Small Founder Population Research Articles

Parasites and genetic diversity in an invasive bumblebee.

Biological invasions are facilitated by the global transportation of species and climate change. Given that invasions may cause ecological and economic damage and pose a major threat to biodiversity, understanding the mechanisms behind invasion success is essential.Both the release of non-native populations from natural enemies, such as parasites, and the genetic diversity of these populations may play key roles in their invasion success.We investigated the roles of parasite communities, through enemy release and parasite acquisition, and genetic diversity in the invasion success of the non-native bumblebee, Bombus hypnorum, in the United Kingdom.The invasive B. hypnorum had higher parasite prevalence than most, or all native congeners for two high-impact parasites, probably due to higher susceptibility and parasite acquisition. Consequently parasites had a higher impact on B. hypnorum queens’ survival and colony-founding success than on native species. Bombus hypnorum also had lower functional genetic diversity at the sex-determining locus than native species. Higher parasite prevalence and lower genetic diversity have not prevented the rapid invasion of the United Kingdom by B. hypnorum. These data may inform our understanding of similar invasions by commercial bumblebees around the world.This study suggests that concerns about parasite impacts on the small founding populations common to re-introduction and translocation programs may be less important than currently believed.

The coding sequence of POMC and obesity and appetite in Labrador retriever dogs

BackgroundIn human beings, the heritability of obesity is estimated at 40–70%, but only a small proportion (<3%) of the genetic variants that account for naturally occurring obesity have been discovered. In dogs, selective breeding from small founder populations has led to trait-associated genes being concentrated within breeding populations, making dogs an appealing model for genetic study. Labrador retriever dogs are commonly prone to obesity and are highly food motivated; such a high prevalence within the breed suggests a genetic predisposition. The aim of this study was to discover the genetic basis of obesity in Labrador retriever dogs. MethodsPet dogs were prospectively selected for study. Body condition score was used to initially group them as lean or obese. They were further divided into two groups—obese, highly food-motivated dogs; and lean, non-food-motivated dogs—by a combination of a standardised questionnaire to owners and a veterinary surgeon taking a clinical and behavioural history. The coding sequence of AGRP, POMC, and MC4R were sequenced in several dogs from each group. Findings35 dogs (15 obese, 20 lean) were studied. The coding sequence of AGRP was normal in all dogs. Six single nucleotide polymorphisms (SNPs) were identified in MC4R, and eight SNPs and two deletions (one coding, one intronic) were found in POMC. There was no significant difference in the distribution of these variants between lean and obese groups for any of the variants except the coding deletion in POMC. Of 15 obese, food-motivated dogs, that deletion was heterozygous in eight and homozygous in two; the deletion was heterozygous in two of the 20 lean, non-food-motivated dogs. The association with obesity and high food motivation was significant (p=0·001). InterpretationMelanocortin signalling has a key role in normal energy homoeostasis; POMC is a precursor protein whose cleavage products act on MC4 and MC3 receptors to suppress appetite and increase energy expenditure. The deletion of 14 base pairs in exon 3 of POMC is predicted to disrupt the POMC protein, stopping production of its cleavage products β-melanocyte-stimulating hormone and β-endorphin and is therefore a strong candidate for causing much or all of the obesity susceptibility in Labrador retriever dogs. Further genetic studies are in progress to assess the prevalence of the deletion in larger cohorts of dogs from the same and different breeds, with functional studies also planned. FundingWellcome Trust, UK Medical Research Council, NIHR Cambridge Biomedical Research Centre.

