MOLECULAR ZOOLOGY LAB
Dr Peter Teske, University of Johannesburg, Auckland Park 2006, Johannesburg, South Africa; Email: email@example.com
This recently founded research group uses genetic tools to study aquatic animals, with a specific focus on the marine biogeography of southern Africa.
Marine phylogeography and cryptic speciation. The number of marine invertebrates in southern Africa and Australia is considerably larger than previously thought. Using genetic data, we have shown that many marine invertebrates are species complexes comprised of numerous species that are difficult to distinguish on the basis of morphological data (PDF). Phylogeographic breaks between sister taxa are often linked to the boundaries between marine biogeographic provinces (PDF), and adaptation to the environmental conditions prevalent within each province is an important factor maintaining the distinct distributions of cryptic sister taxa (PDF). Marine phylogeographic breaks in southern Africa have likely arisen in the absence of complete dispersal barriers. On the basis of molecular dating and fossil data, we hypothesise that their evolution was instead linked to climate change and resulting shifts in the geographic position of biogeographic provinces. For example, during warm climatic phases, the species associated with the subtropical province underwent a range expansion, and the ranges of most species contracted again during the subsequent cold phase. However, regional populations of some species managed to persist in what was now unfavorable temperate habitat by undergoing a selective sweep that effectively put them on the path to speciation (PDF, PDF).
Seahorse evolution and ecology. Seahorses are the only fishes that permanently swim with an upright posture, and even though they are exceptionally poor swimmers, they have managed to colonise tropical and temperate seas throughout the world. See the publication list on the left for papers on seahorse evolution and biogeography, as well as ecological studies on South Africa's endangered Knysna seahorse (PDF). We show that seahorses likely evolved in the Indo-West Pacific (PDF), provide an estimate for when this occurred (PDF) and demonstrate how they gradually established a circumglobal distribution (PDF).
Connectivity between Marine Protected Areas. MPAs are considered to successfully protect South Africa's overfished sparid (seabream) stocks. In many species, dispersal takes place by means of planktonic larvae (which cannot be tagged), so genetic work using highly variable markers is required to determine whether MPAs are adequately spaced to ensure gene flow between different reserves, and whether there is spillover into exploited areas (PDF).
Macrobenthos in South African estuaries. The idea that benthic macroinvertebrates in estuaries are arranged along a salinity gradient is incorrect, although it often seems that way. Most South African systems are dominated by estuarine endemics (rather than marine or oligohaline species), whose wide tolerance range of ~5-55 ppt. makes their distributions fairly independent of salinity. Instead, species are either associated with a sand zone (in the lower reaches) and a mud zone (in the middle and upper reaches). This basic pattern is similar in all estuary types. It is particularly well defined in intermittently closed estuaries, which tend to have the same salinity almost along their entire length and are inhabited almost exclusively by estuarine endemics. Freshwater-deprived open estuaries (which often have a reversed salinity gradient) have an additional faunal component that is of marine origin. Interestingly, these marine species are restricted to the sand zone, even though salinities in the mud zone are often close to that of seawater, and the mud zone community is usually present in its pure form. In river-dominated open systems (which are rare in arid countries like South Africa), low-salinity species can become reasonably abundant in the upper reaches. The common practise of using distance from the estuary mouth as a proxy for long-term salinity is of course highly questionable when studying estuaries in arid countries (PDF).
The vast majority of studies on marine invertebrates have used mitochondrial DNA sequence data, in particular COI. We have developed several exon-primed/intron crossing primers for amplifying nuclear introns in important invertebrate groups, including decapod crustaceans, false limpets and Stolidobranchia ascidians. Introns are a useful addition to mitochondrial DNA because they a) are inherited biparentally and can thus be used to study hybridisation/reproductive isolation b) are crucial to improve the accuracy of molecular dating because of coalescent stochasticity and c) are a useful addition to the limited number of markers available for phylogenetic studies of many marine invertebrate groups, incl. COI, 12S, 16S, 18S, 28S, ITS and Histone H3.
Try the following primers for amplifying the...
a) ANT (Adenine Nucleotide Transporter, also known as ADP/ATP translocator) gene in decapod crustaceans (e.g. Penaeus, Scylla, Jasus):
DecapANT-F (forward primer): 5'-CCTCTTGAYTTCGCKCGAAC-3'
DecapANT-R (reverse primer): 5'-TCATCATGCGCCTACGCAC-3'
(Teske & Beheregaray 2009, Mol Ecol Res, PDF)
b) ANT gene in Stolidobranchia ascidians (e.g. Pyura, Botryllus, Styela)(Teske et al. 2011 PDF, Jarman et al. 2002)
c) ATPSb gene in the Basommatophora limpets (e.g. Siphonaria)
(Teske et al. 2008, J Moll Stud 73:223-228 PDF / Jarman et al. 2002)
Also potentially useful mtDNA primers:
COI primers designed specifically for crustaceans:
DecapCOI-R: 5'-AATTAAAATRTAWACTTCTGG-3′ (for decapods)
PeracCOI-R: 5'-TATWCCTACWGTRAATATATGATG-3' (for peracarids)
(Teske et al. 2007, Mar Biol, PDF)
PeracCOI-R also works for decapods, particularly when nothing else works
Control region primers for syngnathids (seahorses, pipefishes and probably others):
HCAL2 (forward primer): 5'-CACACTTTCATCGACGCTT-3'
HCAH2 (reverse primer): 5'-TCTTCAGTGTTATGCTTTA-3'
(Teske et al. 2003, Mol Ecol 12:1703-1715, PDF)
Control region primers for the seabream genus Chrysoblephus:
ChrysoCytbF (forward primer): 5'-GCAGCAGCAYTAGCAGAGAAC-3'
Sparid12SR1 (reverse primer): 5'-TGCTSRCGGRGGTTTTTAGGG-3'
(Teske et al. 2010, Mar Biol, PDF)
Also work in other sparids, including Lithognathus lithognathus (steenbras), Pachymetopon grande (bronze bream) and Cymatoceps nasutus (poenskop) (G. Gouws, SAIAB )
For microsatellite libraries, please see the following articles:
Galbusera PHA, Gillemot SA, Jouk P, Teske PR, Hellemans B, Volckaert FAMJ (2007)
Isolation of microsatellite markers for the endangered Knysna seahorse Hippocampus capensis and their use in the detection of a genetic bottleneck. Molecular Ecology Notes 7:638-640. PDF
(these cross-amplify in all sorts of other seahorses and may also work in other syngnathids)
Teske PR, Forget FRG, Cowley PD, Beheregaray LB (2009)
Microsatellite markers for the roman, Chrysoblephus laticeps (Teleostei: Sparidae), an overexploited seabream from South Africa. Molecular Ecology Resources 9:1162-1164. PDF
Rourke ML, Teske PR, Attard CRM, Gilligan DM, Beheregaray LB (2010)
Isolation and characterisation of microsatellite loci in the Australian freshwater catfish (Tandanus tandanus). Conservation Genetics Resources.