Analysis of a Hybrid Swarm Between Eucalyptus risdonii Hook. F. And E. amygdalina Labill

1985 ◽  
Vol 33 (5) ◽  
pp. 543 ◽  
Author(s):  
BM Potts ◽  
JB Reid
Keyword(s):  
Phenotypic Diversity ◽  
Flowering Phenology ◽  
Hybrid Swarm ◽  
Hybrid Fitness ◽  
Seedling Vigour ◽  
Pure Species ◽  
Closely Related Species ◽  
Intermediate Phenotypes ◽  
Disjunct Populations ◽  
Tasmanian Endemic

E. risdonii is a rare Tasmanian endemic which occurs as a series of small disjunct populations within a more-or-less continuous population of a closely related species, E. amygdalina. In localized areas (e.g. Risdon, Tasmania), patches of high phenotypic diversity are encountered, with individuals encompassing the complete phenotypic range between these two species. Progeny trials indicate a large heritable component to this variation. Open-pollinated progenies from intermediate mothers exhibit greater variability than those from either pure species, which strongly suggests that these intermediate phenotypes are a result of hybridization. Progenies from pure species mothers near a hybrid swarm are more variable than those from pure stands. There is a greater proportion of seedlings which match the artificially produced F1 in open-pollinated progenies from E. amygdalina than from E. risdonii mothers. In addition, progenies from intermediate mothers show a bias toward E. risdonii types, which implies that they are predominantly outcrossing to E. risdonii. This evidence suggests an asymmetrical flow of genes by pollen migration from E. risdonii into the hybrid swarm and surrounding E. amygdalina. Little difference in seedling vigour or mortality occurred between seedlings from the various parental phenotypes, although differences in seed output per capsule and germination were apparent. The specific identity of E. risdonii and E. amygdalina is usually maintained in parapatry by a range of mechanisms including their specific ecological preference, reduced hybrid fitness and differences in flowering phenology. The reasons for the major zones of hybridization occurring at boundaries on ridge tops as opposed to those on the dry slopes are discussed.

Population Dynamics and Regeneration of a Hybrid Zone Between Eucalyptus risdonii Hook-F and E amygdalina Labill

1986 ◽  
Vol 34 (3) ◽  
pp. 305 ◽  
Author(s):  
BM Potts
Keyword(s):  
Hybrid Zone ◽  
Null Point ◽  
Asymmetric Distribution ◽  
Hybrid Swarm ◽  
Population Response ◽  
Pure Species ◽  
Seed Migration ◽  
Hybrid Swarms ◽  
Population Turnover ◽  
Phenotypic Fitness

Regeneration of a hybrid zone between E. amygdalina and E. risdonii and pure species stands following wildfire is reported, as well as the reproductive and vegetative fitness of parental and hybrid phenotypes. E. risdonii phenotypes dominated the seed rain and seedling cohort and there was clearly a marked fitness differential between E. amygdalina and E. risdonii at their boundary. When the F1 type hybrid is in competition with both parental types it is generally reproductively the least fit, although frequently vegetatively vigorous. Reduced fitness appears to extend to advanced generations as hybrid phenotypes tending.toward either species are, on average, less fit than the corresponding parental type. The pattern of phenotypic fitness suggests that the species' boundary is in disequilibrium and it is argued that E. risdonii is invading the range of E. amygdalina by both pollen and seed migration. There is an asymmetric distribution of F1 type hybrids across the boundary and the hybrid swarm examined is being invaded by E. risdonii genes. It is suggested that hybridization may be associated with natural disequilibrium and, where seed migration is limited, boundary movements may be preceded by a wave of hybridization due partly to pollen swamping of the least fit species. Hybrid swarms may develop but, at the boundary of large stands, are probably transitory. There is a marked inertia in the population response to the prevailing selective regime due to the extremely slow population turnover and limited dispersal potential. This is discussed in the broader context of non-equilibrium models where it is argued that dispersal may be the factor limiting population response to perturbation of a shallow environmental gradient. This is due to large geographical shifts in the position of the null point and would be accentuated in a patchy environment where migration as a front is prevented.

On the role of enemies in divergence and diversification of prey: a review and synthesis

2005 ◽  
Vol 83 (7) ◽  
pp. 894-910 ◽  
Author(s):  
Steven M Vamosi
Keyword(s):  
Visual Cues ◽  
Phenotypic Diversity ◽  
Theoretical Models ◽  
Ecological Interactions ◽  
Closely Related Species ◽  
Diversification Rates ◽  
Extinction Rates ◽  
Phenotypic Divergence ◽  
Experimental Approaches

