GENE FLOW, REFUGIA, AND EVOLUTION OF GEOGRAPHIC VARIATION IN THE SONG SPARROW (<i>MELOSPIZA MELODIA)</i>

Zink, Robert M.; Dittmann, Donna L.

doi:10.1111/j.1558-5646.1993.tb01228.x

Cited by 104 publications

(53 citation statements)

References 61 publications

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“…Several recent models predict that denser, faster-growing subpopulations in ecologically favorable microhabitats will be "genetic sources" for the recolonization of "genetic sink" subpopulations occupying marginal sites (Pulliam 1988;Holt and Gaines 1992;Kawecki 1995). This prediction seems to match patterns of colonization and genetic variation seen in some field studies in highly heterogeneous habitats (Gill 1978;Zink and Dittmann 1993). It is now recognized that this kind of interaction between migration and selection should impede rapid changes in a species' fundamental niche (Holt and Gaines 1992;Kawecki 1995), but the consequences for genetic structure within populations have been less appreciated.…”

Section: Natural Selection and Effective Gene Flow Across Ecological mentioning

confidence: 69%

POPULATION STRUCTURE ALONG A STEEP ENVIRONMENTAL GRADIENT: CONSEQUENCES OF FLOWERING TIME AND HABITAT VARIATION IN THE SNOW BUTTERCUP, RANUNCULUS ADONEUS

1997

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Few studies have determined how gene flow and selection interact to generate population genetic structure in heterogeneous environments. One way to identify the potential role played by natural selection is to compare patterns of spatial genetic structure between different life cycle stages and among microenvironments. We examined patterns of spatial structure in a population of the snow buttercup (Ranunculus adoneus), using both adult plants and newly emerged seedlings. The study population spans a steep environmental gradient caused by gradual melting of snow within a permanent snowbed. Early-melting sites are characterized by denser vegetation, more fertile soils, and a longer growing season than late-melting sites tens of meters away. The flowering time of R. adoneus is controlled entirely by time of snowmelt, so the contiguous population is phenologically substructured into a series of successively flowering cohorts, reducing the opportunity for direct pollen transfer between early- and late-melting sites. For four highly polymorphic enzyme loci in this tetraploid species, there was subtle, but statistically significant, genetic differentiation between early, middle, and late-melting cohorts; adults usually showed greater differentiation among snowmelt zones than did seedlings. At two loci in adults and one locus in seedlings, homozygotes were more common than predicted at Hardy-Weinberg equilibrium, even when assuming maximum levels of double reduction during meiosis. This pattern suggests the occurrence of self-fertilization and/or population substructure. To determine how spatial isolation and phenological separation each contribute to genetic substructure, we used bivariate regression models to predict the numbers of allele differences between randomly paired individuals as a function of meters separation in space and days separation in flowering time. For newly emerged seedlings, we found that spatial separation was positively associated with genetic difference, but that the additional contribution of phenological separation to genetic difference was not significant. This implies that seeds and/or pollen move effectively across the snowmelt gradient, despite differences in flowering time. As was true for seedlings, spatial separation between paired adults contributed to greater genetic difference, but for a given spatial separation, the genetic difference between adult plants was reduced by phenological separation. This result implies that postemergence selection is favoring at least some seeds that migrate across the snowmelt gradient. Directional gene flow across the snowmelt gradient probably results from a genetic source-sink interaction, that is, the colonization of ecologically marginal late-melting sites by high quality seeds produced by the larger subpopulation in early-melting sites. Effective gene flow from high to low quality microenvironments is likely to impede adaptation to late-melting locations.

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Section: Natural Selection and Effective Gene Flow Across Ecological mentioning

confidence: 69%

POPULATION STRUCTURE ALONG A STEEP ENVIRONMENTAL GRADIENT: CONSEQUENCES OF FLOWERING TIME AND HABITAT VARIATION IN THE SNOW BUTTERCUP, RANUNCULUS ADONEUS

1997

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“…Phylogeographic structure among whitefish (Coregonus clupeaformis) populations in North America revealed four distinct lineages that suggest divergence in isolation in four freshwater refugia (Bernatchez and Dodson 1991). In the highly poly typic song sparrow (Melospiza melodia), the basal haplotypes in the phylogeny implicate Newfoundland and Haida Gwaii as potential sites of glacial refugia in the Wisconsin period, although genotypes were geographically unordered and not concordant with subspecies boundaries (Zink and Dittman 1993). Although the glacial refugium hypothesis for evolutionary diversification is a compelling explanation for the contemporary patterns of genetic variation within these Northern Hemisphere taxa, few studies have explicitly tested this hypothesis as a model for isolation and intraspecific divergence of vertebrate populations.…”

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confidence: 99%

A Test of the Glacial Refugium Hypothesis using Patterns of Mitochondrial and Nuclear DNA Sequence Variation in Rock Ptarmigan (Lagopus mutus)