High Risk Population Isolate Reveals Low Frequency Variants Predisposing to Intracranial Aneurysms

3% of the population develops saccular intracranial aneurysms (sIAs), a complex trait, with a sporadic and a familial form. Subarachnoid hemorrhage from sIA (sIA-SAH) is a devastating form of stroke. Certain rare genetic variants are enriched in the Finns, a population isolate with a small founder population and bottleneck events. As the sIA-SAH incidence in Finland is >2× increased, such variants may associate with sIA in the Finnish population. We tested 9.4 million variants for association in 760 Finnish sIA patients (enriched for familial sIA), and in 2,513 matched controls with case-control status and with the number of sIAs. The most promising loci (p<5E-6) were replicated in 858 Finnish sIA patients and 4,048 controls. The frequencies and effect sizes of the replicated variants were compared to a continental European population using 717 Dutch cases and 3,004 controls. We discovered four new high-risk loci with low frequency lead variants. Three were associated with the case-control status: 2q23.3 (MAF 2.1%, OR 1.89, p 1.42×10-9); 5q31.3 (MAF 2.7%, OR 1.66, p 3.17×10-8); 6q24.2 (MAF 2.6%, OR 1.87, p 1.87×10-11) and one with the number of sIAs: 7p22.1 (MAF 3.3%, RR 1.59, p 6.08×-9). Two of the associations (5q31.3, 6q24.2) replicated in the Dutch sample. The 7p22.1 locus was strongly differentiated; the lead variant was more frequent in Finland (4.6%) than in the Netherlands (0.3%). Additionally, we replicated a previously inconclusive locus on 2q33.1 in all samples tested (OR 1.27, p 1.87×10-12). The five loci explain 2.1% of the sIA heritability in Finland, and may relate to, but not explain, the increased incidence of sIA-SAH in Finland. This study illustrates the utility of population isolates, familial enrichment, dense genotype imputation and alternate phenotyping in search for variants associated with complex diseases.

Genetic and morphometric evidence on a Galápagos Island exposes founder effects and diversification in the first-known (truly) feral western dog population

Domesticated animals that revert to a wild state can become invasive and significantly impact native biodiversity. Although dogs can be problematic locally, only the Australasian dingo is known to occur in isolation from humans. Western dogs have experienced more intense artificial selection, which potentially limits their invasiveness. However, feral dogs eradicated from Isabela Island, Galápagos in the 1980s could be the first-known exception. We used DNA and morphometric data from 92 of these dogs to test the hypotheses that (i) these dogs persisted independently of humans for up to a century and a half since descending from a handful of dogs introduced in the early 1800s, vs. (ii) similarly to other western feral dog populations, they reflected continuous recruitment of strays from human settlements on a portion of the Island. We detected one dominant maternal lineage and one dominant paternal lineage shared by the three subpopulations, along with low autosomal genetic diversity, consistent with the hypothesized common origins from a small founder population. Genetic diversity patterns among the three island subpopulations were consistent with stepping-stone founder effects, while morphometric differentiation suggested rapid phenotypic divergence, possibly due to drift and reinforced by selection corresponding to distinct microclimates and habitats on Isabela. Despite the continued presence of free-ranging dogs in the vicinity of settlements on Isabela and other Galápagos Islands, feral populations have not reestablished in remote areas since the 1980s, emphasizing the rarity of conditions necessary for feralization of modern western dogs.

Reconstructing the Population Genetic History of the Caribbean

The Caribbean basin is home to some of the most complex interactions in recent history among previously diverged human populations. Here, we investigate the population genetic history of this region by characterizing patterns of genome-wide variation among 330 individuals from three of the Greater Antilles (Cuba, Puerto Rico, Hispaniola), two mainland (Honduras, Colombia), and three Native South American (Yukpa, Bari, and Warao) populations. We combine these data with a unique database of genomic variation in over 3,000 individuals from diverse European, African, and Native American populations. We use local ancestry inference and tract length distributions to test different demographic scenarios for the pre- and post-colonial history of the region. We develop a novel ancestry-specific PCA (ASPCA) method to reconstruct the sub-continental origin of Native American, European, and African haplotypes from admixed genomes. We find that the most likely source of the indigenous ancestry in Caribbean islanders is a Native South American component shared among inland Amazonian tribes, Central America, and the Yucatan peninsula, suggesting extensive gene flow across the Caribbean in pre-Columbian times. We find evidence of two pulses of African migration. The first pulse—which today is reflected by shorter, older ancestry tracts—consists of a genetic component more similar to coastal West African regions involved in early stages of the trans-Atlantic slave trade. The second pulse—reflected by longer, younger tracts—is more similar to present-day West-Central African populations, supporting historical records of later transatlantic deportation. Surprisingly, we also identify a Latino-specific European component that has significantly diverged from its parental Iberian source populations, presumably as a result of small European founder population size. We demonstrate that the ancestral components in admixed genomes can be traced back to distinct sub-continental source populations with far greater resolution than previously thought, even when limited pre-Columbian Caribbean haplotypes have survived.

