Amount Of Intraspecific Variation Research Articles

Intraspecific and interspecific variation in floral volatiles over time

Floral volatile organic compounds (VOCs) are traits that influence plant interactions with pollinators and other species. Interspecific and intraspecific variation in traits can strongly influence community and ecosystem processes. Yet, we lack an understanding of patterns of variation in floral VOCs among individuals of a species and across species at the community-level across years, and the degree to which phylogenetic relatedness among species influences these patterns. Such an understanding is crucial to accurately interpret more complex patterns and predict consequences for pollination services and plant reproduction. We measured floral VOCs within forb populations and across forb species in a subalpine meadow in the Northern Rocky Mountains of USA over 3 years. Forb species varied in their per-flower VOC emissions as well as in the composition, originality (distance from community mean) and uniqueness (distance from nearest neighbor) of their floral VOCs. The originality of a species’ floral VOCs tended to be more consistent through time than uniqueness. Although not related to phylogeny, there were species-specific differences in originality and uniqueness which may reflect responses of forbs to differences in environmental conditions among years. Interestingly, while species harbored different amounts of intraspecific variation (dispersion) in floral VOCs, species were relatively consistent in this variation across years, and there was significant phylogenetic signal in intraspecific variation. The implications of this temporal consistency for plant–pollinator interactions deserve further attention. Investigating links between interspecific and intraspecific variation in floral VOCs with pollination services and plant reproductive success will help establish the consequences of variation in this important trait.

Intraspecific variation in semicircular canal morphology—A missing element in adaptive scenarios?

Recent evidence suggests that the amount of intraspecific variation in semicircular canal morphology may, itself, be evidence for varying levels of selection related to locomotor demands. To determine the extent of this phenomenon across taxa, we expand upon previous work by examining intraspecific variation in canal radii and canal orthogonality in a broad sample of strepsirrhine and platyrrhine primates. Patterns of interspecific variation are re-examined in light of intraspecific variation to better understand the resolution at which locomotion can be reconstructed from single individuals. Data was collected from high-resolution CT scans of 14 size-matched, related species. Six of these taxa have existing data on rotational head speeds. The level of intraspecific variation was found to differ in strepsirrhine and in platyrrhine species pairs, with larger ranges of variation generally observed for the slower moving taxon than the faster moving one. Taxa that are classified as relatively agile can to some extent be separated from those who are slower-moving, but only when comparing similarly sized, closely related species with more extreme forms of locomotion. Our findings agree with previous research showing that canal intraspecific variation can fluctuate according to species-specific locomotor behavior and extends this further by identifying behaviors that may be under unusual selective pressure. It also demonstrates the complexity of interpreting inner ear morphology in the context of broadly applicable locomotor "categories" of the kind commonly used in behavioral studies. We suspect that simplified models predicting vestibular sensitivity may be unable to differentiate behaviors when only a single specimen is available.

Intraspecific venom variation in southern African scorpion species of the genera Parabuthus, Uroplectes and Opistophthalmus (Scorpiones: Buthidae, Scorpionidae)

Scorpion venoms comprise cocktails of proteins, peptides, and other molecules used for immobilizing prey and deterring predators. The composition and efficacy of scorpion venoms appears to be taxon-specific due to a coevolutionary arms race with prey and predators that adapt at the molecular level. The taxon-specific components of scorpion venoms can be used as barcodes for species identification if the amount of intraspecific variation is low and the analytical method is fast, inexpensive and reliable. The present study assessed the extent of intraspecific variation in newly regenerated venom collected in the field from geographically separated populations of four southern African scorpion species: three buthids, Parabuthus granulatus (Ehrenberg, 1831), Uroplectes otjimbinguensis (Karsch, 1879), and Uroplectes planimanus (Karsch, 1879), and one scorpionid, Opistophthalmus carinatus (Peters, 1861). Although ion signal patterns were generally similar among venom samples of conspecific individuals from different populations, MALDI-TOF mass spectra in the mass range m/z 700–10,000 revealed only a few ion signals that were identical suggesting that species identification based on simple venom mass fingerprints (MFPs) will be more reliable if databases contain data from multiple populations. In general, hierarchical cluster analysis (HCA) of the ion signals in mass spectra was more reliable for species identification than counts of mass-identical substances in MFPs. The statistical approach revealed conclusive information about intraspecific diversity. In combination with a comprehensive database of MALDI-TOF mass spectra in reflectron mode, HCA may offer a method for rapid species identification based on venom MFPs.

