Lesson 3: Species in the environmental complex
Lesson 3: Species in the environmental complex
Lesson 3: Species in the environmental complex
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<strong>Lesson</strong> 3: <strong>Species</strong> <strong>in</strong> <strong>the</strong> <strong>environmental</strong><br />
<strong>complex</strong><br />
• Environmental factors and plant<br />
distribution<br />
– Liebig s law of <strong>the</strong> m<strong>in</strong>imum<br />
– Shelford s law of tolerance<br />
– Bill<strong>in</strong>gs Holocoenotic concept<br />
• Ecotypic variation with<strong>in</strong> species:<br />
– Morphological variation<br />
– Ecophysiological variation<br />
– Genetic variation
Why are organisms absent some<br />
places and abundant <strong>in</strong> o<strong>the</strong>rs?
Why are organisms absent some places and<br />
abundant <strong>in</strong> o<strong>the</strong>rs?<br />
• Abiotic Forces: plants have certa<strong>in</strong> limits regard<strong>in</strong>g <strong>environmental</strong><br />
tolerances.<br />
–Temperature, moisture, sunlight, pH, substratum, sal<strong>in</strong>ity, atmosphere, etc<br />
• Biotic Forces: Organisms compete for space and resources, and some eat<br />
o<strong>the</strong>rs.<br />
–Competition, predation, symbiosis, nest sites, habitat modification.<br />
• Opportunity (history): organisms are absent where <strong>the</strong>re is no geographical<br />
access.<br />
–Sometimes when <strong>the</strong>y are <strong>in</strong>troduced <strong>in</strong>to areas where <strong>the</strong>y were previously<br />
absent, havoc ensues.<br />
–<strong>in</strong>troduced (exotic) species are <strong>the</strong> second most important cause of ext<strong>in</strong>ction.<br />
Habit destruction is <strong>the</strong> first.<br />
–Examples: kudzu, fire ants, killer bees, zebra mussels, Asiatic clams, Japanese<br />
honeysuckle, water hyac<strong>in</strong>th, Hydrilla, Egeria, Japanese beetles, honeybee mites,<br />
giant slugs, Brazilian pepper, tamarisk, thistles, Australian p<strong>in</strong>e, privet.
Justis Liebig (1803-1873)<br />
Liebig’s Lab <strong>in</strong> Giessen, 1840
Liebig s Law of <strong>the</strong> M<strong>in</strong>imum<br />
• Liebig recognized that plant growth is controlled by plant<br />
nutrients, and whichever nutrient is <strong>in</strong> most limited supply<br />
controls <strong>the</strong> plant s growth.<br />
• This concept was later expanded to cover o<strong>the</strong>r <strong>environmental</strong><br />
factors such as water, light, temperature.<br />
• He noted that plants had vary<strong>in</strong>g ranges of tolerance for a given<br />
factor.<br />
• “The growth or distribution of a plant is<br />
dependent on <strong>the</strong> one <strong>environmental</strong> factor most<br />
critically <strong>in</strong> demand.”
Shelford s Law of Tolerance<br />
• Shelford <strong>in</strong> 1913 noted a weakness <strong>in</strong> Liebig s general law<br />
which came to be known as <strong>the</strong> Law of Tolerance. And this<br />
<strong>in</strong> turn was modified by Ronald Good, a plant geographer:<br />
• “Each and every plant species is able to exist and<br />
reproduce successfully only with<strong>in</strong> a def<strong>in</strong>ite range of<br />
<strong>environmental</strong> conditions.<br />
• Good rated climatic factors above edaphic factors.<br />
• Some Examples:<br />
– Sal<strong>in</strong>ity tolerance <strong>in</strong> plants (<strong>in</strong>tertidal zonation)<br />
– Thermal constra<strong>in</strong>ts on activity (sparrow microclimates,<br />
shown <strong>in</strong> <strong>the</strong> diagram from Smith s Ecology and Field<br />
Ecology.)
Shelford s<br />
Law of<br />
Tolerance<br />
• The distribution of<br />
a species along an<br />
<strong>environmental</strong><br />
gradient generally<br />
approximates a<br />
Gausian<br />
distribution, with<br />
<strong>the</strong> optimal<br />
occurrence<br />
somewhere near<br />
<strong>the</strong> midpo<strong>in</strong>t of <strong>the</strong><br />
distribution.<br />
From Smith’s Ecology and Field Ecology.