The role of founder effects on the evolution of reproductive isolation

Several theories argue that large changes in allele frequencies through genetic drift after a small founding population becomes allopatrically isolated can lead to significant changes in reproductive isolation and thus trigger the origin of new species. For this reason, founder speciation has been proposed as a potent force in the generation of new species. Nonetheless, the relative importance of such 'founder effects' remains largely untested. In this report, I used experimental evolution to create one thousand replicates that underwent an extreme bottleneck and to study whether founder effects can lead to an increase in reproductive isolation in Drosophila yakuba. Even though the most common outcome of inbreeding is extinction, founder effects can lead to increased premating reproductive isolation in a very small proportion of cases. Changes in reproductive isolation after a founding population bottleneck are similar to changes in other phenotypic traits, in which inbreeding might displace the mean phenotypic value and substantially increase the phenotypic variance. This increase in phenotypic variance does not confer an increase in the response to selection for reproductive isolation in artificial selection experiments, indicating that the increased phenotypic variance is not caused by increases in additive genetic variance. These results also demonstrate that, similar to morphological and life-history traits, behavioural traits can be affected by inbreeding and genetic drift.

Phylogeographic evidence of cognate recognition site patterns and transformation efficiency differences in H. pylori: theory of strain dominance

BackgroundHelicobacter pylori has diverged in parallel to its human host, leading to distinct phylogeographic populations. Recent evidence suggests that in the current human mixing in Latin America, European H. pylori (hpEurope) are increasingly dominant at the expense of Amerindian haplotypes (hspAmerind). This phenomenon might occur via DNA recombination, modulated by restriction-modification systems (RMS), in which differences in cognate recognition sites (CRS) and in active methylases will determine direction and frequency of gene flow. We hypothesized that genomes from hspAmerind strains that evolved from a small founder population have lost CRS for RMS and active methylases, promoting hpEurope’s DNA invasion. We determined the observed and expected frequencies of CRS for RMS in DNA from 7 H. pylori whole genomes and 110 multilocus sequences. We also measured the number of active methylases by resistance to in vitro digestion by 16 restriction enzymes of genomic DNA from 9 hpEurope and 9 hspAmerind strains, and determined the direction of DNA uptake in co-culture experiments of hspAmerind and hpEurope strains.ResultsMost of the CRS were underrepresented with consistency between whole genomes and multilocus sequences. Although neither the frequency of CRS nor the number of active methylases differ among the bacterial populations (average 8.6 ± 2.6), hspAmerind strains had a restriction profile distinct from that in hpEurope strains, with 15 recognition sites accounting for the differences. Amerindians strains also exhibited higher transformation rates than European strains, and were more susceptible to be subverted by larger DNA hpEurope-fragments than vice versa.ConclusionsThe geographical variation in the pattern of CRS provides evidence for ancestral differences in RMS representation and function, and the transformation findings support the hypothesis of Europeanization of the Amerindian strains in Latin America via DNA recombination.

