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Migrational mortality is introduced into the classical single-locus model for migration and selection. Genotype-independent migration follows selection, which may be soft or hard. For soft selection, the effect of mortality on the backward migration matrix is the same as in the Malécot model; for hard selection, some neutral results still hold, but some do not. For two diallelic demes, mortality can increase or decrease the stringency of the condition for protecting an allele from loss. In the discrete-space, continuous-time limit, mortality increases the diagonal elements of the migration rate matrix and decreases its off-diagonal elements. Were it not for the same result in the Malécot model, it would be surprising that mortality does not alter the general diffusion limit for multiple alleles, arbitrary multidimensional migration, and arbitrary selection. [ABSTRACT FROM AUTHOR]

In geographically structured populations, global panmixia can be regarded as the limiting case of long-distance migration. The effect of incorporating partial panmixia into diallelic single-locus clines (i.e., asymptotically stable equilibria) maintained by migration and selection in an isotropic environmental pocket in n dimensions is investigated. The population density is uniform. Migration and selection are both weak; the former is homogeneous and isotropic; the latter is directional. If the scaled panmictic rate β≥1, then the allele favored in the pocket is ultimately lost. For β≥1, a cline is maintained if and only if the scaled radius a of the pocket exceeds a critical value an. For a step-environment without dominance, simple, explicit formulas are derived for a1 and a3, an equation with a unique solution and simple, explicit approximations are deduced for a2. The ratio of the selection coefficients outside and inside the pocket is α. As expected intuitively, the cline becomes more difficult to maintain; i.e., the critical radius an increases for n=1,2,3,... as α, β, or n increases. [ABSTRACT FROM AUTHOR]

Divergent natural selection across a heterogeneous landscape can drive the evolution of locally adapted populations in which phenotypic variation is fine-tuned to the environment. At the molecular level, such processes can be inferred by identifying correlations between genetic variation and environmental variables. We demonstrate that allele length and allele frequency at a regulatory circadian rhythm gene, OtsClock1b, are highly correlated ( R2 = 0.86, P = 1.25 × 10−5) with latitude (a surrogate for photoperiod) in kokanee, the freshwater resident form of sockeye salmon ( Oncorhynchus nerka). Two OtsClock1b alleles were identified that differed in length by seven amino acids, with the frequency of the shorter allele increasing from 50% in southern British Columbia (49° N) to complete fixation in Alaska (62° N). No such associations were detected for neutral microsatellite loci. In addition, a kokanee population sampled from Kamchatka, Russia (55° N) fits within the North American latitudinal cline, suggesting that this pattern may be convergent across large longitudinal spatial scales. This correlation provides evidence that natural selection rather than demographic processes may drive the distribution of genetic variation at OtsClock1b in kokanee. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111, 869-877. [ABSTRACT FROM AUTHOR]

Drosophila ananassae, a desiccation and cold sensitive species, is abundant along the latitudinal gradient of the Indian subcontinent. Analysis of seasonally varying wild-caught flies showed two independent patterns of melanisation: (1) narrow to broad melanic stripes on three anterior abdominal segments only; (2) a novel body color pattern (dark vs. light background). We investigated the degree to which these two melanisation systems vary; first with latitude and secondly among seasons. There is a shallow latitudinal cline for percent striped melanisation as well as for frequency of body color alleles during the rainy season. The frequencies of body color alleles vary significantly across seasons in the northern populations i.e. the light allele occur abundantly (>0.94) during the rainy season while the frequency of the dark allele increases (0.22-0.35) during the dry season causing steeper clines during the dry season. By contrast, the low variations in abdominal stripes showed non-significant changes and the cline was similar across seasons. Furthermore, both types of melanisation patterns showed no plasticity with respect to temperature. The present study also investigated clines related to desiccation, heat and cold stress in D. ananassae females across seasons (rainy and dry) from nine latitudinal populations. The clines for stress related traits changes to steeper and non-linear during the dry season. Thus, latitudinal populations of D. ananassae differ in slope values of clines for stress related traits across seasons. This study reports seasonal changes in latitudinal clines of stress resistance traits as seen in a changing frequency of body color alleles of D. ananassae in northern locality, while in southern localities it remains constant. This is presumably the result of only minor seasonal changes in humidity and temperature in the South, whereas in the North seasonal climatic variability is much higher. [ABSTRACT FROM AUTHOR]

Abstract: In geographically structured populations, global panmixia can be regarded as the limiting case of long-distance migration. The effect of incorporating partial panmixia into diallelic single-locus clines maintained by migration and selection in an unbounded unidimensional habitat is investigated. Migration and selection are both weak. The former is homogenous and isotropic; the latter has no dominance. The population density is uniform. A simple, explicit formula is derived for the maximum value of the scaled panmictic rate for which a cline exists. The former depends only on the asymptotic values of the scaled selection coefficient. If the two alleles have the same average selection coefficient, there exists a unique, globally asymptotically stable cline for every . Otherwise, if , the allele with the greater average selection coefficient is ultimately fixed. If , there exists a unique, globally asymptotically stable cline, and some polymorphism is retained even infinitely far from its center. The gene frequencies at infinity are determined by a continuous-time, two-deme migration-selection model. An explicit expression is deduced for the monotone cline in a step-environment. These results differ fundamentally from those for the classical cline without panmixia. [Copyright &y& Elsevier]