Ciências Biológicas: Biologia Animal

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Navegando Ciências Biológicas: Biologia Animal por Assunto "Akodon montensis"

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    Comparação morfométrica entre crânios de híbridos e seus parentais Akodon cursor e Akodon montensis (Rodentia: Sigmodontinae)
    (Universidade Federal do Espírito Santo, 2024-10-31) Teixeira, Júlia Andrade Frederico; Paresque, Roberta; https://orcid.org/0000-0001-8177-4144; http://lattes.cnpq.br/5411026526760218; https://orcid.org/0009-0008-1528-580X; http://lattes.cnpq.br/0755088166225492; Assis, Ana Paula Aprígio; https://orcid.org/0000-0001-8170-6352; http://lattes.cnpq.br/1901397112835628; Rodrigues, Ana Carolina Loss ; https://orcid.org/0000-0002-8298-8555; http://lattes.cnpq.br/8415444657040950
    This study investigates the cranial morphological differences between two species of rodents, Akodon cursor (Sigmodontinae: Rodentia) and Akodon montensis (Sigmodontinae: Rodentia), and their hybrids, highlighting the implications of hybridization for morphological inheritance. We analyzed a total of 122 specimens, including adults from both species and hybrids. Markings were made on the skulls of the specimens to obtain intersection points. From these points, we obtained the coordinates of the geometric landmarks, resulting in 38 distances. To examine and compare these distances, statistical methods such as ANOVA, Principal Component Analysis (PCA), Canonical Discriminant Analysis (CDA), Comparative Analysis of Complexity and Modularity Parameters, and Generalized Procrustes Analyses (GPA) were applied. The results indicated that the sampling effort was adequate to capture most of the variation in cranial measurements, as evidenced by the rarefaction curves, which showed stabilization of metrics after approximately 30 specimens for each group. Significant differences among the three groups were found in 23 of the 38 cranial distances (p ≤ 0.05), highlighting relevant morphological variations that likely reflect specific adaptations. Notably, A. cursor exhibited distinct phenotypic characteristics compared to the other groups, suggesting stronger selective pressures in its habitat. The findings reinforce previous studies indicating that hybridization contributes to an increase in morphological diversity, allowing for greater adaptability in varied ecological niches. The PCA revealed considerable morphological overlap between A. cursor, A. montensis, and the hybrids, suggesting phenotypic similarity among the groups. The CDA showed significant separation between the groups, with the intermediate position of the hybrids reflecting the phenotypic inheritance from both parents. The first discriminant function accounted for most of the observed variation. Additionally, the Comparative Analysis of Complexity Parameters, combined with the GPA, confirmed these results. These analyses indicated that hybrids not only retain characteristics from both parents but also position themselves morphologically between the two groups. The cranial morphological analysis revealed significant differences between A. cursor, A. montensis, and hybrids, suggesting distinct ecological adaptations and diverse evolutionary processes. Hybridization emerges as an important evolutionary process that generates morphological diversity and maintains genetic variation in contact zones. The observed differences among the three groups likely reflect different ecological strategies, with A. cursor and A. montensis resulting from distinct evolutionary trajectories, while hybrids explore a combination of resources from both parents. This study highlights the interaction between morphology, ecology, and evolution in Akodon species, underscoring the importance of hybridization in generating phenotypic and adaptive diversity
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    Especiação em Akodon cursor (Winge, 1887): uma abordagem multidisciplinar
    (Universidade Federal do Espírito Santo, 2016-02-29) Massariol, Cristina Dornelas de Andrade Nogueira; Paresque, Roberta; Fagundes, Valéria; Rodrigues, Ana Carolina Loss; Azevedo, Celso Oliveira; Geise, Lena; Yonenaga-Yassuda, Yatiyo
    Akodon cursor (Winge, 1887) is a Sigmodontinae rodent that lives in the Atlantic Forest of Brazil and presents high chromosomal polymorphism (2n=14-16 and NF=18-26), with 31 distinct karyotypes described for this species up to now.Gene sequences of 402 individuals and 63 localities reiterate the geographic structure of A. cursorin North and South clades, with genetic divergence of 4.4% for COI and 2.5% for Cit-b.The phylogeographic break is localized between latitudes 16-18ºS(north Minas Gerais and southern Bahia), coinciding with the Jequitinhonha Valley. The structure of the clades is not related to exclusive karyotypes. However, the form 2n=16 ismore frequent in the North and the form 2n=14 inthe South.Demographic data indicate karyotype contribution on geographic diversification, with populational equilibrium in the North and two distinct and stable populations in the South.Experimental crosses (n=185) involving specimes of A. cursorwith intermediate conditions of geographical distribution (interclades) and karyotype (2n=15),donot indicate reproductive isolation between the Northern clades and Southern clades (reproductive success above 80% ), but show reduced fertility in individuals 2n=15.Combinations (female x male)2n=14x2n=15 and 2n=15x2n=16 show, respectively, higher and lower reproductive success, thusreflecting higher affinity between the forms 2n=15 and 2n=14, and revealing that females 2n=15 presentreproductive disadvantageswhen compared to males in the same heterozygous condition.Moreover, inspecimens with the same diploid number,individuals captured from nature present higher reproductive success than those born in captivity. Aggressive behavior among couples were registered, being more frequent in the Southern clade.There are morphological/anatomical distinctionsbetween individuals of the Northern and Southern clades, in agreementwith the geographical pattern obtained in molecular analysis.Thus, although the use of morphological criteria and reciprocal monophyly points to distinctionsbetweenNorthern and Southern clades showing no signals of reproductive isolation between these populationsis noticeable.The fertility reduction of individuals 2n=15 indicates an incipient process of stasipatric speciation, tending to establish the form 2n=16 in the North andthe form 2n=14 inthe South.Interspecific crosses (n=80) between A. cursorand A. montensis(2n=23-25) Thomas 1913produces sterile hybrids (2n=19-20), unlike observed among supposed A. cursor"hybrid", 2n=15 and interclade.In these cases, the introgression is bidirectional, although ahigher reproductive success (75%) occurred between female of A. montensis2n=24 and male of A. cursor2n=16 (North clade). A. montensiswith 2n=23 14(female), 2n=25 (femaleand male), and A. cursorwith 2n=15 (female) don't generate hybrids.Considering that 2n=14 is aderived condition in A.cursor,and themost frequent in populations of the South clade (which occurs with sympatry with A. montensis), thereexistsa barrier to a more effective gene flow in these areas, with karyotype showing an important role in maintaining the identity of each species