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Marcio R Pie

Publications and source records attributed to Marcio R Pie.

10 recordsLinked to original sources
PubMed2025

Ancient Introgression Explains Mitochondrial Genome Capture and Mitonuclear Discordance Among South American Collared Tropidurus Lizards.

Mitonuclear discordance-evolutionary discrepancies between mitochondrial and nuclear DNA phylogenies-can arise from various factors, including introgression, incomplete lineage sorting, recent or ancient demographic fluctuations, sex-biased dispersal asymmetries, among others. Understanding this phenomenon is crucial for accurately reconstructing evolutionary histories, as failing to account for discordance can lead to misinterpretations of species boundaries, phylogenetic relationships, and historical biogeographic patterns. We investigate the evolutionary drivers of mitonuclear discordance in the Tropidurus spinulosus species group, which contains nine species of lizards inhabiting open tropical and subtropical environments in South America. Using a combination of population genetic and phylogenomic approaches applied to mitochondrial and nuclear data, we identified different instances of gene flow that occurred in ancestral lineages of extant species. Our results point to a complex evolutionary history marked by prolonged isolation between species, demographic fluctuations, and potential episodes of secondary contact with genetic admixture. These conditions likely facilitated mitochondrial genome capture while diluting signals of nuclear introgression. Furthermore, we found no strong evidence supporting incomplete lineage sorting or natural selection as primary drivers of the observed mitonuclear discordance. Therefore, the unveiled patterns are most consistent with neutral demographic processes, coupled with ancient mitochondrial introgression, as the main factors underlying the mismatch between nuclear and mitochondrial phylogenies in this system. Future research could further explore the role of other demographic processes, such as asymmetric sex-biased dispersal, in shaping these complex evolutionary patterns.

Animals↗
PubMed2006

Evolution of genome size in fishes: a phylogenetic test of the Hinegardner and Rosen hypothesis.

Despite remarkable advances in genomic studies over the past few decades, surprisingly little is known about the processes governing genome evolution at macroevolutionary timescales. In a seminal paper, Hinegardner and Rosen (Am Nat 106:621-644, 1972) suggested that taxa characterized by larger genomes should also display disproportionately stronger fluctuations in genome size. Therefore, according to the Hinegardner and Rosen (HR) hypothesis, there should be a negative correlation between average within-family genome size and its corresponding coefficient of variation (CV), a prediction that was supported by their analysis of the genomes of 275 species of fish. In this study we reevaluate the HR hypothesis using an expanded dataset (2050 genome size records). Moreover, in addition to the use of standard linear regression techniques, we also conducted modern comparative analyses that take into account phylogenetic non-independence. Our analyses failed to confirm the negative relationship detected in the original study, suggesting that the evolution of genome size in fishes might be more complex than envisioned by the HR hypothesis. Interestingly, the frequency distribution of fish genome sizes was strongly skewed, even on a logarithmic scale, suggesting that the dynamics underlying genome size evolution are driven by multiplicative phenomena, which might include chromosomal rearrangements and the expansion of transposable elements.

Animals↗
PubMed2006

The influence of phylogenetic uncertainty on the detection of positive Darwinian selection.

The power of maximum likelihood tests of positive selection on protein-coding genes depends heavily on detecting and accounting for potential biases in the studied data set. Although the influence of transition:transversion and codon biases have been investigated in detail, little is known about how inaccuracy in the phylogeny used during the calculations affects the performance of these tests. In this study, 3 empirical data sets are analyzed using sets of simulated topologies corresponding to low, intermediate, and high levels of phylogenetic uncertainty. The detection of positive selection was largely unaffected by errors in the underlying phylogeny. However, the number of sites identified as being under positive selection tended to be overestimated.

Animals↗
PubMed2006

Density-dependent topographical specialization in Gyrodactylus anisopharynx (Monogenoidea, Gyrodactylidae): boosting transmission or evading competition?

Viviparous gyrodactylids are remarkable monogenoid ectoparasites, not only because of their speciousness, but also due to their unusually wide range of hosts. Although many factors have been proposed to determine the location where gyrodactylids attach to their hosts, little is known about how their preference for specific host body regions changes over the course of infection. In this study, we investigate the dynamics of topographical specialization of the parasite Gyrodactylus anisopharynx on 2 of its natural freshwater fish hosts (Corydoras paleatus and C. ehrhardti), as well as a naïve host (C. schwartzi). We recorded the spatial location of this parasite from the foundation of the infrapopulation to its extinction to assess how topographical specialization is affected by host species, the size and the age of the infrapopulation, and the possibility of transmission among hosts. Our results indicate that topographical specialization is negatively correlated with infrapopulation size and only marginally affected by infrapopulation age. Also, the degree of specialization was different among host species, but seemed unaffected by the possibility of transmission among hosts. Therefore, observed changes in spatial specialization of G. anisopharynx do not appear to represent adaptive responses to maximize their transmission. Rather, mechanisms such as increased competition and/ or local immune responses might cause parasites to occupy less favorable regions of the body of their hosts with increasing density.

