ISSN: 2226-7522(Print) and 2305-3327
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S
Technology and Arts Research
esearch Journal
Science,
July-Sep 2013,, 2(3): 93-104
www.starjournal.org
Copyright@2013 STAR Journal. All Rights Reserved
Original Research
Perspective
Ecological Phytogeography: A Case Study of Commiphora Species
Teshome Soromessa
Center for Environmental Science, Addis Ababa University, P
Post Box No: 1176, Addis Ababa Ethiopia
Abstract
The present paper stipulated phytogeography, ecological ranges, possible origin and
migratory route of Commiphora Jacq. species. Data were gathered from the field,
herbarium and secondary sources. Information on distribution, altitude and soil
preferences were compiled and aggregated together. Phytogeographical aspect of
the group has been analyzed using Brooks’s par
parsimony analysis (1990) which was
done by tabulating flora regions versus the species under consideration where the
matrix has been filled as either presence or absence. The result of data on
phytogeography showed three patterns of distribution. Based on tthe plate tectonic
theory, evolution and diversification of most angiosperm families into consideration,
the origin of Commiphora has been discussed in details. It was recommended that
the migratory route of Commiphora still requires further investigation a
and needs to
be corroborated with data on the age of the genus and that of the concept of plate
tectonic theory.
Article Information
Article History:
Received : 28-07-2013
Revised : 21-09-2013
Accepted : 24-09-2013
Keywords:
Commiphora
Ecological Ranges
Phytogeography
*Corresponding Author:
Teshome Soromessa
E-mail:
teshome.soromessa@aau.edu.et
INTRODUCTION
The genus Commiphora Jacq. is one of the most
diverse genera of the family Burseraceae. It is
largely represented in Africa where it is confined to
arid and semi-arid areas. Commiphora also occurs
in Iran, Pakistan, Peninsula India, Sri Lanka and
Brazil. The genus is co-dominant
dominant with Acacia over
the huge areas of the Horn of Africa and supports
the large livestock populations of pastoral and agro
pastoral communities. Of the 190 or so species in
the genus, more than half of the species are native
to the Horn of Africa. This might support the notion
that the center of genetic diversity of the genus is in
this part of the world.
In earlier days attempts have been made to
circumscribe the genus, among others, Berg (1862),
931 and 1931),
Engler (1898, 1904, 1910, 1912, 1931
Sprague (1927), Chiovenda (1932), Burtt (1935),
Leenhouts (1956), Wild (1959 and 1963), Van der
Walt (1973 and 1986), Gillett (1980 and 1991) and
Boulos (2000) are the ones to be mentioned.
However, information on the phytogeography, niche
ranges, possible origin and migratory route of the
group has not been treated in the past. Thus, the
present paper aimed at dealing with the
aforementioned information taking
Commiphora in to consideration.
the
genus
MATERIAL AND METHODS
Studies on NE and
nd E Tropical African species of
Commiphora were made (Table 1 for the
nomenclature of taxa).. Data were gathered from the
intensive field works, herbarium specimens with the
consultations of various literatures. Information on
distribution, altitude and soilil preferences were
compiled and aggregated together. Phytogeo
Phytogeographcal aspect of the group has been analyzed
using Brooks’s parsimony analysis (1990). This
was done by tabulating flora regions versus the
species under consideration where the matrix has
been
een filled as either presence or absence.
The geographical areas included under the
present investigation were NE (North East which
refers to Ethiopia and Eritrea) and E (East referring
to Kenya, Tanzania and Uganda) Tropical Africa.
Because of the transgressing nature of Commiphora
species to the adjacent Somalia, Somalia was also
included in the map for discussion purposes. The
description of the regional floristic divisions of the
An Official International Journal of Wollega University, Ethiopia.
93
Teshome Soromessa
flora areas (i.e., Ethiopia, Eritrea, East Africa and
Somalia) followed Hedberg and Edwards (1989),
Polhill (1988) and Thulin (1999) as given in Figure
1.
Sci. Technol. Arts Res. J., July-Sep 2013, 2(3): 93-104
endemism. For example, C. africana has a wider
distribution through out the continent. It occurs in
Zambezian region, Sudanian region, Somalia-Masai
region, Kalahari-Highveld region, Sahel region and
the Sahara region. C. africana has been reported
from more that 30 countries in Africa (van der Walt,
1975). Others like C. schimperi, C. gileadensis, C.
quadricincta, C. habessinica, C. kataf and C. myrrha
transgress beyond the continent and occur in Arabia
having disjunct distribution. Two species, namely C.
monoica and C. suffruticosa are endemic to
Ethiopia; another two species, C. oblongifolia and C.
ovalifolia are endemic to Kenya; six species, C.
madagascarensis, C. hornbyi, C. acuminata, C.
engleri, C. spathulata and C. stolonifera are
endemic to Tanzanian flora (see Fig. 2).
