Research Article |
Corresponding author: Ling-Yun Chen ( lychen83@qq.com ) Academic editor: Clifford Morden
© 2020 John K. Muchuku, Andrew W. Gichira, Shu-Ying Zhao, Jin-Ming Chen, Ling-Yun Chen, Qing-Feng Wang.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Muchuku JK, Gichira AW, Zhao S-Y, Chen J-M, Chen L-Y, Wang Q-F (2020) Distribution pattern and habitat preference for Lobelia species (Campanulaceae) in five countries of East Africa. PhytoKeys 159: 45-60. https://doi.org/10.3897/phytokeys.159.54341
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East Africa is one of the centres of distribution and diversity for Lobelia L. (Campanulaceae, sub-family Lobelioideae). Lobelia habitats in East Africa have been facing habitat fragmentation and loss, which are recognised as a major threat to biodiversity. However, previous plant conservation studies in East Africa only focused on protected areas and ignored unprotected areas. Future conservation strategies of plants, such as Lobelia, will depend on knowledge of their distribution patterns and habitat preference in East Africa. To understand the distribution pattern and the habitat preference of Lobelia in five countries (Kenya, Uganda, Tanzania, Rwanda and Burundi) of East Africa, we conducted a literature review in the seven major vegetation regions (afro-alpine, afro-montane forest, drier savannah, grasslands, wetter savannah, Zambezian woodland and semi-desert and desert). We also employed meander and patterned searches, which allowed greater opportunities for recording Lobelia species. Our results showed that the genus is distributed in all of the seven regions of the five countries with 54 taxa. The afro-montane forest region, with 41 taxa, is the richest in species diversity, followed by the Zambezian woodland region with 18 taxa. The semi-desert and desert region has the lowest number with only four taxa. The afro-alpine region has 15 taxa, although the region is the smallest by area. The herbaceous type was found in all regions, while the giant type has a clear preference for the afro-alpine and afro-montane forest regions. Future conservation for Lobelia should consider its habitat preference by, for example, focusing on the afro-alpine and afro-montane forest regions. This study will facilitate the setting of future conservation strategies for Lobelia.
East Africa, Flora of Tropical East Africa, habitat preferences, Lobelia, vegetation region
Understanding species richness, habitat preferences and geographical distribution patterns is imperative in formulating conservation strategies. Assessment of species habitat and distribution patterns dates back to the late 18th century (
East Africa (EA) includes Kenya, Uganda, Tanzania, Rwanda, Burundi, Ethiopia, Somalia and South Sudan (
Lobelia L. (Campanulaceae, sub-family Lobelioideae) includes about 437 species. The genus is cosmopolitan, distributed in both temperate and tropical regions of Africa, America, Australia, New Zealand, Hawaii, Asia and other regions (
Habitat loss and fragmentation are the major causes of biodiversity loss worldwide (
The distribution pattern of lobelias across different vegetations in the EA and the habitat preference remain unknown. As far as we know, lobelias are non-uniformly distributed in EA (
In this study, we reviewed previous literature and extracted data from our field survey. We aimed to identify the distribution pattern and habitat preference of Lobelia in five countries in the EA region (Fig.
This study covered five of the eight East African countries, i.e. within and amongst the early administrative divisions of Kenya (K1–7), Uganda (U1–4), Tanzania (T1–8), Rwanda and Burundi. The other three countries (Ethiopia, Somalia and South Sudan) in EA have limited data from both herbaria and the Flora of Tropical East Africa (FTEA) on the distribution of the lobelias. Therefore, they were not included in this study. The study area ranged from coastal regions to the alpine zones of high mountains with changes in the elevation gradient. To obtain a clear understanding of the Lobelia habitats and distribution patterns, seven vegetation regions (afro-alpine, afro-montane forest, drier savannah, grasslands, wetter savannah, Zambezian woodland and semi-desert and desert) were used (Fig.
The major vegetation regions in East Africa, modified from
All lobelias described in the Flora of Tropical East Africa (
To maximise recording lobelias in traversed habitats, meander and patterned searches (
The lobelias in the seven regions of the five countries are represented by 54 taxa including herbs, shrubs and sub-shrubs (Table
Lobelias diversity and distribution in Kenya, Uganda, Tanzania, Rwanda and Burundi of East Africa.