Herbarium specimens show patterns of fruiting phenology in native and invasive plant species across New England.

Patterns of fruiting phenology in temperate ecosystems are poorly understood, despite the ecological importance of fruiting for animal nutrition and seed dispersal. Herbarium specimens represent an under-utilized resource for investigating geographical and climatic factors affecting fruiting times within species, patterns in fruiting times among species, and differences between native and non-native invasive species. We examined over 15,000 herbarium specimens, collected and housed across New England, and found 3159 specimens with ripe fruits, collected from 1849-2013. We examined patterns in fruiting phenology among 37 native and 18 invasive woody plant species common to New England. We compared fruiting dates between native and invasive species, and analyzed how fruiting phenology varies with temperature, space, and time. Spring temperature and year explained a small but significant amount of the variation in fruiting dates. Accounting for the moderate phylogenetic signal in fruiting phenology, invasive species fruited 26 days later on average than native species, with significantly greater standard deviations. Herbarium specimens can be used to detect patterns in fruiting times among species. However,the amount of intraspecific variation in fruiting times explained by temporal, geographic, and climatic predictors is small, due to a combination of low temporal resolution of fruiting specimens and the protracted nature of fruiting.Later fruiting times in invasive species, combined with delays in autumn bird migrations in New England, may increase the likelihood that migratory birds will consume and disperse invasive seeds in New England later into the year.

DNA Barcoding as a Tool for Elucidating Species Delineation in Wide-ranging Species as Illustrated by Owls (Tytonidae and Strigidae)

The mitochondrial cytochrome c-oxidase subunit I (cox1) can serve as a fast and accurate marker for the identification of animal species, and for the discovery of new species across the tree of life. Distinguishing species using this universal molecular marker, a technique known as DNA barcoding, relies on the identifying the gap between intra- and interspecific divergence. One of the difficulties could be wide-ranging, cosmopolitan species that show large amounts of morphological variation. The barn owl Tyto alba is a case in point. It occurs worldwide and varies morphologically, leading to the recognition of many subspecies or, more recently, species. We analysed data from the cox1 gene for 31 individuals of seven subspecies, and compared this with 214 sequences from 29 other owl species. Phylogenetic analysis of the T. alba samples gives very strong support for an Old World alba-clade (three subspecies) and a New World furcata-clade (four subspecies) that are genetically equidistant. The amount of intraspecific variation within each of these clades ranges from 0.66-0.99%, but variation among these clades ranges from 5.33-6.20%. Combined these data suggest that barn owl of the Old World is indeed best considered a separate species different from that of the New World. For combined dataset, sample size of owl species (n between 1 and 21 sequences) increased with geographic range size but we did not find significant relationships between interspecific divergence and sample size or between interspecific divergence and geographic range. For 21/24 species of owls with sample sizes of n ≥4 the maximum interspecific divergences was ≤ 3.00%. However, similar to those found in barn owls, the largest amount of divergence (3.23-4.09%) was present in two other wide-ranging species (Strix nebulosa and Aegolius funereus) raising the possibility of multiple species in other wide-ranging owls as well.

Inter-and intraspecific variation in fern mating systems after long-distance colonization: the importance of selfing

