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| Chilomys georgeledecii Brito, Tinoco, García, Koch & Pardiñas Chilomys carapazi Brito & Pardiñas in Brito, Tinoco, Pinto, ... et Pardiñas, 2022. DOI: 10.7717/peerj.13211 |
Abstract
The Andean cloud forests of Ecuador are home to several endemic mammals. Members of the Thomasomyini rodents are well represented in the Andes, with Thomasomys being the largest genus (47 species) of the subfamily Sigmodontinae. Within this tribe, however, there are genera that have escaped a taxonomic revision, and Chilomys Thomas, 1897, constitutes a paradigmatic example of these “forgotten” Andean cricetids. Described more than a century ago, current knowledge of this externally unmistakable montane rodent is very limited, and doubts persist as to whether or not it is monotypic. After several years of field efforts in Ecuador, a considerable quantity of specimens of Chilomys were collected from various localities representing both Andean chains. Based on an extensive genetic survey of the obtained material, we can demonstrate that what is currently treated as C. instans in Ecuador is a complex comprising at least five new species which are described in this paper. In addition, based on these noteworthy new evidence, we amend the generic diagnosis in detail, adding several key craniodental traits such as incisor procumbency and microdonty. These results indicate that Chilomys probably has a hidden additional diversity in large parts of the Colombian and Peruvian territories, inviting a necessary revision of the entire genus.
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| External aspect of Chilomys carapazi sp. nov., in its natural habitat. (painted by Glenda Pozo). |
Family Cricetidae Fischer, 1817
Subfamily Sigmodontinae Wagner, 1843
Tribe Thomasomyini Steadman and Ray, 1982
Genus Chilomys Thomas, 1897
Chilomys carapazi sp. nov. Brito and Pardiñas
Carapaz’s Forest Mouse,
Ratón del bosque de Carapaz (in Spanish)
Etymology: Named in honor of Richard Carapaz Montenegro, an Ecuadorian professional cyclist born in the Provincia de Carchi. The species epithet is formed from the surname “Carapaz,” taken as a noun in the genitive case, adding the Latin suffix “i” (ICZN 31.1.2).
Diagnosis: A species of Chilomys which can be identified by the following combination of characters: Head and body length ~95 mm; dorsal surface of foot covered with round scales and without interspaces; long nasal (~8.5 mm); long diastema (~8.2 mm); M2 with broad hypoflexus (similar in width to mesoflexus); m1 without anteromedian flexid.
Natural history: The type locality is located in the headwaters of the Gualpi River in the lower montane ecosystem (Cerón et al., 1999). The local expression of the montane cloud forest is characterized by a tree canopy that reaches 30 m high. The understory is luxurious and mostly composed of species belonging to Araceae, Melastomataceae, Cyclanthaceae, Bromeliaceae, and ferns. From the same pit falls where Chilomys carapazi sp. nov., was obtained, we also collected the sigmodontines C. georgeledecii, Pattonimus ecominga, Melanomys caliginosus, Microryzomys minutus, Nephelomys cf. pectoralis, and Thomasomys bombycinus, the heteromyid Heteromys australis, the marsupials Caenolestes convelatus, Mamosops caucae, and the soricid Cryptotis equatoris.
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| External aspect of Chilomys georgeledecii sp. nov. (MECN 6024, holotype), an adult male from Reserva Drácula, Carchi, Ecuador. Photograph by J. Brito. |
Chilomys georgeledecii sp. nov. Brito, Tinoco, García, Koch and Pardiñas
Ledeci Forest Mouse,
Ratón del bosque de Ledeci (in Spanish)
Etymology: Named in honor of Czech and US international conservationist George Campos Ledeci, who has worked to promote more environmentally friendly infrastructure development projects in Ecuador and other countries. The species epithet is formed from the surname “Ledeci,” taken as a noun in the genitive case, adding the Latin suffix “i” (ICZN 31.1.2).
Diagnosis: A species of Chilomys which can be identified by the following combination of characters: Head and body length ~83–90 mm; tail longer than head and body length combined (~144.4–177.7%); dorsal surface of foot with round scales and large interspaces; zygomatic plate slightly tilted backwards; M2 with narrow hypoflexus (distinctly narrower than mesoflexus); m1 with anteromedian flexus.
