Fossils constrain biogeographical history in a clade of flattened spiders with transcontinental distribution

Abstract

Aim Fossil data may be crucial to infer biogeographical history, especially in taxa with tropical trans‐Pacific distributions. Here, we use extinct and extant trochanteriid flattened spiders to test hypotheses that could explain its trans‐Pacific disjunct distribution, including a Boreotropical origin with a North Atlantic dispersal, an African origin with South Atlantic dispersal and an Eurasian origin with Bering Bridge route. Location World‐wide. Taxon Trochanteriidae, Plator‐Doliomalus‐Vectius (PDV) clade. Methods MicroCT was used to collect morphological data from an undescribed Baltic amber fossil. These data were used with additional fossils and extant species in a total‐evidence, tip‐dated phylogenetic analysis. We tested different scenarios using constrained dispersal matrices in a Bayesian approach. An analysis with fossils pruned was also performed to explore how lack of fossil data might impact inferences of biogeographical process. Results The phylogenetic analyses allowed us to place the new fossil in the genus Plator. Analyses without fossils suggest an African origin with a dispersal to Asia from India and a South Atlantic dispersal to South America. When fossils are included, hypothesis‐testing rejects this scenario and equally supports a Boreotropical and an Afro‐European origin with a South Atlantic route and a dispersal to Asia from Europe. Main conclusions Biogeographical inferences of disjunctly distributed taxa should be interpreted with caution when fossils are not included. Although one alternative hypothesis was not completely rejected, results show that the Boreotropical hypothesis for the PDV clade could be a robust explanation for its actual distribution. This hypothesis is mostly overlooked in animal taxa and rigorous tests with other taxa with similar distributions may reveal that a Boreotropical origin is common. We discuss methodological approaches that could improve biogeographical tests using fossils as terminals.

Integrating Fossil Observations Into Phylogenetics Using the Fossilized Birth–Death Model

“…They recommend using the majority rule consensus (MRC) tree instead, as it better represents uncertainty. However, MAP and MCC trees remain commonly used in the literature (Azevedo et al 2021, Chamorro et al 2021.…”

Revision of recluse spiders (Araneae: Sicariidae: Loxosceles) preserved in Dominican amber and a total-evidence phylogeny of Scytodoidea reveal the first fossil Drymusidae

“…Unfortunately, the holotype is preserved in a piece of amber with large fissures that prevent a clear examination of its ventral side, including the palps, the morphology of which has a high taxonomic value. Recently, the use of X-ray micro-computed tomography (µ-CT) and synchrotron radiation micro-computed tomography (SRµ-CT) has been employed to enhance taxonomic descriptions of fossils (e.g., Penney et al 2007Penney et al , 2012Saupe et al 2012) and to reveal morphological details hidden in the piece, or even in completely opaque amber, allowing a better assessment of the systematic placement of the fossil (e.g., Soriano et al 2010;Dunlop et al 2011;Azevedo et al 2021;Solórzano Kraemer et al 2011, 2015, 2022. Thus, the use of this technique might help shed light on the phylogenetic placement of L. aculicaput.…”

“…There are legacy morphological matrices that may be used alongside the newly collected molecular data (e.g., Griswold et al 2005;Labarque and Ramírez 2012;Ramírez 2014). This total evidence approach is useful in testing the placement of taxa for which molecular data is unavailable, such as fossils (e.g., Wood et al 2013;Wood 2017;Mongiardino Koch et al 2021;Azevedo et al 2021;Magalhaes and Ramírez 2022). We thus expect that a phylogenetic analysis including molecular and morphological data is the most straightforward way to test the phylogenetic relationships between the fossils treated here and the extant members of Scytodoidea.…”

The complete mitogenome of Plator insolens (Araneae: Trochanteriidae) with phylogenetic implication

“…Members of this group are commonly known as flattened spiders due to their dorsoventrally flattened bodies which may be an adaptation to life in cracks and under tree barks (Zhu and Zhang 2011 ; Azevedo et al. 2021 ). The mitochondrial genomes have provided valuable insights on the evolution of various animal groups (e.g.…”