The Cyprinodontiformes are a diverse group of teleost fishes distributed in temperate, subtropical and tropical, areas of the world; they are common in freshwater systems, but they also occur in brackish and marine waters (Parenti, 1981; Nelson, Grande, & Wilson, 2016). In Asia the Cyprinodontiformes are in Madagascar, Seychelles, India, Sri Lanka, the Indo-Malaysian archipelago, and Java; in Africa around the Mediterranean Sea and from south of the Sahara Desert to South Africa and Madagascar; in Europe, Cyprinodontiformes occur mainly around the Mediterranean Sea, southeastern Spain, Italy, western Greece, and Turkey. In America from southeastern Canada south to Argentina, including the West Indies archipelago (Nelson et al., 2016). These fishes are commonly known as killifishes, topminnows, four-eyed fishes, or toothcarps (Parenti, 1981; Nelson et al., 2004) and are represented by ~2,000 valid species, distributed in 14 families (Fricke, Eschmeyer, & van der Laan, 2020). Cyprinodontiformes are secondary freshwater fishes, and some members can tolerate waters with elevated salinity levels, occasionally using coastal and marine waters for dispersal (Miller, 1966).
Biogeographical patterns of Cyprinodontiformes are complex, especially in Central America, where it has been largely debated (e.g. Miller, 1966; Myers, 1966; Rosen, 1975; Briggs, 1984; Bussing, 1985; Iturralde-Vinent & MacPhee, 1999; Iturralde-Vinent, 2006; Hrbek, Seckinger, & Meyer, 2007; Alda, Reina, Doadrio, & Bermingham, 2013; Bagley et al., 2015; Ho, Pruett, & Lin, 2016; Palacios, Voelker, Rodriguez, Mateos, & Tobler, 2016; Amorim & Costa, 2018). In this regard, the evidence provided by several authors (Myers, 1966; Rosen, 1975; Iturralde-Vinent & MacPhee, 1999; Hrbek et al., 2007; Matamoros, McMahan, Chakrabarty, Albert, & Schaefer, 2015) suggests that Cyprinodontiforms arrived to Nuclear Central America possibly in three dispersal events. The first event is related to ancestral land bridges that connected Northern South America and Northern Central America in the Lower Cretaceous. The second event through the ephemeral GAARlandia Bridge (Iturralde-Vinent & MacPhee, 1999), and the third event linked to the final closing of the Panamanian isthmus (Bacon et al., 2015). Therefore, Central America harbors unique fish communities where the Cyprinodontiformes stand as one of the most relevant groups in both abundance and species richness (Miller, 1966; Matamoros et al., 2015). Indeed, Cyprinodontiforms account for 10% to 20% of the freshwater fish species in the region, a proportion that is even higher if peripheral fishes are excluded (e.g. Matamoros, Schaefer, & Kreiser, 2009; Angulo, Garita-Alvarado, Bussing, & López, 2013; McMahan et al., 2013).
In general, the information on the Cyprinodontiforms of El Salvador is relatively scarce, however, some regional studies include in their analyses distributional data and museum specimens collected in the country (e.g. Miller, 1966; Parenti, 1981; Ghedotti, 2000; Hrbek et al., 2007; Matamoros, Kreiser, & Schaefer, 2012; Morales-Cazan & Albert, 2012; Alda et al., 2013; Palacios et al., 2013; Bagley et al., 2015; Matamoros et al., 2015; Ho et al., 2016; Palacios et al., 2016; Reznick, Furness, Meredith, & Springer, 2017; Amorim & Costa, 2018). Even some specimens have been used as holotypes for species descriptions (e.g. Gill, 1861; Poeser, 1995). These studies provide evidence about biogeographical patterns, morphological traits, and genetic features within and between populations of Cyprinodontiforms in the region. One of the first papers on freshwater fishes of El Salvador was published approximately one hundred years ago (e.g. Hildebrand, 1925), followed by publications over the last decades which provide basic and limited information about taxonomy and distribution (e.g. Burns & Flores, 1981; Phillips, 1981; Burns & Ramirez, 1990; McMahan et al., 2013; Álvarez, Matamoros, & Chicas, 2017; González-Murcia & Álvarez, 2018; González-Murcia, Álvarez, Alvarado-Larios, Marín-Martínez, & Angulo, 2019). However, the information on freshwater fishes of El Salvador is scarce and information gaps are evident.
