Search

The article provides information on the activities of migrating birds, which includes traveling around 30,000 kilometers annually back and forth between the Northern breeding place and the southern feeding sites. It relates that one of the major problems being faced by these birds is the decreasing number of wetlands for which they can use as their feeding sites. The author affirms that because of this reason, he volunteered to do take part in preserving the natural resources.

Comparative study of character evolution in the shorebirds is presently limited because the phylogenetic placement of some enigmatic genera remains unclear. We therefore used Bayesian methods to obtain a well-supported phylogeny of 90 recognized genera using 5kb of mitochondrial and nuclear sequences. The tree comprised three major clades: Lari (gulls, auks and allies plus buttonquails) as sister to Scolopaci (sandpipers, jacanas and allies), and in turn sister to Charadrii (plovers, oystercatchers and allies), as in previous molecular studies. Plovers and noddies were not recovered as monophyletic assemblages, and the Egyptian plover Pluvianusis apparently not a plover. Molecular dating using multiple fossil constraints suggests that the three suborders originated in the late Cretaceous between 79 and 102Mya, and at least 14 lineages of modern shorebirds survived the mass extinction at the K/T boundary. Previous difficulties in determining the phylogenetic relationships of enigmatic taxa reflect the fact that they are well-differentiated relicts of old, genus-poor lineages. We refrain from suggesting systematic revisions for shorebirds at this time because gene trees may fail to recover the species tree when long branches are connected to deep, shorter branches, as is the case for some of the enigmatic taxa.

To test the hypothesis put forward by Feduccia of the origin of modern birds from transitional birds, we sequenced the first two complete mitochondrial genomes of shorebirds (ruddy turnstone and blackish oystercatcher) and compared their sequences with those of already published avian genomes. When corrected for rate heterogeneity across sites and non–homogeneous nucleotide compositions among lineages in maximum likelihood (ML), the optimal tree places palaeognath birds as sister to the neognaths including shorebirds. This optimal topology is a re–rooting of recently published ordinal–level avian trees derived from mitochondrial sequences. Using a penalized likelihood (PL) rate–smoothing process in conjunction with dates estimated from fossils, we show that the basal splits in the bird tree are much older than the Cretaceous–Tertiary (K–T) boundary, reinforcing previous molecular studies that rejected the derivation of modern birds from transitional shorebirds. Our mean estimate for the origin of modern birds at about 123 million years ago (Myr ago) is quite close to recent estimates using both nuclear and mitochondrial genes, and supports theories of continental break–up as a driving force in avian diversification. Not only did many modern orders of birds originate well before the K–T boundary, but the radiation of major clades occurred over an extended period of at least 40 Myr ago, thus also falsifying Feduccia's rapid radiation scenario following a K–T bottleneck.

Common chaffinches (Fringilla coelebs) are thought to have colonized the Atlantic island archipelagoes (the Azores, Madeira, and the Canaries) from neighboring continental populations (Iberia and north Africa) within the last million years. However, colonization may have occurred separately from north Africa to the Canaries and from Iberia to the Azores (as would be predicted geographically) or in one wave from Iberia to the Azores and then to Madeira and the Canaries. These alternatives have different implications for the evolution of morphometric and plumage differentiation in island chaffinches. To determine the most likely colonization route, we estimated the phylogenetic relationships among island and continental subspecies of common chaffinch using sequences from four mtDNA genes (cytochromeb, ATPase 6, NADH 5, and the control region). The most strongly supported mtDNA phylogeny places the continental subspecies together as the sister group to a monophyletic clade containing the island subspecies. This is consistent with a single wave of colonization, and suggests that patterns of similarity among Atlantic island common chaffinches, such as blue pigmentation, short wings, and long tarsi, are due to common colonization history rather than to convergent evolution in a common island environment. However, spectral analysis of phylogenetic splits showed that although monophyly of island haplotypes is favored, there is also substantial support for their polyphyletic origin. We attribute the latter to the confounding effect of homoplasy at multistate sites and to the relatively rapid sequence of colonization events which provided insufficient time for the accumulation of strong phylogenetic signal. These problems are likely to be significant impediments in attempts to test hypotheses of phylogenetic histories of recently evolved populations and taxa.

