Molecular phylogeny and biogeography of the Afrotropical freshwater crab fauna
Date
2014-04
Authors
Phiri, Ethel Emmarantia
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : Stellenbosch University
Abstract
ENGLISH ABSTRACT: Freshwater organisms, such as crabs (Crustacea: Decapoda: Brachyura), are useful in
studies examining inland historical biogeographic patterns and speciation because they are
isolated to specific drainage systems, which often serve as barriers to gene flow. The
Afrotropical freshwater crab fauna (Potamonautidae) present ideal organisms for
investigating hypothesis relating to evolutionary histories because they occur on continental
Africa (sub-Sahara) and islands. However, there is a great deal of undiscovered freshwater
crab diversity, especially with the prevalence of undiscovered cryptic lineages, which are
poorly studied among freshwater crabs, leading to uncertain regional diversity.
In this research, multiple genetic (mt- and nuDNA) markers were used to infer the
phylogenetic relationships and the biogeographical histories of the Afrotropical freshwater
crab superfamily, Potamonautidae. Divergence time estimations were used to infer
biogeographic histories, to ascertain whether speciation could be linked to past geologic and /
or climatic events.
Two widely distributed Potamonautes species complexes were targeted for the
investigation of regional cryptic species diversity. In Chapter 2, the intraspecific phylogenetic
variability within Potamonautes perlatus sensu lato occurring on the Cape Fold Mountain
range (South Africa) was examined, with sampling localities occurring in western- and
southern flowing drainages. Previous research suggested possible cryptic speciation within
this species complex; however, no tangible inferences could be made because of analytical
constraints. Two major clades were recovered: one corresponding to western flowing
drainages and another to southern flowing drainages. Moreover, three cryptic lineages were
recovered: P. perlatus sensu stricto, restricted to western flowing drainages, and two
geographically discrete novel cryptic lineages from the southern flowing drainages, described
as P. barbarai sp. nov and P. barnardi sp. nov., with divergence (±2.61 Mya) linked to
Pleistocene climatic events.
Subsequent to the recovery of the two novel lineages from the Cape Fold Mountain
range, the Pleistocene climatic events.
Subsequent to the recovery of the two novel lineages from the Cape Fold Mountain
range, the revision of the P. clarus / P. depressus species complex from the Tugela and
uMkomazi drainages (Drakensberg Mountain range, South Africa) was conducted. This
species complex was previously found to comprise at least five cryptic lineages (Chapter 3).
A coalescent multilocus (three mt- and three nuDNA) Bayesian species delimitation method
was used, and an additional three cryptic lineages were recovered, bringing the total to eight species (two already described as P. clarus and P. depressus), with divergence having
occurred approximately 10.3 Mya.
Following the recent discovery of novel freshwater crab lineages in the mountainous
areas of Mozambique and Malawi, a sampling trip to the Zimbabwean Highlands was
undertaken, where a novel freshwater crab species was discovered and described as P.
mutareensis, highlighting the need to sample high-lying regions (Chapter 4). Furthermore,
two additional novel lineages from Mozambique (P. bellarussus sp. nov.) and the
Mpumalanga Province in South Africa (P. flavusjo sp. nov) were described (Chapter 5).
In Chapter 6, increased taxon sampling, with additional specimens acquired from
various museums and personal collections was used to obtain a better resolution of the
phylogeny of the Afrotropical Potamonautidae and to infer the ancestral affinities of the two
sub-families, Deckeniinae and Potamonautinae. The Potamonautidae were found to have
speciated eastward from West Africa, with a late Cretaceous divergence (±107 – 96.04 Mya).
The Potamonautinae originated in West Africa (three genera), while the paraphyletic
Potamonautes and Platythelphusa had East African affinities. Potamonautes was not
monophyletic, comprising several fragmented geographic clades, which may suggest that this
genus requires revision. Nevertheless, the overall speciation within the Potamonautidae
reflects past geological and climatic events, such as rifting and uplift episodes and the
contraction of forests, which occurred from the Tertiary onwards.
Description
Thesis (PhD)--Stellenbosch University, 2014.
Keywords
Freshwater crabs -- Phylogeny, Freshwater crabs -- Biogeography, UCTD, Theses -- Zoology, Dissertations -- Zoology