Commonness and rarity in species distribution Sophia Qian

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) Mc. Gill 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 (Mc. Gill 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