New species of Metagonia Simon with directionally asymmetric male and female genitalia (Araneae, Pholcidae)
Abstract
Genital asymmetry is a rare phenomenon in spiders, and directional asymmetry, where all specimens are same-sided, is particularly scarce. In the New World genus Metagonia, only M. mariguitarensis (González-Sponga, 1998) was previously known to be directionally asymmetric. Here we describe three further species in the genus Metagonia that all share directionally asymmetric male and female genitalia: M. embera Huber sp. nov. (Colombia and Panama), M. uca Huber sp. nov. (Colombia), and M. wayuu Huber sp. nov. (Colombia and Venezuela). Metagonia uca is the species with the most extreme asymmetry and also the only species where female asymmetry is not limited to internal structures but extends to the epigynal scape. Interspecific CO1 distances among these four species ranged from 15.5 to 20.9%. Intraspecific distances mostly ranged from 0.0–1.7%, but higher values were found for M. mariguitarensis (up to 9.1%). While the available evidence suggests that directional asymmetry in Metagonia arose only once (in the last common ancestor of the four species above), the origin of the more widespread asymmetry in Metagonia (female antisymmetry) is less clear. We briefly discuss the phylogenetic pattern of antisymmetry in Metagonia, concluding that further focused research is necessary to provide the basic data for such an analysis.
References
Astrin J.J., Huber B.A., Misof B. & Kluetsch C.F.C. 2006. Molecular taxonomy in pholcid spiders (Pholcidae, Araneae): Evaluation of species identification methods using CO1 and 16S rRNA. Zoologica Scripta 35: 441–457. http://dx.doi.org/10.1111/j.1463-6409.2006.00239.x
Carvalho L.S., Dias S.C., Candiani D.F. & Bonaldo A.B. 2010. On the female of Metagonia taruma (Araneae: Pholcidae), ecology of the pholcid spiders in the Urucu River Basin, Amazonas, Brazil and new records from Brazilian Amazonia. Zoologia 27: 431–439. https://doi.org/10.1590/S1984-46702010000300016
Carvalho L.S., Martins P.H., Schneider M.C. & Cabra-García J. 2017. New records of spiders (Arachnida, Araneae) from the state of Roraima, northern Brazil. Check List 13 (1): 2040. https://doi.org/10.15560/13.1.2040
Felsenstein J. 1985. Confidence limits on phylogenies: An approach using the bootstrap. Evolution 39: 783–791. https://doi.org/10.2307/2408678
Ferreira R.L., Souza M.F.V.R., Machado E.O. & Brescovit A.D. 2011. Description of a new Eukoenenia (Palpigradi: Eukoeneniidae) and Metagonia (Araneae: Pholcidae) from Brazilian caves, with notes on their ecological interactions. Journal of Arachnology 39: 409–419. https://doi.org/10.1636/Ha11-03.1
Gertsch W.J. 1971. A report on some Mexican cave spiders. Association of Mexican Cave Studies, Bulletin 4: 47–111.
Gertsch W.J. 1977. Report on cavernicole and epigean spiders from the Yucatan Peninsula. Association of Mexican Cave Studies, Bulletin 6: 103–131.
Gertsch W.J. 1986. The spider genus Metagonia (Araneae: Pholcidae) in North America, Central America, and the West Indies. Texas Memorial Museum, Speleological Monographs 1: 39–62.
González-Sponga M.A. 1998. Arácnidos de Venezuela. Cuatro nuevos géneros y cuatro nuevas especies de la familia Pholcidae Koch, 1850 (Araneae). Memorias de la Sociedad de Ciencias naturales La Salle 57: 17–31.
Helversen O. 1976. Gedanken zur Evolution der Paarungsstellung bei den Spinnen (Arachnida: Araneae). Entomologica Germanica 3 (1/2): 13–28. https://doi.org/10.1127/entom.germ/3/1976/13
Huber B.A. 1997a. Redescriptions of Eugène Simon’s neotropical pholcids (Araneae, Pholcidae). Zoosystema 19 (4): 573–612. https://doi.org/10.5962/p.268855
Huber B.A. 1997b. On American ‘Micromerys’ and Metagonia (Araneae, Pholcidae), with notes on natural history and genital mechanics. Zoologica Scripta 25: 341–363. https://doi.org/10.1111/j.1463-6409.1996.tb00170.x
Huber B.A. 1998. Report of some pholcid spiders collected in Guatemala and Honduras (Araneae, Pholcidae). Revue suisse de Zoologie 105 (1): 49–80. https://doi.org/10.5962/bhl.part.80031
Huber B.A. 2000. New World pholcid spiders (Araneae: Pholcidae): a revision at generic level. Bulletin of the American Museum of Natural History 254: 1–348. Available from http://www.pholcidae.de/PDFs/new_world_pholcidae_2000.pdf [accessed 27 Oct. 2025].