Recent colonization by a coastal plant of inland habitats at an ancient freshwater lake, Lake Biwa: multilocus sequencing and a demographic history of Lathyrus japonicus (Fabaceae)

AbstractAncient lakes have been recognized as “long‐term isolated islands” in terrestrial ecosystems. Lake Biwa, one of the few ancient lakes that formed around 4 million years ago, harbors many coastal species that commonly inhabit seashores. The beach pea, Lathyrus japonicus, is a typical coastal species of this freshwater lake, where morphological, physiological, and genetic differentiations have been reported between Biwa and coastal populations. Whether Biwa populations were isolated for long periods throughout Pleistocene climatic oscillations and subsequent range shifts is unclear. We assessed population genetic structure and demography of beach pea in this ancient freshwater lake using the sequences of eight nuclear loci. The results of STRUCTURE analyses showed evidence of admixture between Biwa and coastal populations, reflecting recent gene flow. The estimated demographic parameters implemented by the isolation with migration model (IM model) revealed a recent divergence (postglacial period) of Biwa populations, with some gene flow from Biwa to coastal populations. In addition, Biwa populations were significantly smaller in size than the ancestral or coastal populations. Our study suggests that a Holocene thermal maximum, when transgression could allow seeds from coastal plants to access Lake Biwa, was involved in the origin of the Biwa populations and their genetic divergence. Thus, coastal populations might have migrated to Lake Biwa relatively recently. Our study concluded that ancestral migrants in Lake Biwa were derived from small founding populations and accelerated genetic isolation of Biwa populations during short‐term isolation.

Haplotype diversity generated by ancient recombination-like events in the MHC of Indian rhesus macaques

The Mamu-A, Mamu-B, and Mamu-DRB genes of the rhesus macaque show several levels of complexity such as allelic heterogeneity (polymorphism), copy number variation, differential segregation of genes/alleles present on a haplotype (diversity) and transcription level differences. A combination of techniques was implemented to screen a large panel of pedigreed Indian rhesus macaques (1,384 individuals representing the offspring of 137 founding animals) for haplotype diversity in an efficient and inexpensive manner. This approach allowed the definition of 140 haplotypes that display a relatively low degree of region variation as reflected by the presence of only 17 A, 18 B and 22 DRB types, respectively, exhibiting a global linkage disequilibrium comparable to that in humans. This finding contrasts with the situation observed in rhesus macaques from other geographic origins and in cynomolgus monkeys from Indonesia. In these latter populations, nearly every haplotype appears to be characterised by a unique A, B and DRB region. In the Indian population, however, a reshuffling of existing segments generated “new” haplotypes. Since the recombination frequency within the core MHC of the Indian rhesus macaques is relatively low, the various haplotypes were most probably produced by recombination events that accumulated over a long evolutionary time span. This idea is in accord with the notion that Indian rhesus macaques experienced a severe reduction in population during the Pleistocene due to a bottleneck caused by geographic changes. Thus, recombination-like processes appear to be a way to expand a diminished genetic repertoire in an isolated and relatively small founder population.Electronic supplementary materialThe online version of this article (doi:10.1007/s00251-013-0707-8) contains supplementary material, which is available to authorized users.

Fluctuating asymmetry in populations of British roe deer (Capreolus capreolus) following historical bottlenecks and founder events

The potential impact of population bottlenecks and founder events on genetic diversity and indirect measures of fitness (such as fluctuating asymmetry; FA) has important conservation implications. Here we take advantage of historical events that generated a remnant roe deer (Capreolus capreolus) population in the north of the British Isles that retained diversity, while populations in the south were apparently extirpated during the early mediaeval era. The southern population was later re-established from small founder populations of introduced European roe deer starting in the 19th century. We assess the impact of these events, using the northern remnant population as a reference, based on measures of FA at 16 bilateral cranial traits. Comparing the northern and southern populations we find evidence of differential impact on both the level of FA and the relationship between FA and levels of genetic diversity.

