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Eucyclogobius kristinae
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Abstract
A geographically isolated set of southern localities of the formerly monotypic goby genus Eucyclogobius is known to be reciprocally monophyletic and substantially divergent in mitochondrial sequence and nuclear microsatellite-based phylogenies relative to populations to the north along the California coast. To clarify taxonomic and conservation status, we conducted a suite of analyses on a comprehensive set of morphological counts and measures from across the range of Eucyclogobius and describe the southern populations as a new species, the Southern Tidewater Goby, Eucyclogobius kristinae, now separate from the Northern Tidewater Goby Eucyclogobius newberryi (Girard 1856). In addition to molecular distinction, adults of E. kristinae are diagnosed by: 1) loss of the anterior supratemporal lateral-line canals resulting in higher neuromast counts, 2) lower pectoral and branched caudal ray counts, and 3) sets of measurements identified via discriminant analysis. These differences suggest ecological distinction of the two species. Previous studies estimated lineage separation at 2–4 million years ago, and mitochondrial sequence divergence exceeds that of other recognized fish species. Fish from Santa Monica Artesian Springs (Los Angeles County) northward belong to E. newberryi; those from Aliso Creek (Orange County) southward constitute E. kristinae. The lagoonal habitat of Eucyclogobius has been diminished or degraded, leading to special conservation status at state and federal levels beginning in 1980. Habitat of the newly described species has been impacted by a range of anthropogenic activities, including the conversion of closing lagoons to open tidal systems in the name of restoration. In the last 30 years, E. kristinae has only been observed in nine intermittently occupied lagoonal systems in northern San Diego County; it currently persists in only three sites. Thus, the new species is in imminent danger of extinction and will require ongoing active management.
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Eucyclogobius kristinae Southern Tidewater Goby has been found in only a few lagoons in San Diego County, making the newly described species critically endangered.
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Eucyclogobius kristinae new species, Swift, Spies, Ellingson and Jacobs
Southern Tidewater Goby.
Eucyclogobius kristinae, Swift, Spies, Ellingson, and Jacobs, new species
urn:lsid:zoobank.org:act:CC641CE5-7DAE-466E-BA3F-D23994068F2B.
Gillichthys mirabilis, Metz 1912:41, misidentification, record from Aliso Creek, Laguna Beach, Orange County.
Eucyclogobius newberryi, Miller 1939, 1943, records from San Juan Creek, Orange County; Swift et al. 1989: 1–19, in part, biology, distribution, illustration; Earl et al. 2010: 103–114, phylogeography, distinctness of southern population; Ruber and Agoretta 2011: 31–41, in part, reanalysis of gobiid molecular phylogeny; Van Tassell 2011: 143, in part, list of Gobiiformes of the Americas.
Eucyclogobius (S), Ellingson et al. 2014: 472, convergence with western Pacific species.
Holotype: LACM 57334–2, female, 29.3 mm SL (Fig 5), California, San Diego County, coastal lagoon at mouth of Las Flores Canyon (Las Pulgas Canyon on some maps), about 15 km northwest of Oceanside
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Fig 5. A, Photograph of holotype of Eucyclogobius kristinae, n. sp., LACM 57334–2, 29.3 mm Standard Length from Las Flores Canyon lagoon on Marine Corps Base Camp Pendleton on 29 July 2011. See text for other data. B, Illustration of pigment patterns and some neuromast lines on the head and body of Eucyclogobius kristinae n. sp., LACM 42639–1, 33 mm SL, Aliso Creek, Orange County, CA.
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Diagnosis: Eucyclogobius kristinae is distinguished morphologically from the only other species in the genus, E. newberryi, by reduction (in fish over about 25 mm SL) of the anterior supraorbital canal and concomitant increase in number of exposed neuromasts (see analyses above), 8–12 in adult E. kristinae vs. 5–8 in E. newberryi (Fig 4B). The Southern Tidewater Goby averages about one fewer pectoral fin ray (18–19 vs. 19–21) and branched caudal rays 10–11 (9–12) vs. 12–13 (11–14) due to reduction in this count on the lower half of the caudal fin (Fig 3B). Morphologic measures proved efficiently diagnostic in combination (Fig 1B–1F). These include a longer anal spine and measures that contribute to greater girth, more anterior placement of pelvic fins and a more upturned mouth in E. kristinae, while E. newberryi has a more elongate snout with a more terminal mouth, longer pectoral fins and somewhat more elongate dorsal, anal, and caudal fins. Numerous fixed molecular characters have been identified between the two species, both in mitochondrial sequence, as well as in dramatic length difference and amplification of microsatellite loci. Thus, there are many means of efficient molecular diagnosis via PCR amplification assay.
Etymology: The species name is feminine in honor of Kristina D. Y. Louie whose untimely death in 2004 cut short a promising career dedicated to conservation genetics. Her Ph.D. dissertation and associated work contributed greatly to our studies of eastern Pacific phylogeography, as well as to a novel re-interpretation of the placement of Wallace’s Line across the islands of Indonesia.
Conclusions:
The Southern Tidewater Goby, Eucyclogobius kristinae, has a history of genetic isolation (≥ 1 million years) from its sister, E. newberryi, from which it is separated by a geographic break across the Los Angeles Basin. It can be reliably diagnosed on the basis of meristics —e.g. exposed anterior supraorbital neuromasts on adults (Fig 4, neuromast row no. 1) and higher pectoral fin-ray counts in E. newberryi —as well as morphometric characters as identified by discriminant function analyses. Sequencing of mitochondrial control region or cytochrome b or amplification of any of the suite of microsatellite markers can also provide easy diagnosis, and simple PCR assays for species determination can be easily devised. Morphological distinctions suggest adaptations to a more benthic mode of life in E. kristinae. Sexual dimorphism associated with an enlarged jaw in adult males is presumptively used in mating burrow construction. Further work to better establish ecological distinction, sexual dimorphism, and/or behavioral differences between the two species is merited. E. kristinae is critically endangered as it appears to persist in only three sites based on the most recent surveys. Thus, immediate action is needed to prevent extinction of the species during California’s current and persistent drought. All management units of E. newberryi and E. kristinae should maintain state and federal endangered status until recovery has been demonstrated.
Camm C. Swift, Brenton Spies, Ryan A. Ellingson and David K. Jacobs. 2016. A New Species of the Bay Goby Genus
Eucyclogobius, Endemic to Southern California: Evolution, Conservation, and Decline.
PLoS ONE. 11(7); e0158543. DOI:
10.1371/journal.pone.0158543