Figure 1: Regional floristic divisions of Ethiopia,
Eritrea, East Africa and Somalia.
RESULTS AND DISCUSSION
Phytogeograpy
The majority of the species of Commiphora are
essentially pan tropical in their distribution extending
from Brazil via Tropical Africa to India and Pakistan
with their high concentration in the Horn of Africa.
On the account of the subdivision of African
phytochoria of White (1983), the genus is found
distributed in the majority of the regional centers of
endemism, regional mosaic and transitional zones,
with the highest genetic diversity in the SomaliaMasai regional center of endemism. Accordingly
Commiphora species are found in Zambezian
regional center of endemism, the Sudanian regional
center of endemism, the Somalia-Masai regional
center of endemism, the Karoo-Namib regional
center of endemism, the Zanzibar-Inhambane
regional mosaic, the Kalahari-highveld regional
transitional zone, the Tongaland-Pondoland regional
mosaic, the Sahel regional transition zone and the
Sahara regional transition zone. However, some
species like C. myrrha is transcontinental and
extends its distribution to Arabia and India.
Figure 2: Distribution of endemic species of
Commiphora in NE and East Tropical
Africa in different flora regions. The
symbols indicated in the map represent
different species: ● - C. monoica, ♦ - C.
suffruticosa, ♥ - C. oblongofolia, ▲ - C.
ovalifolia, ♣ - C. madagascarensis, ▼- C.
hornbyi, ■ – C. acuminata, ○ – C. engleri, ◘
- C. spathulata,. ◊ - C. stolonifera.
Out of the species of NE and E Tropical African
Commiphora currently dealt with, only a few of them
are out of the Somalia-Masai regional center of
One approach of tracing the phytogeographic
aspect of a given group is using Brooks’s parsimony
analysis (1990). In this analysis flora regions (areas)
94
Teshome Soromessa
Sci. Technol. Arts Res. J., July-Sep 2013, 2(3): 93-104
versus species were tabulated on the data matrix
and this has been generated from Table 1. Within
the developed matrix absence and presence were
considered. The data matrix was analyzed using
PAUP Swofford (2002). The result obtained is
reproduced in Figure 3.
The present gross distributional data for
Commiphora of NE and E Tropical Africa (Figure 3)
shows three types of pattern. The first type is the
EW-GG group that is characterized by wide spread
distributional pattern and know to have few species
of Commiphora. In this group few Commiphora
species are distributed such as C. africana, C.
habessinica, C. edulis and C. schimperi that
normally occurs elsewhere in the different areas.
Figure 3: The areagram obtained using BPA.
The second group, T1-S3 (Figure. 3), is partly
Tanzanian and characterized by group with very
limited distributional pattern. Some species
occurring in these areas are more or less endemic
(such as C. madagascarensis), others are
transgressing ones that transgress down to
Southern African region and still some display very
limited pattern of distribution. The transgressing
species include C. mollis, C. mossambicensis and
C. mombassensis.
The third group, SD-S1 group (Figure. 3), is the
pattern displayed by most Commiphora species.
About 70 % of Commiphora occurring in NE and E
Tropical Africa are found distributed in these
regions. Examples to this pattern are C.
hildebrabdtii and C. ogadensis.
This perhaps
seems to be the appropriate environment that suits
many Commiphora species to survive, diversify and
invade the region.
Except for the political
boundaries these areas are almost adjacent to one
another and sharing similar ecological niche that
support similar life forms.
Possible Origin and Migratory Route
The phylogenetic study of Commiphora species
reported by Teshome (2005) presumably indicated
that the primitive group with in the sections belongs
to section Cupulares which contains C.
eralngeriana, C. monoica, C. erosa, C. eminii, C.
hornbyi, C. unilobata and C. zanziberica. In addition
to this evidence, the Horn of Africa harbors all sex
forms that occur in the genus; i.e. hermaphrodite,
monoecious and dioecious with the possible
intermediate groups and the xerophytic and
mesophytic species of Commiphora also occur in
the NE and E Tropical Africa. Apparently it is
possible to make the presumptuous assumption that
the Horn of Africa is the origin of the group, with
more emphasis to the NE of Africa. Although Wild
(1965), didn’t explicitly pointed out about the origin
of the genus, he indicated that the occurrence of
very dry interpluvial periods in Africa put pressure
on the genus Commiphora to produce xerophytic
species now well represented in NE and SW Africa,
some of which migrated without difficulty through
95
Teshome Soromessa
Sci. Technol. Arts Res. J., July-Sep 2013, 2(3): 93-104
Table 1: Altitudinal ranges, average annual rainfall, pedological preference and distribution of Commiphora
species.