In El Salvador, the Cyprinodontiformes represents 10% of the freshwater fish diversity (McMahan et al., 2013), and in some watersheds, such as the Acahuapa River, members of this order reach 26% of the total species richness, and 77% of the abundances of the fish assemblage (Álvarez et al., 2017). This highlights the importance of Cyprinodontiforms in Salvadorian freshwater systems. However, the absence of accurate taxonomic keys for the identification of species in El Salvador has generated identification errors and confusion regarding the delimitation of species. Moreover, in recent years important changes in the taxonomy of the group have occurred, as well as new advances in terms of the knowledge about their distributions. Thus, our objectives were a) to present updated taxonomic information on cyprinodontiform fishes from El Salvador, including their geographical distribution and habitat use, and b) to provide a photographic taxonomic key to facilitate their identification.
MATERIALS AND METHODS
Records of cyprinodontiform fishes present in El Salvador were obtained from the scientific literature (Alda et al., 2013; Salgado-Maldonado et al., 2014), voucher specimens at the Museo de Historia Natural de El Salvador (MUHNES), the Instituto de Ciencias del Mar y Limnología, Universidad de El Salvador (ICMARES-UES), Museo Nacional de Ciencias Naturales, Madrid, Consejo Superior de Investigaciones Científicas (MNCN-CSIC) and electronic databases of the United States National Museum (USNM), University of Kansas (KU), Field Museum of Natural History (FMNH), Swedish Museum of Natural History (NRM), California Academy of Sciences (CAS), Tulane University (TU), Louisiana Museum of Natural Science (LSUMZ), and University of Michigan Ann Arbor (UMMZ) accessed via FishNet2 (http://www.fishnet2.org). The information about species composition was gathered and organized to construct a taxonomic key for the Cyprinodontiformes in El Salvador aided by the work of Poeser (1995); Bussing (2002); Miller, Minckley, and Norris (2009); Poeser (2011); Matamoros, Schaefer, Hernández, and Chakrabarty (2012) and Robertson and Van Tassell (2015). Family names are presented in evolutionary arrangement following Fricke et al. (2020) and within the families, the categories of genera and species are sorted alphabetically. English common names are included following Nelson et al. (2004), and Salvadoran Spanish common names are also included following McMahan et al. (2013). Distribution maps by species (see Digital Appendix) and photographs of each species, including both male and female for those species that present sexual dimorphism are presented. Furthermore, distributional data by species are provided. Also, some habitat use characteristics within the Salvadorean ecosystems where species occur are described, according to personal observations and available literature (e.g. Álvarez et al., 2017). Finally, unpublished, and updated data (localities) from the Museo de Historia Natural de El Salvador (MUHNES) and Instituto de Ciencias del Mar y Limnología, Universidad de El Salvador (ICMARES-UES) are included.
RESULTS
A total of 604 museum records of Cyprinodontiforms from El Salvador were compiled. Some records were excluded because they were not identified to the species level, lacked specific geographical information, or their occurrence in El Salvador has not been validated. There were only 350 records with taxonomic information at the species level (Figure 1 and Table 1 Digital Appendix) representing three families, five genera, and 11 species: Profundulidae (2 species), Poeciliidae (8 species), and Anablepidae (one species) (Table 1). Within the family Poeciliidae, Poecilia gillii and P. butleri, as reported by McMahan et al. (2013), were excluded from this revision since recent molecular evidence suggests that these species do not occur in El Salvador (Alda et al., 2013; Ho et al., 2016; Palacios et al., 2016). Poecilia mexicana and P. nelsoni were included since these species occur in the country (Alda et al., 2013; Bagley et al., 2015; Ho et al., 2016; Palacios et al., 2016). For P. gillii, molecular and phylogeographic evidence suggests that this species occurs only in the southern portion of Central America in Panama (Alda et al., 2013; Bagley et al., 2015; Palacios et al., 2016). Therefore, a review of these individuals that have been identified as “P. gillii” is suggested. While P. butleri is geographically separated from its sister taxon P. nelsoni, the distribution of P. butleri is likely restricted to North of the Trans-Mexican Volcanic Belt in northern México (Palacios et al., 2016) while P. nelsoni spans south of the Trans-Mexican Volcanic Belt from Mexico to El Salvador (Ho et al., 2016; Palacios et al., 2016). Therefore, all the records of "P. butleri" were replaced by "P. nelsoni" due to the geographical separation between both sister taxa. For P. mexicana only valid records based on molecular analyses were used (see Alda et al., 2013).
