mtDNA Haplotype Frequencies Research Articles

Temporal stability and spatial divergence of mitochondrial DNA haplotype frequencies in red drum ( Sciaenops ocellatus ) from coastal regions of the western Atlantic Ocean and Gulf of Mexico

Restriction-site variation in mitochondrial (mt) DNA was assayed among 1675 red drum (Sciaenops ocellatus Linnaeus) sampled from 20 localities along the southeastern coast of the USA (western Atlantic) and the Gulf of Mexico (Gulf). Up to four consecutive year-classes (cohorts) were sampled at most localities. Nucleotide-sequence divergence among 170 mtDNA haplotypes identified ranged (in percentage) from 0.184 to 1.913, with a mean (±SD) of 0.887 ± 0.300. Comparisons of mtDNA haplotype frequencies across year-classes within localities were non-significant, indicating temporal stability of breeding components within localities. Significant heterogeneity in mtDNA haplotype frequencies was found across all localities, between (pooled) samples from the western Atlantic and the Gulf, and among geographically spaced, regional groupings in the Gulf. Genetic divergence between subpopulations of red drum in the western Atlantic and Gulf follows a pattern exhibited in other marine fishes, and probably stems from physical (historical environmental heterogeneity, absence of suitable habitat, and current patterns) and, perhaps, behavioral factors. Genetic differences among red drum in the Gulf appear to be due largely to an isolation-by-distance effect that is attributable to behavioral factors. The latter may include female philopatry to natal bays or estuaries, limited offshore (coastwise) movement of females relative to their natal bay or estuary, or both. Genetic divergence among red drum in the Gulf occurs despite high gene flow (estimated as the number of genetic effective migrants in an island mode). Conservation and management of red drum should be based on the premise that strategies for a given bay or estuary will impact geographically proximal bays or estuaries more than distal ones. Trajectories of correlograms in spatial autocorrelation analysis suggest a geographic neighborhood size, relative to genetic migration of red drum from a bay or estuary, of roughly 500 to 600 km.

Mitochondrial DNA Diversity and Population Structure of Spotted Seatrout (Cynoscion nebulosus) in Coastal Waters of the Southeastern United States

Restriction-site variation in mitochondrial (mt)DNA was examined among 470 spotted seatrout (Cynoscion nebulosus) sampled from eight localities in the northern Gulf of Mexico (Gulf) and two localities along the southeastern (Atlantic) coast of the United States. mtDNA fragment patterns generated 81 distinct mtDNA haplotypes (genotypes), three of which were found in 64% of the individuals assayed. Nucleotide sequence divergence among mtDNA haplotypes ranged from 0.148 to 1.808% and averaged (±SD) 0.676 ± 0.296%. Significant heterogeneity in mtDNA haplotype frequencies was detected between regions (i.e., Gulf vs Atlantic) and among sample localities from the northern Gulf. The latter appears to stem primarily (but not exclusively) from heterogeneity among samples from the western Gulf. Frequency plots of two of the common mtDNA haplotypes revealed strong east-west clines across the northern Gulf, with distinctive frequency discontinuities ("steps") between Gulf and Atlantic samples and between the westernmost sample in the Gulf (the lower Laguna Madre in Texas) and the next-most geographically proximate sample to the east. Spatial autocorrelation analysis of mtDNA haplotype frequencies among samples from the northern Gulf revealed a strong isolation-by-distance effect. These results support the hypothesis that spotted seatrout are spatially subdivided into discrete subpopulations or stocks. Divergence between Gulf and Atlantic subpopulations is likely related to historical vicariance, stemming from climatic changes occurring during glacial times. Other factors likely reduce present-day gene flow between subpopulations in the two regions. Divergence among subpopulations in the northern Gulf is more likely due to behavioral factors that limit (female) dispersal from a natal bay or estuary. The latter is consistent with studies of life history and returns from mark-and-recapture experiments. mtDNA diversity, an index of evolutionary effective (female) population size, also differed significantly among samples, with spotted seatrout from the lower Laguna Madre possessing appreciably reduced mtDNA diversity. This indicates a reduction in the effective number of females in the lower Laguna Madre and suggests that careful monitoring of spotted seatrout in the estuary may be warranted.

Molecular resolution of marine turtle stock composition in fishery bycatch: a case study in the Mediterranean.

