Organismic Ecology II Posters
Presiding: E Marti, Centre d'Estudis Avancats de Blanes (CSIC); C Hoagstrom, South Dakota State University
NB33P-01 1330h
Mussel Assemblages Below a Dam: High Density, Large Size and Low Recruitment
We examined the demographic structure of mussel assemblages at three locations in the St. Croix River watershed, Wisconsin and Minnesota between 1998-2004. One assemblage, below a small dam on a tributary (Sunrise River), has 113 mussels/m2. On the mainstem, Wild River (not below a dam) and Interstate Park (below a larger dam) have 21 and 24 mussesl/m2, respectively. There is little recruitment at Sunrise and mussels are larger than those at mainstem sites. Larger size is apparently due to higher growth rates at this site. Low recruitment may be due to competition for space with adults. Live and dead mussels comprise much of the substrate at Sunrise with living mussels occupying 23-60% of available space, compared with <5% at the mainstem sites. Course stable sand, thought to be important juvenile habitat, accounts for 35% of the substrate at Sunrise compared with 41-64% at the mainstem sites. Preliminary qualitative data from two other sites below small dams on tributaries indicate similar patterns of high density, large mussel size and little recruitment. Variable recruitment at sites below small dams coupled with long lifespan of mussels (decades) could have profound influences on management decisions to maintain or remove dams.
NB33P-02 1330h
Longitudinal Changes in Physical Habitat and Macroinvertebrate Assemblages Along a Neotropical Stream Continuum
Information on the structure and function of upland Neotropical streams is lacking compared to many other regions. We examined habitat characteristics and macroinvertebrate assemblages along an 8-km stretch of a stream originating on the continental divide in central Panama in order to examine patterns along a stream continuum. Wetted width and discharge ranged from 1 m and 18 L/s, respectively in the uppermost headwaters to 12 m and 1,580 L/s, respectively at the lowest reach examined. Percent substrate composition showed a decrease in fine particle sizes from upper headwater reaches (38%) to the lowest reach (10%). A total of 61 macroinvertebrate taxa were identified along the continuum, with more taxa present in lower reaches (45) compared to headwaters (28), but responses of individual groups varied. Trichoptera, Ephemeroptera, and Diptera richness increased from headwaters to the lowest site, whereas Hemiptera and Coleoptera richness decreased along the gradient. Collector-gatherers and predators were the dominant functional groups (~70% of total abundance) and changed little across sites. Shredder abundance was highest in headwaters (15% of total), while scrapers (20%) and collector/filterers (11%) peaked in the lower reaches. These patterns suggest that upland streams in this region follow basic tenets of the River Continuum Concept.
NB33P-03 1330h
Host-Fish Identification and Early Life Thermal Requisites of the Federal Endangered Winged Mapleleaf Mussel (Quadrula fragosa)
The winged mapleleaf mussel (Quadrula fragosa) is a federal endangered species with only one known reproducing population. Controlled propagation is needed to aid in recovering this species, but little is known of its specific early life-history requirements, including the identity of host-fish that facilitate transformation of its parasitic glochidia (larvae) into free-living juveniles. In autumn 2003, we initiated three winged mapleleaf host-fish identification tests that were each conducted in different thermal regimes. Results of the two shorter-term tests at warmer temperatures identified blue catfish (Ictalurus furcatus) and channel catfish (I. punctatus) as suitable host-fish species. Close examination of these test data allowed us to empirically estimate: the minimum daily mean water temperature (9.24°C) required for glochidia to grow and develop into juveniles; and the cumulative water temperature units of net daily growth (395°C• d)needed to initiate peak juvenile recovery. We applied these findings to the longer-term third test and predicted with great accuracy (±7 d) the initial date of peak juvenile mussel recovery after >8 months development in a colder, more natural thermal regime. Our final results also indicated a consistent daily temperature >17°C is needed to trigger the large-scale release of winged mapleleaf juveniles from the gills of host-fish.
