West Coast Populations Research Articles

The effect of salinity and recruitment on the distribution of Tetraclita squamosa and Tetraclita japonica (Cirripedia; Balanomorpha) in Hong Kong

The barnacles, Tetraclita squamosa and Tetraclita japonica, exhibit different vertical and horizontal distributions along the salinity gradient from the east to west coast of Hong Kong. On the oceanic east coast, T. japonica was common higher on the shore [1.25-2 m above chart datum (C.D.)] than T. squamosa (1-1.25 m above C.D.), whereas on the estuarine west coast, only T. squamosa was found. Annual recruitment of both species occurred on the east coast but no recruitment was recorded on the west coast for 2 years, suggesting that west coast populations of T. squamosa are relics of stochastic, past recruitment, and may decline without further recruitment. Under laboratory conditions, the two species do not vary in their salinity tolerance or osmoregulation. Adults of both species ceased activity when salinity dropped to 10‰ (=mean summer salinity on west coast). The LC 50 of larvae was between 14-16‰ and 100% of naupliar larvae died when salinity was 9‰, showing that the low summer salinities on the west coast may have an impact on some stages of the barnacles' life histories. The east-west distribution and population structure of these two species appear, therefore, to be dependent on the intensity and frequency of past settlement which may be affected by salinity stress.

Matrilinear phylogeography of Atlantic salmon (Salmo salar L.) in Europe and postglacial colonization of the Baltic Sea area.

Sixty-four samples from 46 salmon populations totalling 2369 specimens were used for polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the mitochondrial ND1 region. The final analyses included 3095 specimens from 60 populations in Northern Europe. A subsample was analysed by RFLP of ND3/4/5/6. Representative RFLP haplotypes from different parts of the distribution area were sequenced and the phylogeny of European haplotypes and their relations to the North American lineage was described. The four common European haplotypes derive from the ancestral ND1-BBBA (rooting the European clade to the North American) by one-step substitutions: AAAA < AABA < BBBA > BBBB. The Swedish west-coast populations differ from the geographically close southern Baltic, indicating absence of inward and limited outward gene flow through the Danish straits during the last 8000 years. Within the Baltic Sea, only three ND1 haplotypes were detected and there was no variation for ND3/4/5/6. In the whole southern Baltic and in lakes Vänern, Ladoga and Onega the haplotype AABA dominated. Proposed postglacial colonization routes to the Baltic Sea are discussed in relation to the haplotype distribution pattern.

Biogeographic history of geminate cirrhitoids (Perciformes: Cirrhitoidea) with east–west allopatric distributions across southern Australia, based on molecular data

AbstractThe biogeographic history of three cirrhitoid species pairs with east–west allopatric distributions across southern Australia was examined by determining levels of mitochondrial DNA sequence divergence and applying molecular clock calibrations. Similar levels of genetic divergence were observed for Aplodactylus Valenciennes and Goniistius Gill species pairs, but these were more than twice that observed for a Nemadactylus Richardson pair. Molecular clock calibrations suggested divergences occurred during the late Miocene and mid Pliocene, respectively. Given evidence of high dispersal capabilities, the habitat and climatic barriers of the Australian south coast appear too small to have facilitated speciation of the cirrhitoids examined. A mechanism is proposed by which ancestral cirrhitoids were vicariantly isolated into east and west coast populations during periods of climate change. Although Aplodactylus and Goniistius divergences occurred during the same period, separate vicariant events across the Australian north and south coasts are invoked.

Cultural revolution in whale songs.

Humpbacks have picked up a catchy tune sung by immigrants from a distant ocean. The song patterns of humpback whales (Megaptera novaeangliae) depend on where they live, with populations inhabiting different ocean basins normally singing quite distinct songs. Here we record a unique and radical song change in the song of humpback whales in the Pacific Ocean off the Australian east coast. Their song was replaced rapidly and completely by the song of the Australian west coast population from the Indian Ocean, apparently as a result of the introduction of only a small number of 'foreign' singers. Such a revolutionary change is unprecedented in animal cultural vocal traditions and suggests that novelty may stimulate change in humpback whale songs.