Steno- and Eury-<br />
• These prefixes describe <strong>the</strong> width of <strong>the</strong> ecological niche <strong>in</strong><br />
relation to a given <strong>environmental</strong> factor.<br />
• For example, A plant with a narrow range of tolerance for<br />
temperature is termed steno<strong>the</strong>rmic. Plants with a wide<br />
<strong>the</strong>rmal tolerance are termed eury<strong>the</strong>rmic.
-phile and -phobe<br />
• These suffixes are used to describe plants that favor one<br />
extreme of an <strong>environmental</strong> gradient.<br />
• For example, a plant favor<strong>in</strong>g snowy habitats is called a<br />
chionophile, and a plant that grows only <strong>in</strong> w<strong>in</strong>dblown,<br />
snowfree habitats would be called a chionophobe.
Plants operate with<strong>in</strong> <strong>the</strong> tolerance limits for all <strong>the</strong><br />
critical factors for <strong>the</strong>ir growth<br />
• Add Fig. 3-1 (BBPGS)<br />
• No s<strong>in</strong>gle factor<br />
controls <strong>the</strong><br />
distribution of a<br />
plant.<br />
• Good thought that<br />
climate factors were<br />
most important<br />
controls, edaphic<br />
(soil) factors were<br />
next most important,<br />
and biotic factors,<br />
such as competition,<br />
were least important.
Biotic Controls: Competitive exclusion <strong>in</strong> animals:<br />
Gause s experiment us<strong>in</strong>g protozoans (Paramecium)<br />
• .Competition with o<strong>the</strong>r species can strongly <strong>in</strong>fluence how<br />
a species will respond to an <strong>environmental</strong> factor.<br />
• The concept of what def<strong>in</strong>es a species niche is one of <strong>the</strong><br />
most hotly disputed topics <strong>in</strong> ecology. This famous<br />
experiment by <strong>the</strong> Russian biologist G.F. Gause (1934) first<br />
demonstrated <strong>the</strong> pr<strong>in</strong>cipal of “one species, one niche”. He<br />
did <strong>the</strong> experiment us<strong>in</strong>g small animals.
Biotic Controls: Competitive exclusion <strong>in</strong> animals:<br />
Gause s experiment us<strong>in</strong>g protozoans<br />
(Paramecium)<br />
P. aurelia<br />
P. caudata<br />
Grown separately<br />
Grown toge<strong>the</strong>r<br />
• In separate but identical<br />
bacterial cultures. Each<br />
species showed a similar<br />
growth rate <strong>in</strong> <strong>the</strong><br />
absence of competition.<br />
• When placed toge<strong>the</strong>r, P.<br />
aurelia was able to<br />
compete successfully for<br />
<strong>the</strong> bacterial food, and<br />
eventually elim<strong>in</strong>ated P.<br />
caudata.<br />
• In ano<strong>the</strong>r experiment P.<br />
caudata was grown with<br />
P. bursaria. Both species<br />
fed on <strong>the</strong> bacteria, but<br />
<strong>in</strong> this case, P. bursaria<br />
fed on <strong>the</strong> bacteria at <strong>the</strong><br />
bottom of <strong>the</strong> tub, while<br />
P. caudata fed on <strong>the</strong><br />
bacteria <strong>in</strong> suspension--<br />
Coeexistance because of<br />
different niches.<br />
Based on Gause 1934
Competitive exclustion <strong>in</strong> plants: Harper s<br />
experiment us<strong>in</strong>g duckweed (Lemma)<br />
Adapted from Harper 1961
Effects of competition:<br />
shift of ecological optimum<br />
Solid l<strong>in</strong>e: Spergula arvensis (Spurry)<br />
Dashed l<strong>in</strong>e: Raphanus raphanistrum (a wild mustrard)<br />
• Ellenberg showed that <strong>the</strong> growth of two<br />
species of mustard have very similar<br />
response to pH when grown separately.<br />
• When grown toge<strong>the</strong>r <strong>in</strong> mixed culture,<br />
<strong>the</strong>y both shift <strong>the</strong>ir optimum pH a bit.<br />
Spergula favors a lower pH, and<br />
Raphanus favors a higher pH.<br />
• In most cases it is unlikely that <strong>the</strong>y will<br />
have exactly <strong>the</strong> same niche, where one<br />
totally excludes <strong>the</strong> o<strong>the</strong>r.<br />
From Ellenberg 1958
The ecological (or realized) niche for a species may shift or be truncated <strong>in</strong> <strong>the</strong><br />
presence of competition.<br />
• Add Fig. 3-3 (BBPGS)
Ano<strong>the</strong>r view of fundamental vs. realized niches<br />
From Smith 1977<br />
• The presence of o<strong>the</strong>r species <strong>in</strong> portions of <strong>the</strong> range of characteristics, can elim<strong>in</strong>ate<br />
<strong>Species</strong> A from parts of its fundamental niche, so that its realized niche is smaller.
