**1. Introduction**

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 [1]. 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 [2]. 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, *Striga*, can severely reduce host performance, leading to host death, while others like *Thonningia sanguinea* exert a mild effect on its host. On a community scale, parasitic plants can significantly orchestrate changes in community structure, diversity, vegetation cycling, and zonation by either altering the competitive balance between host and nonhost plants [3] or necessitating an irregular uptake of host solutes which consequently


**Table 1.**

*Systematic presentation of the diversity of parasitic angiosperm.*

*Parasitic Plants*

*Aspects of the Biology and Ethnobotany of Parasitic Angiosperm Species in Nigeria DOI: http://dx.doi.org/10.5772/intechopen.98667*

affect other trophic level organisms (such as herbivores and pollinators). These impacts also result in a ripple effect that may extend to the abiotic environment, including impacts on nutrient cycling, soil water relations, local temperature, and atmospheric CO2 concentrations. Importantly, such major impacts can occur even when parasitic plants are minor components of the ecosystem [4].

Despite the uniqueness of plant parasitism, its evolution is polyphyletic [1]. 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 [3]. 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. (*Hydnora* spp. and *Thonningia sangunea*), climbers (e.g., *Cassytha*), shrubs (*Tapinanthus globiferous*), and Tree (e.g., *Okoubaka aubrevillei*). Parasitic plants can be characterized based on the presence or absence of photosynthetic pigments, in which case hemiparasites like *Cassytha filiformis, Agelanthus spp., Globimetula spp.* etc., have the ability to photosynthesize to some extent due to the presence of chlorophyll or holoparasite like *Hydnora* spp., *Thonningia sanguinea*, *Balanophora* sp. *Cuscuta* derived their entire organic nutrient from the host plant due to chlorophyll deficiency. Parasitic plants could also be categorized as stem parasites. For example, *Cassytha filiformis, Agelanthus spp., Globimetula spp.* are attached to the host stem or root parasites, e.g., *Thonningia sanguinea, Hydnora spp.* attached to the host plant's root.

Parasitic plants are virtually present in all plant communities throughout the world. Moreover, a positive relationship between nonparasitic and parasitic plants has been established [4]. 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 [7]. 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 [8]. 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 0 N 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 [9]. 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 semidesert 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, *Striga.* The species are found on cultivated lands, abandoned farmlands, and waste and weed-infested sites, depending on the presence of the host crop. *Striga astiatica*, *S. aspara*, *S. hermonthica*, *S. gesnerioides* are some of the species found in the savanna habitat. The basis for their occurrence only in the savanna part of the country is yet to be fully ascertained. Mohamed et al. [10] reported that the rain forest's high rainfall and moisture levels result in a "wet dormancy" of *Striga* seeds, consequently precluding its occurrence in the zone. Notwithstanding, most host crops, such as Corn, sorghum, and sugar cane, are cultivated majorly in the savanna part. *Hydnora abyssinica,* a root holoparasitic plant, was recently spotted around Nekong, Wusali ward, Kanke Local Government Area, Plateau State, Nigeria [11]. Notable members of the Loranthaceae family like *Agelanthus dodoneifolius, A. heteromorphus, Globimetula cupulata, Tapinanthus cordifolius, T, globiferous, T. pentagonia*, and *T. preussii* are attached to trees and shrubs in this zone. **Table 2** shows potential distribution and host species of common parasitic plants of Nigeria

#### **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 o N and S. The climate in


#### *Aspects of the Biology and Ethnobotany of Parasitic Angiosperm Species in Nigeria DOI: http://dx.doi.org/10.5772/intechopen.98667*


#### *Parasitic Plants*


**Table 2.** *Potential distribution and host species of common parasitic plants of Nigeria.*
