Relative contributions of neutral and non-neutral processes to clinal variation in calyx lobe length in the series Sakawanum (Asarum: Aristolochiaceae)

The origin of the Neogene planktonic foraminifer Globorotalia (Globoconella) pliozea in the subtropical southwest Pacific has been attributed to its isolation resulting from intensification of the Subtropical Divergence (Tasman Front). Oxygen isotopic analyses suggest that, although the Subtropical Divergence may have played a role, the evolution of Gr. (G.) pliozea was facilitated by depth segregation of Gr. (G.) conomiozea morphotypes (low and high conical) during an interval of near-surface warming and increasing thermal gradient. Oxygen isotopic analyses suggest that low conical morphotypes of Gr. (G.) conomiozea inhabited greater depths than high conical morphotypes. Low conical forms of Gr. (G.) conomiozea are considered ancestral to the low conical species, Gr. (G.) pliozea. Oxygen isotopes indicate that Gr. (G.) pliozea inhabited greater depths than its ancestor, Gr. (G.) conomiozea.These data are consistent with depth-parapatric and depth-allopatric models, but not with a sympatric model of speciation. In the allopatric model, reproduction at different water depths acts as a barrier between morphotypes. In the parapatric model, clinal variation along a depth gradient acts as a barrier between morphotypes living at the limits of the gradient. Depth segregation in both models results in genetic isolation and evolutionary divergence. Our data support a correlation between morphological evolution and habitat changes in the Globoconella clade, implying separation of populations as a driving force for morphological evolution.Ecological segregation of morphotypes and species may be related to morphology (height of the conical angle), based on the data from Gr. (G.) conomiozea and Gr. (G.) pliozea. However, morphological differences alone do not necessarily produce depth differences. Large morphological differences between Gr. (G.) pliozea and closely related Gr. (G.) puncticulata did not result in isotopic and therefore depth differences between these species. These species coexisted at the same water depths for nearly 1 m.y. Thus, it is unlikely that the extinction of Gr. (G.) pliozea in the middle Pliocene resulted from competition with Gr. (G.) puncticulata, as previously suggested.

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Influence of niche and neutral processes on fish communities associated with changes in macrophyte rafts along the hydrological cycle

Biologia ◽

10.1007/s11756-021-00747-4 ◽

2021 ◽

Author(s):

Lucena R. Virgilio ◽

Werther Pereira Ramalho ◽

João C. B. Silva ◽

Monik Oliveira da Suçuarana ◽

Rodrigo Souza Gomes ◽

...

Keyword(s):

Hydrological Cycle ◽

Fish Communities ◽

Neutral Processes

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Plant Compartments and Developmental Stages Modulate the Balance between Niche-Based and Neutral Processes in Soybean Microbiome

Microbial Ecology ◽

10.1007/s00248-021-01688-w ◽

2021 ◽

Author(s):

I. Moroenyane ◽

L. Mendes ◽

J. Tremblay ◽

B. Tripathi ◽

É. Yergeau

Keyword(s):

Developmental Stages ◽

Neutral Processes

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Genotypic Variation in C and N Isotope Discrimination Suggests Local Adaptation of Heart-Leaved Willow

Tree Physiology ◽

10.1093/treephys/tpab010 ◽

2021 ◽

Author(s):

Yi Hu ◽

Robert D Guy ◽

Raju Y Soolanayakanahally

Keyword(s):