Geographic Signatures of North American West Coast Estuaries

West Coast estuaries are geologically young and composed of a variety of geomorphological types. These estuaries range from large fjords to shallow lagoons; from large to low freshwater flows. Natural hazards include E1 Ninos, strong Pacific storms, and active tectonic activity. West Coast estuaries support a wide range of living resources: five salmon species, harvestable shellfish, waterfowl and marine birds, marine mammals, and a variety of algae and plants. Although populations of many of these living resources have declined (salmonids), others have increased (marine mammals). West Coast estuaries are also centers of commerce and increasingly large shipping traffic. The West Coast human population is rising faster than most other areas of the U.S. and Canada, and is distributed heavily in southern California, the San Francisco Bay area, around Puget Sound, and the Fraser River estuary. While water pollution is a problem in many of the urbanized estuaries, most estuaries do not suffer from poor water quality. Primary estuarine problems include habitat alterations, degradation, and loss; diverted freshwater flows; marine sediment contamination; and exotic species introductions. The growing West Coast economy and population are in part related to the quality of life, which is dependent on the use and enjoyment of abundant coastal natural resources.

Historical incidence of Perthida leafminer species (Lepidoptera) in southwest Western Australia based on herbarium specimens

Examination of more than 500 herbarium specimens of Eucalyptus marginata and E. rudis for the presence of two species of leafminers, Perthida spp., indicated that these native insect species were very rare in southwest Western Australia until first recorded in metropolitan Perth in 1878 and 1897, respectively, when west coast populations of both leafminer species evidently increased dramatically. The first record from the south coast dates from 1901 near Albany. Evidence of leafminer populations on E. marginata remote from coastal settlements was not recorded until 1917, near Cranbrook. The first record in jarrah forest was in 1967, some 10 years after outbreaks of the pest insect are known to have occurred in the forest. The Perthida leafminer species on E. rudis was first recorded from inland areas in 1904 and appears to have increased more rapidly in abundance than the species found on E. marginata. These early geographical and species differences in incidence are discussed in terms of changing disturbance patterns, which have not been simultaneous across southwest Western Australia.

Morphological and genetic differentiation of Patella granularis (Gastropoda: Patellidae): recognition of two sibling species along the coast of southern Africa

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.

Morphological and genetic differentiation of Patella granularis (Gastropoda: Patellidae): recognition of two sibling species along the coast of southern Africa

AbstractMorphological 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.

Aspects of the biology of the abaloneHaliotis midae(Linne, 1758) on the east coast of South Africa. 2. Reproduction

The South African abalone Haliolis midae is a dioecious, broadcast spawner with a high fecundity. Histological examination and gonad bulk indices showed that individuals are iteroparous, asynchronous spawners, and that the breeding season extends from March through to October, spawning peaking between April and June. The structure of the ovary and testis, and the process of gametogenesis are typical of haliotid species. Males and females spawn partially or totally, with atresia of residual gametes occurring after spawning. No resting stage was apparent and gonadal recrudescence began immediately after spawning. Sexual maturity was first attained at 20–25 mm shell width, and the size at 50% sexual maturity was attained at approximately 35 mm shell width in all of the populations studied, a size considerably lower than that of previously studied West Coast populations of H. midae.

Sidebar: The decline of sea-run fishes in California: An ongoing tragedy

Abstract Not Available – First paragraph follows: California has the southernmost West Coast populations of sea-run or “anadromous” fish, which spawn in fresh water but spend part of their lives in the ocean. The 13 anadromous fish species native to California include chinook salmon, steelhead trout, river lamprey, white sturgeon and longfin smelt.

