Nrcm 211 Quiz 4

Front 1

Natural variation

Back 1

• Is universal and characteristic of all biological systems.

Front 2

Intraspecific variation

Back 2

– It is responsible, at first, for the feeling of frustration and uncertainty in species identification.
– It may lead to guessing the identification rather than careful consideration of all variable characters.
– By observing many individuals of a species, one begins to acquire and appreciation for the range in variation
to be expected in a particular species.

Front 3

Normal variation

Back 3

– Normal variation between sexually reproducing individuals comes about by mutations, genetic segregation,
and recombination.

Front 4

There are distinct patterns of variation

Back 4

• Can be recognized when considering the differences observed between individuals and populations of a given species its entire geographical and ecological range.

Front 5

Classified variation

Back 5

Variation can be classified initially as intrinsic or extrinsic

Front 6

Intrinsic

Back 6

• Originating within the individual or species

Front 7

Extrinsic

Back 7

• Originating from outside, i.e., coming from another species

Front 8

Types of variation

Back 8

Intrinsic and Extrinsic

Front 9

Intrinsic

Back 9

• Phenotypic plasticit
• Developmental plasticity
• Abnormal (mutational)
• Chromosoma
• Nonadaptive
• Ecotypic
• Clinal
• Reproductive
• Speciational

Front 10

Extrinsic

Back 10

• Hybrid
• Introgressive

Front 11

Phenotypic plasticity

Back 11

– It is the direct response of plant form to environmental factors.
– It means the capacity of organisms with the same genetic makeup (genotype) to vary in its visible
characteristics (phenotype) due to varying environmental conditions.

Front 12

Phenotypic plasticity

Back 12

– Another type of phenotypic plasticity within tree is often associated with the stress morphology created by
extreme midseason drought or defoliation due to a late spring freeze, severe insect damage, or chemical
spraying.
– Phenotypic plasticity is nongenetic in that the acquired, environmentally induced differences are not inherited.

Front 13

Developmental plasticity

Back 13

– The developmental or phase change from juvenile to mature form is called a heteroblastic change or phase
change.

Front 14

Two common examples of of developmental plasticity

Back 14

– Two common examples are the lobed leaves of sassafras and mulberry found on saplings or vigorous sprouts.
– The older trees of these two species may not have any lobed leaves.

Front 15

Seasonal heteromorphism

Back 15

occurs when the first-formed leaves on a twig of adult individuals normally differ
from the later developed leaves on the same twig.
– This may be seen among the leaves of some deciduous trees as several species of poplar, sweetgum, and oak

Front 16

Hickory

Back 16

-5 big leaves
-pinately venations
-first 3 leaves bigger than bottom 2
-opposite leaf arrangement
-shaggy bark

Front 17

Dogwood

Back 17

-Small tree bark has green color
-Older tree bark still shows some green color

Front 18

Abnormal (mutational)

Back 18

– Although mutations are the ultimate source of all genetic variation, most effects are rather minor and not
obvious.

Front 19

Some examples of obvious mutational effects in trees are genetic dwarfs in conifers

Back 19

– Pink-flowered dogwoods were derived as a mutant form of the common “white-flowered” type.
– The hairless peach (nectarine) arose as a spontaneous mutant in east Asia, although a similar mutant occurred in France in the 17 century.
– The navel orange arose as a mutant; likewise, the original grapefruit was probably a natural mutation of the
Asian shaddock.

Front 20

Chromosomal

Back 20

– The n number of chromosomes is the haploid number found, following meiosis, in the subsequent gametophyte phase of the life cycle.
– The 2n or diploid number is formed at fertilization and is the number in the cells of the sporophyte phase-tree.

Front 21

Changes in chromosome number in tree species are of two kinds:

Back 21

– Aneuploid
– Polyploid

Front 22

Hophornbean

Back 22

-Each leaf venation has a long tooth at margin with small teeth between the big teeth

Front 23

Aneuploid

Back 23

– A given haploid set is increased or decreased by the addition or deletion of one or more chromosomes

Front 24

Aneuploid examples

Back 24

– Sweetgum (n=15 or 16)
– Willo (n= 19 and 22)
– Beefwood tree (n=11, 12, and 13)
– Hackberry (n=10, 11, and 14)

Front 25

Polyploid

Back 25

– Additional full haploid sets become associated in the cells.

Front 26

Polyploidy is rare in __________ and much more common in ____________ (50 to 70%)

Back 26

gymnosperms,angiosperms

– Gymnosperms:
• redwood
– Angiosperms:
• tetraploid cucumbertree
• hexaploid southern magnolia

Front 27

Chromosomal

Back 27

– In some cases, the differences in chromosome number might be correlated with significant phenotypic
differences
– In other cases, the variation related to aneuploidy or polyploidy might be undetectable by morphological
characteristics although they may reflect chemical differences or physiological exotypes.
– In other cases, particularly if polyploidy has arisen in an interspecific hybrid,
– there are detectable morphological differences, and often the polyploid shows an adaptive superiority over the
ancestral diploids

Front 28

Nonadaptive

Back 28

– When a particular variant is not associated with some environmental condition,
• It may be a nonadaptive trait that occurs scattered throughout the species populations.
– Examples
• Southern magnolia
• White oak
- California Basswood

Front 29

Southern magnolia

Back 29

• Some trees have leaves that are green and only slightly hairy below whereas other trees have
leaves that are densely rusty-pubescent below.
• Such trees are often side by side in the same habitat
• In some case, such traits are controlled by single genes.