Scientific name
C. acuminata Mattick
Altitudinal
range in m
Annual
Rainfall in
mm
750-900
600-750
Pedological
preference
NE
K1-7
rocky slopes
sandy to
loamy,
recent lava
flows
sandy, rocky
lime stone
sandy, rocky
lime stone
sandy, black
cotton, rocky
slopes
rocky
limestone,
black cotton
C. africana Engl.
2-2100
200-850
C. alaticaulis Gillett
and Vollesen
300-1200
200-450
C. albiflora Engl.
700-1000
200-350
C. baluensis Engl.
600-1700
450-800
C. boranensis
Vollesen
750-1450
250-450
C. bruceae Chiov.
150-1100
200-280
alluvial sand
C. caerulea B.D. Burtt
500-1500
450-700
sandy
C. campestris Engl.
50-1200
230-800
sandy, rocky
lava hills,
alluvial
C. chaetocarpa Gillett
200
230
sandy
C. ciliata Vollesen
700-1250
300-450
C. confusa Vollesen
150-1300
300-700
C. corrugata Gillett
and Vollesen
300-1450
250-380
C. cyclophylla Chiov.
300-800
200-300
C. danduensis Gillett
450-1600
250-700
rock lime
stone hills
sandy, rocky
slopes
rocky
limestone
sandy,
limestone
slope
sandy
K1-7
SD,BA,HA
2
EF, AF, SU, AR,
GG, SD, BA, HA
1467
SD, BA, HA
1
SD, BA, HA
127
SD
1467
N12C1S3
CWS-Africa
Tropical and
southern
Africa
N2C2S1S3
23
Sudan
N1S1S2
N1-3C1-2
S1-3
3
2356
C2
SD, BA
1
C1-2S1
GG, SD, BA
12467
SD, BA, HA
1
C2S1
SD, BA, HA
1
N2-3C1-2 S1
SD
1
123467
C. ellenbeckii Engl.
300-1200
230-350
sandy, rocky
slopes
SD, BA, HA
1
C. eminii Engl.
100-1750
550-1200
rocky hills,
limestone
C. engleri Guillaumin
870-1650
450-800
rocky hills
C. erlangeriana Engl.
250-700
230-250
C. erosa Vollesen
200-400
230-300
C. fulvotomentosa
Engl.
200-1050
800-1000
C. gileadensis C. Chr.
150-750
200-350
467
Malawi,
Zimbabwe,
Botswana
C2S1-3
1
SD, GG
rocky slopes
123
14567
sandy, rock
slopes
650-950
S
C2S2
350-900
5-950
T1-8
SD,BA
2-1400
C. glandulosa Schinz
U1-4
56
EE, AF, EW, TU,
GD, WU, SU,
KF, GG, SD, BA,
HA
C. edulis Engl.
rocky
limestone,
gypsum
slope
gypsum hills,
alluvium
limestone
rocky
outcrops
rocky hills,
sand dunes
T1-8
3
1234567
1
S1-3
N1-3C1-2
S1-2
12345678
Zambia,
Malawi,
Mozambique,
Botswana,
South Africa
Zambia,
Malawi,
Mozambique
12456
SD, BA
1
N1-3C1-2 S1
SD, BA
17
C2S1-3
68
EE, HA
N1-3C1-2 S1
568
Egypt, Sudan
Zaire, Angola,
Zambia,
96
Teshome Soromessa
Sci. Technol. Arts Res. J., July-Sep 2013, 2(3): 93-104
C. gowlello Sprague
350-1400
200-350
sandy, stony
soil
C. gracilispina Gillett
350-400
230
sandy loam
C. guidottii Chiov.
250-400
230-250
C. gurreh Engl.
750-1500
200-500
gypsum soil,
stony slope
black cotton,
rocky lime
stone
sandy to
loamy, black
cotton
C. habessinica Engl.
500-1900
300-900
C. hildebrandtii Engl.
850-1500
300-550
C. hodai Sprague
400-650
230-250
C. hornbyi B.D. Burtt
380-1220
450-750
sandy soil
C. horrida Chiov.
500
250
sandy soil
rocky lime
stone slopes
red sandy
soil
C. kataf (Forssk.)
Engl.