Analysis of genetic structure and growth traits inBarbus capitousing microsatellite markers

Barbus capito is an endemic species in the Aral Sea of Uzbekistan.It is well-known for its salt tolerance and fast growth,and is a valuable food source in the region.The species was introduced to China in 2003 and F1 was obtained using artificial propagation in 2010.As an introduced species,B.capito has the relatively limited genetic resources due to the small founder population size.It is very important to effectively protect and utilize the existing gene resources in breeding practice.In this study,24 microsatellite markers were selected to analyze the genetic structure in cultured F1 population including 96 individuals.A total of 74 alleles were detected and the length of fragments ranged from 109 to 367 bp.The number of alleles per locus was from 2 to 5,and the mean was 3.0833.The effective number of alleles(Ne)ranged from 1.144 5 to 4.626 4 with an average of 2.265 6.The observed heterozygosity(Ho)and the expected heterzygosity(He)varied from 0.135 4 to 1.000 0(mean=0.538 4)and from 0.126 9 to 0.788 1(mean=0.487 2),respectively.The value of polymorphic information content(PIC)was between 0.118 3 and 0.749 0 with an average of 0.428 1,and this result indicated that the level of genetic diversity was moderate(0.25≤PIC0.50).The population accorded with Hardy-Weinberg equilibrium checking by χ2 test except 8 markers including B1,B20,B32,B37,B45,B51,B68,and BC43.In addition,the correlation was analyzed between 24 microsatellite markers and growth traits using the GLM procedure of SPSS 19.0.As a result,there were 8 markers that had a significant(P0.05)impact on growth traits.Six markers including B1,B20,B45,B51,B59,and BC38 had a significant(P0.05)impact on body weight,length,height,and thickness.B26 had a significant(P0.05)impact on body weight,height,and thickness.BC3 had a significant(P0.05)impact on body weight and length.Superior genotypes were obtained using Duncan's multiple comparison.

The origins and genetic distinctiveness of the chamorros of the Marianas Islands: An mtDNA perspective

Archaeological and linguistic evidence suggests the Marianas Islands were settled around 3,600 years before present (ybp) from Island Southeast Asia (ISEA). Around 1,000 ybp latte stone pillars and the first evidence of rice cultivation appear in the Marianas. Both traditions are absent in the rest of prehistoric Oceania. To examine the genetic origins and postsettlement gene flow of Chamorros of the Marianas Islands. To infer the origins of the Chamorros we analyzed ∼360 base pairs of the hypervariable-region 1 (HVS1) of mitochondrial DNA from 105 Chamorros from Guam, Rota, and Saipan, and the complete mitochondrial genome of 32 Guamanian Chamorros, and compared them to lineages from ISEA and neighboring Pacific archipelagoes from the database. Results reveal that 92% of Chamorros belong to haplogroup E, also found in ISEA but rare in Oceania. The two most numerous E lineages were identical to lineages currently found in Indonesia, while the remaining E lineages differed by only one or two mutations and all were unique to the Marianas. Seven percent of the lineages belonged to a single Chamorro-specific lineage within haplogroup B4, common to ISEA as well as Micronesia and Polynesia. These patterns suggest a small founding population had reached and settled the Marianas from ISEA by 4,000 ybp, and developed unique mutations in isolation. A second migration from ISEA may have arrived around 1,000 ybp, introducing the latte pillars, rice agriculture and the homogeneous minority B4 lineage.

Detection of the tropical mussel species Perna viridis in temperate Western Australia: possible association between spawning and a marine heat pulse

In April 2011 a single individual of the invasive mussel Perna viridis was detected on a naval vessel while berthed in the temperate waters of Garden Island, Western Australia (WA). Further examination of this and a nearby vessel revealed a small founder population that had recently established inside one of the vessel’s sea chests. Growth estimates indicated that average size mussels in the sea chest were between 37.1 and 71 days old. Back calculating an ‘establishment date’ from these ages placed an average sized animal’s origins in the summer months of January 2011 to March 2011. This time period corresponded with an unusual heat pulse that occurred along the WA coastline resulting in coastal waters >3 oC above normal. This evidence of a spawning event for a tropical species in temperate waters highlights the need to prepare for more incursions of this kind given predictions of climate change.