Specie | Records | A | B | C | D | E | F | G | H | I | J | K | Co | L | Elevation (masl) |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Profundulidae | 29 | ||||||||||||||
Profundulus guatemalensis | 8 | x | x | 410-830 | |||||||||||
Profundulus kreiseri | 21 | x | 410-1320 | ||||||||||||
Poeciliidae | 278 | ||||||||||||||
Poecilia marcellinoi | 20 | x | x | x | x | 0-670 | |||||||||
Poecilia mexicana* | 7 | x | x | 0-430 | |||||||||||
Poecilia nelsoni* | 11 | x | x | x | 0-705 | ||||||||||
Poecilia salvatoris | 57 | x | x | x | x | x | x | x | x | 0-950 | |||||
Poecilia sphenops | 72 | x | x | x | x | x | x | x | x | x | x | 0-775 | |||
Poeciliopsis pleurospilus | 66 | x | x | x | x | x | x | x | x | 0-1020 | |||||
Poeciliopsis turrubarensis | 36 | x | x | x | 0-260 | ||||||||||
Pseudoxiphophorus anzuetoi | 9 | x | 260-1140 | ||||||||||||
Anablepidae | 43 | ||||||||||||||
Anableps dowii | 43 | x | x | x | x | x | x | x | 0-960 |
*Recently added to the Salvadoran fish fauna based on molecular studies (Alda et al., 2013; Ho et al., 2016; Palacios et al., 2016). Drainages: A: Río Lempa; B: Río Paz; C: Cara Sucia San Pedro; D: Río Grande de Sonsonate; E: Mandinga Comalapa; F: Río Jiboa; G: Estero de Jaltepeque; H: Bahía de Jiquilisco; I: Río Grande de San Miguel; J: Río Sirama; K: Río Goascorán; Co: Lago de Coatepeque; L: Golfo de Fonseca.
Family Profundulidae: One of the few endemic fish families of Central America and Mexico (Morcillo, Ornelas-García, Alcaraz, Matamoros, & Doadrio, 2016; Matamoros, Domínguez-Cisneros, Velázquez-Velázquez, & McMahan, 2018). This family has been subject to several taxonomic reviews and changes (Morcillo et al., 2016). Previously, the only recognized genus within the family was Profundulus Hubbs 1924, however, molecular studies divided it into the genera Profundulus and Tlaloc Álvarez & Carranza 1951 with eight and four valid species respectively (Matamoros et al., 2018; Flores, 2020; Fricke et al., 2020). In El Salvador, Profundulus is represented by two species; P. guatemalensis and P. kreiseri (McMahan et al., 2013), and both species occur mainly in highland areas of the country. Both species tend to inhabit little disturbed rivers and small streams, and at upper portions of basins occur in habitats characterized by rocky substrates, well-oxygenated waters, moderate to high currents, and surrounding vegetation (riparian forest).
Profundulus guatemalensis (Günther, 1866); “Guatemalan killifish”, “Escamudo guatemalteco”, “Olomina” (Figure 2A). Remarks: Profundulus guatemalensis has been considered a valid species since its original description by Günther (1866). Currently supported at the molecular level, the distribution of P. guatemalensis is restricted to the Pacific Slope of Guatemala and El Salvador (Morcillo et al., 2016) (Fig. 1 in Digital Appendix).