mtDNA B-loop sequences were examined in shrews of the genus Sorex. All specimens possessed an array of tandem repeats in which each repeat was 78 to 80 base pairs (bp) in length. Each specimen also possessed a 76-bp imperfect copy of the tandem repeats. Three observations are consistent with the tandem repeats being the product of concerted evolution: (1) the repeats are capable of forming secondary structures; (2) there was minimal sequence divergence between tandem repeats within individuals; and (3) although the tandem repeats and the imperfect repeat presumably arose due to a duplication event in an ancestor of the shrews, the imperfect repeat per sewas not copied in any of the specimens observed. Interspecific homology can therefore be assumed for the imperfect repeat. Furthermore, given the apparent high rate of concerted evolution within a genome, tandem repeats in different individuals may be compared as though only a single copy were present. By including data from the imperfect repeat, the last tandem repeat, and the surrounding unique sequence, cladistic and genetic distance approaches to phylogeny reconstruction indicated two sister groups within the subgenus Otisorex. One group was composed of Sorex fumeusand the S. cinereusspecies complex and the other group was composed of S. hoyi , S.monticolus, S. vagrans,and S. palustris. Resolution of relationships among recently evolved taxa demonstrated the usefulness of selected regions of the D-loop for molecular systematic studies.

Populations of common mynas introduced to Australia, New Zealand, Fiji, Hawaii, and South Africa from India during the last century were compared genetically with the extant native population using isozyme electrophoresis of 39 presumptive loci. Average heterozygosity, mean number of alleles/locus, and the percentage of polymorphic loci are lower in the introduced populations, and the 18% loss of alleles involves only alleles that are rare in the native population. The native population is only weakly subdivided genetically (FST= 0.032) whereas the introduced populations are much more differentiated (FST= 0.123), and the mean genetic distance among them is significantly greater than among native samples. The reduction in mean number of alleles/locus and average heterozygosity is greatest in the South African population, consistent with a very small effective size in the founder population. In the introduced populations, random drift is implicated by the different subsets of polymorphic loci they possess, by their greater variance in allele frequencies, and by shifts either side of the native means. It is concluded that in the evolutionarily short period of 100–120 years, bottlenecks and random drift have promoted genetic shifts equal to those between different subspecies of birds.

Peripherally isolated populations of common chaffinches (Fringilla coelebs) in the Canaries, Madeira, and Azores were compared genetically with their putative ancestral stock in Iberia and Morocco, and with a population of blue chaffinches (F. teydea) from Tenerife, using protein electrophoresis of 42 loci. The continental populations are only weakly differentiated genetically (FST= 0.092), despite distinctive subspecific differences in plumage and morphometrics between Iberia and Morocco populations. Estimated levels of gene flow among continental populations are high enough to account for their relative genetic homogeneity, and it is unlikely that homogenizing selection is operating to mimic the effects of gene flow. In contrast, the Atlantic island populations are well differentiated genetically (FST= 0.321), and have diverged considerably from their continental conspecifics. The development of significant genetic differentiation within the Canaries but not the Azores likely results from smaller population sizes, very restricted gene flow, and enhanced random drift in the former populations. There is no convincing evidence in support of stronger directional selection acting on genotypes or phenotypes to reduce within‐population variability in Canaries populations as proposed by Grant (1979), although other tenets of his model of island evolution are supported by our analysis. Although genetic variability is reduced in four of the Canaries populations, only the Hierro population appears to have encountered a severe bottleneck. Yet it has not differentiated markedly from the La Palma population to which it is subspecifically allied. We conclude that gradual divergence in isolated populations of small to moderate size is the most plausible explanation for the evolution of intraspecific and interspecific diversity in Atlantic island chaffinches.