Understanding the contribution of ecological interactions to the origin and maintenance of diversity is a fundamental challenge for ecologists and evolutionary biologists, and one that is currently receiving a great deal of attention. Natural enemies (e.g., predators, parasites, and herbivores) are ubiquitous in food webs and are predicted to have significant impacts on phenotypic diversity and on speciation, and extinction rates of their prey. Spurred by the development of a theoretical framework beginning in the late 1970s, there is now a growing body of literature that addresses the effects of enemy–prey interactions on the evolution of prey. A number of theoretical models predict that enemies can produce phenotypic divergence between closely related species, even in the absence of interspecific competition for resources. Effects on diversification of prey are more variable, and enemies may either enhance or depress speciation and extinction rates of their prey. Empirical evidences from a number of study systems, notably those involving predators and prey in aquatic environments and interactions between insects and flowering plants, confirm both predictions. There is now considerable evidence for the role of enemies, especially those that are size-selective or use visual cues when identifying suitable prey, on phenotypic divergence of sympatric and allopatric taxa. Enemies may spur diversification rates in certain groups under some circumstances, and hinder diversification rates in other cases. I suggest that further research should focus on the role of enemies in diversification of prey, with significant insights likely to be the product of applying traditional experimental approaches and emerging comparative phylogenetic methods.

scholarly journals Limited intrinsic postzygotic reproductive isolation despite chromosomal rearrangements between closely related sympatric species of small ermine moths (Lepidoptera: Yponomeutidae)

2019 ◽  
Vol 128 (1) ◽  
pp. 44-58 ◽  
Author(s):  
Katerina H Hora ◽  
František Marec ◽  
Peter Roessingh ◽  
Steph B J Menken
Keyword(s):  
Reproductive Isolation ◽  
Parental Species ◽  
Meiotic Chromosome ◽  
Chromosomal Rearrangements ◽  
Sympatric Species ◽  
Hybrid Fitness ◽  
New Host ◽  
Closely Related Species ◽  
Postzygotic Reproductive Isolation

Abstract In evolutionarily young species and sympatric host races of phytophagous insects, postzygotic incompatibility is often not yet fully developed, but reduced fitness of hybrids is thought to facilitate further divergence. However, empirical evidence supporting this hypothesis is limited. To assess the role of reduced hybrid fitness, we studied meiosis and fertility in hybrids of two closely related small ermine moths, Yponomeuta padella and Yponomeuta cagnagella, and determined the extent of intrinsic postzygotic reproductive isolation. We found extensive rearrangements between the karyotypes of the two species and irregularities in meiotic chromosome pairing in their hybrids. The fertility of reciprocal F1 and, surprisingly, also of backcrosses with both parental species was not significantly decreased compared with intraspecific offspring. The results indicate that intrinsic postzygotic reproductive isolation between these closely related species is limited. We conclude that the observed chromosomal rearrangements are probably not the result of an accumulation of postzygotic incompatibilities preventing hybridization. Alternative explanations, such as adaptation to new host plants, are discussed.

Genetic status of the putative hybrid swarms of mountain dwarf pine and Scots pine in contact zones of their distribution in Slovakia

Biologia ◽  
2015 ◽  
Vol 70 (10) ◽  
Author(s):  
Peter Maňka ◽  
Andrej Kormuťák ◽  
Martin Galgóci ◽  
Dušan Gömöry
Keyword(s):  
Genetic Structure ◽  
Scots Pine ◽  
Molecular Level ◽  
Natural Populations ◽  
Hybrid Origin ◽  
Putative Hybrid ◽  
Hybrid Swarm ◽  
Pure Species ◽  
Hybrid Swarms ◽  
History Of

AbstractGenetic structure of the mountain dwarf pine (Pinus mugo) and Scots pine (P. sylvestris) natural populations along with their 4 putative hybrid swarms in Slovakia were analyzed using 12 enzyme loci. The study aimed in evaluation of postulated hybrid status of the swarms on molecular level. Based on semidiagnostic allele frequencies of the MDH B, MDH C, 6PGDH B, ADH 1 and F-EST loci in their megagametophytes and vegetative buds, the conspicuous genetic differences were detected between P. mugo and P. sylvestris populations. The putative hybrid swarms seem to incline by their genetic structure to P. mugo rather than to P. sylvestris. Obtained results indicate independent developmental history of each of the scored hybrid swarms. The putative hybrid swarm in Sucha Hora was found to be a mixed stand consisting prevailingly of pure-species individuals of P. mugo and P. sylvestris. On the contrary, the putative hybrid swarms in Habovka, Tisovnica and Terchova are supposed to be of hybrid origin.

scholarly journals Geographical variation in postzygotic isolation and its genetic basis within and between two Mimulus species

2010 ◽  
Vol 365 (1552) ◽  
pp. 2469-2478 ◽  
Author(s):  
Noland H. Martin ◽  
John H. Willis
Keyword(s):  
Pollen Fertility ◽  
Genetic Basis ◽  
Interspecific Cross ◽  
Local Scale ◽  
Interspecific Crosses ◽  
Postzygotic Isolation ◽  
Hybrid Fitness ◽  
Pure Species ◽  
Geographical Scale ◽  
Germination Success

