Observations on genetic diversity of Bulinus cernicus (Gastropoda: Planorbidae) from Mauritius

Abstract

Enzyme variation has been investigated in eight populations of Bulinus cernicus from Mauritius using isoelectric focusing and starch gel electrophoresis. Of 11 loci examined for 10 enzyme systems, seven were found to be polymorphic. These were malate dehydrogenase, glucose phosphate isomerase, acid phosphatase (A and B), 3‐hydroxybutyrate dehydrogenase, 6‐phosphogluconate dehydrogenase and NADH‐dependent diaphorase. Invariant loci were phosphoglucomutase, xanthine oxidase, fructokinase and αaL‐glycerophosphate dehydrogenase. The percentage of polymorphic loci within the populations ranged from 9.1% to 54.5%. The average heterozygosity per population for all loci ranged from 0,009 to 0.203. Genetic distance values ranged from 0.01 to 0.3 with the higher values associated with comparisons of populations from the north‐west and south‐east of the island. A comparison of data sets for 1980 and 1986 revealed the allelic frequencies at five enzyme loci to be remarkably consistent.

Contrasting temporal dynamics and spatial patterns of population genetic structure correlate with differences in demography and habitat between two closely-related African freshwater snails

“…Perhaps this conclusion is unsurprising, given that B. camerunensis inhabits a large, deep lake in which the water level does not vary significantly. This pattern places it alongside species such as Bulinus globosus (Njiokou et al ., 1994), Bulinus cernicus (Rollinson et al ., 1990), and B. glabrata (Langand et al ., 1999), which also exhibit stable temporal genetic structures. By contrast, the spatial and temporal structure of B. forskalii , which inhabits smaller streams, pools and marshes (Brown, 1994), is most akin to those of Biomphalaria pfeifferi (Webster et al ., 2001; Charbonnel et al ., 2002), and B. truncatus (Viard et al ., 1997), which exhibit genetic signatures characteristics of highly dynamic demographic systems, including bottleneck and extinction/recolonization events.…”

“…Even though empirical temporal genetic studies examining the impact of demography and gene flow on the distribution of neutral genetic variation within natural populations have lagged behind theoretical developments, recent efforts have started to address this imbalance. Although anadromous and marine fish have been the focus of much attention (Waples & Teel, 1990; Jorde & Ryman, 1996; Garant, Dodson & Bernatchez, 2000; Ardren & Kapuscinski, 2003; Østergaard et al ., 2003; Jensen et al ., 2005), another group deserving more consideration is the hermaphroditic tropical freshwater snails, including many species of Bulinus and Biomphalaria , the two genera of freshwater snails associated with human schistosome transmission in Africa (Rollinson et al ., 1990; Njiokou et al ., 1994; Viard, Justy & Jarne, 1997; Langand et al ., 1999; Webster et al ., 2001; Charbonnel et al ., 2002; Chlyeh et al ., 2002). Several characteristics that make them an excellent system with which to address the effects of habitat stability on demography and population genetic structure include their occupation of a diverse range of habitats (Brown, 1994); their reliance on passive rather than active dispersal, via animal agents such as birds (Boag, 1986) or by flooding events and water currents (Woolhouse, 1988); and their short generation time of a few weeks (Woolhouse & Chandiwana, 1989; Woolhouse, 1992).…”

Selfing and outcrossing in hermaphrodite freshwater gastropods (Basommatophora): where, when and why

“…Parent-offspring analysis is an alternative approach (Mulvey & Vrijenhoek, 1981;Rollinson & Wright, 1984;Woodruff, Mulvey & Yipp, 1985;Wethington & Dillon, 199 1 ) , analogous to progeny-array analyses used by plant population biologists (Brown, 1990). In basommatophorans, the hypotheses of either pure selfing, or pure outcrossing with only one partner have been tested.…”

Freshwater snails on Mafia Island, Tanzania with special emphasis upon the genus Bulinus (Gastropoda: Planorbidae)

“…), B. cernicus), (B. bavayi)), (B. forskalii)). Bulinus cernicus is found only on Mauritius (Rollinson et al, 1990) and B. bavayi is common to Madagascar and Aldabra (Wright, 1971). The nucleotide divergence between B. scalaris and Bulinus sp.…”