Descendent populations of chaffinches (Fringilla coelebs) introduced to New Zealand about 120 years ago were compared with “ancestral” populations in northern Europe and with those in a broader region of Europe (including Iberia) using protein electrophoresis at 42 loci and 12 skeletal measurements. The New Zealand populations exhibit very small scale differentiation in genetics (Fst= 0.040) and morphometrics, and the haphazard pattern of among‐population variation does not align with environmental variation nor is it predicted by the geographic proximity of populations. Thus random drift is implicated in the differentiation among the descendent populations. The New Zealand chaffinches have diverged only slightly in morphometrics from an extant population in southern England, and constant heritability rate tests suggest that random drift alone could account for this small shift. In sharp contrast, the European populations are subdivided genetically (Fst= 0.222) and morphometrically, and this subdivision coincides with the Pyrenees mountains between Iberia and northern Europe which act as a barrier to gene flow between these regions. Iberian populations have smaller skulls and longer wings on average than northern European populations and are characterized by high frequencies of alternative common alleles at Adaand Np.Within both the Iberian and northern European regions, however, populations are effectively panmictic in protein‐encoding genes, indicating that homogenizing gene flow is apparently extensive enough to prevent among‐population differentiation in allozymes by drift. Variation in body size as represented by PC I is related to environmental productivity across Europe, unlike in New Zealand. These observations jointly suggest that longer term adaptive differentiation via selection for optimal body size has evolved in Europe. Because multilocus evolution is expected to proceed slowly in populations subject to the opposing forces of selection and homogenizing gene flow, I argue that local adaptation within “ancestral” populations in northern Europe may still be evolving.

The magnitudes of phenotypic variances in peripherally isolated populations of common chaffinches (Fringilla coelebs) in the Azores, Madeira, and Canaries relative to their continental source populations in Iberia and Morocco have played a pivotal role in the formulation of competing hypotheses of phenotypic evolution in these isolates. Because Van Valen's niche variation hypothesis and Grant's model of island evolution were based on museum skins prone to measurement error and temporal variation, we re‐examined the patterns of phenotypic variability using more precise skeletal measurements from freshly collected specimens. Levene's tests showed that univariate character variances were homogeneous in all island and continental populations, although there was a consistent trend for the magnitude of the variances to be lower for all characters in all Canary island populations. Multivariate Levene's tests, however, revealed significantly reduced total variances in the Hierro and Madeira populations compared to some Azores and continental populations. The Azores and continental populations did not differ in variability, and lower variances in the Canaries were not related to the presence or absence of the congeneric blue chaffinch (F. teydea), contrary to the predictions of Van Valen's niche variation hypothesis. Population variability was not inversely related to differentiation or isolation within the Azores or Canaries archipelagoes, opposite to the association reported by Grant. Our results also differ from both previous studies which reported much larger differences in population variabilities, and this likely reflects the use of heterogeneous samples of museum specimens, less precise external characters, and the use of tests sensitive to sample size. Differentiation among populations has been markedly greater in the Canary islands, implicating founder events and possibly historically stronger directional selection as determinants of this enhanced divergence relative to the Azores. These variance‐reducing processes are unlikely to explain current lower levels of phenotypic variability because there has been sufficient time since colonization for replenishment of variability in polygenic characters. Average heterozygosities at putatively neutral allozyme loci are 1.6 times higher in the Azores compared to the Canaries, and support the view that effective population sizes are smaller in the latter archipelago. We argue that reduced variances in the Canary island populations represent lower equilibrium levels maintained by drift and mutation in populations with smaller long‐term effective sizes, consistent with Lynch and Hill's neutral model of phenotypic evolution. Although episodes of selection in the past may have been interspersed with long periods of effective neutralism and drift, adaptationist hypotheses invoking a primary role for variance‐reducing selection appear to be unwarranted.