260-1650
300-500
C. kua Vollesen
90-1000
230-350
C. lindensis Engl.
5-960
600-950
sandy soil
C. madagascarensis
Jacq.
5-660
750-950
rocky slopes
C. merkeri Engl.
700-1600
300-400
C. mildbraedii Engl.
450-1650
500-700
C. mollis Engl.
540-1500
400-900
C. mombassensis
Engl.
125
900
C. monoica Vollesen
1000-1400
250-450
drained
sandy soil
sandy soil,
rocky slopes
sandy, black
cotton soil
rocky places,
black cotton
coastal
dunes
rocky
limestone,
black cotton
390-1660
500-800
sandy soil,
black cotton
C. myrrha Engl.
250-1300
230-350
sandy to
loamy, rocky
lava hills
C. oblongifolia Gillett
600-1050
500-600
rocky hills
150-1050
300-400
C. oddurensis Chiov.
400-600
200-250
SD, BA, HA
N1-2C1-2 S1
1
rocky lime
stone hills
limestone
slopes
N1-3C2S2
SD, BA
SD, BA
EE, EW, TU,
WU, GD, GJ, SU,
WG, IL, GG, SD,
BA, HA
N2-3C1-2 S1
N1-3C1-2
S1-2
1
123467
123567
12
N1N2
SD, BA
N1-3 C2S1-2
HA
N1-2C1-2 S1
Zambia,
Malawi, Zaire,
Rwanda,
Burundi,
Djibouti
567
HA
C1C2S2
123
EE, AF, SD, BA,
HA,
2
147
47
368
All except
S3
N1-3C1-2
S1S3
S2S3
68
6
BA
2
147
sandy soil,
black cotton
C. mossambicensis
Engl.
C. obovata Chiov.
Malawi,
Mozambique,
Namibia,
Botswana,
Zimbabwe,
South Africa
1245678
Zaire, Angola,
Zambia,
Malawi,
Mozambique,
Namibia,
Botswana,
Zimbabwe, S.
Africa
8
Mozambique
1245678
Zambia,
Malawi,
Mozambique,
Botswana,
Zimbabwe
SD, BA
AF, SD, BA, HA
1
N1-3 C1-2
S1
47
SD, HA
7
N1C2
1
C1-2S1-2
97
Teshome Soromessa
Sci. Technol. Arts Res. J., July-Sep 2013, 2(3): 93-104
C. ogadensis Chiov.
500-1450
350-650
sandy soil,
black cotton,
alluvial
C. ovalifolia Gillett
800-1400
600-800
rocky slopes
C. paolii Chiov.
50-700
200-350
alluvial sand
C. pedunculata Engl.
200-1000
450-800
C. pteleifolia Engl.
1-1100
700-950
C. quadricincta
Schweinf.
40-750
200-350
C. rostrata Engl.
80-1350
200-450
C. samharensis
Schweinf.
150-400
150-250
C. sarandensis B.D.
Burtt
750-1300
350-450
sandy soil
rocky
escarpment
sandy, rocky
slopes, lava
hills
sandy soil,
rocky slopes
sandy and
rocky hills
stony soils,
hard-pan
soils
C. schimperi Engl.
430-2100
450-850
sandy, rocky,
black cotton
soils
C. sennii Chiov.
200-900
200-400
alluvium soil
rocky
outcrops
sandy soil,
black cotton,
basaltic soil
rocky slopes,
red soil
gypsum
slope, rocky
limestone
sandy soil,
rocky slopes
C. serrata Engl.
2-700
800-950
C. serrulata Engl.
1000-1850
350-750
C. spathulata Mattick
550-1100
450-600
C. sphaerocarpa
Chiov.
250-400
200-250
400-800
230-350
250-400
200-250
alluvial sand
690-1260
450-550
sandy soil
1000-1450
230-400
sandy soil,
rocky slopes
750-1100
250-550
sandy soil
C. sphaerophylla
Chiov.
C. staphyleifolia
Chiov.
