Systematic presentation of the diversity of parasitic angiosperm.
Parasitic plants continue to gain research attention due to their remarkable lifestyle pattern that clearly cites them as a typical example of a biological oddity. They have defiled the basic characteristics of plants to become dependent on other plants for existence. Aside from their unique heterotrophic mode of feeding, host range and preference, seed germination clues, distribution patterns vary across different parasitic plants, which has partly ensured their presence in virtually every plant community. Among the above-listed factors, host range and preference, in particular, appears to be a major significant factor that shapes their distribution around the world, enabling certain species to thrive in various microclimates. The Nigerian environment has heterogeneous vegetation, traversing mangroves, rainforest, savannah vegetation, and its home to host parasitic plant species, including endemic, natives, and exotic ones. The present chapter gathered and synthesized available information regarding parasitic plants in Nigeria, particularly their biology and the host species supporting their population. Aside from the devastating menace some parasitic plants are known for, this report recognizes their ethnobotanical relevance. Thereby stimulating research interest in these highly specialized plant groups.
- Parasitic plants
- host species
Parasitic plants are an exceptional group of plants that have defiled plants’ basic characteristics of solely synthesizing their own organic nutrient into dependent on other plants for survival . Consequently, they have adapted to an association with a host plant using a physiological bridge known as the haustorium, where water and organic nutrients are transported . This form of association enables the host plant to shape the distribution of the parasite. Based on the degree of host dependence, parasitic plants can exert their impact on an individual or community basis; some parasitic plants, for example,
Despite the uniqueness of plant parasitism, its evolution is polyphyletic . It is reported to have evolved approximately 12 or 13 in the angiosperm phylogeny (Table 1) There are approximately 4,500 species in about 280 genera belonging to 20 families . While some angiosperm families, like Balanophoraceae, consist entirely of parasitic members, others have only a few representatives, for example, Lauraceae. Parasitic plants also exist in different life forms, including annuals and perennials, e.g. (
|Order||Parasitic Evolutionary Linages||Nature of Parasitism||Parasitic||Hemiparasitism||Holoparasitism|
Parasitic plants are virtually present in all plant communities throughout the world. Moreover, a positive relationship between nonparasitic and parasitic plants has been established . By implication, plant-rich ecosystems are also expected to be rich in parasitic plants. The strategic position of Nigeria in West Africa has endowed it with wealthy biodiversity, distributed within different ecological zones, comprising: mangrove, rainforest, montane, and the savanna- Guinea, Sudan, and Sahel . These different eco-geographical zones support a huge diversity of parasitic plants, including endemic ones. Even though some parasitic plant species are important pests of human agriculture and forestry, many are highly valued for food, wood, and medicinal properties . Therefore, the present chapter aims to utilize available literature regarding parasitic plants in Nigeria to document their biology, identified host plants, and their ethnobotanical relevance.
2. Materials and methods
The author obtained information on the biology and ethnobotany of parasitic plants in Nigeria from various sources, which include; Published materials in the form of journals from databases, such as Google Scholar, Elsevier, Web of Science, and SCOPUS, and textbooks, particular checklists, monographs, floras (see references). Herbaria visited include Forest Herbarium Ibadan (FHI) and the Edo State University Herbarium (EUH). Also, personal communication with experts about parasitic plants in Nigeria was valuable to completing this report.
3. Distribution of parasitic plants in Nigeria
The strategic position of Nigeria in the tropics just above the equator within Latitudes 10 0N and 140 N has endowed it with very rich yet heterogeneous vegetation. The temperature is high and ranges from 25–34°C. The mean annual rainfall ranges from 500 mm in the north to 2500 mm in the coaster region. The phytogeography of Nigeria could broadly be categorized into two major regions; the Sudano-Zambezian and the Guineo-Congo . The Northern part of the country falls under the Sudano-Zambezian region, comprising the Sudanian and Sahelian domains. The Guineo-Congo region of Nigeria is made up of Guineo domain to which the west and central part of the country belongs, and the Congo domain has the eastern part of the country. The different domains support various plant species, some of whom are notable host species to the parasitic plants domiciled in the Nigerian environment. For the current discourse on the distribution of parasitic plants, the Nigerian environment will be characterized into two, Northern Nigeria, predominately, savannah, and Southern Nigeria, where the rainforest forest belt is located.
