Evidence for mutation-order speciation inSenecio lautus

In a number of animal species, divergent natural selection has repeatedly and independently driven the evolution of reproductive isolation between populations adapted to contrasting, but not to similar environments1. This process is known as parallel ecological speciation, and examples in plants are enigmatically rare2. Here, we perform a comprehensive test of the ecological speciation hypothesis in an Australian wildflower where parapatric populations found in coastal sand dunes (Dune ecotype) and headlands (Headland ecotype) have repeatedly and independently diverged in growth habit. Consistent with a role for divergent natural selection driving the evolution of reproductive isolation, we found that Dune populations with erect growth habit were easy to transplant across sand dunes, were largely interfertile despite half-a-million years of divergence, and were reproductively isolated from equally divergent Headland populations with prostrate growth habit. However, we unexpectedly discovered that both extrinsic and intrinsic reproductive isolation has evolved between prostrate Headland populations, suggesting that populations evolving convergent phenotypes can also rapidly become new species. Mutation-order speciation2, where the random accumulation of adaptive alleles create genetic incompatibilities between populations inhabiting similar habitats, provides a compelling explanation for these complex patterns of reproductive isolation. Our results suggest that natural selection can drive speciation effectively, but environmental and genetic complexity might make parallel ecological speciation uncommon in plants despite strong morphological convergence.

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Assortative flocking in crossbills and implications for ecological speciation

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2012.1500 ◽

2012 ◽

Vol 279 (1745) ◽

pp. 4223-4229 ◽

Cited By ~ 8

Author(s):

Julie W. Smith ◽

Stephanie M. Sjoberg ◽

Matthew C. Mueller ◽

Craig W. Benkman

Keyword(s):

Natural Selection ◽

Reproductive Isolation ◽

Assortative Mating ◽

Ecological Speciation ◽

Central Question ◽

Loxia Curvirostra ◽

Call Type ◽

Divergent Natural Selection ◽

Contact Calls ◽

Red Crossbills

How reproductive isolation is related to divergent natural selection is a central question in speciation. Here, we focus on several ecologically specialized taxa or ‘call types’ of red crossbills ( Loxia curvirostra complex), one of the few groups of birds providing much evidence for ecological speciation. Call types differ in bill sizes and feeding capabilities, and also differ in vocalizations, such that contact calls provide information on crossbill phenotype. We found that two call types of red crossbills were more likely to approach playbacks of their own call type than those of heterotypics, and that their propensity to approach heterotypics decreased with increasing divergence in bill size. Although call similarity also decreased with increasing divergence in bill size, comparisons of responses to familiar versus unfamiliar call types indicate that the decrease in the propensity to approach heterotypics with increasing divergence in bill size was a learned response, and not a by-product of calls diverging pleiotropically as bill size diverged. Because crossbills choose mates while in flocks, assortative flocking could lead indirectly to assortative mating as a by-product. These patterns of association therefore provide a mechanism by which increasing divergent selection can lead to increasing reproductive isolation.

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Rapid experimental evolution of reproductive isolation from a single natural population

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1901247116 ◽

2019 ◽

Vol 116 (27) ◽

pp. 13440-13445 ◽

Cited By ~ 3

Author(s):

Scott M. Villa ◽

Juan C. Altuna ◽

James S. Ruff ◽

Andrew B. Beach ◽

Lane I. Mulvey ◽

...

Keyword(s):

Body Size ◽

Natural Selection ◽

Reproductive Isolation ◽

Natural Population ◽

Experimental Evolution ◽

Natural Populations ◽

Ecological Speciation ◽

Phenotypic Trait ◽

Divergent Natural Selection ◽

Feather Lice

Ecological speciation occurs when local adaptation generates reproductive isolation as a by-product of natural selection. Although ecological speciation is a fundamental source of diversification, the mechanistic link between natural selection and reproductive isolation remains poorly understood, especially in natural populations. Here, we show that experimental evolution of parasite body size over 4 y (approximately 60 generations) leads to reproductive isolation in natural populations of feather lice on birds. When lice are transferred to pigeons of different sizes, they rapidly evolve differences in body size that are correlated with host size. These differences in size trigger mechanical mating isolation between lice that are locally adapted to the different sized hosts. Size differences among lice also influence the outcome of competition between males for access to females. Thus, body size directly mediates reproductive isolation through its influence on both intersexual compatibility and intrasexual competition. Our results confirm that divergent natural selection acting on a single phenotypic trait can cause reproductive isolation to emerge from a single natural population in real time.

