Systematic Biology最新文献

Unrooted phylogenetic networks are commonly used to represent evolutionary data in the presence of incompatibilities. While rooted phylogenetic networks offer a more explicit framework for depicting evolutionary histories involving reticulate events, they are reported less frequently, probably due to a lack of tools that are as easily applicable as those for unrooted networks. Here, we introduce PhyloFusion, a fast and user-friendly method for constructing rooted phylogenetic networks from sets of rooted phylogenetic trees. The resulting networks have the tree-child property. The algorithm accommodates trees with unresolved nodes -often resulting from the contraction of low-support edges- as well as some degree of missing taxa. We demonstrate its application to the analysis of functionally related gene groups and show that it can efficiently handle datasets comprising tens of trees or hundreds of taxa. An open source implementation of PhyloFusion is available as part of the SplitsTree app: https://www.github.com/husonlab/splitstree6 All data available here: https://doi.org/10.5061/dryad.k3j9kd5h5.

Bayesian inference has predominantly relied on the Markov chain Monte Carlo (MCMC) algorithm for many years. However, MCMC is computationally laborious, especially for complex phylogenetic models of time trees. This bottleneck has led to the search for alternatives, such as variational Bayes, which can scale better to large datasets. In this paper, we introduce torchtree, a framework written in Python that allows developers to easily implement rich phylogenetic models and algorithms using a fixed tree topology. One can either use automatic differentiation, or leverage torchtree's plug-in system to compute gradients analytically for model components for which automatic differentiation is slow. We demonstrate that the torchtree variational inference framework performs similarly to BEAST in terms of speed, and delivers promising approximation results, though accuracy varies across scenarios. Furthermore, we explore the use of the forward KL divergence as an optimizing criterion for variational inference, which can handle discontinuous and non-differentiable models. Our experiments show that inference using the forward KL divergence is frequently faster per iteration compared to the evidence lower bound (ELBO) criterion, although the ELBO-based inference may converge faster in some cases. Overall, torchtree provides a flexible and efficient framework for phylogenetic model development and inference using PyTorch. phylogenetics, Bayesian inference, variational Bayes, PyTorch.

Missing data is a long standing issue in phylogenetic inference, which often results in high levels of taxonomic instability, obscuring otherwise well supported relationships. Multiple approaches have been developed to deal with the negative effects of ineffective overlap on tree resolution, often by identifying taxa for removal. Here we repurpose a heuristic method developed to identify unstable taxa in morphological data matrices, concatabominations, and combine it with a novel gene-tree jackknifing on matrix representation of trees to identify candidates for targeted sequencing. Using a multilocus caecilian dataset we illustrate the method's capacity to identify candidate taxa and loci for additional sequencing, compare the results to those of the mathematics-based gene sampling sufficiency approach and explore the terrace space associated with the multilocus dataset. We show that our approach yields tractable numbers of loci/taxa for targeted sequencing that successfully mitigate topological instability due to ineffective overlap, even when modest amounts of data are added.

The recent rapid radiation of Tillandsia subgenus Tillandsia (Bromeliaceae) provides an attractive system to study the drivers and constraints of species diversification. This species-rich Neotropical monocot clade includes predominantly epiphytic species displaying vast phenotypic diversity. Recent in-depth phylogenomic work revealed that the subgenus originated within the last 7 MY, with one major expansion from South into Central America within the last 5 MY. However, disagreements between phylogenies and lack of resolution at shallow nodes suggest that hybridization may have occurred throughout the radiation, together with frequent incomplete lineage sorting and rapid gene family evolution. We used whole-genome resequencing data to explore the evolutionary history of representative ingroup species employing both tree-based and network approaches. Our results indicate that lineage co-occurrence does not predict relatedness and confirm significant deviations from a tree-like structure, coupled with pervasive gene tree discordance. Focusing on hybridization, ABBA-BABA and related statistics were used to infer the rates and relative timing of introgression, while topology weighting uncovered high heterogeneity of the phylogenetic signal along the genome. High rates of hybridization within and among subclades suggest that, contrary to previous hypotheses, the expansion of subgenus Tillandsia into Central America proceeded through several dispersal events, punctuated by episodes of diversification and gene flow. Network analysis revealed reticulation as a plausible propeller during radiation and establishment across different ecological niches. This work contributes a plant example of prevalent hybridization during rapid species diversification, supporting the hypothesis that interspecific gene flow facilitates explosive diversification.

The total number of species on earth and the rate at which new species are created are fundamental questions for ecology, evolution and conservation. These questions have typically been approached separately, despite their obvious interconnection. In this study, we approach both questions in conjunction, for all terrestrial animals. To do this, we combine two previously unconnected bodies of theory: general ecosystem models and individual-based ecological neutral theory. General ecosystem models provide us with estimated numbers of individual organisms, separated by functional group and body size. Neutral theory, applied within a guild of functionally similar individuals, connects species richness, speciation rate, and number of individual organisms. In combination, for terrestrial endotherms where species numbers are known, they provide us with estimates for speciation rates as a function of body size and diet class. Extrapolating the same rates to guilds of ectotherms enables us to estimate the species richness of those groups, including species yet to be described. We find that speciation rates per species per million years decrease with increasing body size. Rates are also higher for carnivores compared to omnivores or herbivores of the same body size. Our estimate for the total number of terrestrial species of animals is in the range 1.03-2.92 million species, a value consistent with estimates from previous studies, despite having used a fundamentally new approach. Perhaps what is most remarkable about these results is that they have been obtained using only limited data from larger endotherms and their speciation rates, with the predictive process being based on mechanistic theory. This work illustrates the potential of a new approach to classic eco-evolutionary questions, while also adding weight to existing predictions. As we now face an era of dramatic biological change, new methods will be needed to mechanistically model global biodiversity at the species and individual organism level. This will be a huge challenge but the combination of general ecosystem models and neutral theory that we introduce here is a way to tractably achieve it.

-The interplay of key innovation and ecological opportunity is commonly recognized to be the catalyst for rapid radiation. Underground storage organs (USOs), as a vital ecological trait, are advantageous for the adaptation of plants to extreme environments, but receive less attention compared to aboveground organs. Repeated evolution of various USOs has occurred across the plant tree of life. However, whether repeated occurrences of a USO in different clades of a group can promote its replicated radiations in combination with the invasion of similar environments remains poorly known. Corydalis is a megadiverse genus in Papaveraceae and exhibits remarkable variations in USO morphology and biome occupancy. Here, we first generated a robust phylogeny for Corydalis with wide taxonomic and genomic coverage based on plastome and nuclear ribosomal DNA sequence data. By dating the branching events, reconstructing ancestral ranges, evaluating diversification dynamics, and inferring evolutionary patterns of USOs and biomes and their correlations, we then tested whether the interplay of USO evolution and biome shifts has driven rapid diversification of some Corydalis lineages. Our results indicate that Corydalis began to diversify in the Qinghai-Tibet Plateau (QTP) at ca. 41 Ma, and 88% of dispersals happened through forests, suggesting that forests served as important dispersal corridors for range expansion of the genus. The storage root has originated independently at least 6 times in Corydalis since the Miocene, and its acquisition could have operated as a key innovation toward the adaptation to the alpine biome in the QTP. Repeated evolution of this game-changing trait and invasions of alpine biome, in combination with geoclimatic changes, could have jointly driven independent radiations of the 2 clades of Corydalis in the QTP at ca. 6 Ma. Our study provides new insights into the joint contribution of USO repeated evolution and biome shifts to replicated radiations, hence increasing our ability to predict evolutionary trajectories in plants facing similar environmental pressures.