Diversity of life-forms within Sapindaceae Juss . in West Africa and Western Cameroon : A field guide

One of the major challenges faced by biologist during field studies is the identification of plant species and this is most evident in the tropics where biodiversity richness is very high. Hence this study was conducted in order to document and produce a guide for the identification of the diversity of life forms that represents the family Sapindaceae in West Africa. In view of this, plant exploration was carried out in five West African countries with the aim of collecting and recording the different life forms in the family Sapindaceae as well as their specific locations. This revealed that Sapindaceae are widely distributed in West Africa and the highest number of species was recorded in Nigeria (47 taxa). A total of 104 species was recorded in the region and these are represented by diverse life forms ranging from trees (58 species) to shrubs (32 species) and climbers (4 species) with compound trifoliate (e.g. Allophylus), paripinnate (e.g. Deinbollia) or imparipinnate (e.g. Paullinia) leaves. Flowers are arranged in groups either as cymes or racemes. Fruits are in the form of berry (e.g. Melicoccus), capsules (e.g. Blighia) or drupes (e.g. Deinbollia); some are inflated (e.g. Cardiospermum) or trilobed and woody (e.g. Chytranthus). This study provides a guide to field identification of members of the family Sapindaceae in West Africa and can be seen as a step in solving taxonomic identification problems and biodiversity conservation as a whole.


INTRODUCTION
The family Sapindaceae Juss., is one of the families in the order Sapindales and can be divided into 5 or 6 subfamily depending on the treatment.Most Sapindaceae are large emergent trees or erect shrubs however some are tendril lianes (Acevedo et al., 2011).They are comprised of about 140-150 genera with 1400-2000 species worldwide.Many of these are lactiferous, that is, they contain milky sap, and many contain mildly toxic saponins with soap-like qualities in the foliage and/or the seeds or roots.Approximately one-third of the members of the family are found in the tribe Paullineae.Members include economic plants which are largely used as lumber trees or oil seed crops although some are edible.
The majority of species are native to Asia, although there are a few in South America, Africa and Australia (APG II, 2003).They occur in temperate to tropical regions throughout the world with about 18 (Hutchinson  and Daziel, 1958) to 26 (Adeyemi and Ogundipe, 2012) genera in west tropical Africa and 13 (Keay et al., 1964) to 18 (Adeyemi and Ogundipe, 2012) species in Nigeria.Sapindaceae are recognizable by their often spiral, alternate, simple, or more commonly pinnately compound leaves that often have sub-opposite leaflets and a terminal rachis tip.Most often they are pollinated by birds or insects, with a few species pollinated by wind (Singh, 2004).The fruits are fleshy or dry.They may be nuts, berries, drupes, schizocarps, capsules (Bridgesia), or samaras (Acer) often red, containing seeds (Heywood, 1978).The embryos are bent or coiled, without endosperm in the seed, but frequently with an aril (Singh, 2004).Members of the family Sapindaceae are one of the most important forest species to be conserved and valued in Africa due to their multiple uses, high nutritional content and medicinal value.Globally, biodiversity is being threatened by climate change as well as human activities and this has aroused concerns about their conservation status.Hence, this current study is designed as an effort to aid in the conservation and identification of this plant family in Western Africa.Our aim is to explore the diversity of family Sapindaceae in West Africa, with emphasis on the collection, identification and preservation of the collected plant specimens as well as production of a field guide for field identification purposes.

Study area
The study was carried out in the western part of tropical Africa and five countries were visited namely: Nigeria, Ghana, Togo, Ivory Coast and western Cameroon.The study area is characterized by tropical rain forest and prominent water bodies.The land is plain lying less than 300 m above sea level, though isolated high points exist in some areas.

Sample exploration
The national herbaria as well as local herbaria were visited so as to observe the samples in the repositories, take necessary morphological data from each of the samples and collect some of the samples examined where permission is given to do so.The visit provided information on the last location in which the sample was recorded in the region and this informed our decision on where to collect samples in the field.
Consequently, various national parks, forest reserves and botanic gardens were visited in West Africa for the collection of fresh samples of the plant specimens.Permission was obtained from the various authorities involved in each region in order to collect samples from the reserves.
Access to the reserves was possible only through the use of a 4x4 wheel drive vehicles and motorcycles due to the rugged and untarred nature of the roads.Some reserves could only be assessed by trekking some distances of up to 40-50 km as the case may be.A list of the herbaria and reserves visited is shown in Table 1.

