Peter.Teske@bio.mq.edu.au |
Journal articles | |
2007 |
P R Teske, I Papadopoulos, G I Zardi, C D McQuaid, C L Griffiths, M T Edkins, N P Barker (2007) Implications of life history for genetic structure and migration rates of five southern African coastal invertebrates: planktonic, abbreviated and direct development Marine Biology 152: 697-711 Abstract: The amount of genetic structure in marine
invertebrates is often thought to be negatively correlated
with larval duration. However, larval retention may
increase genetic structure in species with long-lived planktonic
larvae, and rafting provides a means of dispersal for
species that lack a larval dispersal phase. We compared
genetic structure, demographic histories and levels of gene
Xow of regional lineages (in most cases deWned by biogeographic
region) of Wve southern African coastal invertebrates
with three main types of larval development: (1)
dispersal by long-lived planktonic larvae (mudprawn
Upogebia africana and brown mussel Perna perna), (2)
abbreviated larval development (crown crab Hymenosoma
orbiculare) and (3) direct development (estuarine isopod
Exosphaeroma hylecoetes and estuarine cumacean Iphinoe
truncata). We hypothesized that H. orbiculare, having
abbreviated larval development, would employ a strategy
of larval retention, resulting in genetic structure comparable
to that of the direct developers rather than the planktonic
dispersers. However, regional population structure was
signiWcantly lower in all species with planktonic larvae,
including H. orbiculare, than in the direct developers.
Moreover, nested clade analysis identiWed demographic
histories resulting from low levels of gene Xow (isolation
by distance and allopatric fragmentation) in the direct
developers only, and migration rates were signiWcantly
higher in all three species having planktonic larvae than in
the direct developers. We conclude that the amount of
genetic structure within marine biogeographic regions
strongly depends on the presence or absence of free-swimming
larvae. Whether such larvae are primarily exported or
retained, whether they have long or short larval duration,
and whether or not they are capable of active dispersal
seems to have little eVect on connectivity among populations. Notes: Lengthy pdf download!! Get some coffee...
Please see the following website for additional publications on marine phylogeography in southern Africa:
http://www.ru.ac.za/academic/departments/botany_research/peter/
|
P R Teske, P W Froneman, C D McQuaid, N P Barker (2007) Phylogeographic structure of the caridean shrimp Palaemon peringueyi in South Africa: further evidence for intraspecific genetic units associated with marine biogeographic provinces African Journal of Marine Science 29: 253-258 Abstract: Recent genetic studies have shown that most widely
distributed, passively dispersing invertebrates in
southern Africa have regional intraspecific units that
are associated with the three main marine biogeographic
provinces (cool-temperate, warm-temperate
and subtropical). The caridean shrimp Palaemon
peringueyi also occurs in all three provinces, but the
fact that it can disperse both actively and passively (i.e.
larval drifting, adult walking/swimming and potential
adult rafting by means of floating objects) suggests
that the amount of gene flow between regions may be
too high for evolutionary divergence to have taken
place. Samples of P. peringueyi were collected throughout
South Africa and an intraspecific phylogeny was
reconstructed using mitochondrial COI and 16S rRNA
sequences. Three major clades were recovered, which
were broadly associated with the three biogeographic
regions. This suggests that, even though P. peringueyi
can disperse actively, the fact that neither larvae nor
adults are strong swimmers has resulted in genetic
subdivisons comparable to those of passively dispersing
coastal invertebrates in southern Africa. Notes: Please see the following website for additional publications on marine phylogeography in southern Africa:
http://www.ru.ac.za/academic/departments/botany_research/peter/
| |
P R Teske, I Papadopoulos, B K Newman, C D McQuaid, N P Barker (2007) Climate change, genetics or human choice: why were the shells of mankind's earliest ornament larger in the Pleistocene than in the Holocene? PLoS ONE 7: e614 Abstract: The southern African tick shell, Nassarius kraussianus (Dunker, 1846), has been identified as being the earliest
known ornamental object used by human beings. Shell beads dated from ~75,000 years ago (Pleistocene era) were found in
a cave located on South Africa’s south coast. Beads made from N. kraussianus shells have also been found in deposits in this
region dating from the beginning of the Holocene era (~10,000 years ago). These younger shells were significantly smaller,
a phenomenon that has been attributed to a change in human preference. We
investigated two alternative hypotheses explaining the difference in shell size: a) N. kraussianus comprises at least two genetic
lineages that differ in size; b) the difference in shell size is due to phenotypic plasticity and is a function of environmental
conditions. To test these hypotheses, we first reconstructed the species’ phylogeographic history, and second, we measured
the shell sizes of extant individuals throughout South Africa. Although two genetic lineages were identified, the sharing of
haplotypes between these suggests that there is no genetic basis for the size differences. Extant individuals from the cool
temperate west coast had significantly larger shells than populations in the remainder of the country, suggesting that N.