The aim of this study is to investigate the evolution of intrinsic postzygotic isolation within and between populations of Mimulus guttatus and Mimulus nasutus . We made 17 intraspecific and interspecific crosses, across a wide geographical scale. We examined the seed germination success and pollen fertility of reciprocal F 1 and F 2 hybrids and their pure-species parents, and used biometrical genetic tests to distinguish among alternative models of inheritance. Hybrid seed inviability was sporadic in both interspecific and intraspecific crosses. For several crosses, Dobzhansky–Muller incompatibilities involving nuclear genes were implicated, while two interspecific crosses revealed evidence of cytonuclear interactions. Reduced hybrid pollen fertility was found to be greatly influenced by Dobzhansky–Muller incompatibilities in five out of six intraspecific crosses and nine out of 11 interspecific crosses. Cytonuclear incompatibilities reduced hybrid fitness in only one intraspecific and one interspecific cross. This study suggests that intrinsic postzygotic isolation is common in hybrids between these Mimulus species, yet the particular hybrid incompatibilities responsible for effecting this isolation differ among the populations tested. Hence, we conclude that they evolve and spread only at the local scale.

scholarly journals Analysis of the Variability of Floral and Pollen Traits in Apple Cultivars—Selecting Suitable Pollen Donors for Cider Apple Orchards

Agronomy ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1717
Author(s):  
Alvaro Delgado ◽  
Muriel Quinet ◽  
Enrique Dapena
Keyword(s):  
Phenotypic Diversity ◽  
Phenotypic Variability ◽  
Germplasm Collection ◽  
Flowering Phenology ◽  
Floral Biology ◽  
Biennial Bearing ◽  
Oceanic Climate ◽  
Apple Cultivars ◽  
Local Germplasm ◽  
Flowering Intensity

Most apple trees (Malus domestica Borkh.) are self-incompatible and fruit yield depends on cross-pollination between genetically compatible cultivars with synchronous flowering. Flowering intensity can vary strongly among years due to the biennial bearing habit of the cultivars. The knowledge of the phenological stages and floral and pollen characteristics is essential to select suitable pollen donors. We evaluated the phenotypic variability of flowering-related traits (i.e., flowering phenology, flowering intensity, pollen production and pollen quality) in 45 apple cultivars over two successive flowering seasons. Large phenotypic variability was found among the studied cultivars indicating that the local germplasm collection provides a good source of genetic and phenotypic diversity. However, low correlations were observed between floral biology traits and, consequently, the improvement in one trait seems not to affect other traits. Some of the cultivars such as ‘Perurico’ and ‘Raxila Dulce’ regularly produced copious amounts of high-quality pollen which can improve the pollen load dispersion leading to a most effective pollination process. We did not identify statistically significant correlations between pollen attributes and the biennial bearing phenomenon. The large variation in bloom dates from year-to-year observed under a typical Oceanic climate makes it advisable to combine cultivars in new plantings.

scholarly journals Gap genes are involved in inviability in hybrids between Drosophila melanogaster and D. santomea

2021 ◽  
Author(s):  
Wenhan Chang ◽  
Martin Kreitman ◽  
Daniel R. Matute
Keyword(s):  
Drosophila Melanogaster ◽  
Gene Network ◽  
Developmental Process ◽  
Coding Region ◽  
Pure Species ◽  
Closely Related Species ◽  
Hybrid Inviability ◽  
Gap Gene ◽  
Gap Genes ◽  
Anterior Posterior

ABSTRACTEvolved changes within species lead to the inevitable loss of viability in hybrids. Inviability is also a convenient phenotype to genetically map and validate functionally divergent genes and pathways differentiating closely related species. Here we identify the Drosophila melanogaster form of the highly conserved essential gap gene giant (gt) as a key genetic determinant of hybrid inviability in crosses with D. santomea. We show that the coding region of this allele in D. melanogaster/D. santomea hybrids is sufficient to cause embryonic inviability not seen in either pure species. Further genetic analysis indicates that tailless (tll), another gap gene, is also involved in the hybrid defects. giant and tll are both members of the gap gene network of transcription factors that participate in establishing anterior-posterior specification of the dipteran embryo, a highly conserved developmental process. Genes whose outputs in this process are functionally conserved nevertheless evolve over short timescales to cause inviability in hybrids.

scholarly journals Species integrity enhanced by a predation cost to hybrids in the wild

