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1.
Mol Ecol ; 28(9): 2155-2172, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30937976

RESUMO

Inferring the processes underlying spatial patterns of genomic variation is fundamental to understand how organisms interact with landscape heterogeneity and to identify the factors determining species distributional shifts. Here, we use genomic data (restriction site-associated DNA sequencing) to test biologically informed models representing historical and contemporary demographic scenarios of population connectivity for the Iberian cross-backed grasshopper Dociostaurus hispanicus, a species with a narrow distribution that currently forms highly fragmented populations. All models incorporated biological aspects of the focal taxon that could hypothetically impact its geographical patterns of genomic variation, including (a) spatial configuration of impassable barriers to dispersal defined by topographic landscapes not occupied by the species; (b) distributional shifts resulting from the interaction between the species bioclimatic envelope and Pleistocene glacial cycles; and (c) contemporary distribution of suitable habitats after extensive land clearing for agriculture. Spatiotemporally explicit simulations under different scenarios considering these aspects and statistical evaluation of competing models within an Approximate Bayesian Computation framework supported spatial configuration of topographic barriers to dispersal and human-driven habitat fragmentation as the main factors explaining the geographical distribution of genomic variation in the species, with no apparent impact of hypothetical distributional shifts linked to Pleistocene climatic oscillations. Collectively, this study supports that both historical (i.e., topographic barriers) and contemporary (i.e., anthropogenic habitat fragmentation) aspects of landscape composition have shaped major axes of genomic variation in the studied species and emphasizes the potential of model-based approaches to gain insights into the temporal scale at which different processes impact the demography of natural populations.


Assuntos
Genética Populacional , Gafanhotos/genética , Modelos Genéticos , Animais , Variação Genética , Gafanhotos/fisiologia , Espanha , Análise Espaço-Temporal
2.
Mol Ecol ; 27(5): 1229-1244, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29411440

RESUMO

Although resolving phylogenetic relationships and establishing species limits are primary goals of systematics, these tasks remain challenging at both conceptual and analytical levels. Here, we integrated genomic and phenotypic data and employed a comprehensive suite of coalescent-based analyses to develop and evaluate competing phylogenetic and species delimitation hypotheses in a recent evolutionary radiation of grasshoppers (Chorthippus binotatus group) composed of two species and eight putative subspecies. To resolve the evolutionary relationships within this complex, we first evaluated alternative phylogenetic hypotheses arising from multiple schemes of genomic data processing and contrasted genetic-based inferences with different sources of phenotypic information. Second, we examined the importance of number of loci, demographic priors, number and kind of phenotypic characters and sex-based trait variation for developing alternative species delimitation hypotheses. The best-supported topology was largely compatible with phenotypic data and showed the presence of two clades corresponding to the nominative species groups, one including three well-resolved lineages and the other comprising a four-lineage polytomy and a well-differentiated sister taxon. Integrative species delimitation analyses indicated that the number of employed loci had little impact on the obtained inferences but revealed the higher power provided by an increasing number of phenotypic characters and the usefulness of assessing their phylogenetic information content and differences between sexes in among-taxa trait variation. Overall, our study highlights the importance of integrating multiple sources of information to test competing phylogenetic hypotheses and elucidate the evolutionary history of species complexes representing early stages of divergence where conflicting inferences are more prone to appear.


Assuntos
Evolução Biológica , Genoma , Gafanhotos/genética , Fenótipo , Animais , Análise por Conglomerados , Biologia Computacional , Genótipo , Gafanhotos/anatomia & histologia , Gafanhotos/classificação , Filogenia , Especificidade da Espécie
3.
Mol Phylogenet Evol ; 118: 343-356, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-29080673

