Jay R. Stauffer

Microsatellite Variation Demonstrates Multiple Paternity in Lekking Cichlid Fishes from Lake Malawi, Africa

The genotypes of two microsatellite loci were determined for the mouthbrooded progeny of 13 females, representing seven species of both rock- and sand-dwelling Lake Malawi cichlid fishes. Multiple paternity is clearly demonstrated for all but two broods. One brood contained the progeny of at least six males. Heterozygosity of these two microsatellite loci in a sample of 18 male Copadichromis cyclicos was 89% and 83%, respectively. Each locus displayed 16 alleles among the 18 males. The expected average exclusion probability using both loci, given a mother/offspring pair, is 0.968, suggesting that microsatellite variation will be useful for quantifying mate choice in these taxa. The low heterozygosity of a Melanochromis auratus brood is consistent with reduced levels of mtDNA polymorphism previously documented in this species. Thus microsatellite variation may provide insight into the genetic history of these populations.

Population structure and colour variation of the cichlid fishes Labeotropheus fuelleborni Ahl along a recently formed archipelago of rocky habitat patches in southern Lake Malawi

Extremely fine–scale genetic partitioning has recently been detected among populations of Lake Malawis rock–dwelling cichlids through the study of microsatellite loci. Understanding the mechanisms of genetic differentiation that operate in this rapidly speciating group requires further investigation of the geographic patterns of gene flow and the congruence between morphological and genetic divergence. In pursuit of this goal, genetic variation at four microsatellite loci and variation in male breeding coloration were examined in several populations of Labeotropheus fuelleborni from southern Lake Malawi. Significant genetic differentiation exists among populations (overall FST = 0.063; p = 0.0002). While migration appears unrestricted within continuous rocky patches, deep waters and sandy bays more than 2 km wide act as strong barriers to gene flow. Dispersal of L. fuelleborni appears to follow a stepping–stone model in which the distribution of habitats often constrains migration to one dimension. It is hypothesized that clinal colour variation in the study area has resulted from the secondary contact of divergent lineages, although reproductive isolation between colour variants is not apparent. Relative to shoreline populations, reduced levels of gene flow among populations inhabiting isolated, deep–water islands provides greater opportunities for drift, adaptation to local conditions, or sexual selection to effect genetic differentiation in this species.

Regional Frameworks and Candidate Metrics for Assessing Biotic Integrity in Mid-Atlantic Highland Streams

Abstract Regionally stratified biological criteria are being used increasingly to assess stream quality. We used multivariate analysis of variance and canonical analysis to examine the utility of two regional frameworks (basins and ecoregions) and 14 candidate metrics of local fish assemblages for assessing the biotic integrity of streams in the mid-Atlantic highlands (montane areas from Pennsylvania to Virginia). In particular, we determined (1) how metrics varied naturally among basins and ecoregions and (2) which metrics varied most consistently with site quality. We also examined the ability of preliminary multimetric indices (MMIs) to distinguish site quality. Metrics varied meaningfully among both basins and ecoregions, but most metrics differed more among basins. The basin effect was especially strong for taxonomic metrics (e.g., number of species [TOTSP]), which reflected the influence of zoogeography on fish community composition. Few metrics differed strongly among both basins and ecoregions. Co...

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

Phenotypic plasticity is the capacity of an organisms 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.

Evaluation of female mate choice cues in a group of lake Malawi Mbuna (Cichlidae)

Abstract The mechanisms that underlie the diversity of cichlids in the East African Great Lakes are poorly understood. Sexual selection through female choice based on male body coloration has often been suggested as a driving force behind the speciation of these fishes. The objectives of this study were to investigate, through mate choice trials, the cues that guide species-isolating female choice. In a group of sympatric Lake Malawi mbuna (rock-dwelling fish), we investigated both visual and chemical cues that might guide female choice by giving gravid females a choice between a heterospecific and a conspecific male. Visual cues, in contrast to olfactory cues, were sufficient to stimulate courtship and thus guide female choice of males. Furthermore, in contrast to other studies on related species, we found that females courted only with conspecifics even if color was not a cue. Species-isolating female choice is likely based primarily on visual information.