Holder¹,

Montgomerie²,

Friesen³

1999

Evolution

116

125

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The glacial refugium hypothesis (GRH) proposes that glaciers promoted differentiation and generation of intraspecific diversity by isolating populations in ice-free refugia. We tested three predictions of this hypothesis for the evolutionary divergence of rock ptarmigan (Lagopus mutus) during the Wisconsin glaciation of the late Pleistocene. To do this, we examined subspecies distributions, population genetic structure, and phylogenetic relationships in 26 populations across North America and the Bering Sea region. First, we analyzed sequence variation in the mitochondrial control region, in a nuclear intron (Gapdh), and in an internal transcribed spacer (ITS1). Control region sequences of 154 rock ptarmigan revealed strong population and phylogeographic structure. Variation in intron sequences of 114 rock ptarmigan also revealed significant population structure compatible with results for the control region. Rock ptarmigan were invariant for ITS1. Second, we show that five known Nearctic refugia and an Icelandic refugium are concordant with the current distribution of morphologically distinct subspecies; five of these six refugia are geographically concordant with the distribution of closely related control region haplotypes. Third, our estimates of the time since phylogenetic lineages diverged predated the last glacial maximum for all but two lineages. In addition, all lines of evidence suggest that two unknown refugia in the Bering Sea region supported rock ptarmigan during the Wisconsin glaciation. Overall, our results are most consistent with the hypothesis that isolated populations of rock ptarmigan diverged in multiple refugia during the Wisconsin and that geographic variation reflects patterns of recolonization of the Nearctic after the ice receded. The GRH may therefore offer the most plausible explanation for similar biogeographic patterns in a variety of Nearctic vertebrates.

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“…Geographic variation in plumage pattern has played a prominent role in the development of avian systematics. It has historically been critical in the establishment of specific and subspecific taxonomic boundaries, and in the development and testing of geographic models of avian speciation (Mayr 1942(Mayr , 1963Zink andRemsen 1986, Bensch et al 1999;Zink and Dittmann 1993;Zink 1994;Mayr and Diamond 2001). In spite of its historical importance and near ubiquity among birds, geographic variation in plumage pattern remains largely enigmatic; the evolutionary processes responsible for intra-and interspecific geographic variation in plumage pattern have seldom been investigated experimentally (e.g., Hill 1993;Marchetti 1993;Saetre et al 1997), and they are well understood in relatively few cases (Snow 1954;Aldrich and James 1991;Price and Pavelka 1996;Marchetti and Price 1997;Saetre et al 1997;Hughes et al 2001).…”

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confidence: 99%

Evolutionary Significance of Geographic Variation in a Plumage-Based Foraging Adaptation: An Experimental Test in the Slate-Throated Redstart (Myioborus Miniatus)

Mumme

Galatowitsch

Jabłoński

et al. 2006

Evol

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Geographic variation in the plumage pattern of birds is widespread but poorly understood, and in very few cases has its evolutionary significance been investigated experimentally. Neotropical warblers of the genus Myioborus use their contrasting black-and-white plumage to flush insect prey during animated foraging displays. Although previous experimental work has demonstrated that white plumage patches are critical to flush-pursuit foraging success, the amount of white in the plumage shows considerable interspecific and intraspecific geographic variation. We investigated the evolutionary significance of this geographic variation by experimentally decreasing or increasing the amount of white in the tail of slate-throated redstarts (Myioborus miniatus comptus) from Monteverde, Costa Rica, to mimic the natural extremes of tail pattern variation in this species. In addition to measuring the effects of plumage manipulation on foraging performance, we performed field experiments measuring the escape response of a common insect prey species (an asilid fly) using model redstarts representing four different Myioborus plumage patterns. Our experiments were designed to test four hypotheses that could explain geographic variation in plumage pattern. Compared to controls, experimental birds with reduced-white tails that mimic the plumage pattern of M. miniatus hellmayri of Guatemala showed significant reductions in flush-pursuit foraging performance. In contrast, the addition of white to the tail to mimic the plumage pattern of M. miniatus verticalis of Bolivia had no significant effect on foraging performance of Costa Rican redstarts. In field experiments with asilid flies, model redstarts simulating the plumage of M. miniatus comptus of Costa Rica and M. miniatus verticalis of Bolivia elicited greater responses than did models of other Myioborus taxa with either less or more white in the plumage. The results of our experiments with both birds and insects allow us to reject two hypotheses for geographic variation in plumage pattern: (1) that geographic variation is a nonadaptive result of genetic drift, and (2) that selection for enhanced flush-pursuit foraging performance generally favors increased white in the plumage, but evolutionary trade-offs constrain the evolution of extensive patches of white in some geographic regions. Instead, our results suggest that geographic variation in the plumage pattern of Myioborus redstarts reflects adaptation to regional habitat characteristics that enhances flush-pursuit foraging performance.

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GENE FLOW, REFUGIA, AND EVOLUTION OF GEOGRAPHIC VARIATION IN THE SONG SPARROW (MELOSPIZA MELODIA)

Cited by 104 publications

References 61 publications

POPULATION STRUCTURE ALONG A STEEP ENVIRONMENTAL GRADIENT: CONSEQUENCES OF FLOWERING TIME AND HABITAT VARIATION IN THE SNOW BUTTERCUP, RANUNCULUS ADONEUS

POPULATION STRUCTURE ALONG A STEEP ENVIRONMENTAL GRADIENT: CONSEQUENCES OF FLOWERING TIME AND HABITAT VARIATION IN THE SNOW BUTTERCUP, RANUNCULUS ADONEUS

A Test of the Glacial Refugium Hypothesis using Patterns of Mitochondrial and Nuclear DNA Sequence Variation in Rock Ptarmigan (Lagopus mutus)

Evolutionary Significance of Geographic Variation in a Plumage-Based Foraging Adaptation: An Experimental Test in the Slate-Throated Redstart (Myioborus Miniatus)

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