Discovery of populations endemic to a marine biogeographical transition zone

Tirupathi Rao Golla,Leishe Pieterse,Candice M Jooste,Peter R Teske

doi:10.1111/ddi.13162

Abstract

AbstractAimBiogeographical transition zones are areas of overlap between the faunas of adjacent biogeographical entities. Particularly the well‐defined transition zones along linear coastlines are interesting natural laboratories to study dispersal and incipient speciation. Few studies have explored whether marine biogeographical transition zones harbour biodiversity that is distinct from that of the biogeographical entities they separate. The Wild Coast in eastern South Africa is a poorly studied transition zone between the region's warm‐temperate and subtropical faunas, and is generally considered to be an area of faunal overlap.LocationThe South African portion of the Western Indian Ocean.MethodsSequences of the DNA barcoding marker COI were generated from 306 estuarine sandprawns (Kraussillichirus kraussi) collected at 13 sites. Genetic structure and evolutionary history were assessed using a haplotype network and a Bayesian discrete phylogeographic analysis.ResultTwo populations were identified whose ranges are centred on the Wild Coast, a rare one in the northern portion and a more common one in the central and southern portion of this biogeographical transition zone. These populations are not closely related to each other, but descend from subtropical and warm‐temperate sister populations, respectively. Although genetic distances between populations were low, they exceeded within‐population distances, indicating the presence of a "barcoding gap."ConclusionsThis is the first study to indicate that the Wild Coast marine biogeographical transition zone is not merely an area of faunal overlap, and one of very few studies to have discovered genetically unique populations within a marine biogeographical transition zone. The Wild Coast may harbour additional unique biodiversity that remains to be discovered, including rare species that require protection. More research is required to understand how this environmentally dynamic marine biogeographical transition zone differs from the adjacent biogeographical provinces.

Highlights

IntroductionBiogeographical transition zones are areas located between the distribution ranges of two or more independently-evolving biotic entities (e.g. biogeographical regions, provinces, biomes or communities), whose intermediate environmental conditions allow overlap of faunal elements, but prevent the extension of their ranges into each other (Ferro & Morrone, 2014)
Biogeographical transition zones are areas located between the distribution ranges of two or more independently-evolving biotic entities, whose intermediate environmental conditions allow overlap of faunal elements, but prevent the extension of their ranges into each other (Ferro & Morrone, 2014)
The present study explored the issue of endemicity in a more extensive marine biogeographical transition zone, the Wild Coast in eastern South Africa

Summary

Introduction

Biogeographical transition zones are areas located between the distribution ranges of two or more independently-evolving biotic entities (e.g. biogeographical regions, provinces, biomes or communities), whose intermediate environmental conditions allow overlap of faunal elements, but prevent the extension of their ranges into each other (Ferro & Morrone, 2014) They may be found in locations with either strong environmental gradients or ‘ribbons’ of relatively unsuitable habitats (Glor & Warren, 2011), and often have high biodiversity because of the co-occurrence of species from the adjacent biogeographical entities (Morrone, 2006; Ortega & Arita, 1998; Silva-Pereira et al, 2020). This suggests that such widespread species comprise multiple unique, regional populations that are each on their own evolutionary trajectory, making biogeographical transition zones interesting areas for exploring incipient speciation and its environmental drivers (Dawson, 2005; Sommer et al, 2014; Teske et al, 2019)

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