Based on an extensive sampling regime from both nesting populations and bycatch, frequency analyses of mitochondrial (mt) DNA control region haplotypes in the Mediterranean were used to assess the genetic structure and stock composition of the loggerhead sea turtle, Caretta caretta, in different marine fisheries. The analyses show the following. (i) In drifting longline fisheries working in Mediterranean pelagic habitats 53-55% of turtles caught originated from the Mediterranean stock; (ii) In bottom-trawl fisheries all turtle bycatch is derived from this regional stock; (iii) This regional stock contribution to fishery bycatch suggests that the population size of the Mediterranean loggerhead nesting population is significantly larger than previously thought. This is consistent with a recent holistic estimate based on the discovery of a large rookery in Libya. (iv) Present impact of fishery-related mortality on the Mediterranean nesting population is probably incompatible with its long-term conservation. Sea turtle conservation regulations are urgently needed for the Mediterranean fisheries. (v) The significant divergence of mtDNA haplotype frequencies of the Turkish loggerhead colonies define this nesting population as a particularly important management unit. Large immature and adult stages from this management unit seem to be harvested predominantly by Egyptian fisheries. (vi) Combined with other data, our findings suggest that all the nesting populations in the Mediterranean should be considered as management units sharing immature pelagic habitats throughout the Mediterranean (and possibly the eastern Atlantic), with distinct and more localized benthic feeding habitats in the eastern basin used by large immatures and adults. (vii) Between the strict oceanic pelagic and the benthic stages, immature turtles appear to live through an intermediate neritic stage, in which they switch between pelagic and benthic foods.

Population structure of nuclear and mitochondrial DNA variation among humpback whales in the North Pacific.

The population structure of variation in a nuclear actin intron and the control region of mitochondrial DNA is described for humpback whales from eight regions in the North Pacific Ocean: central California, Baja Peninsula, nearshore Mexico (Bahia Banderas), offshore Mexico (Socorro Island), southeastern Alaska, central Alaska (Prince Williams Sound), Hawaii and Japan (Ogasawara Islands). Primary mtDNA haplotypes and intron alleles were identified using selected restriction fragment length polymorphisms of target sequences amplified by the polymerase chain reaction (PCR-RFLP). There was little evidence of heterogeneity in the frequencies of mtDNA haplotypes or actin intron alleles due to the year or sex composition of the sample. However, frequencies of four mtDNA haplotypes showed marked regional differences in their distributions (phi ST = 0.277; P < 0.001; n = 205 individuals) while the two alleles showed significant, but less marked, regional differences (phi ST = 0.033; P < 0.013; n = 400 chromosomes). An hierarchical analysis of variance in frequencies of haplotypes and alleles supported the grouping of six regions into a central and eastern stock with further partitioning of variance among regions within stocks for haplotypes but not for alleles. Based on available genetic and demographic evidence, the southeastern Alaska and central California feeding grounds were selected for additional analyses of nuclear differentiation using allelic variation at four microsatellite loci. All four loci showed significant differences in allele frequencies (overall FST = 0.043; P < 0.001; average n = 139 chromosomes per locus), indicating at least partial reproductive isolation between the two regions as well as the segregation of mtDNA lineages. Although the two feeding grounds were not panmictic for nuclear or mitochondrial loci, estimates of long-term migration rates suggested that male-mediated gene flow was several-fold greater than female gene flow. These results include and extend the range and sample size of previously published work, providing additional evidence for the significance of genetic management units within oceanic populations of humpback whales.

TEMPORAL CHANGE OF MITOCHONDRIAL DNA HAPLOTYPE FREQUENCIES AND FEMALE EFFECTIVE SIZE IN A BROWN TROUT (SALMO TRUTTA) POPULATION.

We report data on genetic drift of mitochondrial DNA (mtDNA) haplotypes in a natural brown trout (Salmo trutta) population in Sweden. Large temporal frequency shifts were observed over the 14 consecutive year classes studied. The observed rate of drift was used to estimate the effective size of the population. This effective size applies to the female segment of the population as mtDNA is maternally inherited. The magnitude of mtDNA haplotype frequency change is compared with the corresponding allele frequency changes at 14 allozyme loci in the same population. The female effective size is estimated as 58, which is approximately half the effective size of 97 for the total population (both sexes) previously obtained from the shifts of allozyme allele frequencies.

