Plasticity and genetics
One of several threads -
http://forums.pondboss.com/ubbthreads.ph...true#Post130058 By Dave Willis - “I do realize that we are getting pretty darn in-depth. However, those who are interested, take a look at this!
Foraging performance of diet-induced morphotypes in pumpkinseed sunfish (Lepomis gibbosus) favours resource polymorphism.
Research Paper
Journal of Evolutionary Biology. 20(2):673-684, March 2007.
PARSONS, K. J.; ROBINSON, B. W.
Abstract:
Morphological plasticity can influence adaptive divergence when it affects fitness components such as foraging performance. We induced morphological variation in pumpkinseed sunfish (Lepomis gibbosus) ecomorphs and tested for effects on foraging performance. Young-of-year pumpkinseed sunfish from littoral and pelagic lake habitats were reared each on a 'specialist diet' representing their native habitat-specific prey, or a 'generalist diet' reflecting a combination of native and non-native prey. Specialist and generalist diets, respectively, induced divergent and intermediate body forms. Specialists had the highest capture success on their native prey whereas generalist forms were inferior. Specialists faced trade-offs across prey types. However, pelagic specialists also had the highest intake rate on both prey types suggesting that foraging trade-offs are relaxed when prey are abundant. This increases the likelihood of a resource polymorphism because the specialized pelagic form can be favoured by directional selection when prey are abundant and by diversifying selection when prey resources are restricted.”
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By Bill Cody – “Plasticity, variation, and adaptability of species promotes success and survial.” “The red shiner (C. lutrensis) ranges from Minnesota to the Gulf Coast in creeks and small rivers over sand, rock and gravel, in runs and pools. It spawns in rock and log crevices, at the base of plants, among algal masses and elsewhere. This plasticity in spawning sites; feeding habits; wide use as a baitfish; and tolerance of turbid to clear, fast or slow, warm to cold waters all account for its wide distribution, and threat to other native fish.”
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A look at YP from several locations shows a good bit of local variation. As you know (for others who may not) all fish species that I know of exhibit local adaptation which may be visual (how the fish looks) or it may not be visual but rather be any of a hundred other functions. Over very long periods of time in seperate populations the local adaptation can become genetic . It is call Phenotypic plasticity which is the ability of an organism to change its phenotype in response to changes in the environment. Such plasticity in some cases expresses as several highly morphologically distinct results; in other cases, a continuous norm of reaction describes the functional interrelationship of a range of environments to a range of phenotypes (see Wiki ). Common examples are seen in Fla LMB and CNBG vs regular BG and LMB. In some instances new species are formed. In many other instances they go into the ash bend of extinction.
From Wiki - Adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation. Adaptations contribute to the fitness and survival of individuals. Organisms face a succession of environmental challenges as they grow and develop and are equipped with an adaptive plasticity as the phenotype of traits develop in response to the imposed conditions
Local adaptation and plasticity can and often do effect what a fish looks like and what traits are outstanding.
Phenotypic plasticity is the ability of an organism to change its phenotype in response to changes in the environment. Fundamental to the way in which organisms cope with environmental variation, phenotypic plasticity encompasses all types of environmentally induced changes (e.g. morphological, physiological, behavioral, phenological) that may or may not be permanent throughout an individual’s lifespan. The term was originally used to describe developmental effects on morphological characters, but is now more broadly used to describe all phenotypic responses to environmental change, such as acclimation or acclimatization, as well as learning.
Evolution of phenotypic plasticity
Plasticity is usually thought to be an evolutionary adaptation to environmental variation that is reasonably predictable and occurs within the lifespan of an individual organism, as it allows individuals to ‘fit’ their phenotype to different environments. If the optimal phenotype in a given environment changes with environmental conditions, then the ability of individuals to express different traits should be advantageous and thus selected for. Hence, phenotypic plasticity can evolve if Darwinian fitness is increased by changing phenotype . However, the fitness benefits of plasticity can be limited by the energetic costs of plastic responses (e.g. synthesizing new proteins, adjusting expression ratio of isozyme variants, maintaining sensory machinery to detect changes) as well as the predictability and reliability of environmental cues (see Beneficial acclimation hypothesis).
