Local adaptation
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Local adaptation is when a population of organisms evolves (adapts) to be more well-suited to its local environment than other members of the same species. Local adaptation requires that different populations of the same species experience different natural selection, due to differences in the abiotic or biotic environment the populations occupy. For example, if a species lives across a wide range of temperatures, populations from warm areas may have better heat tolerance than populations of the same species that live in the cold part of its geographic range. More formally, a population is said to be locally adapted[1] if organisms in that population have evolved different phenotypes than other populations of the same species, and local phenotypes have higher fitness in their home environment compared to individuals that originate from other locations in the species range [2][3].
Testing for local adaptation
Local adaptation is often determined via reciprocal transplant experiments, where organisms from one population are transplanted into another population, and vice versa, and their fitness is measured.[3] If the local transplants outperform (i.e. have higher fitness than) the foreign transplants, the local population is said to be locally adapted[3]. Before 2004, reciprocal transplants sometimes considered populations locally adapted if the population experienced its highest fitness in its home site vs the foreign site (i.e. compared the same population at multiple sites, vs. multiple populations at the same site). This definition of local adaptation has been largely abandoned after Kawecki and Ebert argued convincingly that populations could be adapted to poor-quality sites but still experience higher fitness if moved to a more benign site [3].
Local adaptation can be defined simply as home site advantage of one populations (local sources outperform foreign sources at a common site). In this case it can be tested using common garden experiments, where multiple source populations are grown in a common site, as long as one of the source populations is local to that site. A stricter definition of local adaptation is reciprocal home site advantage, where for a pair of populations each out performs the other in its home site[4][2]. Under this definition local adaptation can only be tested for using reciprocal transplant experiments (multiple sources transplanted to multiple sites).
Reciprocal transplants have most often been done with plants or other organisms that do not move [4].
Frequency of local adaptation
Several meta-analyses have attempted to quantify how common local adaptation is, and generally reach similar conclusions. Roughly 75% of transplant experiments (mostly with plants) find that local populations outcompete foreign populations at a common site, but less than 50% find the reciprocal home site advantage that defines classic local adaptation [4][5].
Drivers of local adaptation
Populations from different environments may be faced with different biotic and abiotic pressures,[6] consequently natural selection may drive the evolution of these populations in different directions.
Examples of local adaptation abound in the natural world. For instance, many plant populations exhibit local adaptation.[7][8][9] Many examples of local adaptation exist in host-parasite systems as well. For instance, a host may be resistant to a locally-abundant pathogen or parasite, but conspecific hosts from elsewhere where that pathogen is not abundant may have no evolved no such adaptation. [10]
See also
References
- ^ Williams, George (1966). Adaptation and Natural Selection. Princeton: Princeton University Press.
- ^ a b Leimu, Roosa (December 23, 2008). "A meta-analysis of local adaptation in plants". PLoS ONE. 3 (12): e4010. doi:10.1371/journal.pone.0004010. PMC 2602971. PMID 19104660.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ a b c d Kawecki, Tadeusz J.; Ebert, Dieter (2004-12-01). "Conceptual issues in local adaptation" (PDF). Ecology Letters. 7 (12): 1225–1241. doi:10.1111/j.1461-0248.2004.00684.x. ISSN 1461-0248.
- ^ a b c Hereford, Joe (2009). "A Quantitative Survey of Local Adaptation and Fitness Trade‐Offs". The American Naturalist. 173 (5): 579–588. doi:10.1086/597611. ISSN 0003-0147.
- ^ Leimu, Roosa; Fischer, Markus (2008). Buckling, Angus (ed.). "A Meta-Analysis of Local Adaptation in Plants". PLoS ONE. 3 (12): e4010. doi:10.1371/journal.pone.0004010. ISSN 1932-6203. PMC 2602971. PMID 19104660.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ Thompson, John (2005). The geographic mosaic of coevolution. The University of Chicago Press. ISBN 9780226797625.
- ^ Leimu, Roosa (December 23, 2008). "A meta-analysis of local adaptation in plants". PLoS ONE. 3 (12): e4010. doi:10.1371/journal.pone.0004010. PMC 2602971. PMID 19104660.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ Elizabeth, Leger (2009). "Genetic variation and local adaptation at a cheatgrass (Bromus tectorum) invasion edge in western Nevada". Molecular Ecology. 18 (21): 4366–4379. doi:10.1111/j.1365-294x.2009.04357.x. PMID 19769691.
- ^ Joshi, J (2001). "Local adaptation enhances performance of common plant species". Ecology Letters. 4 (6): 536–544. doi:10.1046/j.1461-0248.2001.00262.x.
- ^ Kaltz, O; Shykoff, JA (1998). "Local adaptation in host-parasite systems". Heredity. 81 (4): 361–370. doi:10.1046/j.1365-2540.1998.00435.x.