Aging, mating, and the evolution of mtDNA heteroplasmy in Drosophila melanogaster

Heteroplasmy, the presence of more than one type of mtDNA within cells, is common in animals and has been associated with aging and disease in humans. Changes in the frequencies of mtDNA variants between cell and animal generations thus bears on the evolution of mtDNA and the progression of diverse pathologies. We have used densitometry of Southern blots of individual heteroplasmic Drosophila melanogaster to study the effects of age, increased egg production after mating, and temperature on evolution of heteroplasmy within and between generations. The frequency of the longer mtDNA variant consistently increased between early and late cohorts of F1 offspring derived from 18 independent heteroplasmic mothers as they aged. Neither temperature (flies maintained at 25 degrees C and 18 degrees C) nor the holding of flies as virgins for 10 days before mating had significant effects on transmission patterns. However, at the ends of their lives, flies that had laid eggs at 25 degrees C had a greater frequency of the long mtDNA than did their siblings who had laid eggs at 18 degrees C. The evolution of heteroplasmy within a generation was studied in samples of siblings that either were mated or held as virgins, and then scored for mtDNA haplotype frequencies at two different ages (day 2 and day 14). Mated flies showed a significantly greater increase in the frequency of the long mtDNA variant with age than did the unmated flies. This system provides a model for the joint analysis of generational and chronological age in the transmission dynamics of a molecular polymorphism.

Mixed-stock analysis of Atlantic coast striped bass (Morone saxatilis) using nuclear DNA and mitochondrial DNA markers

Striped bass (Morone saxatilis) stocks comingle along the northeastern United States and Canadian coasts and support mixed-stock fisheries in which stock compositions fluctuate widely. Many approaches to stock analysis of these populations have been tried. The recent use of mitochondrial DNA (mtDNA) haplotype frequency data showed promising results, despite low levels of mtDNA variation; to improve resolution, we used a single-copy nuclear DNA (nDNA) probe with two mtDNA markers (major length variants and Taq I variants), alone or in combination. Striped bass reference collections were from the Hudson River and Chesapeake Bay, and mixed-stock collections (1989 and 1991) were from eastern Long Island, New York. The combination of the nDNA and mtDNA major length variant data provided lower but still quite high resolution potential (Dst = 0.417) in mixed-stock analysis (1991 collection) than the combination of all three markers (Dst = 0.552). However, unlike the Hudson River stock, the Chesapeake Bay stock is composed of multiple substocks that vary significantly in the frequencies of Taq I variants; this among-substock variation destabilizes the Chesapeake Bay reference data set and the resultant mixed-stock estimates. Thus, we recommend an approach based on composite nDNA and mtDNA major length variant markers.

Mitochondrial DNA variation in king mackerel ( Scomberomorus cavalla ) from the western Atlantic Ocean and Gulf of Mexico

King mackerel (Scomberomorus cavalla Cuvier) collected in 1992 and 1993 from 13 localities along the Atlantic coast of the southeastern USA and in the northern Gulf of Mexico were surveyed for variation in mitochondrial (mt)DNA and a nuclear-encoded dipeptidase locus (PEPA-2). Both polymorphic and fixed mtDNA restriction sites were identified and mapped using conventional and polymerase chain-reaction (PCR)-based methods. Heterogeneity in mtDNA haplotype frequencies was found only in comparisons of pooled haplotypes from Atlantic localities versus pooled haplotypes from Gulf localities. This finding indicates weak genetic divergence between king mackerel from the Atlantic and those from the Gulf. Frequencies of two PEPA-2 alleles essentially paralleled previous findings: one allele (PEPA-2a) was common among samples from western Gulf localities, whereas the other allele (PEPA-2b) was common among samples from Atlantic and eastern Gulf localities. There was considerable variation in PEPA-2 allele frequencies within broadly-defined regions. Variation in mtDNA haplotypes and PEPA-2 genotypes was independent, as was variation in mtDNA haplotypes with sex or age of individuals. Variation in PEPA-2 genotypes was not independent of sex or age of individuals. The latter result suggests that frequencies of PEPA-2 alleles in samples of king mackerel may stem, in part, from sex and age distributions of individuals within samples, and indicates that caution should be exercised in using allelic variation at PEPA-2 as a measure of population (stock) structure in king mackerel. The discordance in spatial patterning of mtDNA haplotypes versus PEPA-2 alleles across the Gulf (i.e. homogeneity in mtDNA haplotype frequencies versus heterogeneity in PEPA-2 allele frequencies) may be due to either female excess at several localities, sex-biased migration, or both. Observed patterns of genetic variation also are consistent with the hypothesis that king mackerel in the western Atlantic may have been subdivided during Pleistocene glaciation, and that the current distribution of PEPA-2 alleles may be a historical artefact.