Profundulus kreiseri Matamoros, Schaefer, Hernández, & Chakrabarty 2012; Olomina, Escamudo de Kreiser, Kreiser’s killifish (Figure 2B). Remarks: Profundulus kreiseri was originally described based on material from the Ulúa and Chamelecón Rivers in Honduras (Matamoros, Schaefer et al., 2012). It has been reported in the Atlantic slope in Guatemala and the Pacific slope in El Salvador (McMahan et al., 2013; Morcillo et al., 2016). Its distribution in El Salvador is limited to the north region of El Salvador, in tributaries of the Río Lempa basin (Fig. 1 in Digital Appendix).
Family Poeciliidae: This family is comprised of 274 species, of which ten have been described in the last decade from Middle America (Fricke et al., 2020). The family Poeciliidae is distributed from the South of the United States to the North East of Argentina (Miller et al., 2009), and its greatest diversification occurred in Central America (Rosen & Bailey, 1963; Miller, 1966). Biogeographic studies place the origin of this family in Central and South America (Reznick et al., 2017; Tagliacollo, Duke-Sylvester, Matamoros, Chakrabarty, & Albert, 2017), however, the estimated dates of origin are still debated. In El Salvador three genera are present; Poeciliopsis Regan, 1913, Poecilia Bloch & Schneider, 1801, and Pseudoxiphophorus Bleeker, 1860, with two, five, and one species respectively (McMahan et al., 2013). In general, the species of this family in El Salvador inhabit small rivers, streams, lakes, and lagoons, from clear to disturbed water, rivers and streams with little surrounding vegetation, characterized by substrate mainly composed of rocks, logs, silt, leaves, and sand, shallow waters, and moderate to low currents.
Poecilia marcellinoi Poeser, 1995; “Ilopango molly”, “Chimbolo”, “Bute”, “Olomina”, “Topote de Ilopango” (Figure 2C). Remarks: Poecilia marcellinoi belongs to the subgenus Mollienesia within the P. sphenops species complex (Palacios et al., 2016). The holotype was collected in Lake Ilopango, El Salvador. Poeser (1995) and Palacios et al. (2016) recognize P. marcellinoi as a valid species occurring in the Pacific slope of Guatemala, Honduras, El Salvador, and Nicaragua (Fig. 2 in Digital Appendix).
Poecilia mexicana Steindachner, 1863; “Atlantic molly”, “Chimbolo”, “Bute”, “Olomina” (Figure 2D). Remarks: This species belongs to the subgenus Mollienesia within the P. mexicana species complex (Palacios et al., 2016). Poecilia mexicana was previously considered a synonym of P. sphenops (Rosen & Bailey, 1963). Currently, molecular evidence supports P. mexicana as a valid species, distributed from central Mexico to southern Central America, including El Salvador (Alda et al., 2013; Bagley et al., 2015; Palacios et al., 2016). Its morphological plasticity hinders its identification from other congeneric species (Bagley et al., 2015). We consider that in El Salvador P. mexicana has been misidentified as P. sphenops, P. gillii, P. marcellinoi, and P. salvatoris (Fig. 2 in Digital Appendix).
Poecilia nelsoni Meek, 1904; “Pacific molly”, “Chimbolo”, “Bute”, “Olomina”, “Topote del Pacífico” (Figure 2E). Remarks: Poecilia nelsoni belongs to the subgenus Mollienesia within the P. mexicana species complex (Palacios et al., 2016). Described by Meek (1904) and revalidated by Poeser (2003); some authors considered it a synonym of P. sphenops (Rosen & Bailey, 1963; Lucinda, 2003) or P. butleri (Schultz & Miller, 1971; Parenti, Clayton, & Howe, 1999). Recent molecular studies revealed that P. nelsoni is a sister taxon of P. butleri (Palacios et al., 2016) occurring south of the Trans-Mexican Volcanic Belt (Ho et al., 2016; Palacios et al., 2016) to El Salvador and potentially in Honduras. Therefore, we considered that records of P. butleri in El Salvador by McMahan et al. (2013) corresponds to P. nelsoni and its distribution must be corrected for the Nuclear Middle America region (Fig. 2 in Digital Appendix).
