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Povzetek: Island systems provide excellent arenas to test evolutionary hypotheses pertaining to gene flow and diversification of dispersal-limited organisms. Here we focus on an orbweaver spider genus Cyrtognatha (Tetragnathidae) from the Caribbean, with the aims to reconstruct its evolutionary history, examine its biogeographic history in the archipelago, and to estimate the timing and route of Caribbean colonization. Specifically, we test if Cyrtognatha biogeographic history is consistent with an ancient vicariant scenario (the GAARlandia landbridge hypothesis) or overwater dispersal. We reconstructed a species level phylogeny based on one mitochondrial (COI) and one nuclear (28S) marker. We then used this topology to constrain a time-calibrated mtDNA phylogeny, for subsequent biogeographical analyses in BioGeoBEARS of over 100 originally sampled Cyrtognatha individuals, using models with and without a founder event parameter. Our results suggest a radiation of Caribbean Cyrtognatha, containing 11 to 14 species that are exclusively single island endemics. Although biogeographic reconstructions cannot refute a vicariant origin of the Caribbean clade, possibly an artifact of sparse outgroup availability, they indicate timing of colonization that is much too recent for GAARlandia to have played a role. Instead, an overwater colonization to the Caribbean in mid-Miocene better explains the data. From Hispaniola, Cyrtognatha subsequently dispersed to, and diversified on, the other islands of the Greater, and Lesser Antilles. Within the constraints of our island system and data, a model that omits the founder event parameter from biogeographic analysis is less suitable than the equivalent model with a founder event.
Ključne besede: biogeography, spiders
Objavljeno v DiRROS: 23.07.2024; Ogledov: 92; Prenosov: 72
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Povzetek: Aim A wholistic biogeographical reconstruction should combine a phylogeny with specifics of organismal biology, plate tectonics and consequent probabilities of historic dispersal events. Here, we demonstrate this approach by reconstructing the geographical origin and sequence of intercontinental colonization of the golden orbweaving spiders, a global clade. We test two alternative hypotheses about their ancestral range. Due to the highest contemporary species diversity in Africa, the ‘Out of Africa’ hypothesis predicts the Afrotropics as their most likely ancestral area. The alternative, ‘Out of West Burma’ hypothesis aims to explain a Burmese amber fossil as stem nephilid. Because the West Burma block probably detached from Australia, then rafted towards Laurasia, either on its own or with India, this hypothesis predicts either Australasia or Indomalaya (or both) as the ancestral area. Location Worldwide. Taxon Golden orbweaving spiders, family Nephilidae. Methods We construct an expanded phylogeny of nephilid spiders and apply RASP (Reconstruct Ancestral State in Phylogenies) to infer their global biogeographical history. We fit the data to six integrated biogeographical models: DEC, DIVALIKE, BAYAREALIKE and their +j variants. We fine-tune the analysis by evaluating varying probabilities of dispersal between geographical areas throughout the clade's evolutionary history. We use the physical distance between the areas as a proxy for dispersal probabilities, thus accounting for plate tectonics. Results The best supported model reconstructs both Australasia and Indomalaya as ancestral area. In several parts of the phylogeny, these areas persist for the estimated 130-million-year evolutionary history. However, numerous intercontinental shifts in nephilid biogeographical history are also inferred. Since nephilid origins are clearly Gondwanan, our study supports the interpretations that Burmese amber contains Gondwanan biota. Main conclusions These results are consistent with the Out of West Burma hypothesis but reject the Out of Africa hypothesis. That certain clades persist in their ancestral ranges while others may shift continents aligns well with the known nephilid biology. Our methodological approach that assesses organismal specific dispersal probabilities through concrete distances measured though time slices of the Earth's history can be applied to biogeographical reconstruction of any lineage.
Ključne besede: spiders, golden orbweavers, Nephilidae, reconstruction of lineage, biogeography
Objavljeno v DiRROS: 22.07.2024; Ogledov: 97; Prenosov: 132
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Povzetek: Higher-level classifications often must account for monotypic taxa representing depauperate evolutionary lineages and lacking synapomorphies of their better-known, well-defined sister clades. In a ranked (Linnean) or unranked (phylogenetic) classification system, discovering such a depauperate taxon does not necessarily invalidate the rank classification of sister clades. Named higher taxa must be monophyletic to be phylogenetically valid. Ranked taxa above the species level should also maximize information content, diagnosability, and utility (e.g., in biodiversity conservation). In spider classification, families are the highest rank that is systematically catalogued, and incertae sedis is not allowed. Consequently, it is important that family level taxa be well defined and informative. We revisit the classification problem of Orbipurae, an unranked suprafamilial clade containing the spider families Nephilidae, Phonognathidae, and Araneidae sensu stricto. We argue that, to maximize diagnosability, information content, conservation utility, and practical taxonomic considerations, this “splitting” scheme is superior to its recently proposed alternative, which lumps these families together as Araneidae sensu lato. We propose to redefine Araneidae and recognize a monogeneric spider family, Paraplectanoididae fam. nov. to accommodate the depauperate lineage Paraplectanoides. We present new subgenomic data to stabilize Orbipurae topology which also supports our proposed family-level classification. Our example from spiders demonstrates why classifications must be able to accommodate depauperate evolutionary lineages, e.g., Paraplectanoides. Finally, although clade age should not be a criterion to determine rank, other things being equal, comparable ages of similarly ranked taxa do benefit comparative biology.
Ključne besede: classification, family rank, phylogenomics, systematics, monophyly, spider phylogeny, zoology
Objavljeno v DiRROS: 12.07.2024; Ogledov: 116; Prenosov: 103
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