Conservation Genetics of North American Freshwater Mussels Amblema and Megalonaias

Freshwater bivalves are among the most endangered groups of organisms in North America. Efforts to protect the declining mussel fauna are confounded by ambiguities associated with recognition of distinct evolutionary entities or species. This, in part, is due to the paucity of reliable morphological characters for differentiating taxa. We have employed allozymes and DNA sequence data to search for diagnosably distinct evolutionary entities within two problematic genera of unionid mussels, Amblema and Megalonaias. Within the genus Amblema three species are recognized based on our DNA sequence data for the mitochondrial 16S rRNA and allozyme data (Amblema neislerii, A. plicata, and A. elliotti). Only one taxonomically distinct entity is recognized within the genus Megalonaias—M. nervosa. Megalonaias boykiniana of the Apalachicolan Region is not diagnosable and does not warrant specific taxonomic status. Interestingly, Megalonaias from west of the Mississippi River, including the Mississippi, exhibited an allozyme and mtDNA haplotype frequency shift suggestive of an east‐west dichotomy. The results of this study eliminate one subspecies of Amblema and increase the range of A. plicata. This should not affect the conservation status of “currently stable” assigned to A. plicata by Williams et al. (1993). The conservation status of A. elliotti needs to be reexamined because its distribution appears to be limited to the Coosa River System in Alabama and Georgia.

Philopatry of male marine turtles inferred from mitochondrial DNA markers.

Recent studies of mitochondrial DNA (mtDNA) variation among marine turtle populations are consistent with the hypothesis that females return to beaches in their natal region to nest as adults. In contrast, less is known about breeding migrations of male marine turtles and whether they too are philopatric to natal regions. Studies of geographic structuring of restriction fragment and microsatellite polymorphisms at anonymous nuclear loci in green turtle (Chelonia mydas) populations indicate that nuclear gene flow is higher than estimates from mtDNA analyses. Regional populations from the northern and southern Great Barrier Reef were distinct for mtDNA but indistinguishable at nuclear loci, whereas the Gulf of Carpentaria (northern Australia) population was distinct for both types of marker. To assess whether this result was due to reduced philopatry of males across the Great Barrier Reef, we determined the mtDNA haplotypes of breeding males at courtship areas for comparison with breeding females from the same three locations. We used a PCR-restriction fragment length polymorphism approach to determine control region haplotypes and designed mismatch primers for the identification of specific haplotypes. The mtDNA haplotype frequencies were not significantly different between males and females at any of the three areas and estimates of Fst among the regions were similar for males and females (Fst = 0.78 and 0.73, respectively). We conclude that breeding males, like females, are philopatric to courtship areas within their natal region. Nuclear gene flow between populations is most likely occurring through matings during migrations of both males and females through nonnatal courtship areas.

Mitochondrial DNA variation in the scallop Pecten maximus (L.) assessed by a PCR-RFLP method.

Two PCR-RFLP mitochondrial DNA (mtDNA) markers were developed through the cloning and sequencing of mtDNA from the scallop Pecten maximus, and were used to study genetic differentiation off UK and Atlantic coast populations of this species. Although no distinct pattern of mtDNA haplotype frequencies was apparent and no diagnostic haplotypes were identified for any population, sequence divergence data provided convincing evidence that a P. maximus sample taken from Mulroy Bay, Eire, a semi-enclosed sea lough, was genetically differentiated form all other samples. However, this could not be unequivocally attributed to a restriction in gene flow, as the sample consisted of an ongrown single spatfall, which may not have been representative of the wild population. Despite the inability to separate populations on the basis of haplotype frequency, it was noteworthy that the frequency pattern of the commonest haplotype varied between sampling sites in a manner similar to that of allozyme allele frequencies in Aequipecten opercularis, a scallop species with a similar distribution and life history, for which there is evidence of population subdivision. Pecten maximus from St. Brieuc Bay, reasoned to be a self-recruiting population from reproductive and physiological evidence, could not be separated from other populations using mtDNA markers. Further investigation of this population with alternative markers is warranted.