Responses of Fish to a Strobe Light/Air Bubble Barrier

Abstract The responses of selected freshwater ( Alosa pseudoharengus, Osmerus mordax, Dorosoma cepedianum ) and estuarine ( Morone americana, Leiostomus xanthurus, Brevoortia tyrannus ) species to air bubbles alone, strobe light alone, and a combined strobe light/ air-bubble barrier were investigated under laboratory conditions. Gizzard shad, alewife and smelt avoided an air-bubble barrier. Avoidance response varied with air-bubble spacing and illumination. All species tested exhibited avoidance behavior to strobe lights, which varied with current velocity, strobe flash rate, and acclimation of fish. Increased avoidance was evident for most species when strobe lights were combined with air bubbles as an exclusion barrier. A combined strobe light/ air-bubble scheme shows potential for application in fish management schemes. Strobe light is more effective than continuous light.

Controlling Vectors and Hosts of Parasitic Diseases Using Fishes A case history of schistosomiasis in Lake Malaŵi

Current estimates of the global prevalence of parasitic diseases range from 600 million cases caused by protozoan and metazoan parasites (Kolberg 1994) to more than 1 billion total cases (Goodman 1994). Strategies for reducing the transmission of these diseases include: immunization programs; reduction of parasite loads in human populations via chemotherapy; modification of cultural practices through public health education, clean water, and sanitation projects; habitat modification (e.g., drainage of stagnant water bodies); and biological and chemical vector and host control (Warren and Mahmoud 1990, WHO 1990). Due Much of the published research on the use of

African Tilapia in Lake NicaraguaEcosystem in transition

L ake Nicaragua contains more than 40 species of fish, including 16 recognized species (Thorson 1976) of native cichlids and additional undescribed cichlids.1 The lake is also inhabited by several large marine predators, such as the bull shark (Charcharhinus leucas), sawfish (Pristis perotteti), tarpon (Tarpon atlanticus), grunt (Pomadasys spp.), and snook (Centropomus parallelus; Thorson 1976). Eleven of the 16 cichlid species are confined to San Juan Province, which contains the lake (Miller 1966). The most heavily exploited fishery resources have traditionally been the native cichlids, estimated currently to constitute 58% of Lake Nicaraguas fish biomass. Lake Nicaragua (Figure 1), the largest (8264 km2) tropical lake outside of Africa (Incer 1976), is lo-

Characteristics that influence male reproductive success on a lek of Lethrinops c.f. parvidens (Teleostei : Cichlidae)

Abstract Sexual selection has long been proposed as a mechanism leading to the diverse cichlid (Teleostei: Cichlidae) fauna of Lake Malawi, Africa. Many of the shallow-water, sand-dwelling, bower-building cichlid species are particularly well suited for studies of sexual selection because they participate in leks. Since females in lekking systems appear to acquire only genetic material from their mates, it has been suggested that leks are ideal systems to study female mate choice. The objectives of the investigation were to examine Lethrinops c.f. parvidens male bower characteristics (i.e., bower size and location) as well as other male characteristics (i.e., length, gular color, and duration on the lek) for their influence on male mating success as measured by the number of visits, circles, and eggs laid by females. These measures are nested in that a visit by a female may or may not lead to circling, and circling by a female may or may not lead to egg-laying. We found increased bower height and higher numbers of conspecific neighbors (analogous to shallow-water, near-shore bower positions) to be positively, significantly associated with the number of visits by females. The only significant correlate with the number of circles was visits, and similarly circles was the only significant correlate with the number of eggs laid. The R2 value for the egg-laying regression was quite low (19.8%) compared with visits (54.3%) and circling (78.9%), suggesting that females may be using additional cues, that we failed to measure, when in close proximity to males or simply that a small proportion of the females were ready to spawn. Both indirect selection and direct selection pressure due to egg predation may have influenced female choice on the lek.

Fishes of the Greenbrier river, West Virginia, with drainage history of the Central Appalachians

The Mississippi river valley was the origin of dispersal of the majority of freshwater fishes east of the Rocky Mountains. The Pliocene Teays river was the major drainage from the east-central United States to the ancestral Mississippi. In the north, the Pittsburgh river flowed northward to join the Pliocene Laurentian river. The advance of Pleistocene glaciation brought about profound drainage reorganization and influenced faunal extinctions through ecological changes. Headwater tributaries, remote from the ice fronts, were less severely affected by these changes and served as refugia. The Allegheny-Ohio river eventually succeeded the Teays river as the major eastern drainage to the Missis- sippi. The New (upper Kanawha) river basin is a remnant of the ancient Teays system. The Greenbrier river, a tributary to New river in West Virginia, was a sub- sequent centre of dispersal of fishes as the Pleistocene ice front receded. Major captures occurred with the Monongahela river to enhance dispersal, but were not limited to that drainage. A total of fifty-three fish species is presently known from the Greenbrier river, with eighteen others listed as expected. The depau- perate fauna is influenced by limiting factors associated with the New river --4-to