Summary Variation within and between eight subspecies of Canada geese was assessed by restriction fragment analysis of mitochondrial DNA (mtDNA), electrophoresis of proteins encoded by nuclear DNA, and the morphometric analysis of skeletons. Estimates of mtDNA sequence divergence between Canada goose subspecies ranged from 0.04 to 2.54%. Pairwise comparisons of the three data matrices revealed that only mtDNA variation and body size are significantly correlated. Subspecies with northern breeding grounds are small-bodied and display small variations of one mtDNA clone, whereas those breeding further south are largebodied and show small differences in another mtDNA clone. Canada geese exhibit strong geographic differentiation with respect to mtDNA sequence, but weak structuring in protein-encoding nuclear DNA. This finding can be explained by a lower level of gene flow for the mitochondrial genome than for the nuclear genome, which in turn emanates from the maternal inheritance of mtDNA and male-biased dispersal in Canada geese. Despite male-mediated flow of nuclear genes, strong morphometric differentiation persists among Canada geese subspecies.

Mitochondrial DNA control region sequences of 25 Knots sampled from 10 populations and possibly four subspecies (canutus, islandica, rogersi, rufa) were obtained by PCR and direct sequencing. Only 7 haplotypes were found worldwide, all closely related to one another and differing by 1–3 substitutions. Knots have most probably expanded to their current population size from a refugial population that was severely bottlenecked late in the Pleistocene. Preliminary results from RAPDs are consistent with this prediction, in that Knots from North America appear to be genetically distinct from Knots elsewhere.

Parsimony analysis of sequence variation in the mitochondrial (mt) DNA, D-loop region indicated that the masked shrew (Sorex cinereus) and the prairie shrew (S. haydeni) are monophyletic taxa, but mtDNA from S. cinereus has introgressed into S. haydeni. Within S. cinereus there was a lack of concordance between mtDNA clades and currently accepted subspecific designations. The taxonomic designation S. c. acadicus corresponded to a mtDNA clade composed of specimens found predominantly in Nova Scotia and New Brunswick. This clade shared a more recent ancestor with a lineage common to Ontario and Quebec than it did with mtDNA haplotypes from specimens sampled in Michigan and Alberta. S. c. cinereus is, therefore, a paraphyletic assemblage based on mtDNA haplotypes. Little support for currently recognized subspecific designations was found from an analysis of molecular variance among the populations of S. c. cinereus. The mtDNA clades fit a biogeographic hypothesis in which populations of shrews were isolated by factors associated with the Wisconsinan, glaciation and then reinvaded Canada from coastal and southern continental refugia. However, divergence times preceding the recent Wisconsinan glaciation are indicated by applying a molecular clock calibrated for shrews to observed genetic-distance values.

Populations of the masked shrew (Sorex cinereus) and the prairie shrew (S. haydeni) occurring in sympatry in Alberta were compared genetically with each other and with populations of S. cinereus across Canada using protein electrophoresis of 33 loci. Despite distinct morphologic differences between S. cinereus and S. haydeni, in Alberta these taxa were less genetically differentiated (Ne's genetic distance, DN = 0.006; Rogers' genetic distance, DR = 0.047) than were conspecific populations of S. cinereus across Canada (DN = 0.019; DR = 0.058). Although there were no fixed allele differences among the populations sampled, there was a unique allele at a moderate frequency in S. haydeni (PEP-SB, 0.375). This may be indicative of no gene flow between these two taxa and thus they may be valid species. The genetic similarity of the masked and prairie shrews implies that S. cinereus is a paraphyletic taxon and suggests a recent divergence of these taxa, perhaps in the late Pleistocene or the early Holocene. Among populations of S. cinereus across Canada, the pattern of differentiation is consistent with a biogeographic model in which shrews re-colonized Canada from multiple refugia following the retreat of the Wisconsin glaciers.