Morphological and Genetic Variation in Three Populations of Hoplobatrachus tigerinus from Bangladesh

In order to investigate the morphological and genetic variation of Indian bullfrog Hoplobatrachus tigerinus, live samples were collected from three populations located in Khulna (southern part), Char Nilokhia and Netrokona (central part) in Bangladesh. The proportions of head length and head width (HL : HW), eye length and tympanum diameter (EL:TD), head length and snout length (HL : SL), internarial space and interorbital distance (IN:IOD) and internarial space and distance from nostril to tip of snout (IN:NS) of the Khulna population were significantly higher (p<0.05) than those of the other two populations. For allozyme study, 4 enzymes were screened, where 5 presumptive scorable loci were identified. The highest values of mean proportion of polymorphic loci (<0.95), mean number of alleles per locus and mean number of heterozygous loci per individual were observed in the Khulna population (60%, 1.60 and 14.0% respectively). The pairwise genetic differentiation (FST and Nei’s D) was the highest (0.279 and 0.157, respectively) between the Khulna and Netrokona populations. The UPGMA dendrogram showed two clusters i.e. the Char Nilokhia and Netrokona populations formed one cluster, whereas the Khulna population alone made another cluster. These results suggested that the Khulna population diverged morphologically and genetically from the other two populations probably due to its geographical distance. Further extensive study will be necessary for elucidating the whole aspects of differentiation in H. tigerinus from Bangladesh.DOI: http://dx.doi.org/10.3329/pa.v19i2.16954 Progress. Agric. 19(2): 139 - 149, 2008

An allozyme study of sexual and vegetative regeneration in Hieracium pilosella

Allozyme markers were used to fingerprint clones of the grassland plant Hieracium pilosella L. and, by inference, to estimate the relative importance of sexual and vegetative reproduction in a population. Field studies in populations of clonal plant species have often reported negligible or absent recruitment from seed. In contrast, studies of genetic markers have found substantial clonal diversity in populations, suggesting recruitment of new genets into established populations. Our results showed that H. pilosella regenerates from seed both within and between dense clonal patches. Two sites differing in environmental conditions were sampled to investigate how the balance between seed-derived and stolon-derived recruitment changes with biotic and abiotic stress. In a relatively drought-prone site on a south-facing slope, the balance was shifted towards recruitment from seed, compared with a mesic site in which vegetative regeneration was more important.

Taxonomic distinction of Ophelia barquii and O. bicornis (Annelida: Polychaeta) in the Mediterranean as revealed by ISSR markers and the number of nephridiopores

Ophelia bicornis sensu lato is a polychaete living in intertidal sandy habitats of Mediterranean and European Atlantic coasts, whose systematics have been strongly debated in the past few decades. In the present work the count of nephridiopores was coupled with genetic analysis carried out with DNA markers (inter simple sequence repeats) for a total of 30 individuals collected at six Italian beaches. Exact test, analysis of molecular variance, non-metric multidimensional scaling and assignment tests clearly separated individuals with five nephridiopore pairs from those with six pairs. This finding validated results of a recent allozyme study in which O. bicornis sensu lato was split into O. bicornis sensu stricto (six nephridiopore pairs) and O. barquii (five nephridiopore pairs). This paper represents a further contribution to the estimation of biodiversity within marine invertebrates.

Geographic patterns of genetic diversity in subterranean amphipods of the Pilbara, Western Australia

Twenty-six species of subterranean amphipods have been described from the Pilbara, Western Australia, based on variation in morphological characters. Many are known only from single bores. The Pilbara is rich in iron ore, and thus, an understanding of species’ diversity and their distribution is necessary both to manage resources and to conserve fauna. A previous allozyme study of nine bores in a single catchment in the Pilbara found low levels of genetic differentiation among individuals, but the diversity was not associated with single bores. The area studied appeared to contain a single widespread species common to all nine bores, in sympatry with a second, rare species, represented by a single specimen. The present study analysed allozymic variation in amphipods from 26 bores in four additional catchments in the Pilbara, to test the generality of these findings. At each site, samples with similar allelic arrays were found in multiple bores, in sympatry with rare divergent genotypes. Geological complexity was associated with increased genetic differentiation over short geographical distances. With few exceptions, each catchment contained a unique suite of species, suggesting that catchments may form hydrological barriers to gene flow, resulting in local speciation events.

Interpopulation relationships in two species of Antarctic fish Notothenia rossii and Champsocephalus gunnari from the Kerguelen Islands: an allozyme study

Enzymatic polymorphism was used to detect variability within Notothenia rossii from two sites on the Kerguelen Plateau and Champsocephalus gunnari from the same sites and the South Orkney Islands. No polymorphism was found in the second species and it was low but not statistically significant in the first. This apparent homogeneity does not substantiate suggestions from other results that the populations can be separated, especially in the case of C. gunnari. Other approaches will be necessary to solve definitively the question of population separation.

Mating system and distribution of enzyme genetic variation in bracken (Pteridium aquilinum)

An allozyme study of populations of bracken, Pteridium aquilinum, revealed very low rates of intragametophytic selfing, on average 0.046, despite potential hermaphroditism and selfing of the gametophytes. The average number of genotypes per population was only 3.0 and mean heterozygosity equalled 0.015. Several populations consisted of only one genotype. The level of genetic divergence among populations was considerable. The mean value of the differentiation among populations (FST) was high (0.307) and the gene flow values were low, equalling 0.52 and 0.23 depending on the method of estimation. It is suggested that the life history of P. aquilinum, characterized by variable rates of spore production, vegetative reproduction, and the inefficiency of gametophyte growth and reproduction in established bracken stands, promotes genetic differentiation between populations. Key words: bracken, Pteridophyta, genetic variation, gene flow, mating systems.

Molecular systematics in the acanthocephalan genus Echinorhynchus (sensu lato) in northern Europe

SUMMARYNew biological species and high levels of inter- and intraspecific genetic divergence were discovered in an allozyme study of some North European members of the acanthocephalan genus Echinorhynchus (sensu lato), parasites of fish and malacostracan crustaceans. (i) A strong differentiation between the marine E. gadi and the fresh- and brackish-water E. salmonis (genetic identity I ≃ 0) supports a generic distinction between these taxa; however, the subdivision would not entirely concur with the concepts of Echinorhynchus (sensu stricto) and Metechinorhynchus suggested earlier. (ii) Samples of E. gadi from the Baltic, Norwegian and North Seas included three distinct, partially sympatric biological species (spp. I–III; I ≃ 0·5). (iii) E. bothniensis, previously only known from the northern Baltic Sea, represents a complex of freshwater taxa with an intermediate host relationship to the ‘glacial relict’ Mysis spp. and with a distributional and host analogy to the North American E. leidyi. A population in a northern lake in the Barents Sea basin is closely related to E. bothniensis of the Baltic area, but is probably specifically distinct; the divergence between these populations (I ≃ 0·6) is similar to that between their Mysis host species. (iv) Considerable intraspecific differentiation (Fst = 0·25), probably reflecting post-glacial population bottlenecks, was found between Baltic and nearby lacustrine E. bothniensis, and between Atlantic and Baltic E. gadi sp. I.