3.1 Northern Nigeria
Northern Nigeria has a Savannah ecoregion, comprising the Guinea savanna bordering the rainforests, the Sudan savanna, and the Sahel bordering the desert. The guinea savanna is found in Kaduna, Kwara, Kogi, and Benue states; the Sudan savanna, in Kano and parts of Borno, Sokoto, Niger, and Bauchi states; and the Sahel around the Lake Chad. The savanna ecoregion is renowned for a climate that has a short wet and long dry season. The average monthly temperatures are around 29°C during the hot season and around 18°C during the cool season. The total annual rainfall varies greatly from around 500 mm in regions on the semi-desert fringes to about 1500 mm in regions bordering the rain forests. The savanna rainfall is insufficient to support a rich growth of trees but is mostly dominated by perennial grasses with few tree clumps. In the Guinea savanna, the grasses grow tall during the rainy season. Trees occur quite close together, especially along the rain forest fringe. The grass is shorter in the drier Sudan savanna, and the trees are fewer and more scattered. In the Sahel, which is borders the Sahara desert, the land is quite bear with clumps of short grass and a few isolated shrubs and trees. During the dry season, the grass is usually dry and brown, and bush fires are common occurrences. The underground parts of the grasses survive the dry season and fires and grow again when the rains come. In terms of the parasitic plant distribution, the Nigerian Savanna is home to one of the most devastating parasitic genus,
|Species||Family||Potential Distribution||Herbarium voucher number||Host species||Literature|
|Loranthaceae||SN: Edo, Ogun, Ondo||FHI 16684||[5, 12]|
|Loranthaceae||NN; Kano, Bauchi, Yola|
|FHI 16279||[5, 13]|
|Loranthaceae||NN: Sokoto, Zamfara, Bauchi, Yola||FHI 15893|||
|Oronbanchaceae||SN: Oyo||FHI 13735||parasitic on some members of the poaceae family|||
|Oronbanchaceae||NN: Niger, Bauchi SN: Ondo||FHI 24448||parasitic on some members of the poaceae family|||
|Oronbanchaceae||NN: Sokoto, Niger, Kogi, Bauchi, Ilorin||FHI I9265|
|Semi parasitic on members of papilionoidae|||
|Loranthaceae||SN: Ogun, Ondo||FHI 173041|||
|Loranthaceae||SN: Ogun, Anambra, Lagos, Cross River||FHI 6679|||
|Loranthaceae||SN: Cross River||FHI 33216||Coffea, Citrus, ||[5, 13]|
|Loranthaceae||SN: Cross River||Coffea, Citrus, |||
|Santalaceae||SN: Edo, Cross River and Osun||EUH 00011||Companion tree plant species||[20, 21]|
SS: Oyo, Cross River.