C. stolonifera B.D.
Burtt
C. suffruticosa
Teshome
C. swynnertonii B.D.
Burtt
sandy, rocky,
black cotton
soils
sandy, stony
soil
SD, BA, HA
1
N1-3 C2S1-2
46
SD, BA, HA
147
GD, GJ, WG
C1-2S1S3
Mali to
Sudan,
Malawi,
Zambia
Zaire, Zambia,
Mozambique
78
7
3468
Nigeria, Chad,
Sudan
EE, AF, EW
GG, SD, BA, HA
N1-3C12S1-2
147
EE, GG
1
EW, TU, GD,
WU, SU, GJ, SU,
AR, GG, SD, BA,
HA
123467
In all
Sudan
N1C2
Zaire,
Botswana,
Zimbabwe,
Mozambique,
S. Africa
1245
123567
1
147
S1S2S3
68
Mozambique
SD, BA, HA
N1N2
567
SD, BA, HA
N1-3 C12S1
HA
N1-2 C12S1
SD, HA
C2S2
1567
SD
1
5
123467
2
C. terebinthina
Vollesen
200-1800
300-800
C. truncata Engl.
600-1050
250-400
C. ugogensis Engl.
800-1400
500-800
sandy soil
C. unilobata Gillett
and Vollesen
70-1000
200-350
alluvium soil
SD
147
C2S1S2
C. velutina Chiov.
400-900
230-300
sandy soil,
limestone
hills, old lava
flow
AF, SD, HA
1
N1-3C1-2
S1S3
C. zanzibarica Engl.
2-510
900-1050
coral rocks
near sea &
streams
KF, GG, SD, BA,
HA
HA
1
N1-3C12`S1-3
N1-2C1-2 S1
Zambia,
Zimbabwe
12457
7
Mozambique,
Malawi,
Zimbabwe, S.
Africa
98
Teshome Soromessa
Arabia (with six species of the Horn currently
occurring in Arabia) to India (one species of the
Horn which was cultivated occurs there) and are
represented today by species such as C. wightii
(synonym of the then C. mukul) and C. berryi.
Further more species that currently occur in India
include C. caudata, C. agallocha, C. pubescens and
C. myrrha (Chithra and Henry, 1997).
The transoceanic distribution of Commiphora
from the mainland in Madagascar, India and Arabia
on one side and to Latin America on the other side
is another remarkable feature of the group to be
portrayed here. In connection with phytogeography
the land bridge theory has been stipulated by
several authors, notably van Steenis (1962), Wild
(1965), Takhtajan (1969), Raven and Axelrod
(1974), Schuster (1976), Turner (1995), RidderNuman (1996) and Haegens (2000) including
literatures cited therein.
According to Raven and Axelrod (1974) and
literatures cited therein, the separation of Africa
from South America seems to have commenced
125-130 m.y. BP. The final marine connection
associated with the spreading apart of Africa and
South America took place slightly less than 100 m.y.
BP with the continent remaining in near contact
along strike-slip faults until at least 90 m.y. BP,
when northeast Brazil and Africa were separated by
only a narrow strait. The same authors adopted the
concept that Africa and Europe were connected via
Spain, in Early Paleocene (63 m.y BP). Africa may
have been connected with Asia through Arabia at
this time. Finally they came to the notion that from
the Early Paleocene into the Upper Eocene (53 m.y.
BP), Africa and Europe seem to have become more
widely separated. Furthermore Schuster (1976) and
literatures cited therein suggested that until at least
75 million (roughly Late Cretaceous) years ago
there were archipelagic connections between the
Indian plate, the Mascarene Plateau, Madagascar
and Africa. During this same period, India and
Australia continued to move northward towards
Eurasia, opening the Indian Ocean and beginning to
close the Tethys Ocean. As India separated from
the southeast coast of Africa it pulled Madagascar in
its wake.
Following this plate tectonic events, the pattern
of evolution and distribution of organism has been
considered as events of great importance. Raven
and Axelrod (1974) indicated that direct migration of
organism between Africa, Madagascar (probably
also India) and South America last possible about
100 m.y. BP and also reestablishment of direct
connection between Africa and Eurasia was about
17 m.y. BP. Rabinowitz et al., (1983) and literatures
cited therein, attested that the magnetic data point
Sci. Technol. Arts Res. J., July-Sep 2013, 2(3): 93-104
to the motion of Madagascar relative to Africa being
from the north, with the Africa-Madagascar
separation started beginning during the time of the
Jurassic quite zone (~165 Ma) and ending at a time
of formation of anomaly M9 (~121 Ma) denoting that
the Africa-Madagascar separation began at about
the same time of as the breakup of Gondwanaland
and the separation of North America from Africa. On
the other side, Storey et al., (1995) dated the
separation of Madagascar and India before ~ 88
Ma. However, recent studies of the Mozambique
channel, revealed the possibility of the land bridge
connecting mainland Africa and Madagascar from
mid-Eocene to early Miocene (45-26 Ma) (McCall,
1997 as cited in Möller & Cronk, 2001). On the
other hand authors like Coleman et al., (1992),
Tadiwos Cherinet et al., (1998) and Ukstins et al.,
(2002) dated the separation of Africa-Arabia to 3020 Ma range. From the above geological dating of
separation events, one can come to the conclusion
that the separation of Madagascar predates that of
Arabia from Africa. This geological episode can be
augmented by the presence of 6 Commiphora
species in Arabia that also occur in the Horn as
opposed to the endemic species of Commiphora in
Madagascar. This shows that the Arabian species
of Commiphora migrate recently to Arabia than to
the rest of the world which still is in favor of the
geological time of the separation of the two
continents.