RESUMO

Understanding the consequences of past environmental changes on the abiotic and biotic components of the landscape and deciphering their impacts on the demographic trajectories of species is a major issue in evolutionary biogeography. In this study, we combine nuclear and mitochondrial genetic data to study the phylogeographical structure and lineage-specific demographic histories of the scrub-legume grasshopper (Chorthippus binotatus binotatus), a montane taxon distributed in the Iberian Peninsula and France that exclusively feeds on certain scrub-legume species. Genetic data and paleo-distribution modelling indicate the presence of four main lineages that seem to have diverged in allopatry and long-term persisted in Iberian and French refugia since the Mid Pleistocene. Comparisons of different demographic hypotheses in an Approximate Bayesian Computation (ABC) framework supported a population bottleneck in the northwestern French clade and paleo-distribution modelling indicate that the populations of this lineage have experienced more severe environmental fluctuations during the last 21 000 years than those from the Iberian Peninsula. Accordingly, we found that nuclear genetic diversity of the populations of scrub-legume grasshopper is positively associated with local stability of suitable habitats defined by both Pleistocene climate changes and historical distributional shifts of host-plant species. Overall, our study highlights the importance of integrating the potential effects of abiotic (i.e. climate and geography) and biotic components (i.e. inter-specific interactions) into the study of the evolutionary and demographic history of specialist taxa with narrow ecological requirements.


Assuntos
Variação Genética , Gafanhotos/genética , Animais , Teorema de Bayes , Mudança Climática , DNA/isolamento & purificação , DNA/metabolismo , Ecossistema , Complexo IV da Cadeia de Transporte de Elétrons/química , Complexo IV da Cadeia de Transporte de Elétrons/genética , França , Genética Populacional , Gafanhotos/classificação , Desequilíbrio de Ligação , Filogenia , Filogeografia
4.
BMC Evol Biol ; 17(1): 109, 2017 05 04.
Artigo em Inglês | MEDLINE | ID: mdl-28472922

RESUMO

BACKGROUND: The combination of model-based comparative techniques, disparity analyses and ecomorphological correlations constitutes a powerful method to gain insight into the evolutionary mechanisms that shape morphological variation and speciation processes. In this study, we used a time-calibrated phylogeny of 70 Iberian species of short-horned grasshoppers (Acrididae) to test for patterns of morphological disparity in relation to their ecology and phylogenetic history. Specifically, we examined the role of substrate type and level of ecological specialization in driving different aspects of morphological evolution (locomotory traits, chemosensitive organs and cranial morphology) in this recent radiation. RESULTS: We found a bimodal distribution of locomotory attributes corresponding to the two main substrate type guilds (plant vs. ground); plant-perching species tend to exhibit larger wings and thicker femora than those that remain on the ground. This suggests that life form (i.e., substrate type) is an important driving force in the evolution of morphological traits in short-horned grasshoppers, irrespective of ancestry. Substrate type and ecological specialization had no significant influence on head shape, a trait that showed a strong phylogenetic conservatism. Finally, we also found a marginal significant association between the length of antennae and the level of ecological specialization, suggesting that the development of sensory organs may be favored in specialist species. CONCLUSIONS: Our results provide evidence that even in taxonomic groups showing limited morphological and ecological disparity, natural selection seems to play a more important role than genetic drift in driving the speciation process. Overall, this study suggests that morphostatic radiations should not necessarily be considered as "non-adaptive" and that the speciation process can bind both adaptive divergence mechanisms and neutral speciation processes related with allopatric and/or reproductive isolation.


Assuntos
Gafanhotos/anatomia & histologia , Gafanhotos/classificação , Animais , Antenas de Artrópodes/anatomia & histologia , Evolução Biológica , Ecologia , Feminino , Especiação Genética , Gafanhotos/genética , Masculino , Filogenia , Crânio/anatomia & histologia
5.
BMC Evol Biol ; 16: 96, 2016 May 05.
Artigo em Inglês | MEDLINE | ID: mdl-27149952