BackgroundPrevious studies on the reproductive biology of ferns showed that mating strategies vary among species, and that polyploid species often show higher capacity for self-fertilization than diploid species. However, the amount of intraspecific variation in mating strategy and selfing capacity has only been assessed for a few species. Yet, such variation may have important consequences during colonization, as the establishment of any selfing genotypes may be favoured after long-distance dispersal (an idea known as Baker's law).ResultsWe examined intra-and interspecific variation in potential for self-fertilization among four rare fern species, of which two were diploids and two were tetraploids: Asplenium scolopendrium (2n), Asplenium trichomanes subsp. quadrivalens (4n), Polystichum setiferum (2n) and Polystichum aculeatum (4n). Sporophyte production was tested at different levels of inbreeding, by culturing gametophytes in isolation, as well as in paired cultures with a genetically different gametophyte. We tested gametophytes derived from various genetically different sporophytes from populations in a recently planted forest colonized through long-distance dispersal (Kuinderbos, the Netherlands), as well as from older, less disjunct populations.Sporophyte production in isolation was high for Kuinderbos genotypes of all four species. Selfing capacity did not differ significantly between diploids and polyploids, nor between species in general. Rather selfing capacity differed between genotypes within species. Intraspecific variation in mating system was found in all four species. In two species one genotype from the Kuinderbos showed enhanced sporophyte production in paired cultures. For the other species, including a renowned out crosser, selfing capacity was consistently high.ConclusionsOur results for four different species suggest that intraspecific variation in mating system may be common, at least among temperate calcicole ferns, and that genotypes with high selfing capacity may be present among polyploid as well as diploid ferns. The surprisingly high selfing capacity of all genotypes obtained from the Kuinderbos populations might be due to the isolated position of these populations. These populations may have established through single-spore colonization, which is only possible for genotypes capable of self-fertilization. Our results therewith support the idea that selection for selfing genotypes may occur during long-distance colonization, even in normally outcrossing, diploid ferns.

A small ichthyosaur from the Clearwater Formation (Alberta, Canada) and a discussion of the taxonomic utility of the pectoral girdle

Albian sedimentary successions of northwestern Canada have yielded a diverse assemblage of Mesozoic marine vertebrates, and ichthyosaurs form an important component of these faunas. Here, we describe a partial postcranial skeleton of a small (estimated at less than 3 m total body length) ichthyosaur from the Wabiskaw Member of the Clearwater Formation (lowermost Albian). The semi-articulated specimen includes much of the presacral vertebral column, dorsal ribs and gastralia. Most significantly, it possesses an articulated pectoral girdle and humerus, and also preserves the pelvic girdle, allowing new insights into girdle evolution in ichthyosaurs. Whereas both sets of girdles are thought to exhibit large amounts of intraspecific variation, the pectoral girdle of ophthalmosaurids appears to evolve very slowly, remaining essentially unchanged from the Middle Jurassic onwards. In contrast, the pelvic girdle shows taxonomically informative changes within Ophthalmosauridae. The variable and poorly known nature of girdle morphology in Cretaceous ichthyosaurs precludes generic referral of the specimen.

Including intraspecific variability in functional diversity

Linking species and ecosystems often relies on approaches that consider how the traits exhibited by species affect ecosystem processes. One method is to estimate functional diversity (FD) based on the dispersion of species in functional trait space. Individuals within a species also differ, however, and an unresolved challenge is how to include such intraspecific variability in a measure of functional diversity. Our solution is to extend an existing measure to variation among individuals within species. Here, simulations demonstrate how the new measure behaves relative to one that does not include individual variation. Individual-level FD was less well associated with species richness than species-level FD in a single trait dimension, because species differed in their intraspecific variation. However, in multiple trait dimensions, there was a strong association between individual- and species-level FD and richness, because many traits result in a tight relationship between functional diversity and species richness. The correlation between the two FD measures weakened as the amount of intraspecific variability increased. Analyzing natural plant communities we found no relationship between species richness and functional diversity. In these analyses, we did not have to specify the source of intraspecific variation. In fact, the variation was only among individuals. The measure can, however, include differences in the amount of intraspecific variation at different sites, as we demonstrate. Including intraspecific variation should allow a more complete understanding of the processes that link individuals and ecosystems and provide better predictions about the consequences of extinctions for ecosystem processes.

