Biology subjects

Klopfstein, S.

Publications and source records attributed to Klopfstein, S..

8 recordsLinked to original sources

bioRxiv2023

A macroevolutionary role for chromosomal fusion and fission in Erebia butterflies

The impact of large-scale chromosomal rearrangements, such as fusions and fissions, on speciation is a long-standing conundrum. We assessed whether bursts of change in chromosome numbers resulting from chromosomal fusion and fission are related to increased speciation rates in Erebia, one of the most species-rich and karyotypically variable butterfly groups. We established a genome-based phylogeny and employed state-dependent birth-death models to infer trajectories of karyotype evolution across this genus. We demonstrated that rates of anagenetic chromosomal changes (i.e. along phylogenetic branches) exceed cladogenetic changes (i. e. at speciation events), but when cladogenetic changes occur, they are mostly associated with chromosomal fissions rather than fusions. Moreover, we found that the relative importance of fusion and fission differs among Erebia clades of different ages, where especially in younger, more karyotypically diverse clades, speciation is more frequently associated with chromosomal changes. Overall, our results imply that chromosomal fusions and fissions have contrasting macroevolutionary roles and that large-scale chromosomal rearrangements are associated with bursts of species diversification.

evolutionary biology↗

bioRxiv2021

New fossil wasp species from the earliest Eocene Fur Formation has its closest relatives in late Eocene ambers (Hymenoptera, Ichneumonidae, Pherhombinae)

Darwin wasps (Ichneumonidae) are one of the most species-rich insect families, but also one of the most understudied ones, both in terms of their extant and extinct diversity. We here use morphometrics of wing veins and an integrative Bayesian analysis to place a new rock fossil species from the Danish Fur Formation ([~]54 Ma) in the tree of Darwin wasps. The new species, Pherhombus parvulus n. sp., is placed firmly in Pherhombinae, an extinct subfamily so far only known from Baltic and Rovno-Ukranian ambers, which are estimated to be 34-48 Ma and 34-38 Ma, respectively. Our phylogenetic analysis recovers a subfamily clade within the higher Ophioniformes formed by Pherhombinae, Townesitinae and Hybrizontinae, in accordance with previous suggestions. Due to the placement of the new species as sister to the remaining members of Pherhombinae, we argue that our finding is not at odds with a much younger, late Eocene age ([~]34-41 Ma) of Baltic amber and instead demonstrates that Pherhombus existed over a much longer period than previously thought. Our results also exemplify the power of wing vein morphometrics and integrative phylogenetic analyses in resolving the placement even of poorly preserved fossil specimens.

paleontology↗

bioRxiv2021

High diversity of pimpline parasitoid wasps (Hymenoptera, Ichneumonidae, Pimplinae) from the lowermost Eocene Fur Formation

With an estimated 100,000 extant species, Darwin wasps (Ichneumonidae) are more specious than all vertebrates together. However, only 288 fossil species have been described to date, with hundreds more awaiting formal description in palaeontological collections. One of the largest gaps in our knowledge concerns the ~12 million years between the K-PG mass extinction and the late Ypresian, from which only two species have been formally described, including Pimpla stigmatica Henriksen from the Danish Fur Formation (~55 Ma). Ie here redescribe and reclassify this species in the genus Epitheronia Gupta, n. comb., and describe nine new species from this fossil locality that are consistent with a placement in Pimplinae: Crusopimpla collina n. sp., C. elongata n. sp., C. minuta n. sp., C. rettigi n. sp., C. violina n. sp., Theronia? furensis n. sp., T. nigriscutum n. sp., Xanthopimpla ciboisae n. sp., and X. crescendae n. sp. The diagnosis of the genus Crusopimpla Kopylov, Spasojevic & Klopfstein is amend in the light of the new species. By comparing the preserved colouration between and within specimens of different species, we draw conclusions about the taxonomic usefulness of colour patterns observed in Fur Formation ichneumonids. The number of described species of pimpline parasitoid wasps from Fur is very high when compared to any other fossil deposit, but low with respect to numbers of extant species. Further study and excavation of Fur ichneumonids will certainly reveal an even higher diversity.

