Gavin Gouws

Evolutionary Drivers of Diversification and Distribution of a Southern Temperate Stream Fish Assemblage: Testing the Role of Historical Isolation and Spatial Range Expansion

This study used phylogenetic analyses of mitochondrial cytochrome b sequences to investigate genetic diversity within three broadly co-distributed freshwater fish genera (Galaxias, Pseudobarbus and Sandelia) to shed some light on the processes that promoted lineage diversification and shaped geographical distribution patterns. A total of 205 sequences of Galaxias, 177 sequences of Pseudobarbus and 98 sequences of Sandelia from 146 localities across nine river systems in the south-western Cape Floristic Region (South Africa) were used. The data were analysed using phylogenetic and haplotype network methods and divergence times for the clades retrieved were estimated using *BEAST. Nine extremely divergent (3.5–25.3%) lineages were found within Galaxias. Similarly, deep phylogeographic divergence was evident within Pseudobarbus, with four markedly distinct (3.8–10.0%) phylogroups identified. Sandelia had two deeply divergent (5.5–5.9%) lineages, but seven minor lineages with strong geographical congruence were also identified. The Miocene-Pliocene major sea-level transgression and the resultant isolation of populations in upland refugia appear to have driven widespread allopatric divergence within the three genera. Subsequent coalescence of rivers during the Pleistocene major sea-level regression as well as intermittent drainage connections during wet periods are proposed to have facilitated range expansion of lineages that currently occur across isolated river systems. The high degree of genetic differentiation recovered from the present and previous studies suggest that freshwater fish diversity within the south-western CFR may be vastly underestimated, and taxonomic revisions are required.

A new goatfish species of the genus Upeneus (Mullidae) based on molecular and morphological screening and subsequent taxonomic analysis

Abstract A new goatfish, Upeneus heemstra sp. nov. (Mullidae), from the Western Indian Ocean and SE India is described from initial DNA barcoding and quantitative morphological screening, followed by a taxonomic analysis featuring the comparison of 56 meristic, morphometric and colour characters compiled from 340 specimens of 10 phenotypically similar species. The new species differs clearly from U. oligospilus (Persian Gulf), U. tragula (Eastern Indian Ocean and West Pacific) and U. niebuhri – resurrected here – from the Gulf of Suez (Red Sea) in the combination of the following characters: caudal peduncle, head, snout, postorbital, barbel and caudal-fin length, anal-fin and second dorsal-fin height, and the number of oblique bars on the caudal fin. These four species can be distinguished from the six other species of the so-called tragula group primarily by colour pattern and appear to represent a distinct ‘dark-freckled’ species complex. An updated identification key for the tragula species group is provided and remarks on size-related and population differences are made.

Description of a new species of Potamonautes MacLeay, 1838, from the iSimangaliso Wetland Park, South Africa.

Abstract A new species of freshwater crab, Potamonautes isimangaliso sp. n., is described from the western shores of False Bay, Hluhluwe, within the iSimangaliso Wetland Park, South Africa. While bearing a superficial resemblance to Potamonautes lividus, the new species has been found to be genetically distinct, diverging from the former by 7.4–7.8% in mtDNA. Potamonautes isimangaliso most closely resembles Potamonautes lividus, but is distinguished by a unique suite of carapace characters, colouration, and size. The new species also lives in close association with oxygen-poor, fresh ephemeral pans, while the habitat of Potamonautes lividus is well above the surface water line of the closest water body. An updated identification key for the Potamonautes species of South Africa is provided.

Molecular evidence of distinct evolutionary units in the sandhopper Talorchestia capensis (Amphipoda, Talitridae) along South African coasts

Marine geographical and ecological barriers often reflect intraspecific genetic discontinuities among populations which may experience different selective pressures and undergo evolutionary divergence. While the phylogeography of marine intertidal invertebrates across the Atlantic/Indian Ocean transition received more attention, the population genetic structures of supralittoral direct developers across such transition area have been poorly investigated. Sandhoppers are supralittoral invertebrates characterised by a direct developmental mode (low dispersal ability), and Talorchestia capensis (Amphipoda, Talitridae) represents the most abundant species of sandhoppers along the South African coasts. To define population structure of T. capensis, we used a mitochondrial marker (the cytochrome oxidase subunit I gene, COX1). T. capensis showed a clean population structure with three main haplogroups genetically well separated, although this separation is not perfectly in line with geographical boundaries described for this area. The presence of separate evolutionary significant units is also confirmed by the shape of mismatch distribution, as well as the p distance values among groups. The overall results confirm the importance of mtDNA to retrieve information on the evolutionary history of species. This study suggests the evidence of a complex-species for this sandhoppers, which have never been considered before, providing fundamental basis for further studies.