Dwight Bill<strong>in</strong>gs<br />
• Dwight Bill<strong>in</strong>gs helped to<br />
crystallize <strong>the</strong> study of <strong>the</strong><br />
relationship of plants to <strong>the</strong><br />
environment. He was one of<br />
<strong>the</strong> major proponents of<br />
us<strong>in</strong>g an ecophysiological<br />
approach.<br />
• He believed that <strong>the</strong> best way<br />
to study <strong>the</strong>se relationshps<br />
was through detailed<br />
autecological studies of plant<br />
species and how <strong>the</strong>y react to<br />
changes <strong>in</strong> <strong>the</strong>ir environment.
Why do plants grow where <strong>the</strong>y do?<br />
The holocoenotic<br />
<strong>environmental</strong><br />
<strong>complex</strong><br />
• A <strong>complex</strong>, <strong>in</strong>dvisible<br />
whole system<br />
consist<strong>in</strong>g of <strong>the</strong> plant<br />
and its multitude of<br />
<strong>environmental</strong><br />
<strong>in</strong>fluences.<br />
• Holocoenosis =<br />
ecosystem?<br />
• Compare to Tansley s<br />
concept of <strong>the</strong><br />
“ecosystem”, which<br />
also <strong>in</strong>cluded time and<br />
change.<br />
• Bill<strong>in</strong>g s concept is<br />
<strong>the</strong>refore an<br />
ecosystem at a<br />
moment <strong>in</strong> time.<br />
W.D. Bill<strong>in</strong>gs, 1952. The <strong>environmental</strong> <strong>complex</strong> <strong>in</strong> relation to plant growth and<br />
distribution. Quaterly Review of Biology 27: 251-265.
Bill<strong>in</strong>gs: Groups of factors <strong>in</strong> a terrestrial plant environment:<br />
– Climate<br />
– Edaphic<br />
– Geographic<br />
– Topographic<br />
– Pyric<br />
– Biotic<br />
Groups were subdivided <strong>in</strong>to: factors subfactors and aspects.<br />
Examples:<br />
Climate was divided <strong>in</strong>to <strong>the</strong> factors Radiation, Temperature, Water, Atmospheric gases.<br />
Edaphic was divided <strong>in</strong>to Parent material, Soil;<br />
Geographic was divided <strong>in</strong>to Gravity, Rotational Effects, Geographic Position,<br />
Vulcanism, Ditrophism (fold<strong>in</strong>g, fault<strong>in</strong>g), Erosion and Deposition, Topography, etc.<br />
The factor Radiation was divided <strong>in</strong>to <strong>the</strong> subfactors: Solar radiation, cosmic radiation, and<br />
terrestrial radiation.<br />
The subfactor Solar radiation was subdivided <strong>in</strong> <strong>the</strong> aspects, wavelenths, <strong>in</strong>tensity,<br />
photoperiod and o<strong>the</strong>r cycles.<br />
Bill<strong>in</strong>gs identified a total of 64 <strong>environmental</strong> aspects, but this was by no means a<br />
comprehensive list. It only served to illustrate how <strong>complex</strong> <strong>the</strong> plant environment is and<br />
how <strong>the</strong> aspects <strong>in</strong>teract among <strong>the</strong>mselves and <strong>the</strong> plant.
