Ecological Distribution of Tithonia diversifolia (Hemsl). A. Gray-A New Exotic Weed in Nigeria
Ecological distribution of Tithonia diversifolia (Hemsl). A. Gray was studied in six states of the southwestern Nigeria using three locations in each of the States. The presence of T. diversifolia was recorded in all the States and locations surveyed in varying numbers with associated weeds. Survey data were analysed using detrended correspondence analysis (DCA). The first two ordination axes of the DCA accounted for 67.2% (Axis 1, 40.6%; Axis 2, 26.6%) of variance on the site and species components. The DCA separated Ogun State locations from others. T. diversifolia was found to be closely associated with Boerhavia coccinea, Fleurya ovaliflora, Indigofera subulata, Merremia dissecta, Mimosa pudica, Momordica foetida, Phyllanthus mimosoides, other species of Phyllanthus, Physalis angulata, Schrankia leptocarpa and Sesbania parchycarpa in Ekiti, Lagos, Ondo, Osun and Oyo States while these species were absent in Ogun State.
Tithonia diversifolia (Hemsl). A. Gray belongs to the family Asteraceae (formerly Compositae). It originated from Mexico, Central America and Cuba (Royal Horticultural Society, 1956) and has since naturalised in Tropical Asia and Africa (Blake, 1921; Blake, 1957). The genus Tithonia is made up of 11 species which include Tithonia diversifolia, T. excelsa, T. fruiticosa, T. glaberrima, T. ovata, T. playlepis, T. rotundifolia, T. scaberrima, T. speciosa, T. tagitiflora and T. tubiformis; all of which originated from Mexico, Central America and Cuba (Arias et al., 1982; Royal Kenya Horticultural Society, 1957). Agnew (1974) reported that the only member of the genus found in Tropical Africa (and Nigeria in particular) is Tithonia diversifolia.
T. diversifolia, the Mexican sunflower as it is commonly called, was probably introduced into West Africa as an ornamental plant (Akobundu and Agyakwa, 1987) but has become a weed of field crops and roadsides (Akobundu and Agyakwa, 1987). Opinions varied as regards the introduction and subsequent establishment of T. diversifolia in Nigeria. However, the most authentic opinion suggests that the plant gained entrance into Nigeria through Ogbomoso with the seeds of Zea mays imported from Israel (Akobundu and Agyakwa, 1987; Lordbanjou, 1991) by the then Oyo State Phased Agricultural Development Project (OSPADP) in the late 1970 s. The plant has since spread to various parts of the southern States of Nigeria especially in the last fifteen years where conditions that favour its growth exist. In these areas, the plant has established itself as a serious weed of arable crops, plantations abandoned lawns and roadsides.
T. diversifolia, a new exotic weed in Nigeria, is one of the most underestimated problems in Nigerian agriculture (Akobundu, 1987; Chukwuka, 2003; Ikemefuna, 1995; Njoku, 1995). For most African crop farmers, weed represent the main threat to their crops because the work involved in getting rid of them is cumbersome, time-consuming, enormous and therefore demands considerable manpower. It is therefore in the light of this, that the study on the ecological distribution of T. diversifolia in Nigeria was undertaken.
Most imported neotropical plants have become established in the tropics as serious weeds. Examples of such weeds include Chromolaenna odorata (Olaoye, 1974) and Tithonia diversifolia (Akobundu and Agyakwa, 1987; Chukwuka, 2003) . The genus Tithonia is well distributed all over the world. Various workers (Agnew, 1974; Blake, 1921; La deeke, 1982; Standley, 1926) have reported on the world distribution of Tithonia diversifolia. T. diversifolia according to their reports is found in North America (Mexico); South America (in Argentina, Cuba, Natal and Guatemela); Asia (in Philippines, Republic of Myamar, Malaya, Indonesia
and India, West Bengal, Tranvancore and Mycore); Australia (in New South Wales) and Africa (in Tanzania, Cameroon, Kenya, Uganda, Malawi, Egypt, Zambia and Nigeria). Although its mode of distribution has not been well documented, it is connected with importation of food crops, which were meant for cultivation. Other possible means of its distribution is by seed dispersal through the agency of wind and other dispersal mechanisms (for example birds and insects) since the seed is usually light and could be carried by wind over reasonable distance.