When bigger is not better: intraspecific competition for pollination increases with population size in invasive milkweeds

One of the essential requirements for an introduced plant species to become invasive is an ability to reproduce outside the native range, particularly when initial populations are small. If a reproductive Allee effect is operating, plants in small populations will have reduced reproductive success relative to plants in larger populations. Alternatively, if plants in small populations experience less competition for pollination than those in large populations, they may actually have higher levels of reproductive success than plants in large populations. To resolve this uncertainty, we investigated how the per capita fecundity of plants was affected by population size in three invasive milkweed species. Field surveys of seed production in natural populations of different sizes but similar densities were conducted for three pollinator-dependent invasive species, namely Asclepias curassavica, Gomphocarpus fruticosus and G. physocarpus. Additionally, supplemental hand-pollinations were performed in small and large populations in order to determine whether reproductive output was limited by pollinator activity in these populations. Reproductive Allee effects were not detected in any of the study species. Instead, plants in small populations exhibited remarkably high levels of reproductive output compared to those in large populations. Increased fruit production following supplemental hand-pollinations suggested that the lower reproductive output of naturally pollinated plants in large populations is a consequence of pollen limitation rather than limitation due to abiotic resources. This is consistent with increased intraspecific competition for pollination amongst plants in large populations. It is likely that the invasion of these milkweed species in Australia has been enhanced because plants in small founding populations experience less intraspecific competition for pollinators than those in large populations, and thus have the ability to produce copious amounts of seeds.

The relationship between male moth density and female mating success in invading populations of Lymantria dispar

AbstractThe successful establishment of non‐native species in new areas can be affected by many factors including the initial size of the founder population. Populations comprised of fewer individuals tend to be subject to stochastic forces and Allee effects (positive‐density dependence), which can challenge the ability of small founder populations to establish in a new area. Although the conceptual relationship between initial colony size and establishment success has been previously documented, it is not trivial to estimate precisely the colony size needed to ensure colony persistence. Over the last 40 years, there have been many studies on the probability of mating success of female Lymantria dispar (L.) (Lepidoptera: Lymantriidae) in the USA related to background male moth densities. We were motivated by this wealth of data and sought to combine the results from these prior studies with the goal of estimating a robust measure of the male moth density required to achieve varying levels of female mating success. Although the data are specific to L. dispar, the pheromone communication system in L. dispar is not unique and thus the results of this analysis could be broadly applicable to our general understanding of Lepidoptera mating behavior.

Allee effects, aggregation, and invasion success

Understanding the factors that influence successful colonization can help inform ecological theory and aid in the management of invasive species. When founder populations are small, individual fitness may be negatively impacted by component Allee effects through positive density dependence (e.g., mate limitation). Reproductive and survival mechanisms that suffer due to a shortage of conspecifics may scale up to be manifest in a decreased per-capita population growth rate (i.e., a demographic Allee effect). Mean-field population level models are limited in representing how component Allee effects scale up to demographic Allee effects when heterogeneous spatial structure influences conspecific availability. Thus, such models may not adequately characterize the probability of establishment. In order to better assess how individual level processes influence population establishment and spread, we developed a spatially explicit individual-based stochastic simulation of a small founder population. We found that increased aggregation can affect individual fitness and subsequently impact population growth; however, relatively slow dispersal—in addition to initial spatial structure—is required for establishment, ultimately creating a tradeoff between probability of initial establishment and rate of subsequent spread. Since this result is sensitive to the scaling up of component Allee effects, details of individual dispersal and interaction kernels are key factors influencing population level processes. Overall, we demonstrate the importance of considering both spatial structure and individual level traits in assessing the consequences of Allee effects in biological invasions.