paleontology↗

bioRxiv2019

Mind the Outgroup: Influence of Taxon Sampling on Total-Evidence Dating of Pimpliform Parasitoid Wasps (Hymenoptera, Ichneumonidae)

Taxon sampling is a central aspect of phylogenetic study design, but it has received limited attention in the context of molecular dating and especially in the framework of total-evidence dating, a widely used dating approach that directly integrates molecular and morphological information from extant and fossil taxa. We here assess the impact of different outgroup sampling schemes on age estimates in a total-evidence dating analysis under the uniform tree prior. Our study group are Pimpliformes, a highly diverse, rapidly radiating group of parasitoid wasps of the family Ichneumonidae. We cover 201 extant and 79 fossil taxa, including the oldest fossils of the family from the Early Cretaceous and the first unequivocal representatives of extant subfamilies from the mid Paleogene. Based on newly compiled molecular data from ten nuclear genes and a morphological matrix that includes 222 characters, we show that age estimates become both older and less precise with the inclusion of more distant and more poorly sampled outgroups. In addition, we discover an artefact that might be detrimental for total-evidence dating: "bare-branch attraction", namely high attachment probabilities of, especially, older fossils to terminal branches for which morphological data are missing. After restricting outgroup sampling and adding morphological data for the previously attracting, bare branches, we recover a Middle and Early Jurassic origin for Pimpliformes and Ichneumonidae, respectively. This first age estimate for the group not only suggests an older origin than previously thought, but also that diversification of the crown group happened before the Cretaceous-Paleogene boundary. Our case study demonstrates that in order to obtain robust age estimates, total-evidence dating studies need to be based on a thorough and balanced sampling of both extant and fossil taxa, with the aim of minimizing evolutionary rate heterogeneity and missing morphological information.

zoology↗

bioRxiv2019

Completing Linnaeus’s Inventory of the Swedish Insect Fauna: Only 5000 Species Left

Despite more than 250 years of taxonomic research, we still have only a vague idea about the true size and composition of the faunas and floras of the planet. Many biodiversity inventories provide limited insight because they focus on a small taxonomic subsample or a tiny geographic area. Here, we report on the size and composition of the Swedish insect fauna, thought to represent roughly half of the diversity of multicellular life in one of the largest European countries. Our results are based on more than a decade of data from the Swedish Taxonomy Initiative and its massive inventory of the countrys insect fauna, the Swedish Malaise Trap Project The fauna is considered one of the best known in the world, but the initiative has nevertheless revealed a surprising amount of hidden diversity: more than 3,000 new species (301 new to science) have been documented so far. Here, we use three independent methods to analyze the true size and composition of the fauna at the family or subfamily level: (1) assessments by experts who have been working on the most poorly known groups in the fauna; (2) estimates based on the proportion of new species discovered in the Malaise trap inventory; and (3) extrapolations based on species abundance and incidence data from the inventory. For the last method, we develop a new estimator, the combined non-parametric estimator, which we show is less sensitive to poor coverage of the species pool than other popular estimators. The three methods converge on similar estimates of the size and composition of the fauna, suggesting that it comprises around 33,000 species. Of those, 8,600 (26%) were unknown at the start of the inventory and 5,000 (15%) still await discovery. We analyze the taxonomic and ecological composition of the estimated fauna, and show that most of the new species belong to Hymenoptera and Diptera groups that are decomposers or parasitoids. Thus, current knowledge of the Swedish insect fauna is strongly biased taxonomically and ecologically, and we show that similar but even stronger biases have distorted our understanding of the fauna in the past. We analyze latitudinal gradients in the size and composition of known European insect faunas and show that several of the patterns contradict the Swedish data, presumably due to similar knowledge biases. Addressing these biases is critical in understanding insect biomes and the ecosystem services they provide. Our results emphasize the need to broaden the taxonomic scope of current insect monitoring efforts, a task that is all the more urgent as recent studies indicate a possible worldwide decline in insect faunas.