These results show that the natural variation in
pharyngeal morphology between these populations of pumpkinseeds is primarily the result of a
plastic response to the environment, rather than a response to selection driven by the environmental
differences.
Thus, although our results provide no evidence of a genetic basis for variation in functional
morphology, the observed phenotypic plasticity represents an important mechanism
that can mould a fish’s morphology to the resource base of a lake. Ultimately, this would be
most adaptive if reduced crushing morphology resulted in the more efficient use of softbodied
prey. To date, we have no evidence for such a trade-off in pumpkinseed, although
work on its sister species, the redear sunfish, has shown that such a trade-off exists (Huckins,
1997; see also Ehlinger, 1990; Schluter, 1995; Robinson et al., 1996, for other examples
of trade-offs).
Here is a part from a prior Cutting Edge article on BG adaptation. Never underestimate the effect of local adaptation on a population.
In the Shoup et al study eight experimental 0.4-ha ponds (one acre with a mean depth of 1m) were used to evaluate the effects of habitat complexity on growth of small bluegill. Each pond was stocked with 15 kg of young-of-year bluegills (30–50 mm total length, approximately 20,000 fish per pond) to produce a realistic density for small ponds. The ponds contained varying amounts of vegetation (plants) and no predators.
The result was - by the end of the experiment, bluegill from the low vegetation treatment ponds were significantly longer – twenty (20%) percent than bluegill from the high vegetation treatment ponds.
..... addressed in more detail is phenotypic plasticity. That is
the ability of an individual or population to change due to environmental influences. Can environmental conditions during early development shape individuals’ phenotypes so they become more adaptive to the conditions they encounter? Were the long bluegill that fed in open water that way because longer fish can swim better in open water and were the shorter bluegill that way because being short allows them to maneuver around the weeds better? Plasticity has been shown to effect sunfish (Lepomis) shape, feeding and behavior in some cases.
Tramactions of the American Fisheries Society 109:108-115, 1980
¸ Copyright by the American Fisheries Society 1980
Genetic and Morphological Variation of Bluegill
Populations in Florida Lakes
JAMES D. FELLEY
Department of Zoology, University of Oklahoma
Norman, Oklahoma 73019
JOHN C. AVISE
Department of Zoology, University of Georgia
Athens, Georgia 30602
Abstract
The structure of bluegill (Lepomis macrochirus) populations in natural Florida lakes was assessed
from clcctromorphic and morphologicharacters. Elcctrophorctically assaycd allclc frequencies
arc homogeneous within lakes and heterogeneous among lakes. Populations in two adjacent
lakes connected by a short river arc nearly identical. Several considerations indicate that cvcn
young-of-the-year bluegills arc well mixed within subpopulations of these lakes, and that indi-
vidual dispersal is important in maintaining intcrsubpopulation homogcncity in allclc frequency.
This pattern of genetic differentiation contrasts with the pattern of hctcrogcncity observed in
mcristic counts for several morphological traits. At the microgeographic level, genetic homo-
gcncity probably reflects a long-term history of bluegill movements within a lake, while within-
lake morphological hcterogcncity reflects the varied conditions during individual development
to which incompletely isolated subpopulations are exposed.
The genetic homogeneity observed within
lakes is not reflected in the morphological char-
acteristics (Fig. 2). Hagen (1973) found high
heritabilities for meristics traits but noted that
heritability can only be defined for given envi-
ronmental conditions. Meristic traits are influ-
enced during embryonic development by such
environmental variables as temperature, CO2
concentration, salinity, and pH (T•ning 1952;
Barlow 1961; Fowler 1970). The variation in
locality means for these meristic traits may thus
be evidence of the environmental conditions,
varying temporally and microgeographically, to
which the developing fish were subjected. Thus
we can envision the possibility of a lake con-
sisting of/a patchwork of environmental con-
ditions influencing developmentally plastic
traits. Between-locality heterogeneity in such
morphological characters would then be regen-
erated in each generation, while the between-
locality homogeneity in genetic composition re-
flects effects of a long-term history of bluegill
movement within a lake.