http://news.fws.gov/NewsReleases/showNews.cfm?newsId=4578EB48-5A4A-4A20-9F99627C4C331B84
NB33P-04 1330h
A Habitat Suitability Model for Selected Crayfish Species in Lancaster County,Pennsylvania, Streams
The introduction of invasive exotic species to previously inaccessible areas provides the opportunity to study the impacts of invasive species on closely related native species. Habitat suitability index [HSI] models offer a coarse estimate of the habitat quality relative to hypothesized physiological tolerances of a species. The distribution and abundance of two native [Orconectes obscurus and Cambarus bartonii] and one invasive [Orconectes rusticus] crayfish along a twenty-three mile length of a Lancaster County, PA, stream and various physical factors at the sample sites were provided by a recent survey (Wagner et.al. unpublished). Of the factors provided, stream width, velocity, pH, and temperature were considered as the factors defining the geographic range of each species. An HSI model was constructed based on these factors to identify regions offering suitable habitat for a species and areas of a stream which are at risk for invasion of O. rusticus. Current work involves the development of subindices describing the availability of food and shelter within the stream, using stream order, link magnitude, and substrate measurements. The HSI model will be coupled to a model describing the interactions between size-structured populations of native and invasive species under the influence of a predator.
NB33P-05 1330h
Plasticity as Phenotype: G x E Interaction in a Freshwater Snail
Plasticity in morphological development allows species to accommodate environmental variation experienced during growth; however, genetic variation for phenotypic plasticity per se has been relatively under-studied. We utilized the well-documented plastic response of shell development to predator cues in a freshwater snail to quantify genetic variation for plasticity in growth rate and shell shape. Field-caught pairs of snails reproduced in the laboratory to create families of full siblings, which were then divided and allowed to grow in control and predator cue treatments. Predator (crayfish) cues had significant effects on both size-corrected growth rate and shell shape; family identity also significantly affected both final shell shape and growth rate. The interaction between predator treatment and family identity significantly affected snail growth rate but not final shell shape, suggesting genetic variation in the plastic response to predator cues for a physiological variable (growth rate) but not for a variable known to mechanically reduce the risk of predation (shell shape), at least in this population of snails. The possibility that risk of multiple modes of predation (i.e., both fish and crayfish) in some populations might maintain genetic variation in morphological plasticity is discussed.
NB33P-06 1330h
Morphological Variation in the New Zealand Mud Snail (Potamopyrgus antipodarum).
The New Zealand mud snail (Potamopyrgus antipodarum) is a morphologically diverse species, showing variation in body shape and spine ornamentation. Native to New Zealand, the snail is highly invasive in the United States and Europe. As part of a broader study examining the role of morphological variation in hydrodynamic performance, we sought to quantify shell variation in snails from four different populations in New Zealand. Shells were mounted and photographed, and four characters (shell length and width, and aperture length and width) were digitized. Shell length differed significantly among populations. Sheared PCA revealed that shell shape, defined in terms of overall robustness (PC1) as well as the ratio between shell width and aperture width (PC2), also differed significantly among populations. Spined shells differed significantly from smooth shells with respect to shell shape (PC1 and PC2), with spined shells being generally more robust with larger apertures for their length. Shell shape differed significantly between spined and smooth shells in the two lotic habitats but not in the lentic habitats, suggesting a possible interaction between shell shape, presence of spines, and hydrodynamic environment. Further research will attempt to relate shell morphology and spine ornamentation to hydrodynamic drag and lift forces.
NB33P-07 1330h
Feeding Preferences of the Larval Southern Two-Lined Salamander, Eurycea Cirrigera, in an Impacted Agricultural Area, Southwest Georgia.
Feeding preference of the stream-dwelling Southern Two-lined Salamander, Eurycea cirrigera, was examined in streams affected by agricultural practices in southwest Georgia. Larvae were collected within bimonthly benthic macroinvertebrate samples from February 2002 to February 2003. Five stream reaches were sampled, two of which were fenced from cattle and three allowed cattle access. Forty larvae were recovered from the invertebrate collections, with significantly higher captures at fenced sites than unfenced sites. The entire digestive tract was removed from larvae and stomach contents were examined to better understand prey selection in streams with differing intensities of adjacent agricultural land-use. Invertebrates were enumerated in 34 salamander stomachs, with Chironomidae comprising the largest percentage of individuals found, both in stomach contents and habitat collections. Electivity values showed a wide range of variability among individual salamanders, however, overall indices suggest slight positive selection for a subfamily of the Chironomidae, the Tanypodinae. It appears that E.cirrigera larvae select for Tanypodinae, however, this invertebrate group was found at all stream sites, suggesting factors other than prey abundance, such as stream habitat quality, may also influence larval salamander abundance.