Correlation of continental separation with that of
the fossil evidence might be the best evidence for
the biogeography of a given group. However, the
fossil records of a tropical family, Burseraceae, is
very scanty with the available ones most from north
temperate zone latitude, i.e. a little has changed
since Muller (1981) suggested “at present only
doubtful records of rare bureseraceous pollen grains
have been published, interpretation of which will
depend on a future detailed study of the recent
pollen morphology of this family.” Nevertheless,
Graham & Jarzen (1969) had recorded Bursera
simaruba type pollen from Puerto Rico as Oligocene
communities.
Furthermore, from the Eocene of Panama,
Graham (1985) described Tetragastris-like pollen
and Protium-like pollen, but this pollen (Protium-like)
is considered as much more like Chrysophyllum L.
pollen by Harley & Daly (1995). Taylor (1990) also
reported 6-7 putative genera of the family
Burseraceae which are of Paleocene to upper
Eocene age which include pollen of putative Protium
and Tetragastris and the leaves of putative Bursera
showing that the probable age of the family with
much reservation, from this scanty information, lies
between Paleocene-Eocene.
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Teshome Soromessa
Sci. Technol. Arts Res. J., July-Sep 2013, 2(3): 93-104
Taking the separation of the continents and the
meager information on the age of the family into
consideration one could possibly assume that
Commiphora migrate from the Horn of Africa to the
different African regions, to Madagascar via the land
bridge that was supposed to connect Africa and
Madagascar, to Arabia and might or might not reach
India. The recent report on the displacement of
Bursera leptophloeos Mart. from Bursera to
Commiphora leptophloeos (Mart.) Gillett comb. nov.
of Commiphora Gillett (1980) indicated the
existence of Commiphora species in Latin America.
It is then impractical to assume that either
Commiphora migrated from Africa to Latina America
or from Latin America to Africa, for the fact that the
separation of these two continents predates the
evolution and diversification of most angiosperm
families. One hypothetical explanation on the
existence of Commiphora in Latina America and
India might be linked to polyphyletic origin (note that
the present study didn’t consider the whole genus to
confirm whether it is polyphyletic or monophyletic in
origin) of Commiphora and that Commiphora might
have derived from Bursera itself which is currently
distributed in both places. The endemicity of the
Madagascan species of Commiphora might suggest
the possible speciation events in the area.
Wild (1965) on the other hand indicated that
there are double patterns of distribution of
Commiphora species: his first argument was that
the occurrences of interpluvial periods in Africa
produced xerophytic species that migrated to Arabia
and India. His second argument for the notion was
that the Lemurian land-bridge played its role since
the more mesophytic species in one of the more
favorable pluvial periods migrated along the
Lemurian bridge into Madagascar with its twenty or
so species and also into India and Ceylon. The
morphological resemblances of C. wightii to that of
the section containing Commiphora (which contains
C. quadricincta, a northern species and C.
madagascarensis, C. oblongifolia and C. ovalifolia
the Tanzanian species) may suggest a two way
migration of species that go with Wild’s (1965)
notion.
In contrast to the different kinds of colonization
event, another possible explanation of the
distribution of species across the continent is long
distance dispersal. Even if this process might
happen (animal dispersal in this case) in the past,
the viability of the seeds of Commiphora species is
quite in question.
Vegetation, Altitudinal & Pedological Preference
Most, if not all, species of Commiphora in the NE
of Africa occur in the southern and southeastern
parts of Ethiopia. These include the lowlands of
Hararge (HA in Figure 1), Bale (BA), Sidamo (SD),
and some parts of Gamo Gofa (GG), with a high
species concentration of Commiphora in Sidamo.