RESUMO

BACKGROUND: Understanding the underlying processes shaping spatial patterns of genetic structure in free-ranging organisms is a central topic in evolutionary biology. Here, we aim to disentangle the relative importance of neutral (i.e. genetic drift) and local adaptation (i.e. ecological divergence) processes in the evolution of spatial genetic structure of the Morales grasshopper (Chorthippus saulcyi moralesi), a narrow-endemic taxon restricted to the Central Pyrenees. More specifically, we analysed range-wide patterns of genetic structure and tested whether they were shaped by geography (isolation-by-distance, IBD), topographic complexity and present and past habitat suitability models (isolation-by-resistance, IBR), and environmental dissimilarity (isolation-by-environment, IBE). RESULTS: Different clustering analyses revealed a deep genetic structure that was best explained by IBR based on topographic complexity. Our analyses did not reveal a significant role of IBE, a fact that may be due to low environmental variation among populations and/or consequence of other ecological factors not considered in this study are involved in local adaptation processes. IBR scenarios informed by current and past climate distribution models did not show either a significant impact on genetic differentiation after controlling for the effects of topographic complexity, which may indicate that they are not capturing well microhabitat structure in the present or the genetic signal left by dispersal routes defined by habitat corridors in the past. CONCLUSIONS: Overall, these results indicate that spatial patterns of genetic variation in our study system are primarily explained by neutral divergence and migration-drift equilibrium due to limited dispersal across abrupt reliefs, whereas environmental variation or spatial heterogeneity in habitat suitability associated with the complex topography of the region had no significant effect on genetic discontinuities after controlling for geography. Our study highlights the importance of considering a comprehensive suite of potential isolating mechanisms and analytical approaches in order to get robust inferences on the processes promoting genetic divergence of natural populations.


Assuntos
Genes de Insetos , Gafanhotos/genética , Animais , Clima , Análise por Conglomerados , Ecossistema , Evolução Molecular , França , Fluxo Gênico , Deriva Genética , Variação Genética , Repetições de Microssatélites , Modelos Genéticos , Filogeografia
6.
Mol Ecol ; 24(23): 5796-812, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26475782

RESUMO

Conservation plans can be greatly improved when information on the evolutionary and demographic consequences of habitat fragmentation is available for several codistributed species. Here, we study spatial patterns of phenotypic and genetic variation among five grasshopper species that are codistributed across a network of microreserves but show remarkable differences in dispersal-related morphology (body size and wing length), degree of habitat specialization and extent of fragmentation of their respective habitats in the study region. In particular, we tested the hypothesis that species with preferences for highly fragmented microhabitats show stronger genetic and phenotypic structure than codistributed generalist taxa inhabiting a continuous matrix of suitable habitat. We also hypothesized a higher resemblance of spatial patterns of genetic and phenotypic variability among species that have experienced a higher degree of habitat fragmentation due to their more similar responses to the parallel large-scale destruction of their natural habitats. In partial agreement with our first hypothesis, we found that genetic structure, but not phenotypic differentiation, was higher in species linked to highly fragmented habitats. We did not find support for congruent patterns of phenotypic and genetic variability among any studied species, indicating that they show idiosyncratic evolutionary trajectories and distinctive demographic responses to habitat fragmentation across a common landscape. This suggests that conservation practices in networks of protected areas require detailed ecological and evolutionary information on target species to focus management efforts on those taxa that are more sensitive to the effects of habitat fragmentation.


Assuntos
Ecossistema , Variação Genética , Genética Populacional , Gafanhotos/classificação , Animais , Conservação dos Recursos Naturais , Genótipo , Gafanhotos/genética , Repetições de Microssatélites , Modelos Genéticos , Dados de Sequência Molecular , Fenótipo , Filogenia , Dinâmica Populacional , Espanha
7.
Zootaxa ; (3797): 65-77, 2014 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-24870858

RESUMO

The genus Apteromantis Werner, 1931 comprises two species of wingless mantids, the Iberian A. aptera (Fuente, 1894) and the North African A. bolivari (Werner, 1929). Although A. aptera and A. bolivari have been traditionally considered as separate and valid species, their external appearance is quite similar and no comprehensive taxonomic study has analyzed their morphological and genetic characteristics. This taxonomic uncertainty has important implications for conservation because A. aptera is considered an Iberian endemic and the only praying mantis protected by international laws. In this study, we apply a comprehensive approach, including quantitative morphological and molecular analyses, to shed new light on the taxonomic and conservation status of the genus Apteromantis and the putative species. We have found that the Iberian and North African specimens analyzed herein significantly differ in female head shape, male genitalia morphology and several other traits related to body size. Molecular data suggest the presence of two main lineages, with sequence divergence rates of approximately 4 %, which are within the range reported for other well defined insect species. Overall, this study supports that A. aptera and A. bolivari are valid species despite their ecological and morphological similarity and highlights the importance of comprehensive approaches to resolve old taxonomic and conservation problems.