Molecular phylogeography of the Japanese weasel, Mustela itatsi (Carnivora: Mustelidae), endemic to the Japanese islands, revealed by mitochondrial DNA analysis

To investigate the process of the population divergence of mammalian species endemic to continental islands, we studied the phylogeography of the Japanese weasel, Mustela itatsi, compared with its closely related continental species, the Siberian weasel M. sibirica, using mitochondrial DNA control region sequences. Mustela itatsi is endemic to the main Japanese islands (Honshu, Shikoku and Kyushu Islands), except Hokkaido Island, whereas M. sibirica is widespread in eastern Asia, southern Siberia, Taiwan and Tsushima Island. Fifty individuals of M. itatsi collected from 19 localities in Japan were examined. For M. sibirica, 27 individuals were analysed: 12 specimens from five localities within native habitats and 15 individuals (from the population introduced to Japan) from eight localities in western Japan. We identified 32 haplotypes for M. itatsi, which were clustered into two main clades (Honshu and Kyushu–Shikoku clades), whereas there were 11 haplotypes for M. sibirica, all of which were clustered into one clade. The grade of genetic differentiation within each clade of M. itatsi was similar to each other and to that of M. sibirica from samples distributed widely across northern Eurasia. The two clades in M. itatsi could have been established as a result of alternative zoogeographical events: geographical isolation of Honshu and Kyushu–Shikoku Islands or independent migration of the two lineages from the continent to Japan at different times. The molecular phylogeographical and demographic analyses indicated that the population of M. itatsi of Honshu Island expanded more recently than those of Kyushu and Shikoku Islands, which could have been refugia in the middle Pleistocene. In addition, the genetic differentiation and population expansion of M. itatsi on the Japanese islands could have occurred earlier than for other mammalian species endemic to Japan. However, the phylogeographical results for M. sibirica showed much less genetic variation through Eurasia, and that the introduced population in western Japan originated from a small founder population from the Korean Peninsula.

Structured growth and genetic drift raise relatedness in the social amoeba Dictyostelium discoideum

One condition for the evolution of altruism is genetic relatedness between altruist and beneficiary, often achieved through active kin recognition. Here, we investigate the power of a passive process resulting from genetic drift during population growth in the social amoeba Dictyostelium discoideum. We put labelled and unlabelled cells of the same clone in the centre of a plate, and allowed them to proliferate outward. Zones formed by genetic drift owing to the small population of actively growing cells at the colony edge. We also found that single cells could form zones of high relatedness. Relatedness increased at a significantly higher rate when food was in short supply. This study shows that relatedness can be significantly elevated before the social stage without a small founding population size or recognition mechanism.

Effects of Potyvirus Effective Population Size in Inoculated Leaves on Viral Accumulation and the Onset of Symptoms

Effective population size (N(e)) is a key parameter for understanding evolutionary processes, but it is generally not considered in epidemiological studies or in studying infections of individual hosts. Whether N(e) has an effect on the onset of symptoms and viral accumulation in Tobacco etch virus (TEV) infection of Nicotiana tabacum plants is considered here. Using mixtures of TEV variants carrying fluorescent markers, the dose dependence of N(e) was confirmed, and the inoculation procedure was found to be the main source of variation in these experiments. Whereas the onset of symptoms was independent of N(e), there was less and more variable accumulation at 6 days postinoculation for small N(e) values (N(e) < 5). The observed variation in accumulation was not heritable, however, suggesting that this variation was not due to the fixation of deleterious mutations in the small founder populations. On the other hand, virus-induced fluorescence and accumulation in the inoculated leaf were strongly N(e) dependent. Systemic accumulation was independent of N(e), although removal of the inoculated leaf led to a small reduction in systemic accumulation for small N(e) values. For whole plants, N(e)-dependent effects on accumulation were no longer observed at 9 days postinoculation. Therefore, the effects of N(e) on accumulation are due mainly to limited expansion in the inoculated leaf and are transient. In this system, N(e)-dependent effects will be strongest at low doses and early in infection. We conclude that N(e) can have implications for epidemiology and infection at the individual host level, beyond determining the rate of mixed-genotype infection.