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Ecological Divergence and the Origins of Intrinsic Postmating Isolation with Gene Flow

International Journal of Ecology ◽

10.1155/2011/435357 ◽

2011 ◽

Vol 2011 ◽

pp. 1-15 ◽

Cited By ~ 24

Author(s):

Aneil F. Agrawal ◽

Jeffrey L. Feder ◽

Patrik Nosil

Keyword(s):

Linkage Disequilibrium ◽

Gene Flow ◽

Natural Selection ◽

Theoretical Models ◽

Ecological Speciation ◽

Divergent Selection ◽

Postmating Isolation ◽

Divergent Natural Selection ◽

Mathematical Exploration ◽

Neutral Gene

The evolution of intrinsic postmating isolation has received much attention, both historically and in recent studies of speciation genes. Intrinsic isolation often stems from between-locus genetic incompatibilities, where alleles that function well within species are incompatible with one another when brought together in the genome of a hybrid. It can be difficult for such incompatibilities to originate when populations diverge with gene flow, because deleterious genotypic combinations will be created and then purged by selection. However, it has been argued that if genes underlying incompatibilities are themselves subject to divergent selection, then they might overcome gene flow to diverge between populations, resulting in the origin of incompatibilities. Nonetheless, there has been little explicit mathematical exploration of such scenarios for the origin of intrinsic incompatibilities during ecological speciation with gene flow. Here we explore theoretical models for the origin of intrinsic isolation where genes subject to divergent natural selection also affect intrinsic isolation, either directly or via linkage disequilibrium with other loci. Such genes indeed overcome gene flow, diverge between populations, and thus result in the evolution of intrinsic isolation. We also examine barriers to neutral gene flow. Surprisingly, we find that intrinsic isolation sometimes weakens this barrier, by impeding differentiation via ecologically based divergent selection.

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Extending r/K selection with a maternal risk-management model that classifies animal species into divergent natural selection categories

Scientific Reports ◽

10.1038/s41598-019-42562-7 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 3

Author(s):

Deby L. Cassill

Keyword(s):

Risk Management ◽

Natural Selection ◽

Animal Species ◽

Management Model ◽

Maternal Risk ◽

Divergent Natural Selection

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Assortative mating, sexual selection and their consequences for gene flow in Littorina

10.1101/2020.01.28.922658 ◽

2020 ◽

Author(s):

Samuel Perini ◽

Marina Rafajlović ◽

Anja M. Westram ◽

Kerstin Johannesson ◽

Roger K. Butlin

Keyword(s):

Sexual Selection ◽

Gene Flow ◽

Natural Selection ◽

Reproductive Isolation ◽

Assortative Mating ◽

Small Male ◽

Mating Pattern ◽

Barrier Effects ◽

Divergent Natural Selection ◽

Coastal Marine

AbstractWhen divergent populations are connected by gene flow, the establishment of complete reproductive isolation usually requires the joint action of multiple barrier effects. One example where multiple barrier effects are coupled consists of a single trait that is under divergent natural selection and also mediates assortative mating. Such multiple-effect traits can strongly reduce gene flow. However, there are few cases where patterns of assortative mating have been described quantitatively and their impact on gene flow has been determined. Two ecotypes of the coastal marine snail, Littorina saxatilis, occur in North Atlantic rocky-shore habitats dominated by either crab predation or wave action. There is evidence for divergent natural selection acting on size, and size-assortative mating has previously been documented. Here, we analyze the mating pattern in L. saxatilis with respect to size in intensively-sampled transects across boundaries between the habitats. We show that the mating pattern is mostly conserved between ecotypes and that it generates both assortment and directional sexual selection for small male size. Using simulations, we show that the mating pattern can contribute to reproductive isolation between ecotypes but the barrier to gene flow is likely strengthened more by sexual selection than by assortment.

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Divergent natural selection drives the evolution of reproductive isolation in an Australian wildflower

Evolution ◽

10.1111/evo.12994 ◽

2016 ◽

Vol 70 (9) ◽

pp. 1993-2003 ◽

Cited By ~ 16

Author(s):

Thomas J. Richards ◽

Greg M. Walter ◽

Katrina McGuigan ◽

Daniel Ortiz-Barrientos

Keyword(s):

Natural Selection ◽

Reproductive Isolation ◽

Divergent Natural Selection

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Gradient Evolution of Body Colouration in Surface- and Cave-DwellingPoecilia mexicanaand the Role of Phenotype-Assortative Female Mate Choice

BioMed Research International ◽

10.1155/2013/148348 ◽

2013 ◽

Vol 2013 ◽

pp. 1-15 ◽

Cited By ~ 10

Author(s):

David Bierbach ◽

Marina Penshorn ◽

Sybille Hamfler ◽

Denise B. Herbert ◽

Jessica Appel ◽

...