http://www.jonesctr.org
NB33P-08 1330h
Use of Biomechanical Analyses of Cranial Variation to Interpret Feeding Components of the Niche in Larval Dytiscid Beetles (Coleoptera: Dytiscidae)
Dytiscid larvae are obligatory predators with most using extra-oral digestion to feed on aquatic invertebrates and small vertebrates. Three aspects of cranial morphology are presented here to illustrate the strong selective force feeding success has on cranial morphology. First, distortion gird analysis of ontogenetic allometry revealed significant changes in Agabus disintegratus during larval development. These differences are most likely the result of ontogenetic shifts in prey preferences in A. disintegratus leading to anisomorphic increases in mandibular musculature during development. Second, evolutionary allometry of lateral head shape in larvae of Matus bicarinatus, Coptotomus lenticus, and Thermonectus basilaris revealed prognathic, hypoprognathic and hyperprognathic patterns of orientation. This variation in cranial architecture may be an indicator of differences in prey regimes exploited by each taxon. And third, geometric analysis of mandibular shape to predict the food habits of Acilius mediatus, Agabus punctatus, and Rhantus calidus revealed significant differences in camber, arc, and angle of attack. These data indicate that mandibular geometry may be strongly influenced by prey choice. Biomechanical methods could have predictive value for identifying larval food habits. This project was supported by a Faculty Research Grant, Office of Research Services, GC&SU. Aquatic Coleoptera Laboratory Contribution No. 61
NB33P-09 1330h
Springs in Time: Fish Faunal Changes in Oklahoma Springs Over a 20-Year Interval
Springs face a number of threats affecting water quality, habitat characteristics, and biodiversity. Despite these threats and the occurrence of spring-endemic species, temporal changes in spring biota have been little studied. We compared among-year changes in 22 Oklahoma springs with fish that were sampled in 1981 and 1982, and again in 2001, after 20 years. Although flow reduction from groundwater use is a major threat to springs, we found little evidence of flow impacts in these fish-containing springs. Flow reduction was not a major threat because springs may have been impacted prior to the study and springs containing fish were in areas with low groundwater water use (although some of these springs are threatened by proposed large-scale groundwater sales). Twenty-year assemblage differences were correlated with physical alteration of specific springs and the introduction of fish. These introductions were possible because of alterations that deepened habitats. Between-year variation in spring fish assemblages was affected by movement of species in and out of springs. The distinctive fish fauna in 1982 was correlated with unusually high spring rains and the resultant greater connectivity between springs and streams.
NB33P-10 1330h
Stoneflies (Plecoptera) of the Gunnison Basin: A Geographical Study of Current Versus Historical Distributions.
We compared the stonefly diversity sampled from 11 selected sites in the Gunnison River Basin over the last three years to the stonefly diversity recorded by Knight (1965) from the same or nearby sites. The 11 sites in this study were chosen from the 22 sites reported by Knight (1965) because they represented mainstem Gunnison River sites that would be predicted to experience the most alteration due to anthropogenic changes such as the construction of impoundments, differences in land use patterns, and effects from the increase in human population of the region. We have been unable to locate ten of the stonefly species that were historically found and we presume that they have gone locally extinct or have become increasingly rare. We have also found six species present today that were not historically reported from Knight (1965). Maps showing current and historical stonefly diversity and distribution have been produced using ArcGIS and analyzed with relevant geographical data to form hypotheses to account for specific changes in the stonefly fauna of the basin.
NB33P-11 1330h
A Temporal Comparison of the Macroinvertebtate Community Structure of the Arima River, Trinidad, West Indies
In 1969 H.B.N. Hynes conducted a field study of invertebrates of the Arima River, Trinidad, West Indies. The 1971 paper that resulted was a landmark in developing concepts for longitudinal zonation in tropical streams. Thirty-four years later in 2003, 4 of Hynes' sample sites were re-sampled in an attempt to assess the impact of land use change over this period and current human activities on stream macroinvertebrate community structure. Hynes' 1969 data and those for 2003 were compared at a family level using MDS ordination and cluster analysis (PRIMER version 5). No significant dissimilarities were noted between sites for the respective years. This may be attributed to the fact that land use change within the Arima catchment has not been extensive enough to cause a dramatic shift in stream community composition. However, subtle changes in community structure may not be ascertained as discrimination at a family level may mask differences that would be clearer at a generic or species level.