2017 ◽  
Vol 13 (7) ◽  
pp. 20170208 ◽  
Author(s):  
P. Anders Nilsson ◽  
Kaj Hulthén ◽  
Ben B. Chapman ◽  
Lars-Anders Hansson ◽  
Jakob Brodersen ◽  
...  
Keyword(s):  
Related Species ◽  
Parental Species ◽  
Great Cormorant ◽  
Phalacrocorax Carbo ◽  
Hybrid Fitness ◽  
Closely Related Species ◽  
Ecological Selection ◽  
Field Evidence ◽  
In The Wild ◽  
Species Integrity

Species integrity can be challenged, and even eroded, if closely related species can hybridize and produce fertile offspring of comparable fitness to that of parental species. The maintenance of newly diverged or closely related species therefore hinges on the establishment and effectiveness of pre- and/or post-zygotic reproductive barriers. Ecological selection, including predation, is often presumed to contribute to reduced hybrid fitness, but field evidence for a predation cost to hybridization remains elusive. Here we provide proof-of-concept for predation on hybrids being a postzygotic barrier to gene flow in the wild. Cyprinid fishes commonly produce fertile, viable hybrid offspring and therefore make excellent study organisms to investigate ecological costs to hybrids. We electronically tagged two freshwater cyprinid fish species (roach Rutilus rutilus and bream Abramis brama ) and their hybrids in 2005. Tagged fish were returned to their lake of origin, exposing them to natural predation risk from apex avian predators (great cormorant, Phalacrocorax carbo ). Scanning for regurgitated tags under cormorant roosts 3–4 years later identified cormorant-killed individual fish and allowed us to directly test for a predation cost to hybrids in the wild. Hybrid individuals were found significantly more susceptible to cormorant predation than individuals from either parental species. Such ecological selection against hybrids contributes to species integrity, and can enhance species diversification.

scholarly journals The genetic architecture and evolution of life-history divergence among perennials in the Mimulus guttatus species complex

2021 ◽  
Vol 288 (1948) ◽  
Author(s):  
Jenn M. Coughlan ◽  
Maya Wilson Brown ◽  
John H. Willis
Keyword(s):  
Life History ◽  
Species Complex ◽  
Genetic Architecture ◽  
Phenotypic Diversity ◽  
Mimulus Guttatus ◽  
Multiple Traits ◽  
Hybrid Fitness ◽  
Trait Divergence ◽  
Evolution Of Life ◽  
Opposing Effects

Ecological divergence is a fundamental source of phenotypic diversity between closely related species, yet the genetic architecture of most ecologically relevant traits is poorly understood. Differences in elevation can impose substantial divergent selection on both complex, correlated suites of traits (such as life-history), as well as novel adaptations. We use the Mimulus guttatus species complex to assess if the divergence in elevation is accompanied by trait divergence in a group of closely related perennials and determine the genetic architecture of this divergence. We find that divergence in elevation is associated with differences in life-history, as well as a unique trait, the production of rhizomes. The divergence between two perennials is largely explained by few mid-to-large effect quantitative trait loci (QTLs). However, the presence of QTLs with correlated, but opposing effects on multiple traits leads to some hybrids with transgressive trait combinations. Lastly, we find that the genetic architecture of the ability to produce rhizomes changes through development, wherein most hybrids produce rhizomes, but only later in development. Our results suggest that elevational differences may shape life-history divergence between perennials, but aspects of the genetic architecture of divergence may have implications for hybrid fitness in nature.

scholarly journals The genetic architecture and evolution of life history divergence among perennials in the Mimulus guttatus species complex

2020 ◽  
Author(s):  
Jenn M. Coughlan ◽  
Maya Wilson Brown ◽  
J.H. Willis
Keyword(s):  
Life History ◽  
Species Complex ◽  
Genetic Architecture ◽  
Phenotypic Diversity ◽  
Investment Strategies ◽  
Mimulus Guttatus ◽  
Hybrid Fitness ◽  
Trait Divergence ◽  
Phenotypic Divergence ◽  
Overwintering Survival

AbstractEcological divergence is a main source of trait divergence between closely related species. Despite its importance in generating phenotypic diversity, the genetic architecture of most ecologically relevant traits is poorly understood. Differences in elevation can impose substantial selection for phenotypic divergence of both complex, correlated suites of traits (such as life history), as well as novel adaptations. Here, we use the Mimulus guttatus species complex to assess if divergence in elevation is accompanied by trait divergence in a group of closely related perennial species, and determine the genetic architecture of this divergence. We find that divergence in elevation is associated with differences in multivariate quantitative life history traits, as well as a unique trait; the production of rhizomes, which may play an important role in overwintering survival. However, the extent of phenotypic divergence among species depended on ontogeny, suggesting that species also diverged in investment strategies across development. Lastly, we show that the genetic architecture of life history divergence between two species is simple, involving few mid to large effect Quantitative Trait Loci (QTLs), and that the genetic architecture of the ability to produce rhizomes changes through development, which has potential implications for hybrid fitness in the wild.

Sign in / Sign up

Export Citation Format

Share Document