Assuntos
Conservação dos Recursos Naturais , Mantódeos/anatomia & histologia , Mantódeos/classificação , Animais , Feminino , Masculino , Mantódeos/genética , Mantódeos/fisiologia , Filogenia , Especificidade da Espécie
8.
Mol Ecol ; 19(3): 472-83, 2010 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-20051009

RESUMO

The genetic consequences of population fragmentation and isolation are major issues in conservation biology. In this study we analyse the genetic variability and structure of the Iberian populations of Mioscirtus wagneri, a specialized grasshopper exclusively inhabiting highly fragmented hypersaline low grounds. For this purpose we have used seven species-specific microsatellite markers to type 478 individuals from 24 localities and obtain accurate estimates of their genetic variability. Genetic diversity was relatively low and we detected genetic signatures suggesting that certain populations of M. wagneri have probably passed through severe demographic bottlenecks. We have found that the populations of this grasshopper show a strong genetic structure even at small geographical scales, indicating that they mostly behave as isolated populations with low levels of gene flow among them. Thus, several populations can be regarded as independent and genetically differentiated units which require adequate conservation strategies to avoid eventual extinctions that in highly isolated localities are not likely to be compensated for with the arrival of immigrants from neighbouring populations. Overall, our results show that these populations probably represent the 'fragments' of a formerly more widespread population and highlight the importance of protecting Iberian hypersaline environments due to the high number of rare and endangered species they sustain.


Assuntos
Variação Genética , Genética Populacional , Gafanhotos/genética , Alelos , Animais , Teorema de Bayes , Análise por Conglomerados , Fluxo Gênico , Genótipo , Geografia , Repetições de Microssatélites , Portugal , Análise de Componente Principal , Espanha
9.
Ecol Evol ; 10(9): 3991-4008, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32489626

RESUMO

Understanding the processes that shape neutral and adaptive genomic variation is a fundamental step to determine the demographic and evolutionary dynamics of pest species. Here, we use genomic data obtained via restriction site-associated DNA sequencing to investigate the genetic structure of Moroccan locust (Dociostaurus maroccanus) populations from the westernmost portion of the species distribution (Iberian Peninsula and Canary Islands), infer demographic trends, and determine the role of neutral versus selective processes in shaping spatial patterns of genomic variation in this pest species of great economic importance. Our analyses showed that Iberian populations are characterized by high gene flow, whereas the highly isolated Canarian populations have experienced strong genetic drift and loss of genetic diversity. Historical demographic reconstructions revealed that all populations have passed through a substantial genetic bottleneck around the last glacial maximum (~21 ka BP) followed by a sharp demographic expansion at the onset of the Holocene, indicating increased effective population sizes during warm periods as expected from the thermophilic nature of the species. Genome scans and environmental association analyses identified several loci putatively under selection, suggesting that local adaptation processes in certain populations might not be impeded by widespread gene flow. Finally, all analyses showed few differences between outbreak and nonoutbreak populations. Integrated pest management practices should consider high population connectivity and the potential importance of local adaptation processes on population persistence.

10.
Proc Biol Sci ; 275(1646): 2039-47, 2008 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-18505717

RESUMO

The genetic consequences of small population size and isolation are of central concern in both population and conservation biology. Organisms with a metapopulation structure generally show effective population sizes that are much smaller than the number of mature individuals and this can reduce genetic diversity especially in small sized and isolated subpopulations. Here, we examine the association between heterozygosity and the size and spatial isolation of natal colonies in a metapopulation of lesser kestrels (Falco naumanni). For this purpose, we used capture-mark-recapture data to determine the patterns of immigration into the studied colonies, and 11 highly polymorphic microsatellite markers that allowed us to estimate genetic diversity of locally born individuals. We found that individuals born in smaller and more isolated colonies were genetically less diverse. These colonies received a lower number of immigrants, supporting the idea that both reduced gene flow and small population size are responsible for the genetic pattern observed. Our results are particularly intriguing because the lesser kestrel is a vagile and migratory species with great movement capacity and dispersal potential. Overall, this study provides evidence of the association between individual heterozygosity and the size and spatial isolation of natal colonies in a highly mobile vertebrate showing relatively frequent dispersal and low genetic differentiation among local subpopulations.