Isotopic Composition ◽

Local Adaptation ◽

N Uptake ◽

Genotypic Variation ◽

Carbon Isotopic Composition ◽

Genotypic Differences ◽

Clinal Variation ◽

Trade Off ◽

Uptake Efficiency ◽

N Uptake Efficiency

Abstract Plants acquire multiple resources from the environment and may need to adjust and/or balance their respective resource-use efficiencies to maximize grow and survival, in a locally adaptive manner. In this study, tissue and whole-plant carbon isotopic composition (δ13C) and C/N ratios provided long-term measures of use efficiencies for water (WUE) and nitrogen (NUE), and a nitrogen isotopic composition (δ15N) based mass balance model was used to estimate traits related to N uptake and assimilation in heart-leaved willow (Salix eriocephala Michx.). In an initial common garden experiment consisting of 34 populations, we found population level variation in δ13C, C/N and δ15N, indicating different patterns in WUE, NUE and N uptake and assimilation. Although there was no relationship between foliar δ13C and C/N ratios among populations, there was a significant negative correlation between these measures across all individuals, implying a genetic and/or plastic trade-off between WUE and NUE not associated with local adaptation. To eliminate any environmental effect, we grew a subset of 21 genotypes hydroponically with nitrate as the sole N-source, and detected significant variation in δ13C, δ15N and C/N ratios. Variation in δ15N was mainly due to genotypic differences in the nitrate efflux/influx ratio (E/I) at the root. Both experiments suggested clinal variation in δ15N (and thus N uptake efficiency) with latitude of origin, which may relate to water availability and could contribute to global patterns in ecosystem δ15N. There was a tendency for genotypes with higher WUE to come from more water replete sites with shorter and cooler growing seasons. We found that δ13C, C/N, and E/I were not inter-correlated, suggesting that selection of growth, WUE, NUE and N uptake efficiency can occur without trade-off.

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Evidence for Selection at the fused1 Locus of Drosophila americana

Genetics ◽

10.1093/genetics/158.1.279 ◽

2001 ◽

Vol 158 (1) ◽

pp. 279-290 ◽

Cited By ~ 4

Author(s):

Jorge Vieira ◽

Bryant F McAllister ◽

Brian Charlesworth

Keyword(s):

Amino Acid ◽

Sequence Variation ◽

Amino Acid Replacement ◽

Population Subdivision ◽

Amino Acid Substitutions ◽

Clinal Variation ◽

Haplotype Structure ◽

Common Amino Acid ◽

Chromosome Arrangement ◽

Dna Sequence Variation

Abstract We analyze genetic variation at fused1, a locus that is close to the centromere of the X chromosome-autosome (X/4) fusion in Drosophila americana. In contrast to other X-linked and autosomal genes, for which a lack of population subdivision in D. americana has been observed at the DNA level, we find strong haplotype structure associated with the alternative chromosomal arrangements. There are several derived fixed differences at fused1 (including one amino acid replacement) between two haplotype classes of this locus. From these results, we obtain an estimate of an age of ∼0.61 million years for the origin of the two haplotypes of the fused1 gene. Haplotypes associated with the X/4 fusion have less DNA sequence variation at fused1 than haplotypes associated with the ancestral chromosome arrangement. The X/4 haplotypes also exhibit clinal variation for the allele frequencies of the three most common amino acid replacement polymorphisms, but not for adjacent silent polymorphisms. These patterns of variation are best explained as a result of selection acting on amino acid substitutions, with geographic variation in selection pressures.

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GENETIC DIFFERENTIATION BETWEEN GEOGRAPHICALLY DISTANT POPULATIONS OF DROSOPHILA MELANOGASTER

Genetics ◽

10.1093/genetics/101.2.235 ◽

1982 ◽

Vol 101 (2) ◽

pp. 235-256

Author(s):

Rama S Singh ◽

Donal A Hickey ◽

Jean David

Keyword(s):

Drosophila Melanogaster ◽

Genetic Differentiation ◽

Gene Frequency ◽

Natural Populations ◽

Allozyme Variation ◽

Clinal Variation ◽

Significant Genetic Differentiation ◽

African Populations ◽

Latitudinal Clines ◽

North And South

ABSTRACT We have studied allozyme variation at 26 gene loci in nine populations of Drosophila melanogaster originating on five different continents. The distant populations show significant genetic differentiation. However, only half of the loci studied have contributed to this differentiation; the other half show identical patterns in all populations. The genetic differentiation in North American, European and African populations is correlated with the major climatic differences between north and south. These differences arise mainly from seven loci that show gene-frequency patterns suggestive of latitudinal clines in allele frequencies. The clinal variation is such that subtropical populations are more heterozygous than temperate populations. These results are discussed in relation to the selectionist and neutralist hypotheses of genetic variation in natural populations.

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