Mitochondrial DNA variation in the scallop Pecten maximus (L.) assessed by a PCR-RFLP method

Two PCR-RFLP mitochondrial DNA (mtDNA) markers were developed through the cloning and sequencing of mtDNA from the scallop Pecten maximus, and were used to study genetic differentiation of UK and Atlantic coast populations of this species. Although no distinct pattern of mtDNA haplotype frequencies was apparent and no diagnostic haplotypes were identified for any population, sequence divergence data provided convincing evidence that a P. maximus sample taken from Mulroy Bay, Eire, a semi-enclosed sea lough, was genetically differentiated from all other samples. However, this could not be unequivocally attributed to a restriction in gene flow, as the sample consisted of an ongrown single spatfall, which may not have been representative of the wild population. Despite the inability to separate populations on the basis of haplotype frequency, it was noteworthy that the frequency pattern of the commonest haplotype varied between sampling sites in a manner similar to that of allozyme allele frequencies in Aequipecten opercularis, a scallop species with a similar distribution and life history, for which there is evidence of population subdivision. Pecten maximus from St Brieuc Bay, reasoned to be a self-recruiting population from reproductive and physiological evidence, could not be separated from other populations using mtDNA markers. Further investigation of this population with alternative markers is warranted.

Population Structure of Red Snapper from the Gulf of Mexico as Inferred from Analysis of Mitochondrial DNA

Abstract Variation in mitochondrial DNA (mtDNA) was examined among 707 red snapper Lutjanus campechanus representing 16 samples taken during 3 years from localities in the northern and western Gulf of Mexico. Ninety-two composite mtDNA haplotypes were revealed by 13 restriction enzymes (representing 93 inferred restriction sites). Significant heterogeneity (P = 0.042) in mtDNA haplotype frequencies was detected among the 16 samples; however, homogeneity tests of mtDNA haplotype frequencies between or among samples taken in different years at the same locality and among samples at different localities within the same year, were not significant. No phylogeographic structure of haplotypes was evident, nor were rare haplotypes clustered geographically. Spatial autocorrelations did not differ significantly from those expected when no correlation exists. These findings are consistent with the hypothesis that a single breeding population of red snapper inhabits the northern Gulf of Mexico. Intrapopulational mtDN...

The problem of sampling families rather than populations: relatedness among individuals in samples of juvenile brown trout Salmo trutta L.

In species exhibiting a nonrandom distribution of closely related individuals, sampling of a few families may lead to biased estimates of allele frequencies in populations. This problem was studied in two brown trout populations, based on analysis of mtDNA and microsatellites. In both samples mtDNA haplotype frequencies differed significantly between age classes, and in one sample 17 out of 18 individuals less than 1 year of age shared one particular mtDNA haplotype. Estimates of relatedness showed that these individuals most likely represented only three full‐sib families. Older trout exhibiting the same haplotypes generally were not closely related.

Genetic population structure of southern bluefin tuna ( Thunnus maccoyii )

Samples of southern bluefin tuna, Thunnus maccoyii (Castelnau), taken from off the coasts of South Africa, Western Australia, South Australia and Tasmania from 1992 to 1994 were analysed for six polymorphic allozyme loci (ADA *, GDA *, GPI-A *, MPI *, PGDH * and PGM-1 *, n = 595 to 733 per locus) and for mitochondrial DNA variants revealed by three restriction enzymes (Bam HI, Bcl I and Eco RI) detecting polymorphic cut sites (n = 555). No significant spatial heterogeneity was detected. There were no sex-related differences in allele or mtDNA haplotype frequencies. Juveniles (30 to 35 cm and 46 to 54 cm) from what are thought to be two temporally-separated spawning peaks showed no significant genetic differentiation. There were also no significant differences in allele or haplotype frequencies between fish smaller than 70 cm and those larger than 70 cm. These data are consistent with the null hypothesis of a single unit stock of southern bluefin tuna, with a single spawning area. This is located to the south of Java and off the north-west coast of Australia.