Assuntos
Migração Animal , Falconiformes/crescimento & desenvolvimento , Falconiformes/genética , Animais , DNA/química , DNA/genética , Feminino , Variação Genética , Genótipo , Modelos Lineares , Masculino , Repetições de Microssatélites , Reação em Cadeia da Polimerase , Densidade Demográfica
11.
Mol Ecol ; 17(8): 2051-9, 2008 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-18346124

RESUMO

Dispersal is a life-history trait that plays a fundamental role in population dynamics, influencing evolution, species distribution, and the genetics and structure of populations. In spite of the fact that dispersal has been hypothesized to be an efficient behavioural mechanism to avoid inbreeding, the expected relationship between dispersal and mate relatedness still remains controversial. Here, we examine the genetic consequences of natal dispersal, namely the higher chance of obtaining genetically less similar mates as a result of moving from natal to breeding sites, in a lesser kestrel (Falco naumanni) population. Relatedness between individuals tended to decrease with distance between their breeding colonies, indicating that the study population follows an 'isolation-by-distance' pattern of spatial genetic structure. Such a fine-scale genetic structure generates a scenario in which individuals can potentially increase the chance of obtaining genetically less similar mates by dispersing over larger distances from their natal colony. Using dispersal information and genotypic data, we showed that mate relatedness decreased with natal dispersal distance, an effect that remained significant both while including and excluding philopatric individuals from the data set. These results, together with the well known detrimental consequences of reduced genetic diversity in the study population, suggest that dispersal may have evolved, at least in part, to avoid the negative fitness consequences of mating with genetically similar individuals.


Assuntos
Migração Animal/fisiologia , Falconiformes/genética , Animais , Análise por Conglomerados , DNA/química , DNA/genética , Feminino , Variação Genética , Genética Populacional , Genótipo , Endogamia , Masculino , Repetições de Microssatélites/genética , Modelos Genéticos , Reação em Cadeia da Polimerase , Espanha
12.
Mutat Res ; 648(1-2): 82-6, 2008 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-18973763

RESUMO

Although microsatellites are one of the most popular tools in genetic studies, their mutational dynamics and evolution remain unclear. Here, we apply extensive pedigree genotyping to identify and analyze the patterns and factors associated with de novo germline mutations across nine microsatellite loci in a wild population of lesser kestrels (Falco naumanni). A total of 10 germline mutations events were unambiguously identified in four loci, yielding an average mutation rate of 2.96x10(-3). Across loci, mutation rate was positively correlated with locus variability and average allele size. Mutations were primarily compatible with a stepwise mutation model, although not exclusively involved single-step changes. Unexpectedly, we found an excess of maternally transmitted mutations (male-to-female ratio of 0.1). One of the analyzed loci (Fn2.14) resulted hypermutable (mutation rate=0.87%). This locus showed a size-dependent mutation bias, with longer alleles displaying deletions or additions of a small number of repeat than shorter alleles. Mutation probability at Fn2.14 was higher for females and increased with parental (maternal) age but was not associated with individual physical condition, multilocus heterozygosity, allele length or allele span. Overall, our results do not support the male-biased mutation rate described in other organisms and suggest that mutation dynamics at microsatellite loci are a complex process which requires further research.


Assuntos
Falconiformes/anatomia & histologia , Falconiformes/genética , Mutação em Linhagem Germinativa , Repetições de Microssatélites/genética , Locos de Características Quantitativas , Animais , Animais Selvagens , Comportamento Animal/fisiologia , Feminino , Frequência do Gene , Mutação em Linhagem Germinativa/fisiologia , Masculino , Modelos Estatísticos , Comportamento de Nidação/fisiologia , Polimorfismo Genético/fisiologia , Reprodução/genética
13.
Sci Rep ; 8(1): 13436, 2018 09 07.
Artigo em Inglês | MEDLINE | ID: mdl-30194365