Some conclusions from Bill<strong>in</strong>gs paper: Factors of a terrestrial plant<br />
environment:<br />
• Environment of a plant is holocoenotic (forms a complete system <strong>in</strong><br />
comb<strong>in</strong>ation with <strong>the</strong> plant).<br />
• For a given species, limit<strong>in</strong>g factors can be different <strong>in</strong> different parts of<br />
its range.<br />
• The total environment is dynamic and varies both space and time.<br />
• Vegetation can be used as an <strong>in</strong>dicator of <strong>the</strong> total environment if <strong>the</strong><br />
tolerances of its characteristic species are known.
What is a species?:<br />
The biological species concept<br />
• A group of natural populations that are morphologically, genetically, and<br />
ecologically similar.<br />
– This def<strong>in</strong>ition <strong>in</strong>volves<br />
• Appearance (morphology)<br />
• Breed<strong>in</strong>g behavior (genetics)<br />
• Habitat dist<strong>in</strong>ctiveness (ecology)<br />
• They may or may not be <strong>in</strong>terbreed<strong>in</strong>g, but <strong>the</strong>y are reproductively isolated<br />
from o<strong>the</strong>r species.
The biological species concept<br />
• Classical taxonomists have focused most on morphology. This<br />
approach has been until recently <strong>the</strong> only tool to determ<strong>in</strong>e <strong>the</strong><br />
relationship of one species to o<strong>the</strong>rs.<br />
• Newer approaches to <strong>the</strong> species focus on <strong>the</strong> genetic aspects --<br />
how population of plants ma<strong>in</strong>ta<strong>in</strong> <strong>the</strong>ir dist<strong>in</strong>ctiveness through<br />
genetic isolation.<br />
• These isolat<strong>in</strong>g barriers may be due to:<br />
– breed<strong>in</strong>g behavior (time of flower<strong>in</strong>g, type of poll<strong>in</strong>ator),<br />
– habitat, or geographic isolation, or<br />
– <strong>in</strong>ability to form fertile hybrids.
Ecotype Concept<br />
• Many botanists have noted that with<strong>in</strong> a given species <strong>the</strong>re is often<br />
considerable morphological, physiological, or phenological variation.<br />
• Kerner <strong>in</strong> Switzerland noted such variation but thought that <strong>the</strong> various<br />
traits were plastic responses to <strong>environmental</strong> factors.<br />
• In <strong>the</strong> 1920s Göte Turesson confirmed that many of <strong>the</strong> traits were<br />
heritable. He collected samples of populations of many plant species from<br />
all over Europe and grew <strong>the</strong>m <strong>in</strong> a common garden <strong>in</strong> Sweden. He noted<br />
considerable variation <strong>in</strong> a variety of factors with<strong>in</strong> a given species even<br />
though <strong>the</strong> various populations were fully <strong>in</strong>terbreed<strong>in</strong>g.
Göte Turreson: Ecotype Concept<br />
• Turreson grew<br />
plants of <strong>the</strong> same<br />
species from all<br />
over Europe <strong>in</strong> his<br />
transplant garden<br />
<strong>in</strong> Åjarp, Sweden.<br />
Table 3-2. From Barbour et al. 1999.<br />
• He noted with<strong>in</strong><br />
one species of<br />
hawkweed<br />
collected from<br />
woodlands, fields,<br />
and dunes, <strong>the</strong>re<br />
was consistent<br />
variation <strong>in</strong> leaf<br />
morphology,<br />
pubescence, and<br />
autumn dormancy.