|FHI 3420||[12, 13]|
|Loranthaceae||NN: Niger, Kogi SN: Cross River;|||
|Loranthaceae||NN: Kogi, Adamawa|
SN: Ogun, Cross River;
|Loranthaceae||SN: Akwa Ibom, Cross River;||[12, 24]|
|Oronbanchaceae||NN: Niger, Kaduna, Adamawa||FHI 24389||Corn, sorghum, and sugar cane|||
|Oronbanchaceae||NN: widespread||FHI 4557||rice, wild grasses||[5, 25]|
|Oronbanchaceae||NN: Sokoto, Adamawa||Cowpea||[5, 25]|
|Oronbanchaceae||NN: widespread||EUH 00022||Sorghum roots||[5, 25]|
|Loranthaceae||SN: widespread||EUH 00029||[5, 26]|
|Loranthaceae||NN: widespread||FHI 24389|||
|Loranthaceae||NN: Zamfara, Kano, Bornu||FHI 15683||[5, 13]|
|Loranthaceae||SN: Oyo||FHI 3442||[12, 13]|
|Loranthaceae||SN: widespread||EUH 00101||[5, 13]|
|Balanophoraceae||SN: Edo, Cross River, Oyo, Ondo, Ogun, Bayelsa||EUH 00055||[27, 28]|
|Loranthaceae||SN: Akwa Ibom, Cross River||EUH 00121|||
|Loranthaceae||Rain forest: Akwa Ibom, Cross River||EUH 00122||[2, 27]|
3.2 Southern Nigeria
The Southern part of Nigeria experiences heavy and abundant rainfall due to its proximity to the equatorial belt. It comprises majorly the rainforest and the swarm forest that borders the Southern Atlantic Ocean. The rainforest belt occurs in the regions that lie between the equator and latitude 5o − 10 oN and S. The climate in the tropical rainforest region is hot and wet throughout the year. The mean annual temperature is 27°C while the mean total annual rainfall is 2000 mm. The rainforest is characterized by dense and stratified vegetation, comprising various broad-leaved tree species sandwiched by lianas and herbaceous climbers. The rain forest covers Oyo, Edo, Delta, Imo, Cross River, Ogun, Ondo, and Rivers state, while the swarm forest is situated across the Niger Delta region. Parasitic plants are very much represented in the Nigerian rainforest. The largest parasitic tree,
4. Systematic presentation of parasitic angiosperm in Nigeria
Members of the genus
4.3 SANTALALES: nigerian loranthaceae
Loranthaceae is the largest family in Santalales with about 73 genera and over 900 species . It has a wide distribution particularly in the southern hemisphere, including both subtropical and tropical areas. Members of Loranthaceae have mostly stemmed parasites, with exception of a few root parasites. They possess both primary and secondary haustoria. Loranthaceae leaves are usually evergreen, leathery, and simple with smooth edges but variable forms, from broad flat leaves to cylindrical succulent leaves. Flowers are nearly always bisexual, with 4–7 perianth members who normally are of the same color. Stamens occur in the same number as the perianth parts, but there is only one pistil. Insects and birds, especially sunbirds pollinate flowers. The fruits are berry-like, single-seeded and of different color depending on species. Birds are the main disperser. The family- Loranthaceae is represented in Nigeria by
The Tapinanthoid group has simple to branched hairs. There are three flower types in this group. Some possess relatively small, non-explosive flowers, which are mostly adapted to pollination by insects. They are considered primitive for example is
The Taxilloid group has stellate hairs and has a flower that is both explosive and vented. Example
The leaf blade is ovate to oblong, simple and entire in shape, arranged in an alternate to almost opposite. Flowers are green in color and arranged on spines around older branches. Flowers are green in color. Unisexual flowers are present, with the female flowers slightly larger than male flowers . The flowers develop into hard, yellow-colored ellipsoid drupes containing a single large seed that weighs up to 100 g. The tree is monoecious. Hence, it is expected that the plant undergoes self-fertilization (allautogamy), leading to genetic stability. Although little is known about the pollination biology, the pollination type is likely either by ants (myrmecophily) or bats (cheiropterophily) due to the small greenish flowers that preclude its chances of being pollinated by birds . Seeds are speculated to be dispersed by large forest animals such as elephants.
thonningia sanguinea (Balanophoraceae)
The life-cycle of
cuscuta australisR.Br. (Convulvulaceae)
5. Ethnobotanical relevance of parasitic plants
The term Ethnobotany was first used by Harshberger  to denote the study of plants used by primitive aboriginal people subsequently; different workers have defined the subject, greatly enlarged the scope and accepted it as an interdisciplinary science for a holistic approach to man–plant relationship, hence different definitions of the concept of ethnobotany exist. Allem,  defined the concept as the biological, economic and cultural inter-relationship between people and plants in the environment where they exist. Schultes and Raffauf  broadly defined the subject as human evaluation and manipulation of plant materials, substances and phenomena in societies. Jain  related it to the study of how people make use of plants. According to Pushpangadan and Kumar , it is the entire realm of useful relationship between plant and humans. These definitions point out a relationship between people of a given community or society, the environment and the plant diversity in that particular community.
