Diets and Diet Overlap of Nonindigenous Gobies and Small Benthic Native Fishes Co-inhabiting the St. Clair River, Michigan

We examined the relationship between structure of fish communities and 11 environmental variables in floodplain lakes from the Middle Araguaia River, Brazil. Samples were collected at the beginning and at the end of the dry season in standardized surveys of six seasonally isolated lakes and six lakes permanently connected to the river mainstem. Canonical correspondence analysis revealed that among the environmental descriptors of lakes, only Secchi transparency and maximum depth were significantly related to fish community structure. Most of the patterned variation in community structure was associated with marked seasonal changes in lake transparency (means: early dry season=90.8 cm; late dry season = 33.2 cm) and depth (means: early dry season = 4.6 m; late dry season = 2.0 m). Visually oriented fishes had highest abundance in clear lakes, whereas fishes with adaptations to low visibility were most abundant in turbid lakes. The type of isolation of lakes from the river channel had no apparent effect on community structure. The results suggest that sensory adaptations for detection of prey under prevailing optical conditions play a major role in the organization of these communities, as predicted by a model of fish community organization originally developed for floodplain lakes of the Orinoco River, Venezuela.

Fish community structure in relation to environmental variation in floodplain lakes of the Araguaia River, Amazon Basin

Phenotypic plasticity is the capacity of an organism's phenotype to vary in different environments. Although diet-induced phenotypic plasticity has been documented in New World cichlids, it has been hypothesised that this type of plasticity would be limited in certain Old World cichlids, because of the morphological constraints on the jaw imposed by mouth-brooding. This hypothesis was experimentally tested by determining the effect of different diets on the head and jaw morphology of split broods of several species of haplochromine cichlids from Lake Malaŵi, Africa, and two substrate-spawning cichlids, one from the Old World, Tilapia mariae (Boulenger), and one from the New World, Herichthys cyanoguttatum (Baird and Girard). Different feeding regimes resulted in differences in head morphologies in both New and Old World cichlid species. Although Old World mouth-brooding haplochromine cichlids exhibited phenotypic plasticity, the magnitude of head-shape plasticity observed was greater in the New World substrate-spawning cichlid, H. cyanoguttatum . The Old World tilapiine cichlid, T. mariae , did not exhibit phenotypic plasticity of head morphology. Experiments with modified foods demonstrated that the observed changes were unrelated to dietary nutrition, but were a result of differing feeding modes. Phenotypic plasticity might have contributed to the extensive trophic radiation and subsequent explosive speciation observed in Old World haplochromine cichlids. The existence of phenotypic plasticity has implications for morphology-based species descriptions as well.

Phenotypic plasticity: its role in trophic radiation and explosive speciation in cichlids (Teleostei: Cichlidae)

Microhabitat use and habitat partitioning for 10 darter species (Percidae: Etheostomatini) were studied by direct observation (snorkeling) at five sites in the Elk River drainage, West Virginia, U.S.A. We used canonical discriminant analysis and univariate tests to determine microhabitat variables that were important in segregating species. Darter species were segregated by depth, substrate size, and water velocity. In addition, Percina typically occurred in the water column, whereas species of Etheostoma were benthic and segregated by occurring under, between, and on top of rocks.

Habitat partitioning in a community of darters in the Elk River, West Virginia

The Ozark madtom, Noturus albater, is distributed in upland streams in the upper White, Black, and St. Francis rivers of Missouri and Arkansas, USA. Fixed chromosomal and biochemical differences between populations in the upper White River and the Black and St. Francis rivers led earlier researchers to suggest that the Ozark madtom comprised two distinct species. The current study reviewed previous data, and examined osteology, pigmentation, morphometrics and DNA sequences from the mitochondrial cytochrome b gene and the nuclear Recombination Activating Gene 2. Sequence data were analysed using parsimony and Bayesian methods to construct a phylogenetic hypothesis of relationships within Noturus and examine relationships of populations of Ozark madtoms. Results of the molecular analyses were consistent with earlier chromosomal and biochemical studies. Morphology could not distinguish between populations from the upper White River and populations from the Black and St. Francis rivers. However, karyotypes, allozyme variation, and DNA sequences all provide diagnostic characters demonstrating the presence of two species consistent with the phylogenetic species concept. We describe the populations from the Black and St. Francis rivers as Noturus maydeni, a new cryptic species of madtom catfish.