Turreson s observations of Betula<br />
.<br />
ALPINE TUNDRA<br />
MID-ELEVATION<br />
FOREST<br />
COASTAL BLUFFS<br />
LOW TEMP (SPRING)<br />
MOD TEMP (SUMMER)<br />
MOD. TEMP (SUMMER)<br />
PROSTRATE<br />
TREE<br />
SHRUB<br />
TINY LEAVES<br />
LARGE LEAVES<br />
FLESHY LEAVES<br />
• THESE DIFFERENCES PERSISTED IN THE COMMON ENVIRONMENT GARDEN LEADING<br />
GOTE TURESSON TO LABEL EACH POPULATION AN ECOTYPE OF ITS SPECIES
Key aspects of ecotypes accord<strong>in</strong>g to Turreson s concept<br />
• Wide-rang<strong>in</strong>g species are differentiated <strong>in</strong>to different hereditary groups<br />
that are genetically based (ecotypes). They are discrete entities with clear<br />
differences separat<strong>in</strong>g <strong>the</strong>m from o<strong>the</strong>r ecotypes.<br />
• The genetic differences are adaptations to <strong>the</strong> different habitats.<br />
• Ecotypes occur <strong>in</strong> dist<strong>in</strong>ctive habitats. In a given habitat populations of<br />
different species often exhibit similar morphological and developmental<br />
characteristics. Dist<strong>in</strong>ctiveness can be morphological, physiological,<br />
and/or phenological. (e.g. (1) life form, (2) tim<strong>in</strong>g of growth, (3) tolerance of<br />
frost, (4) tolerance of salt, and (5) tolerance of shade.)<br />
• They are potentially <strong>in</strong>terfertile with o<strong>the</strong>r ecotypes of <strong>the</strong> same species.
Clausen, Keck, and Heisey (1940)<br />
Fig. 3.5. Barbour et al. 1999.<br />
• Ecotypes along an elevation transect <strong>in</strong><br />
California.<br />
• Initially, <strong>the</strong>y had many transplant gardens<br />
located along this transect and were<br />
transplant<strong>in</strong>g about 180 species from<br />
different areas <strong>in</strong>to as many gardens as<br />
possible.<br />
• Reduced <strong>the</strong> number of gardens to <strong>the</strong> three<br />
at Stanford, Ma<strong>the</strong>r, and a Timberlilne site,<br />
and 60 species.<br />
• Transplanted local species from each site<br />
<strong>in</strong>to <strong>the</strong> o<strong>the</strong>r gardens.
Table 3.3. Barbour et al. 1999.<br />
Summary of <strong>environmental</strong> conditions at <strong>the</strong> transplant<br />
gardens
Three ecotypes (subspecies) of Potentilla glandulosa and <strong>the</strong>ir appearance <strong>in</strong><br />
each of <strong>the</strong> transplant gardens<br />
Ecotype<br />
Nevadensis<br />
• Photos along <strong>the</strong> diagonal<br />
show <strong>the</strong> species as it<br />
grows at its native site.<br />
• All of <strong>the</strong> populations were<br />
shown to be <strong>in</strong>terfertile.<br />
reflexa<br />
• They concluded, as<br />
Turesson did, that species<br />
are really composed of<br />
genetically dist<strong>in</strong>ct groups<br />
of ecotypes which are best<br />
suited <strong>the</strong>ir specific<br />
environment.<br />
typica<br />
Fig. 3-6 from Barbour et al.
Mooney and Bill<strong>in</strong>gs (1959): Ecophysiological variation <strong>in</strong><br />
ecotypes of Oxyria digyna (Mounta<strong>in</strong> sorrel)<br />
• Took <strong>the</strong> concept<br />
one step fur<strong>the</strong>r<br />
with detailed<br />
exam<strong>in</strong>ation of <strong>the</strong><br />
physiological<br />
responses of<br />
different<br />
population.