Molecular phylogeny of the Drosophila auraria species complex and allied species of Japan based on nuclear and mitochondrial DNA sequences

We studied the phylogenetic relationships among the six species of the Drosophila auraria species complex and three species of the montium species subgroup endemic to Japan. To do this, we examined the DNA sequences of the nuclear ITS1 and the mitochondrial COII of these species. Intraspecific variation in ITS1 was observed for most of the species studied. However, interspecific variation was small and of the same magnitude as intraspecific variation among D. auraria, D. triauraria, and D. quadraria. In addition, the amount of intraspecific variation between COII sequences from D. auraria and D. triauraria was almost the same as that of the interspecific variation between these species. Phylogenetic trees based on ITS1 or COII data reveal that, with the exception of D. pectinifera, these species can be separated into two taxonomic groups. D. rufa formed a taxonomic lineage with two Japanese endemic species, D. asahinai and D. lacteicornis. Physiological and behavioral differences between D. auraria and D. triauraria have been reported, but our results differed from those previously reported. Such differences may be better explained by hybridization between D. auraria and D. triauraria than by similarity due to recent common ancestry. Both the ITS1- and COII-based phylogenetic trees placed D. pectinifera outside the auraria complex. However, D. pectinifera sequences were more similar to those of the auraria complex than those of D. punjabiensis, another species thought to be closely related to members of the auraria complex.

Evolution of a HOXB6 intergenic region within the great apes and humans

Data accumulated over the past decade from several loci suggest that nonhuman primates have a greater amount of intraspecific genetic variation relative to humans. In phylogenetic reconstructions among primates that are based on genetic data, therefore, it becomes essential to adequately sample the population(s) being analyzed. Inadequate sampling may not only underestimate variation within any given population, but such an underestimate may confound any phylogenetic or population-specific conclusions implied by the data. Here we present inter- and intraspecific data on the molecular evolution of an approximately 1·0kb intergenic HOXB6 sequence among humans, common chimpanzees, pygmy chimpanzees, gorillas and orang-utans. To date, this study represents the most comprehensive investigation of a noncoding nuclear locus among the great apes and humans that examines the nature and amount of intraspecific variation in DNA sequences. Not only do these HOXB6 data continue to support earlier findings thatHomo sapiens sapienshas less genetic variation than any great ape species (Ruanoet al., 1992; Deinard & Kidd, 1995), but they strongly suggest that a high level of genetic polymorphism existed within the common ancestor of the African ape clade (Homo–Pan–Gorilla). Despite detecting two nucleotide substitutions linkingPanandHomo, we caution against concluding that the HOXB6 data definitively support aHomo–Panclade to the exclusion ofGorilla. Rather, we believe that taking into consideration the level of genetic polymorphism that is likely to have existed within the common ancestor, the most prudent conclusion that can be made from all available data, including morphological, karyotypic and genetic data, may be that speciation amongHomo–Pan–Gorillais best represented by a “trichotomy”.

Intraspecific variation in population gene diversity and effective population size correlates with the mating system in plants.

Published data on allele frequencies at isozyme loci in inbreeding and outbreeding plant species were analyzed to examine intraspecific variation in gene diversity and effective population size (Ne). Compared with outbreeders, inbreeding species showed markedly greater variation among populations in average values of Nei's gene diversity statistic. Effective population size was estimated by assuming that the variation observed at isozyme loci is selectively neutral. Inbreeding species showed greater levels of variation in Ne than did outbreeders, although the upper range of Ne was similar in the two classes of species. The results suggest that there may be considerable genetic variation and potential for evolutionary change in some but not all populations of inbreeders. Moreover, these findings are important with respect to the conservation of genetic resources. In particular, that the amount of intraspecific variation in population genetic diversity and Ne differs between inbreeding and outbreeding species should be taken into account in sampling efforts designed to optimize the diversity of germplasm collections.

Allozyme variation and differentiation in African and Indian rhinoceroses.

