Diversity and Zoogeography of South African Bryozoa

Abstract

The taxonomic history of South African bryozoans is fragmented and outdated, with the majority of published works in the 20th Century. Sampling gaps exist in deep-sea regions and parts of the coastline, while existing collections within museums remain undetermined due to scarcity of specialist taxonomists. This project forms part of a larger project aimed at updating marine invertebrate biodiversity in South Africa. Outcomes of this project include updating bryozoan biodiversity by identifying species from existing collections housed in natural history museums (e.g., Iziko South African Museum, Cape Town and Natural History Museum, London), and analysing current regional bryozoan biogeographical and depth-related species richness patterns. The biogeography and richness of bryozoan species around South Africa was investigated using published distribution records from the literature and museum catalogues as well as examining un-worked bryozoan material from Iziko South African Museum. A total of 368 species of bryozoans were recorded, including twelve new species (Favosipora epiphyta sp. nov., Chaperiopsis (Chaperiopsis) yinca sp. nov., Aspidostoma staghornea sp. nov., Micropora erecta sp. nov., Trypostega infantaensis sp. nov., Khulisa ukhololo sp. nov., Adeonella assegai sp. nov., Celleporaria umuzi sp. nov., Hippomonavella lingulatus sp. nov., Microporella lezinyosi sp. nov., Phidolopora cyclops sp. nov. and Reteporella ilala sp. nov.) and 70 unidentified species. Distribution data for 286 valid species were separated by depth zones (shallow waters, subphotic zone, shelf edge, bathyal zone and abyss) and four biogeographic regions are recognised a priori around South Africa, namely the west, south, southeast and east coasts. This study revealed that there is a clear biogeographic structure to regional bryozoan fauna of South Africa. Species richness and endemism appear lowest on the west coast (104 species) and highest on the south coast (174 species), while local peaks are observed in the Cape Peninsula/False Bay area, East London, Durban and St. Lucia, which coincide with distinct genetic lineages for some marine taxa (e.g. octocorals, chitons, echinoderms, fishes, seaweeds). Although, the faunal break in Durban does not represent a peak in species richness in this study, but rather very low bryozoan richness, highlighting the undersampled areas north of Durban. The northward-flowing Benguela Current and strong upwelling centres may influence the low diversity on the west coast. On the south coast, the high diversity may be attributed to the Agulhas Current that can carry larvae southwards and eastward-flowing counter currents produce great variability in bryozoan communities in this region. Within any biogeographic region, bryozoan diversity was higher in shallower (< 500 m) than deeper waters, which may be attributed to sampling effort and heterogeneity (e.g. variable substrate and wave action) in shallower waters. Keywords: Bryozoa, distribution patterns, gradients, species richness, South Africa