ecology↗

bioRxiv2019

Mismatch of the morphology model is mostly unproblematic in total-evidence dating: insights from an extensive simulation study

Calibrating the molecular clock is the most contentious step in every dating analysis, but the emerging total-evidence dating approach promises increased objectivity. It combines molecular and morphological data of extant and fossil taxa in a Bayesian framework. Information about absolute node ages stems from the inferred fossil placements and associated branch lengths, under the assumption of a morphological clock. We here use computer simulations to assess the impact of mismatch of the morphology model, such as misspecification of character states and transition rates, non-stationarity of the evolutionary process, and extensive variation of evolutionary rates among branches. Comparisons with published datasets suggest that, at least for evolutionary rates typically observed in discrete morphological characters, the total-evidence dating framework is surprisingly robust to these factors. We show that even with relatively low numbers of morphological characters sampled, extensive model mismatch is mostly irrelevant for the performance of the method. The only exception we found are cases of highly asymmetric state frequencies and thus transition rates, but these can be accounted for by appropriate morphology models. In contrast, we find that the temporal scope of fossil sampling has a major impact on divergence time estimates, with the time signal quickly eroding if only rather young fossils are included in an analysis. Our results suggest that total-evidence dating might work even without a good understanding of morphological evolution and that study design should instead focus on an adequate sampling of all relevant fossils, even those with highly incomplete preservation.

evolutionary biology↗

bioRxiv2018

Illustrating phylogenetic placement of fossils using RoguePlots: An example from ichneumonid parasitoid wasps (Hymenoptera, Ichneumonidae) and an extensive morphological matrix

The fossil record constitutes the primary source of information about the evolutionary history of extant and extinct groups, and many analyses of macroevolution rely on fossils that are accurately placed within phylogenies. To avoid misinterpretation of the fossil record, especially by non-palaeontologists, the proper assessment and communication of uncertainty in fossil placement is crucial. We here use Bayesian morphological phylogenetics to evaluate the classifications of fossil parasitoid wasps (Hymenoptera, Ichneumonidae) and introduce RoguePlots to illustrate placement uncertainty on the phylogeny of extant taxa. Based on an extensive, newly constructed morphological matrix of 222 characters in 24 fossil and 103 extant taxa, we test three different aspects of models of morphological evolution. We find that a model that includes ordered characters, among-character rate variation, and a state-space restricted to observed states achieves the highest marginal likelihoods. The individual RoguePlots reveal large differences in confidence in the placement of the different fossils and allow some refinements to their classification: Polyhelictes bipolarus and Ichninsum appendicrassum are moved from an uncertain subfamily placement to Pimplinae, Plectiscidea lanhami is transferred to Allomacrus in Cylloceriinae (Allomacrus lanhami, comb. nov.), Lithotorus cressoni is moved from Diplazontinae to Orthocentrinae, and we note uncertainty in the generic placement of Xanthopimpla? messelensis. We discuss potential artefacts that might result in biased posterior probabilities in Bayesian morphological phylogenetic analyses, pertaining to character and taxon sampling, fossilization biases, and model misspecification. Finally, we suggest future directions both in ichneumonid palaeontology, in the modelling of morphological evolution, and in the way Bayesian phylogenetics can improve both assessment and representation of fossil placement uncertainty.

paleontology↗

bioRxiv2017

Facilitation between plants shapes pollination networks

SignificanceAlthough it is known that plant-plant and plant-pollinator interactions can strongly influence biodiversity and its effects on ecosystem functioning, the details of how competition and facili-tation among plants scale up to mutualistic interactions with pollinators and thus affect pollina-tion networks are poorly understood. We introduce a simple experimental system in which we control local plant interactions, measure pollinator responses and characterize plant-pollinator networks. We find that facilitation among plants produces synergistic and antagonistic effects on the pollinator community affecting the architecture and robustness of plant-pollinator net-works. Our results provide evidence for bottom-up non-additive effects of plant interactions on pollination networks and have implications for the way we study and manage ecosystems.

ecology↗