Crustacean Issues 19: Phylogeography and population genetics in crustacea

Tintinnids represent a group of ciliates belonging to the subclass Choreotrichida. The choreotrichids are characterized by a row of radially oriented ciliary membranelles that encircle the oral opening situated at the anterior end of the cell. The membranelles serve for motility as well as for feeding; otherwise, the ciliature is relatively reduced. The cells are roughly radially symmetric and the organisms typically lead a planktonic life. What especially characterizes the tintinnids is that the cell is housed in a vase-shaped or cylindrical lorica; this may be hyaline consisting of a transparent proteinaceous material or it may be made up of agglutinated fine mineral particles or of particles of biogenic material such as diatom frustules. The cell is attached to the lorica by the cell’s posterior contractile end. The tintinnids comprise a species-rich group: about a thousand species have been named. The vast majority of the species occur in marine plankton, but a few have adapted to life in freshwater (the freshwater species are largely ignored in the book). Historically, it is a well-studied group of organisms. The popularity of tintinnids was due to the lorica allowing easy preservation of samples (in contrast to most other protozoans) on, for example, oceanographic cruises, and in the past lorica morphology was almost the only basis for tintinnid taxonomy and for species descriptions. Lorica morphology, however, has more recently been shown to provide little information on phylogeny. Culturing of different species has also shown that some of them are polymorphic with respect to lorica structure because different types occur during different stages of the cell cycle and environmental factors affect lorica morphology, and so examples of synonymous species have been revealed and the estimated number of tintinnid species may be inflated. This book is a comprehensive and up-to date account of what is known about tintinnids. Ten chapters authored by altogether 16 authors cover the following aspects: morphology, life cycles and cyst formation, systematics and evolution, ecophysiological aspects (including motile behaviour, feeding mechanisms, food preferences, and bioenergetics), enemies of tintinnids (in the form of predators and parasites), fossil tintinnids, role of tintinnids in plankton communities, and distribution patterns of species in the world oceans. Different tintinnid biota are characteristic for warmer and for colder waters as well as for neritic versus oceanic waters. Tintinnids are unusual among unicellular eukaryotes in that they may form recognizable fossils due to their lorica. Molecular evidence suggests that the tintinnids originated during the late Precambrian; putative tintinnid fossils have been recorded from Palaeozoic deposits, but the earliest bona fide tintinnid fossils derive from the Jurassic. This is a good book. The individual chapters are well-written and authoritative. Together, they cover all aspects of tinitinnid biology and several chapters emphasize functional aspects. The book is well illustrated and it appears attractive (as are the organisms that the book describes), and the reference list is comprehensive. The book can, of course, be recommended to all who are fond of protozoa. However, since the book treats all aspects of an important group of microzooplankton emphasizing functional biology and its role in plankton ecosystems, it should also be of value to all interested in biological oceanography.

Epigenetic variation among natural populations of the South African sandhopper Talorchestia capensis

Ecological epigenetics is gaining importance within the field of Molecular Ecology, because of its novel evolutionary implications. Linking population ecology to the variation in epigenetic profiles can help explain the effect of environmental conditions on phenotypic differences among populations. While epigenetic changes have largely been investigated through the examination of DNA methylation under laboratory conditions, there is a limited understanding of the extent of DNA methylation variation in wild populations. Assuming that epigenetic variation is important in nature, the conditions experienced by different conspecific populations should result in levels of DNA methylation that are independent of their genetic differentiation. To test this, we investigated levels of DNA methylation among populations of the sandhopper Talorchestia capensis that show phenotypic (physiological) differences in their response to environmental conditions, at the same time evaluating their genetic relationships. Given the high levels of inter-individual physiological variation observed within populations, we further hypothesised that inter-individual differences in methylation would be high. Levels of genetic and epigenetic variation were assessed within and among populations from five localities using the methylation sensitive amplified polymorphism technique. Population differentiation was higher for epigenetics than genetics, with no clear geographical pattern or any relation to biogeography. Likewise, individuals showed greater variability in their epigenetic than their genetic profiles. Four out of five populations showed significant negative relationships between epigenetic and genetic diversity. These results show uncoupling between epigenetic and genetic variation and suggest that: (1) epigenetics are more responsive to local, site-specific environmental conditions than genetics and (2) individual differences in epigenetic profiles drive phenotypic variation within (and most likely among) natural populations. Within populations, epigenetics could offer a level of phenotypic flexibility beyond genetic constraint that allows rapid responses to variable or unpredictable environments, potentially compensating for low genetic variability.