Ethnobotany has now been recognized as an integral part of indigenous/local knowledge of a particular society. Thus, different societies or communities have their own knowledge about plants and their uses. Indigenous knowledge represents an immense valuable database that provides humanity with an insight into how numerous communities have interacted with the changing environment, providing local solutions for local problems and suitable ways for coping with challenges posed by specific conditions. According to Warren and Cashman , ethnobotanical knowledge is how most communities survived for centuries by adapting themselves to their environment, using their intrinsic knowledge of associated resource management.
Parasitic plants are keystone species in plant communities, exhibiting a unique and important ecological role . They are common in many natural and semi-natural ecosystems, from tropical rain forests to the savanna. Although some parasitic plant species are important pests of human agriculture and forestry, many are highly valued for food and wood as well as for their medicinal and esthetic properties .
The study and management of parasites have historically focused on the control, and even elimination, of parasite populations, for example, researchers have intensified efforts to eradicate several mistletoe species,
The importance of indigenous knowledge is overwhelming especially with regard to parasitic plants. Aiyeloja and Bello  valued it as the sum of the experience that forms the basis for decision making for familiar and unfamiliar problems and challenges in a local community. The overall ethnobotanical uses of parasitic plants are quite high. However, the traditional knowledge of these plants have been widely threatened by current trends of economic globalization that promote intensive agriculture, industrialization, and the migration of rural populations to urban areas. Consequently, it is crucial to record this fast-disappearing knowledge before it is lost along with the present generation of elderly persons. Table 3 shows the ehnobotanical relevance of parasitic plants.
|Species||Geographical location; plant parts use; ethno-uses||References|
|In West Africa, the leaves of |||
|In Western Kenya, the flowers and leaves of ||[44, 45]|
|Several tribes use the whole plant of |||
|In Saudi Arabia, the whole plant of |||
|In Libreville (Gabon), the leaves of |||
|In the Southeast part of Nigeria, the Leaves and fruits of ||[48, 49]|
|In West Africa, |||
|In Southern Mozambique, the inflorescence of |||
|In Southern Nigeria, the bark and the seeds of ||[32, 46, 51]|
|In southwest Nigeria, the leaves of |||
|In South Africa, the stem and leaves of |||
|In Northern Nigeria, the stem and leaves are used to treat dermatosis, leprosy ulcer, pneumonia and jaundice|||
|Southwest Nigeria leaves; the whole plant is used to treat circulatory and respiratory disease problems, malaria, diabetes, hypertension and sterility in cows.||[54, 55]|
|In Southern Nigeria, the whole plant is used with other materials against anemia, asthma, diarrhea, infant illness, rheumatism, skin infection, sore throat, stomach upset. It is also valuable as (a) an aphrodisiac|||
Parasitic plants play a vital role in plant communities, and their diversity is quite huge, with various species inhabiting the different ecosystems in Nigeria. The study and management of parasites have historically focused on controlling and even eliminating parasite populations. Although some parasitic plant species are important pests of human agriculture and forestry, many are highly valued for food and wood and their medicinal properties. The current chapter provides an update on the various potential uses of parasitic plants in Nigeria from an ethnobotanical perspective. Therefore it is important to look beyond just their economic implications and approach the conservation of parasitic plants holistically. Next time you walk along nature trails in the forest, look out for some stem parasites on the branches of trees and root parasites at the base of host plants.