Natural history: Reserva Drácula belongs to the subtropical and lower montane ecosystem (Cerón et al., 1999). The local expression of the cloud montane forest is characterized by a tree canopy that reaches 30 m high. The understory is luxurious and mostly composed of species belonging to Araceae, Melastomataceae, Cyclanthaceae, Bromeliaceae, and ferns. Stomachs from six specimens were dissected to inspect content (Supplemental S4). Sampled C. georgeledecii sp. nov., were insectivorous, preying primarily on fly larva. Identifiable prey items were 50% Diptera, 28.5% Coleoptera, 7.1% Hymenoptera, 7.1% Blattodea, and 7.1% Annelida. From the same pit falls where C. georgeledecii sp. nov., was obtained, we also collected the sigmodontines Chilomys carapazi sp. nov., Pattonimus ecominga, Melanomys caliginosus, Microryzomys minutus, Nephelomys cf. pectoralis, Oecomys sp., Rhipidomys latimanus, Tanyuromys thomasleei, Sigmodontomys alfari, and Thomasomys bombycinus, the heteromyid Heteromys australis, the marsupials Caenolestes convelatus, Mamosops caucae, and Marmosa isthmica, and the soricid Cryptotis equatoris.
Chilomys neisi sp. nov. Brito, Tinoco, García, Koch, and Pardiñas
Neisi Forest Mouse,
Ratón del bosque de Neisi (in Spanish)
Etymology: Named in honor of Neisi Dajomes Barrera, an Ecuadorian athlete weightlifting athlete born in the Provincia de Pastaza; Ecuadorian female Olympic gold medalist. The species epithet is formed from the name “Neisi” taken as a noun in apposition.
Diagnosis: A species of Chilomys which can be identified by the following combination of characters: long nasal (~8.4–8.8 mm); zygomatic plate straight; M1 without anteromedian flexus; M1–M2 with indistinct mesoloph; M2 with narrowed hypoflexus (similar in width to mesoflexus); m1 without anteromedian flexus; hemal arches absent.
Natural history: The zoogeographic area where Chilomys neisi sp. nov., occurs is Temperate (Albuja et al., 2012). The ecosystem corresponds to the montane forest (Ministerio del Ambiente del Ecuador, 2013), which is characterized by trees with abundant orchids, ferns, and bromeliads. Chilomys neisi sp. nov., was collected in mature forest where the undergrowth is visually dominated by herbaceous families such as Poaceae (Chusquea sp.), Araceae, and Melastomataceae. On the steep slopes, the palm (Ceroxylon sp.) predominates. Stomach content from one specimen revealed Coleoptera (one larva), and Chrysomelidae (one adult). Chilomys neisi sp. nov., was collected in sympatry with the didelphids Marmosops caucae Caenolestes caniventer and C. condorensis, and the rodents Akodon mollis, Nephelomys albigularis, Microryzomys minutus, Oreoryzomys balneator, and Thomasomys taczanowskii.
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| External aspect of Chilomys percequilloi sp. nov. (MECN 5854, holotype), an adult male from Cordillera de Kutukú, Morona Santiago, Ecuador. Photograph by J. Brito. |
Chilomys percequilloi sp. nov. Brito, Tinoco, García and Pardiñas
Percequillo Forest Mouse,
Ratón del bosque de Percequillo (in Spanish)
Etymology: This species is named in honor of Alexandre Reis Percequillo (nickname PC), Brazilian contemporary biologist devoted to the study of Neotropical mammal fauna and a specialist in oryzomyine rodents. The species epithet is formed from the surname “Percequillo,” taken as a noun in the genitive case, with the Latin suffix “i” (ICZN 31.1.2).
Diagnosis: A species of Chilomys identified by the following combination of characters: tail with 18–20 rows of scales per centimeter on axis; zygomatic plate sloping backwards; M1–M2 with mesoloph; M2 with broader hypoflexus (similar in width to mesoflexus); m1 with anteromedian flexus; hemal arches present.
Natural history: The zoogeographic area where C. percequilloi sp. nov., occurs is Eastern Sub-Tropical, Temperate and Altoandino (Albuja et al., 2012). The ecosystem corresponds to the montane forest (Ministerio del Ambiente del Ecuador, 2013), which is characterized by trees with abundant orchids, ferns, and bromeliads. Chilomys percequilloi sp. nov., was collected in mature forest where the undergrowth is visually dominated by herbaceous families such as Poaceae (Chusquea sp.), Araceae, and Melastomataceae. On the steep slopes, the royal palm (Dictyocaryum lamarckianum) predominates. Stomach contents of three specimens were analysed. Identifiable prey items were 25% Lepidoptera, 25% Blattodea, 25% Diptera, and 25% Acari (Supplemental S4). Chilomys percequilloi sp. nov., was collected in sympatry with the didelphids Marmosa germana, Marmosops caucae and Monodelphis adusta, and the rodents Akodon aerosus, A. mollis, Nephelomys auriventer, N. nimbosus, Oreoryzomys balneator, Rhipidomys albujai, Thomasomys pardignasi, T. cinnameus, T. erro, and T. salazari.