kraussianus grows to a larger size in colder water. The decrease in fossil shell size from Pleistocene
to Holocene was likely due to increased temperatures as a result of climate change at the beginning of the present interglacial
period. We hypothesise that the sizes of N. kraussianus fossil shells can therefore serve as indicators of the climatic conditions
that were prevalent in a particular region at the time when they were deposited. Moreover, N. kraussianus could serve as
a biomonitor to study the impacts of future climate change on coastal biota in southern Africa. Notes: Please see the following website for additional publications on marine phylogeography in southern Africa:
http://www.ru.ac.za/academic/departments/botany_research/peter/
| |
P R Teske, C D McQuaid, N P Barker (2007) Lack of genetic differentiation between four southeast African intertidal limpets: phenotypic plasticity in a single species? Journal of Molluscan Studies 73: 223-228 Abstract: Specimens of four sympatric intertidal limpet species (Siphonaria dayi, S. tenuicostulata, S. anneae and
S. nigerrima ) were collected from four localities on the east coast of South Africa and southern Mozambique.
Their phylogenetic relationships were investigated using sequences of the mitochondrial COI
gene and the intron-containing nuclear ATPSb gene. Two closely related lineages were recovered,
which grouped specimens on the basis of geography rather than morphology. One lineage was associated
with the subtropical coastline of South Africa’s east coast and the other with the tropical coastline
of northeastern South Africa and southern Mozambique. This genetic discontinuity coincides with a
biogeographic boundary located in the vicinity of Cape St Lucia. Combined genetic diversity of the
four species was lower than that of three other southern African congeners, and fell within the range
determined for single southern African marine mollusc species. We suggest that the four limpet
species are in fact different morphotypes of a single species. Notes: Please see the following website for additional publications on marine phylogeography in southern Africa:
http://www.ru.ac.za/academic/departments/botany_research/peter/
| |
P R Teske, J F Lockyear, T Hecht, H Kaiser (2007) Does the endangered Knysna seahorse, Hippocampus capensis, have a preference for aquatic vegetation type, cover or height? African Zoology 42: 23-30 Abstract: The Knysna seahorse, Hippocampus capensis, is an endangered teleost confined to three South
African estuaries. Its abundance within these systems is low and distributions are patchy.
Consequently, monitoring population sizes is labour-intensive. The aim of this study was to
establish if Knynsa seahorses are associated with specific regions within the estuaries, on
which conservation efforts could concentrate. The relationship of Knysna seahorses with
aquatic vegetation was analysed in the Knysna Estuary (the largest of the three estuarine
systems inhabited by H. capensis) to determine whether this species shows a preference for a
particular plant species, vegetation density or vegetation height. Seahorses were associated
with five dominant aquatic plants: Zostera capensis, Caulerpa filiformis, Codium extricatum,
Halophila ovalis and Ruppia cirrhosa. Together, these comprised 96% of the submerged objects
with which seahorses were associated. The relative abundance of plant species changed along
the estuary, but seahorses were present throughout the system, except at the estuary mouth,
which was characterized by low plant densities and strong currents. No significant difference
was found between the proportion of plant species present in a particular region of the estuary
and the proportion of plants that seahorses used as holdfasts. However, when Z. capensis and
C. filiformis were present at the same sites, adult seahorses preferred C. filiformis as holdfast.
Adult seahorse density (individuals/m2) was significantly correlated with percentage vegetation
cover and with holdfast length, but juvenile seahorse density was not. Nonetheless, significantly
more adult and juvenile seahorses were found at sites characterized by high vegetation
cover (>75%) than at sites with lower cover. Our results indicate that although there is some
evidence that Knynsa seahorses prefer certain plant species over others, they are likely to be
encountered anywhere in the estuary where aquatic plants are present. Conservation efforts
in the Knysna Estuary should thus concentrate on such vegetated areas, which comprise
approximately 11% of the total submerged surface area. Notes: More papers on the ecology and evolution of seahorses are available at the following website:
http://www.ru.ac.za/academic/departments/botany_research/peter/
|
Selected :
Delete selected items