Species/subspecies name | Growth height | Elevation (m) | Habitat | Vegetation region | Data sources |
---|---|---|---|---|---|
Lobelia aberdarica R.E.Fr. & T.C.E.Fr. | Erect subshrub 3.5 m | 1700–3550 | Upland swamp | Amfr | SR, HS |
L. adnexa E.Wimm. | Erect herb ca. 40 cm | 1000–1600 | Shady or rocky areas | Amfr, Zwr | FTEA |
L. angolensis Engl. & Diels | Procumbent 25 cm | 1600–2200 | Moist wetland banks | Amfr, Zwr | SR, FTEA |
L. bambuseti R.E.Fr. & T.C.E.Fr. | Erect subshrub 8 m | 1800–3300 | Forest, bamboo zone | Amfr | SR |
L. baumannii Engl. | Procumbent herb 80 cm | 700–2450 | Stream banks in shade | Amfr, Gr, Wsr, Zwr | HS, FTEA |
L. bequaertii De Wild. | Erect subshrub 4–5 m | 3250–4100 | Moorland and bog | A-ar | HS, FTEA |
L. burttii subsp. meruensis E.B.Knox | Erect subshrub 3 m | 3150–3900 | Wet alpine or ravine | A-ar | SR, HS |
L. burttii subsp. telmaticola E.B.Knox | Erect subshrub 3 m | 3000–3900 | Wet alpine and moorland | A-ar | SR, HS |
L. cheranganiensis Thulin | Decumbent herb 0.6 m | 2500–3400 | Moorland | A-ar | SR |
L. chireensis A.Rich. | Herb ca. 25 cm | 500 –1250 | Marshy muddy areas | Amfr, Dsr, Wsr, Zwr, S-ddr | FTEA |
L. cymbalarioides Engl. | Prostrate herb ca. 70 cm | 1500–3000 | Moist forest and woodland floor | Amfr, Zwr | FTEA, LR |
L. deckenii Hemsl. | Erect subshrub 4 m | 3000–4500 | Wet moorland | A-ar | SR |
L. deckenii subsp. incipiens E.B.Knox | Erect subshrub 5 m | 2700–3000 | Mist forest | Amfr | SR |
L. deckenii subsp. burtii (E.A.Bruce) Mabb. | Erect subshrub 3 m | 3150–3800 | Stream bank or ravine | A-ar |
SR, HS, LR ( |
L. dissecta M.B.Moss | Erect herb ca. 50 cm | 1500–2250 | Open rocky area | Amfr | FTEA |
L. duriprati T.C.E.Fr. | Decumbent herb 32 cm | 1500–3600 | Swamp or river banks | Amfr, Dsr, Zwr | SR |
L. erinus L. | Decumbent herb ca. 65 cm | 0–2500 | Wet banks, grassland | Gr, Wsr, Zwr | SR, HS, FTEA |
L. fervens subsp. recurvata (E.Wimm.) Thulin | Erect herb 60 cm | 400–1500 | Marshy areas, Savannah, forest | Amfr, Dsr, S-ddr | SR, FTEA |
L. fervens Thunb. | Erect herb ca. 60 cm | 10–2100 | Grassland, forest and woodland edge, river banks | Amfr, Wsr, Zwr | SR, HS |
L. flaccida subsp. granvikii (T.C.E.Fr.) Thulin | Erect herb 15–60 cm | 1200–3200 | Upland forest edges and on wet marshy edges | Amfr, Wsr, Dsr, Gr | SR, FTEA |
L. giberroa Hemsl. | Erect shrub 10 m | 1200–3050 | Upland forest edges | Amfr |
SR, LR ( |
L. gilgii Engl. | Branched prostrate herb 45 cm | 1500–2500 | Stream banks | Amfr, Zwr | SR, FTEA |
L. goetzei Diels | Erect herb 75 cm | 1000–3000 | Grassy rocky hillside | Amfr, Dsr, Gr, Wsr, Zwr | FTEA |
L. graniticola E.Wimm. | Decumbent herb < 50 cm | 2100–2500 | Rocky slopes | Amfr | SR, FTEA |
L. gregoriana Baker f. | Erect sub shrub 3 m |
3200–4500 |
Erica zone, wet moorland |
A-ar | SR |
L. gregoriana subsp. elgonensis (R.E.Fr. & T.C.E.Fr.) E.B.Knox | Erect subshrub 2 m | 3400–4100 | Swamp or stream banks | A-ar | SR, FTEA |
L. gregoriana subsp. satimae E.B.Knox | Erect subshrub 3 m | 3300–4000 | Wet moorland | A-ar | SR |
