Camm C. Swift

Comparative phylogeography of sympatric sister species, Clevelandia ios and Eucyclogobius newberryi (Teleostei, Gobiidae), across the California Transition Zone

It is paradigmatic in marine species that greater dispersal ability often, but not always, results in greater gene flow and less population structure. Some of the exceptions may be attributable to studies confounded by comparison of species with dissimilar evolutionary histories, i.e. co‐occurring species that are not closely related or species that are closely related but allopatric. Investigation of sympatric sister species, in contrast, should allow differences in phylogeographic structure to be attributed reliably to recently derived differences in dispersal ability. Here, using mitochondrial DNA control region sequence, we first confirm that Clevelandia ios and Eucyclogobius newberryi are sympatric sister taxa, then demonstrate considerably shallower phylogeographic structure in C. ios than in E. newberryi. This shallower phylogeographic structure is consistent with the higher dispersal ability of C. ios, which most likely results from the interaction of habitat and life‐history differences between the species. We suggest that the paradigm will be investigated most rigorously by similar studies of other sympatric sister species, appended by thorough ecological studies, and by extending this sister‐taxon approach to comparative phylogeographic studies of monophyletic clades of sympatric species.

Rangewide microsatellite phylogeography of the endangered tidewater goby, Eucyclogobius newberryi (Teleostei: Gobiidae), a genetically subdivided coastal fish with limited marine dispersal

The federally endangered tidewater goby, Eucyclogobius newberryi, is the most locally differentiated vertebrate with marine dispersal on the California Coast. It inhabits seasonally closed estuaries along the California coast; a habitat heavily impacted by anthropogenic filling and artificial opening, and exhibits varied metapopulation behavior as a consequence of hydrologic variation and anthropogenic impact. We describe 19 taxon-specific microsatellite loci, and assess genetic variation across the taxon range relative to genetic subdivision. A highly divergent southern clade, with reduced genetic variation, now confined to Northern San Diego County, appears to merit status as a separate species. The mid-coast is subdivided into regional groups with overall similarity to, and minor differences from previous mitochondrial sequence based clades. The northernmost region, although locally differentiated, forms a star phylogeny with limited geographic structure which we attribute to dispersal during Pleistocene/Holocene sea-level rise followed by increasing isolation during the Holocene. Bottleneck/founder events are evident in some habitats thought to have experienced (anthropogenic) extirpation. Further work with more, and larger, samples will be required to assess local and regional differences. Analytical methods employed include Analysis of Molecular Variance (AMOVA), Neighbor-Joining, Bayesian/STRUCTURE analysis and Principle Components Analysis (PCA).

The Delta Mudsucker, Gillichthys detrusus, a Valid Species (Teleostei: Gobiidae) Endemic to the Colorado River Delta, Northernmost Gulf of California, Mexico

Substantial genetic and subtle morphological characters document that the Delta Mudsucker or chupalodo delta, Gillichthys detrusus Gilbert and Scofield, 1898, family Gobiidae, is a valid species separate from its widespread sister species, the Longjaw Mudsucker, G. mirabilis Cooper, 1864. This species was erroneously placed in the synonymy of G. mirabilis in 1907 and has since remained unrecognized until this study. The Delta Mudsucker is restricted to a narrow zone of tidally influenced channels of the lowermost Colorado River and adjacent to the mouth of the river within its delta. It is the second fish species endemic to the rivers delta in Mexicos Reserva de la Biósfera del Alto Golfo de California y Delta del Río Colorado (Upper Gulf of California and Colorado River Delta Biosphere Reserve). This study underscores the importance of continued reassessment of baseline and cryptic biodiversity, especially in habitats where initial assessment was scant prior to extensive anthropogenic influence. Caracteres sustancial de genética y caracteres morfológicas sutiles sustentan que el chupalodo delta, Gillichthys detrusus Gilbert y Scofield, 1898, familia Gobiidae, es una especie válida, separada de su especie hermana de amplia distribución, el chupalodo grande, G. mirabilis Cooper, 1864. Esta especie fue erróneamente colocada en la sinonimia de G. mirabilis en 1907 y ha permanecida sin reconocimiento desde entonces hasta este estudio. El chupalodo delta está restringido a una zona angosta, influenciada por la marea, de la parte más baja del delta del Río Colorado en la parte más alto del Golfo de California, y es la segunda especie de pez endémica al delta dentro de la Reserva de la Biosfera del Alto Golfo de California y Delta del Río Colorado. Este estudio subraya la importancia de la revaloración continua de la biodiversidad base y críptica, especialmente en hábitats donde la evaluación inicial fue escasa antes de una influencia antropogénica severa.

A New Species of the Bay Goby Genus Eucyclogobius, Endemic to Southern California: Evolution, Conservation, and Decline.

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.

Long-term Qualitative Changes in Fish Populations and Aquatic Habitat in San Mateo Creek Lagoon, Northern San Diego County, California

Abstract Patterns of abundance were documented for 17 species of fish in the lagoon at the mouth of San Mateo Creek, northern San Diego County, California from occasional observations (1974-1997) and multiple samples per year (1998-2008). Fish populations varied with Mediterranean climate patterns of rainfall, stream flow and consequent breaching of the lagoon to the ocean through the barrier sand berm. Two near-record rainfall seasons occurred during this period; the 1997-1998 El Niño due to southern storms and the 2004-2005 winter wet season of more usual storms from the north and northwest. The lagoon stabilized as fresh to brackish in the dry season and for multiple years during successive drier winters. Closed conditions benefitted the native, federally endangered southern tidewater goby, Eucyclogobius kristinae, but were less suitable for other native estuarine species more common in wetter years. Wet year flows also reduced non-native freshwater species; some thrived and increased predation pressure on the southern tidewater goby. Historically these exotics were absent and two additional native species were present, partially armored threespine stickleback, Gasterosteus aculeatus, and the federally endangered southern steelhead, Oncorhynchus mykiss. Restoring and maintaining a full suite of native species will require a combination of 1) habitat maintenance and restoration, 2) control or management of non-native species, and 3) reintroduction of some native fishes and amphibians.

Expansion of the non-native Mississippi Silverside, Menidia audens (Pisces, Atherinopsidae), into fresh and marine waters of coastal southern California

Abstract Mississippi Silversides, Menidia audens, were first recorded in southern California reservoirs and nearby outflows in the late 1980s and early 1990s. In 1997–2000 they were taken in King Harbor, Redondo Beach, and in 2000 in the Santa Ana River. By 2005–2006 they were found in several other coastal drainages from the San Gabriel River in Orange and Los Angeles counties northward to Arroyo Burro, Santa Barbara County. Initial invasion was via the California Aqueduct in the late 1980s and early 1990s and more recently dispersal has taken place along the southern California coast. The records from King Harbor occurred for a relatively short period, mid-1997-mid-2000 (mostly 1997 and 1998) before they were established in coastal drainages. Their impact on native species is not known but on some occasions Mississippi Silversides have outnumbered native Topsmelt, Atherinops affinis, in small coastal lagoons estuaries. Mississippi Silversides are known to prey on eggs and larvae of other fishes and could be increasing predation on small native animals as well as serving as prey for larger piscivores like steelhead and terns.