Keyword(s):

Natural Selection ◽

Reproductive Isolation ◽

Assortative Mating ◽

Ecological Speciation ◽

Divergent Selection ◽

Gradual Change ◽

Cave Fish ◽

Resident Male ◽

Poecilia Mexicana ◽

Body Colouration

Ecological speciation assumes reproductive isolation to be the product of ecologically based divergent selection. Beside natural selection, sexual selection via phenotype-assortative mating is thought to promote reproductive isolation. Using the neotropical fishPoecilia mexicanafrom a system that has been described to undergo incipient ecological speciation in adjacent, but ecologically divergent habitats characterized by the presence or absence of toxic H2S and darkness in cave habitats, we demonstrate a gradual change in male body colouration along the gradient of light/darkness, including a reduction of ornaments that are under both inter- and intrasexual selection in surface populations. In dichotomous choice tests using video-animated stimuli, we found surface females to prefer males from their own population over the cave phenotype. However, female cave fish, observed on site via infrared techniques, preferred to associate with surface males rather than size-matched cave males, likely reflecting the female preference for better-nourished (in this case: surface) males. Hence, divergent selection on body colouration indeed translates into phenotype-assortative mating in the surface ecotype, by selecting against potential migrant males. Female cave fish, by contrast, do not have a preference for the resident male phenotype, identifying natural selection against migrants imposed by the cave environment as the major driver of the observed reproductive isolation.

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Experimental evolution of reproductive isolation from a single natural population

10.1101/436287 ◽

2018 ◽

Author(s):

Scott M. Villa ◽

Juan C. Altuna ◽

James S. Ruff ◽

Andrew B. Beach ◽

Lane I. Mulvey ◽

...

Keyword(s):

Body Size ◽

Natural Selection ◽

Reproductive Isolation ◽

Natural Population ◽

Experimental Evolution ◽

Natural Populations ◽

Ecological Speciation ◽

Phenotypic Trait ◽

Sexual Competition ◽

Feather Lice

Ecological speciation occurs when local adaptation generates reproductive isolation as a by-product of natural selection1–3. Although ecological speciation is a fundamental source of diversification, the mechanistic link between natural selection and reproductive isolation remains poorly understood, especially in natural populations2–6. Here we show that experimental evolution of parasite body size over four years (ca. 60 generations) leads to reproductive isolation in natural populations of feather lice on birds. When lice are transferred to pigeons of different sizes they rapidly evolve differences in body size that are correlated with host size. These size differences trigger mechanical mating isolation between lice that are locally adapted to the different sized hosts. Size differences among lice also influence the outcome of competition between males for access to females. Thus, body size directly mediates reproductive isolation through its influence on both inter-sexual compatibility and intra-sexual competition. Our results confirm that divergent natural selection acting on a single phenotypic trait can cause reproductive isolation to emerge from a single natural population in real time.

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Growth and Branching Responses of Portulaca grandiflora to Foliar Applications of Chemical Growth Regulators

HortScience ◽

10.21273/hortsci.33.3.447c ◽

1998 ◽

Vol 33 (3) ◽

pp. 447c-447

Author(s):

T.J. Banko ◽

M.A. Stefani

Keyword(s):

Growth Regulators ◽

Growth Habit ◽

Stem Elongation ◽

Block Design ◽

Shoot Elongation ◽

Main Shoot ◽

Randomized Complete Block Design ◽

Portulaca Grandiflora ◽

Prostrate Growth ◽

Secondary Shoot

During container production of portulaca, growth of long, prostrate, sparsely branched stems makes handling of plants difficult, and reduces their commercial appeal. Growers prefer to minimize shoot elongation while increasing branching to provide a full, compact plant. The objectives of this study were to evaluate growth regulators for promotion of branching and inhibition of stem elongation. Container-grown plants ≈21 cm in diameter were treated with sprays of ProShear (benzylaminopurine) at 62.4, 125, and 250 ppm; Promalin (benzyaminopurine + gibberellins 4+7) at 125, 250, and 500 ppm; Atrimmec (dikegulac) at 250, 500, and 750 ppm; and Florel (ethephon) at 250, 500, and 750 ppm. These treatments were compared with untreated controls in a randomized complete-block design. Main shoot lengths were measured at 16, 31, and 51 days after treatment (DAT). Numbers of new shoot breaks were counted 16 DAT. The growth habit, that is, tendency to grow upright or prostrate, was also evaluated 16 DAT. The most-effective material for retarding primary shoot elongation and for stimulating secondary shoot development was ProShear. At 16 DAT, 250 ppm ProShear reduced shoot elongation by 25% compared to control plants. This treatment also increased the number of secondary shoot breaks by 143%. Promalin increased the number of new shoot breaks, but it also increased the lengths of all shoots. High rates of Florel and Promalin caused shoots to grow predominantly upright rather then prostrate. ProShear, however, caused more prostrate growth as rate increased.

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