On a broader perspective, all bluegills in the
Florida lakes are similar to one another, both
morphologically and genetically. Their meristic
counts and genotype frequencies are character-
istic of the Florida bluegill subspecies, and are
very distinct from bluegills from Georgia and
South Carolina to Texas (Avise and Smith
1974; Felley, in press). At the macrogeographic
level, there is a clear correspondence between
morphology and genetics. At the microgeo-
graphic level, genetic homogeneity may reflect
the long-term history of bluegill movement
within a lake, while morphological heteroge-
neity reflects the varied developmental condi-
tions to which individuals in incompletely iso-
lated subpopulations are exposed.
North American Journal of Fisheries Management 17:543-556, 1997
© Copyright by the American Fisheries Society 1997
Geographic Patterns in Genetic and Life History Variation in
Pumpkinseed Populations from Four East-Central
Ontario Watersheds
MICHAEL G. Fox
Environmental and Resource Studies Program and Department of Biology
Trent University, Peterborough, Ontario K9J 7B8, Canada
JULIE E. CLAUSSEN AND DAVID P. PHILIPP
Center for Aquatic Ecology, Illinois Natural History Survey
607 East Peabody Drive, Champaign, Illinois 61820, USA
Abstract.—We examined the geographic distribution of biochemical genetic and life history
characteristics of 16 populations of pumpkinseed Lepomis gibbosus within four east-central Ontario
watersheds to determine (1) if populations within watersheds were more alike for either of these
traits than populations among watersheds, (2) if the distribution of genetic and life history characteristics
among watersheds coincided with each other, and (3) if the distribution of genetic and
life history characteristics among watersheds showed some geographic pattern. Pumpkinseeds
collected early in the reproductive season in the years 1990-1993 were assessed for reproductive
maturity, gonadosomattc index (females only), and juvenile growth. Allele frequencies at six
polymorphic loci were determined by protein electrophoresis. Cluster analysis based upon genetic
distance coefficients showed three distinct groups, one containing populations from the Rideau
River watershed, a second containing populations from the Crowe River watershed, and a third
containing a mixture of populations from the Cataraqui River and Otonabee River watersheds.
This cluster pattern does not coincide with a geographic distance matrix among river systems
based upon current watersheds, but is consistent with suggested post-Pleistocene recolonization
routes from both the Mississippi and Atlantic refugia. Mean age and length at maturity, however,
showed an east-west pattern of variation, with the populations in the two central Ontario watersheds
maturing earlier and at a smaller size than the populations in the two eastern Ontario watersheds.
The cluster pattern of life history traits also did not coincide with a geographic distance matrix
based upon current watersheds, nor did it coincide with the cluster pattern based upon genetic
distance coefficients. The differences in genetic and life history patterns may reflect original
founder effects during initial recolonization events, the effects of drift subsequent to that time,
life history responses to east-west differences in natural or human-induced environmental factors,
or some combination of these factors. These observed patterns in the distribution of genetic
variation (i.e., the clustering of populations within watersheds) support the concept of managing
native fisheries by the stock concept.
Fish also exhibit interpopulational variation in
life history traits, some of which can be attributed
to genetic factors (McPhail 1977; Fields, et al.
1987; Gharrett et al. 1988; Snyder and Dingle
1988; Beacham el al. 1989; Philipp and Whitt
1991; Toline and Baker 1994; see also Stearns and
Koella 1986). A high degree of variation in reproductive
life history traits has been shown to
occur even among fish populations within the same
geographic region. Although some of this variation
is clearly related to environmental variability (e,g,,
Constantz 1979; Baltz and Moyle 1982; Fox and
Keast 1991), reproductive life history variation
within a geographic region also occurs among fish
populations for which major environmental differences
are not evident (Schmeidler and Brown
1990; Hutchings 1993; Fox 1994).
More
FELLEY, J. In press. Analysis of morphology and
asymmetry in bluegill sunfish (Lepomis macrochi-
rus) in the southeastern United States. Copeia.
NEY, J.J., AND L. L. SMITH, JR. 1976. Serum protein
variability in geographically defined bluegill (Le-
pomis macrochirus) populations. Transactions of
the American Fisheries Society 105:281-290.