20 
Bulletin of the EANHS 27(2/3) 
elsewhere. The genus MarsHea is adapted lo seasonal 
water bodies. Thus fern species can be used as 
Indicators of habitat conditions. For instance, the 
bracken fem grows normally in forest edges and its 
presence below a tree canopy could be used as an 
indicator of past forest disturbance. Again the presence 
of filmy ferns is an indication of a wet humid undisturbed 
forest no matter how dry everything seems at the time. 
Many species of Ac/iniopierix and f'chaea nre indicators 
of dry areas while those of Marsilea ( water-floating 
ferns) are indicators of seasonal pools and streams. 
Diversity and biogeography 
Johns lists 519 species from East Africa in his recent 
Checklist of Easl African Ptcrulophyies, information 
on the distribution was available for 434 of these. Table I 
lists the number of species present in Kenyu. Tanzania 
and Uganda. Families with a high number of genera and 
species arc rhclypteridaceoc (13 genera. 33 species ), 
Dyopteridaccae (1 1 genera. 59 species), I'olypodinceae 
{ 1 1 genera. 26 species), and Adiantiaccac ( 1 0 genera. 57 
species). Some families however, have very few genera 
( I or 2) but a large number of species, eg Asplcmaceac 
(2 genera). On the other hand monogcneric und 
monospecific families arc also present in our region such 
as Maratiiaceae, Osmundaceae and Davalliaceac 
The number of recorded species may increase when 
taxonomic research on each family has taken place 
although the overall specics/genera ratio in Johns (1991) 
is 5.04, which is very high. liven withoui the 99 species 
ofAsplenlum in Johns' list, the ratio is 4.08. Faden (1994) 
gives a ratio of 2.82 for the area of Kenya above 1 000 m 
altitude, which is much more reasonable for an ancient 
Table 1 Number of specie s per family of 
Ptendophytes occurring in each of the East African 
countries: Uganda (U) Kenya (K) and Tanzania (T) 
FAMILY 
U 
K 
T 
Actmioptendaceae 3 
3 
4 
Adiantaceae 
28 
27 
47 
Asplentaceae 
54 
53 
67 
Azoliaceae 
2 
1 
2 
Blech naceae 
2 
e 
8 
Cyalheaceae 
3 
2 
11 
Davaliiaceae 
1 
1 
1 
Dennslaedtiaceae 
11 
11 
17 
Oryoptefidaceae 
15 
14 
27 
Gietcneruaceae 
2 
2 
4 
GfammtxJaceae 
1 
* 
16 
Hymenophyllaceae ^ 2 
12 
24 
lomanopsidaceae 10 
13 
23 
Marattiaceae 
1 
1 
1 
Mannleaceae 
2 
7 
B 
Olcandraceae 
7 
6 
10 
Ophroglossaceae 
10 
a 
11 
Osmundaceae 
1 
i 
1 
Parttenaceae 
1 
i 
1 
Poi»podiaceae 
16 
13 
19 
Ptendaceae 
16 
15 
25 
Salvmiaceat* 
0 
2 
2 
Schizaeaceae 
1 
3 
7 
Thelypteridaceae 
15 
18 
26 
Viltanaceae 
4 
5 
8 
Woodsiaceae 
4 
7 
15 
Grand Total 
2 22 
236 
386 
group of plants, many of which arc at the end of 
evolutionary lines. It is clear that the taxonomy of many’ 
groups is in a state of flax and that differences of opinion 
exist between experts. There are many specimens in the 
East African Herbarium that have not been properly 
identified due lo lack of up to date literature and 
specialised botanists. 
Figure 1 shows how species are shared between the 
three countries of East Africa. As with orchids (Vandcn 
Figure 1 Number of fem species unique to each 
country, and snared between different 
combinations of countries 
Berghe & Bytchicr. 1995). the number of species 
occurring in Tanzania but not in cither of the two other 
East African countries is considerable higher than the 
species unique to either Kenya or l Iganda For both 
anunal groups for which a similar analysis was done, 
mammals (Gathuu& Vandcn Bcrglic. 1 993) and Diptora 
(De Meyer *7 ul . 1994). Uganda scored highest It 
would be interesting to subject more taxonomic groups 
to this analysis, to check whether a trend develops - 
four groups is not enough to draw definite conclusions. 
Fem disiribulion with respect to tJ»e botanical regions 
used in the Flora of Tropical East Africa (TTEA) is 
summarised in figure 2. A map of the floral regions, and 
a short discussion was given in a previous issue of the 
Bulletin anden Berghe & Bytcbier, 1 995 ). Most ferns 
arc found in U2 in Uganda, K4 in Kenya; and T2, T3 T6 
and T7 in Tanzania. Of course species can occur in one 
or more botanical regions and therefore regional 
numbers of species ure independent The areas with 
most ferns include high altitudes such as Kwenzori 
Mountains (Uganda); Mis Kenya, A her dares, Miui and 
Elgon (Kenya); and Mts Meru. Kilimanjaro. Parcs. 
Usambarasand Ulugurus (Tanzania). High rainfall and 
cool mist-cloud climates occur in these greater altitudes 
which are ideal lor the establishment of ferns 
Conservation Status 
Unfortunately ideal fem habitats arc also the best 
potential agricultural areas in East Africa. At the same 
time the population rate of increase in East Africa, 