Interannual variability in coastal Washington Dungeness crab (Cancer magister) populations: larval advection and the coastal landing strip

ABSTRACTSubstantial and unexplained variations in abundance characterize US west coast populations of Dungeness crab, Cancer magister. It is likely that this variability reflects oceanic advection of larvae given the dynamics of the California Current system, the protracted (4–5 months) pelagic larval phase and the restrictive nature of juvenile habitat requirements. We compare 40 years of Ekman transport vectors during January‐May (1947– 1986) with time‐lagged and stratified commercial landings for coastal Washington (1951–1990). Persistent landward and net northward flow characterized the circulation of near‐surface waters during the larval periods studied. A mechanism for progressive seaward transport of larvae through ontogeny, as proposed by others, was not apparent. Overall, above‐ (below‐) average year classes were associated with relatively weak (strong) northward transport and, to a lesser degree, strong (weak) landward transport. Based on these analyses and in consideration of the prevailing coastal circulation, we propose that the relative magnitude of C. magister juvenile recruitment and, hence, incoming year class strength, reflects: (1) the proportion of larvae retained within a relatively narrow (≤ 15 km) and heterogeneous ‘coastal landing strip’, (2) the availability of suitable substrate within the coastal landing strip at time of settlement and (3) the magnitude of downstream advective losses (export) of larvae from the California‐Oregon‐Washington coastal system. Based on a consideration of the physics of the California Current system and the larval biology of the species, significant linkage of Dungeness crab populations along the west coast of North America is likely.

The Origin and Evolution of Parthenogenesis in Heteronotia Binoei (Gekkonidae): Reciprocal Origins and Diverse Mitochondrial DNA in Western Populations

Parthenogenetic lines of the Heteronotia binoei complex are genetically diverse, of hybrid origin, and geographically widespread, ranging from central Australia to the west coast. Analysis of the western populations revealed a class of mitochondrial DNA (mtDNA) approximately 12% different from the mtDNAs found among parthenogens further east. Detailed analysis of mtDNAs from 59 western individuals revealed far greater diversity than previously reported for any parthenogenetic vertebrate. Phylogenetic comparisons with mtDNAs from the bisexual parental species identified the maternal parent(s) as coming from the SM6 species, most probably from west coast populations. This ancestry contrasts with that of the more eastern parthenogenetic lines, which had as parents females of the other bisexual parental species, CA6. The nucleotide diversity of mtDNA among the western parthenogens, although higher than usual (x 0.38%), is low compared with the variation found within (2.1%) and among (3.9-7.8%) SM6 populations. This diversity illustrates the importance of rigorous sampling of related bisexual populations for interpreting variation among unisexuals. Despite the high mtDNA diversity, these parthenogens probably arose from a relatively small geographic area. The distinct geographic ranges of parthenogens that have the two major classes of mtDNA suggest that the western populations arose separately and further to the west than did the other lines. If so, then the two groups of parthenogenetic lines should be regarded as separate species.

High Incidence of Significant Urinary Ascorbic Acid Concentrations in a West Coast Population—Implications for Routine Urinalysis

Examination of 4379 routine urinalysis specimens with dipsticks sensitive to ascorbic acid showed that 22.8% were positive specimens. The mean urinary vitamin C concentration in this population was 2120 mumol/L. There was a high rate of false-negative dipstick results for hemoglobin in patients with vitamin C in the urine. The highest false-negative rates were observed in urine samples containing less than 50 erythrocytes per high-power field. In further experiments when volunteers consumed supplemental oral USP vitamin C at doses of 100, 250, 500, and 1000 mg or vitamin C-containing fruit juices, even the lowest doses of oral vitamin C or juice resulted in sufficient urinary vitamin C to produce false-negative dipstick results in hemoglobin and glucose testing. To prevent potentially dangerous false-negative results, screening urinalysis protocols relying only on dipstick testing should include a check for urinary vitamin C or use a dipstick that is not subject to vitamin C interference.