Deep Genetic Divergence Between Geographically Isolated Populations of the Goldie Barb (Barbus pallidus) in South Africa: Potential Taxonomic and Conservation Implications

Barbus pallidus as it is presently defined has a disjunct distribution that is divided between northern and southern populations in South Africa. Sequence data from the cytochrome b gene region showed two distinct lineages that correspond to these geographically distant areas. Divergence between these two lineages was relatively high (5.5–6.5%) and comparable to typical interspecific divergences found between closely related southern African cyprinid fishes. Based on this deep genetic divergence, we conclude that the northern lineage may represent a previously unrecognised species or may belong to a different, but known species or species complex not associated with ‘true’ B. pallidus. These findings add to a growing body of evidence that freshwater fish diversity in southern Africa requires major revision.

Redescription of Potamonautes sidneyi (Rathbun, 1904) (Decapoda, Potamonautidae) and description of a new congeneric species from KwaZulu-Natal, South Africa

Abstract A new species of freshwater crab, Potamonautes danielsi sp. n., is described from the southern region of the KwaZulu-Natal Province, South Africa. Potamonautes danielsi most closely resembles Potamonautes sidneyi which is re-described here, but can be distinguished by a suite of key morphological characters including carapace shape and width, slim pereopods, inflated propodi of the chelipeds, and the shape and terminal segment length:subterminal segment length ratio of the 1st gonopod. In a previous study (Gouws et al. 2015), a 9.2–11.8 % divergence was found in the mitochondrial COI and 16S genes of the Potamonautes sidneyi clade, allowing for the delineation of a new species. Despite the clear molecular distinction between the two species, it is difficult to separate them based on individual morphological characters, as there is a great deal of overlap even among key features. The new species is found in slow-moving mountain streams and pools at high altitudes between Umhlanga and Mtamvuna, in KwaZulu-Natal.

Just off the beach: intrageneric distinctiveness of the bandtail goatfish Upeneus taeniopterus (Mullidae) based on a comprehensive alpha-taxonomy and barcoding approach

ABSTRACT The phenotypic, distributional, and genetic distinctiveness of the bandtail goatfish Upeneus taeniopterus within the genus Upeneus (Mullidae) is elaborated using a comprehensive alpha-taxonomic and barcoding approach. Based on a large number of morphometric, meristic and colour characters obtained from 71 preserved or freshly photographed specimens, an updated diagnosis, a redescription, and detailed inter- and intraspecific comparisons are provided. The distribution information is revised with strong emphasis on ensuring correct species identification. Upeneus taeniopterus shows intraspecific variation in morphology and number of oblique bars on the caudal fin related to two size classes, ‘subadults’ (< 12 cm SL) and ‘adults’ (12 cm SL or larger). Indications for population differences were only detected for the smaller size class, possibly reflecting geographic developmental differences. This species is widely distributed in the Indo-Pacific from Mozambique to the Tuamoto Archipelago and from the Ryukyu Islands to Tonga and occurs mostly in very shallow subtidal sandy beach or lagoon habitats of oceanic islands and atolls. Four new records of the species for Palau, Papua (Indonesia), Tonga and Vanuatu are reported. Comparisons with all other 36 congeners revealed clear differences from U. taeniopterus in the combination of maximum size, eight meristic and colour characters, distributional range and habitat selection. The only congeneric species with similarly large maximum size and wide distributional range is Upeneus vittatus, which differs however in morphology, colour and habitat. The congeneric species differ from U. taeniopterus with sequence divergences which are comparable to those observed among genera. More genetic tissue samples are needed to further investigate the relatedness among Upeneus species and to search for phylogeographic patterns in U. taeniopterus. The need to thoroughly study the insufficiently explored subtidal sandy habitats of oceanic islands and atolls is emphasized.

Distinction and relatedness – Taxonomic and genetic studies reveal a new species group of goatfishes (Upeneus; Mullidae)

Abstract Phenotypic and genetic differentiation among goatfish species of the genus Upeneus which had been formerly included in the so-called ‘vittatus group’ were examined using a comprehensive alpha-taxonomic and barcoding approach. Four of the five species of this group, U. indicus, U. suahelicus, U. supravittatus and U. vittatus, occur in the Western Indian Ocean (WIO), while U. parvus occurs in the Western Atlantic. An updated diagnosis of the WIO species, followed by detailed inter- and intraspecific comparison, is provided based on a large set of morphological and colour characters obtained from 134 specimens. The phenotypic comparisons among all five species and the evidence obtained from barcoding analyses of four species support the separation of U. parvus and U. vittatus from the other three more similar and closely related species which form the here newly established suahelicus group. An identification key for this species group is provided that should also minimize possible confusion with U. vittatus and species of the U. stenopsis group, two of which also occur in the WIO. New records for Madagascar and Saudi Arabia (U. suahelicus), Iran and Pakistan (U. supravittatus) and Sudan (U. vittatus) are reported. Application of this integrative approach to other species groups and species of Upeneus and the need to uncover intra- and interspecific distribution patterns and diversity more fully within the suahelicus group are outlined.