L. hartlaubii Buchenau | Procumbent herb 90 cm | 500–1300 | River banks, forest | Amfr | FTEA |
L. heyneana Schult. | Erect herb30 cm | 1000–1800 | Disturbed rocky area | Amfr, Zwr | FTEA |
L. holstii Engl. | Erect/decumbent 60 cm | 900–3500 | Disturbed moorland, rocky and forest areas | A-ar, Amfr, Dsr, Gr, Wsr | SR |
L. inconspicua A.Rich. | Erect herb ca. 20 cm | 1000–2400 | Ditches, woodland | Amfr, Dsr, Wsr, Zwr | SR, FTEA |
L. lindblomii Mildbr. | Prostrate herb ca. 80 cm | 3000–4300 | Swampy or rocky places | A-ar | SR |
L. longisepala Engl. | Erect subshrub 5 m | 750–1500 | Along the streams | Amfr | HS, FTEA |
L. lukwangulensis Engl. | Erect subshrub 10 m | 1700–2500 | Forest edges | Amfr | HS, FTEA |
L. mildbraedii Engl. | Erect subshrub 3.5 m. | 1800–3050 | Upland swamp | Amfr | HS, FTEA |
L. minutula Engl. | Prostrate herb >70 cm | 200–4000 | Moorland, Forest | A-ar, Amfr | SR |
L. molleri Henriques. | Decumbent herb 80 cm | 850–2500 | Upland shady and moist places | Amfr, Wsr, Gr | FTEA |
L. morogoroensis E.B.Knox & Pócs | Erect subshrub 6 m | 700–1400 | Dry woodland, riparian forest | Amfr, Zwr |
LR ( |
L. neumannii T.C.E.Fr. | Decumbent herb ca. 35 cm | 1800–2800 | Bare or rocky ground | Amfr, Gr | SR |
L. ovina E.Wimm. | Erect herb 77 cm | 1800–2500 | Burnt forest | Amfr | HS, FTEA, SR |
L. petiolata Hauman | Erect shrub 5 m | 1900–2100 | Moist forest | Amfr |
FTEA, LR ( |
L. ritabeaniana E.B.Knox | Erect subshrub 6 m | 2000–2250 | Moist forest | Amfr |
LR ( |
L. rubescens De Wild. | Decumbent 60 cm | 700–3000 | Bamboo zone, forest, woodland in wetland banks | Amfr, Zwr | FTEA |
L. sancta Thulin | Erect subshrub 8 m | 1900–2100 | Mist summit forest | Amfr | HS, FTEA |
L. sapinii De Wild. | Erect ca. 35 cm | 400–1050 | Woodland, grassland | Amfr, Wsr, Zwr | FTEA |
L. stricklandiae Gilliland | Erect subshrub 6 m | 1700–2000 | Lowland forest to bamboo | Amfr | HS, FTEA |
L. stuhlmannii Schweinf. ex Engl. | Erect subshrub 10 m | 3000–4000 | Afro-alpine region, moorland | A-ar | HS, FTEA |
L. telekii Schweinf.ex Engl | Erect subshrub 4 m | 3000–5000 | Lower afro-alpine to snow line | A-ar | SR |
L. trullifolia Hemsl. | Decumbent herb > 60 cm | 1000–2750 | Forest margins, rocky areas | Amfr, Zwr | SR, FTEA |
L. trullifolia subsp. minor Thulin | Erect herb 15 ca. 60 cm | 1050–2200 | Rocky outcrop | Amfr, Dsr, S-ddr | SR, FTEA |
L. uliginosa E.Wimm. | Erect 45 cm | 1000–1800 | Rocky forest/ bog | Amfr, Zwr | FTEA |
L. undzungwensis Thulin | Erect shrub 9 m | 1500–2400 | Mist forest, rock outcrop | Amfr |
LR ( |
L. welwitschii Engl. & Diels ex Diels | Erect herb 45 cm | 400–3200 | Wet banks, bogs, swamps | Amfr, Dsr, Gr, Wsr, Zwr, S-ddr | SR, FTEA |
L. wollastonii Baker f. | Erect subshrub 7 m | 3300–4400 | Erica zone, moorland | A-ar | HS, FTEA |
(1) Afro-alpine region. In this study, the afro-alpine region includes the sub-alpine ericaceous zone and the afro-alpine zone. The sub-alpine ericaceous zone ranges from about 3000 m to 3800 m (
Summary for the distribution of lobelias in the seven vegetation regions.