We studied variation at 25 to 31 allozymic loci in African and Asian rhinoceroses. Four taxa in three genera were examined: African Ceratotherium simum simum (northern white rhinoceros), C. s. cottoni (southern white rhinoceros), Diceros bicornis (black rhinoceros), and Rhinoceros unicornis (Indian rhinoceros). Extremely small amounts of intraspecific variation were observed in sample sizes of 2 to 10 presumably unrelated individuals per taxon: P = .00-.10, H = 0.00-0.02. We examined demographic bottlenecks and sampling errors as possible reasons for the low levels of detectable variation. The very small intraspecific genetic distance (D = 0.005) between the two living white rhinoceros subspecies is far less than the distance that has been reported for other mammal subspecies. The mean D value of 0.32 +/- 0.11 between the two African genera was also less than expected given the divergence time of greater than 7 million years suggested by the fossil record. Rhinoceroses may be evolving more slowly at the structural gene loci than are some other mammal groups. The estimate of D = 1.05 +/- 0.24 for the African-Indian split supports this idea, as the lineage diverged at least 26 million years ago. Our results contribute to the currently available scientific information on which management decisions aimed toward saving endangered rhinoceroses should be based.

Interspecific Discontinuity in the Genus Clavispora Rodrigues de Miranda by Phenetic Analysis, Genomic Deoxyribonucleic Acid Reassociation, and Restriction Mapping of Ribosomal Deoxyribonucleic Acid

Heterothallic strains belonging to the biologically distinct yeast species Clavispora opuntiae and Clavispora lusitaniae were studied by three different methods. The type cultures of the two yeast species exhibited 8% relatedness as measured by reassociation of unique deoxyribonucleic acid. Ten strains of C. opuntiae and nine strains of C. lusitaniae were compared on the basis of their physiological phenotypes and the restriction maps of their ribosomal deoxyribonucleic acid (rDNAs). Although the two species possessed many similarities as well as certain amounts of intraspecific variation by both approaches, they appeared to constitute well-defined entities. Unlike C. opuntiae, C. lusitaniae always utilized l-rhamnose as the sole carbon source and was resistant to 10 mg of cycloheximide per liter. Strains of C. opuntiae did not utilize l-lysine as the sole nitrogen source or utilized it very weakly, whereas all strains of C. lusitaniae grew rapidly on this compound. By contrast, the hydrolysis of Tween 80 and the utilization of lactic acid, citric acid, and hexadecane tended to be more pronounced in C. opuntiae. The rDNA repeating unit was 9.0 kilobases long in C. lusitaniae, as compared with 7.6 kilobases in C. opuntiae. The conserved region identified previously in the rDNA of C. opuntiae was found almost intact in the rDNA of C. lusitaniae, but the variable regions differed substantially between the two species.

Leaf conductance responses of Viola species from sun and shade habitats

The diurnal pattern of leaf conductance was measured extensively for two Viola species from New England forest and meadow habitats throughout the growing season. The amount of light available to the two species constituted the major micrometeorological difference between their habitats. In the forest, light intensity was highly variable and composed of low-intensity, foliage-filtered light with brief, periodic bursts of high-intensity sun flecks. These contributed less than 25% of total photosynthetically active radiation reaching the forest floor. Comparatively unobstructed, high-intensity light was measured at the meadow site. The forest canopy also buffered air temperature to a greater extent than the grass and shrub vegetation in the meadow, although leaf temperatures in the forest increased briefly during sun flecks. High morning conductance values decreased during the day, perhaps in response to increasing heat load (meadow species) or decreasing light levels (forest species) during the late afternoon. A greater amount of intraspecific variation in leaf conductance was detected for the forest species than for the meadow species. No water stress was observed for either species.

The Subgenus Pompilinus in Mexico (Hymenoptera, Pompilidae)

The subgenus Pompilinus of the genus Anoplius is widely distributed throughout most of the globe, but appears to be best represented in the Nearctic region, where there are about twenty species and subspecies. The group is a difficult one, the differences between the species being slight and often rather subtle, while the amount of intraspecific variation is often not inconsiderable. I believe that future refinements in the systematics of the group will come from comparative ethological studies. However, additional distributional data are also of value, and for this reason a review of the Mexican fauna of Pompilinus is presented at this time. Mexican records were omitted from the writer's recent revision of this group (Evans, 1951, pp. 277–325) for the simple reason that material from that country was then unavailable. The greater part of Mexico is a legitimate part of the Nearctic zoogeographical region, and in fact the Mexican highlands have played an important role in the distribution patterns of many North American Hymenoptera.