RESUMO

Inferring the demographic history of species is fundamental for understanding their responses to past climate/landscape alterations and improving our predictions about the future impacts of the different components of ongoing global change. Estimating the time-frame at which population fragmentation took place is also critical to determine whether such process was shaped by ancient events (e.g. past climate/geological changes) or if, conversely, it was driven by recent human activities (e.g. habitat loss). We employed genomic data (ddRAD-Seq) to determine the factors shaping contemporary patterns of genetic variation in the Iberian cross-backed grasshopper Dociostaurus crassiusculus, an endangered species with limited dispersal capacity and narrow habitat requirements. Our analyses indicate the presence of two ancient lineages and three genetic clusters resulted from historical processes of population fragmentation (~18-126 ka) that predate the Anthropocene. Landscape genetic analyses indicate that the limits of major river basins are the main geographical feature explaining large-scale patterns of genomic differentiation, with no apparent effect of human-driven habitat fragmentation. Overall, our study highlights the importance of detailed phylogeographic, demographic and spatially-explicit landscape analyses to identify evolutionary significant units and determine the relative impact of historical vs. anthropogenic factors on processes of genetic fragmentation in taxa of great conservation concern.


Assuntos
Conservação dos Recursos Naturais , Variação Genética , Genoma , Gafanhotos/genética , Sequenciamento de Nucleotídeos em Larga Escala , Animais , Gafanhotos/classificação , Região do Mediterrâneo
14.
Ecol Evol ; 7(9): 3110-3122, 2017 05.
Artigo em Inglês | MEDLINE | ID: mdl-28480010

RESUMO

Understanding the processes underlying spatial patterns of genetic diversity and structure of natural populations is a central topic in evolutionary biogeography. In this study, we combine data on ancient and contemporary landscape composition to get a comprehensive view of the factors shaping genetic variation across the populations of the scrub-legume grasshopper (Chorthippus binotatus binotatus) from the biogeographically complex region of southeast Iberia. First, we examined geographical patterns of genetic structure and employed an approximate Bayesian computation (ABC) approach to compare different plausible scenarios of population divergence. Second, we used a landscape genetic framework to test for the effects of (1) Late Miocene paleogeography, (2) Pleistocene climate fluctuations, and (3) contemporary topographic complexity on the spatial patterns of population genetic differentiation. Genetic structure and ABC analyses supported the presence of three genetic clusters and a sequential west-to-east splitting model that predated the last glacial maximum (LGM, c. 21 Kya). Landscape genetic analyses revealed that population genetic differentiation was primarily shaped by contemporary topographic complexity, but was not explained by any paleogeographic scenario or resistance distances based on climate suitability in the present or during the LGM. Overall, this study emphasizes the need of integrating information on ancient and contemporary landscape composition to get a comprehensive view of their relative importance to explain spatial patterns of genetic variation in organisms inhabiting regions with complex biogeographical histories.

15.
Evol Appl ; 8(6): 621-32, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-26136826

RESUMO

Anthropogenic habitat fragmentation has altered the distribution and population sizes in many organisms worldwide. For this reason, understanding the demographic and genetic consequences of this process is necessary to predict the fate of populations and establish management practices aimed to ensure their viability. In this study, we analyse whether the spatial configuration of remnant semi-natural habitat patches within a chronically fragmented landscape has shaped the patterns of genetic diversity and structure in the habitat-specialist esparto grasshopper (Ramburiella hispanica). In particular, we predict that agricultural lands constitute barriers to gene flow and hypothesize that fragmentation has restricted interpopulation dispersal and reduced local levels of genetic diversity. Our results confirmed the expectation that isolation and habitat fragmentation have reduced the genetic diversity of local populations. Landscape genetic analyses based on circuit theory showed that agricultural land offers ∽1000 times more resistance to gene flow than semi-natural habitats, indicating that patterns of dispersal are constrained by the spatial configuration of remnant patches of suitable habitat. Overall, this study shows that semi-natural habitat patches act as corridors for interpopulation gene flow and should be preserved due to the disproportionately large ecological function that they provide considering their insignificant area within these human-modified landscapes.

