significant when estimated from inbreeding coefficient FST
Genetic differentiation among population is not different between
common and rare species. Genetic variation between common and
rare species is not clear-cut, they are equality vulnerable to habitat
fragmentation
Why species became common and rare
5) History – intrinsically rare: lineages (or populations that
experience speciation) were geographically isolated; due to
climate and geologic changes some have chances to expend the
range and persist (become common), some do not (remain rare)
6) Rarity showed consistency along time due to competitive
exclusion and stochastic effects (Ferriere and Cazelles, 1999)
7) Dispersal ability and opportunities (metacommunity model):
poorly understand, but with evidences from island (e.g.
Mehranvar and Jackson, 2001).
They are not mutually exclusive, and many more under-studied