Huber B.A. 2004. Evidence for functional segregation in the directionally asymmetric male genitalia of the spider Metagonia mariguitarensis (González-Sponga) (Pholcidae: Araneae). Journal of Zoology 262: 317–326. https://doi.org/10.1017/S0952836903004709
Huber B.A. 2006. Cryptic female exaggeration: The asymmetric female internal genitalia of Kaliana yuruani (Araneae: Pholcidae). Journal of Morphology 276: 705–712. https://doi.org/10.1002/jmor.10431
Huber B.A. 2010. Mating positions and the evolution of asymmetric insect genitalia. Genetica 138: 19–25. https://doi.org/10.1007/s10709-008-9339-6
Huber B.A. & Meng G. 2024. Old World Micropholcus spiders, with first records of acrocerid parasitoids in Pholcidae (Araneae). ZooKeys 1213: 95–182. https://doi.org/10.3897/zookeys.1213.133178
Huber B.A. & Villarreal O. 2020. On Venezuelan pholcid spiders (Araneae, Pholcidae). European Journal of Taxonomy 718: 1–317. https://doi.org/10.5852/ejt.2020.718.1101
Huber B.A., Rheims C.A. & Brescovit A.D. 2005. Two new species of litter-dwelling Metagonia spiders (Araneae, Pholcidae) document both rapid and slow genital evolution. Acta Zoologica (Stockholm) 86: 33–40. https://doi.org/10.1111/j.0001-7272.2005.00184.x
Huber B.A., Sinclair B. & Schmitt M. 2007. The evolution of asymmetric genitalia in spiders and insects. Biological Reviews 82: 647–698. https://doi.org/10.1111/j.1469-185X.2007.00029.x
Huber B.A., Meng G., Acurio A.E., Astrin J.J., Inclán D.J., Izquierdo M. & Valdez-Mondragón A. 2022. Metagonia spiders of Galápagos: Blind cave-dwellers and their epigean relatives (Araneae, Pholcidae). Invertebrate Systematics 36 (7): 647–678. https://doi.org/10.1071/IS21082
Huber B.A., Meng G., Dupérré N., Herrera M., Inclán D., Wipfler B. 2023. Humpback spiders from Ecuador: Relationships, prosoma ‘inflation’, and genital asymmetry (Araneae: Pholcidae: Mecolaesthus). Invertebrate Systematics 37 (2): 117–151. https://doi.org/10.1071/IS22052
Huber B.A., Meng G., Dederichs T.M., Michalik P., Forman M. & Král J. 2024. Castaways: the Leeward Antilles endemic spider genus Papiamenta (Araneae: Pholcidae). Invertebrate Systematics 38 (2): IS23052. https://doi.org/10.1071/IS23052
Kimura M. 1980. A simple method for estimating evolutionary rate of base substitutions through comparative studies of nucleotide sequences. Journal of Molecular Evolution 16: 111–120. https://doi.org/10.1007/bf01731581
Rivera-Quiroz F.A., Schilthuizen M., Petcharad B. & Miller J.A. 2020. Imperfect and askew: A review of asymmetric genitalia in araneomorph spiders (Araneae: Araneomorphae). PLoS ONE 15 (6): e0220354. https://doi.org/10.1371/journal.pone.0220354
Saitou N. & Nei M. 1987. The neighbor-joining method: A new method for reconstructing phylogenetic trees. Molecular Biology and Evolution 4: 406–425. https://doi.org/10.1093/oxfordjournals.molbev.a040454
Tamura K., Stecher G. & Kumar S. 2021. MEGA 11: Molecular Evolutionary Genetics Analysis Version 11. Molecular Biology and Evolution 38: 3022–3027. https://doi.org/10.1093/molbev/msab120
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