The challenge of truly cryptic diversity: Diagnosis and description of a new madtom catfish (Ictaluridae: Noturus)

Habitat partitioning among eleven species of darters (Percidae: Etheostomatini) from the Allegheny River system was studied through underwater observation. Percina caprodes and Percina copelandi showed consistent segregation from Etheostoma by occupying deeper habitats. Substrate size, depth, and water velocity were important variables by which Etheostoma species segregated. Analysis of niche breadth values indicated that species differed widely in their degree of specialization in habitat use; based on the variables measured, Etheostoma zonale was a habitat generalist whereas Etheostoma camurum, Etheostoma tippecanoe, and Percina caprodes tended towards habitat specialization. Habitat segregation appears to be an important mechanism allowing the coexistence of these closely related and ecologically similar species. Microhabitat quantification on a fine scale was important in discovering habitat differences in this diverse system.

/pdf/microhabitat-partitioning-in-a-diverse-assemblage-of-darters-j7fbwdkkwj.pdf

Microhabitat partitioning in a diverse assemblage of darters in the Allegheny River system

A new species of darter in the genus Etheostoma (Teleostei: Percidae) and subgenus Nothonotus is described from the upper Tennessee River. The new species closely resembles Etheostoma tippecanoe and was historically regarded as a distinct population. The presence of 1-4 scales on the cheek, a light transverse bar directly anterior to the dorsal-fin origin, and fewer scales in the lateral series distinguishes the new species from E. tippecanoe. THE subgenus Nothonotus (Bailey and Etnier, 1988) is considered to be monophyletic (Page, 1981) and is characterized by the following synapomorphies: slab-sided body shape, darkened anterior membranes in the spinous portion of the dorsal fin, and horizontal lines on the lateral sides (Bailey and Etnier, 1988). The smallest member of the subgenus is Etheostoma tippecanoe, which differs from the other Nothonotus by consistently having an incomplete lateral line (Bailey and Etnier, 1988). Etheostoma tippecanoe was described by Jordan and Evermann (1890) from the Tippecanoe River, Marshland, Indiana. In their review of the type specimens of the darters, Collette and Knapp (1966) designated a lectotype (USNM 40080) and paralectotype (USNM 197919) and concluded that the larger of the remaining syntypes (UMMZ 187513) was Etheostoma camurum and the smaller one was most probably E. camurum as well.

/pdf/new-species-of-etheostoma-teleostei-percidae-from-the-upper-2szrkapjy9.pdf

New Species of Etheostoma (Teleostei: Percidae) from the Upper Tennessee River

New Species of Petrotilapia (Teleostei: Cichlidae) from Lake Malaŵi, Africa@@@New Species of Petrotilapia (Teleostei: Cichlidae) from Lake Malawi, Africa

Interpopulation variation in oocyte production of darter species from three tributaries of the Allegheny River system was examined. Significant differences across localities for numerous darter species were identified. Several potential biotic and abiotic ecosystem attributes such as competition and water quality constituents differed across the study sites and may influence oocyte production. This study demonstrates the importance of including several populations in life history studies in order to describe the intraspecific range of oocyte production.

Ellen S. van Snik

Papers

Microhabitat partitioning in a diverse assemblage of darters in the Allegheny River system

New Species of Etheostoma (Teleostei: Percidae) from the Upper Tennessee River

New Species of Petrotilapia (Teleostei: Cichlidae) from Lake Malaŵi, Africa@@@New Species of Petrotilapia (Teleostei: Cichlidae) from Lake Malawi, Africa

Interpopulation Variation in Darter Oocyte Production