In Nigeria today, Tithonia diversifolia occurs mainly in the forest zone and the adjoining savanna along the roadsides, farmlands and lawns. Its presence has been recorded and observed in five States (Lagos, Ogun, Oyo, Osun and Ondo) of Southwestern Nigeria (Chukwuka, 2003; Lordbanjou, 1991). It is however prominent along roadsides in the guinea and derived savanna especially near river courses (Chukwuka, 2003). It has been observed on Kafanchan-Jos road, in Akwa-Ibom, Rivers, Cross River and parts of Delta, Imo and Anambra States (Chukwuka, 2003).
MATERIALS AND METHODS
Study area: The six States (Oyo, Osun, Ondo, Ogun, Ekiti and Lagos)
of the Southwestern Nigeria were chosen for the study between January 2 and
June 6, 2001. The general mean annual rainfall for this ecozone is 1997 mm per
annum; mean maximum and minimum temperatures are 37.57 and 21.37 °C respectively
(Ekeleme, 1986). The rainfall/evapotranspiration ratio of the ecozone has been
estimated to be 1.06 (Oke, 1982). The climate is seasonal with two distinct
wet and dry seasons. The soils are mainly of the Egbeda, Olorunda and Iwo series
(Smyth and Montgomery, 1962). The series have parent rocks, which are combinations
of fine-grained biotite gneiss with coarse granite and gneiss. The soil colour
usually varies from brown to brownish red which are fairly clayey with fine
and coarse sand fractions.
Field studies of Tithonia diversifolia in southwestern Nigeria: A study of the distribution of Tithonia diversifolia in Southwestern Nigeria was carried out. This was determined by field survey. Three locations were chosen in each of the six States of Southwestern Nigeria and the inventory of plant species encountered was taken. The locations were chosen from where T. diversifolia were found to be growing in the wild. The locations surveyed are shown in Fig. 1.
In choosing the locations, sites with abundant presence of T. diversifolia
were identified in each State. Three of such sites were randomly selected for
detailed investigation. One hundred metre-long and 5 metre-wide belt transect
was laid in each location.
showing the six southwestern states of Nigeria and locations surveyed
In each transect, twenty-one 1 x1 square meter quadrats were systematically
laid at every 5 m point. All the plant species encountered in each quadrat were
identified, listed and enumerated. Any unidentified species was taken in a plant
press to the University of Ibadan Herbarium (UIH) for identification and authentication.
Botanical nomenclature follows that of Hutchinson and Dalziel (1954). Density
data obtained from the survey were subjected to Detrended Correspondence Analysis
(DCA) in order to ascertain floristic gradient and continuity within the six
States (Hill, 1979; Ter Braak, 1988) and default option of the CANOCO program
was used (Ter Braak, 1988).
The locations visited and surveyed were Ibadan, Ogbomoso and Ilora-Oyo (in Oyo State); Gbongan, Ile-Ife and Ilesha (in Osun State); Ifetedo-Ondo, Oba-Ile and Owo (in Ondo State); Aramoko-Ekiti, Ado-Ekiti and Orin-Ekiti (in Ekiti State); Odeda-Abeokuta, Ilugun and Erunwon-Ijebu-Ode (in Ogun State) and Ikeja, Apapa and Badagri (in Lagos State). Tithonia diversifolia was encountered in all the states and locations surveyed in varying proportions (Appendix 1) with associated weeds.