Morphological, biochemical, and phenological differences between <strong>the</strong> arctic<br />
and alp<strong>in</strong>e populations of O. digyna<br />
• Insert Table 3-6 from BBPGS
Physiological response of O. digyna ecotypes: Photosyn<strong>the</strong>tic response<br />
Temperature varies<br />
• CO 2 uptake of two ecotypes at different<br />
temperature and light conditions.<br />
• The alp<strong>in</strong>e plants had higher<br />
photosyn<strong>the</strong>tic response to both<br />
temperature and light, reflect<strong>in</strong>g <strong>the</strong><br />
generally warmer and sunnier conditions<br />
<strong>in</strong> <strong>the</strong> alp<strong>in</strong>e environment.<br />
• The optimum po<strong>in</strong>t was also higher <strong>in</strong><br />
each case for <strong>the</strong> alp<strong>in</strong>e plants (i.e.,<br />
higher light <strong>in</strong>tensity and higher<br />
temperature.<br />
Light <strong>in</strong>tensity varies<br />
• Ecophysiological differences have now<br />
been documented at much more local<br />
scales, between geographically close<br />
populations, consistent with idea of<br />
ecocl<strong>in</strong>es.<br />
Fig. 3-8, Barbour et al. 1999
Ecocl<strong>in</strong>e concept<br />
• Langlet (1959) exam<strong>in</strong>ed <strong>the</strong> growth of P<strong>in</strong>us sylvestris at<br />
580(!) sites <strong>in</strong> Sweden and concluded that species really<br />
formed a cl<strong>in</strong>e, or cont<strong>in</strong>uum of variation.<br />
• Qu<strong>in</strong>n (1987) showed that every population of Danthonia<br />
caespitosa had dist<strong>in</strong>ctive growth characteristics<br />
(phenology, morphology, physiology). He concluded that<br />
each population was <strong>in</strong> some sense <strong>in</strong>dividualistic.
McNaughton (1966): enzymatic connection <strong>in</strong> Typha<br />
latifolia<br />
http://plants.usda.gov/<br />
• Ano<strong>the</strong>r step closer to <strong>the</strong><br />
demonstrat<strong>in</strong>g actual genetic<br />
control for ecotypic variation<br />
of physiological differences.<br />
• Po<strong>in</strong>t Reyes: foggy coastal<br />
site.<br />
• Red Bluff: hot Sacramento<br />
Valley.<br />
• Collected dormant rhizomes<br />
from each site and placed <strong>in</strong><br />
common greenhouse.<br />
• Made plant extracts and<br />
collected 3 enzymes.<br />
• Subjected to <strong>the</strong> enzymes to<br />
heat stress of 50 ˚C for up to<br />
30 m<strong>in</strong>.<br />
• One of <strong>the</strong> critical enzymes<br />
(malate deydrogenase) from<br />
Red Bluff showed much<br />
higher activity with higher<br />
temperature.<br />
Fig. 3-9 , Barbour et al. 1999
O<strong>the</strong>r studies <strong>the</strong> helped demonstrate differences <strong>in</strong> ecotypes at <strong>the</strong><br />
genetic level<br />
• Smith and Pham (1996) us<strong>in</strong>g molecular biology showed high genetic<br />
variation <strong>in</strong> separate populations of wild onion.<br />
• McCauley et al. (1996) exam<strong>in</strong>ed spatial patterns of chloroplast DNA <strong>in</strong><br />
Silene alba, and found <strong>the</strong> most similar genotypes were those <strong>in</strong> close<br />
proximity to each o<strong>the</strong>r.<br />
• Rejmanek (1996) found major differences <strong>in</strong> <strong>the</strong> amount of nuclear DNA <strong>in</strong><br />
different p<strong>in</strong>e species. Aggressive <strong>in</strong>vaders of p<strong>in</strong>es had small amounts of<br />
nuclear DNA, which correlated with a shorter time for cell division, more<br />
rapid growth.<br />
• Techniques of molecular biology have now been used to identify<br />
differences <strong>in</strong> specific genes.
Rapid evolution of heavy metal tolerance <strong>in</strong><br />
bent grass (Danthonia tenuis). Anthony<br />
Bradshaw and students (1996):<br />
http://www.plann<strong>in</strong>g.sa.gov.au/<br />
• Studied m<strong>in</strong>es <strong>in</strong> Wales abandoned about 100 yr<br />
ago, and contam<strong>in</strong>ated with high levels of Cu,<br />
Fe, Zn, and Pb. Heavy metals cause prote<strong>in</strong>s to<br />
precipitate lead<strong>in</strong>g to death.<br />
• Bent grass was one of <strong>the</strong> few species grow<strong>in</strong>g<br />
on m<strong>in</strong>es and away from m<strong>in</strong>es.<br />
• Bradshaw grew plants <strong>in</strong> concentrations of 20<br />
and 2000 ppm of heavy metals. Plants on <strong>the</strong><br />
m<strong>in</strong>e sites grew <strong>in</strong> both solutions, but plants on<br />
o<strong>the</strong>r sites grew only <strong>in</strong> 20 ppm solution.<br />
See: 1. Bradshaw, A.D. and McNeilly, T.<br />
1996. Evolution and pollution. London:<br />
Edward Arnold.<br />
2. Salt, D.E. et al. 1995. Bio/Technology<br />
13: 468-474.<br />
3. Adler, T. Science News. 1996. 150:42-<br />
43.<br />
• Tolerance is present <strong>in</strong> 0.3% of natural<br />
population but is strongly selected for on <strong>the</strong><br />
m<strong>in</strong>e sites.<br />
• Plants with <strong>the</strong> tolerance make specific prote<strong>in</strong>s<br />
to b<strong>in</strong>d <strong>the</strong> heavy metals, and this takes energy<br />
away from growth of leaves and roots, mak<strong>in</strong>g<br />
<strong>the</strong>se plants less competitive <strong>in</strong> natural<br />
populations.