Poecilia salvatoris Regan, 1907; “Salvadoran molly”, “Chimbolo”, “Bute”, “Olomina”, “Topote de El Salvador” (Figure 2F). Remarks: Poecilia salvatoris belongs to the subgenus Mollienesia within the P. mexicana species complex (Palacios et al., 2016); previously considered a synonym of P. sphenops (Rosen & Bailey, 1963). Poeser (1995) recognized P. salvatoris as a morphologically valid taxon, however, some molecular studies suggest that this species might be a morphotype of P. mexicana (Bagley et al., 2015; Ho et al., 2016), therefore, a taxonomic revision is suggested (Fig. 3 in Digital Appendix).
Poecilia sphenops Valenciennes, 1846; “Mexican molly”, “Chimbolo”, “Bute”, “Olomina”, “Topote mexicano” (Figure 2G). Remarks: Part of the subgenus Mollienesia within the P. sphenops species complex (Palacios et al., 2016), the taxonomic status of P. sphenops is supported by both morphological and molecular evidence (Bagley et al., 2015; Palacios et al., 2016). This species occurs south of the Trans-Mexican Volcanic Belt, from Mexico to Nicaragua (Palacios et al., 2016) (Fig. 3 in Digital Appendix).
Poeciliopsis pleurospilus (Günther, 1866); “Largespot livebearer”, “Chimbolo”, “Olomina de manchas”, “Bute de manchas”, “Guatopote manchote” (Figure 2I). Remarks: Poeciliopsis pleurospilus was previously considered as a junior synonym of P. gracilis (Rosen & Bailey, 1963). Subsequently, it was recognized as a valid species (Nelson et al., 2004), occurring in Mexico, Guatemala, Honduras, El Salvador, and Nicaragua (Bussing, 2008; Miller et al., 2009) (Fig. 4 in Digital Appendix).
Poeciliopsis turrubarensis (Meek, 1912); “Barred livebearer”, “Bute con rayas”, “Olomina con rayas”, “Chimbolo”, “Guatopote del Pacífico” (Figure 2H). Remarks: Originally described by Meek (1912). Poeciliopsis turrubarensis occurs in the Pacific slope drainages south of the Trans-Mexican Volcanic Belt in Mexico south to Colombia (Mateos, Sanjur, & Vrijenhoek, 2002; Miller et al., 2009). In El Salvador, it is usually found in the lower basin of rivers and streams (Fig. 4 in Digital Appendix).
Pseudoxiphophorus anzuetoi Rosen & Bailey, 1979; “Anzueto’s killifish”, “Bute”, “Chimbolo”, “Olomina” (Figure 2J). Remarks: Regan (1913) initially considered the genus Pseudoxiphophorus as a subgenus within the genus Heterandria Agassiz 1853, Rosen and Bailey (1963) placed Pseudoxiphophorus in synonymy with Heterandria, while other authors recognized Pseudoxiphophorus and Heterandria as different genera (Hubbs, 1924; Miller, 1974). Based on morphological evidence, the genus Pseudoxiphophorus was recognized as valid and Heterandria remained as a monotypic genus with its only known member H. formosa (Morales-Cazan & Albert, 2012). Recently, all Middle American species of the genus Heterandria were reassigned to the genus Pseudoxiphophorus (Morales-Cazan & Albert, 2012). McMahan et al. (2013) recognized this listed species as H. anzuetoi, and we update its record as P. anzuetoi. This species occurs in El Salvador, Guatemala, and Honduras (Fricke et al., 2020). It is usually found in rivers and streams near Cerrón Grande damming in the middle basin of the Río Lempa (Fig. 5 in Digital Appendix).
Family Anablepidae: This family is represented by a total of 19 species distributed in the Neotropics from Mexico to South America (Fricke et al., 2020). The origin of the family is still debated, with some studies suggesting that the clade originated in the Lower Cretaceous (130-110 Ma), before Africa and South America split (Rosen, 1975; Ghedotti, 2000; Hrbek et al., 2007) or between the Upper Cretaceous and the Early Palaeocene (62-67 Ma) (Reznick et al., 2017). Recent molecular studies suggest that Anablepidae originated in South America during the Oligocene (~29.6 Ma) (Amorim & Costa, 2018), followed by a separation between the oviparous brackish and marine genus Oxyzygonectes Fowler 1916 and the clade comprised by the viviparous anablepids including the brackish and marine genus Anableps Scopoli 1777 and the predominantly freshwater genus Jenynsia Günther 1866 (27.9 Ma), which eventually diverged from each other in the Miocene (12.5 Ma).