In Oyo State, the survey showed that T. diversifolia was associated with the following plant species-Amaranthus spinosus, Asystasia gangetica, Cassia alata, Centrosema pubescens, Commelina nodiflora, Corchorus olitorius, Desmodium scorpiurus, Euphorbia hyssopifolia, Fleurya ovalifolia, Ipomoea involucrata, Mariscus longibracteatus, Merremia aegyptia, Merremia dissecta, Merremia kentrocaulos, Panicum maximum, Panicum repens, Paspalum orbiculare, Phyllanthus amarus, Phyllanthus niruroides, Physalis angulata, Schwenckia americana, Sesbania parchycarpa, Setaria sp. and Trianthema portulacastrum.
In Osun State, T. diversifolia was associated with Albizia sp., Boerhavia coccinea, Calopogonium mucunoides, Cassia occidentalis, Centrosema pubescens, Chromolaena odorata, Indigofera subulata, Mimosa pudica, Panicum maximum, Phyllanthus amarus, Physalis angulata, Physalis sp., Pueraria phaseoloides, Schrankia leptocarpa, Sida acuta and Triumfetta cordifolia.
Also associated with Tithonia diversifolia in Ondo State were Centrosema
pubescens, Chromolaena odorata, Desmodium scorpiurus, Dioscorea
rotundata, Euphorbia heterophylla, Imperata cylindrica, Panicum
maximum, Paullinia, pinnata, Phyllanthus mimosoides;
P. niruroides, Phyllanthus sp., Spigelia anthelmia and
ordination (Detrended Correspondence Analysis) of six southwestern states
of Nigeria with reference to Tithonia diversifolia and associated
classification of plants associated with Tithonia diversifolia
in six states of Southwestern Nigeria. The locations surveyed are Ibadan,
Ogbomoso, Ilora-Oyo, Gbongan, Ile-Ife, Ilesa, Ifetedo, Oba-Ile, Owo, Aramoko-Ekiti,
Ado-Ekiti, Orin-Ekiti, Odeda, Ilugun, Erunwon, Ikeja, Apapa and Badagri.
Species in the code numbers are as follows:
In Ogun State, Tithonia diversifolia were found to be associated with
Calopogonium mucunoides, Centrosema pubescens, Cleome viscosa,
Commelina benghalensis, Commelina nodiflora, Indigofera sp.,
Ipomoea sp., Panicum maximum, Pueraria phaseoloides, Spigelia anthelmia
and Talinum triangulare.
Associated with Tithonia diversifolia in Ekiti State were Centrosema pubescens, Chromolaena odorata, Panicum maximum, Sida acuta and other unidentified grass species.
In Lagos State, Tithonia diversifolia was found to be associated with Amaranthus spinosus, Azadiractha indica, Brachiara deflexa, Centrosema pubescens, Cleome viscosa, Commelina nodiflora, Croton lobatus, Luffa aegyptiaca Momordica feotida, Panicum maximum, Paspalum conjugatum, Sida acuta, Sterculia tragacantha, Strophanthus hispidus, Talinum triangulare, Trianthema portulacastrum and other unidentified grass species.
The species ordination (Fig. 2) indicates a discontinuous
gradient along the first and second axes (Appendix 2). The first axis shows
a cluster of species that are closely associated with Tithonia diversifolia
(TIDI) and these include: Boerhavia coccinea (BOCO), Fleurya ovaliflora
(FLOV), Indigofera subulata (INSU), Merremia dissecta (MEDI),
Mimosa pudica (MIPU), Momordica foetida (MOFO), Phyllanthus
mimosoides (PHMI), Phylanthus sp. (PHSP), Physalis angulata
(PSAN), Schrankia leptocarpa (SHLE) and Sesbania parchycarpa (ESDA).