16.
Evolution ; 57(2): 397-405, 2003 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-12683535

RESUMO

Bird tails are extraordinarily variable in length and functionality. In some species, males have evolved exaggeratedly long tails as a result of sexual selection. Changes in tail length should be associated with changes in feather structure. The study of the evolution of feather structure in bird tails could give insight to understand the causes and means of evolution in relation to processes of sexual selection. In theory, three possible means of tail length evolution in relation to structural components might be expected: (1) a positive relationship between the increase in length and size of structural components maintaining the mechanical properties of the feather; (2) no relationship; that is, enlarging feather length without changes in the structural components; and (3) a negative relationship; that is, enlarging feather length by reducing structural components. These hypotheses were tested using phylogenetic analyses to examine changes in both degree of exaggeration in tail length and structural characteristics of tail feathers (rachis width and density of barbs) in 36 species, including those dimorphic and nondimorphic in tail length. The degree of sexual dimorphism in tail length was negatively correlated with both rachis width and density of barbs in males but not in females. Reinforcing this result, we found that dimorphism in tail length was negatively associated with dimorphism in tail feather structure (rachis width and density of barbs). These results support the third hypothesis, in which the evolution of long feathers occurs at the expense of making them simpler and therefore less costly to produce. However, we do not know the effects of enfeeblement on the costs of bearing. If the total costs increased, the enfeeblement of feathers could be explained as a reinforcement of the honesty of the signal. Alternatively, if total costs were reduced, the strategy could be explained by cheating processes. The study of female preferences for fragile tail feathers is essential to test these two hypotheses. Preferences for fragile tails would support the evolution of reinforcement of honesty, whereas female indifference would indicate the existence of cheating in certain stages of the evolutionary process.


Assuntos
Aves/anatomia & histologia , Aves/genética , Animais , Evolução Biológica , Aves/fisiologia , Plumas/anatomia & histologia , Feminino , Masculino , Modelos Biológicos , Filogenia , Seleção Genética , Comportamento Sexual Animal
17.
Proc Biol Sci ; 271(1551): 1929-33, 2004 Sep 22.
Artigo em Inglês | MEDLINE | ID: mdl-15347516

RESUMO

Adjustment of offspring sex ratios should be favoured by natural selection when parents are capable of facultatively altering brood sex ratios and of recognizing the circumstances that predict the probable fitness benefit of producing sons and daughters. Although experimental studies have shown that female birds may adjust offspring sex ratios in response to changes in their own condition and in the external appearance of their mate, and male attributes other than his external morphology are also thought to act as signals of male quality, it is not known whether females will respond to changes in such signals, in the absence of any change in the appearance of the male himself. Here, we experimentally manipulated a male courtship display, the green plants carried to the nest by male spotless starlings (Sturnus unicolor), without changing any physical attributes of the male himself, and examined whether this influenced female decisions on offspring sex ratio. We found that in an environment in which female starlings were producing more daughters than sons, experimental enhancement of the green nesting material caused females to significantly increase the number of male eggs produced and thereby removed the female bias. This effect was consistent in 2 years and at two localities. This demonstrates that the green material, whose function has long puzzled biologists, conveys important information to the female and that she facultatively adjusts offspring production accordingly.


Assuntos
Comportamento de Nidação/fisiologia , Seleção Genética , Razão de Masculinidade , Comportamento Sexual Animal/fisiologia , Aves Canoras/fisiologia , Animais , Feminino , Masculino , Plantas , Espanha
18.
Parasitol Res ; 104(2): 467-70, 2009 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-18818949

RESUMO

We genetically analysed haematozoa parasites (Protozoa) isolated from nestling eagle owls (Bubo bubo) in Toledo province, Central Spain. A total of 206 nestlings from 74 nests were screened for parasites of the genera Leucocytozoon, Plasmodium, and Haemoproteus using a very efficient polymerase chain reaction (PCR) approach that amplifies a partial segment of the mitochondrial cytochrome b gene of these parasites. PCR-based detection and sequence analyses revealed a unique lineage of Leucocytozoon (EO1) parasitizing nestling eagle owls. Ocular examination of blood smears identified these parasites as Leucocytozoon ziemanni, the only species deemed valid in owls based on morphology. Preliminary phylogenetic analyses using homologous published sequences isolated from other owl species suggest that L. ziemanni constitutes a monophyletic clade that may be composed by a complex of genetically differentiated cryptic species.