McGraw and Antonovics study of Dryas octopetala<br />
• Exam<strong>in</strong>ed <strong>the</strong> causes of ecotypic variation <strong>in</strong> ssp. octopetala and<br />
ssp. alaskana<br />
• An <strong>in</strong>tegrated approach to study plant populations us<strong>in</strong>g:<br />
– Growth chamber studies<br />
– Field transplants<br />
– Competition trials<br />
– Poll<strong>in</strong>ation ecology<br />
– Photosyn<strong>the</strong>sis measurements<br />
– Determ<strong>in</strong>ation of photosynthate allocation patterns <strong>in</strong> plant organs<br />
McGraw, J.B. 1985b. Experimental ecology of Dryas octopetala ecotypes. III.<br />
Environmental factors and plant growth. Arctic and Alp<strong>in</strong>e Research, 17: 229-<br />
239.
Summary<br />
• Environmental factors and plant distribution<br />
– Liebig s (1840) law of <strong>the</strong> m<strong>in</strong>imum<br />
– Shelford s (1913) law of tolerance<br />
– Holocoenotic concept of <strong>the</strong> <strong>the</strong> plant environment (Bill<strong>in</strong>gs 1952)<br />
• Ecotypic variation with<strong>in</strong> species:<br />
– Morphological variation (Turesson 1920s, Clausen, Keck and Heisey 1940,<br />
Langlet 1959, Qu<strong>in</strong>n 1987)<br />
– Ecophysiological variation (Mooney and Bill<strong>in</strong>gs 1961, McNaughton 1967;<br />
Björkman 1968)<br />
– Genetic l<strong>in</strong>kage identified (e.g., Rejmanek 1995)<br />
– Rapid selection for genes and adaptation to highly toxic environments<br />
(Bradshaw and students)
Literature for <strong>Lesson</strong> 3<br />
• Bill<strong>in</strong>gs, W.D. 1952. The <strong>environmental</strong> <strong>complex</strong> <strong>in</strong> relation to plant growth and<br />
distribution. Quarterly Review of Biology 27: 251-265.<br />
• Björkman, O. 1968. Carboxydismutase activity <strong>in</strong> shade-adapted species of higher<br />
plants. Physiologia Plantarum 21:1-10.<br />
• *McGraw, J.B. and J. Antonovics. 1983. Experimental ecology of Dryas octopetala<br />
ecotypes. Ecotypic differentiation and life-cyle stages of selection. J. Ecol.: 879-897.<br />
• *McGraw, J.B. 1985b. Experimental ecology of Dryas octopetala ecotypes. III.<br />
Enviornmental factors and plant growth. Arctic and Alp<strong>in</strong>e Research, 17: 229-239.<br />
• McNaughton, S. J. 1966. Thermal <strong>in</strong>activation properties of enzymes from Typha<br />
latifolia L. ecotypes. Plant Physiology 41: 1736-1738.<br />
• *Mooney, H.A. and W.D. Bill<strong>in</strong>gs. 1961. Comparative physiological ecology of arctic<br />
and alp<strong>in</strong>e populations of Oxyria digyna. Ecological Monographs 31: 1-29.<br />
• Rejmanek, M. 1996. A <strong>the</strong>ory of seed plant <strong>in</strong>vasiveness: <strong>the</strong> first sketch. Biological<br />
Conservation 78: 171-181.