Anableps dowii Gill, 1861; “Pacific four-eyed fish”, “Cuatro Ojos” (Figure 2K). Remarks: The holotype of this species was collected in the Bay of La Unión, El Salvador (Gill, 1861). Its distribution range includes Mexico, Guatemala, El Salvador, Honduras, and Nicaragua. It occurs in freshwater, brackish, and marine environments. In El Salvador, A. dowii occurs in many watersheds at an elevation ranging from 0 to 960 masl (Fig. 6 in Digital Appendix). Anableps dowii inhabits coastal lagoons, estuaries, rivers with moderate to low currents. It is usually found in deep waters and wide rivers, substrates mainly composed of sand, silt, and rocks, in open environments with little surrounding vegetation, it is common to observe it on the surface of the rivers.
Key to the Salvadoran species of the Order Cyprinodontiformes:
1a. Head wide and depressed; eyes raised above the top of the head and divided longitudinally, producing two pupils in each eye (Anablepidae; Anableps) ……………………….…………………...... A. dowii
1b. Head small and rounded; eyes not elevated on top of the head and not producing two pupils in each eye; eyes on sides of body……………………………………………………………………………………………...……. 2
2a. Humeral spot present; males without gonopodium; dorsal and anal fins posterior to the transverse half-line of the body; mouth terminal; lower jaw usually longer than the upper jaw (Profundulidae; Profundulus) …………………………………………………………………………………...………………....3
2b. Humeral spot absent; males with gonopodium; dorsal and anal fins anterior or located above of the transverse half-line of the body; mouth superior; jaws of the same size (Poeciliidae)……………………………………………………………………………………….…………………………………...…...4
3a. Oval milky spots on the sides of the body (different from the dark brown spots typical of P. punctatus); preorbital nearly covered with well-developed scales; scales in the caudal fin covering the anterior, up to the middle, portion of the fin; 19-23 caudal-fin rays (very rarely 18 or 24); 17-20 pectoral-fin rays (very rarely 16 or 21)……............................................................... P. guatemalensis
3b. Oval milky spots on the sides of the body absent or not conspicuous; the preorbital region with at least three to four conspicuous scales (not deeply embedded under the skin); scales in the caudal fin that covering only the anterior portion of the fin, not reaching their middle portion; caudal fin with 13-18 rays, pectoral fin with13-16 rays……………………………………………………………...…… P. kreiseri
4a. Reticulated pattern on the body very prominent; the origin of the dorsal fin of the females is located behind the origin of the anal fin; gonopodium long which extends almost to the end of the dorsal fin or nearly to the base of the caudal peduncle; pelvic fins not modified in males………………………………………………………………………………………………………..………..……………….………..5
4b. Reticulated pattern on the body weak; the origin of the dorsal fin of the females commonly above the origin of the anal fin; gonopodium short, rarely reaches half of the dorsal fin; modified pelvic fins in adult males, the tip of the first ray with a soft swelling, second ray thickened (Poecilia)………………………………………………………………………………………………………………………………………..7
5a. Reticulated pattern formed by the scales on the body very prominent (defined dots or vertical bars present); gonopodium rays folded, and thin; without dark pigment at the end of the peduncle (Poeciliopsis)………...............................................................................................................................6
5b. Reticulated pattern formed by the scales on the body very prominent (dark reticulated network); gonopodium rays unfolded, ray tip of sickle-shaped gonopodium; dark pigment at the end of the peduncle present (Pseudoxiphophorus)………................................................... P. anzuetoi
6a. Lateral marks forming 6-9 vertical lines.…………………………………………………………… P. turrubarensis
6b. Lateral marks forming dark spots (usually present) greater than the diameter of the pupil………………………………………………………………………………………………………………….…….. P. pleurospilus
7a. Inner jaw dentition unicuspid……………………………………………………………………………………..…………..8
7b. Inner jaw dentition tricuspid…………………………………………….…………………………………………..….…..10