Adaptation of an Introduced Host to an Indigenous Parasite

Introduction of striped bass to the west coast from the east coast of the U.S.A. provided the opportunity to study a recent host-parasite association in a marine system. An indigenous species of parasite was known to induce pathological changes in the introduced population. Because the west coast population has been in association with this pathogenic parasite more than 20 generations, we predicted that the host reaction of the west coast population would be less severe compared to that of the naive east coast stock of striped bass. This prediction was tested by conducting reciprocal infection experiments with east and west coast hosts and parasites. The group of west coast striped bass had a lower intensity of infection and exhibited less tissue damage compared to the group of east coast striped bass. We suggest that selection has acted only on the host and is driven by parasite-induced host mortality. This type of 1-sided selection is in contrast to present models of the evolution of host-parasite associations.

GEOGRAPHICAL AND GENETIC STRUCTURE OF LIFE-HISTORY VARIATION IN MILKWEED BUGS (HEMIPTERA: LYGAEIDAE: ONCOPELTUS).

Life-history variation was investigated using crosses within and among the laboratory-bred descendants of six geographic samples of the large milkweed bug, Oncopeltus fasciatus. These samples spanned the species' range, from permanent (year-round) populations on tropical islands to seasonal middle-latitude populations found in temperate North America. The seasonal populations must be refounded each year by colonists from more southern populations. Marked differences in life-history traits (particularly in age at first reproduction, clutch size, and rate of egg production) were observed among the six population samples, with tropical-island and west-coast populations being the most distinct. In the eastern and central United States, there was a marked north-south difference in life history. Crossing experiments demonstrated a genetic basis for these differences. F1 and F2 hybrids from crosses between continental populations tended to have intermediate phenotypes. The similarity of the seasonal middle-latitude populations' life histories and the consistency of the distribution of life-history characteristics among populations (across years) may indicate that the north-south difference in life history is due to selection on these traits during the annual northward movement or that migrants represent a distinct genetic form of this species.

WING COLOURATION DIFFERENCE BETWEEN THE BRUCE SPANWORM OPEROPHTERA BRUCEATA (HULST) (LEPIDOPTERA: GEOMETRIDAE) AND THE WINTER MOTH OPEROPHTERA BRUMATA (L.) ON VANCOUVER ISLAND

In a recently completed study involving pheromone trapping of the winter moth, Operophtera brumata (L.), and the Bruce spanworm, O. bruceata (Hulst), on Vancouver Island (Pivnick et al. 1988), I noticed that O. bruceata had wing colouration different from sympatric O. brumata. The west coast O. bruceata has a pale yellow-orange costal margin on the underside of the forewings and this is faint to absent in O. brumata (Fig. 1). It is also absent from O. bruceata in Saskatoon, which is interesting because some authors consider the west coast population of O. bruceata to be a separate species: the western winter moth, O. occidentalis (see Ferguson 1978; Pivnick et al. 1988). Descriptions of O. bruceata (Brown 1962) and O. brumata (Cuming 1961), and a taxonomic key to these two species (Eidt et al. 1966), do not mention any distinctive wing markings that could be used to separate the two species.

A Comprehensive Study of Genic Variation in Natural Populations of Drosophila melanogaster. I. Estimates of Gene Flow from Rare Alleles

In order to assess the evolutionary significance of molecular variation in natural populations of Drosophila melanogaster, we have started a comprehensive genetic variation study program employing a relatively large number of gene-protein loci and an array of populations obtained from various geographic locations throughout the world. In this first report we provide estimates of gene flow based on the spatial distributions of rare alleles at 117 gene loci in 15 worldwide populations of D. melanogaster . Estimates of Nm (number of migrants exchanged per generation among populations) range from 1.09 in East-Asian populations (Taiwan, Vietnam and Australia) to 2.66 in West-Coast populations of North America. These estimates, among geographic populations separated by hundreds or even thousands of miles, suggest that gene flow among neighboring populations of D. melanogaster is quite extensive. This means that, for selectively neutral genes, we should expect little differentiation among neighboring populations. A survey of eight West-Coast populations of D. melanogaster (geographically comparable to Drosophila pseudoobscura) showed that in spite of extensive gene flow, populations of D. melanogaster show much more geographic differentiation than comparable populations of D. pseudoobscura. From this we conclude that migration in combination with natural selection rather than migration alone is responsible for the geographic uniformity of molecular polymorphisms in D. pseudoobscura.