The People of the Eye: Deaf Ethnicity and Ancestry (review)

The People of the Eye: Deaf Ethnicity and Ancestry, Harlan Lane, Richard C. Pillard, Ulf Hedburg (Oxford: Oxford University Press, 2011, 269 pp., hardcover, $49.95, ISBN 978-0-19-975929-3) THIS VOLUME HAS a double aim. The authors argue for the importance of understanding Deaf people, in this case American Sign Language users, as a distinct ethnic group (Part I). This then frames an in depth history of the Deaf families of New England (Parts II-IV). Starting with the voyage of the Mayflower in 1620, and continuing until about 1640, more than 20,000 colonists, most of them English Puritans, made their way to New England's harsh shores. This small founding population and the practice of intermarriage within extended families including between first cousins led to significant Deaf lineages in New Hampshire, Massachusetts, and Maine. The first known Deaf person of Henniker, New Hampshire, was Nahum Brown, a farmer born in the late 1700s. His Deaf son,Thomas Brown, entered the American Asylum, the school founded by Thomas Gallaudet and Laurent Clerc, at eighteen and was one of the first pupils to graduate. There Thomas Brown met Mary Smith from Martha's Vineyard, Massachusetts. They married and returned to Henniker where they were at the center of an active Deaf community. In 1887, the American Asylum listed forty-four students past and present from the Henniker area. This Deaf enclave became a powerful force in the Deaf institutions of the era. Thomas helped found the New England Gallaudet Association of Deaf-Mutes (NEGA), copublished a newspaper, was director of the Deaf-Mute Library Association, and helped found the New England Industrial School for Deaf Mutes. His Deaf son and nephews followed in his footsteps. The Deaf community of Martha's Vineyard was quite different from that of Henniker. The Vineyard had high rates of intermarriage between just a few families with multiple ties to Deaf ancestors from England's Kentish Weald. This led to high rates of deafness and to a population where both Deaf and hearing people knew sign language. DeafVineyarders lived lives similar to those of their hearing neighbors, sharing professions such as farmer and fisherman, interacting with many of them easily in sign language, and marrying hearing people at a far higher rate than their Deaf counterparts in Henniker. In the late eighteenth century, setders from Martha's Vineyard, including Deaf families, moved to Maine, drawn by inexpensive land and a wealth of natural resources. Parts III and IV describe the important Deaf families of the northern cluster, including the Smith- Parkhurst and Samuel Allen clans, and the Davises, Lovejoys, Jellisons, Jacks, and Berrys, and the southern cluster including the Rogers-Holmes, Badger-Boardwin-Brown-Glidden, and Curtis-Rowe clans. The most interesting parts of these chapters are the glimpses into the everyday lives of Deaf individuals that reveal the close ties between Deaf families and fellow Deaf- Wo rid members. In 1849, Samuel Rowe wrote to his brother-in-law Ebenezer Curtis, saw some former deaf-mutes, viz Homer Smithu, and some old ones I did not remember well. . . .You will laugh at me for I am everyday happy to be in the company with sister PersisD, Lucy M. Reedu [wife of Benjamin RoweD] who works with PersisD, and Lucvd's brother AdinD is in town and works as a printer (p. 155, information in [ ] brackets and d for Deaf from Lane et al.) In 1850, Rebekah Allen met numerous Deaf cousins from Massachusetts and Connecticut at the American Asylum alumni reunion. Sometime around the turn of the twentieth century, Francis Berry had an adulterous affair with Mrs. Isaac Jellison, nee Lydia Lovejoy; their unsanctioned relationship thus bringing together three of large Deaf clans. These small tastes of lives left me wishing for much more. Deaf families are a key part of the authors evidence for Deaf ethnicity which surpasses family in its scope: it evokes a rich history of one's kind and a historic fate across generations (i). …