Land snail biogeography and endemism in south-eastern Africa: Implications for the Maputaland-Pondoland-Albany biodiversity hotspot.

Sandun J Perera,David G Herbert,Şerban Procheş,Syd Ramdhani,Geerat J Vermeij

doi:10.1371/journal.pone.0248040

Sandun J Perera, David G Herbert + Show 3 more

Open Access

https://doi.org/10.1371/journal.pone.0248040

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Abstract

Invertebrates in general have long been underrepresented in studies on biodiversity, biogeography and conservation. Boundaries of biodiversity hotspots are often delimited intuitively based on floristic endemism and have seldom been empirically tested using actual species distributions, and especially invertebrates. Here we analyse the zoogeography of terrestrial malacofauna from south-eastern Africa (SEA), proposing the first mollusc-based numerical regionalisation for the area. We also discuss patterns and centres of land snail endemism, thence assessing the importance and the delimitation of the Maputaland-Pondoland-Albany (MPA) biodiversity hotspot for their conservation. An incidence matrix compiled for relatively well-collected lineages of land snails and slugs (73 taxa in twelve genera) in 40 a priori operational geographic units was subjected to (a) phenetic agglomerative hierarchical clustering using unweighted pair-group method with arithmetic means (UPGMA), (b) parsimony analysis of endemicity (PAE) and biotic element analysis (BEA). Fulfilling the primary objective of our study, the UPGMA dendrogram provided a hierarchical regionalisation and identified five centres of molluscan endemism for SEA, while the PAE confirmed six areas of endemism, also supported by the BEA. The regionalisation recovers a zoogeographic province similar to the MPA hotspot, but with a conspicuous westward extension into Knysna (towards the Cape). The MPA province, centres and areas of endemism, biotic elements as well as the spatial patterns of species richness and endemism, support the MPA hotspot, but suggest further extensions resulting in a greater MPA region of land snail endemism (also with a northward extension into sky islands—Soutpansberg and Wolkberg), similar to that noted for vertebrates. The greater MPA region provides a more robustly defined region of conservation concern, with centres of endemism serving as local conservation priorities.

Highlights

Terrestrial molluscs (Mollusca: Gastropoda; hereafter land snails) with a global species richness estimated at over 25,000 [1, 2] are not distributed evenly across the globe
The parsimony analysis of endemicity (PAE) area cladogram did not show hierarchical structuring so we further tested our Areas of endemism (AOEs) for consensus and congruency with those recovered from a biotic element analysis (BEA)
The first ever numerical regionalisation for land snails in south-eastern Africa is presented in Fig 2 and Table 1

Summary

Introduction

Terrestrial molluscs (Mollusca: Gastropoda; hereafter land snails) with a global species richness estimated at over 25,000 [1, 2] are not distributed evenly across the globe. With high levels of diversity and endemism, land snails make an excellent indicator group to start exploring the invertebrate zoogeography of south-eastern Africa (SEA). We numerically analyse the zoogeography of the terrestrial malacofauna in SEA for the first time, assessing the importance and the delimitation of the MPA biodiversity hotspot for land snail conservation. This is achieved through numerical biogeographical analyses and mapping of species richness and endemism patterns followed by comparison of the results with the current boundary of the MPA hotspot. Land snail endemism in the Maputaland-Pondoland-Albany biodiversity hotspot sought from two alternative approaches, a parsimony analysis of endemicity and a biotic element analysis

Materials and methods

Bushveld-Mpumalanga Escarpment

Discussion

Units Method