Animals↗
PubMed2005

A null model of morphospace occupation.

Progress in understanding the relationship between lineage diversity, morphological diversity, and morphospace dynamics has been hampered by the lack of an appropriate null model of morphospace occupation. In this article, we introduce a simple class of models based on branching random walks (BRWs) for continuous traits. We show that many of the observed patterns of morphospace occupation might be simply a consequence of the dynamics of BRWs and therefore might not require special explanations. We also provide expected patterns of morphospace occupation according to a number of different conditions. In particular, we model BRWs on neutral landscapes and demonstrate that clumping in morphospace is possible even in the absence of adaptive landscapes with well-defined peaks and valleys. The quantitative definition of the BRW provides a means to analyze, both computationally and analytically, patterns of morphospace occupation according to different hypotheses.

Ecosystem↗
PubMed2005

Signal evolution in prey recognition systems.

In this paper a graphical model first developed in the context of kin recognition is adapted to the study of signalling in predator-prey systems. Antipredation strategies are envisioned as points along a signal-to-noise (S/N) axis, with concealing (low S/N) and conspicuous (high S/N) strategies being placed at opposite sides of this axis. Optimal prey recognition systems should find a trade-off between acceptance errors (going after a background cue as if it were a prey) and rejection errors (not going after a prey as if it were background noise). The model also predicts the types of cues the predator should use in opposite sides of the S/N axis.

Animals↗
PubMed2005

Lethargic crab disease: multidisciplinary evidence supports a mycotic etiology.

Although lethargic crab disease (LCD) is causing massive mortalities in populations of the mangrove crab Ucides cordatus of Northeastern Brazil, the identity of its etiological agent was hitherto unknown. In this study we provide robust evidence suggesting that LCD is caused by an anamorph Ascomycota (Fungi). We examined specimens of U. cordatus collected from stocks affected by LCD. Histological and TEM methods detected the presence of hyphae, conidia, and condiophores in several host tissues. Moreover, the abundance of fungal stages is negatively associated with crab health. Finally, DNA was isolated from the fungus and a region of its 18S ribosomal gene was sequenced Phylogenetic analyses not only confirm the diagnosis of the LCD fungus in crab tissues as an ascomycete, but also suggest a close relationship with members of the subphylum Pezizomycotina.

Animals↗
PubMed2005

Mode of transmission, host switching, and escape from the Red Queen by viviparous gyrodactylids (Monogenoidea).

Compared to other monogenoidean groups, viviparous gyrodactylids exhibit extraordinary species diversity and broad host range. It has been suggested that this evolutionary success is associated with a suite of morphological and life-history traits that include, in part, continuous transmission (i.e., ability to infect new hosts throughout the gyrodactylid life cycle). Experiments were conducted to explore the putative adaptive advantage of continuous transmission within viviparous gyrodactylids during colonization of new host resources. Differences in infrapopulation growth, such as abundance, prevalence, and duration of the infection, of Gyrodactylus anisopharynx on 3 species of fish--Corydoras paleatus and Corydoras ehrhardti (both natural hosts) as well as Corydoras schwartzi (a host not known to harbor G. anisopharynx)--held under isolated and grouped conditions were determined. Results showed that infrapopulations of G. anisopharynx on C. paleatus and C. schwartzi had higher growth when the parasite had the opportunity for host transfer (grouped hosts). Infrapopulations of G. anisopharynx on isolated and grouped C. ehrhardti showed an opposite trend, although differences in mean duration and maximum abundance were not statistically different. Results obtained from experiments with C. paleatus and C. schwartzi support the hypothesis that continuous transmission in viviparous gyrodactylids enhances colonization success, probably by allowing initial avoidance of Red Queen dynamics. The absence of statistical differences between infrapopulations on isolated and grouped C. ehrhardti suggests that parasite dynamics may be influenced by factors other than continuous transmission in this host.

Animals↗
PubMed2004

Nest architecture, activity pattern, worker density and the dynamics of disease transmission in social insects.

The role of disease in the organization of insect colonies has become an important focus of research in evolutionary pathobiology, in which the relationship of sociality and disease transmission can be comparatively and experimentally analysed. In this paper we use an individual-based model of disease transmission to assess how an epidemic is influenced by worker density and activity level, the probability of disease transmission, and the structural organization of the nest. First, we observed in our model a nonlinear interaction between worker density and the probability of disease transmission: high levels of both factors interact to enhance the likelihood of an epidemic. Additionally, when we incorporated in our model the empirical observation that only a fraction of the worker population in social insect colonies is active at any given point in time, results suggested that relatively low levels of worker movement can have a significant impact on the spread of disease, slowing its transmission through the colony. Finally, we found that nests having even a simple spatial separation of chambers could delay the spread of infection and diminish the severity of an outbreak. The effect of nest structure in delaying infection spread became more pronounced as nest architecture became increasingly unidimensional, as in the case of simple gallery nests. Therefore, nest architecture and worker activity patterns might indeed exert considerable influence on the dynamics of epidemics in social insects and should be incorporated into models of disease transmission.

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