Least-s~uares lin:ar regression and multiple regression are among the most com~ only used anal.ytical te~hm.ques of ecologists. However, these techniques only address a portion of~he possible apphcatwns of regression methods. We discuss two less commonly used regressiOn a~alyses t?a~ could fi~d "':ide application in ecology, logistic regression and LO~ESS regr:sswn .. Logistic regression 1s appropriate in cases where the dependent variable IS categoncal, dichotomous, or polychotomous. It can be used with continuous and/ or di_screte independent variables. Logistic regression is motivated by the underlying binomial or multinomial distribution of dichotomous and polychotomous dependent variables a_nd transforms the dat.a to explicitly model these distributions. Locally weighted regressiOn scatterplot sm~othmg or _LOWESS regression is used to model the relationship b~tween a dependent vanable and mdependent variable when no single functional form will. do. LOWESS r:gression is motivated by the assumption that neighboring values of ~he mdependent vanable are the best indicators of the dependent variable in that range of mdependent values.

Oecologia (1988) 76:206 214 Two equations in our paper were inverted. These were the weights for empirical logistic regression reported on the bottom of page 212 and top of page 213. The corrected weight from the bottom of page 212 is:When Rj equals 0 or Nj the weight, incorrectly given on top of page 213, is:These changes have no effect on the results we report as these equations were not used in our analyses. We opted for the more accurate maximum likelihood solution to logistic regression, which we continue to advocate over the empirical logistic approach.

We used analytic and simulation models to determine the ecological conditions favoring evolution of a matrotrophic fish from a lecithotrophic ancestor given a complex set of trade-offs. Matrotrophy is the nourishment of viviparous embryos by resources provided between fertilization and parturition, while lecithotrophy describes embryo nourishment provided before fertilization. In fishes and reptiles, embryo nourishment encompasses a continuum from solely lecithotrophic to primarily matrotrophic. Matrotrophy has evolved independently from lecithotrophic ancestors many times in many groups. We assumed matrotrophy increased the number of offspring a viviparous female could gestate and evaluated conditions of food availability favoring lecithotrophy or matrotrophy. The matrotrophic strategy was superior when food resources exceeded demand during gestation but at a risk of overproduction and reproductive failure if food intake was limited. Matrotrophic females were leaner during gestation than lecithotrophic females, yielding shorter life spans. Our models suggest that matrotrophic embryo nourishment evolved in environments with high food availability, consistently exceeding energy requirements for maintaining relatively large broods. Embryo abortion with some resorption of invested energy is a necessary preadaptation to the evolution of matrotrophy. Future work should explore trade-offs of age-specific mortality and reproductive output for females maintaining different levels of fat storage during gestation.

We examined periphyton along transects in five Everglades marshes and related compositional and functional aspects to phosphorus (P) gradients caused by enriched inflows. Results were compared to those of a P-addition experiment in a pristine Everglades marsh. While the water total P (TP) concentration was not related to P load in the marshes or experiment, the concentration of TP in periphyton was strongly correlated with the distance from the P source. Increased P concentration in periphyton was associated with a loss of biomass, particularly of the calcifying mat-forming matrix, regardless of the growth form of the periphyton (epiphytic, floating, or epilithic). Diatom species composition was also strongly related to P availability, but the TP optima of many species varied among marshes. Enriched periphyton communities were found 14 km downstream of P inputs to one marsh that has been receiving enhanced P loads for decades, where other studies using different biotic indicators show negligible change in the same marsh. Although recovery trajectories are unknown, periphyton indicators should serve as excellent metrics for the progression or amelioration of P-related effects in the Everglades.Water column total phosphorus (TP) concentration has been shown to be a poor metric of eutrophication in P-limited shallow wetlands and ponds (Gaiser et al. 2004). In all but the most hypereutrophic settings, the majority of P is in the biota (Hudson et al. 2000), which, in shallow water, are mainly benthic rather than planktonic. However, water column measures are still used to assess P transport in wetlands

1.Drought is a natural disturbance that can cause widespread mortality of aquatic organisms in wetlands. We hypothesized that seasonal drying of marsh surfaces (i.e. hydrological disturbance) shapes spatio-temporal patterns of fish populations. 2. We tested whether population dynamics of fishes were synchronized by hydrological disturbance (Moran effect) or distance separating study sites (dispersal). Spatio-temporal patterns were examined in local populations of five abundant species at 17 sites (sampled five times per year from 1996 to 2001) in a large oligotrophic wetland. 3. Fish densities differed significantly across spatio-temporal scales for all species. For all species except eastern mosquitofish ( Gambusia holbrooki ), a significant portion of spatio-temporal variation in density was attributed to drying events (used as a covariate). 4. We observed three patterns of response to hydrological disturbance. Densities of bluefin killifish ( Lucania goodei ), least killifish ( Heterandria formosa ), and golden topminnow ( Fundulus chrysotus ) were usually lowest after a dry down and recovered slowly. Eastern mosquitofish showed no distinct response to marsh drying (i.e. they recovered quickly). Flagfish ( Jordanella floridae ) density was often highest after a dry down and then declined. Population growth after a dry down was often asymptotic for bluefin killifish and golden topminnow, with greatest asymptotic density and longest time to recovery at sites that dried infrequently. 5. Fish population dynamics were synchronized by hydrological disturbance (independent of distance) and distance separating study sites (independent of hydrological disturbance). Our ability to separate the relative importance of the Moran effect from dispersal was strengthened by a weak association between hydrological synchrony and distance among study sites. Dispersal was the primary mechanism for synchronous population dynamics of flagfish, whereas hydrological disturbance was the primary mechanism for synchronous population dynamics of the other species examined. 6. Species varied in the relative role of the Moran effect and dispersal in homogenizing their population dynamics, probably as a function of life history and ability to exploit dry-season refugia.

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Models of community regulation commonly incorporate gradients of disturbance inversely related to the role of biotic interactions in regulating intermediate trophic levels. Higher trophic-level organisms are predicted to be more strongly limited by intermediate levels of disturbance than are the organisms they consume. We used a manipulation of the frequency of hydrological disturbance in an intervention analysis to examine its effects on small-fish communities in the Everglades, USA. From 1978 to 2002, we monitored fishes at one long-hydroperiod (average 350 days) and at one short-hydroperiod (average 259 days; monitoring started here in 1985) site. At a third site, managers intervened in 1985 to diminish the frequency and duration of marsh drying. By the late 1990s, the successional dynamics of density and relative abundance at the intervention site converged on those of the long-hydroperiod site. Community change was manifested over 3 to 5 years following a dry-down if a site remained inundated; the number of days since the most recent drying event and length of the preceding dry period were useful for predicting population dynamics. Community dissimilarity was positively correlated with the time since last dry. Community dynamics resulted from change in the relative abundance of three groups of species linked by life-history responses to drought. Drought frequency and intensity covaried in response to hydrological manipulation at the landscape scale; community-level successional dynamics converged on a relatively small range of species compositions when drought return-time extended beyond 4 years. The density of small fishes increased with diminution of drought frequency, consistent with disturbance-limited community structure; less-frequent drying than experienced in this study (i.e., longer return times) yields predator-dominated regulation of small-fish communities in some parts of the Everglades.

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