Laevicaulis natalensis ( Krauss, 1848 )

Rapalai, Boikhutso Lerato, 2024, An annotated checklist of molluscs recorded from Botswana, Indago: Investigating nature and humanity in Africa (Oxford, England) 41 (10), pp. 15-44 : 31-32

63. Laevicaulis natalensis ( Krauss, 1848)

Distribution and year: Francistown 2020 ( GBIF 2023 b); Ngwaketse North 2023 ( GBIF 2023 b).

Geographic range: Botswana, Mozambique, South Africa, Zimbabwe.

Habitat: Terrestrial.

Notes: This is a common species in Southern Africa, found in a variety of habitats such as the forest, bushveld and woodland ( Herbert & Kilburn 2004).

Type locality: KwaZulu-Natal, South Africa ( Krauss 1848) .

Source: GBIF (2023 b).

Conservation status: Not Evaluated.

IUCN Red Data Listing

Out of the species recorded from Botswana, 52.4 % are listed as ‘Least Concern’, 41.3 % as ‘Not Evaluated’,

while 6.3% are considered ‘Data Deficient’ in the IUCN Red Data Listing ( Fig. 2 ).

Sampling effort over the years

Species comprising this checklist were collected and/or observed from 1854 to 2023. Less than five species were recorded from 1854 to the early 1960s ( Fig. 3). Following the Harvard-Smithsonian-Transvaal Museum Kalahari expedition in 1961 and publications by van Bruggen (1963; 1966 a), there was a slight increase to seven species around the early 1960s, with further growth to 14 species in the mid- 1960s. The number of recorded species abruptly declined in the late 1960s and remained low during the 1970s until dedicated collecting of freshwater molluscs by C.C. Appleton, S. Bethune and B.A. Curtis in 1983–1986 contributed to 19 species in 1984 and 15 species in 1986. The 1990s saw a decline of documented molluscs to less than ten species. A multilateral AquaRAP expedition to the Okavango Delta in 2000 ( Ashton et al. 2003) prompted the instantaneous addition of 26 species ( Appleton et al. 2003). The beginning of the 21 st century witnessed a record of less than ten (often less than five) species annually.

Species richness per locality and ecoregion

The Okavango Delta harbours 31 species, the highest figure per locality, followed by the Chobe–Linyanti– Kwando river-system with 25 species ( Fig. 4 ). The Thamalakane and Boro rivers host 13 species each. Lake Ngami, Boteti River, Aha Hills, and Limpopo River yield between 6–10 species. All the other localities produce less than five species ( Fig. 4 ). In terms of the ecoregions, the Zambezi Flooded Grasslands record the highest number of freshwater mollusc species, while the Kalahari Xeric Savanna biome has the lowest number of them ( Fig. 5 ). For terrestrial molluscs, the Kalahari Acacia Woodlands record the richest diversity, whereas the Zambezian Mopane Woodlands host the lowest number of species ( Fig. 5 ).

Introduced species

Order Stylommatophora Schmidt, 1855

Family Helicidae Rafinesque, 1815

Common name: Typical snails or helix garden snails

Figures

Figure 2: The percentage of the IUCN Red Listings for mollusc species recorded in Botswana from 1854–2023: green – Least Concern, blue – Not Evaluated, red – Data Deficient.

Figure 4: Botswana localities where mollusc species were collected and/or observed. The size of each circle is proportional to the number of species collected and/or observed in that locality. The colours correspond to the seven ecoregions of Botswana (Fig. 1).

Figure 5: The number of mollusc species recorded per each ecoregion of Botswana.