Other species which are closely associated with each other but not closely associated
with Tithonia diversifolia (TIDI) include: Amaranthus spinosus (AMSP),
Azadiractha indica (AZIN), Brachiara deflexa (BADE), Desmodium
scorpiurus (DESC), Dioscorea rotundata (DIRO), Euphorbia hyssopifolia
(EPHY), Ipomoea involucrata (IPIN), Panicum repens (PARE),
Paspalum orbiculare (PABI), Paullinia pinnata (PAPI), Physalis
sp., (PSSP) and Sterculia tragacantha (STTR).
ordination (Detrended Correspondence Analysis) of six southwestern states
of Nigeria with reference to Tithnonia diversifolia and associated
classification of the six states of southwestern Nigeria (Oyo, Osun, Ondo,
Ekiti, Ogun and Lagos) where Tithonia diversifolia was distributed
and the 18 locations surveyed. The locations are Ibadan, Ogbomoso, Ilora-Oyo,
Gbongan, Ile-Ife, Ilesha, Ifetedo, Oba-Ile, Owo, Aramako-Ekiti, Ado-Ekiti,
Orin-Ekiti, Odeda, Ilugun, Erunwon, Ikeja, Apapa and Badagri. The sites
in the code numbers are in appendix 3
The second axis also shows a discontinuous gradient with Chromolaena odorata
(CROD), Centrosema pubescens (CEPU) and Seteria sp., (SESP) at
the positive and other species at the negative ends. The species ordination
diagram gives an insight into the species abundance in the states and locations
surveyed. This is further confirmed by the species classification diagram (Fig.
3), where the first division separated the species closely associated with
T. diversifolia from those not closely associated with it as shown by
the grouping in the positive and negative axes of the ordination diagram. Species
present at one end of the ordination gradient are not likely to be present at
The site ordination diagram (Fig. 4) shows a discontinuous gradient along the first and second axes. The first (horizontal) axis shows a gradient separating Ogun State locations (LG 17, EW6, EW17, LG3, DD2, LG2, LG20, DD9, DD11, LG11, EW16 and LG21) on the negative side of the axis. The second axis also shows a discontinuous gradient with Odeda (DD14, DD5, DD6, DD4, DD12, DD15, DD8) in Ogun State on the negative side of the axis (Appendix 3). This result is further confirmed by the site classification diagram (Fig. 5), which grouped Ogun State sites together (in code numbers 00000, 00001, 00010, 00011, 00100, 00101, 00110 and 00111). The stand classification diagram (Fig. 5) using the species presence or absence as indicators separated Ogun State locations from other locations surveyed; thereby confirming the results of the site ordination.
Tithonia diversifolia was found to be well spread and adapted in southwestern Nigeria especially within the forest zone. This therefore accounts for its spread in Oyo, Osun, Ondo, Ekiti, Ogun and Lagos States in varying densities. In these States, T. diversifolia was found to be commonly associated with the roadsides, open and disturbed habitats where plant cover is low, being absent from areas of mature plant establishments. Akobundu and Agyakwa (1987) and Lordbonjou (1991) reported similar findings on T. diversifolia. Although T. diversifolia is a roadside plant, it has taken over a vast area of land in Ogbomoso, Ilora and Ibadan (Oyo State); Gbongan (Osun State); Odeda, Ilugun and Erunwon (in Ogun State). Consequently, most farmers in these areas have to abandon their farmlands due to the stubbornness of T. diversifolia as well as aggressive colonization of their farmlands by T. diversifolia and problems associated with cultural control of the weeds by hand weeding and hoeing. It is remarkable to infer that T. diversifolia, a roadside plant is gradually becoming a weed of arable crops in these areas.
In all the States surveyed, Tithonia diversifolia was found to be commonly associated with Centrosema pubescens and Panicum maximum. These two species are common roadside, cultivated, open places and abandoned field plants as reported elsewhere (Akobundu and Agyakwa, 1987). Within each State surveyed, the under listed species were found to be associated with T. diversifolia at least in two of the locations. These are Centrosema pubescens, Desmodium scorpiurus, Merremia aegyptia, Sesbania parchycarpa and Trianthema portulacastrum (for Oyo State); Calopogonium mucunoides, Centrosema pubescens and Panicum maximum (for Osun State); Centrosema pubescens, Chromolaena odorata and Panicum maximum (for Ondo and Ekiti States); Calopogonium mucunoides, Centrosema pubescens, Panicum maximum and Spigelia anthelmia (for Ogun State) and Commelina nodiflora, other unidentified grass species, Panicum maximum, Sida acuta and Talinum triangulare (for Lagos State).