Similarly, the East African species of Commiphora
are highly concentrated in the Northern Frontier
Province and the coast of Kenya in K1 and K7 as
recognized in Flora of Tropical East Africa. High
concentration of species occurs in T5 and T6 of
Tanzania and U1 (around the Karamoja district of
Uganda). Figure 4 shows comparison of the
different flora regions in terms of the species
abundances within the different political boundaries.
40
35
No. of s pe cies
30
25
20
15
10
5
0
S B H GA S WG T A KG W E E I K K K K K K K T T T T T T T T U U U C S C N N N S S
D A A G F U U D UR F J L WE L 1 7 4 6 2 3 5 5 6 2 7 1 8 4 3 1 2 3 2 1 1 1 2 3 3 2
No. of species 36 28 30 10 6 6 3 3 3 3 2 2 2 4 7 1 33 21 19 10 8 8 1 19 18 15 13 13 12 12 12 6 2 1 35 32 26 25 24 19 15 13
Flora regions
Figure 4: Comparison of different flora regions in terms of abundances of Commiphora species. The Flora
regions are as recognized in the Flora of Ethiopia, Flora of Somalia and Flora of Tropical East
Africa. Note also C2 of Somalia has high species concentration.
100
Teshome Soromessa
The vegetation of these areas, although not
studied deeply, have been classified and mapped
by various authors. The physiognomic study made
by Pichi-Sermolli (1957) resulted in the recognition
of 24 vegetation units in his publication on the
geobotany of Ethiopia, Eritrea, Djibouti and Somalia.
Of 24 vegetation units recognized by Pichi-Sermolli
(1957), unit 2, 3, 4, 6, 7, 11, 12 and 13 were
considered to, at least, occur in one or more areas
of the lowlands of Hararge, Sidamo, Bale and Gamo
Gofa. However, some of his units, particularly unit 6,
7 and 11 are generalized ones and could not exactly
tell the nature of vegetation in the areas.
Breitenbach (1963) studied the vegetation of
Ethiopia based on physiognomy in relation to
altitude and humidity and came up with seven
vegetation types including various sub-types. In this
study he mapped the lowlands of Hararge, Bale,
Sci. Technol. Arts Res. J., July-Sep 2013, 2(3): 93-104
Sidamo and Gamo Gofa under his lowlandwoodland, lowland-savannahs and lowland-steppes
units. Although Breitenbach (1963) identified seven
major units, the borders drawn on the vegetation
maps produced from his study is quite similar to the
one produced by Pichi-Sermolli's (1957). The next
comprehensive study of African vegetation was that
of White (1983). According to White (1983) southern
and southeastern Ethiopia belongs to the SomaliMasai Regional Center of Endemism, one of his
major units within the flora of Africa as a whole. It is
the home of Commiphora and Acacias extending
down to Somalia, Kenya, Tanzania and Uganda. In
this regional center different plant communities
could be encountered. This includes CommiphoraAcacia, Commiphora woodland (as in the case of
pure Commiphora baluensis woodland in El Siro
area, Figure 5) and or Commiphora bushland.
Figure 5: Some vegetation formations with Commiphora species. A-B, C. baluensis woodland; C, AcaciaCommiphora woodland around Sof Umar; Weyib river in the center; D, dry Commiphora
woodland.
Generally
speaking
areas
harboring
Commiphora, belong to deciduous woodland and/or
bushland usually conspicuously rich in species of
Acacia and Commiphora. Associated with these
vegetation types, there are extensive grassland
areas that are found at relatively higher altitudes,
notably at Nagelle and Jijiga, which probably were
formed as a result of anthropogenic influences in
the past years. Altitudinally Commiphora occur from
almost sea level to about 2000 m above sea level
101
Teshome Soromessa
Sci. Technol. Arts Res. J., July-Sep 2013, 2(3): 93-104
(Table 1), on alternatively sandy soils, rocky hills,
limestone, gypsum and sometimes on black cotton
soils.
Further categorization of species based on the
width of altitudinal niche they occupy shows that
some species perform best in a wide range of
altitude exploiting broader ecological niches while
others preferably occur in a narrow range. Of all the
species considered here for investigation, 20
species occur within a 500 m altitudinal range
showing narrow range of performances (e.g., C.
acuminata, C. chaetocarpa, C. gileadensis, C. erosa
and C. suffruticosa, Table 2) and 7 species occupy
altitudinal range exceeding 1500 m utilizing all
opportunity from lowland, premontane to low
montane range and successfully invading the
habitat.
Table 2: Categorical performance of species in terms of altitudes.
