Transcript Morphological variability in Melampyrum (Orobanchaceae)

Morphological variability in
Melampyrum
(Orobanchaceae)
Milan Štech
Faculty of Biological Sciences
University of South Bohemia
Czech Republic
Genus Melampyrum
 almost 40 species in northern hemisphere
 large morphological variation especially at
infraspecific level
 the indistinct species limits in some groups
 “seasonal variation” – the most conspicuous
phenomenon at the intraspecific level
 important fetotypic plasticity, influence of host plant
Interspecific level
Melampyrum nemorosum
group
M. nemorosum group
 nearly one half of the genus´s species
 species delimitation is based predominantly on the
calyx indumentum, calyx teeth length, bract shape
and bract colour, corolla length and corolla shape
 but
* characters indicated for individual species do not
correspond to reality sometimes
* both infra- and interpopulation variation in these taxa
are large
* populations with intermediate characters occur often
Example M. subalpinum / M. bohemicum
 many nomenclatorical and taxonomical mistakes
 originally described as M. nemorosum var. subalpinum
by Juratzka from the northeastern border of the Alps.
 Kerner included in your species M. subalpinum
(Juratzka) Kerner plants from Romania, which he
himself described as M. bihariense later
 Beck distinguished two types of M. subalpinum
* M. subalpinum s. str. with wide leaves
* M. angustissimum with narrow leaves
 Kerner described M. bohemicum from the Czech
Republic, but his diagnostic characters distinguish
M. bohemicum from M. subalpinum s. str. and not from
M. angustissimum
Diagnostic characters according to the Flora Europaea
Character
M. subalpinum
M. bohemicum
Leaf width
(2–)14–18 mm
1,5–3 mm
Bracts
ovato-lanceolate, deeply
toothed, violet-blue
1,5–3 mm wide, green, the
lower entire, the upper hastatedentate
Calyx
subglabrous
glabrous or puberulent, but
with longer hairs on veins and
on margin
Calyx teeth
4 mm, more or less patent
4–6 mm, porrect
Corolla lenght
15 mm
18–20 mm
Study
 26 morphological characters were studied in 15 populations of
M. bohemicum, M. angustissimum, M. subalpinum s. str., and
M. nemorosum.
 Differences in indicated diagnostic characters between
M. bohemicum and M. angustissimum were not confirmed.
M. bohemicum comprises a part of larger variation of populations
of M. angustisimum.
 M. subalpinum s. str. differs from both types and resembles
M. nemorosum in some characters
Hybridization hypothesis
 intermediate position of M. subalpinum s. str. between
M. angustissimum and M. nemorosum
 large variation range in several characters among
individual populations of M. subalpinum s. str.
 distribution area of M. subalpinum s. str.
possibility of old introgressive hybridization
between M. nemorosum and M. angustissimum
120
Hybridization hypothesis
0 = without capsule
1 = regular capsule
2 = aborted capsule
100
 intermediate position of M. subalpinum s. str. between
M. angustissimum and M. nemorosum
 large variation range in several characters among
individual populations of M. subalpinum s. str.
80
60
45
Number of developed capsules
40
20
24
21
1
2
18
20
7
0
 distribution area of M. subalpinum s. str.
0
1
2
M. bohemicum × M. bohemicum
120
100
0
M. bohemicum × M. nemorosum
possibility of old introgressive hybridization
between M. nemorosum and M. angustissimum
99
80
 hybridization experiments indicate a possibility of
successful crossing between M. bohemicum and
M. nemorosum despite apparent reproductive barriers
60
40
27
18
20
13
1
0
0
0
1
2
control without treatment
0
1
2
control with removal of stamens
Melampyrum sylvaticum
group
M. sylvaticum group
M. saxosum
 problem
* three taxa at the specific level are usually distinguished
* two taxa consider to be endemic in the Eastern and Southern Carpathians
but occurrence records originate from other regions too
 study
* 17 morphological characters were studied in 25 populations of M.
sylvaticum in Central Europe
* RAPD markers were studied in 10 populations as a support of
morphological study
M. sylvaticum
M. herbichii
Results
 M. herbichii seems not to be restricted in the Eastern and
Southern Carpathians
 Populations of M. sylvaticum agg. from the Western
Carpathians and Sudeten Mts. seem to be closer to M.
herbichii based on the RAPD markers, but they are
polymorphic and often similar to the M. sylvaticum s. str.
from the morphological point of view
 But problem is more comlex and needs further study
Discriminant Analysis – Canonical scores of individual
plants on the discriminant axis.
Infraspecific level
Seasonal variation
 traditionally evaluated as the most important taxonomic
character at this level
 different populations of one species flower in different
periods of the year
 in addition to the flowering period so-called “seasonal
characters ” vary in different populations of one species
Example M. pratense
 probably the most variable species of genus
 many infraspecific taxa were described based on
seasonal characters mainly
 study
* 11 morphological characters were studied in 90 populations in
Central Europe
* changes in seasonal characters over the flowering period in
particular populations and influence of enviromental factors
were studied too
Results
 variation of “seasonal characters” is often limited by
enviromental factors, which determined vegetation period length
 Studied population form a very homogeneous reticulate pattern.
Delimitation of intraspecific taxa based on the seasonal
characters is impossible and would be artificial.
 Populations of Melampyrum pratense break up into diverse
“regional types” over all the distribution area. These types are
characterised by a specific combination of seasonal characters,
but also by other characters (the most conspicuous one is the
flower colour).
 Taxonomic description of these “regional types” is not much
important, but processes generating this variation are worth of
Positions
further
study. of individual plants in the ordination space of PCA of
population samples. Two population examples are marked.
Example M. nemorosum
240
early populations
Number of plants
 11220“seasonal
” were studied in 44 populations
latecharacters
populations
200
 changes in seasonal characters over the flowering period in
180
particular
populations and influence of enviromental factors were
160
studied
too
140
 Results
120
*100 significant contrast were found in the seasonal variation
pattern by comparison to M. pratense
80
* two seasonal taxa can be distinguished based studied
60
morphological characters – early, late
40
* difference in habitat recquirements
20
 Polytopic
origin of early type is supposed
0
-5
-4
-3
-2
-1
0
1
2
3
Canonical discriminant analysis of plants of Melampyrum nemorosum. Frequency
distribution of specimens along the canonical variable
4
Chance for further study
 study of the hybrifization hypothesis by molecular
methods
 revision of other confused taxa from the Melampyrum
nemorosum group
 origin of seasonal types by individual species
 study of important “nonseasonal characters” at the
infraspecific level (e. g. bract shape by M. pratense)
 phylogeographical study of selected species
 genus phylogeny
…