Assuntos
Sangue/parasitologia , Haemosporida/classificação , Haemosporida/isolamento & purificação , Doenças Parasitárias em Animais/parasitologia , Estrigiformes/parasitologia , Animais , Análise por Conglomerados , Citocromos b/genética , DNA de Protozoário/química , DNA de Protozoário/genética , Haemosporida/genética , Dados de Sequência Molecular , Filogenia , Reação em Cadeia da Polimerase/métodos , Análise de Sequência de DNA , Espanha
19.
Mol Ecol ; 16(17): 3712-20, 2007 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-17845443

RESUMO

Parasites and infectious diseases are major determinants of population dynamics and adaptive processes, imposing fitness costs to their hosts and promoting genetic variation in natural populations. In the present study, we evaluate the role of individual genetic diversity on risk of parasitism by feather lice Degeeriella rufa in a wild lesser kestrel population (Falco naumanni). Genetic diversity at 11 microsatellite loci was associated with risk of parasitism by feather lice, with more heterozygous individuals being less likely to be parasitized, and this effect was statistically independent of other nongenetic parameters (colony size, sex, location, and year) which were also associated with lice prevalence. This relationship was nonlinear, with low and consistent prevalences among individuals showing high levels of genetic diversity that increased markedly at low levels of individual heterozygosity. This result appeared to reflect a genome-wide effect, with no single locus contributing disproportionably to the observed effect. Thus, overall genetic variation, rather than linkage of markers to genes experiencing single-locus heterosis, seems to be the underlying mechanism determining the association between risk of parasitism and individual genetic diversity in the study host-parasite system. However, feather lice burden was not affected by individual heterozygosity; what suggest that differences in susceptibility, rather than variation in defences once the parasite has been established, may shape the observed pattern. Overall, our results highlight the role of individual genetic diversity on risk of parasitism in wild populations, what has both important evolutionary implications and major consequences for conservation research on the light of emerging infectious diseases that may endanger genetically depauperated populations.


Assuntos
Falconiformes/parasitologia , Ftirápteros/fisiologia , Polimorfismo Genético , Animais , Falconiformes/genética , Predisposição Genética para Doença , Repetições de Microssatélites , Fatores de Risco
20.
Mol Ecol ; 16(22): 4858-66, 2007 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-17944853

RESUMO

Insight into the genetic basis of malaria resistance is crucial for understanding the consequences of this parasite group on animal populations. Here, we analyse the relationship between genotypic variation at 11 highly variable microsatellite loci and prevalence of three different lineages of avian malaria, two Plasmodium (RTSR1, LK6) and one Haemoproteus (LK2), in a wild population of the endangered lesser kestrel (Falco naumanni). Although we used a large sample size (584 typed individuals), we did not find any significant association between the prevalence of the studied parasite lineages and individual genetic diversity. Although our data set is large, the 11 neutral markers typed may have had low power to detect such association, in part because of the low parasite prevalence observed (less than 5% of infected birds). However, the fact that we have detected previous correlations between genetic diversity and other traits (ectoparasitism risk, fecundity) in the study population using the same panel of neutral markers and lower sample sizes suggests that other factors could underlie the absence of such a similar correlation with avian malaria. Differences in the genetics of the studied traits and in their particular basis of inbreeding depression (dominance vs. overdominance) may have led to malaria prevalence, but not other traits, being uncoupled with individual genetic diversity. Also, we cannot discard the possibility that the absence of association was a consequence of a low pathogenic effect of these particular malaria lineages on our lesser kestrel population, and thus we should not expect the evolution of genetic resistance against these parasites.


Assuntos
Falconiformes/genética , Imunidade Inata/genética , Malária Aviária/genética , Polimorfismo Genético , Alelos , Animais , Falconiformes/parasitologia , Marcadores Genéticos , Genótipo , Malária Aviária/epidemiologia , Malária Aviária/imunologia , Repetições de Microssatélites , Reação em Cadeia da Polimerase , Prevalência
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