Preservation and identification of samples
Preliminary identification was achieved with the aid of floras including that of Hutchinson and Daziel (1958), Fouilloy and Hallé (1973) and Cheek et al. (2000).For preparation of voucher specimens, a part (usually branch) of each plant sample was placed in between each old newspapers and this was kept in a plant press.The press was tied with twines and kept in the dryer for two days in order to prevent the decomposition of the plant material.Each of the dried specimens was then removed from the newspaper and mounted on white cardboard papers using white gum (glue).Label was attached to each of the herbarium specimen in order to give a full description of the plant, its location, the date of collection and the name of collector.This was then authenticated at the Forestry Herbarium, Ibadan and deposited at the University of Lagos Herbarium for reference purposes.

Data analysis
Data obtained was analyzed using Shannon and Wiener indices following Ubom ( 2010) Magurram (1988) and Kent and Coker (1985).The Shannon and Wiener Diversity Index, which accounts for species richness and how the species are distributed, is derived from the relation: Where: H1 = Shannon-Weiner index; S = number of species; Pi = proportion of individuals or abundance of the i th species expressed as a proportion of the total number of individuals of all species: In = log base10.

RESULTS
Sample exploration was carried out across five African countries and 35 plant species were collected from the field (Table 2) while 69 species were retrieved from the herbarium (Table 3), identified and authenticated at the Forestry Herbarium Ibadan.Our sampling revealed that Sapindaceae are widely distributed in West Africa being represented by 26 genera and 104 species.Of these species, 4 are climbers 32 are shrubs and 58 are trees representing 3.84, 30.76 and 65.38% of the total number of species, respectively.The largest population was recorded in the southern highlands of Nigeria (47 taxa), western region of Cameroon (45 taxa) and western and eastern River banks in Ghana (25 taxa) (Figure 1); however, taxa shared are highest between Nigeria and Cameroon.Leaf, stem, fruit and flower samples were collected and photographs were taken (Plate 1).Also, GPS coordinate of each sample was recorded and inputted into a map (Figure 2).Voucher samples of samples collected from the field have been deposited at the University of Lagos Herbarium (LUH) Nigeria.

DISCUSSION
Most of the samples collected from the field were found in Cameroon, due to the presence of large area of conserved forest, that is, 24 samples, followed by Nigeria (14 samples).Only 5 samples each was found in the other three countries visited: Ghana, Togo and Ivory Coast.However, the forestry herbarium in Nigeria houses the largest number of taxa (33) of all the herbarium visited.Taxa shared were highest between Nigeria and Cameroon with 9 taxa endemic to the mountains.A key item in the conservation of biodiversity is identification of species and this could be challenging especially in field studies.Over the years, this has been made difficult by the fast rate of disappearance of species largely as a result of changes in the climate as well as a wide range of unsustainable human activities hence the need for this study.All the observations made in this study are consistent with earlier description of the family given by Heywood (1978), Singh (2004), Acevedo-Rodríguez et al. (2011) and Adeyemi et al. (2013).With exception of a few species, members of Sapindaceae were largely found in lowland forest.Most of the taxa are native to the region with exception to Melicoccus bijugatus and Nephelium lappaceum which are exotic species.Also, 11 of the species encountered are yet to be identified at the species level due to absence of fruiting structures in the samples.
Several authors, including Alamu and Agbeja (2011) and Pelemo et al. (2011), have highlighted the main drivers of deforestation to include agriculture, logging and mining, use of fuel wood and logging all of which pose threats to biodiversity  Limbe Botanic Gardens De WILDE, J.J 14-Mar-34 FHI    conservation.This is confirmed in this study as it was observed that some of the species earlier recorded in some of the reserves were no longer found largely due to the high rate of deforestation and agricultural activities going on in the reserves.
This study provides a virtual guide to field identification of members of the family Sapindaceae in West Africa and can be seen as a step in solving taxonomic identification problems and biodiversity conservation as a whole.It is therefore expected that this report will assist scientists in the area for on-the spot identification of plants in the field.

Figure 1 .
Figure 1.Number of taxa encountered per country visited.

Figure 2 .
Figure 2. Distribution of sapindaceae in West Africa and western Cameroon: White dots show the locations.

Figure 3 .
Figure 3. Number of life forms of family Sapindaceae represented in West Africa.

Table 1 .
Sites visited for plant collection.

Table 2 .
Samples collected in the field and their locations.

Table 3 .
Samples collected from the herbarium and their locations.

Table 4 .
Percentage number of species encountered according to genera.