8a. 18 scales around caudal peduncle……………………………………….……………..................... P. mexicana
8b. 16 scales around caudal peduncle ………………….………………………………………………………...……………9
9a. 9 anal-fin rays; dorsal fin reddish with a black spot on its base (sometimes the size of the entire fin) …….…………………………………………………………………………………………………………………….…. P. salvatoris
9b. 8 anal-fin rays; dorsal and anal fins light yellow………….……………………………………..……... P. nelsoni
10a. 18 scales around caudal peduncle; dorsal and caudal fins with dark spots (pigmented spots), both fins yellow or soft orange……………………………………………………………………………….…… P. sphenops
10b. 16 scales around caudal peduncle; dorsal and caudal fins without black spots, both fins reddish to dark orange; a blotch at the caudal-fin base on scales of caudal-peduncle present………………………………………………………………………………………………………….…………. P. marcellinoi
DISCUSSION
Members of the Cyprinodontiformes are among the most conspicuous fishes in Salvadorian rivers. Some species have very restricted ranges in the country, such as P. guatemalenis, P. kreiseri, and P. anzuetoi. For instance, P. kreiseri occurs in the north side of the country on the border with Honduras and Guatemala in the Río Lempa basin, while P. guatemalensis occurs in the northwest side of the country near the border with Guatemala in the Río Paz and Cara Sucia San Pedro basin. Both inhabit mountain rivers, whereas the distribution of P. anzuetoi appears to be restricted to the middle reaches of the Río Lempa basin, near to Cerrón Grande dam. The rest of the members of the Poeciliidae family and A. dowii are widely distributed in almost all the watersheds of El Salvador. The distribution of A. dowii in freshwater systems in El Salvador is unusual when compared to other countries where this species occurs close to the coasts (Miller et al., 2009; Robertson & Van Tassell, 2015), although there are records at 670 masl in Honduras (Miller, 1979), while in El Salvador this species is found at altitudes above 900 masl.
Within the genus Poecilia, several important taxonomic modifications had occurred that affect the species composition for El Salvador. In this review, five species of the genus Poecilia are considered for El Salvador, which can be differentiated morphologically based on aspects of traditional taxonomy and that is supported by molecular studies. For example, previously P. gillii was considered to be distributed in almost all Central American countries (e.g. Bussing, 2002; Matamoros et al., 2009), however, molecular phylogeographic and systematic work, revealed that the distribution of P. gillii is restricted to Panama, excluding its occurrence in El Salvador (Alda et al., 2013; Bagley et al., 2015; Ho et al., 2016; Palacios et al., 2016). While other molecular studies concluded that P. mexicana is widely distributed in Central Mexico up to Panama on the Pacific and Atlantic slopes (Alda et al., 2013; Bagley et al., 2015; Ho et al., 2016; Palacios et al., 2016). Also, P. nelsoni was separated from P. butleri limiting its distribution north of the Trans-Mexican Volcanic Belt to Sonora, and P. nelsoni from South of the Trans-Mexican Volcanic Belt to El Salvador (Ho et al., 2016; Palacios et al., 2016). However, we recognize P. salvatoris as a morphologically valid species, despite a recent molecular study claims that this taxon could represent a morphotype of P. mexicana and that a review is needed (Bagley et al., 2015; Ho et al., 2016).
It is evident that this group is complex and diverse, and still genetic and morphological studies are necessary for clarifying the taxonomy of some species of this group (mainly of Poecilia genus) for the Mesoamerican region. This research compiled the most recent changes and relevant findings on the taxonomy, systematics, distribution, and habitat use of the Cyprinodontiformes in El Salvador. We recognize that there are still gaps in information and additional studies are necessary to improve our understanding of the freshwater fishes of the country. We hope that this document serves as a tool that facilitates the correct identification of the species both in the field and laboratory for future research.