Vegetation region | Altitude (m) | Number of taxa | Number of giant taxa | Number of herbaceous taxa |
---|---|---|---|---|
Afro-alpine | 3000–4900 | 15 | 11 | 4 |
Afro-montane forest | 0–3000 | 41 | 13 | 28 |
Lowland montane forest | 0–1500 | 12 | 3 | 9 |
Upland montane forest | 1500–3000 | 29 | 10 | 19 |
Drier savannah | 10–1000 | 9 | 0 | 9 |
Grassland | 1200–3000 | 9 | 0 | 9 |
Wetter savannah | 0–1250 | 11 | 0 | 11 |
Zambezian woodland | 700–1500 | 18 | 1 | 17 |
Semi-desert and desert | 400–1500 | 4 | 0 | 4 |
(2) Afro-montane forest region. The afro-montane forest region currently occurs in anthropogenically-fragmented patches in East Africa and has an altitudinal range of 0–3000 m (
The highlands of the afro-montane forest region extend from 1500 m to 3000 m. These forests have recently been highly fragmented. They are similar in species composition across the East African countries. Dominant native species from other families found in this region include Olea europaea subsp. africana (Mill.) P.S. Green., Juniperus procera Hockst ex Endl., Prunus africana (Hook.) Kalkman., Oldeania alpina (K. Schum.) Stapleton and Hagenia abyssinica (Faber-Langendoen) J.F.Gmel. However, non-native species have become fully naturalised in disturbed areas for timber production. The species include Grevillea robusta A.Cunn. ex R.Br., Casuarina equisetifolia L., Cupressus lusitanica Lindl. Ex Parl., Pinus patula Schiede & Deppe ex Schltdl., Eucalyptus globulus Labill., Eucalyptus saligna Sm., Corymbia citriodora (Hook.) K.D.Hill & Johnson, Corymbia maculata (Hook.) K.D.Hill & Johnson, Fraxinus pennsylvanica f.colorata B.Boivin, Araucaria cunninghamii Sweet ex Courtois and Acrocarpus fraxinifolius Arn.
The afro-montane forest region above 1600 m is rich in lobelias. Most species at this altitude are herbaceous and include Lobelia gilgii Engl., Lobelia graniticola E.Wimm., Lobelia trullifolia Hemsl., Lobelia uliginosa E.Wimm., Lobelia dissecta M.B.Moss, Lobelia neumannii T.C.E.Fr., Lobelia flaccida subsp. granvikii (T.C.E.Fr.) Thulin, Lobelia molleri Henriques., Lobelia rubescens De Wild., Lobelia heyniana Spreng., L. minutula, Lobelia cymbalarioides Engl., Lobelia duriprati T.C.E.Fr., L. holstii, Lobelia goetzei Diels, Lobelia ovina E.Wimm., Lobelia baumannii Engl., Lobelia fervens Thunb. and Lobelia angolensis Engl. & Diels (Table
The giant lobelias in this zone include Lobelia mildbraedii Engl., Lobelia sancta Thulin, Lobelia stricklandae Gilliland, Lobelia lukwangulensis Engl., Lobelia ritabeaniana E.B.Knox, Lobelia deckenii subsp. incipiens E.B.Knox, Lobelia petiolata Hauman, Lobelia udzungwensis Thulin, L. aberdarica and L. bambuseti (
(3) Drier savannah region. The drier savannah region is found in Kenya, Ethiopia and Somalia, where Senegalia Raf. spp., Vachellia Wight & Arn. spp. and Commiphora Jacq. spp. dominate the area. The region ranges from 10 m to 1000 m (or up to 1500 m in some habitats;
(4) Grassland region. Grassland region is the most common habitat in the EA, and is dominated by alternating grasses with thorny bush-land and thicket. Although habitats in this region are different from others, some lobelias in this region are the same as in the areas of highland, wet and dry savannah and some even from the woodland. However, lobelias in this region are mostly restricted to the wet ground after rainfall (waterlogged grassland and seasonal river banks) and at the edges of wetlands in the marshy areas, streams and river banks, as well as tops of grass hills. The species include L. fervens, L. molleri, L. holstii, L. flaccida subsp. granvikii, L. baumannii, L. goetzei, L. erinus and L. welwitschii (Table
