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1

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Assessing researcher impacts from a long-term sampling program of wetland communities in the Everglades National Park, Florida, U.S.A. (2004)

Wolski, Lawrence F. ; Trexler, Joel C. ; Nelson, Eric B. ; [et al.]

Oxford, UK : Blackwell Science Ltd

Freshwater biology 49 (2004), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: 1. Long-term monitoring requires repeated visits to a study site, greatly increasing the potential for cumulative visitation effects. For ecological studies in general, and for monitoring in particular, data must be evaluated for confounding artefacts from researcher presence. We compared aquatic communities at long-term sampling plots (nine sites, each with three plots, studied continuously from 6 to 22 years) in the Everglades National Park to previously unsampled reference plots adjacent to them to assess the effects of researcher visitation on the flora and fauna.2. We identified two criteria that are sensitive to local habitat heterogeneity for assessment of visitation impacts. First, the long-term plots must differ from adjacent reference plots by a magnitude that exceeded variation among plots separated by equal or greater distance (i.e. the difference is greater than expected by scaling of community change proportional with distance); and second, multiple reference plots must consistently differ in direction (e.g. greater abundance or less abundance) from adjacent long-term plots. We also tested for increased heterogeneity among samples from long-term plots compared with those not previously visited.3. We found no evidence of researcher effects on fish or macroinvertebrates, and only weak evidence for alteration of emergent plants and periphyton floating mats. Our failure to document visitor impacts may result from either low visitation rate or the dynamic nature of the wetlands studied.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-2427.2004.01256.x

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2

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Restoration of the Kissimmee River: A Conceptual Model of Past and Present Fish Communities and Its Consequences for Evaluating Restoration Success (1995)

Trexler, Joel C.

Oxford, UK : Blackwell Publishing Ltd

Restoration ecology 3 (1995), S. 0

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ISSN: 1526-100X

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Efforts to restore fish communities of the Kissimmee River will require carefully defined criteria for assessing success. A goal of regaining communities mirroring those in the historical river may not be an appropriate target because the ecological conditions of the river before channelization are poorly known. The Kissimmee River is in a biogeographic region historically low in fish diversity, and no comparable rivers in that region remain substantially unaltered by human activity to permit their use as reference sites indicative of conditions in the Kissimmee before channelization. I propose alternative criteria for assessing restoration success emphasizing expectations for ecosystem function in similar floodplain rivers. Assessing ecosystem function will be less simple than assessing criteria such as fish condition or density of selected species. But criteria based solely on fish-population characteristics cannot be justified quantitatively. Information integrated from several levels of biotic organization (individuals, populations, communities, and systems) should be drawn upon in making conclusions about restoration success. I develop a conceptual model to outline aspects of ecosystem function that could serve as a basis for evaluation of the restoration of fish communities of the Kissimmee River. The model focuses on the dynamics of the flux of floodplain-channel nutrients and the movement of larvae, juvenile, and adult fishes and macroinvertebrates. The present community may be dominated more by species tolerant of low-oxygen conditions, such as gar and bowfin, than the restored community will be. I propose that nest sites may be the limiting recruitment success of substrate spawning species in the channelized river and that these species, including sunfish and large-mouth bass, will increase in abundance after restoration. Also, species relying on floodplain habitats, including sun-fish species, darters, and some minnows, may also increase in frequency with restoration of floodplain-channel hydro-logical conditions and habitats. The observation that no species are known to have disappeared from the Kissimmee River, and its relatively simple community structure compared to rivers of comparable size elsewhere, are encouraging for prospects of successful restoration.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1526-100X.1995.tb00170.x

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3

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How can the functional response best be determined? (1989)

Trexler, Joel C. ; McCulloch, Charles E. ; Travis, Joseph

Springer

Oecologia 78 (1989), S. 571-571

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ISSN: 1432-1939

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00378751

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4

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How can the functional reponse best be determined? (1988)

Trexler, Joel C. ; McCulloch, Charles E. ; Travis, Joseph

Springer

Oecologia 76 (1988), S. 206-214

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ISSN: 1432-1939

Keywords: Curve fitting ; Density dependence ; Functional response ; Logit ; Predation