Stock Composition of the New York Bight Atlantic Sturgeon Fishery Based on Analysis of Mitochondrial DNA

Abstract One of the few remaining fisheries for Atlantic sturgeon Acipenser oxyrinchus takes place during spring and fall in the New York Bight, but no information on the stock composition of this fishery is available. We used data from mitochondrial DNA (mtDNA) restriction fragment length polymorphism analysis to estimate the relative contributions of source stocks of Atlantic sturgeon to a New York Bight fishery sample (N = 112) collected in 1993 and 1994. Composite mtDNA haplotype frequencies of source populations were first characterized with five informative restriction enzymes: Bgl I, Msp I, EcoR V, Hinf I, and Hinc II. All St. Lawrence River, Quebec, and St. John River, New Brunswick, specimens had an identical haplotype (genotypic diversity = 0.0); for the purposes of mixed-stock analysis, both populations were pooled as the “Canadian stock.” Genotypic diversity ranged between 0.483 and 0.750 among samples from the Hudson River in New York, the Edisto River in South Carolina, and the Ogeechee, Alt...

Mitochondrial DNA analysis of Mongolian populations and implications for the origin of New World founders.

High levels of mitochondrial DNA (mtDNA) diversity were determined for Mongolian populations, represented by the Mongol-speaking Khalkha and Dariganga. Although 103 samples were collected across Mongolia, low levels of genetic substructuring were detected, reflecting the nomadic lifestyle and relatively recent ethnic differentiation of Mongolian populations. mtDNA control region I sequence and seven additional mtDNA polymorphisms were assayed to allow extensive comparison with previous human population studies. Based on a comparative analysis, we propose that indigenous populations in east Central Asia represent the closest genetic link between Old and New World populations. Utilizing restriction/deletion polymorphisms, Mongolian populations were found to carry all four New World founding haplogroups as defined by WALLACE and coworkers. The ubiquitous presence of the four New World haplogroups in the Americas but narrow distribution across Asia weakens support for GREENBERG and coworkers' theory of New World colonization via three independent migrations. The statistical and geographic scarcity of New World haplogroups in Asia makes it improbable that the same four haplotypes would be drawn from one geographic region three independent times. Instead, it is likely that founder effects manifest throughout Asia and the Americas are responsible for differences in mtDNA haplotype frequencies observed in these regions.

Mitochondrial-DNA Variation and Genetic-Population Structure in Rocky Mountain Bighorn Sheep (Ovis canadensis canadensis)

Mitochondrial-DNA (mtDNA) variation in Rocky Mountain bighorn sheep was assessed to determine relationships among populations and the usefulness of mtDNA analysis for the conservation of bighorn sheep. Phylogeographic analysis revealed relatively divergent mtDNA haplotypes within herds and several geographically widespread haplotypes. This suggested that gene flow has occurred on a regional scale at some time in the past and that populations have not been subdivided by long-term biogeographic barriers. Nonetheless, significant differentiation in mtDNA-haplotype frequencies among herds suggested that little gene flow currently exists among populations. Failure to recognize that historical (phylogeographic) and current population structure may not be concordant could lead to erroneous conclusions and conservation strategies.

Associations between physical isolation and geographical variation within three species of Neotropical birds

AbstractWe studied effects of physical isolation on geographical variation in mtDNA RFLP polymorphisms and a suite of morphological characters within three species of neotropical forest birds; the crimson‐backed tanager Ramphocelus dimidiatus, the blue‐gray tanager Thraupis episcopus, and the streaked saltator Saltator albicollis. Variation among populations within continuous habitat on the Isthmus of Panama was compared with that among island populations isolated for about 10000 years. Putative barriers to dispersal were influential, but apparent isolation effects varied by species, geographical scale, and whether molecular or morphological traits were being assessed. We found no geographical structuring among the contiguous, mainland sampling sites. Migration rates among the islands appeared sufficient to maintain homogeneity in mtDNA haplotype frequencies. In contrast, variation in external morphology among islands was significant within two of three species. For all species, we found significant variation in genetic and morphological traits between the island (collectively) and mainland populations. Interspecific variation in the effects of isolation was likely related to differential vagility. These data generally corroborate other studies reporting relatively great geographical structuring within tropical birds over short distances. Behaviourally based traits ‐ low vagility and high ‘sensitivity’ to geographical barriers ‐ may underlie extensive diversification within neotropical forest birds, but more extensive ecological and phylogeographic information are needed on a diverse sample of species.

Temporal stability of mtDNA haplotype frequencies in American shad stocks: to pool or not to pool across years?

Temporal stability of mtDNA haplotype frequencies in American shad stocks: to pool or not to pool across years?