Species assemblages and community structure of adult caddisflies along a headwater stream in southeastern Ghana (Insecta: Trichoptera)

Abstract

Adult caddisflies were collected at 12 sites along a 5 km stretch of a forested headwater stream in southeastern Ghana in March and November 1993 and the catches are related to environmental variables. Some 34,000 specimens, belonging to 178 morphospecies in 43 genera and 11 families, were caught with Malaise traps and light traps. Many species demonstrate differences between sampling method, seasonal occurrence, and sex-ratios, with the light trap in the second wet sunny season (November) being most efficient with respect to the diversity of the catches. A Moran index analysis for global structures indicates a major transition in the fauna from the ravine with waterfalls to the forest, and secondly, a gradient through the forest. A Geary index analysis for local structures indicates further faunal turnovers in the lower reaches of the stream. Species-environment relationships were analyzed through correspondence analysis and co-inertia analysis, allowing ordination of both species and the environment into three zones. The first co-inertia axis reveals a transition between the waterfalls in the open ravine (sites 1-3), and the stream through the riverine forest (sites 4-12), while the second co-inertia axis reveals a gradient from the lotic stream in the moist semi-deciduous forest (sites 4-8) to more lentic stretches of the stream in a gradually more depleted forest (sites 9-12). The most important environmental factors related to the species transition are: riparian moss growth (r ¼ 0.94), leaves in the stream substratum (r ¼ 0.91), forest type (r ¼ 0.90), hygropetric surfaces (r ¼ 0.88), bedrock (r ¼ 0.87), lotic [riffle] (r ¼ 0.85) and lentic [pool] (r ¼ 0.85) stretches. The most important environmental factors related to the species gradient are: lotic [riffle] stretches (r ¼ 0.92), gravel (r ¼ 0.88) and leaves (r ¼ 0.85) in the stream substratum, forest type (r ¼ 0.81), and agricultural use (r ¼ 0.76). Three clusters representing three major environmental zones (zone I, II and III) along the stream are identified by projecting the average species positions on the co-inertia plane. By analyzing the Malaise trap samples significant indicator values are found for 29 species in zone I, 16 species in zone II, and 18 species in zone III. By analyzing the light trap samples significant indicator values are found for 17 species in zone I, 57 species in zone II, and 38 species in zone III. The high diversity of caddisflies in the sanctuary might be reflected both in the geological and climatological history of West Africa, as well as in the recognition of three major environmental zones, and the clean water with high diversity of stream microhabitats favorable for Trichoptera larvae. The closed forest seems to play an important role for the Trichoptera community, and the study demonstrates the importance of protecting forested headwater streams in order to maintain a sustainable aquatic biodiversity in tropical Africa.

Eleven new species of Sericostomatoidea from Madagascar (Trichoptera: Helicopsychidae, Petrothrincidae, Sericostomatidae)

“…The Trichoptera fauna of Madagascar, with 79 species recorded (Morse 1999, Johanson 2002, Malm & Johanson 2005 is relatively rich compared to many regions of mainland Africa. In species richness it is surpassed only by the (political) region of South Africa for which nearly 160 species are recorded (Moor 2000), and Ghana with nearly 180 species, of which most are still undescribed (Kjaerandsen 2005). With few exceptions, descriptions of Trichoptera from Madagascar generally have been based on only one or very few individuals, suggestive of very low population densities.…”

New species of the genus Chimarra Stephens from Africa (Trichoptera, Philopotamidae) and characterization of the African groups and subgroups of the genus

“…The Kakum National Park was visited in the autumn of 1994, and we collected mainly near the main entrance. In the Agumatsa Wildlife Sanctuary caddis flies were collected at 12 sites along a 5 km stretch of the Agumatsa-Nubui headwater stream in spring and autumn 1993 ( Kjærandsen 2005 ). In northern Ghana we collected at the Black Volta and Oti rivers in 1991 to 1993.…”

“…Most of the material treated here is from a study of the caddisfly community along a headwater stream in the Agumatsa Wildlife Sanctuary in the Volta Region, situated in the transition zone in the eastern part of Ghana ( Andersen and Kjærandsen 2001 ; Kjærandsen 2005 ). The sanctuary lies in the southwestern part of the Togo Mountains where it embraces a ravine-riverine forest valley with rather steep sides.…”

First record of Macrostemum alienum Ulmer 1907 (Trichoptera: Hydropsychidae: Macronematinae) from Ile-Ife, Southwestern Nigeria, West Africa

“…However, there have been a number of recent reports from West Africa (Marlier 1978, Statzner 1984, Statzner & Gibon 1984, Statzner et al 1985, 1987Gibon et al 1994, Kjaerandsen & Andersen1997, Andersen & Kjaerandsen 2001), but they are from just a few countries in the sub-region. Therefore, as pointed out in Andersen & Kjaerandsen (2001) and Kjaerandsen (2005), it is evident that the hydropsychid caddisfly fauna of the rest of the West-African sub-region is not completely known. Furthermore, many described species also need redescription to allow for clear, precise recognition (Kjaerandsen 2005).…”

“…Therefore, as pointed out in Andersen & Kjaerandsen (2001) and Kjaerandsen (2005), it is evident that the hydropsychid caddisfly fauna of the rest of the West-African sub-region is not completely known. Furthermore, many described species also need redescription to allow for clear, precise recognition (Kjaerandsen 2005). For example, there is a dearth of information pertaining to the caddisfly fauna in Nigeria compared to those in other West African countries, such as Ghana (Gibbs 1973, Kjaerandsen & Andersen 1997 and Ivory Coast (Statzner 1982(Statzner , 1984, where extensive studies have been carried out.…”