NB33P-12 1330h
Aquatic Communities Of Temporary Streams Of The Guanacaste Conservation Area In Northwest Costa Rica
Santa Rosa National Park in northwestern Costa Rica is a seasonally dry region with little or no rain for 5-6 months of the year. Streams here are intermittent, with moderate or rapid flows for 2 months or less during the first downpours of the rainy season. Thereafter the streams become a connected series of pools during the remainder of the rainy season, with most pools disappearing during the dry months. The serpentine area of the Santa Elena peninsula is one of the driest habitats in Santa Rosa; nevertheless the temporary streams in this area have a diverse aquatic invertebrate community dominated by Ephemeroptera and Coleoptera. The mayfly genera Caenis (Caenidae), Ulmeritoides, Choroterpes, and Tikuna (Leptophlebiidae: Ephemeroptera) are abundant in these streams but the leptophlebiids are rare elsewhere in Costa Rica. Ulmeritoides appears to be a specialist in lentic microhabitats in lowland streams along both coasts of Costa Rica. Among tropical intermittent streams studied so far, the streams in Santa Elena have an unusually abundant and diverse Ephemeroptera fauna.
NB33P-13 1330h
The Effects of Photosynthesis on Extracellular Enzyme Activity in Periphyton Communities
In freshwater wetlands, a diverse assemblage of microorganisms (algae, bacteria, and fungi) grow on and within submerged dead plant material. Litter-associated bacteria and fungi produce a wide array of degradative enzymes that are important in decomposition of detritus. We investigated the potential for photosynthetically-mediated stimulation of heterotrophic extracellular enzyme activity. Microbial communities were grown on natural Typha litter in a local wetland. Samples were collected after 10 and 29 days of microbial colonization. In the laboratory, periphytic algal photosynthesis was manipulated by controlling light (0 or 400 Μmol m-2 s-1 PAR), while simultaneously quantifying the activities (Vmax) of litter associated β -xylosidase, β -glucosidase, leucine-aminopeptidase, and phosphotase using artificial fluorescent substrates. Activities of β -glucosidase (p=0.006) and phosphotase (p<0.001) were significantly greater in light-exposed communities, suggesting that attached algal photosynthesis stimulated enzyme activities. Thus, algal activity may potentially stimulate the litter decay activities of heterotrophic microbial assemblages in wetland ecosystems.
NB33P-14 1330h
Life History and Reproductive Timing of the Endangered Illinois Cave Amphipod, Gammarus acherondytes
To aid the recovery of endangered species requires an understanding of their basic biology. Armed with such knowledge, meaningful management plans with realistic objectives can be established. We examined the life history and reproductive biology of Gammarus acherondytes, a federally endangered cave amphipod, in Reverse Stream, Monroe Co., Illinois. The population was sampled non-destructively at monthly intervals from October 2003 to February 2005. The density of gravid females peaked twice annually, (November-December and June-July) indicating major reproductive events. Gravid females also occurred at other times of the year but at low densities. Two major peaks in the density of newborn young were also observed, which lagged the density of gravid females by approximately 1-2 months. We believe this reproductive pattern is related to the influx of organic matter from mid summer storm events and leaf abscission in autumn. Young grew at a rate of 0.034 mm/day and likely reach reproductive size in one year. Adults are iteroparous and may live for several years. Our results suggest that limiting cave access in highly visited caves during peak reproduction may be a simple strategy to increase the abundance of G. acherondytes.
NB33P-15 1330h
Freshwater Mussel (Family: Unionidae) Community Trends: A Commentary on the State of Great Plains Rivers?
The long-term health of a stream ecosystem may be judged by following the extended progress of a group of closely related species, such as unionid mussels. We compared current and historical distribution and abundance data for unionid mussels at 48 sites within six southeastern Kansas rivers. The current states of these communities were also correlated with instream environmental conditions (e.g., distribution with substrate size) and watershed condition, evaluated using a vegetation greenness index (NDVI) obtained from satellite imagery. Fusconaia flava (SINC) ranked in the top five in species abundance in each river, a very pleasant finding. Amblema plicata, the region's most abundant species, experienced severe declines in the Verdigris and Walnut Rivers. Between-year comparisons show 65-80% community similarity, except in the Walnut, which may have lost one-third to one-half of its species diversity in the last 25 years, while between-river comparisons show 35-65% similarity. Within and among species, mussels preferred medium-sized gravel (32-64 mm). Factors affecting the distribution and abundance of unionid mussels will be discussed along with a comparison of the current and historical states of the mussel populations. This evaluation is especially important in light of the recent invasion of Kansas by the zebra mussel, Dreissena polymorpha.