Ranges of altitudinal
performance
Within 500 m range
Within 500 – 1000 m range
Within 1000 – 1500 m range
Above 1500 m range
Number of
species
20
29
17
7
Commiphora are aridisols species, a soil type
known to occur in dry areas in general and in
lowlands of Oromia, Ogaden and southern Ethiopia
in particular (Mesfin Abebe, 1998). Some species of
Commiphora occur preferably in the woodland
vegetation on brown soils, black cotton soils and on
a rocky lava places. They form association with
Acacia, Boswellia, Combretum, Terminalia, Barbeya
and some species of Lannea. Some of these
species of Commiphora include Commiphora edulis,
C. habessinica, C. pedunculata, C. engleri, C.
serrulata and C. gurreh with C. pedunculata being
an exception as it also occurs in wooded grassland
vegetation. Other species of Commiphora tend to
occur in bushland vegetation forming an extensive
association with Acacia and some Acanthaceae.
Some notable species to this group are C.
acuminata, C. albiflora, C. campestris, C.
ellenbeckii, C. horrida, C. sphaerocarpa, C.
staphyleifolia and C. unilobata. The bushland
Commiphora largely occur on rocky lime stone hills.
Other than the bushland or woodland species, some
are widespread over both bushlands and woodlands
frequently occupying sandy soil that overlay
limestone. These species include the widespread C.
africana, C. baluensis and C. schimperi. Other
widespread
species
include
Commiphora
boranensis, C. confusa, C. corrugata, C.
cyclophylla, C. monoica, C. myrrha and C. rostrata.
Commiphora corrugata, C. baluensis and C. rostrata
also occur in wooded grassland vegetation, which is
primarily dominated by grass. Interestingly,
Commiphora corrugata and C. hildebrandtii are
species that often perform best with Combretum
molle and Terminalia brownii.
Implications for in-situ Conservation
Commiphora form important and major parts of
the vegetation in what is known as White’s (1983)
Examples of species in that category
C. acuminata, C. erosa, C. suffruticosa, etc.,
C. alaticaulis, C. albiflora, C. ciliata, etc.,
C. corrugata, C. gurreh, C pedunculata, etc.,
C. africana, C. edulis, C. schimperi, etc.,
Somalia-Masai Regional Center of Endemism. It is
also the best sources of browse for the large
livestock of the region. The need for trees that can
be browsed coupled with the need for arable land in
the areas may lead to degradation of their genetic
diversity. Alluding to earlier discussion on the
diversity of Commiphora species, flora regions like
SD, HA, BA, K1, S1, C2 and C1 are regions of high
genetic pool. Identification of rich centers of diversity
is then important for undertaking in-situ
conservation of the genetic resources. Regions with
high diversity of Commiphora species could serve
as a possible in-situ conservation site. Although
considering all these regions for in-situ conservation
seems to be expensive, regions that are endowed
with greater genetic pool can be considered for
conservation purposes. Good examples are Sof
Umar in Bale and Walensu Ranch in Sidamo where
12 and 13 species of Commiphora have been
recorded. Similar gene conservation activities can
be made in the other regions having high genetic
diversity of Commiphora species.
CONCLUSIONS
Commiphora are pan tropical in distribution
performing well in arid and semi-arid environments
occupying an ecological range between 1 – 2100 m
above sea level striving best on aridisols. More
over, some species of the genus tend to perform
well in a narrow ecological range. Results from the
phytogeographic analysis of the group revealed
three patterns of distributions: species with wider
distribution ranges, endemic and transgressing
species having limited niche and those found in flora
regions that are appropriate environment for
Commiphora to diversify and invade the regions.
102
Teshome Soromessa
Although tracing the migratory route and possible
origin of the group requires numerous information,
studies such as Wild (1965) and Teshome (2005)
suggested that the possible origin of Commiphora
seems to be in the Horn of Africa. Based on the
separation of the continents and the meager
information on the age of the family into
consideration it is possible to assume that
Commiphora migrate from the Horn of Africa to the
different African regions, Madagascar and Arabia. It
seems practical to note that Commiphora did not
migrate to Latin America nor vice versa, since the
separation of African and Latina American
continents predates the evolution and diversification
of most angiosperm families showing that
Commiphora might have polyphyletic origin.
However, the migratory route of Commiphora still
requires more data, particularly complete data of
Commiphora of the world. Data on the age of the
genus is also important to corroborate it with the
plate tectonic theory.
Sci. Technol. Arts Res. J., July-Sep 2013, 2(3): 93-104
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