Chilomys weksleri sp. nov. Brito, García, Pinto and Pardiñas
Weksler Forest Mouse,
Ratón del bosque de Weksler (in Spanish)
Etymology: This species is named in honor of Marcelo Weksler, Brazilian contemporary biologist devoted to the study of living and fossil Neotropical cricetids. The species epithet is formed from the surname “Weksler,” taken as a noun in the genitive case, with the Latin suffix “i” (ICZN 31.1.2).
Diagnosis: A species of Chilomys which can be identified by the following combination of characters: Head and body length ~74–85 mm; tail longer than head and body length combined (~143–153%); dorsal surface of foot with round scales and small interspaces; zygomatic plate leaning forward; M2 with broader hypoflexus (similar in width to mesoflexus); m1 with anteromedian flexus.
Natural history: The zoogeographic area where Chilomys weksleri sp. nov., occurs is Temperate (Albuja et al., 2012). The ecosystem corresponds to the montane forest (Ministerio del Ambiente del Ecuador, 2013), which is characterized by trees with abundant orchids, ferns, and bromeliads. Chilomys weksleri sp. nov., was collected in mature forest where the undergrowth is visually dominated by herbaceous families such as Poaceae (Chusquea sp.), Araceae, and Melastomataceae. The species was collected in sympatry with the didelphids Marmosops caucae, Caenolestes caniventer and C. fuliginosus, and the rodents Akodon mollis, Nephelomys moerex, Microryzomys minutus, Thomasomys aureus, T. baeops, and T. silvestris.
Family Cricetidae Fischer, 1817
Subfamily Sigmodontinae Wagner, 1843
Tribe Thomasomyini Steadman and Ray, 1982
Genus Chilomys Thomas, 1897
Type species (by monotypy).—Oryzomys instans Thomas, 1895.
Etymology.—None originally, but Néstor Cazzaniga (in litteris) suggested that Thomas (1897) employed the Greek noun τιλός (chilos), meaning “grass” to distinguish Chilomys from Oryzomys, whose generic epithet is composed of ὄρσζα (oryza), meaning “rice.”
Geographic distribution.—Known from Andean montane forests and Páramo-forest ecotone from northwestern Venezuela in the north to northern Perú in the south, generally ranging between 1,000 and 4,050 m above sea level.
Chronological distribution.—Recent; no fossils are known.
Contents.—The type species (C. instans) and, in order of nomination, C. fumeus Osgood, 1912, C. carapazi sp. nov. Brito & Pardiñas, C. georgeledecii sp. nov. Brito, Tinoco, García, Koch & Pardiñas, C. neisi sp. nov. Brito, Tinoco, García, Koch, & Pardiñas, C. percequilloi sp. nov. Brito, Tinoco, García & Pardiñas, and C. weksleri sp. nov. Brito, García, Pinto & Pardiñas (this paper).
Conclusions:
After more than a century of stasis in alpha taxonomy an integrative approach supported by extensive field sampling reveals that the poorly-known Andean thomasomyine Chilomys instans constitutes a complex of species. Five new species are described here, from Ecuadorian populations inhabiting montane forests on both sides of the Andes. Preliminarily, the newly revealed diversity can be attributed to allopatric speciation associated with the effect of Quaternary glacial-interglacial cycles on vegetation belts. Chilomys emerges as a morphologically distinctive Andean thomasomyine that exhibits unique specializations related to the procumbency of the incisors and probably associated to an invertebrate feeding strategy.
Jorge Brito, Nicolás Tinoco, C. Miguel Pinto, Rubí García, Claudia Koch, Vincent Fernandez, Santiago Burneo and Ulyses F. J. Pardiñas. 2022. Unlocking Andean sigmodontine Diversity: Five New Species of Chilomys (Rodentia: Cricetidae) from the Montane Forests of Ecuador. PeerJ. 10:e13211. DOI: 10.7717/peerj.13211