Front 30

White oak

Back 30

• Baranski (1975) found that much of the variation in leaf form, bark, etc., among trees of white
oak is explained by nonadaptive, more or less random, genetic variation.

Front 31

Carolina basswood

Back 31

• Different trees in a local population may be very different in leaf pubescence, some glabrous
from the beginning, some tomentose at first then becoming glabrate, and others remaining
tomentose.

Front 32

Ecotypic

Back 32

– An ecotype, or ecological race, is a distinct morphological or physiological form, or population, resulting from
selection by a distinct ecological condition.
– It is adapted genetically to factors of its local habitat.
– Ecotypes within a species are able to interbreed freely, but the offspring are naturally selected in each habitat.
– Ecotypic variation is habitat-correlated genetic variation unlike nonadapted variation, and inherited unlike ecophenic variation.
– Transplant or common garden experiment will distinguish an ecotype from an ecophene.

Front 33

Ecophene

Back 33

The range of phenotypic modifications produced by one genotype within the limits of the habitat under which the genotype is found in nature

Front 34

Ecoypes

Back 34

Would maintain its morphological form

Front 35

Ecophene

Back 35

• Would change in relation to its new environment

Front 36

_______ is most important to select the proper source of seeds for any planting to be successful.

Back 36

Ecotype

Front 37

Cline

Back 37

– Is character gradient correlated with a geographical or ecological gradient.
– Most environmental factors (temp, rainfall, and photoperiod) vary in a gradual, continuous fashion
– Thus, cone would expect a gradual, continuous variation in a wide-ranging species rather than discontinuous,
ecotypic variation.
– Each population along the gradient is more or less homogeneous and approximately adapted to the
environment at that point along the gradient.

Front 38

Cline example: White Pine

Back 38

• A decreases in needle length and number of stomata and an increase in number of resin ducts
with increasing latitude in North America

Front 39

Cline example: Red buckeye

Back 39

• Shows an east-west cline in two characters, the calyx length and pubescence of the lower leaf surface.
• The calyx becomes shorter and more bell-shaped from the Atlantic coast to Texas,
• There is a gradual increase westward North America.

Front 40

Reproductive

Back 40

– Various reproductive strategies are important determinants of variation at both the population and species level
– Most species maintain a “winning” combination of several strategies.

Front 41

There are three basic types of breeding system:

Back 41

1. Outbreeding or outcrossing
2. Inbreeding
3. Apomixis

Front 42

Outbreeding or outcrossing

Back 42

– Is xenogamy
– Is crossing between individual plants
– Leads to greater genetic variation within populations, and assuming some gene flow among populations
– Is promoted by various floral mechanisms, self-incompatibility, and the monoecious and dioecious conditions (ginko, holly, ash)

Front 43

Inbreeding

Back 43

– Is autogamy
– Is selfing within a single
– Is bisexual flower
– Is geitonogamy, crossing between flowers of one plant
– Leads to less genetic variation within a population and greater differences among populations of a species.
– Several floral mechanisms promote this

Front 44

Apomixis

Back 44

– Is a specialized mechanism that is a substitution of an asexual process for the normal sexual reproduction
– May give rise to an unusual pattern of within-population and between-population variation.

Front 45

Apomixis may occur in two basic ways:

Back 45

1. Vegetative Apomixis
2. True Apomixis

Front 46

Vegetative apomixis

Back 46

– Vegetative apomixis in which the plants reproduce by root sprouts or other means of vegetative propagation in place of sexual seed formation.
– Examples: Bigtooth aspen and quaking aspen

Front 47

Big tooth Aspen

Back 47

-Big tooth on leaf margin
-3 main leaf venations from base
-Two buttons at base of leaf

Front 48

Quaking Aspen

Back 48

-Taper at apex of leaf
-3 main leaf venations from base
-no button
-Very small teeth
-Light color bark

Front 49

True apomixis

Back 49

– Is agamospermy
– Is the asexual formation of a seed found in certain tree species
• like citrus, alder, mountainash, serviceberry, and hawthorn.

Front 50

Speciational

Back 50

– The primary mode of species formation
• Speciation
• If ecotypes, portions of a cline, or populations of autogamous plant become genetically isolated through spatial or reproductive barriers of some type, the distinct population can continue to diverge genetically.

Front 51

Speciational examples

Back 51

– The coastal and Rocky Mountain forms of Douglas-fir
• May represent incipient and incomplete speciation,
• Because the two types intergrade in certain areas
– The large fruited form of devilwood
• Found in the dry pine scrub of south peninsular, FL
• Is considered a variety of the widespread Osmanthus americanus of more mesic environmets