Morphological and genetic differentiation of Patella granularis (Gastropoda: Patellidae): recognition of two sibling species along the coast of southern Africa
- Authors: Ridgway, Tyronne M , Stewart, Barbara A , Branch, George M , Hodgson, Alan N
- Date: 1998
- Subjects: Patellidae
- Language: English
- Type: Article
- Identifier: vital:6944 , http://hdl.handle.net/10962/d1011971
- Description: Morphological and isozyme variations between 13 populations of the species hitherto named Patella granularis were investigated to see whether differences in shell structure between the west coast versus the south and east coasts of southern Africa are supported by other morphological features or by genetic differences. The shells showed a definite decrease in size from west to east, but this is correlated with productivity and is of no diagnostic use in distinguishing between populations. Discriminant functions analysis based on shell morphometrics failed to separate populations from the three coastal regions. Shells from the northern east coast do, however, have shell nodules with a dark pigmentation, distinctly separating them from those further south and west. No differences in radular or soft part morphology were detected between the populations, but the four northernmost populations on the east coast have a significantly shorter Z looping of the gut than the other populations along the coast. Significant microstructural differences in the sperm were also detected between these two groups of populations. Electrophoretic analysis of 16 enzyme loci failed to detect any significant differences between the west and south coast populations, but revealed a genetic identity (Nei) of 0.528 as well as four diagnostic alleles between the four northernmost populations from the east coast compared with those to the south and west. The two genetically distinct forms occurred sympatrically at one of the study sites on the east coast (Coffee Bay). It was concluded the two groupings were sufficiently different to warrant the recognition of a separate species, which is centred in KwaZulu-Natal on the east coast and extends south to Coffee Bay, from where it is replaced by P. granularis. There is, however, no evidence at all that the west coast populations are in any way separable from the remaining populations of P. granularis on the south coast.
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- Date Issued: 1998
Spatial and temporal variability in recruitment of intertidal mussels around the coast of southern Africa
- Authors: Harris, Jean M , Branch, George M , Elliot, Bridget L , Currie, Bronwen , Dye, Arthur H , McQuaid, Christopher D , Tomalin, Bruce J , Velasquez, Claudio
- Date: 1998
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447579 , vital:74658 , https://www.ajol.info/index.php/az/article/view/154717
- Description: Intensity of intertidal mussel recruitment was compared across a range of different spatial and temporal scales around the coast of southern Africa between June 1995 and October 1996. Comparison of the east and west coasts revealed significantly higher recruit densities on the west coast, corresponding to larger adult densities. This difference between the two coasts reflects biogeographic disparities in mussel species composition, growth rates and spawning intensities, oceanographic conditions and productivity. Significant spatial variations in recruitment were recorded between regions 100–1000 km apart and between localities 1–25 km apart. Results suggest that the influence of dispersal processes on recruitment patterns acts at a relatively small scale, and may affect the distribution and abundance of adults among shores only a few kilometres apart.
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- Date Issued: 1998