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary We evaluated three methods for the analysis of functional response data by asking whether a given method could discriminate among functional responses and whether it could accurately identify regions of positive density-dependent predation. We evaluated comparative curve fitting with foraging models, linear least-squares analysis using the angular transformation, and logit analysis. Using data from nature and simulations, we found that the analyses of predation rates with the angular transformation and logit analysis were best at consistently determining the “true” functional response, i.e. the model used to generate simulated data. These methods also produced the most accurate estimates of the “true” regions of density dependence. Of these two methods, functional response data best fulfill the assumptions of logit analysis. Angularly transformed predation rates only approximate the assumptions of linear leastsquares analysis for predation rates between 0.1 and 0.9. Lack-of-fit statistics can reveal inadequate fit of a model to a data set where simple regression statistics might erroneously suggest a good match.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00379954

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5

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Interactions among factors affecting growth, development and survival in experimental populations of Bufo terrestris (Anura: Bufonidae) (1986)

Travis, Joseph ; Trexler, Joel C.

Springer

Oecologia 69 (1986), S. 110-116

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ISSN: 1432-1939

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary We designed a series of field experiments to investigate the importance of interactions between biotic and abiotic factors on the survival and development of larval cohorts of Bufo terrestris. Five “blocks” in a large pond represented environments of varying physical harshness. In the more severe blocks, increased density inhibited growth rates, yet in the more benign blocks, increased density enhanced growth rate. Although different blocks produced very different levels of survival to metamorphosis and size at metamorphosis, there were no interactions with density. Increased density produced lengthened development times in the harsher blocks, but had no effect in the less stressful blocks. Hatchlings that were in the lowest of 3 initial size classes never caught up with their larger contemporaries and survived poorly. Hatchlings in the middle and largest size classes performed equivalently in all parameters of growth and development, but hatchlings from the middle size class were less likely to survive than their larger contemporaries. The effects of initial size did not interact with block. The inhibitory patterns displayed by density in conjunction with varying physical environments are similar to those found in comparable experiments with plants.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00399045

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6

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Environmental effects on adult growth patterns in the male sailfin molly, Poecilia latipinna (Poeciliidae) (1989)

Travis, Joseph ; Farr, James A. ; McManus, Michael ; [et al.]

Springer

Environmental biology of fishes 26 (1989), S. 119-127

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ISSN: 1573-5133

Keywords: Juvenile experience ; Phenotypic plasticity ; Fish

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Synopsis Widespread male body size variation in P. latipinna appears to be attributable to genetic variation in the size at maturation. The contribution of adult growth needs to be assessed because adult growth rates may vary with size at maturation and local environment. In our laboratory study we examined adult growth patterns as a function of size at maturation and juvenile experience (favorable or unfavorable conditions). In our field study we assessed adult growth as a function of initial size and environmental condition (using males in enclosures in contrasting habitats). Adult growth rates in the laboratory were an order of magnitude higher than rates observed in field enclosures. Growth rates varied with male size, increasing with increasing male size in the laboratory study but decreasing with increasing male size in the field study. The laboratory results alone would have cast considerable doubt on the ability to interpret size distributions of field-collected males, but the field results indicate that adult growth is sufficiently low that it can be ignored as a source of body size variation within and among populations.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00001028

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7

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Modeling fish dynamics and effects of stress in a hydrologically pulsed ecosystem (1997)

DeAngelis, Donald L. ; Loftus, William F. ; Trexler, Joel C. ; [et al.]

Springer

Journal of aquatic ecosystem stress and recovery 6 (1997), S. 1-13

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ISSN: 1573-5141

Keywords: wetlands ; fish population model ; seasonal cycles ; predator–prey relationships ; hydrology ; anthropogenic stresses