NB33P-16 1330h
Mollusk Survey in the Snake River, Hells Canyon, USA
We conducted surveys and several experiments on mollusks, focusing on listed, rare, or sensitive species, in reservoirs, tributaries and main stem of the Snake River in Hells Canyon Idaho and Oregon, USA. The most important result of this study was documentation of the undescribed Taylorconcha sp. throughout the Snake River in Hells Canyon, although we did not find Taylorconcha sp. within 12 miles downstream of HCD, most likely due to river armoring. Additional results include: 1) the mollusk community was similar throughout the Snake River, except where the Salmon River entered the Snake River; 2) Taylorconcha sp. abundance was directly related to the abundance of Potamopyrgus antipodarum, a highly invasive snail, and with moderate abundance of detritus; 3) hand picking cobbles was more efficient than suction dredging for snails and limpets but not for bivalves, 4) the most abundant mollusks were two invasive species, P. antipodarum and Corbicula fluminea and; 5) only one live small colony of native Gonidea angulata (Unionidae) and no live Anodonta californiensis (Unionidae) were found in the survey.
NB33P-17 1330h
Microsatellite Assessment of Gene Flow in Amblema plicata in the Ouachita Highlands of Southeastern Oklahoma
Appreciation of genetic diversity in unionids is essential to their preservation. Understanding how habitat perturbations, particularly those that fragment populations, affect this genetic diversity will provide information for better management of their natural habitats. We will examine genetic diversity and relatedness within a common mussel species, Amblema plicata, from three rivers in the Ouachita Highlands of southeastern Oklahoma that are fragmented to varying degrees. We sampled A. plicata tissue from ten sites each in the Little, Glover and MT. Fork Rivers. At each of ten sites per river, mussels were sampled from 15, randomly placed, 0.25m2 quadrats. Tissue samples consisting of 20-40 micrograms of mantle tissue were clipped from a minimum of 30 individuals per site. A subsample of mussel individuals was taken from each site for shell thin-sectioning to determine age. Microsatellite markers will be used to examine both genetic diversity and relatedness of A. plicata within and between sites. This will enable us to determine the impacts of impoundments on gene flow.
NB33P-18 1330h
Distribution of Unionid Mussels in Tributaries of the Lower Flint River, Southwestern Georgia: An Examination of Current and Historical Trends.
The historically diverse assemblage of freshwater mussels in the Flint River Basin has shown declines in abundance and distribution. The mid-reaches of the major tributaries of the Flint River contained one of the richest assemblages of mussels in the southeastern Coastal Plain. Declines in mussel assemblages accelerated following a recent severe drought (1999-2001). Following the drought, we surveyed mussel populations at selected sites in the major tributaries of the Flint River to determine whether declines in abundance and distribution are continuing. Many populations of common, rare, and endangered species were stable in their distribution (&35; taxa per site) but exhibited declines in abundance. One survey site in particular, on Spring Creek, contains a rich assemblage of mussels unique to the basin, and surveys from this site also suggest diminishing populations. Possible explanations for declines include poor water quality, loss or degradation of instream habitat, competition from the exotic Asiatic clam, and inadequate instream flows.
NB33P-19 1330h
Assessment and Habitat Evaluation of Native Freshwater Mussel Resources of Buffalo National River
The Buffalo National River, Arkansas, boundary includes a 132-mile river corridor from near the headwaters to the confluence with the White River. The objectives of this project are to survey the entire river corridor, search for endangered and extirpated mussels, and conduct a geomorphological study. To date ~30% of the river has been qualitatively and quantitatively surveyed. A total of 22 new mussel aggregates were located in 2004. A total of 8 quantitative aggregates of previously known aggregates also were sampled in 2004, with an average aggregate area of 205.25 m2 ranging from 60 to 420 m2. Quantitatively sampled mussel aggregates resulted in: a mean richness of 11.13, ranging from 5-13; a mean density of 8.81 individuals / m2, ranging from 4.96-17.4 individuals / m2; and a mean community numeric standing crop of 1797 mussels, with a range of 610-4287 mussels. Habitat data from the aggregates suggests that mussels are more associated with substrate than with depth or velocity. Aggregates tend to increase in diversity and richness within cobble and boulder substrates. General negative correlations are seen for gravel, with diversity being strongly negatively correlated. Mussel surveys and geomorphology studies will continue in the summer and fall of 2005.
http://www.nps.gov/buff