(5) Wetter savannah region. This region is widely distributed in Kenya, Tanzania and Uganda with altitudes from 0 m to 1250 m. Both Combretaceae R.Br., and Fabaceae Lindl. families dominate this region. Lobelias in this region include the herbaceous L. fervens subsp. fervens, L. baumannii, L. goetzei, L. inconspicua, L. molleri, L. holstii, L. flaccida subsp. granvikii, L. sapinii, L. chireensis, L. erinus and L. welwitschii (Table
(6) Zambezian woodland region. This region occurs in the southern part of Tanzania at altitudes ranging from 700 m to 1500 m. It is dominated by members of the family Fabaceae, such as species of the genera Brachystegia Benth., Julbernardia Pellegr., Isoberlinia Craib & Stapf ex Holland and Uapaca Baill. Lobelia inhabits wet deciduous woodland habitats in this region. Herbaceous lobelias include L. fervens subsp. fervens, L. chireensis, L. trullifolia subsp. trullifolia, L. gilgii, L. sapinii, L. duriprati, L. goetzei, L. inconspicua, L. uliginosa, L. rubescens, Lobelia heyneana Schult., L. adnexa, L. cymbalarioides, L. baumannii, L. erinus, L. angolensis and L. welwitschii (Table
(7) Semi-desert and desert region. The hostile climate of this region forms semi-desert and desert vegetations in northern Kenya and southern Ethiopia. This region is characterised by thorny scattered trees and shrubs. Lobelias are distributed in muddy ditches edges and seasonal river banks. However, they are exceedingly rare and only appear in the seasonally-flooded ground or marshy edges of the freshwater wetlands. Species that are distributed in this region include L. fervens subsp. recurvata, L. trullifolia subsp. minor, L. welwitschii and L. chireensis (Table
We employed a map (Fig.
The EA Mountains form altitudinal island-like habitats. Most of these mountains, which are known as sky-islands, are of volcanic origin (
The East African Mountains embrace a wide range of altitudinal habitats and ecosystems, from surrounding environs at the foot of the mountains to the alpine zone (
East African Mountain biomes were differentiated into two major categories, the mountains that reach the alpine (upland) and those without the alpine regions (lowlands and Eastern Arc Mountains). The upland giant lobelias, except L. petiolata, normally have a single aerial stem that is unbranched. The branched L. petiolata inhabits Nyungwe in Rwanda and extends its range to Kahuzi in DR Congo in very wet afro-montane forest region. These species have a clear preference for a wet forest habitat (
The Eastern Arc Mountains (lowlands) form the easternmost blocks of East Africa (
The Eastern Arc Mountains are separated from each other by lowland woodlands and savannah (
Land-use changes associated with deforestation and land degradation are major causes of biodiversity loss in East Africa (
Moreover, the afro-montane forest and its environment are also threatened by invasive plants (
Mountain forests are major water towers, biodiversity hotspots, species evolution refugia, eco-tourism locations, sources of wild foods and centres of plant genetics (
Our results showed that lobelias are distributed in all of the seven vegetation regions in five countries of East Africa. The afro-montane forest region is the richest in species diversity, although it is not the largest by area. The herbaceous type has a preference for the lowland regions, while the giant type has a clear preference for the afro-alpine and afro-montane forest. Future conservation for the genus should consider the habitat preferences of lobelias.
We thank Edwin Kadiori, Josephat Mbogo, Elizabeth Kamande and Ceaser Gitari for fieldwork assistance. This work was supported by the National Natural Science Foundation of China (grant number 31670226) and the Sino-Africa Joint Research Center.
Tables S1–S12
Data type: data statistics
Explanation note: Data statistics for each species.