Biochemical population genetics of the black musselChoromytilus meridionalis

Gene products of nine loci were examined by horizontal starch-gel electrophoresis in five samples of black mussels, Choromytilus meridionalis, from the south-western Cape coast. Allelic frequency variation for four polymorphic proteins suggests no racial differences between west and south coast populations. Mean heterozygosity (H) showed a non-significant increase from south to west coast populations. The duration of the pelagic larval stage and currents may both contribute to long-distance larval recruitment, although gene flow between neighbouring populations may be more important.

LATITUDINAL CLINE INDROSOPHILA MELANOGASTERFOR KNOCKDOWN RESISTANCE TO ETHANOL FUMES AND FOR RATES OF RESPONSE TO SELECTION FOR FURTHER RESISTANCE

We have introduced a device for selecting Drosophila for increased resistance to very high concentrations of ethanol fumes. This device has enabled us to: 1) select quickly and easily over a thousand flies at a time, and 2) score the knockdown time of every fly in the distribution, while causing very little injury to the flies. A sample of nine west coast populations of Drosophila melanogaster showed a significant trend toward higher knockdown resistance in more northern populations. A population's level of knockdown resistance was virtually uncorrelated with its alcohol dehydrogenase (Adh) allele frequencies. Five of the above nine populations were then subjected to selection for further knockdown resistance. Each population was divided randomly into four groups of 256 flies: two lines to be selected, and two lines to remain unselected as control lines. In every generation each selected line was measured for knockdown resistance, and the last quartile of flies to be knocked down was saved to continue the selection cycle. Population sizes of the selected and unselected lines were all maintained at 256. Realized heritability, based on the responses to selection of the first four generations, was calculated for each selected line. The five populations were significantly heterogeneous for heritability estimates; the average heritability of the five populations pooled was 0.143 ± 0.019. Over the course of twelve generations, the ten selected lines increased their knockdown times by an average factor of 2.40. Before selection, the five populations were heterogeneous for knockdown resistance, and resistance was greatest among the most northern populations. The amount of change of knockdown resistance over the course of selection was also correlated with latitude: the most southern population increased its knockdown time by a factor of 2.23, and the most northern population increased it by a factor of 2.55. After ten generations of selection, the cline of knockdown resistance was about 4.5 times as steep as that before selection. Small phenotypic differences among populations before selection were thus exaggerated by the action of selection. The differences among populations in their rates of response to selection were attributed to genetic differences that existed before selection. The pattern of change of Adh frequencies over the course of selection was very inconsistent, both among and within populations. From this inconsistency of change of Adh alleles with selection, and the lack of correlation between Adh frequencies and knockdown resistance before selection, we concluded that Adh frequency changes could not have had much effect on the responses of the selected lines.

Allozyme variation in Greek wild populations of Drosophila melanogaster and D. simulans along a North-South gradient

Allozyme frequency data from five Greek wild sympatric populations of Drosophila melanogaster and D. simulans along a North-South gradient were analyzed for genotype-environment relationships. The regression coefficient of genetic distance on geographic distance indicates that there is a significant relationship between these parameters for D. melanogaster only. Highly significant differences in specific alleles at certain loci were found between the various local populations studied. The changes in αGpdh F of D. melanogaster and Est-6 F of D. simulans exhibited clinal patterns in allele frequencies. In addition, analysis of D. melanogaster αGpdhFand Adh F allele frequencies shows that the Greek data do not have regression coefficients (regressing allele frequency on degrees North of latitude) of the same sign as East-and West-Coast United-States populations. These contradictory data are discussed in relation to what is known about the maintenance of the Adh and αGpdh polymorphisms.