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Many wetlands undergo seasonal cycles in precipitation and water depth.This environmental seasonality is echoed in patterns of production of fishbiomass, which, in turn, influence the phenology of other components of thefood web, including wading birds. Human activities, such as drainage orother alterations of the hydrology, can exacerbate these natural cycles andresult in detrimental stresses on fish production and the higher trophic levels dependent on this production. In this paper we model theseasonal pattern of fish production in a freshwater marsh, with specialreference to the Everglades/Big Cypress region of southern Florida.The model illustrates the temporal pattern of production through theyear, which can result in very high densities of fish at the end of ahydroperiod (period of flooding), aswell as the importance of ponds and other deep depressions, both as refugia and sinks during dry periods. The model predicts that: (1) there is an effective threshold in the length of the hydroperiod that must beexceeded for high fish-population densities to be produced, (2) large,piscivorous fishes do not appear tohave a major impact on smaller fishes in the marsh habitat, and (3) therecovery of small-fish populations in the marsh following a major droughtmay require up to a year. The last of these results is relevant toassessing anthropogenic impacts on marsh production, as these effectsmay increase the severity and frequency of droughts.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1008228706210

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8

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Empirical Assessment of Fish Introductions in a Subtropical Wetland: An Evaluation of Contrasting Views (2000)

Trexler, Joel C. ; Loftus, William F. ; Jordan, Frank ; [et al.]

Springer

Biological invasions 2 (2000), S. 265-277

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ISSN: 1573-1464

Keywords: canals ; cichlids ; Everglades ; exotic fishes ; Florida ; introduced fishes ; invasion ; non-indigenous fishes ; wetlands

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract We summarized data from eight quantitative fish surveys conducted in southern Florida to evaluate the distribution and relative abundance of introduced fishes across a variety of habitats. These surveys encompassed marsh and canal habitats throughout most of the Everglades region, including the mangrove fringe of Florida Bay. Two studies provided systematically collected density information over a 20-year period, and documented the first local appearance of four introduced fishes based on their repeated absence in prior surveys. Those species displayed a pattern of rapid population growth followed by decline, then persistence at lower densities. Estuarine areas in the southern Everglades, characterized by natural tidal creeks surrounded by mangrove-dominated marshes, and canals held the largest introduced-fish populations. Introduced fishes were also common, at times exceeding 50% of the fish community, in solution holes that serve as dry-season refuges in short-hydroperiod rockland habitats of the eastern Everglades. Wet prairies and alligator ponds distant from canals generally held few individuals of introduced fishes. These patterns suggest that the introduced fishes in southern Florida at present may not be well-adapted to persist in freshwater marshes of the Everglades, possibly because of an interaction of periodic cold-temperature stress and hydrologic fluctuation. Our analyses indicated low densities of these fishes in central or northern Everglades wet-prairie communities, and, in the absence of experimental data, little evidence of biotic effects in this spatially extensive habitat. There is no guarantee that this condition will be maintained, especially under the cumulative effects of future invasions or environmental change.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1011488118444

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9

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Variation among populations of the sailfin molly in the rate of concurrent multiple paternity and its implications for mating-system evolution (1997)

Trexler, Joel C. ; Travis, Joseph ; Dinep, Andrea

Springer

Behavioral ecology and sociobiology 40 (1997), S. 297-305

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ISSN: 1432-0762

Keywords: Key wordsPoecilia latipinna ; Mating system ; Multiple paternity ; Fertility ; Allozymes

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract We examined patterns of concurrent multiple mating in a live-bearing poeciliid fish, the sailfin molly (Poecilia latipinna). We tested whether the probability of multiple paternity was related to female body size or fertility and whether the rate of multiple paternity varied among four populations that differed in their distributions of female body size and fertility. We analyzed data on mother and offspring genotypes for three polymorphic allozymes by three techniques, including a maximum-likelihood estimator that accounts for sampling error in both parental and offspring allele frequencies. The estimated rate of multiple paternity varied between 0.09 and 0.85, and the rate in one population varied seasonally between 0.33 (spring) and 0.85 (autumn). The variation in these rates was not associated with variation in body-size distributions among populations but was closely associated with variation in size-specific fertility: populations with greater variation in female fertility had higher multiple-paternity rates. Within two populations, logistic regression revealed that individual females of larger body size and greater size-specific fertility were more likely to carry multiply sired broods. This result is consistent with observations made in one of the populations 5 years earlier. In general, the results strongly suggest that the mating system varies markedly among conspecific populations of sailfin mollies and that larger, more fertile females are the objects of intermale competition.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002650050345

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