However, species ordination by detrended correspondence analysis (DCA) of plant species in the six States and eighteen locations surveyed showed three clusters of species along axis 2, which were closely associated with Tithonia diversifolia and with one another in varying degrees. The species that were closely associated with each other were clustered together.
The first cluster of species associated with T. diversifolia (TIDI)
consisted of Boerhavia coccinea (BOCO); Fleurya ovaliflora (FLOV);
Indigofera subulata (INSU); Merremia dissecta (MEDI); Mimosa
pudica (MIPU); Momordica foetida (MOFO); Phyllanthus mimosoides
(PHMI); Phyllanthus sp. (PHSP); Schrankia leptocarpa (SHLE);
Sesbania parchycarpa (ESDA) and Spigelia anthelmia (SPAN).
The second cluster consisted of Amaranthus spinosus (AMSP); Azadiractha indica (AZIN); Brachiara deflexa (BADE); Desmodium scorpiurus (DESC); Dioscorea rotundata (DIRO); Paspalum orbiculare (PABI); Physalis sp. (PSSP) and Sterculia tragacantha (STTR) while the third cluster consisted of Euphorbia hyssopifolia (EPHY); Ipomoea involucrata (IPIN), Panicum repens (PARE) and Paullinia pinnata (PAPI).
The species in the third cluster are rare species (with very low densities
per square metre) encountered during the survey. Except for Brachiara deflexa,
Phyllanthus mimosoides and Spigelia anthelmia that were encountered
in three out of six States surveyed. Other rare plant species were encountered
in either one or two States. Also, except for Amaranthus spinosus and
Spigelia anthelmia that were encountered in five and seven locations respectively,
out of eighteen locations surveyed others were encountered in four or less locations.
It is therefore the rareness of these species that grouped them together in
their various clusters at anytime they were associated with Tithonia diversifolia.
Generally, most of these rare species were encountered in Oyo and Osun States,
which belong to the Egbeda soil series. This seems to suggest that the association
of T. diversifolia with the plants in these clusters affected them negatively
such that most of them did not survive over time with T. diversifolia
interference. Baruah et al. (1994) working on growth inhibitory sesquirterpene
lactones and flavones from T. diversifolia reported similar findings.
The above result was further confirmed by species classification of plants associated
with T. diversifolia in the six States surveyed.
On the other hand, the absence of plant species such as Asystasia gangetica,
Boerhavia coccinea, Cassia occidentalis, Fleurya ovaliflora,
Imperata cylindrica, Indigofera subulata, Merremia dissecta,
Merremia kentrocaulos, Mimosa pudica, Phyllanthus niruroides,
Phyllanthus sp; Schrankia leptocarpa, Schwenckia americana,
Sesbania parchycarpa and Triumfetta cordifolia, in Ogun State sites
which were closely associated with Tithonia diversifolia in other states
may be responsible for the separation of Ogun State in the stand ordination.
Ojo and Ola-Adams (1996) reported similar findings in their work on measurement
of tree diversity in Nigerian rainforest. The separation of Ogun State locations
on both axes of the site ordination diagram as confirmed by the site classification
diagram may be attributed to the soil and parent materials of the area, which
belongs to the Odeda series.
||Plant species associated with Tithonia diversifolia in the sampling
locations in six states of southwestern Nigeria. Values are mean densities
m -2 ± standard error from 21 stands
||Names of plant species with their codes as reflected in figure 2 (species
||List of locations surveyed in the six southwestern states and their codes
as reflected in Fig. 4. Numbers attached to the codes
indicate the location number during the survey
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